Thèses sur le sujet « Landslides monitoring »

Every year, thousands of people all over the world are loosing their lives in natural disasters. As a second most widespread hazard, landslides are still a disaster problem for Turkey. The long-term monitoring studies of instability phenomena have a paramount importance for Turkey to reduce its both direct and indirect effects. The objective of this thesis is to monitor the activity of the Bü
lbü
lderesi and Bakacak landslides in Asarsuyu Catchment for 42 years period by the digital aerial photogrammetric techniques while evaluating the possible use of archive aerial photography in such analysis. To achieve the purpose of the study an orthophoto map was generated by aerial photographs belonging to 1994 year. The orthophoto map was utilized as a base map for aerial photo interpretation of different sets of aerial photographs corresponding to 1952, 1972, 1984 and 1994 years. As a result of this, 4 landslide activity maps are obtained. In addition, the characteristics of these landslides are analyzed by utilizing digital elevation model (DEM) created from stereo photographs of 1994. As a result of the study, no considerable variation is detected in the position of main boundaries of Bü
lbü
lderesi and Bakacak landslides except some minor differences. However, within the landslides many topographical changes were observed between 1952 and 1994 period. Based on the profiles from toe to crest of the Bü
lbü
lderesi landslide, the approximate length was measured as 4773m whereas the approximate width was about 2614m. The areal extent was calculated as ~12km2 having an approximate slope gradient ranging between 10-15°
with local variations. On the other hand, the approximate length of Bakacak landslide was 4420m and the approximate width was 832m from toe to crest with an area of ~4km2 and with an approximate slope angle 9-14°
.

2017 - 2018
Weather induced landslides cause a large number of casualties as well as severe economic losses worldwide every year. Such a diffuse risk cannot be mitigated only by means of structural works, typically characterized by significant economic and environment al impacts. Therefore, landslide early warning systems (LEWS) are being increasingly applied as non structural mitigation measures aiming at reducing the loss of life probability and other adverse consequences from landslide events by prompting people to a ct appropriately and in sufficient time to reduce the possibility of harm or loss. The systems can be distinguished, as a function of the scale of design and operation, in two different categories. Territorial systems (Te LEWS), deal with multiple landslid es over wide areas at regional scale, i.e. typically a basin, a municipality or a region; local systems (Lo LEWS) address single landslides at slope scale. In a preliminary phase of this study, a detailed review of Lo LEWS operational worldwide is provide d. The information has been retrieved from peer reviewed articles published in scientific journals and proceedings of technical conferences, books, reports, and institutional web pages. The main characteristics of these systems have been summarized and des cribed according to a scheme based on a clear distinction between three modules: landslide model, warning model and warning system. The monitoring strategies implemented therein have been presented and discussed, focusing on the monitored parameters and th e monitoring instruments for each type of landslide. Subsequently, warning models developed within Te LEWS for weather induced landslides have been analyzed , pointing out that: their outputs are strongly dependent from the accurateness and reliability of t he information on landslide occurrences; and only meteorological variables are considered in most of occurrences; and only meteorological variables are considered in most of the cases, thus leading to an unavoidable uncertainty in the empirically the cases, thus leading to an unavoidable uncertainty in the empirically defined thresholds. defined thresholds. To overcome these issues, original procedures for To overcome these issues, original procedures for defining wardefining warning models are herein proposed and tested on case studies ning models are herein proposed and tested on case studies in Campania and Emiliain Campania and Emilia--Romagna regions (Italy) and in Norway. In Italy, Romagna regions (Italy) and in Norway. In Italy, a probabilistic approach has been developed to determine landslide a probabilistic approach has been developed to determine landslide conditional probabilities related to rainfall of specific conditional probabilities related to rainfall of specific intensity and intensity and duration. The adopted Bayesian methodology allows to consider the duration. The adopted Bayesian methodology allows to consider the uncertainty of the data and to provide a quantitative assessment of the uncertainty of the data and to provide a quantitative assessment of the reliability of the results. Data on landslide occurrences have been derived reliability of the results. Data on landslide occurrences have been derived from a new landslide inventofrom a new landslide inventory, named “FraneItalia”, wherein data are ry, named “FraneItalia”, wherein data are retrieved from online journalistic news; the correlations between retrieved from online journalistic news; the correlations between landslides and rainfall have been assessed by analylandslides and rainfall have been assessed by analyzzing satelliteing satellite--rainfall rainfall records within weather alert zones. On the other hand, the methodology records within weather alert zones. On the other hand, the methodology prproposed for Norway aims at integrating the hydrooposed for Norway aims at integrating the hydro--meteorological meteorological variables employed within the regional model used by the national early variables employed within the regional model used by the national early warning system (i.e. combinations of relative water supply and relative soil warning system (i.e. combinations of relative water supply and relative soil water saturation degree) with monitoring datwater saturation degree) with monitoring data collected at local scale, a collected at local scale, specifically pore water pressure observations acquired by the Norwegian specifically pore water pressure observations acquired by the Norwegian Geotechnical Institute for a variety of projects. The analyses are carried Geotechnical Institute for a variety of projects. The analyses are carried out on a number of hydrological basins (test areas) defined at national out on a number of hydrological basins (test areas) defined at national scale andscale and selected considering the occurrence of landslides in loose soils selected considering the occurrence of landslides in loose soils from 2013 to 2017 and the availability of a significant number of pore from 2013 to 2017 and the availability of a significant number of pore water pressure measurements. For each basin, the alerts issued by the water pressure measurements. For each basin, the alerts issued by the regional model are assessed by means of a 2regional model are assessed by means of a 2--step step analysis employing analysis employing indicators derived from simple moving averages of the pore water indicators derived from simple moving averages of the pore water pressure measurements. pressure measurements. The warning models developed herein were successfully applied to The warning models developed herein were successfully applied to selected case studies. Therefore, the proposed methodologies can be selected case studies. Therefore, the proposed methodologies can be considered valuconsidered valuable frameworks considering aspects that are crucial for able frameworks considering aspects that are crucial for improving the efficiency of the models, such as: the potential of nonimproving the efficiency of the models, such as: the potential of non--conventional landslide inventories and remote sensing monitoring conventional landslide inventories and remote sensing monitoring instruments to complement the traditional sources of data, the uinstruments to complement the traditional sources of data, the use of se of probabilistic techniques for defining more objective rainfall thresholds, probabilistic techniques for defining more objective rainfall thresholds, and the additional contribution of the information derived from the local and the additional contribution of the information derived from the local observations of pore water pressures.observations of pore water pressures. [edited by Author]
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Landslides are one of the most destructive disasters that cause damage to both property and life every year. Various methodologies have been reported for landslide susceptibility mapping. Statistical methods are widely used to fit the mathematical relationship between observed landslides and the factors considered to influence the slope failure, and have shown remarkable accuracy. Among these models, frequency ratio and logistic regression models are the most popular for its simplicity and high accuracy. However, virtually all previous studies randomly extracted and reserved a portion of historical landslide records to perform the model evaluation. The purpose of this study are: 1) To produce a landslide susceptibility map for Lantau Island by GIS and remote sensing methods as well as statistical modeling techniques 2) To add extra value to the literature of evaluating their “prediction rate” (rather than “success rate”) for landslide susceptibility mapping in a temporal context. The mountainous terrain, heavy and prolonged rainfall, as well as dense development near steep hillsides make Hong Kong as one of the most vulnerable metropolitans to the risk of landslides. As there is an increasingly high demand for land resource to support the growth of economic and population, regional specific landslide susceptibility assessment in Hong Kong is necessary for hazard management and effective land use planning. Firstly, the spatial relationship among landslide occurrence and nine causative factors (elevation, slope aspect, slope gradient, plan curvature, profile curvature, NDVI, distance to river, SPI and lithology) were explored. The distribution of landslides on Lantau Island is largely governed by a combination of geo-environmental conditions, such as elevation of 200m-300m, slope gradient of 25°-35°, slope aspect of west or northwest, high degree of positive or negative plan curvature and profile curvature, sparse vegetation in terms of NDVI in 0.3-0.5 (shrub/grassland), proximity (0.6-1.2km) to fault line, presence of volcanic bedrocks (especially rhyolite lava and tuff) and high stream power index. Second, landslide susceptibility maps were generated by frequency ratio and logistic regression model, respectively. Validations of the mapping results were performed by calculating relative operating characteristics (ROC). The models, trained by 1,864 (70%) landslides records in the Enhanced Natural Terrain Landslide Inventory (ENTLI) from 2000 to 2008, were validated by subsequent 799 (30%) landslide occurred from 2008 to 2009. The validation result shows that logistic regression model (88.70%) possesses a better prediction power than frequency ratio model (78.00%) for the study area. The findings suggested that logistic regression analysis is more reliable for landslide susceptibility mapping. The resultant maps are expected to provide a scientific assessment of the risk areas with respect to landslides on Lantau Island, and to serve as a basis for decisions or justification of the Lantau development planning. Keywords: landslide susceptibility; frequency ratio; logistic regression; temporal verification; GIS; Hong Kong

Landslide failures are a worldwide problem claiming human lives and causing catastrophic damages to infrastructure, with their impact able to reach that of war conflicts. For these reasons this thesis is going to investigate on the use of microseismic monitoring to study the kinematic behaviour of landslides and help towards the design of an optimised early or real time warning system. All findings are based in field experiments, using 1D and 3D short period seismometers, designed to understand the capabilities and limitations of microseismic monitoring in order to enhance the first and minimize the last. The first goal of this thesis is to understand accuracy of microseismic monitoring in locating weak seismic events. The effect of the seismic velocity model is studied against common seismological assumptions, while different aperture sizes of microseismic arrays are put into test for achieving optimum location results. Next, in order to allow the study of the expected landslide seismicity during a future landslide failure, a novel methodology, an up-scaled shear box, is designed to induce landslide like seismic signals. The proposed methodology can recreate soil slip events allowing control over different geotechnical conditions, such as stress levels, thus reproducing different landslide failure scenarios. The up-scaled shear box methodology is then used to test a novel engineered seismic source: glass shard piles placed inside the landslide's mass, triggered from the landslide's displacements. The material characteristics of glass shards don't change in time, e.g. due to saturation, and have a stable seismic signature during displacement. For these reasons glass shard piles can act as the common seismic source, overcoming the time consuming process of identifying landslide complex failure mechanisms. Finally, failure is induced to two landslide vertical faces under controlled conditions. Both landslides have identical characteristics, e.g. size and geology, with the only difference that in one of them a glass shard pile was incorporated. Visual observations, displacement and loading observations of the landslide faces, timed with a GPS clock, allowing for their detection on the seismic recordings and the characterisation of failure events. The collected data are found to correlate well with the experiments conducted with the up-scaled shear box methodology, allowing for their validation.

Early warning of slope instability will enable evacuation of vulnerable people and timely repair and maintenance of critical infrastructure. However, currently available warning systems are too expensive for wide-scale use or have technical limitations. The acoustic emission (AE) monitoring approach using active waveguides (i.e. a steel tube with granular backfill surround installed in a borehole through a slope), in conjunction with the Slope ALARMS AE measurement system, has the potential to be an affordable early warning system for slope instability. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from measured AE. The development of an approach to quantify slope deformation behaviour from measured AE will enable the AE monitoring system to provide early warning of slope instability through detecting, quantifying and communicating accelerations in slope movement. Field monitoring and full-scale physical modelling have been conducted to characterise the AE response from the system to both reactivated slope movements and first-time slope failure. Definitive field evidence has been obtained showing AE monitoring can measure slope movements and generated AE rates are proportional to slope displacement rates, which was confirmed through comparisons with both conventional inclinometer and continuous ShapeAccelArray deformation measurements. A field monitoring case study demonstrated that the AE approach can detect very slow slope movements of 0.075 mm/day. In addition, the concept of retrofitting inclinometer casings with active waveguides to convert the manually read instrument to a real-time monitoring system has been demonstrated using a field trial. Dynamic strain-controlled shear tests on active waveguide physical models demonstrated that AE monitoring can be used to quantify slope displacement rates, continuously and in real-time, with accuracy to within an order of magnitude. Large-scale first-time slope failure experiments allowed the AE response to slope failure to be characterised. AE was detected after shear deformations of less than a millimetre in previously un-sheared material, and AE rates increased proportionally with displacement rates as failure occurred. The AE rate-displacement rate relationship can be approximated as linear up to 100 mm/hour and shear surface deformations less than 10-20 mm. At greater velocities and larger deformations the gradient of the relationship progressively increases and is best represented using a polynomial. This is because complex pressure distributions develop along the active waveguide analogous to a laterally loaded pile, and the confining pressures increase. Variables that influence the AE rate-displacement rate relationship have been quantified using physical model experiments and empirical relationships. A framework has been developed to allow AE rate-displacement rate calibration relationships to be determined for any AE system installation. This provides a universal method that can be used by practitioners when installing AE systems, to calibrate them to deliver alarm statuses/warning levels that are related to slope displacement rates. Use of this framework has been demonstrated using a case study example, and decision making protocols have been suggested that use trends in alarms with time to trigger decisions, which could be to send an engineer to inspect the slope, manage traffic, or evacuate people.

Landslide characterization and hazard assessments require multidisciplinary approaches that connect geologic processes with geotechnical parameters. Field monitoring of hydrologic variables such as water content and water potential, coupled with geoelectrical measurements that can establish relationships used for geotechnical and landslide hazard investigations is deficient. This study brings together different techniques to develop a methodology that connects geoelectrical measurements and shear strength. A field-based framework was established that includes (1) analysis of long-term soil moisture fluctuations within different landslides (2) establishment of constitutive and new equations that test the use of electrical conductivity to predict soil-water relationships and shear strength (3) using electrical resistivity tomography (ERT) to support and facilitate the prediction of shear strength in a slope. Hydrologic conditions including volumetric water content, water potential, and electrical conductivity in the soil were measured at three active landslides in Kentucky. The in-situ electrical conductivity used within the framework is valid as a predictor of suction stress and shear strength. The ERT supports interpretations of landslide failure zones, landslide type, lithologic boundaries, and changes in moisture conditions, but also is able to utilize the methodology to calculate shear strength, and provide a spatial view of shear strength in the slope. The practical application of this framework is to support landslide hazard assessment and further understand the long-term influence of moisture conditions in hillslope soils. These parameters are pertinent to investigating the stability of landslides that are often triggered or reactivated by rainfall.

Hundreds of thousands of landslides occur every year around the world impacting on people's lives. Monitoring techniques able to foresee imminent collapse and provide a warning in time useful for action to be taken are essential for risk reduction and disaster prevention. Acoustic emission (AE) is generated in soil and rock materials by rearrangement of particles during displacement or increasing damage in the microstructure preceding a collapse; therefore AE is appropriate for estimation of slope deformation. To overcome the high attenuation that characterise geological materials and thus to be able to monitor AE activity, a system called Slope ALARMS that makes use of a waveguide to transmit AE waves from a deforming zone to a piezoelectric transducer was developed. The system quantifies acoustic activity as Ring Down Count (RDC) rates. In soil applications RDC rates have been correlated with the rate of deformation, however, the application to rock slopes poses new challenges over the significance of the measured AE trends, requiring new interpretation strategies. In order to develop new approaches to interpret acoustic emission rates measured within rock slopes, the system was installed at two trial sites in Italy and Austria. RDC rates from these sites, which have been measured over 6 and 2.5 years respectively, are analysed and clear and recurring trends were identified. The comparison of AE trends with response from a series of traditional instruments available at the sites allowed correlation with changes in external slope loading and internal stress changes. AE signatures from the limestone slope at the Italian site have been identified as generated in response to variations in the groundwater level and snow loading. At the conglomerate slope in Austria, AE signatures include the detachment of small boulders from the slope surface caused by the succession of freeze-thaw cycles during winter time. Consideration was also given to laboratory testing of specific system elements and field experiments. A framework towards strategies to interpret measured acoustic emission trends is provided for the use of the system within rock slopes.

This project was a step forward in developing a reliable, economical and accurate real-time warning system for rainfall-induced individual landslides based on physical-based, optimised slope monitoring and statistical and numerical approaches. The physical-based system involved experimental and numerical analyses in implementing a low-cost slope monitoring system in critical slopes in North Maleny, evaluating parameters of tilt angle (and tilt rate), the volumetric water content of soil and rainfall. The thesis further investigated auxiliary landslide prediction approaches, including rainfall intensity–duration thresholds and analytical time to failure predictions to enhance the accuracy and reliability of outcomes.

The Little North Santiam River Basin is a 111-square mile watershed located in the Cascade Range of western Oregon. The Little North Santiam River is a major tributary to the North Santiam River, which is the primary source of drinking water for Salem, Oregon and surrounding communities. Consequently, water quality conditions in the Little North Santiam River, such as high turbidity, affect treatment and delivery of the drinking water. Between 2001 and 2008, suspended-sediment loads from the Little North Santiam River accounted for 69% of the total suspended-sediment load that passed the treatment plant. Recent studies suggest that much of this sediment originates from landslide activity in the basin. Using airborne Light Detection and Ranging (LiDAR)-derived imagery, 401 landslides were mapped in the Little North Santiam River Basin. Landslide types vary by location, with deep-seated earth flows and earth slumps common in the lower half of the basin and channelized debris flows prominent in the upper basin. Over 37% of the lower basin shows evidence of landslide activity compared to just 4% of the upper basin. Instream turbidity monitoring and suspended-sediment load estimates during the winter of 2009-2010 demonstrate a similar distribution of sediment transport in the basin. During a 3-month study period, from December 2009 through February 2010, the lower basin supplied 2,990 tons, or 91% of the suspended-sediment load to the Little North Santiam River, whereas the upper basin supplied only 310 tons of sediment. One small 23-acre earth flow in the lower basin, the Evans Creek Landslide, supplied 28% of the total suspended-sediment load, even though it only comprises 0.0004% of the basin. The Evans Creek Landslide is an active earth flow that has been moving episodically since at least 1945, with surges occurring between 1945 and 1955, 1970 and 1977, in February 1996, and in January 2004. Recent erosion of the landslide toe by Evans Creek continues to destabilize the slope, supplying much of the sediment measured in the Little North Santiam River. Over the last 64 years, the average landslide movement rate has been between 5 and 12 feet per year.

Les processus gravitaires dans l’évolution de la morphologie des reliefs se produisent à de nombreuses échelles de temps et d’espace. Leur compréhension, fondamentale pour envisager la gestion des risques associés à ces phénomènes destructeurs, est subtile et complexe. En effet, les caractéristiques intrinsèques aux versants étudiés sont spécifiques et les facteurs externes agissant sur la dynamique de la déstabilisation présentent des temporalités et des intensités très variées. Afin de comprendre comment ces forçages influencent le comportement des instabilités de versant, une approche systémique a été adoptée dans ce travail pour mettre en perspective l’ensemble des processus en jeu dans l’évolution temporelle de leurs comportements. A travers deux cas d’étude situés dans les Alpes Maritimes (La Clapière à Saint-Etienne-de-Tinée et le Prat de Julian à Vence), véritables observatoires naturels disposant de plusieurs années de suivi multi-paramètres, la faculté de l’observation instrumentale à déterminer des paramètres comportementaux clés contrôlant l’évolution dynamique des versants instables a été explicitée. Des analyses multivariées intégrant l’état de surface (déplacements, déformations, perturbations) et interne (niveau piézométrique, résistivité électrique de la subsurface) ont permis de quantifier les liens entre l’état comportemental du versant étudié et les contributions météorologiques. Ce travail met finalement en avant l’importance des études observationnelles multi-paramètres dans l’élaboration des modèles descriptifs et prédictifs, ainsi que les systèmes d’alerte associés à ces risques majeurs
Gravity processes occur at many scales of time and space in the evolution of landforms’ morphology. Their understanding is subtle and complex and it is fundamental to consider the management of the risks associated with these destructive phenomena. Indeed, the intrinsic characteristics of the studied slopes are specific and the external factors acting on the dynamics of the destabilization present a wide range of temporalities and intensities. In order to understand how these forcings influence the behavior of slope instabilities, a systemic approach has been adopted in this work to put into perspective all the processes involved in the temporal evolution of their behaviors. Through two study cases located in the Alpes Maritimes (La Clapière at Saint-Etienne-de-Tinée and the Prat de Julian at Vence, France), real natural observatories with several years of multi-parameter monitoring, we were able to clarify the ability of instrumental observation to determine key behavioral parameters controlling the dynamic evolution of unstable slopes. Multivariate analyzes integrating the surface (displacements, deformations, disturbances) and internal state (groundwater level, electrical resistivity of the subsurface) allowed to quantify the links between the behavioral state of the studied slope and the meteorological contributions. This work finally highlights the importance of multi-parameter observational studies in the development of descriptive and predictive models, as well as the alert systems associated with these major risks

This thesis describes research efforts toward the development of a wireless sensor node, which can be employed in durable and expandable wireless sensor networks for remote monitoring of soil conditions in areas conducive to slope stability failures. Commercially available soil moisture probes and soil tilt sensors were combined with low-power, wireless data transmitters to form a self-configuring network of soil monitoring sensors. The remote locations of many slope stability hazard sites eliminates the possibility of real-time, remote monitoring instrumentation that relies on AC power or land-based communication methods for operation and data transfer. Therefore, various power supply solutions and data transfer methods were explored during this research and are described herein. Additionally, sensor modification and calibrations are discussed. Preliminary evaluations of field durability of the pilot instrumentation were undertaken during this research. Geotechnical engineering instrumentation must be able to withstand extreme weather related conditions. The wireless, solar-powered soil moisture and tilt sensor node was installed on the Texas A&M University campus, allowing evaluation of system reliability and instrument durability. Lastly, potential future research and conclusions arising from this research are presented. This research has shown that commercially available wireless instrumentation can be modified for use in geotechnical applications. The development of an active power management system allows for sensors to be placed in remote locations and operated indefinitely, thus creating another option for monitoring applications in geotechnical and environmental problems.

Active natural processes, such as landslides, that can induce damages and casualties, recurrently affect mountainous areas. In order to reduce the risks, the careful assessment and monitoring of landslides is highly needed. Interferometric Synthetic Aperture Radar (InSAR) is a powerful tool that can extract useful information to monitor natural hazards. Over the past two decades, several studies have demonstrated the potential of synthetic aperture radar interferometry for detecting and quantifying land surface deformation. Despite the advantages of InSAR methods for quantifying landslide deformation, some limitations remain. The temporal and spatial decorrelation, the presence of atmospheric artifacts, the 1-D Line Of Sight (LOS) observation restriction, the possible high velocity rate and the multi-directional movement properties make it difficult to monitor accurately complex landslides in areas covered by vegetation. Therefore, complementary and integrated approaches, such as offset tracking-based techniques, and sophisticated atmospheric artifacts estimation are needed to overcome these limitations for monitoring ground surface deformations. These critical issues are particularly challenging in mountain environments, due to the SAR properties, the stronger spatial variations of the local atmospheric conditions and the scattering characteristics of the ground surface, leading to spatial and temporal decorrelation of the SAR signal. Hence, the performance evaluation of the offset tracking and atmospheric corrections techniques is important in order to assess their potentials, robustness and limitations. In this thesis, we aim at improving estimation accuracy of offset tracking and InSAR atmospheric phase delay estimation. To this end, the Corvara landslide, located in the Alpine region of South Tyrol, is used as a pilot site to implement and test the offset tracking and atmospheric correction techniques. This area is monitored with GPS periodic campaigns and permanent stations and over there a set of corner reflectors have been installed.

Landslides represent major natural phenomena with often disastrous consequences. Monitoring landslides with time-series surface observations can help mitigate such hazards. Unmanned aerial vehicles (UAVs) employing compact digital cameras, and in conjunction with Structure-from-Motion (SfM) and modern Multi-View Stereo (MVS) image matching approaches, have become commonplace in the geoscience research community. These methods offer a relatively low-cost and flexible solution for many geomorphological applications. The SfM-MVS pipeline has expedited the generation of digital elevation models at high spatio-temporal resolution. Conventionally ground control points (GCPs) are required for co-registration. This task is often expensive and impracticable considering hazardous terrain. This research has developed a strategy for processing UAV visible wavelength imagery that can provide multi-temporal surface morphological information for landslide monitoring, in an attempt to overcome the reliance on GCPs. This morphological-based strategy applies the attribute of curvature in combination with the scale-invariant feature transform algorithm, to generate pseudo GCPs. Openness is applied to extract relatively stable regions whereby pseudo GCPs are selected. Image cross-correlation functions integrated with openness and slope are employed to track landslide motion with subsequent elevation differences and planimetric surface displacements produced. Accuracy assessment evaluates unresolved biases with the aid of benchmark datasets. This approach was tested in the UK, in two sites, first in Sandford with artificial surface change and then in an active landslide at Hollin Hill. In Sandford, the strategy detected a ±0.120 m 3D surface change from three-epoch SfM-MVS products derived from a consumer-grade UAV. For the Hollin Hill landslide six-epoch datasets spanning an eighteen-month duration period were used, providing a ± 0.221 m minimum change. Annual displacement rates of dm-level were estimated with optimal results over winter periods. Levels of accuracy and spatial resolution comparable to previous studies demonstrated the potential of the morphology-based strategy for a time-efficient and cost-effective monitoring at inaccessible areas.

If the effects of landslides are to be mitigated and avoided then the causes of landslide activations – and re-activations – must be better understood. The most common subsurface property change in the lead up to rainfall-triggered landslide activation is the moisture content of slope material and associated pore water pressure rises and/or consistency changes. Landslide early warning systems have been developed which observe and monitor characteristic slope properties in advance of activation and give advanced warning of imminent slope displacement. This PhD thesis analyses and presents the results of a four and a half year monitoring campaign of a periodically active inland landslide by – among other methods – a geoelectrical monitoring system called Automated time-Lapse Electrical Resistivity Tomography (ALERT). The ALERT system was trialled on a landslide system located within the Early Lias of North Yorkshire and the suitability of the system for landslide monitoring assessed. The products of the geophysical monitoring campaign range from discrete resistance measurements on the landslide to a four-dimensional, high-temporal resolution dataset which is interpreted in terms of hydrogeological processes. Temperature corrected resistance results of the geoelectrical monitoring system reveal that the system responds very well to rises and falls in piezometric levels and seasonal trends of soil desiccation during warmer, drier months and crack annealing and slope soil moisture accumulation in response to wetter periods. The existence of threshold slope moisture contents, and hence electrical resistances/resistivities, above which the slope activates are not observed in resistance/resistivity results most probably due to the complex nature of the landslide system, the system resolution and a number of physical slope processes taking place. However, trends in precursory soil moisture dynamics during the period leading up to earthflow activation are apparent in temperature corrected resistance results. Time-lapse model resistivity was converted to gravimetric moisture content through laboratory calibration of soil electro-petrophysical properties of each active lithological formation. Seasonal moisture content trends confirm system sensitivity to slope moisture content. However, lower moisture contents than were observed in the field indicate the need for higher resolution, intra-landslide ERT data to make the hydrogeology of landslides more apparent.

La cartographie, l'inventaire et le suivi de glissements de terrain sont indispensables pour l'évaluation de l'aléa glissements de terrain et la gestion des catastrophes. La disponibilité croissante des satellites THR, des drones et des appareils photo numériques grand public offre un grand potentiel pour soutenir ces tâches à l'échelle régionale et locale en complément detechniques établies telles que l'instrumentation in-situ, radar, et les acquisitions par scanner laser. Un manque d'outils de traitement d'image pour l’extraction efficace d’informations pertinentes à partir de différents types d'imagerie optique complique encore l'exploitation des données optiques et entrave la mise en oeuvre de services opérationnels. Cette thèse est consacrée à l'élaboration et l'application de techniques de traitement d'image pour la cartographie, la caractérisation et la surveillance des glissements de terrain en exploitant des données d'imagerie optique. Un état de l'art approfondi des techniques de télédétection innovantes pour la surveillance des glissements de terrain est proposé et démontre le potentiel et les limites des techniques et propose des critères pour le choix des capteurs disponibles (plateformes et méthodes d'analyse d'images) selon le processus observé et les besoins des utilisateurs. Pour la cartographie rapide des glissements de terrain lors de catastrophes majeures, une méthode qui combine segmentation d'image et apprentissage supervisé est développée pour l'analyse des images satellitaires THR à travers plusieurs exemples en Chine, au Brésil, à Haïti, en Italie et en France. Pour l'analyse de glissements de terrain à l'échelle locale, la recherche a élaboré des chaînes de traitement d'images pour la détection de fissures à partir de séries temporelles d'images de drones comme possible géo-indicateurs de l'activité des glissements, la mesure des champs de déplacements horizontaux à partir d'images satellitaires THR utilisant en utilisant des méthodes stéréophotogrammétrie et par corrélation d’image, et les mesures 3D à partir de photographies terrestres basées sur des méthodes de photogrammétrie multi-images
Landslide inventory mapping and monitoring are indispensable for hazard assessment and disaster management. The enhanced availability of VHR satellites, UAVs and consumer grade digital cameras offers a great potential to support those tasks at regional and local scales, and to complement established techniques such as in situ instrumentation, radar, andlaser scanning. A lack of image processing tools for the efficient extraction process-relevant information from different types of optical imagery still complicates the exploitation of optical data and hinders the implementation of operational services. This doctoral thesis is dedicated to the development and application of image processing techniques for the mapping,characterization and monitoring of landslides with optical remote sensing data. A comprehensive review of innovative remote sensing techniques for landslide monitoring shows the potential and limitations of available techniques and guides the selection of the most appropriate combination of sensors – platforms – image analysis methods according to the observed process and end-user needs. For the efficient detection of landslides after major triggering events at the regional scale, a method for rapid mapping combining image segmentation, feature extraction, supervised learning is developed. For detailed landslide investigations at the local scale, this study elaborates image processing chains for detection of surface fissures in time-series of UAV images as geo-indicators of landslide activity, the measurement of horizontal surface displacements from VHR satellite images using stereo-photogrammetric and image correlation methods, and 3D measurements from terrestrial photographs based on multi-view open-source photogrammetry

Every year, with the onset of spring rains and snow melting, landslides represent one of the major threats to human life and infrastructures in natural environments. In this context, different surveying techniques, such as inclinometers, extensometers, piezometers or Global Positioning System (GPS) networks, are typically employed to address landslide monitoring problem. Nonetheless, these conventional techniques present several limitations. They are labor, expensive and usually require skillful users to data interpretation. Moreover, they typically provide poor spatial sampling and coverage, which hinder the characterization of complex landslides. Finally, these techniques require the direct installation of devices over the landslide surface, which could be a complex task, sometimes impossible to fulfill, in hard-to-reach locations. During the last decade, Synthetic Aperture Radar (SAR) Interferometry (InSAR) techniques based on space-borne SAR sensors have matured to a widely used geodetic tool for the precise monitoring of complex displacement phenomena with millimetric accuracy. Concretely, the new family of X-band SAR sensors, like the German TerraSAR-X and TanDEM-X satellites or the Italian constellation Cosmo-Skymed, have led to a scientific breakthrough presenting a lower revisiting time (up to few days) and an improved spatial resolution (up to the meter), compared with their predecessors ERS-1/2, ENVISAT-ASAR or RADARSAT-1, which worked at C-band. The industry, research laboratories, and universities are developing flexible tools for displacement monitoring analysis by means of space-borne InSAR techniques, which are being adapted for its fully operational use and for its integration with conventional observations and predictive models. Contrarily, when a high flexibility in terms of revisiting-time is required, or the need to fit the sensor orientation to the specific characteristics of the area under study exists, the research activity of several groups has been addressed to the development of Ground-Based SAR (GB-SAR) sensors. Easy to deploy, and cheaper if compared with space-borne solutions, GB-SAR sensors are a potential alternative, ideal for the monitoring of small-scale areas. The high stability of the sensor platform, and its flexibility in terms of revisiting time, make these systems an excellent option to detect displacements with a high temporal resolution of up to few minutes. Despite all these clear advantages, SAR sensors based on both space-borne and ground-based platforms also present some limitations, especially, over vegetated scenarios in mountainous environments, where landslides typically occur. Whereas its performance over bare surfaces or rocky areas is satisfactory during snow-free seasons, severe limitations arise from temporal decorrelation over vegetated areas, due to layover and shadowing effects caused by SAR geometrical distortions, the presence of tropospheric atmospheric artifacts or when rapid displacements are faced. Finally, it must be taken into account that SAR sensors are only sensitive to the satellite-to-target component of displacement, which may notably differ from the real one. There is still some way to go in order to overcome all these limitations and convert InSAR techniques into fully operational tools, context in which this PhD Thesis has been developed. The main objective of this PhD Thesis is the development of advanced InSAR techniques for the monitoring of areas affected by landslides. Concretely, the performance of both space-borne and ground-based SAR sensors will be compared and evaluated in the area of El Forn de Canillo, Andorra, which corresponds to one of the biggest landslides of the Pyrenees. The techniques presented in this PhD Thesis provide evidences for informed decision making, supported by the science, in order to ease the management of the geo-hazard risk associated with active landslides.
Cada año, con la llegada de la época de lluvia y el deshielo en primavera, los deslizamientos de laderas representan una gran amenaza para la vida humana y para un gran número de infraestructuras en entornos naturales. Para abordar esta problemática, tradicionalmente se utilizan técnicas de auscultación que incluyen extensómetros, inclinómetros, piezómetros o redes de Sistemas de Posicionamiento Global (GPS). A pesar de que su uso está muy extendido, estas técnicas presentan un gran número de limitaciones. Por una parte, requieren sensores generalmente caros y complejos, cuya eficiencia está sujeta a la disponibilidad de usuarios expertos para su posterior interpretación. Además, estas técnicas típicamente presentan bajas prestaciones en términos de muestreo espacial y cobertura, dificultando de este modo la caracterización de deslizamientos complejos. Finalmente, requieren la instalación de dispositivos directamente sobre la superficie de deslizamiento, lo cual puede resultar una tarea compleja en zonas de difícil acceso. Durante esta última década, el uso de imágenes de satélite de Radar de Apertura Sintética (SAR) y concretamente el uso de su más notable aplicación, conocida como Interferometría SAR (InSAR), ha experimentado un gran impulso, haciendo posible la observación de estos fenómenos de desplazamiento con precisiones milimétricas. Estos avances están permitiendo el desarrollo de herramientas flexibles por parte de la industria, laboratorios de investigación y universidades, para el estudio de desplazamientos del terreno mediante técnicas InSAR, las cuales están siendo adaptadas para su operatividad e integración con observaciones convencionales y modelos predictivos. Por otra parte, cuando se requiere de una alta flexibilidad en términos de tiempo de revisita, o existe la necesidad de adaptar la orientación del sensor a las características específicas de la zona bajo estudio, la actividad de investigación de un gran número de grupos se ha centrado en el desarrollo de sensores SAR terrestres. Fáciles de implementar y de un menor coste en comparación con soluciones orbitales, estos sensores representan una alternativa muy interesante para la monitorización de zonas localizadas. A pesar de todas estas ventajas, tanto los sensores SAR embarcados en plataformas orbitales como los terrestres presentan distintas limitaciones, especialmente, en áreas montañosas altamente vegetadas donde normalmente se producen los deslizamientos de laderas. Mientras que su rendimiento sobre áreas rocosas es muy satisfactorio en ausencia de nieve, pueden aparecer diferentes limitaciones debido a efectos de decorrelación temporal sobre zonas con vegetación, a distorsiones en la imagen causadas por la geometría de adquisición, a la presencia de artefactos atmosféricos severos en zonas con topografía abrupta o cuando se intentan analizar desplazamientos de carácter rápido. Finalmente, debe tenerse en cuenta que los sensores SAR sólo son sensibles a la componente de desplazamiento en la línea de visión del satélite y por ello, ésta, puede diferir notablemente de la real. Aún queda por tanto un cierto camino por recorrer para superar todas estas limitaciones y convertir a las técnicas InSAR en herramientas totalmente operativas, contexto en el que esta Tesis Doctoral se ha desarrollado. El principal objetivo de esta Tesis Doctoral es el desarrollo de técnicas InSAR para la monitorización de zonas afectadas por deslizamientos de laderas. En concreto, el rendimiento de éstas técnicas para ambas plataformas, orbital y terrestre, se ha comparado y evaluado exhaustivamente en el deslizamiento de El Forn de Canillo, Andorra, que está considerado como con uno de los mayores deslizamientos de ladera de los Pirineos. Las técnicas presentadas en esta Tesis Doctoral proporcionan evidencias para la toma de decisión, apoyadas por la ciencia, con el fin de facilitar la gestión de los riesgos asociados con los deslizamientos de laderas inestables.
Cada any, amb l'arribada de l'època de pluges i desglaç a la primavera, les esllavissades representen una gran amenaça per a la vida humana i per a un gran nombre d'infraestructures en entorns naturals. Per abordar aquesta problemàtica, tradicionalment s'utilitzen tècniques d'auscultació que inclouen extensòmetres, inclinòmetres, piezòmetres o xarxes de Sistemes de Posicionament Global (GPS). Tot i que el seu ús està molt estès, aquestes tècniques presenten un gran nombre de limitacions. D'una banda, requereixen de sensors generalment cars i complexes, on la seva eficiència està subjecta a la disponibilitat d'usuaris experts per a la seva posterior interpretació. A més, aquestes tècniques típicament presenten baixes prestacions en termes de mostreig espacial i cobertura, dificultant d'aquesta manera la caracterització d'esllavissades complexes. Finalment, requereixen de la instal·lació de dispositius directament sobre la superfície de l'esllavissada, la qual cosa pot resultar una tasca complicada en zones de difícil accés.Durant aquesta última dècada, l'ús d'imatges de satèl·lit de Radar d'Obertura Sintètica (SAR) i més concretament l'ús de la seva aplicació més notable, coneguda com Interferometria SAR (InSAR), ha experimentat un gran impuls, fent possible l'observació de fenòmens de desplaçament complexos amb precisions mil·limètriques. Aquests avanços estan permetent el desenvolupament d'eines flexibles per part de la indústria, laboratoris d'investigació i universitats, per a l'estudi de desplaçaments del terreny mitjançant tècniques InSAR, les quals s'estan adaptant per a la seva operativitat i integració amb observacions convencionals i models predictius.D'altra banda, quan es requereix d'una alta flexibilitat en termes de temps de revisita, o hi ha la necessitat d'adaptar l'orientació del sensor a les característiques específiques de la zona sota estudi, l'activitat de recerca d'un gran nombre de grups s'ha centrat en el desenvolupament de sensors SAR terrestres. Fàcils d'implementar i d'un menor cost en comparació amb solucions orbitals, aquests sensors representen una alternativa molt interessant per a la monitorització de zones localitzades. Malgrat tots aquests avantatges, tants els sensors SAR embarcats en plataformes orbitals com els terrestres presenten diferents limitacions, especialment, en àrees muntanyoses altament vegetades on normalment es produeixen les esllavissades. Mentre que el seu rendiment sobre àrees rocoses és molt satisfactori en absència de neu, poden aparèixer diferents limitacions degut a efectes de decorrelació temporal sobre zones amb vegetació, a distorsions en la imatge causades per la geometria d'adquisició, a la presència d'artefactes atmosfèrics severs en zones amb topografia abrupta o quan s'intenten analitzar desplaçaments de caràcter ràpid. Finalment, cal tenir en compte que els sensors SAR només són sensibles a la component de desplaçament a la línia de visió del satèl·lit i per tant, aquesta, pot diferir notablement de la real. Encara queda un cert camí per recórrer per superar totes aquestes limitacions i convertir a les tècniques InSAR en eines totalment operatives, context en què aquesta Tesi Doctoral s'ha desenvolupat.El principal objectiu d'aquesta Tesi Doctoral és el desenvolupament de tècniques InSAR per al monitoratge de zones afectades per esllavissades. En concret, el rendiment d'aquestes tècniques per a ambdues plataformes, orbital i terrestre, s'ha comparat i avaluat exhaustivament en el lliscament del Forn de Canillo, Andorra, que està considerat com una de les majors esllavissades dels Pirineus.Les tècniques presentades en aquesta Tesi Doctoral proporcionen evidències per a la presa de decisió, recolzades per la ciència, per tal de facilitar la gestió dels riscos associats amb les esllavissades.

This study demonstrates the value of historical aerial photographs as a source for monitoring long-term landslide evolution, which can be unlocked by using appropriate photogrammetric methods. The understanding of landslide mechanisms requires extensive data records; a literature review identified quantitative data on surface movements as a key element for their analysis. It is generally acknowledged that, owing to the flexibility and high degree of automation of modern digital photogrammetric techniques, it is possible to derive detailed quantitative data from aerial photographs. In spite of the relative ease of such techniques, there is only scarce research available on data quality that can be achieved using commonly available material, hence the motivation of this study. In two landslide case-studies (the Mam Tor and East Pentwyn landslides) the different types of products were explored, that can be derived from historical aerial photographs. These products comprised geomorphological maps, automatically derived elevation models (DEMs) and displacement vectors. They proved to be useful and sufficiently accurate for monitoring landslide evolution. Comparison with independent survey data showed good consistency, hence validating the techniques used. A wide range of imagery was used in terms of quality, media and format. Analysis of the combined datasets resulted in improvements to the stochastic model and establishment of a relationship between image ground resolution and data accuracy. Undetected systematic effects provided a limiting constraint to the accuracy of the derived data, but the datasets proved insufficient to quantify each factor individually. An important advancement in digital photogrammetry is image matching, which allows automation of various stages of the working chain. However, it appeared that the radiometric quality of historical images may not always assure good results, both for extracting DEMs and vectors using automatic methods. It can be concluded that the photographic archive can provide invaluable data for landslide studies, when modern photogrammetric techniques are being used. As ever, independent and appropriate checks should always be included in any photogrammetric design.

Le frane a lento scorrimento sono solitamente caratterizzate da tassi di spostamento da estramente lento, i.e. mm/anno a lento, i.e. centimetri/anno. Si sviluppano frequentemente in rocce metamorfiche foliate, e la deformazione è prevalentemente localizzata lungo una zona di taglio principale. Le caratteristiche mineralogiche, granulometriche e tessiturali di queste zone controllano sia il comportamento della frana che la sua possibile evoluzione. In questa tesi sono stati investigati sia il comportamento che l'evoluzione della zona di taglio, attraverso prove di laboratorio convenzionali (taglio diretto, le prove uniassiali e triassiali) e non convenzionali (ring shear apparatus). Le successive analisi hanno permesso di considerare sia la degradazione dal punto di vista mineralogico, che meccanico, valutando il ruolo di entrambe nella transizione da lenta a rapida (fenomeni di creep). Le prove sono state condotte su campioni provenienti dalla frana del Mont de La Saxe (MLS, Valle d'Aosta, Italia). La frana ha un volume stimato di circa 8x106 m3 e si estende tra 1,400 e 1,870 m a.s.l., su un'area di 150,000 m2. Questa frana interessa le frazioni di Entréves e di La Palud (Courmayeur), nonchè l'autostrada ed il tunnel del Monte Bianco che collega l'Italia alla Francia. Un altro caso studio comparitivo (Chervaz, Valle d'Aosta, Italia) è stato selezionato per effettuare i test di laboraorio, variando le litologie analizzate (scisti serpentinitici con elevata presenza di fillosilicati). La zona di taglio di MLS contiene sia fillosilicati (almeno il 20%) che grafite (circa il 10%) in grado di controllare le proprietà di attrito. Inoltre, la riduzione della granulometria è stata osservata durante il test con il ring shear apparatus insieme all’allineamento preferenziale delle particelle. Sono state derivate le caratteristiche di attrito e viscosità, come l'incremento di spostamento tangenziale prima dello stato stazionario e il comportamento di creep terziario. Il monitoraggio della frana di Mont de La Saxe è iniziato nel 2009 e negli anni seguenti è stato via via perfezionato. Il sistema di monitoraggio – ad oggi - è composto sia da strumentazione superficiale (e.g. GB-InSAR,…) che di strumentazione di monitoraggio installata in profondità (inclinometri, piezometri e DMS). Un monitoraggio così ampio è - probabilmente - un caso unico nelle Alpi. È stato osservato un chiaro comportamento stagionale, in particolare durante lo scioglimento delle nevi quando la frana mostra un massiccio incremento degli spostamenti (ad esempio, 2012, 2013 e soprattutto 2014). Inoltre, è stata investigata anche la frana del Ruinon (Valtellina, Italia) considerando la disponibilità di dati a lungo termine (dal 2006). È stata quindi condotta un'analisi statistica dei dati di monitoraggio, caratterizzando il comportamento della frana nel tempo e proponendo un nuovo approccio per definire le soglie di Early Warning. Infine, dopo la campagna sperimentale e la profonda analisi dei dati di monitoraggio, è stato sviluppato un modello matematico, basato sull’approccio proposto da Perzyna, in cui l’incrudimento subisce un processo di degradazione. I parametri del materiale sono stati calibrati sia con i risultati sperimentali precedentemente ottenuti e con i dati di monitoraggio. Le simulazioni numeriche attraverso questo modello danno l'evoluzione delle variabili cinematiche (spostamento, velocità e accelerazione) durante i risultati sperimentali. I risultati ottenuti in questa tesi contribuiscono alle nuove conoscenze relative allo sviluppo e all'evoluzione delle zone di taglio e forniscono anche una migliore comprensione di questi meccanismi combinando i test innovativi sviluppati con i dati sul campo in grado di sviluppare un modello per la previsione degli spostamenti delle frane. Infine, lo studio fornisce anche un nuovo approccio per definire le soglie di Early Warning.
Rockslides are characterized by slow to extremely slow displacement rates in their initial phases or for their entire evolution. They frequently occur in foliated metamorphic rocks. Field and monitoring evidence show that deformation is predominantly localized along a shear zone. Mineralogic, grain size and fabric characteristics of the shear zone control its behavior and the possible evolution of the rockslide from a slow creeping to a fast moving one. In this thesis we investigate the shear zone behavior and evolution through conventional (direct shear, standard uniaxial compression and triaxial test) and unconventional laboratory testing (with an ring shear apparatus). We try to merge mineralogic data with material degradation and their role in the transition from slow to fast evolution due to creep phenomena, the change in material behavior with shear displacement and velocity. The tests were carried out on samples collected from boreholes through cataclastic shear zones within the Mont de La Saxe (MLS) rockslide, Valle d’Aosta region, Italy, at the extreme termination of a Deep-seated Gravitational Slope Deformations. The rockslide volume is of about 8x106 m3, and it extends between 1,400 and 1,870 m a.s.l., over area of 150,000 m2. This landslide is located close to Entréves and La Palud (Courmayeur municipality) villages and to the Mont Blanc highway that connects Italy to France through a tunnel. Laboratory tests were also performed on samples from the Chervaz rockslide (Valle d’Aosta region) located in a different rock suite (e.g. serpentine schist with phyllosilicates). The MLS shear zone contained both phyllosilicates (at least 20%) and graphite minerals (about 10%) which can control frictional properties. Furthermore, grain size reduction has been observed during slow ring shear testing together with particles rearrangement. Frictional and viscous characteristics, such as the tangential displacement increment before the steady state and the tertiary creep behavior, have been derived. The long-term monitoring of this instability started on 2009 and during the following years has been improved. The monitoring system is composed by ground surface (GB-InSAR, optical targets, TLS surveys, GPS network) and deep-seated equipment (inclinometers, piezometers and DMS probes). Such an extensive monitoring is – probably – a unique case in the Alps. A clear seasonal behavior has been observed, especially during snow-melt season when the rockslide shows a massive increment of displacements (e.g. 2012, 2013 and especially 2014). An addition a case study was selected, the Ruinon rockslide (upper Valtellina, Italian Alps) because of the long-term available dataset (since 2006). A statistical analysis of monitoring data has been completed, in order to characterize to behavior of the rockslides through time and to propose a new approach to define Early Warning displacement rate thresholds. Finally, after the experimental campaign and the deep analysis of monitoring data, a mathematical model, based on the Perzyna’s delayed plasticity theory, in which the hardening rule considers the degradation process, has been developed. The material parameters were calibrated on the experimental results previously obtained and using the monitoring data. The numerical simulations through this model give the evolution of the kinematic variables (displacement, velocity and acceleration) during the experimental results. The results contribute new knowledge regarding the shear zone development and evolution and also provide an improved understanding of these mechanisms by developing one of the first high quality data sets that combines new laboratory tests and field data able to develop a model in order the landslide forecasting. Finally, the study provides a new approach to define Early Warning displacement rate thresholds for slope failures.

This thesis investigates the design, implementation and validation of a multi-antenna GPS system to monitor the displacement of deforming slopes. The system utilises a switched antenna array design allowing data from multiple antennas to be sampled sequentially by one GPS receiver. The system provides quasi-continuous GPS observations that can produce a precise and reliable coordinate time-series of the movement of the slope under consideration. GPS observations and particularly those concerned with the monitoring of steep slopes, are subject to systematic errors that can significantly degrade the quality of the processed position solutions. As such, this research characterises the data in terms of multipath effects, the spectrum of the coordinate time-series, and the carrier to noise power density ratio of the raw GPS observations. Various GPS processing parameters are then investigated to determine optimal processing parameters to improve the precision of the resulting coordinate time-series. Results from data stacking techniques that rely on the daily correlation of the repeating multipath signature find that the GPS data actually decorrelates somewhat from day to day. This can reduce the effectiveness of stacking techniques for the high precision monitoring of steep slopes. Finally, advanced stochastic models such as elevation angle and carrier-to-noise weighting are investigated to optimise the precision of the coordinate time-series data. A new in-line stochastic model is developed based on weighting GPS observations with respect to the level of systematic error present within the data. By using these advanced types of stochastic models, reductions to the noise level of the coordinate time-series of approximately 20 and 25 percent are possible in the horizontal and height components respectively.Results from an extensive field trial of this system on a deforming high-wall of an open-pit mine indicate that approximately 135mm of displacement occurred over the 16-week field trial. The precision of the coordinate time-series for surface stations approaches ±4.Omm and ±5.4mm in the horizontal and height components respectively. For sub-surface stations next to the mine wall, coordinate precision has been determined as ±4.9mm.component and ±7.6mm in the height component respectively.

This thesis investigates the design, implementation and validation of a multi-antenna GPS system to monitor the displacement of deforming slopes. The system utilises a switched antenna array design allowing data from multiple antennas to be sampled sequentially by one GPS receiver. The system provides quasi-continuous GPS observations that can produce a precise and reliable coordinate time-series of the movement of the slope under consideration. GPS observations and particularly those concerned with the monitoring of steep slopes, are subject to systematic errors that can significantly degrade the quality of the processed position solutions. As such, this research characterises the data in terms of multipath effects, the spectrum of the coordinate time-series, and the carrier to noise power density ratio of the raw GPS observations. Various GPS processing parameters are then investigated to determine optimal processing parameters to improve the precision of the resulting coordinate time-series. Results from data stacking techniques that rely on the daily correlation of the repeating multipath signature find that the GPS data actually decorrelates somewhat from day to day. This can reduce the effectiveness of stacking techniques for the high precision monitoring of steep slopes. Finally, advanced stochastic models such as elevation angle and carrier-to-noise weighting are investigated to optimise the precision of the coordinate time-series data. A new in-line stochastic model is developed based on weighting GPS observations with respect to the level of systematic error present within the data. By using these advanced types of stochastic models, reductions to the noise level of the coordinate time-series of approximately 20 and 25 percent are possible in the horizontal and height components respectively.
Results from an extensive field trial of this system on a deforming high-wall of an open-pit mine indicate that approximately 135mm of displacement occurred over the 16-week field trial. The precision of the coordinate time-series for surface stations approaches ±4.Omm and ±5.4mm in the horizontal and height components respectively. For sub-surface stations next to the mine wall, coordinate precision has been determined as ±4.9mm.component and ±7.6mm in the height component respectively.

Recently, the use of unmanned aerial vehicles (UAVs) has increased in popularity across several industries. Most notable, however, is the impact that this technology has had in research at academic institutions worldwide. As the technology for UAVs has improved, with that comes easier to operate, more accessible equipment. UAVs have been used in various types of applications and are quickly becoming a preferred method of studying and analyzing a site. Currently, the most common use of a UAV is to monitor a location of interest to a researcher that is difficult to gain access to otherwise. The UAV can be altered to meet the needs of any given project and this versatility has contributed to their popularity. Often, they are equipped with a type of remote sensor that can gather information in the form of images, sounds, heat, or light. Once data has been gathered from a site, it is processed and modified, allowing it to be studied and analyzed. A process known as Structure from Motion (SfM) creates a 3D digital terrain model from camera images captured through the use of a UAV. SfM is a common method of processing the vast amount of images that are taken at a site and the 3D model that it creates is a helpful resource for analysis. These digital models, while useful, are oftentimes created at an unknown accuracy. This research presents a comparative study of the accuracies obtained when different parameters are applied during the SfM process. The results present a comparison of the time required to process a particular model and the accuracy that the model had. Depending on the application and type of project, a desired level of accuracy can be obtained in the presented amount of time. This particular study used a landslide as the site of interest and captured the imagery using a helicopter UAV.

The work is focused on the study of the Passo della Morte landslide, the so-called landslide 3, located in northern Italy, in Province of Udine (UD). The landslide is moving at an extremely slow rate of 2-3 cm/year and has been studied for more than 15 years due to the presence of a road tunnel that crosses it. Several features that characterise the Passo della Morte area and that are considered interesting for the purpose of building the reference geological and numerical models of landslide 3 have been described. At first, an overview of the methods for the slope stability analysis has been carried out. The main part of the work has been focused on the building of a numerical model of the landslide. The main objective of the modelling was to obtain a representation of the phenomena similar to those observed with surveys and monitoring. The reference data have been taken from the monitoring devices present on the landslide body and in the surrounding area. In order to model the landslide, the commercial software RS3 has been used; it is a three dimensional analysis software based on the finite element method. In order to build a reference model, a series of test models was built. Once obtained the reference geometry and defined the geomechanical parameters, the model was calibrated comparing its results with the data coming from the monitoring. The similarity between observed displacements and those shown by the model, and the minimal difference between the results obtained using two different failure criterions are a confirmation of the reliability of the model. The analysis was repeated implementing a groundwater surface defined based on a hydrogeological map of the area. The new results confirmed the reliability of the model. Various attempts were done in order to implement the existing drainage adit and simulate its influence on the groundwater but problems in the definition of the boundary conditions did not permit to achieve satisfactory results.

Esta dissertação apresenta o estudo sobre um caso de movimento rotacional em uma massa de solo coluvionar, localizada na Vila Albertina na zona norte da cidade de São Paulo-SP. O objetivo deste trabalho foi estudar os processos de instabilidade associados a eventos de chuvas, condições de fluxo e ações antrópicas que ocorreram no local. Procurou-se estabelecer as relações de causa e efeito que os eventos pluviométricos têm sobre a estabilidade da encosta; também foram estudadas as alterações causadas pelo homem e as condições de infiltração de água no terreno. Foi realizado um levantamento histórico de escorregamentos ocorridos na região desde a década de 30. Este levantamento histórico constituiu em resgatar aerofotografias, imagens de satélites e reconstituições de plantas topográficas do local. Através deste estudo se constatou que a encosta começou a ser modificada desde a década de 40, com uma possível tentativa de exploração de rochas graníticas. Nos anos 60 foi construída uma fábrica no pé da encosta. Atualmente, o solo desta encosta, que está em movimento, invade o pátio desta fábrica. Na década de 70, a área de escorregamento começou a ser ocupada por moradores, que construíram suas casas sobre esta encosta. Esta ocupação foi desordenada e acelerou o processo de instabilização da encosta; até o ano de 2004 viviam no local 600 famílias. No início da década de 80, a encosta apresentou grandes movimentações. Para que estes movimentos fossem cessados, realizaram-se obras de contenção, foram executados retaludamentos, instalações de drenos profundos e drenagens superficiais através de canaletas e escadas hidráulicas. Ainda na década de 80, retirou-se uma grande camada de solo da encosta para cobrir o aterro sanitário da Vila Albertina, localizado no terreno vizinho a encosta. Esta remoção deixou parte do terreno plano, causado o acumulo de águas pluviais. As águas, que antes escoariam superficialmente, passaram a se infiltrar no terreno. Para a caracterização e obtenção dos parâmetros de resistência dos solos da região, foram coletadas três amostras indeformadas: uma na crista do escorregamento e duas no pé da encosta. Neste local, foram identificados um solo coluvionar e um solo residual mais jovem. A encosta foi instrumentada através de marcos superficiais, inclinômetros que também serviram de medidores de nível d\'água e tensiômetros.
This paper presents a study on a rotational movement in a colluvial soil mass located at Vila Albertina, northern region of São Paulo City. The main purpose of this work is to study the processes of instability related to rainfalls, conditions of flow and human actions that occurred at the site. It was intended to establish cause and effect relations pluviometric events have over the stability of the slope. It also studies alterations caused by men and water infiltration conditions on the land. A historical survey of ground sliding data on the region since the 1930s was gathered. This survey was composed of retrieved material such as aerial photographs, satellite images and topographic plans reconstitutions of the location. By means of this study, it was possible to verify that the slope started to be modified since the1940s, with a possible attempt of granite rocks exploitation. In the 60s, a factory was built on the bottom of the slope. Nowadays, the soil of this slope, which is in movement, is invading the courtyard of this factory. In the 70s, the sliding area started to be occupied by inhabitants, who built their homes on this slope. This disorderly occupancy accelerated the instability of the slope; until 2004, 600 families were living in the location. In the beginning of the 80s, the slope presented considerable movements. In order to stop them, contention constructions were executed, as well as re-sloping, installation of deep drains and superficial drainage by channels and hydraulic stairs. Still in the 80s, a great layer of the slopes soil was taken to cover Vila Albertinas sanitary landfill, located at land nearby. This removal left part of the ground plain, causing an accumulation of pluvial water. The pluvial water, which would superficially drain, started to infiltrate into the ground. To characterize and acquire the regions soil resistance parameters, three undisturbed samples were collected: one at the top of the sliding and two at the bottom of the slope. In this area, colluvial and a more recent residual soil were identified. The slope was monitored by superficial indicators, tensiometers and inclinometers that were also used to measure the water level.

Les réseaux de capteurs permettent une surveillance multi-paramètres de zones d'étendue limitée grâce à la coopération d'un ensemble de récepteurs déployés in-situ qui gèrent l'acquisition, le traitement et le transfert de données. Afin de coupler le concept de réseaux de capteurs et un positionnement précis des récepteurs à l'aide de puces GPS mono-fréquence, l'Institut National de l'Information Géographique et Forestière (IGN) a mis au point le Geocube.La première partie de ce travail a été consacrée au développement d'une stratégie d'acquisition, de transfert et de traitement des données GPS des Geocubes pour permettre un positionnement précis et en temps-réel des récepteurs au sein du réseau. Un traitement utilisant les observations de phase GPS ainsi qu'un filtrage de Kalman a été adopté. Cependant, les séries temporelles de positions brutes sont entachées de l'effet des multitrajets. Diverses méthodes d'atténuation de ce phénomène sont alors proposées. Au final, une précision infra-centimétrique à millimétrique est atteinte.La seconde partie de cette thèse a été consacrée à l'application de réseaux de Geocubes pour l'étude d'objets géophysiques. Deux sites d'étude ont été sélectionnés: le glissement de terrain de Super-Sauze dans la vallée de l'Ubaye et le glacier d'Argentière dans le massif du Mont-Blanc. La dynamique des objets d'intérêt peut alors être étudiée à une échelle infra-journalière grâce à la précision et à la grande résolution temporelle du positionnement des Geocubes. De plus, la densité des réseaux de mesure et leur facilité d'installation permet d'instrumenter la grande majorité des points où un besoin de surveillance est identifié
Wireless Sensor Networks (WSN) allow a multi-parameters monitoring of small extend areas thanks to cooperative data acquisition, transfer and processing. In order to combine WSN with a precise positioning of the receivers within the network using single frequency GPS modules, the Geocube has been developed by the French National Institute of Geographic and Forest Information (IGN-France). The first part of this work focused on GPS data management and processing to allow the relative positioning of the Geocubes within a local network. To this end, a processing method customized for Geocube data and WSN environment was developed. It is based on the use of GPS carrier phase double differences and a Kalman filtering. Due to the basic GPS antenna used into the Geocube to minimize its price and its size, multipath affect position time series. Various strategies are proposed for multipath mitigation, and finally a sub-centimeter to millimeter level accuracy is reached for relative positioning depending on measurement conditions.The second part of this work was devoted to the use of Geocube networks for geophysical structures monitoring. Two test sites were selected: the Super-Sauze landslide (Ubaye valley, Alpes de Haute-Provence, France) and the Argentière glacier (Mont-Blanc massif, Haute-Savoie, France). The dynamics of the studied areas was investigated at a sub-daily time scale thanks to the high accuracy and the high time resolution of positioning time series derived from Geocubes. In addition, positioning data were acquired quite everywhere a deformation measurement was needed thanks to the low-cost of Geocubes and their easy set up

Захищається положення про те, що розвиток зсувоутворення тісно пов'язаний не тільки з загальновідомими чинниками, але й з динамікою неотектонічних рухів, як прояву глобальних геодинамічних процесів, та проявами сейсмічної активності, що обгрунтовано аналізом зв'язків кількості, розмірів зсувів та інших статистичних показників, які їх характеризують, з місцезнаходженням зсувних ділянок по відношенню до певних структурно-тектонічних зон Закарпаття, яким властиві різні рівні інтенсивності варіацій природного імпульсного електромагнітного поля Землі. На цій основі пропонується реалізувати районування територій Закарпаття за схильністю до активізації зсувонебезпечних процесів. В роботі теоретично обгрунтовано механізм утворення шару динамічних деформацій. Показано, що підготовка зсувів в значній мірі забезпечується розвитком деформаційних процесів в цьому шарі, внаслідок чого утворюється поверхня ковзання. Вивчення динамічних змін в ІПДД при забезпеченні їх реєстрації високоточними геофізичними методами є основою моніторингу зсувних процесів. Запропонована нова технологія робіт методом природного імпульсного електромагнітного поля Землі, яка забезпечується використанням розробленого приладу РХІНДС-ПМ, удосконаленою методикою польових робіт, системою обробки даних польових спостережень згідно з запропонованим алгоритмом, що дозволяє застосовувати даний метод для режимних спостережень як складової частини системи моніторингу зсувів. В комплексі геофізичних методів для дослідження зсувонебезпечних ділянок основним стає метод зондування становленням електромагнітного поля в ближній зоні завдяки розробці принципово нової електророзвідувальної станції. Стає вивчення верхньої частини розрізу, яка забезпечує отримання кількісних параметрів для розрахунку просторово-часових змін фізико-механічних властивостей порід.
Защищается положение о том, что развитие оползнеобразования тесно связано не только с общеизвестными факторами, но и с динамикой неотектонических движений, как проявления глобальных геодинамических процессов, и проявлениями сейсмической активности, что обосновано анализом связей количества, размеров оползней и других статистических показателей, которые их характеризуют, с местоположением оползневых участков по отношению к известным структурно-тектоническим зонам Закарпатья, которым свойственны различные уровни интенсивности вариаций естественного импульсного электромагнитного поля Земли. На этом основании предлагается реализовать районирование территории Закарпатья по склонности к активизации оползнеопасных процессов. В работе теоретически обосновано механизм образования слоя динамических деформаций. Показано, что подготовка оползней в значительной мере обеспечивается развитием деформационных процессов в этом слое, вследствие чего образуется поверхность скольжения. Изучение динамических изменений в ПІДД при обеспечении их регистрации высокоточными геофизическими методами является основанием мониторинга оползневых процессов. Предложена новая технология работ методом естественного импульсного электромагнитного поля Земли, которая обеспечивается использованием разработанного прибора РХІНДС-ПМ, усовершенствованной методикой полевых работ, системой обработки данных полевых наблюдений в соответствии с предложенным алгоритмом, что позволяет использовать данный метод для режимных наблюдений как составной части системы мониторинга оползней. В комплексе геофизических методов для исследования оползнеопасных участков основным становится метод зондирования становлением электромагнитного поля в ближней зоне благодаря разработке принципиально новой электроразведочной станции “Стадія-М” для изучения верхней части разреза, которая обеспечивает получение количественных параметров для расчета пространственно-временных изменений физико-механических свойств пород и устойчивости оползней.
It is advocated that the development of the landsliding is closely connected not only with well known causes but also with dynamics of the neotectonic movements as manifestation of global geodynamic processes and seismic activity that is proved by analysis of the connection of quantity and sizes of landslides and other statistic indexes which characterize them with the localization of the landslides area in connection with know structural-tectonic zones of the Transcarpathians with intrinsic different levels of the intensity variation of natural impulsive electromagnetic field of the Earth. On this base it is propose to realize the zoning of the Transcarpathian territory on predisposition to the activization of the landslide hazard processes. It is grounded the mechanism of the layer dynamic deformation origin It is shown that preparation of the landslides to certain degree is ensured by deformation processes in this layer. As a result the slikenslides are forming. The study of the dynamic changes in LDD by their registration of high accurate geophysical methods is the base of monitoring of landslide processes. It is proposed of the new work technology by using the methods of the natural impulsive electromagnetic field of the Earth which ensure by worked out equipment RHINDS - PM, improved field methods, system of the field data elaboration according to proposed algorithm that allow to use this method for the regime investigations as part of landslide monitoring. The method of sounding by adjusting of the electromagnetic field in dip zone due to the working out of principal new electroprospecting station “Stadia - M” for the study of the upper part of the section which ensure the gathering qualitative parameters for the calculation of the space-time changes of the physic-mechanic parameters of the rocks and stability of the landslides became the main one in the complex of the geophysical methods of landslide hazard parts.

Nous souhaitons connaître les processus qui contrôlent les glissements de terrain lents à l'aide de méthodes sismiques passives. Nous installons des dispositifs d'écoute sismique sur les sites de Super-Sauze (France) et de Valoria (Italie). Nous détectons, localisons et caractérisons trois types principaux de signaux sismiques. Un type est associé aux séismes régionaux donc externe à la dynamique des glissements. Les deux autres sont localisés dans des foyers de fissures ou des ruptures de pente. Nous suggérons que le premier type est associé à des écroulements depuis l'escarpement et à du transport en surface, tandis que le second type est associé à des fractures et des cisaillements. On montre qu'il existe des corrélations entre ces signaux, les déplacements en surface et les précipitations. Les glissements de terrain sont des volumes variables dans le temps et dans l'espace, ce qui impose une maintenance régulière des équipements et complexifie l'acquisition de données permanentes.

碩士
聖約翰科技大學
電子工程系碩士班
99
Taiwan climate have typhoon and mudslide ,This paper Proposes innovative image-based monitoring methods,Using a single image to achieve monitoring, measuring displacement and direction. The method of landslide monitoring system is not measuring land appearance displacement, so do not compare the before and after image to calculate the landslide displacement. And this system does not need high-performance computer and DSP system, it has some advantages include: simple structure, high processing speed, low cost and low power consumption. This research is coming from our former research IBDMS (Image-Based Distance Measurement System), using a visible laser projector projection for a long distance. Set a “coordinates scale board” in analyze zone, it will generate a laser spot on “coordinates scale board”. The CCD camera is setting behind the “coordinates scale board” to capture the image, to calculated landslide displacement and direction in 50-200 meters away by using some simple formulas.

Landslides are one of the most dangerous geological hazards. In the United States, landslides cause a damage of $ 3.5 billion and kill 25 to 50 people annually. Shallow landslides occurring near any transportation facilities (railways and highways) can cause economic loss and disturbance of services which lead to indirect economic loss. It also increases the maintenance cost of those facilities. Hence, facilities located near a shallow landslide prone area should be monitored so as to avoid any catastrophic damages. Soil moisture and movement of the soil mass are prime indicators of potential shallow slide movements. This assessment of wireless instruments considers a variety of devices ranging from devices for monitoring tilt and moisture at specific points in the soil mass to ground penetrating radar (GPR), which can give indications of moisture accumulation in soils over a wide spatial extent. For this assessment study, a low cost MEMS accelerometer was selected for measuring tilts and motions. And EC type soil moisture sensor was selected to measure soil moisture content of embankments. The instrumentation of railway embankments works effectively and cheaply when a suspected problem area has already been identified and monitoring is needed over a limited spatial extent. This makes the monitoring system highly localized which often fails to cover potentially new failure prone areas. It is not feasible to use this approach to monitor soil conditions along the entire alignment of the railway. Therefore, another approach, GPR, is defined and explained in this study. GPR measures the dielectric constant value for any given material including soils. In soils, the dielectric constant value depends on the volumetric amount of water content present in a soil. Due to moisture infiltration, there is a reduction in suction value on embankment which indicates a decrease in shear strength of slope. Therefore, a correlation between suction and dielectric constant value is formulated in this study using Complex Refractive index model/Time propagation (CRIM/TP) model for soils. To validate this theoretical correlation, a laboratory study was conducted on pure kaolinite and on normal soil. For pure kaolinite this correlation proves beneficial while, for other type of soil, the correlation was off due to the limitations in filter paper test to measure suction below 2.5pF.

Tesi di ricerca sul monitoraggio di fenomeni di deformazione al suolo e di infrastrutture effettuata attraverso l’utilizzo di tecniche interferometriche di base ed avanzate. Il lavoro è stato svolto presso il Dipartimento di Scienze della Terra di Firenze-Università degli Studi di Firenze (DST-UNIFI) e presso l’Institut de Geomàtica, all’interno del CTTC (Centre Tecnològic Telecomunicacions Catalunya), Castelldefels, Barcelona, Spagna. This thesis work aims to demonstrate the potential of SAR interferometry as a tool for detecting and monitoring hydrogeological instability. This goal is achived by means of a compilation of interesting results obtained applying different DInSAR methodologies and analysed at different scale levels: form single infrastructures up to regional map. The greatest importance of this scientific work is how the combination of InSAR and geomorphologic tools to improve hydrogeological risk assessment both at regional and local scale.

碩士
國立聯合大學
防災科技研究所
95
This research attempts to test the feasibility of the active wave detecting with passive natural seismic wave monitoring the property variation of slope-landside in the backyard of the Department of Civil Engineering of the school, and in two mountain fields of Tongluo Jiuhua and Sanyi Huoyan. The active wave seimic prospecting is used to detect the waveform, spectra and wavespeed of the site earth conditions, while the natural seismism is motoring those of waveform and spectra only. The active-wave results show that the seismic refracted inversion method is suitable for predicting the wave speed of the surface layer, and the active wave is suitable for detecting the property variation of slope-landslides because the waveform, spectra and wavespeed are stable under the same site conditions, but changeable under different site conditions such as torrential rains or debris flows. Also we found that the P-wave velocities of surface layer is slower about one third in the sunny day than those in the rainy day, and the energy evolution manner from solid debris state to soft debris state.The natural micro seismic monitoing results also show the energy evolution process that the natural frequencies of the earth spectra is more concentrated and higher in the dry debris, then is less concentrated and dispering when beginning raining, and then is reconcentrated at lower frequencies less about 10Hz after large raining such that the surface earth is tend to saturated. Towards the research direction, the methods may help monitor and prewarn the landslide or debris flow in the future. Keyword: seismic prospecting, micro seismic wave , active detection , passive monitor, spectra.

In the last decade satellite remote sensing has become an effective tool for monitoring geo-hazard-induced ground motions, and has been increasingly used by scientific community. Geo-hazards direct and indirect costs are currently rising, causing serious socio-economics and casualty losses. Therefore, creating a priority list turns out to be essential to highlight the most relevant ground deformations and to better focus the risk management practices at regional scale. The Sentinel-1 constellation, thanks to the 6-days repeatability and the free availability of the data, allows to easily update the geo-hazard-induced ground motions, compared to other kind of satellite sensors. In this PhD Thesis, the potentialities and drawbacks of the interferometric technique have been presented and then exploited to define three different procedures, applied in different environment and at different scales, for the use of multi-band PSI products. This thesis work represents the main outcome of a three yearslong activity at the Department of Earth Sciences of the University of Florence, Centre technologic de telecomunicacions de Catalunya research center and TRE-Altamira (Barcelona). The main goal is to test and evaluate the potential and applicability of space-borne SAR data, processed by means of different PSI approaches, as operational tools for the characterization of geohazards in different geological and geomorphological environments. For this work, two Italian test areas at regional scale are been selected: Tuscany and Valle d’Aosta Regions. Furthermore a site at detailed scale was analyzed, the mining area of Saline di Volterra (Tuscany). The main goal of the thesis hinges on illustrating different methodologies that could be merged in one single workflow to detect active moving areas, characterize them in detail and cross-correlate the satellite data with ancillary information, implementing the obtained products and results in the Civil Protection chain and geohazard risk management. The proposed case studies were intended as examples, although referred to different environments and geohazards, for the working approaches to be used from regional to detailed scale. For the Tuscany Region, there were exploited Sentinel-1 images for active moving areas detection at regional scale. A hotspot-like methodology was used, exploiting the temporal repetitiveness of Sentinel-1 data analysed by means of the SqueeSAR algorithm to create deformation maps in three different periods with a 6 months update. Thanks to a filtering approach based on a velocity threshold, it was possible extract a total of 652 deformation clusters, divided in three different periods, to study their spatial and temporal evolution. The final output is a flexible geo-database that contains interferometric parameters, geographical, geomorphological and geological information, a brief evaluation of the possible triggering cause and information about the temporal evolution of the moving areas. For the Valle d’Aosta Region, it was used a clustering analysis applied to a large stack of Sentinel-1 satellite interferometric products that has been derived using the SqueeSAR algorithm. Valle d’Aosta Region is an alpine region characterized by a wide spectrum of mass wasting phenomena. The approach, based on simple GIS tools and indexes, allowed detecting 277 moving areas above the selected velocity threshold. Overall, landslides (complex, rotational, Deep Seated Gravitational Slope Deformation (DSGSD)), rock glacier evolution and detrital-related deformation are responsible for the detected motions. In mountainous areas, where the field data collection is sometimes limited or impossible, the presented approach is intended to create priority areas to be focused for further investigations. In this way, it is possible to increase, with reduced economic and personnel costs, the “landslide knowledge” of all the actors involved within the landslide risk management chain at regional scale. In this context, easily updatable clustering methodologies are very useful tools for MTInSAR data analysts; it is possible to obtain reliable results in a fast way and to compare them with previous results. Well knowing the limitations of the interferometric technique, especially in mountain regions, it is reasonable to rely on clustering approaches in order to derive multi-temporal synoptic views of ground motions over wide areas. For the Saline di Volterra case, it is presented a local scale application of multi-temporal satellite interferometry targeting a solution mining area in southern Tuscany. The surroundings of Saline di Volterra host several brine wells that pump water into a salt level at a depth ranging between 60 and 400 m below surface. The mining activity has a relevant environmental impact in terms of depletion of the water resources and in terms of ground motion, creating several sinkholes which were mapped through multi-temporal analysis of orthophotos. The deformation map, obtained through the analysis of Sentinel-1 images, revealed the presence of several subsidence bowls, sometimes corresponding to sinkholes formed in the recent past. The subsidence bowls have a common deformation pattern, with LOS velocities increasing forward the center of the bowl. The temporal evolution of the measurement points can vary a lot on case-basis. Finally, a correlation between LOS velocities and age of formation of sinkholes have been found. The Sentinel-1 images were processed with an ad hoc processing chain, elaborated in Centre Technologic Telecomunicacions Catalunya research center (Barcelona). With this new procedure, it was possible to detect fast deformation rates that are usually puzzling to solve in mining areas. This detailed scale and target-oriented approach demonstrated its capability to provide useful information in terms of density of measurement points and quality of the time series.

The research concerns the effects of landslides on linings tunnel. The monitoring data elaboration of a real case defined the distinctive elements that characterize the behavior of the tunnel linings, highlighting differences with those not involved in landslides. The problem of interaction has been generalized and numerical studies provided correlation between the landslide movements and mechanical response of the tunnel lining.

Occurring in many geographical, geological and climatic environments, landslides represent a major geological hazard. In landslide prone areas, monitoring devices associated with Early Warning Systems are a cost-effective means to reduce the risk with a low environmental and economic impact, and in some cases, they can be the only solution. In this framework, particular interest has been reserved for Wireless Sensor Networks (WSNs), defined as networks of usually low-size and low-cost devices denoted as nodes, which are integrated with sensors that can gather information through wireless links. In this thesis, data from a new prototypical ground instability monitoring instrument called Wi-GIM (Wireless sensor network for Ground Instability Monitoring) have been analysed. The system consists in a WSN made by nodes able to measure their mutual inter-distances by calculating the time of flight of an Ultra-Wide Band impulse. Therefore, no sensors are implemented in the network, as the same signals used for transmission are also used for ranging. The system has been tested in a controlled outdoor environment and applied for the monitoring of the displacements of an actual landslide, the Roncovetro mudflow in Central Italy, where a parallel monitoring with a Robotic Total Station (RTS) allowed to validate the system. The outputs are displacement time series showing the distance of each couple of nodes belonging to the same cluster. Data retrieved from the tests revealed a precision of 2–5 cm and that measurements are influenced by the temperature. Since the correlation with this parameter has proved to be linear, a simple correction is sufficient to improve the precision and remove the effect of temperature. The campaign also revealed that measurements were not affected by rain or snow, and that the system can efficiently communicate up to 150 m with a 360° angle of view without affecting precision. Other key features of the implemented system are easy and quick installation, flexibility, low cost, real-time monitoring and acquisition frequency changeability. The comparison between Wi-GIM and RTS measurements pointed out the presence of an offset (in an order that vary from centimetric to decametric) constant for each single couple, due mainly to the presence of obstacles that can obstruct the Line Of Sight (LOS). The presence of vegetation is the main cause of the non-LOS condition between two nodes, which translates in a longer path of the signals and therefore to a less accurate distance measurements. To go further inside this issue, several tests have been carried out proving the strong influence of the vegetation over both data quantity and quality. To improve them, a MATLAB tool (R2018a, MAthWorks, Natick, MA, USA) called WiSIO (Wireless Sensor network Installation Optimizer) has been developed. The algorithm finds the best devices deployment following three criteria: (i) inter-visibility by means of a modified version of the Hidden Point Removal operator; (ii) equal distribution; (iii) positioning in preselected priority areas. With respect to the existing viewshed analysis, the main novelty is that it works directly with 3D point clouds, without rendering them or performing any surface. This lead to skip the process of generating surface models avoiding errors and approximations, that is essential when dealing with vegetation. A second installation of the Wi-GIM system has been therefore carried out considering the deployment suggested by WiSIO. The comparison of data acquired by the system positioned with and without the help of the proposed algorithm allowed to better comprehend the effectiveness of the tool. The presented results are very promising, showing how a simple elaboration can be essential to have more and more reliable data, improving the Wi-GIM system performances, making it even more usable in very complex environments and increasing its flexibility. The main left limitation of the Wi-GIM system is currently the precision. Such issue is connected to the aim of using only low-cost components, and it can be prospectively overcome if the system undergoes an industrialization process. Furthermore, since the system architecture is re-adaptable, it is prone to enhancements as soon as the technology advances and new low cost hardware enters the market.

碩士
明道管理學院
環境規劃暨設計研究所
94
The earthquake occurred on September 21, 1999 caused not only heavy casualties and extensive damage to buildings, but also a large number of landslides in central Taiwan. Due to scattered distribution of landslides, satellite images were used to rapidly monitor and evaluate the change of the large-scale landslides. Currently, the Jou-Jou Mountain area was proposed as a Nature Reserve Area by the Taiwan Forestry Bureau to restore the natural landscape and ecosystem. There have been over six years since earthquake occurred. It is essential to assess the change of landslide sites. The objectives of this study are to analyze multi-temporal SPOT images from 1999 to 2003 years, and monitor the change and vegetation recovery condition of landslide sites by using Normalized Difference Vegetation Index (NDVI), image change analysis and vegetation recovery rate (VRR). The analyzed results show that the sites of landslide have been gradually restored, the areas decreased from 958.359 ha on September 27, 1999 to 163.672 ha on July 20, 2003. The corresponding VRR has been restored to 70.46% on July 20, 2003 without human interference, which shows that nature itself has quite robust vegetation restoration ability. Additionally, the landslide change evaluation also shows that there are over 84.921 ha of enlarging landslide sites identified on July 20, 2003, most of which primarily concentrated on ridgelines and concave river bank. Using multi-temporal SPOT satellite images can effectively assess and monitor the landslide and its VRR for the reference of decision making and policy planning in the landslide area.

碩士
國立中央大學
土木工程學系
107
The automatic monitoring systems are gradually concerned for disaster prevention in Taiwan recently. Time Domain Reflectometry (TDR) is one of valuable technique for landslide monitoring. It is a passive-based monitoring method which provides multi-functions, such as water level, bridge scour, landslide, and suspended sediment concentration (SSC), based on a single TDR device via a multiplexer. In addition, the Real Time Kinematic (RTK) based single frequency GPS sensor can provide the centri-meter for the surface displacement and direction of the landslide. Thus, this study integrate the low-cost monitoring device with single frequency GPS three-axis accelerometer for surface displacement monitoring, as well as the TDR for sliding surface monitoring. Consequently, the proposed monitoring system not only can provide diverse monitoring data at field-side, but also have three thresholds for early waring of the landslide. Furthermore, the Open Geospatial Consortium (OGC) provided SensorThings API, which has a standardized definition for the sensor description, observed position, and observed feature. Because it is based on JSON and Restful proctols, the content of SensorThings API is lighter and more liberal than Sensor Observation Service (SOS). Besides, it realizes data interoperable way by providing web service. This study also improved a middleware, which is between SOS and the existing TDR monitoring platform, by providing TDR heterogeneity data interoperability via SensorThings API finally.

博士
國立中正大學
應用地球物理研究所
99
Taiwan is located not noly in the tectonic collision zone between Eurasia plate and Philippine sea plate but also in the most active tropical cyclone region, so that many nature disasters occur, such as earthquakes, landslides and debris flows (LMDF), storms, floods and so on. These natural disasters often cause damages to lives and properties and economic loss, so how to treat these disasters is an important subject. This dissertation will study and discuss earthquakes and LMDF, respectively. Identifying the rupture plane of an earthquake doublet is a very challenging problem. Because the pair of events often occurs in close space and time with almost the same magnitude, most long-period waveforms of an earthquake doublet are severely tangled and thus unsuitable for conventional waveform inversion methods. The SSA identify a seismic source based on brightness function, defined as the summation of the normalized waveform amplitudes at the predicted arrival time at all stations. By illuminating the spatiotemporal distribution of asperities in an earthquake’s source process, we are able to constrain the orientation of the rupture propagation that, in turn, leads to the identification of the fault plane. In this study, I try to resolve this issue, not only on Ila earthquake doublet of 2005 March 5 but also on Jiashian earthquake of 2010 March 4, by utilizing the SSA. Finally, I design an automatic processing tool to identify the rupture plane of earthquake, so as to provide more clear fault rupture structures for Taiwan. The typhoon, Morakot, passed Taiwan during 7 to 9 August 2009 and dumped as much as 1800 mm of rain for the island and caused heavy life and economic loss. During typhoon Morakot’s passage across Taiwan, many LMDF events were detected by the regional broadband seismograph network. In this study, I find that the first character of signals is the lack of definitive arrivals of seismic phases such as P or S. The second is the predominant band of instantaneous frequencies between 0.5 and 5 Hz. We also determined locations by Source-Scanning Algorithm (SSA) without clear arrivals of P or S. We also set up the LMDF Automatic Monitoring System, built with the regional broadband seismograph network, and issued a LMDF report in 2 and a haf seconds. We hope that this system can save a lot of LMDF victims.

Natural Hazards are a risk to buried gas pipeline infrastructure, but these risks are difficult to assess and quantify. This can often lead to the risks not being properly identified by pipeline owners. The risk to pipelines within landslide areas are particularly difficult to assess given the complex nature of landslide movements and the soil-pipeline interaction mechanisms imposing loads on a pipeline. This thesis research examines the relationship between ground movements and strains/stresses in buried pipelines through field measured ground movements and in-situ measured pipe strains/stresses. The pipe stresses and strains are then used to estimate probability of pipeline failure and risk based on RBDA limit states approaches. Within Manitoba Hydro’s pipeline network, three at-risk landslide areas (riverbank and deep river valleys) were selected for detailed studies. A field investigation and monitoring program was undertaken to assess possible sources of load and stresses on pipelines. Soil, ground, and pipe instrumentation were installed at the sites and monitored over a four year period. Monitoring results identified soil near the pipeline does not freeze, and ground movements at valley sites are slow moving (<50 mm/year) landslides. The monitoring results also showed pipe stresses and behaviour were affected by backfilling, changes in river levels, thermal affects, soil-pipe relaxation, and ground movements. Pipe push tests were conducted in conjunction with FEM modelling to examine pipe adhesion and to possible explain the pipe behaviour observed. Several ultimate and serviceability limit states pipe failure modes were assessed using the measured pipe stresses. Statistical analysis was undertaken to calculate the probability of pipeline failure for the various limit states failure modes and compared against limit states targets for several scenarios (backfill loads, initial stress-state of the pipeline, other pipelines within Manitoba Hydro network). Overall, the probability of failure estimates were generally insignificant or low due to a postulated soil-pipe relaxation mechanism which is causing a repeated release in longitudinal pipe stresses as the landslide continues to accumulate ongoing ground movements. Three mechanisms are presented and discussed. The statistical analysis indicate pipelines within Manitoba Hydro’s network may exceed limit states targets for yielding and local buckling depending on the loading scenario and the class of the pipeline within the landslide area. The outcome of the research was used to develop a risk managements system to examine geotechnical hazards within Manitoba Hydro’s pipeline network. Specifically, risks associated with ground movements along natural slopes and at river crossings are examined within the system.
October 2016