Добірка наукової літератури з теми "Geostructural survey"

Geostructural rock mass surveys and the collection of data related to discontinues provide the basis for the characterization of rock masses and the study of their stability conditions. This paper describes a multiscale approach that was carried out using both non-contact techniques and traditional support techniques to survey certain geometrical features of discontinuities, such as their orientation, spacing, and useful persistence. This information is useful in identifying the possible kinematics and stability conditions. These techniques are extremely useful in the case study of the Elva valley road (Northern Italy), in which instability phenomena are spread across 9 km in an overhanging rocky mass. A multiscale approach was applied, obtaining digital surface models (DSMs) at three different scales: large-scale DSM of the entire road, a medium-scale DSM to assess portions of the slope, and a small-scale DSM to assess single discontinuities. The georeferenced point cloud and consequent DSMs of the slopes were obtained using an unmanned aerial vehicle (UAV) and terrestrial photogrammetric technique, allowing topographic and rapid traditional geostructural surveys. This technique allowed us to take measurements along the entire road, obtaining geometrical data for the discontinuities that are statistically representative of the rock mass and useful in defining the possible kinematic mechanisms and volumes of potentially detachable blocks. The main purpose of this study was to analyse how the geostructural features of a rock mass can affect the stability slope conditions at different scales in order to identify road sectors susceptible to different potential failure mechanisms using only kinematic analysis.

In mountainous areas around the world, dealing with rockfalls means facing some technical survey difficulties due to the low accessibility of areas and the height of slopes. If a cultural heritage is also threatened by such mass movement, the need of specific survey solutions, even in a combined asset, is required. This paper deals with the integration of ground and UAV rock mass surveys aimed at defining the rockfall attitude of an unstable rock cliff sector hosting an example of cultural heritage in tourist area of southern Italy, whose fruition has already been threatened by the occurrence of rockfalls. As an example of the defensive architecture of XII and XIII centuries, the Saracen Castle in Taormina is reached by hundreds of visitors each year, but its access path and the surrounding area are threatened by the unstable condition of the cliff, hosting unstable rock volumes on kinematically critical planes. In order to achieve a reliable geostructural setting of the cliff, aiming at its possible securing through proper mitigation works, ground rock mass surveys could not provide enough information due to the bad accessibility of the rock faces. Therefore, a survey by an Unmanned Aerial Vehicle, with a reliable verified accuracy, was carried out to map the discontinuity planes especially occurring at the highest portions of the cliff, achieving geostructural data of different fronts of the cliff. Ground and aerial data were combined and statistically analyzed to define the main kinematic failure patterns. In this perspective, a critical comparison between the two employed surveying methodologies is proposed herein, highlighting that both approaches are affected by potential and limitations and that the integration of the mutual dataset represents a suitable solution for a complete rock mass characterization in this type of areas. Furthermore, rockfall simulations allowed ascertaining that potential falling blocks would cross the access path to the castle, thus representing a natural threat to the fruition of cultural heritage, thus proving the need of mitigation measures to ensure the safe fruition of the cultural heritage.

The use of non-contact-techniques for rock mass characterization has been growing significantly over the last decade. However, their application to stability assessment of ornamental stone has not yet received much attention from researchers. This study utilizes rock mass data both in terms of slope orientations and degree of fracturing obtained from a point cloud, a set of three-dimensional (3D) points representing a rock mass surface, to (1) investigate the influence of geostructures at different scales and (2) assess quarry stability by determining areas susceptible to different failure types. Multi-resolution point clouds are obtained through several photogrammetric survey techniques to identify important structural elements of the site. By integrating orientation data of discontinuity planes, obtained with a traditional survey, and of traces, outlined on point clouds, several joint sets were identified. Kinematic tests revealed various potential failure modes of the rock slope. Moreover, an analysis of the influence of the discontinuity strength determined by the presence of rock bridges was carried out. The study revealed that the strength of the quarry face is governed by the presence of rock bridges that act to improve the stability condition of the rock fronts.

This study provides a detailed integrated analysis of the erosional processes affecting the volcanoclastic headlands of a pocket beach, of a typical Tyrrhenian volcanic island (Ventotene, south Italy). It compares the survey carried out in 2012 and the recent landslides that occurred in 2018–2020. The studied tuff cliff is characterised by steep, up to overhanging walls affected by a fracture network, which locally isolates blocks in precarious equilibrium. The stability conditions of the southern Cala Nave Bay sea cliff were evaluated by integrating a geological field survey, structural analysis of discontinuities, and a detailed topographic survey consisting of a terrestrial laser scanner (TLS) and photogrammetry data acquisition and processing, providing a three-dimensional (3D) model of the sea cliff. The 3D model of the area affected by the recent landslides was created using proximity photogrammetry, the Structure for Motion (SfM) methodology. The fracture network was represented by using high-resolution digital models and projected to realize geostructural vertical mapping of the cliff. The data acquired in 2012 were more recently compared with further surveys carried out, following rock failures that occurred in winter 2019–2020. The detachment planes and failure modalities coincide perfectly with the ones previously assessed. The applied techniques and the comparison with the recent rock failures have proven to be important in defining these conditions to address risk mitigation interventions.

The article describes the possibility of using the granulometric analysis of rock cuttings formed in controlled core scratching tests to estimate the angle of internal friction.The study object is the Kovykta gas-condensate field (GCF) that occupies a wide area in the southeastern part of the Irkutsk amphitheater of the Siberian platform. This uniquely complex geological structure holds significant reserves of hydrocarbons. Its sedimentary cover is composed of the Vendian – lower Paleozoic and partly Riphean formations. Their total thickness exceeds 6000 m, as estimated from the new seismic survey data [Vakhromeev et al., 2019].The sedimentary cover of the Kovykta GCF has been studied by surface and borehole geophysical techniques, remote sensing and geostructural methods, in combination with the tectonophysical approach [Seminsky et al., 2018] based on drilling data, including standard and special core sampling data.

This paper explored the relationship between acidic sulfate alteration, geostructural frameworks, and geomorphological changes that can be observed in active volcanic hydrothermal systems. The target area was Pisciarelli in the Campi Flegrei volcano, where diffuse acidic sulfate alteration and hydrothermal dynamics have been growing since 2012, causing a progressive deterioration of landscapes. Terrestrial Laser Scanner (TLS), photogrammetry of proximity survey, geological field work, mineralogical and geochemical analysis with Optical Microscopy (OM), electron microscopy, and energy dispersive micro-analysis (BSEM-EDS) and X-ray Powder Diffraction (XRPD) to characterize (and monitor) altered rock outcrops were repeatedly carried out in the area. We present the multi-temporal acquisition and analysis referring to Terrestrial Laser Scanning (TLS) datasets (2014 survey) with 3D-point clouds obtained from the Structure for Motion (SfM) photogrammetry (2021 survey) with a high-resolution digital camera aimed at evaluating volumetric changes on the mostly damaged and altered fault scarp. For each survey, we obtained a vertical Digital Elevation Model (DEM) and a true color RGB orthomosaic that provided the setting of the area at the different times and its evolution through their comparison. Changing sites were examined in the field and characterized for mineralogical and geochemical purposes. The investigated slope lost up to about 4 m3 of deposits between 2014 and 2021, mostly related to hydrothermal alteration induced by gas emissions and meteoric infiltration. Our methodological approach appears promising to evaluate evolution and rock-fall susceptibility of solfataric terrains subjected to hydrothermal dynamics.

Rock slope instabilities represent a major hazard for human activities, often causing economic losses, property damages and maintenance costs, as well as injuries or fatalities. Rock slope stability is so one of the most important issue in mountain areas and mines. Although, in fact, rock falls along highways and railways in mountainous terrains do not pose the same level of economic risk as large-scale failures (which can cause the closure of major transportation routes for several days), the number of people killed by rockfalls tends to be of the same order as people killed by all other instabilities affecting rock slopes. An accurate characterisation of the rock mass discontinuities allows to understand the most probable failure mechanism and individuate the source area, since the local orientation of the mesh of the 3D model of the slope. A proper geostructural survey, together with a high definition 3D model of the slope, allows, in fact, to evaluate the position of source area; the geostructural survey permits also the modelling of the volume distribution of the removable blocks. The position of the source area, the position of the blocks and the high definition 3D model of the slope are fundamental parameters for the modelling of the run out of the blocks, defining so the trajectory of the blocks and the associated kinetic energy for the design of the most appropriate protection works. The estimate of the blocks volume can be conducted by means of codes that use the structural features of the rock surface to identify the boundaries of the polygons that represent the blocks. An accurate geomechanical characterisation is therefore crucial to gather information about the most probable failure mechanism, the position of source area and the volume of removable blocks. Semiautomatic methods in addition to manual methods for discontinuities extraction, have allowed to reduce the user-dependant subjectivity and the consume of time over the last few decades, to obtain details of the rock mass structures. The thesis shows the application of different tools for the structural characterisation and the stability assessment on a number of different walls affected by rockfall in open pit mines in Australia. 3D models of walls have been built since close range photogrammetric surveys using Siro3D code (Datamine SiroVision). SiroJoint (in built in the Siro3D package) has been used to manually detect the discontinuities, while DiAna, Facets plug-in of CloudCompare and I-site Studio (Maptek) codes have been used for the semiautomatic discontinuities extraction. Stereoplots of the discontinuities extracted by manual and semiautomatic methods have been so compared and kinematic indices for plane failure, wedge failure, block toppling, and flexural toppling have been calculated. The structural survey has been then used to perform the distribution of the block volume thanks to a multi-function discrete fracture network (DFN) generator and to describe removability and stability of the blocks using the Block Theory (Goodman & Shi) and the Factor of Safety (Hoek & Bray). This stability analysis has been carried out with SiroModel software (developed by CSIRO within Large Open Pit-LOP project). 3D kinematic analysis has been then performed using DiAna-K code, since the semiautomatic geostructural survey carried out with DiAna and the high definition 3D model of the slope. DiAna and DiAna-K codes has been developed within the Department of earth Sciences of the University of Florence. The integration of the 3D kinematic analysis with the stability analysis of the blocks extracted with a DFN allows to objectively quantify since remote survey data the main geometric input parameters necessary for a complete and reliable rockfall hazard analysis, such as slope high resolution morphology, source areas and volume of unstable blocks, thanks to which is possible to calculate the kinetic energy along the run out. The study is aimed to: i) evaluate how artificial cuts affect the reliability of semiautomatic discontinuities extraction methods in comparison to manual discontinuities extraction methods; ii) compare stereoplots of semiautomatic and manual discontinuities extraction in case of artificial cuts; iii) integrate 3D kinematic analysis with the stability analysis of the blocks extracted with a multi-function discrete fracture network generator. The comparison of the stereoplots of the discontinuity planes produced with SiroJoint and DiAna shows results somehow comparable; moreover, this application revealed a number of interesting advantages and drawbacks of manual and semiautomatic methods, which can be useful to overcome some current limitations and improve the quality of the remote geostructural survey and then of the rockfall simulations. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------- La stabilità di versanti in roccia costituisce un tipo di frana che presenta un rischio elevato. Tale rischio è elevato in considerazione della probabilità che si abbiano vittime o feriti, dei tempi di interruzione dell’infrastruttura danneggiata e dei costi della sua messa in esercizio, oltre che di installazione dei più idonei sistemi di protezione. La caduta massi è infatti uno dei rischi maggiori in aree montane, così come anche in aree minerarie. Malgrado infatti i volumi di versate mobilizzati dai crolli siano in genere minori rispetto ai volumi dei corpi di frana di altri fenomeni di versante, l’elevata velocità del fenomeno fa sì che il numero di vittime avute a causa di caduta massi sia dello stesso ordine di altri fenomeni di versante. Un’attenta caratterizzazione delle discontinuità presenti all’interno dell’ammasso roccioso consente comprendere quali meccanismi cinematici siano più probabili ed individuare le possibili aree fonte dei distacchi. Pertanto, un corretto rilievo geostrutturale, insieme ad un modello 3D ad alta definizione del pendio, costituisce un dato di input essenziale per la corretta modellazione del run out dei massi in termini di percorsi e di energie cinetiche in gioco, permettendo quindi la progettazione delle contromisure di protezione più appropriate. Sono pertanto essenziali alcuni dati per la corretta modellazione 3D della rockfall analysis: un modello del terreno 3D di alta definizione (ricavato con rilievo fotogrammetrico o laser scanning), la posizione delle aree di distacco dei blocchi ed il volume dei blocchi instabili. Un accurato rilievo geostrutturale è alla base dell’individuazione dei meccanismi e quindi delle aree la cui esposizione risulta più favorevole all’innesco di caduta massi: un accurato rilievo geostrutturale è quindi alla base di una corretta valutazione del rischio caduta massi. Negli ultimi decenni ai metodi di rilevamento manuale delle discontinuità si sono aggiunti i metodi semiautomatici di estrazione delle discontinuità, che consentono di individuare le discontinuità a partire da parametri geometrici settati dall’operatore, riducendo molto la soggettività del rilievo ed il tempo necessario. Il rilievo geostrutturale consente quindi di calcolare gli indici di pericolosità cinematica e di avere la distribuzione del volume dei blocchi rimovibili. Gli indici di pericolosità cinematica consentono di attribuire un valore a ciascuno dei cinematismi posibili (scivolamento planare, civolamento di cunei, ribaltamento di blocchi, ribaltamento di flessure) in funzione dell’orientazione del versante; se si dispone di una mesh sarà quindi possibile capire quali porzioni siano più esposte al distacco di blocchi, in ragione della loro esposizione. Il rilievo geostrutturale consente inoltre di ricavare la distribuzione del volume dei blocchi mediante l’utilizzo di codici di calcolo che costruiscono una rete discreta di discontinuità all’interno dell’ammasso roccioso, mediante una modellazione di tipo stocastico. La tesi analizza e confronta l’applicazione di diversi codici per la caratterizzazione geostrutturale e per la successiva valutazione della stabilità di versante, su vari versanti in roccia situati in miniere di tipo open-pit in Australia. I modelli 3D dei versanti in roccia sono stati ricavati tramite fotogrammetria con il software Siro3D (Datamine SiroVision). Il codice SiroJoint (Siro3D package) è stato utilizzato per il rilievo manuale delle discontinuità, mentre per il rilievo semiautomatico delle discontinuità sono stati utilizzati i codici DiAna, Facets (CloudCompare) e I-Site Studio (Maptek). Sono stati quindi ricavati e gli stereoplots delle discontinuità estratte con metodi manuali e automatici e sono stati calcolati e confrontati gli indici di pericolosità cinematica per ciascun cinematismo. Il rilievo strutturale effettuato è stato utilizzato per ricavare tramite un generatore multifunzione di un sistema di fratture continue (discrete fracture network, DFN) all’interno del software SiroModel (sviluppato da CSIRO all’interno del progetto LRGE Open Pit mines – OPS), che ha consentito a partire dalla Teoria di Goodman e Shi sulla rimovibilità dei blocchi e dal calcolo del Fattore di Sicurezza (Factor of Safety; Hoek & Bray, 1981) di comprendere la distribuzione del volume dei blocchi instabili, stabili grazie all’attrito e stabili (Type I, II e III della classificazione dei blocchi di Goodman & Shi). I blocchi sono stati estratti mediante una modellazione stocastica a partire dall’orientazione e dalla persistenza delle discontinuità. L’analisi cinematica 3D è stata condotta tramite DiAna-K, usando come dati di il rilievo semiautomatico delle discontinuità ed il modello 3D del terreno ottenuto con tecnica fotogrammetrica. I codici DiAna e DiAna-K sono stati sviluppati dal Dipartimento di Scienze della Terra dell’Università di Firenze. L'integrazione dell’analisi cinematica 3D e dell’analisi di stabilità finalizzata alla definizione del volume dei blocchi rimovibili permette una definizione quantitativa ed oggettiva dei principali dati geometrici necessari per la modellazione del rischio di caduta massi, consentendo quindi di definire le traiettorie, la velocità e l’energia cinetica dei blocchi per una corretta progettazione degli interventi di mitigazione del rischio. Lo studio è stato finalizzato a: i) Valutare come la presenza di tagli artificiali influenzi l’applicabilità di metodi semiautomatici per l’estrazione delle discontinuità, rispetto a metodi manuali; ii) Confrontare gli stereoplot e gli indici di pericolosità cinematica dei rilievi geostrutturali effettuati con metodi manuali o con metodi semiautomatici di estrazione delle discontinuità; iii) Integrare l’analisi cinematica 3D con l’analisi di stabilità dei blocchi estratti grazie a DFN.