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Sai, Kolluru Venkata, V. V. N. Prabhakara Rao i V. Mallikarjuna. "A Review on the Utilisation of Silica Fume and Metakaolin as Novel Grout Materials". IOP Conference Series: Earth and Environmental Science 1130, nr 1 (1.01.2023): 012009. http://dx.doi.org/10.1088/1755-1315/1130/1/012009.
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Abstract One of the approaches for solving challenges related to foundations, open cut excavations, landslides, rock slopes, fractured rocks and tunnelling is enhancement of soil via grouting. Two main components of soil enhancement are reduced permeability and increase in strength. To overcome reduced strength and permeability in soils and rock fissures, it has always depended on cement and lime treatment. To replace cement and lime, chemical and ultra-fine cementitious grouts are often employed to break through highly fissured rocks or fine sands. This document gives a censorious evaluation of chosen studies that used unconventional cementitious grouts in order to assist practicing engineers and promote best practice. In sand and cohesive soils, sodium silicate, colloidal silica, metakaolin, silica fume, fly ash, resins, polymers, and microfine substitutes were evaluated as grouting material. The intent of the article is to procure effective data for consultants and contractors who will be building injection works that use non-cementitious fluids in the future.
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Cacace, Mauro, i Antoine B. Jacquey. "Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks". Solid Earth 8, nr 5 (13.09.2017): 921–41. http://dx.doi.org/10.5194/se-8-921-2017.
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Abstract. Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture–solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton–Raphson or by free Jacobian inexact Newton–Krylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).
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Bruckert, Sylvain, i Malika Bekkary. "Formation des horizons diagnostiques argiliques et de fragipan en fonction de la permeabilité des roches". Canadian Journal of Soil Science 72, nr 1 (1.02.1992): 69–88. http://dx.doi.org/10.4141/cjss92-007.
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Leached soils (Alfisols) with either an argillic horizon or a fragipan were encountered close to each other on the marly-limestone and sandstone plateaus of Haute–Saône (France). Soils have formed under periglacial conditions during the Riss in a similar climatic environment. Because the soils occurring today are in the same geomorphic and topographic position, the objectives of the investigations were to study the influence of other pedogenic factors, such as parent materials and underlying rock type. The soil mantle, above the bedrock, is from one and a half to several meters thick. Four types of materials were identified through the pedons studied: sands, clays, clay-loams, loams. Their location being directly above either a rhetian sandstone or a sinemurian marly-limestone, sandy or clayey materials were accumulated as insoluble residue of the underlying rocks. Related to particle size distribution and mineralogy, the clay loamy materials were identified as eolian dusts. The loamy materials were also eolian deposits, but they were reworked and transported with sandy particles from sandstone of other high landscape positions. The surficial materials, encountered in all the sites studied, were texturally and mineralogically similar, which suggested that the parent materials were not the main factor controlling the formation of argillic horizons or fragipans. On the other hand, the effect of rock type has been established. Our data suggest: (1) significant relationships between the internal drainage of soil and the underlying geological substrata (type, joints and fracture planes, permeability, effect on hydrology), (2) rock effect on formation of an argillic or a fragipan horizon. In the case where meteoric waters can move through fractured rocks, soils can undergo drying and wetting cycles and clays swell and shrink. These processes induce favorable effects on genesis of soil structure, particularly of Bt structure. In the case of low-porosity and low-permeability rocks, soils dry from the surface downward and dessication cycles accomplish a vertical cleavage and polygonal cracking. We have concluded that the rock effect is a major factor involved in the development of leached soils with an argillic horizon or a fragipan. A major advantage of the rock factor hypothesis is that the formation of fragipans is possible in periglacial areas and far from glaciated regions, as proposed by the literature. Key words: Fragipans, argillic horizon, pedogenetic factors, rock effect, Alfisols
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Xia, Lu, i Qingchun Yu. "Numerical Investigations of Blockiness of Fractured Rocks Based on Fracture Spacing and Disc Diameter". International Journal of Geomechanics 20, nr 3 (marzec 2020): 04020004. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0001596.
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Rodríguez-Robles, Ulises, Tulio Arredondo, Elisabeth Huber-Sannwald, José Alfredo Ramos-Leal i Enrico A. Yépez. "Technical note: Application of geophysical tools for tree root studies in forest ecosystems in complex soils". Biogeosciences 14, nr 23 (30.11.2017): 5343–57. http://dx.doi.org/10.5194/bg-14-5343-2017.
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Abstract. While semiarid forests frequently colonize rocky substrates, knowledge is scarce on how roots garner resources in these extreme habitats. The Sierra San Miguelito Volcanic Complex in central Mexico exhibits shallow soils and impermeable rhyolitic-rock outcrops, which impede water movement and root placement beyond the soil matrix. However, rock fractures, exfoliated rocks and soil pockets potentially permit downward water percolation and root growth. With ground-penetrating radar (GPR) and electrical resistivity tomography (ERT), two geophysical methods advocated by Jayawickreme et al. (2014) to advance root ecology, we advanced in the method development studying root and water distribution in shallow rocky soils and rock fractures in a semiarid forest. We calibrated geophysical images with in situ root measurements, and then extrapolated root distribution over larger areas. Using GPR shielded antennas, we identified both fine and coarse pine and oak roots from 0.6 to 7.5 cm diameter at different depths into either soil or rock fractures. We also detected, trees anchoring their trunks using coarse roots underneath rock outcroppings. With ERT, we tracked monthly changes in humidity at the soil–bedrock interface, which clearly explained spatial root distribution of both tree species. Geophysical methods have enormous potential in elucidating root ecology. More interdisciplinary research could advance our understanding in belowground ecological niche functions and their role in forest ecohydrology and productivity.
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Masciopinto, Costantino, i Maria Clementina Caputo. "Modeling Unsaturated-Saturated Flow and Nickel Transport in Fractured Rocks". Vadose Zone Journal 10, nr 3 (sierpień 2011): 1045–57. http://dx.doi.org/10.2136/vzj2010.0087.
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Sun, Long, Lei Yang, Liding Chen, Fangkai Zhao i Shoujuan Li. "Short-term changing patterns of stem water isotopes in shallow soils underlain by fractured bedrock". Hydrology Research 50, nr 2 (10.10.2018): 577–88. http://dx.doi.org/10.2166/nh.2018.086.
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Abstract Knowledge is limited on the changes in tree water uptake over short timescales in shallow soils underlain by fractured rocks under humid climate conditions. This study explored the changing patterns of tree water uptake at two forests (camphor) and two orchards (peach and tea) over multi-day timescales. We collected water isotopic samples (δD and δ18O) from rainfall, spring, tree branch, soil and fissure between two rain events (8-day duration). The trees in the forest lands exhibited a larger variability in stem water isotopic composition than the trees in the orchards. Significantly different changing patterns of stem water isotopic composition were found between the orchards and the forest lands. On average, the fissure contributed most of the tree water uptake (46.1 ± 20.8%) compared to the soil layer (33.9 ± 17.7%) and shallow groundwater (20.0 ± 13.5%). Main water sources for the trees in this study shifted at a daily timescale. Compared to orchards, forest trees had a relatively large range of source water and a good water use strategy in the shallow soil–rock profile under humid climate conditions. This study emphasizes the importance of characterization of the changing patterns of stem water isotopic composition over short timescales.
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Pan, L., Y. S. Wu i K. Zhang. "A Modeling Study of Flow Diversion and Focusing in Unsaturated Fractured Rocks". Vadose Zone Journal 3, nr 1 (1.02.2004): 233–46. http://dx.doi.org/10.2113/3.1.233.
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Pan, Lehua, Yu-Shu Wu i Keni Zhang. "A Modeling Study of Flow Diversion and Focusing in Unsaturated Fractured Rocks". Vadose Zone Journal 3, nr 1 (2004): 233. http://dx.doi.org/10.2136/vzj2004.0233.
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Pan, Lehua, Yu-Shu Wu i Keni Zhang. "A Modeling Study of Flow Diversion and Focusing in Unsaturated Fractured Rocks". Vadose Zone Journal 3, nr 1 (luty 2004): 233–46. http://dx.doi.org/10.2136/vzj2004.2330.
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Zhang, Xiaobo, Huihui Chen, Chi Yao, Jianhua Yang, Shuihua Jiang, Qinghui Jiang i Chuangbing Zhou. "Seepage Characteristics of Triaxial Compression-Induced Fractured Rocks under Varying Confining Pressures". International Journal of Geomechanics 20, nr 9 (wrzesień 2020): 04020160. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0001796.
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Lai, Jin, Dong Li, Yong Ai, Hongkun Liu, Deyang Cai, Kangjun Chen, Yuqiang Xie i Guiwen Wang. "Structural diagenesis in ultra-deep tight sandstones in the Kuqa Depression, Tarim Basin, China". Solid Earth 13, nr 6 (21.06.2022): 975–1002. http://dx.doi.org/10.5194/se-13-975-2022.
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Abstract. The Lower Cretaceous Bashijiqike Formation of the Kuqa Depression is made up of ultra-deeply buried sandstones in fold-and-thrust belts. Few researches have linked diagenetic processes with structure. To fill this gap, a comprehensive analysis integrating diagenesis with structure pattern, fracture and in situ stress is performed following a structural diagenetic approach. The results show that the pore spaces include residual intergranular pores, intergranular and intragranular dissolution pores, and micro-fractures. The sandstones experienced a high degree of mechanical compaction, but compaction is limited in well-sorted rocks or abundant in rigid quartz grains. The most volumetrically important diagenetic minerals are calcites. The framework grains experienced a varied degree of dissolution, and intergranular and intragranular dissolution pores are formed. Special attention is paid on the dissolution associated with the fracture planes. Large numbers of natural fractures are cemented by carbonate cements, which limit fluid flow. In addition, the presence of fracture enhances dissolution and the fracture planes are enlarged by dissolution. Cementation and dissolution can occur simultaneously in fracture surfaces, and the enlarged fracture surfaces can be cemented by late-stage cements. The in situ stress magnitudes are calculated using well logs. The horizontal stress difference (Δσ) determines the degree of mechanical compaction, and rocks associated with low Δσ experienced a low degree of compaction, and these contain preserved intergranular pores. Natural fractures are mainly related to the low Δσ layers. The presence of intergranular and intragranular dissolution pores is mainly associated with the fractured zones. The high-quality reservoirs with intergranular pores or fractures are related to low Δσ layers. The structural diagenesis researches above help the prediction of reservoir quality in ultra-deep sandstones and reduce the uncertainty in deep natural gas exploration in the Kuqa Depression.
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Guo, Liang, Xiewen Hu, Lizhou Wu, Xiaozhao Li i Hongsheng Ma. "Simulation of Fluid Flow in Fractured Rocks Based on the Discrete Fracture Network Model Optimized by Measured Information". International Journal of Geomechanics 18, nr 10 (październik 2018): 05018008. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0001270.
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Villeneuve, Marlène C. "Challenges of Tunnelling in Volcanic Rock Masses". BHM Berg- und Hüttenmännische Monatshefte 166, nr 12 (30.11.2021): 612–17. http://dx.doi.org/10.1007/s00501-021-01175-2.
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AbstractVolcanic rock masses exhibit temporal and spatial variability, even at the scale and duration of engineering projects. Volcanic processes are dynamic, resulting in rock masses ranging from high-porosity, clay-rich, fractured, and soil-like to low-porosity, high-strength, brittle, and massive. Based on a number of studies in a variety of geological settings, such as active and fossil geothermal systems, on the surface of active volcanoes and up to 3000 m below the surface, the work presented in this article shows the relationship between geological characteristics and mechanical parameters of volcanic rocks. These are then linked to the resultant challenges to tunnelling associated with the mechanical behaviour of volcanic rocks and rock masses, ranging from ductile failure such as squeezing and swelling to dynamic failure such as spalling and rockburst.This article highlights some of the key parameters that should be incorporated in site and laboratory investigations to build representative ground models in volcanic rocks and rock masses. Rock mass characterisation needs to address the highly variable and anisotropic nature of volcanic rocks, ranging from millimetre to decametre scale. Ground models must include not only the mechanical properties, such as strength and stiffness, of typical lab investigations, but also petrophysical properties, such as porosity, and geological conditions, such as alteration. Geomechanical characterisation of these rock masses requires an understanding of geological processes to select appropriate field, lab and design tools. In volcanic rocks, perhaps more than any other rock types, the geology is critical to characterising and understanding the behaviour in response to tunnelling.
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Ezung, Meripeni, Temsulemba Walling i C. Chelladura C. Chelladura. "Application of Vertical Electrical Sounding for Subsurface Characterization to Determineslope Instability at Perizie, Nagaland". Current World Environment 17, nr 3 (30.12.2022): 657–71. http://dx.doi.org/10.12944/cwe.17.3.14.
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Vertical Electrical Sounding (VES) technique which employs the Schlumberger depth sounding method was used to investigate the subsurface conditions at the landslide in Perizie colony, Kohima. The interpretation of the VES curves shows differing lithology consisting of weathered shales with associated clay, which is considered an important factor for slope instability. The shear strength of the slope materials, including the country rocks and the soil cover, is also significantly reduced and easily detached due to the effects of weathering and erosion, causing the landslides. Three to six possible geo-electric layers are delineated from the variations in the resistivity values, with the lithologies consisting of topsoil followed by alternate layers of weathered and fractured rocks of varying thickness. The analysis also points to the presence of a weak zone at a depth of about 10 m, which is not apparent from the surface. The formation of groundwater aquifers in the fractured zones indicates high risk for slope failure as this accelerates the weak country rocks to weather. The results obtained by this study correspond well with the available borehole data of the area.
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Corona, Roberto, i Nicola Montaldo. "On the transpiration of wild olives under water-limited conditions in a heterogeneous ecosystem with shallow soil over fractured rock". Journal of Hydrology and Hydromechanics 68, nr 4 (1.12.2020): 338–50. http://dx.doi.org/10.2478/johh-2020-0022.
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AbstractMediterranean ecosystems are typically heterogeneous and savanna-like, with trees and grass competing for water use. By measuring sap flow, we estimated high transpiration of wild olive, a common Mediterranean tree, in Sardinia despite dry conditions. This estimate agrees with independent estimates of tree transpiration based on energy balance, highlighting the wild olive’s strong tolerance of dry conditions. The wild olive can develop an adaptation strategy to tolerate dry conditions. In this Sardinian case study, the wild olive grew in shallow soil, and the tree roots expanded into the underlying fractured basalt. The trees survived in dry periods using water infiltrated during wet seasons into fractured rocks and held in soil pockets. We estimated a high upward vertical flux through the bottom soil layer from the underlying substrate, which reached 97% evapotranspiration in August 2011. The water taken up by tree roots from bedrock hollows is usually neglected in ecohydrological modeling.
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Frazer, L. Neil. "Dynamic elasticity of microbedded and fractured rocks". Journal of Geophysical Research 95, B4 (1990): 4821. http://dx.doi.org/10.1029/jb095ib04p04821.
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Norbury, D. R., G. H. Child i T. W. Spink. "A Critical Review of Section 8 (BS 5930)—Soil and Rock Description". Geological Society, London, Engineering Geology Special Publications 2, nr 1 (1986): 331–42. http://dx.doi.org/10.1144/gsl.1986.002.01.57.
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AbstractBS 5930 proposes fundamental changes to current practice in the description of soils and rocks. The paper reviews these changes and suggests alternative proposals which provide a workable reconciliation between the aims of the new Code and current practical soil and rock description. The main changes made by the Code and the authors' recommendations are:The distinction between fine soil and coarse soil solely on grading is rejected in favour of description according to engineering behaviour.The distinction between silt and clay solely on the basis of the A-line is supplemented with additional terms for borderline cases.Simplification and extension of terminology for description of secondary constituents of mixed soils.Rejection of proposed weathering classification for rocks as inapplicable, in favour of current practice.Clarification of rock nomenclature to conform with geological conventions.The changes to current practice made by BS 5930 are considered to be a retrograde step and could lead to confusion and errors. The paper also considers the process of sample description and attempts to clarify the definition of terms employed in fracture logging of rock core.The paper calls for a revision and reissue of Section 8 of the new Code.
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Grab, Melchior, Beatriz Quintal, Eva Caspari, Hansruedi Maurer i Stewart Greenhalgh. "Numerical modeling of fluid effects on seismic properties of fractured magmatic geothermal reservoirs". Solid Earth 8, nr 1 (24.02.2017): 255–79. http://dx.doi.org/10.5194/se-8-255-2017.
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Abstract. Seismic investigations of geothermal reservoirs over the last 20 years have sought to interpret the resulting tomograms and reflection images in terms of the degree of reservoir fracturing and fluid content. Since the former provides the pathways and the latter acts as the medium for transporting geothermal energy, such information is needed to evaluate the quality of the reservoir. In conventional rock physics-based interpretations, this hydro-mechanical information is approximated from seismic velocities computed at the low-frequency (field-based) and high-frequency (lab-based) limits. In this paper, we demonstrate how seismic properties of fluid-filled, fractured reservoirs can be modeled over the full frequency spectrum using a numerical simulation technique which has become popular in recent years. This technique is based on Biot's theory of poroelasticity and enables the modeling of the seismic velocity dispersion and the frequency dependent seismic attenuation due to wave-induced fluid flow. These properties are sensitive to key parameters such as the hydraulic permeability of fractures as well as the compressibility and viscosity of the pore fluids. Applying the poroelastic modeling technique to the specific case of a magmatic geothermal system under stress due to the weight of the overlying rocks requires careful parameterization of the model. This includes consideration of the diversity of rock types occurring in the magmatic system and examination of the confining-pressure dependency of each input parameter. After the evaluation of all input parameters, we use our modeling technique to determine the seismic attenuation factors and phase velocities of a rock containing a complex interconnected fracture network, whose geometry is based on a fractured geothermal reservoir in Iceland. Our results indicate that in a magmatic geothermal reservoir the overall seismic velocity structure mainly reflects the lithological heterogeneity of the system, whereas indicators for reservoir permeability and fluid content are deducible from the magnitude of seismic attenuation and the critical frequency at which the peak of attenuation and maximum velocity dispersion occur. The study demonstrates how numerical modeling provides a valuable tool to overcome interpretation ambiguity and to gain a better understanding of the hydrology of geothermal systems, which are embedded in a highly heterogeneous host medium.
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Bolshov, Leonid, Peter Kondratenko, Leonid Matveev i Karsten Pruess. "Elements of Fractal Generalization of Dual-Porosity Model for Solute Transport in Unsaturated Fractured Rocks". Vadose Zone Journal 7, nr 4 (listopad 2008): 1198–206. http://dx.doi.org/10.2136/vzj2007.0151.
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Lu, Zhiming, i Edward M. Kwicklis. "Numerical Evaluation of Effective Unsaturated Hydraulic Properties of Fractured Rocks using a Stochastic Continuum Approach". Vadose Zone Journal 11, nr 4 (listopad 2012): vzj2011.0164. http://dx.doi.org/10.2136/vzj2011.0164.
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Grinchar, N. G., A. S. Shohin i M. Yu Chalova. "Application of modern drilling machines in transport construction". Nauchno-tekhnicheskiy vestnik Bryanskogo gosudarstvennogo universiteta 6, nr 4 (25.12.2020): 477–85. http://dx.doi.org/10.22281/2413-9920-2020-06-04-477-485.
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The broad scale of the plan for the development of the Far North, Siberia, provides for the annual development of hundreds of millions of cubic meters of permafrost soils and rocks, most of which require the use of drilling and blasting operations. The most time consuming process of preparing rocks for excavation is the creation of wells. Drilling of permafrost soils, soils with rock inclusions, monolithic and fractured rocks requires careful analysis and detailed calculations for each type of rock. It should also be borne in mind that the harsh climatic conditions of work in the Far North, open mining fields, also imply a significant distance from any settlements, therefore, based on the above factors, special attention should be paid to investigate the problems of mobility and reliability of tractor drilling rigs. This article discusses the use of modern drilling machines, provides a comparison of a tractor drilling rig with a mechanical drive of a drill string with a machine with a hydraulic drive, lists the factors confirming the feasibility of using a hydraulic drive of a drilling string, examines the results of tests of drilling various rocks, as well as the effect of rock structure on vibrations pressure and increase in the flow rate of hydraulic fluid in the drive system of the machine.
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Ayub, Syahrial, Muhammad Zuhdi i Joni Rokhmat. "Aplikasi Metode Seismik Refraksi dalam Menentukan Lapisan dan Tingkat Kekerasan Batuan di Bawah Permukaan Desa Medana Lombok Utara". Kappa Journal 4, nr 2 (30.12.2020): 188–96. http://dx.doi.org/10.29408/kpj.v4i2.2607.
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The seismic refraction method is one of the geophysical methods which is based on measuring the response of seismic waves in the soil that are fractured along the soil and rock layers. One of the seismic refraction method application is to determine the layers and rocks types below the surface. This study uses a geophone as a catcher for seismic waves that are emitted below the surface. The waves caught on the geophone are converted into seismic data which can be read in a seismograph. Seismic data read by seismographs are already in digital form and stored in the central unit PASI 16S24-P. The results of the data analysis concluded that below the land surface of the village of Medana, there were 3 rock layers with a thickness of the first layer 3-4 meters, the second layer 2-5 meters and the third layer 10-17 meters. The first and second layers are still in the form of soil (less compact), while the third layer is in the form of rock (compact). The level of hardness (density) will be more compact in linear to the depth, the more the depth will be the more compact the rock. The depth in the form of hard rock starts from 16 meters to 23 meters from the ground level of the village of Medana, Central Lombok.
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Prabhakaran, Rahul, Pierre-Olivier Bruna, Giovanni Bertotti i David Smeulders. "An automated fracture trace detection technique using the complex shearlet transform". Solid Earth 10, nr 6 (20.12.2019): 2137–66. http://dx.doi.org/10.5194/se-10-2137-2019.
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Abstract. Representing fractures explicitly using a discrete fracture network (DFN) approach is often necessary to model the complex physics that govern thermo-hydro-mechanical–chemical processes (THMC) in porous media. DFNs find applications in modelling geothermal heat recovery, hydrocarbon exploitation, and groundwater flow. It is advantageous to construct DFNs from the photogrammetry of fractured outcrop analogues as the DFNs would capture realistic, fracture network properties. Recent advances in drone photogrammetry have greatly simplified the process of acquiring outcrop images, and there is a remarkable increase in the volume of image data that can be routinely generated. However, manually digitizing fracture traces is time-consuming and inevitably subject to interpreter bias. Additionally, variations in interpretation style can result in different fracture network geometries, which, may then influence modelling results depending on the use case of the fracture study. In this paper, an automated fracture trace detection technique is introduced. The method consists of ridge detection using the complex shearlet transform coupled with post-processing algorithms that threshold, skeletonize, and vectorize fracture traces. The technique is applied to the task of automatic trace extraction at varying scales of rock discontinuities, ranging from 100 to 102 m. We present automatic trace extraction results from three different fractured outcrop settings. The results indicate that the automated approach enables the extraction of fracture patterns at a volume beyond what is manually feasible. Comparative analysis of automatically extracted results with manual interpretations demonstrates that the method can eliminate the subjectivity that is typically associated with manual interpretation. The proposed method augments the process of characterizing rock fractures from outcrops.
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Mitskovets, Ivan A. "Application of Chimeric Meshes for Explicit Accounting for Inhomogeneities in Modeling the Propagation of Elastic Waves". Radioelectronics. Nanosystems. Information Technologies. 15, nr 2 (29.06.2023): 185–92. http://dx.doi.org/10.17725/rensit.2023.15.185.
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The method of chimeric meshes is applied to simulate the propagation of elastic perturbations in media containing porous and fractured inclusions. A model of a linearly elastic isotropic medium is considered, which describes the state of a geological rock. The grid-characteristic method with the third-order accurate Rusanov scheme is used for numerical modeling of the dynamic propagation of elastic disturbances. Special attention is paid to the presence of separate inclusions of pores or fractures, which introduce heterogeneity into the medium and can substantially influence the response of elastic disturbances. The use of the chimera grid method allows for both the position and shape of such inclusions to be described explicitly, taking into account their influence on the propagation of elastic disturbances. As a result of the conducted investigation, a methodology for numerical modeling of the propagation of elastic disturbances in media with porous and fractured inclusions was developed, which can be used to assess the influence of such inclusions on the dynamic response of elastic disturbances. The presented results can be applied in geophysical and seismic research related to modeling the dynamics of various processes in soils and rocks.
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Köppl, Tobias, Ettore Vidotto, Barbara Wohlmuth i Paolo Zunino. "Mathematical modeling, analysis and numerical approximation of second-order elliptic problems with inclusions". Mathematical Models and Methods in Applied Sciences 28, nr 05 (maj 2018): 953–78. http://dx.doi.org/10.1142/s0218202518500252.
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Many biological and geological systems can be modeled as porous media with small inclusions. Vascularized tissue, roots embedded in soil or fractured rocks are examples of such systems. In these applications, tissue, soil or rocks are considered to be porous media, while blood vessels, roots or fractures form small inclusions. To model flow processes in thin inclusions, one-dimensional (1D) models of Darcy- or Poiseuille type have been used, whereas Darcy-equations of higher dimension have been considered for the flow processes within the porous matrix. A coupling between flow in the porous matrix and the inclusions can be achieved by setting suitable source terms for the corresponding models, where the source term of the higher-dimensional model is concentrated on the center lines of the inclusions. In this paper, we investigate an alternative coupling scheme. Here, the source term lives on the boundary of the inclusions. By doing so, we lift the dimension by one and thus increase the regularity of the solution. We show that this model can be derived from a full-dimensional model and the occurring modeling errors are estimated. Furthermore, we prove the well-posedness of the variational formulation and discuss the convergence behavior of standard finite element methods with respect to this model. Our theoretical results are confirmed by numerical tests. Finally, we demonstrate how the new coupling concept can be used to simulate stationary flow through a capillary network embedded in a biological tissue.
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Araújo Pedron, Fabrício de, Jessé Rodrigo Fink, Miriam Fernanda Rodrigues i Antonio Carlos de Azevedo. "Hydraulic conductivity and water retention in leptosols-regosols and saprolite derived from sandstone, Brazil". Revista Brasileira de Ciência do Solo 35, nr 4 (sierpień 2011): 1253–62. http://dx.doi.org/10.1590/s0100-06832011000400018.
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Leptosols and Regosols are soils with a series of restrictions for use, mainly related to the effective depth, which have been poorly studied in Brazil. These soils, when derived from sedimentary rocks should be treated with particular care to avoid environmental damage such as aquifer contamination. The purpose of this study was to verify the behavior of hydraulic conductivity and water retention capacity in profiles of Leptosols and Regosols derived from sandstone of the Caturrita formation in Rio Grande do Sul state. The morphology, particle size distribution, porosity, soil density (Ds), saturated hydraulic conductivity (Ks), basic water infiltration in the field (BI) and water retention were determined in soil and saprolite samples of six soil profiles. High Ds, low macroporosity and high microporosity were observed in the profiles, resulting in a low Ks and BI, even under conditions of sandy texture and a highly fractured saprolite layer. The variation coefficients of data of Ks and BI were high among the studied profiles and between replications of a same profile. Water retention of the studied soils was higher in Cr layers than in the A horizons and the volume of plant-available water greater and variable among A horizons and Cr layers.
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Rasmussen, T. C., i D. D. Evans. "Water Infiltration into Exposed Fractured Rock Surfaces". Soil Science Society of America Journal 57, nr 2 (marzec 1993): 324–29. http://dx.doi.org/10.2136/sssaj1993.03615995005700020006x.
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Gomez-Rivas, E., A. Griera i M. G. Llorens. "Fracturing of ductile anisotropic multilayers: influence of material strength". Solid Earth 6, nr 2 (19.05.2015): 497–514. http://dx.doi.org/10.5194/se-6-497-2015.
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Abstract. Fractures in rocks deformed under dominant ductile conditions typically form simultaneously with viscous flow. Material strength plays a fundamental role during fracture development in such systems, since fracture propagation can be strongly reduced if the material accommodates most of the deformation by viscous flow. Additionally, the degree and nature of anisotropy can influence the orientation and type of resulting fractures. In this study, four plasticine multilayer models have been deformed under coaxial boundary conditions to investigate the influence of strength and anisotropy on the formation of fracture networks. The experiments were made of different mixtures and had two types of anisotropy: composite and composite-intrinsic. The transition from non-localised deformation to systems where fracture networks control deformation accommodation is determined by the ability of the material to dissipate the external work and relax the elastic strain during loading either by viscous flow or by coeval flow and failure. Tension cracks grow in experiments with composite anisotropy, giving rise to a network of shear fractures when they collapse and coalesce with progressive deformation. The presence of an additional intrinsic anisotropy enhances the direct nucleation of shear fractures, the propagation and final length of which depend on the rigidity of the medium. Material strength increases the fracture maximum displacement (dmax) to fracture length (L) ratio, and the resulting values are significantly higher than those from fractures in elastic–brittle rocks. This can be related to the low propagation rates of fractures in rocks undergoing ductile deformation.
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Sulaiman, N., N. A. Ariffin, M. S. Sulaiman, N. Sulaiman i R. M. Jamil. "Groundwater exploration using Electrical Resistivity Imaging (ERI) at Kemahang, Tanah Merah, Kelantan". IOP Conference Series: Earth and Environmental Science 1102, nr 1 (1.11.2022): 012027. http://dx.doi.org/10.1088/1755-1315/1102/1/012027.
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The electrical resistivity imaging (ERI) method was conducted at Kemahang, Tanah Merah, Kelantan. This study intends to explore the potential for groundwater resources in the study area. The greatest way for locating groundwater is ERI, a technique that doesn’t alter the composition or functionality of the soil. ERI survey is concerned with the resistivity (Ωm) value of subsurface rocks. The Pole-Dipole array was used for this study, and a total of two survey lines were used. Each survey line was 200 m long, with 2.5 m between electrodes. ABEM Terrameter LS Toolbox is used to record all the data, and RES2DINV software is used to process it. All the data are processed in two-dimensional (2D) resistivity profiles will give a better understanding of the geological environment and enable the detection of groundwater. The findings indicate fluctuating resistivity with a range of 1-4000 Ωm and an inquiry depth of roughly 45 m. High resistivity zones of 4000 Ωm indicate values for granitic rock, whereas low resistivity zones of 10-800 Ωm reveal values for the area’s fractured aquifer, which is viewed as a potential water carrying zone (bedrock). Bedrock is found to be around 50 m below the indicated fractured aquifer layer, which is located at a depth of about 25 m. By measuring the depth of the fractured zone for probable zones with low resistivity values, this study provides an idea of the potential groundwater resources.
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Birkholzer, Jens T., i Yingqi Zhang. "The Impact of Fracture-Matrix Interaction on Thermal-Hydrological Conditions in Heated Fractured Rock". Vadose Zone Journal 5, nr 2 (maj 2006): 657–72. http://dx.doi.org/10.2136/vzj2005.0071.
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Bingchao, Zhao, Yang Leilei, He Weizhong, Li Hui i Wang Guirong. "Development of the fracture zone water flow level in the overburden". Water Practice and Technology 14, nr 2 (26.03.2019): 399–408. http://dx.doi.org/10.2166/wpt.2019.024.
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Abstract The Guojiahe coalmine was studied to estimate the maximum water level in the fractured zone in the overburden of a thick seam in Linyou mining area, where extraction is fully-mechanized. Using a predictive model of the movement and deformation of the upper rock/soil layer in the overburden fracture zone, the free water level in the overburden was determined. Physical and numerical simulations were performed to study the development characteristics of water-flow in the fractured zone under different conditions, and the maximum water level in the fracture zone was determined. The maximum height of the fracture zone is 185 ∼ 193 m from the roof of the coal seam, and the relationship between it and the distance to the working face has a step-like function, revealing the controlling effects on water level of the key strata in the overburden.
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Celico, Fulvio, Mario Varcamonti, Marco Guida i Gino Naclerio. "Influence of Precipitation and Soil on Transport of Fecal Enterococci in Fractured Limestone Aquifers". Applied and Environmental Microbiology 70, nr 5 (maj 2004): 2843–47. http://dx.doi.org/10.1128/aem.70.5.2843-2847.2004.
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ABSTRACT Limestone aquifers provide the main drinking water resources of southern Italy. The groundwater is often contaminated by fecal bacteria because of the interaction between rocks having high permeability and microbial pollutants introduced into the environment by grazing and/or manure spreading. The microbial contamination of springwater in picnic areas located in high mountains can cause gastrointestinal illness. This study was carried out in order to analyze the interaction between Enterococcus faecalis and the soil of a limestone aquifer and to verify the influence of this interaction on the time dependence of groundwater contamination. E. faecalis was chosen because, in the study area involved, it represents a better indicator than Escherichia coli. The research was carried out through field (springwater monitoring) and laboratory experiments (column tests with intact soil blocks). The transport of bacterial cells through soil samples was analyzed by simulating an infiltration event that was monitored in the study area. Comparison of laboratory results with data acquired in the field showed that discontinuous precipitation caused an intermittent migration of microorganisms through the soil and produced, together with dispersion in the fractured medium (unsaturated and saturated zones), an articulated breakthrough at the spring. The short distances of bacterial transport in the study area produced a significant daily variability of bacterial contamination at the field scale.
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Xiang, Yanyong, i Yong Zhang. "Two-Dimensional Integral Equation Solution of Advective-Conductive Heat Transfer in Sparsely Fractured Water-Saturated Rocks with Heat Source". International Journal of Geomechanics 12, nr 2 (kwiecień 2012): 168–75. http://dx.doi.org/10.1061/(asce)gm.1943-5622.0000109.
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Salve, Rohit, i Daniella Rempe. "Backfill Impacts on Moisture Measurements in Fractured Rock". Vadose Zone Journal 12, nr 4 (listopad 2013): vzj2013.04.0076. http://dx.doi.org/10.2136/vzj2013.04.0076.
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Bruna, Pierre-Olivier, Julien Straubhaar, Rahul Prabhakaran, Giovanni Bertotti, Kevin Bisdom, Grégoire Mariethoz i Marco Meda. "A new methodology to train fracture network simulation using multiple-point statistics". Solid Earth 10, nr 2 (17.04.2019): 537–59. http://dx.doi.org/10.5194/se-10-537-2019.
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Abstract. Natural fracture network characteristics can be establishes from high-resolution outcrop images acquired from drone and photogrammetry. Such images might also be good analogues of subsurface naturally fractured reservoirs and can be used to make predictions of the fracture geometry and efficiency at depth. However, even when supplementing fractured reservoir models with outcrop data, gaps will remain in the model and fracture network extrapolation methods are required. In this paper we used fracture networks interpreted from two outcrops from the Apodi area, Brazil, to present a revised and innovative method of fracture network geometry prediction using the multiple-point statistics (MPS) method. The MPS method presented in this article uses a series of small synthetic training images (TIs) representing the geological variability of fracture parameters observed locally in the field. The TIs contain the statistical characteristics of the network (i.e. orientation, spacing, length/height and topology) and allow for the representation of a complex arrangement of fracture networks. These images are flexible, as they can be simply sketched by the user. We proposed to simultaneously use a set of training images in specific elementary zones of the Apodi outcrops in order to best replicate the non-stationarity of the reference network. A sensitivity analysis was conducted to emphasise the influence of the conditioning data, the simulation parameters and the training images used. Fracture density computations were performed on selected realisations and compared to the reference outcrop fracture interpretation to qualitatively evaluate the accuracy of our simulations. The method proposed here is adaptable in terms of training images and probability maps to ensure that the geological complexity in the simulation process is accounted for. It can be used on any type of rock containing natural fractures in any kind of tectonic context. This workflow can also be applied to the subsurface to predict the fracture arrangement and fluid flow efficiency in water, geothermal or hydrocarbon fractured reservoirs.
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Mahi, Shuaibu, Abubakar Yusuf i Garba Lawal. "Geoelectrical Assessment of Groundwater Potential within Zamfara and its Environs, Northwestern Nigeria". Caliphate Journal of Science and Technology 4, nr 1 (10.02.2022): 54–70. http://dx.doi.org/10.4314/cajost.v4i1.8.
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Groundwater potential assessment was carried out within Zamfara environs, Northwestern Nigeria using geoelectrical technique with a view of solving the problem of incessant failure of boreholes in the study area. A total of one hundred and eighty-three (183) vertical electrical soundings (VES) were used to identify potential groundwater bearing zones capable of sustaining economic development of the study area. Two hydrogeological units were investigated (basement rock units and sedimentary rock unit), using Omega resistivity meter Model No. 122, to measure and record the resistance of the subsurface by Schlumberger configuration. The data obtained were interpreted quantitatively and qualitatively using the partial curve matching and computer iteration techniques to generate the first order geoelectric parameters. Generally, the VES result from the basement rock units revealed, four geoelectric layers which correspond to lateritic top soil, weathered basement (clay), partially fractured layer/fractured layer and fresh basement. The weathered/fractured layer was identified as the water bearing layer, within the basement rock units of the study area. From geospatial analysis of both weathered thickness/fracture thickness layers, South and Northeastern part tends to be the most prospective area with the best hydrogeologic conditions for borehole siting within the basement rock units. Consequently, three geo-electric layers were delineated from VES result obtained from Gundumi formation, which correspond to sandy clayey top/gravelly sandy top soil, second layer are mostly silty-clay/compacted sandstone/sandy gravel layers, the third layer were majorly saturated sandstone in some instances silty clay. However, the aquiferous layer is saturated sandstone/sandy gravel layer. The Dar Zarrouk result revealed excellent groundwater potential within the Gundumi formation. The values of coefficient anisotropy obtained from Gundumi rock units range from 0.44 to 3.79, which implies moderate saturation of groundwater. This is an indication that the aquifers of the Gundumi formation is more promising and it can be tap for both domestic and agricultural uses.
Keywords: Vertical electrical sounding; Fractured layer; Saturated Sandstone; Basement rock units; Gundumi formation
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Cheng, Chaojie, Sina Hale, Harald Milsch i Philipp Blum. "Measuring hydraulic fracture apertures: a comparison of methods". Solid Earth 11, nr 6 (11.12.2020): 2411–23. http://dx.doi.org/10.5194/se-11-2411-2020.
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Abstract. Hydraulic fracture apertures predominantly control fluid transport in fractured rock masses. Hence, the objective of the current study is to investigate and compare three different laboratory-scale methods to determine hydraulic apertures in fractured (Fontainebleau and Flechtinger) sandstone samples with negligible matrix permeability. Direct measurements were performed by using a flow-through apparatus and a transient-airflow permeameter. In addition, a microscope camera permitted measuring the mechanical fracture apertures from which the corresponding hydraulic apertures were indirectly derived by applying various empirical correlations. Single fractures in the sample cores were generated artificially either by axial splitting or by a saw cut resulting in hydraulic apertures that ranged between 8 and 66 µm. Hydraulic apertures, accurately determined by the flow-through apparatus, are used to compare results obtained by the other methods. The transient-airflow permeameter delivers accurate values, particularly when repeated measurements along the full fracture width are performed. In this case, the derived mean hydraulic fracture apertures are in excellent quantitative agreement. When hydraulic apertures are calculated indirectly from optically determined mechanical apertures using empirical equations, they show larger variations that are difficult to compare with the flow-through-derived results. Variations in hydraulic apertures as observed between methods are almost certainly related to differences in sampled fracture volume. Overall, using direct flow-through measurements as a reference, this study demonstrates the applicability of portable methods to determine hydraulic fracture apertures at both the laboratory and outcrop scales.
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Prabhakaran, Rahul, Giovanni Bertotti, Janos Urai i David Smeulders. "Investigating spatial heterogeneity within fracture networks using hierarchical clustering and graph distance metrics". Solid Earth 12, nr 10 (30.09.2021): 2159–209. http://dx.doi.org/10.5194/se-12-2159-2021.
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Abstract. Rock fractures organize as networks, exhibiting natural variation in their spatial arrangements. Therefore, identifying, quantifying, and comparing variations in spatial arrangements within network geometries are of interest when explicit fracture representations or discrete fracture network models are chosen to capture the influence of fractures on bulk rock behaviour. Treating fracture networks as spatial graphs, we introduce a novel approach to quantify spatial variation. The method combines graph similarity measures with hierarchical clustering and is applied to investigate the spatial variation within large-scale 2-D fracture networks digitized from the well-known Lilstock limestone pavements, Bristol Channel, UK. We consider three large, fractured regions, comprising nearly 300 000 fractures spread over 14 200 m2 from the Lilstock pavements. Using a moving-window sampling approach, we first subsample the large networks into subgraphs. Four graph similarity measures – fingerprint distance, D-measure, Network Laplacian spectral descriptor (NetLSD), and portrait divergence – that encapsulate topological relationships and geometry of fracture networks are then used to compute pair-wise subgraph distances serving as input for the statistical hierarchical clustering technique. In the form of hierarchical dendrograms and derived spatial variation maps, the results indicate spatial autocorrelation with localized spatial clusters that gradually vary over distances of tens of metres with visually discernable and quantifiable boundaries. Fractures within the identified clusters exhibit differences in fracture orientations and topology. The comparison of graph similarity-derived clusters with fracture persistence measures indicates an intra-network spatial variation that is not immediately obvious from the ubiquitous fracture intensity and density maps. The proposed method provides a quantitative way to identify spatial variations in fracture networks, guiding stochastic and geostatistical approaches to fracture network modelling.
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Keefer, David K., Raymond C. Wilson, Edwin L. Harp i Elliott W. Lips. "The Borah Peak, Idaho Earthquake of October 28, 1983—Landslides". Earthquake Spectra 2, nr 1 (listopad 1985): 91–125. http://dx.doi.org/10.1193/1.1585304.
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The Borah Peak, Idaho earthquake caused several hundred landslides throughout an area of about 4,200 km2. The most numerous landslides were rock falls and rock slides, which occurred where slopes contained conspicuous, through-going, open fractures or were composed of weakly cemented rocks. The earthquake also produced several slumps and cracks in man-made fill, several soil liquefaction phenomena, a large debris flow, a large mud flow, and a few ground failures of other types. The most significant landslide damage was in Challis, where rock falls damaged at least 3 houses and 2 automobiles.
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Abe, Steffen, i Hagen Deckert. "Roughness of fracture surfaces in numerical models and laboratory experiments". Solid Earth 12, nr 10 (27.10.2021): 2407–24. http://dx.doi.org/10.5194/se-12-2407-2021.
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Abstract. We investigate the influence of stress conditions during fracture formation on the geometry and roughness of fracture surfaces. Rough fracture surfaces have been generated in numerical simulations of triaxial deformation experiments using the discrete element method and in a small number of laboratory experiments on limestone and sandstone samples. Digital surface models of the rock samples fractured in the laboratory experiments were produced using high-resolution photogrammetry. The roughness of the surfaces was analyzed in terms of absolute roughness measures such as an estimated joint roughness coefficient (JRC) and in terms of its scaling properties. The results show that all analyzed surfaces are self-affine but with different Hurst exponents between the numerical models and the real rock samples. Results from numerical simulations using a wide range of stress conditions to generate the fracture surfaces show a weak decrease of the Hurst exponents with increasing confining stress and a larger absolute roughness for transversely isotropic stress conditions compared to true triaxial conditions. Other than that, our results suggest that stress conditions have little influence on the surface roughness of newly formed fractures.
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Tseng, P. H. "Flow and Transport Through Unsaturated Fractured Rock--Second Edition." Vadose Zone Journal 1, nr 1 (1.08.2002): 201. http://dx.doi.org/10.2113/1.1.201.
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Tseng, Peng-Hsiang. "Flow and Transport Through Unsaturated Fractured Rock—Second Edition." Vadose Zone Journal 1, nr 1 (2002): 201. http://dx.doi.org/10.2136/vzj2002.0201.
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Tseng, Peng-Hsiang. "Flow and Transport Through Unsaturated Fractured Rock-Second Edition." Vadose Zone Journal 1, nr 1 (sierpień 2002): 201. http://dx.doi.org/10.2136/vzj2002.2010.
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Thorne, G. A., J. Laporte i D. Clarke. "The Effects of Frozen Soils on Groundwater Recharge and Discharge in Granitic Rock Terrane of the Canadian Shield". Hydrology Research 29, nr 4-5 (1.08.1998): 371–84. http://dx.doi.org/10.2166/nh.1998.0028.
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Hydrologic measurements on groundwater flow systems of the Canadian Shield during the winter period provide insight into groundwater dynamics and can support conclusions based on measurements of the more “active” spring-to-fall, open-water period. To illustrate this, we present the results of detailed and continuous year-round measurements of parameters such as groundwater levels, air/soil temperatures, soil heat flux and soil moisture content which were made in upland recharge and wetland discharge areas of a local groundwater flow system in granitic terrane of the Canadian Shield. Recharge to the groundwater flow system in the rocks of the study area occurs as rain or snowmelt waters infiltrate exposed vertical and/or sub-horizontal soil-infilled fractures in outcrops of the upland area. During winter, soils in the fractures of the recharge area do not normally freeze below 0.5 m depth and shallow (5-20 cm depth) soil temperatures are most often only 1-2°C below freezing. During the spring melt period the temperature of these frozen soils remains near 0°C for several weeks as the pore ice absorbs thermal energy necessary for the phase transition from ice to water. However, despite these soils being completely or partially frozen, infiltration and recharge to the groundwater flow system in the rock occurs as shown by large and rapid rises in watertable and piezometric levels. In the groundwater discharge area of this flow system, near-surface soil temperatures (5 cm depth) reached minimums of about -12°C during the 1996 winter and freezing soils extended downward to more than 75 cm depth. During the spring melt period, as meltwaters add heat to the substrate, these shallow soil temperatures also, rise to near 0°C and remain frozen for several weeks as latent heat of fusion of ice becomes a factor. However, during the spring melt period, while ice covers ithe surface and soils are still frozen in the discharge area, groundwater level rises are recorded in both the overburden and bedrock of the discharge area. This is attributed to hydraulic pressure being rapidly transmitted to the discharge area through the low storativity groundwater flow system in the rock from the large waterlevel increases occurring in the rock of the adjacent upland recharge area.
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Konstantopoulou, G., i I. Vacondios. "Engineering geological map of the urban area of Kastoria, NW Greece". Bulletin of the Geological Society of Greece 40, nr 4 (1.01.2007): 1664. http://dx.doi.org/10.12681/bgsg.17070.
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In the present work, the engineering geological conditions of the urban area of Kastoria were examined. More specifically a geotechnical assessment of subsoil and rock outcrops within a minimum depth of 20 m bellow surface is made, for urban planning purposes. Landslide potential of the studied area including mainly rock falls and ground subsidence was also evaluated. Eleven engineering geological units were identified and mapped at 1:5.000 scale, which constitute the foundation ground of the old Kastoria town, as well as of its new areas of built-up extension. The identified ground units consist of six soil and five rock types. Soil units comprise one fill formation of variable composition and consistency with a ranging thickness between 2 m and 6 m and five loose to cohesive deposits, Holocene to Upper Pliocene in age, with high variation in grain size, density and plasticity factors. Rock lithologies range from highly to moderately weathered, closely fractured serpentinites and schists to fresh, widely fractured limestones. The old city of Kastoria is founded mainly on stable rocky ground and does not show any remarkable geotechnical problems. However, the need of built-up extension however and improvement of infrastructures, led to configurations of the marshy areas and to the use of foundation ground with poor mechanical properties, which locally need a special treatment to become stable.
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Detournay, E. "Propagation Regimes of Fluid-Driven Fractures in Impermeable Rocks". International Journal of Geomechanics 4, nr 1 (marzec 2004): 35–45. http://dx.doi.org/10.1061/(asce)1532-3641(2004)4:1(35).
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Güler, Cüneyt, Geoffrey D. Thyne, Hidayet Tağa i Ümit Yıldırım. "Processes Governing Alkaline Groundwater Chemistry within a Fractured Rock (Ophiolitic Mélange) Aquifer Underlying a Seasonally Inhabited Headwater Area in the Aladağlar Range (Adana, Turkey)". Geofluids 2017 (2017): 1–21. http://dx.doi.org/10.1155/2017/3153924.
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The aim of this study was to investigate natural and anthropogenic processes governing the chemical composition of alkaline groundwater within a fractured rock (ophiolitic mélange) aquifer underlying a seasonally inhabited headwater area in the Aladağlar Range (Adana, Turkey). In this aquifer, spatiotemporal patterns of groundwater flow and chemistry were investigated during dry (October 2011) and wet (May 2012) seasons utilizing 25 shallow hand-dug wells. In addition, representative samples of snow, rock, and soil were collected and analyzed to constrain the PHREEQC inverse geochemical models used for simulating water-rock interaction (WRI) processes. Hydrochemistry of the aquifer shows a strong interseasonal variability where Mg–HCO3 and Mg–Ca–HCO3 water types are prevalent, reflecting the influence of ophiolitic and carbonate rocks on local groundwater chemistry. R-mode factor analysis of hydrochemical data hints at geochemical processes taking place in the groundwater system, that is, WRI involving Ca- and Si-bearing phases; WRI involving amorphous oxyhydroxides and clay minerals; WRI involving Mg-bearing phases; and atmospheric/anthropogenic inputs. Results from the PHREEQC modeling suggested that hydrogeochemical evolution is governed by weathering of primary minerals (calcite, chrysotile, forsterite, and chromite), precipitation of secondary minerals (dolomite, quartz, clinochlore, and Fe/Cr oxides), atmospheric/anthropogenic inputs (halite), and seasonal dilution from recharge.
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Ghimire, Motilal, i Niroj Timalsina. "Assessment of denudation rate and erosion susceptibility in the upper Tamakoshi basin in the higher Himalayas, Nepal". Geographical Journal of Nepal 14 (10.03.2021): 41–80. http://dx.doi.org/10.3126/gjn.v14i0.35548.
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The higher rate of slope erosion in the Himalayan basins is contributing to rapid change in landform in the mountainous terrain, which has caused sedimentation, and inundation downstream. The Tamakoshi basin is a trans-boundary river that originates from Tibet and flows through Dolakha and Ramechap districts before joining the Sapta Koshi river. Few studies exist in Nepal attempting to quantify the erosion rate and susceptibility. However, they are scattered and mainly focus on either rill-sheet erosion or landslide only. Hence, this study attempted to estimate slope erosion by applying the Revised Universal Soil Loss Equation (RUSLE), and soil and debris erosion from landslide (2000-2019). Spatially distributed erosion intensity maps derived from the RUSLE model, as well as index-based landslide susceptibility map, were integrated to capture both running water and gravity erosion processes. The novelty of this research is that it examined the soil erosion rate using a process-based model as well as from the soil or rock displaced by the observed landslides over the last 20 years. The study estimated gross annual erosion by running water of 9.1million tons/yr, equivalent to the denudation rate of 3.34 mm/yr. Of these, landslide erosion accounts for 7.6 million ton/yr, i.e., 2.88 mm/yr, this covers about 84% of total slope erosion. High landslide and erosion potential areas are associated with high rainfall, steep slopes, scarps, lower segment of valley side slopes, high relief, and highly fractured and deformed parts of high-grade metamorphic rocks, such as gneiss, quartzite, marbles, migmatite, and granitic gneiss.
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Benoît, Jean, i John A. Howie. "A View of Pressuremeter Testing in North America". Soils and Rocks 37, nr 3 (1.09.2014): 211–31. http://dx.doi.org/10.28927/sr.373211.
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The pressuremeter was introduced to North America by Ménard in 1957. It consists of a cylindrical probe which is inserted into the ground in a borehole, by self-boring or by pushing, and is expanded against the soil or rock to obtain a pressure-expansion curve. Interpretation methods based on cavity expansion theory applied to realistic models of soil behavior allow derivation of in situ lateral stress, stiffness, strength and volume change characteristics of the material being tested. Since its introduction, the pressuremeter test (PMT) has been a popular topic of research but has not gained wide acceptance in geotechnical engineering site characterization practice which, in North America, is still dominated by the Standard Penetration Test (SPT) and more recently by the piezocone (CPTu). Over the same period, the PMT has become the dominant tool for site investigation and foundation design in France. There, the PMT is used empirically based on a very large amount of load testing and experience. This paper examines the use of the PMT in North American practice, discusses its strengths and weaknesses, identifies trends in its use for site characterization and geotechnical design and identifies possible reasons for its lack of adoption by industry. We conclude that the PMT is not competitive with other techniques such as the CPTu and SPT for general site characterization where such tests are possible but that the PMT offers great potential to provide geotechnical design parameters in problematic materials such as hard, very dense or gravelly soils, residual, saprolitic or lateritic soils, soft and fractured rocks, frozen ground and ice. The PMT also has application in all soils where high consequences of failure require very detailed analysis and design. We also emphasize the need for improvements in the education of geotechnical practitioners on the use of the pressuremeter.