Academic literature on the topic 'Fractured Slope'
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Journal articles on the topic "Fractured Slope"
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Jia, Lin, Jingsen Cai, Li Wu, Tiange Qin, and Kun Song. "Influence of Fracture Geometric Characteristics on Fractured Rock Slope Stability." Applied Sciences 13, no. 1 (December 24, 2022): 236. http://dx.doi.org/10.3390/app13010236.
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Analysis of the stability of slopes in fractured rock masses is not trivial and is fraught with uncertainty and risk. A DFN-DEC model (Discrete Fracture Network-Distinct Element Code) based on the MATLAB platform is developed to evaluate the stability of rock slopes with random fractures. Then, the influences of mean values of geometric characteristics (i.e., the trace length T, the dip D, and the spacing S) for both the horizontal (denoted with 1) and inclined (denoted with 2) fractures on the mean slope stability are investigated. The results indicate that the proposed DFN-DEC model based on the MATLAB platform is adequate, robust, and can generate more realistic fracture networks. By means of probabilistic analysis (i.e., Monte Carlo simulation), we can obtain a more accurate stability assessment result of fractured rock slopes. In addition, it is found that the μFs (the mean of Fs) of slopes decreases with the increase in μT1, μT2 (the mean trace length of horizontal and inclined fractures, respectively) and μD1 (the mean dip of horizontal fractures), and increases gradually with the increase in μD2 (the mean dip of inclined fractures), μS1 and μS2 (the mean spacing of horizontal and inclined fractures, respectively). Furthermore, the geometric characteristics related to inclined fractures have a much greater influence on μFS than that related to horizontal fractures. This study can be well applied in engineering practice, e.g., preliminary evaluation of the slope stability according to the statistics of fracture geometric characteristics.
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Zhang, Wen, Jia Wang, Peihua Xu, Junqing Lou, Bo Shan, Fengyan Wang, Chen Cao, Xiaoxue Chen, and Jinsheng Que. "Stability evaluation and potential failure process of rock slopes characterized by non-persistent fractures." Natural Hazards and Earth System Sciences 20, no. 11 (November 5, 2020): 2921–35. http://dx.doi.org/10.5194/nhess-20-2921-2020.
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Abstract. Slope failure, which causes destructive damage and fatalities, is extremely common in mountainous areas. Therefore, the stability and potential failure of slopes must be analysed accurately. For most fractured rock slopes, the complexity and random distribution of structural fractures make the aforementioned analyses considerably challenging for engineers and geologists worldwide. This study aims to solve this problem by proposing a comprehensive approach that combines the discrete fracture network (DFN) modelling technique, the synthetic rock mass (SRM) approach, and statistical analysis. Specifically, a real fractured rock slope in Laohuding Quarry in Jixian County, China, is studied to show this comprehensive approach. DFN simulation is performed to generate non-persistent fractures in the cross section of the slope. Subsequently, the SRM approach is applied to simulate the slope model using 2D particle flow code software (PFC2D). A stability analysis is carried out based on the improved gravity increase method, emphasizing the effect of stress concentration throughout the formation of the critical slip surface. The collapse, rotation, and fragmentation of blocks and the accumulation distances are evaluated in the potential failure process of the rock slope. A total of 100 slope models generated with different DFN models are used to repeat the aforementioned analyses as a result of a high degree of variability in DFN simulation. The critical slip surface, factor of safety, and accumulation distance are selected by statistical analysis for safety assurance in slope analysis and support.
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Gao, Qin, and Gui He Wang. "Numerical Simulation of Fractured Rock Slope with Shear-Slip Behavior." Applied Mechanics and Materials 548-549 (April 2014): 673–77. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.673.
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The development of shear-slip cracks and motion trend of fracture water were presented for discussing the shear-slip behavior and analyzing the stability of fractured rock slope under hydraulic action. Seepage behavior of epigenetic cracks and the positions of slip or collapse were also investigated by monitoring pore water pressure using DEM. The analysis method of discrete element simulation for fractured rock slope was proposed. The results of numerical simulation indicated that interpenetrating fractures are more likely to be slip planes.
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Guo, Yun Hua, and Wei Shen Zhu. "A New Method to Determining the Strength Parameters of Fractured Rock Mass." Advanced Materials Research 898 (February 2014): 378–82. http://dx.doi.org/10.4028/www.scientific.net/amr.898.378.
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A Hydropower Station is located in the middle reach of the Dadu River in southwest China. The natural slope angles are generally 40°~65° and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. Many abutment slopes were formed during construction of the abutments. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the hydropower station. According to the statistical distribution of joints and fractures at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model which is close to the real state of the fractured rock mass are established by the Monte-Carlo method. The mechanical response of fractured rock masses with different sizes of numerical models is studied using FLAC3D. The REV characteristic scale is identified for rock masses in the slopes with stochastic fracture network. Numerical simulation is performed to obtain the stress-strain curve, the mechanical parameters and the strength of the jointed rock mass in the zone. A constitutive relationship reflecting the mechanical response of the jointed rock mass in the zone is established. The Comparison between the traditional method and the method in this paper has been made at the end.
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Liu, Xianshan, and Ming Xu. "The Unsaturated Hydromechanical Coupling Model of Rock Slope Considering Rainfall Infiltration Using DDA." Geofluids 2017 (2017): 1–15. http://dx.doi.org/10.1155/2017/1513421.
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Water flow and hydromechanical coupling process in fractured rocks is more different from that in general porous media because of heterogeneous spatial fractures and possible fracture-dominated flow; a saturated-unsaturated hydromechanical coupling model using a discontinuous deformation analysis (DDA) similar to FEM and DEM was employed to analyze water movement in saturated-unsaturated deformed rocks, in which the Van-Genuchten model differently treated the rock and fractures permeable properties to describe the constitutive relationships. The calibrating results for the dam foundation indicated the validation and feasibility of the proposed model and are also in good agreement with the calculations based on DEM still demonstrating its superiority. And then, the rainfall infiltration in a reservoir rock slope was detailedly investigated to describe the water pressure on the fault surface and inside the rocks, displacement, and stress distribution under hydromechanical coupling conditions and uncoupling conditions. It was observed that greater rainfall intensity and longer rainfall time resulted in lower stability of the rock slope, and larger difference was very obvious between the hydromechanical coupling condition and uncoupling condition, demonstrating that rainfall intensity, rainfall time, and hydromechanical coupling effect had great influence on the saturated-unsaturated water flow behavior and mechanical response of the fractured rock slopes.
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Theune, Ulrich, Dean Rokosh, Mauricio D. Sacchi, and Douglas R. Schmitt. "Mapping fractures with GPR: A case study from Turtle Mountain." GEOPHYSICS 71, no. 5 (September 2006): B139—B150. http://dx.doi.org/10.1190/1.2335515.
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Ground-penetrating radar (GPR) surveys were acquired of rocks on the highly fractured summit of Turtle Mountain in Canada. In 1903 a disastrous rock slide occurred at Turtle Mountain and it still poses a geologic hazard. Dips, shapes, and penetration depths of fractures are important parameters in slope-stability analysis. Determination of fracture orientation at Turtle Mountain has been based mostly on areal geologic mapping and, most recently, on data collected from boreholes. The purpose of GPR surveys was to test, confirm, and extend information about fractures and bedding planes. Data acquisition was complicated by the rough terrain; because slopes are steep and uneven. This also complicated analysis of the data. Measurement of in situ velocity — an important value for migration — was impossible. Instead, data were migrated with different velocities and data results were chosen that were considered to be reasonable. Analysis and interpretation of the data, resulted in confirmation and extension of the a priori information on orientations of fractures and bedding planes at Turtle Mountain. Despite the rough terrain and highly fractured rock mass, GPR surveys provide reliable information about the shapes and density of fractures — information important for slope-stability evaluation. The most reliable migration results obtained for velocities were considerably less than the standard velocities recorded for limestone, the dominant lithofacies at Turtle Mountain. We interpret this observation as an indicator of water within the rock. However, thorough investigation of this conclusion remains a project for future work.
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Ershaghi, I., and R. Aflaki. "Problems in Characterization of Naturally Fractured Reservoirs From Well Test Data." Society of Petroleum Engineers Journal 25, no. 03 (June 1, 1985): 445–50. http://dx.doi.org/10.2118/12014-pa.
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Abstract This paper presents a critical analysis of some recently published papers on naturally fractured reservoirs. These published papers on naturally fractured reservoirs. These publications have pointed out that for a publications have pointed out that for a matrix-to-fracture-gradient flow regime, the transition portion of pressure test data on the semilog plot develops a portion of pressure test data on the semilog plot develops a slope one half that of the late-time data. We show that systems under pseudosteady state also may develop a 1:2 slope ratio. Examples from published case studies are included to show the significant errors associated with the characterization of a naturally fractured system by using the 1:2 slope concept for semicomplete well tests. Introduction Idealistic models of the dual-porosity type often have been recommended for interpretation of a well test in naturally fractured reservoirs. The evolutionary aspects of these models have been reviewed by several authors. Gradual availability of actual field tests and recent developments in analytical and numerical solution techniques have helped to create a better understanding of application and limitation of various proposed models. Two important observations should be made here. First, just as it is now recognized that classical work published by Warren and Root in 1963 was not the end of the line for interpretation of the behavior of naturally fractured systems, the present state of knowledge later may be considered the beginning of the technology. Second, parallel with the ongoing work by various investigators who progressively include more realistic assumptions in their progressively include more realistic assumptions in their analytical modeling, one needs to ponder the implication of these findings and point out the inappropriate impressions that such publications may precipitate in the mind of practicing engineers. practicing engineers. This paper is intended to scrutinize statements published in recent years about certain aspects of the anticipated transition period developed on the semilog plot of pressure-drawdown or pressure-buildup test data. pressure-drawdown or pressure-buildup test data. The Transition Period In the dual-porosity models published to date, a naturally fractured reservoir is assumed to follow the behavior of low-permeability and high-storage matrix blocks in communication with a network of high-permeability and low-storage fractures. The difference among the models has been the assumed geometry of the matrix blocks or the nature of flow between the matrix and the fracture. However, in all cases, it is agreed that a transition period develops that is strictly a function of the matrix period develops that is strictly a function of the matrix properties and matrix-fracture relationship. Fig. 1 shows properties and matrix-fracture relationship. Fig. 1 shows a typical semilog plot depicting the transition period and the parallel lines. Estimation of Warren and Root's proposed and to characterize a naturally fractured proposed and to characterize a naturally fractured system requires the development of the transition period. The Warren and Root model assumes a set of uniformly distributed matrix blocks. Furthermore, the flow from matrix to fracture is assumed to follow a pseudosteady-state regime. Under such conditions, in theory, this period is an S-shaped curve with a point of inflection. Uldrich and Ershaghi developed a technique to use the coordinates of this point of inflection for estimating and under conditions where either the early- or the late-time straight lines were not available. Kazemi and de Swann presented alternative approaches to represent naturally fractured reservoirs. They assumed a geometrical configuration consisting of layered matrix blocks separated by horizontal fractures. Their observation was that for such a system the transition period develops as a straight line with no inflection point. Bourdet and Gringarten identified a semilog straight line during the transition period for unsteady-state matrix-fracture flow. Recent work by Streltsova and Serra et al emphasized the transient nature of flow from matrix to fracture and pointed out the development of a unique slope ratio. These authors, later joined by Cinco-L. and Samaniego-V., stated that under a transient flow condition, the straight-line shape of the transition period develops a slope that is numerically one-half the slope of the parallel straight lines corresponding to the early- or late-time data. It was further pointed out that the transient flow model is a more realistic method of describing the matrix-fracture flow. As such, they implied that in the absence of wellbore-storage-free early-time data, or late-time data in the case of limited-duration tests, one may use the slope of the transition straight line and proceed with the estimation of the reservoir properties. Statement of the Problem The major questions that need to be addressed at this time are as follows. SPEJ P. 445
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Weber, Samuel, Jan Beutel, Jérome Faillettaz, Andreas Hasler, Michael Krautblatter, and Andreas Vieli. "Quantifying irreversible movement in steep, fractured bedrock permafrost on Matterhorn (CH)." Cryosphere 11, no. 1 (February 16, 2017): 567–83. http://dx.doi.org/10.5194/tc-11-567-2017.
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Abstract. Understanding rock slope kinematics in steep, fractured bedrock permafrost is a challenging task. Recent laboratory studies have provided enhanced understanding of rock fatigue and fracturing in cold environments but were not successfully confirmed by field studies. This study presents a unique time series of fracture kinematics, rock temperatures and environmental conditions at 3500 m a. s. l. on the steep, strongly fractured Hörnligrat of the Matterhorn (Swiss Alps). Thanks to 8 years of continuous data, the longer-term evolution of fracture kinematics in permafrost can be analyzed with an unprecedented level of detail. Evidence for common trends in spatiotemporal pattern of fracture kinematics could be found: a partly reversible seasonal movement can be observed at all locations, with variable amplitudes. In the wider context of rock slope stability assessment, we propose separating reversible (elastic) components of fracture kinematics, caused by thermoelastic strains, from the irreversible (plastic) component due to other processes. A regression analysis between temperature and fracture displacement shows that all instrumented fractures exhibit reversible displacements that dominate fracture kinematics in winter. Furthermore, removing this reversible component from the observed displacement enables us to quantify the irreversible component. From this, a new metric – termed index of irreversibility – is proposed to quantify relative irreversibility of fracture kinematics. This new index can identify periods when fracture displacements are dominated by irreversible processes. For many sensors, irreversible enhanced fracture displacement is observed in summer and its initiation coincides with the onset of positive rock temperatures. This likely indicates thawing-related processes, such as meltwater percolation into fractures, as a forcing mechanism for irreversible displacements. For a few instrumented fractures, irreversible displacements were found at the onset of the freezing period, suggesting that cryogenic processes act as a driving factor through increasing ice pressure. The proposed analysis provides a tool for investigating and better understanding processes related to irreversible kinematics.
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Guo, Yun Hua, Wei Shen Zhu, Da Jun Yu, and Xin Ping Li. "Study of a High Slope Stability Considering the Stochastic Distribution of Rock Joint Set." Applied Mechanics and Materials 90-93 (September 2011): 786–90. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.786.
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A hydropower station is located in the middle reach of the Dadu River in southwest China. The natural slope angles at the project site are generally 40~65 and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the project. According to the statistical distribution of joints at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model are established by the Monte-Carlo method. The mechanical characters of fractured rock with different sizes are studied using FLAC3D. The REV characteristic scale is identified for rock masses. Numerical simulation is performed to obtain the mechanical parameters and the strength of the jointed rock. With the numerical model and the site monitoring data, a self-developed stochastic mechanical analysis software is applied for back analysis and stability assessment.
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Zhang, Tingting, Ruifeng Zhang, Jianzhang Tian, Lifei Lu, Fengqi Qin, Xianzeng Zhao, and Yuefeng Sun. "Two-parameter prestack seismic inversion of porosity and pore-structure parameter of fractured carbonate reservoirs: Part 2 — Applications." Interpretation 6, no. 4 (November 1, 2018): SM9—SM17. http://dx.doi.org/10.1190/int-2018-0019.1.
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Fractures and fracture-related dissolution pores, as well as cavities, molds, and vugs, provide the major conduit and/or storage space for hydrocarbons in the deeply buried carbonate hill of Hexiwu field, Bohai Bay Basin. The fractured reservoir generally has lower porosity but better permeability than moldic/vuggy reservoir, and it consists of the major part of the buried-hill slope and buried-hill internal reservoirs. The conventional method of characterizing carbonate reservoirs, however, often mixes these two types of reservoirs together because they both have low acoustic impedance and low bulk modulus. The rock-physics analysis of two field wells indicates that a pore-structure parameter defined in a rock-physics model, the so-called Sun model, can help to distinguish the fractured reservoir zones together with porosity. Fractured zones usually have porosity of less than 5% and a pore-structure parameter of greater than six, whereas moldic/vuggy reservoirs of higher porosity have a pore-structure parameter of less than six. Field-scale application demonstrates that simultaneous prestack seismic inversion for the porosity and pore-structure parameter enables 3D mapping of fractured reservoir zones in the buried carbonate hills. It also provides an analog of detecting fractures and/or fracture-related pores in deeply buried carbonates in similar geologic settings.
Dissertations / Theses on the topic "Fractured Slope"
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Spreafico, Margherita Cecilia <1984>. "Lateral spreading and associated slope processes in fractured rock slabs." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7180/.
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Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. These instability phenomena can become particularly risky, when historical towns and cultural heritage sites built on the top of them are endangered. Neverthless, the mechanisms controlling the developing of related instabilities, i.e. toppling and rock falls, at the edges of rock plateaux are not fully understood yet. In addition, the groundwater flow path developing at the contact between the more permeable units, i.e. the jointed rock slab, and the relatively impermeable clay-rich units have not been already studied in details, even if they may play a role in this kind of instability processes, acting as eventual predisposing and/or triggering factors. Field survey, Terrestrial Laser Scanner and Close Range Photogrammetry techniques, laboratory tests on the involved materials, hydrogeological monitoring and modelling, displacements evaluation and stability analysis through continuum and discontinuum numerical codes have been performed on the San Leo case study, with the aim to bring further insights for the understanding and the assessment of the slope processes taking place in this geological context.
The current research permitted to relate the aquifer behaviour of the rocky slab to slope instability processes. The aquifer hosted in the fractured slab leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clay-shales led to the progressive undermining of the slab. The cliff becomes progressively unstable due to undermining and undergoes large-scale landslides due to fall or topple.
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CAMONES, LUIS ARNALDO MEJIA. "MODELLING OF STEP-PATH TYPE FAILURE MECHANISMS IN FRACTURED ROCK SLOPE USING DISCRETE ELEMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33108@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Diferentes mecanismos de ruptura são considerados no momento de avaliar a estabilidade de um maciço rochoso fraturado. Entre estes, os mecanismos de ruptura tipo planar, em cunha e tombamentos têm sido estudados intensivamente, existindo atualmente modelos matemáticos que permitem avaliá-los. Estes mecanismos de ruptura são restritos a taludes pequenos e com fraturas contínuas, nas quais o deslizamento ocorre ao longo destas descontinuidades. Em casos de taludes de grande altura ou quando a persistência das fraturas é pequena em relação à escala do talude, o fraturamento torna-se descontínuo. Neste caso, o mecanismo de ruptura mais provável é o tipo Step-Path, o qual, a superfície de ruptura é formada por fraturas que se propagam através da rocha intacta juntando-se entre elas. Este fenômeno de união de fraturas é chamado de coalescência. Análises de estabilidade, como os probabilísticos ou por equilíbrio limite, são usados atualmente para avaliar estes tipos de rupturas, não se tendo ainda o desenvolvimento de um modelo numérico que possa representá-lo e reforçar estas teorias. O presente trabalho avalia o uso do Método dos Elementos Discretos na modelagem do mecanismo de ruptura tipo step- path, realizando uma análise de estabilidade que permita comparar os seus resultados com o método de equilíbrio limite. Foi utilizado o programa PFC nas versões 2D e 3D, assim como o programa FracGen para a geração de fraturas tridimensionais. A análise tridimensional foi feita mediante um acoplamento PFC3D-FracGen. A pesquisa inclui a análise e modelagem dos fenômenos de coalescência em amostras, assim como a influência da anisotropia na resistência das rochas em ensaios triaxiais.
Different failure mechanisms are considered when a fracturated rock mass is valued. Some of them are being subject of accurate study, like planar failure mechanism, wedges and toppling, which are currently valued by mathematical models. These failure mechanisms are restricted to small slopes and with continue fractures, where the sliding occurs along these discontinuities. To height slopes or when the fracture persistence is smaller than the slope scale, the fracturing becomes discontinuous. In this case, the most probable failure mechanism to happen is the step-path type, in which the failure surface is composed by fractures that propagate through the intact rock and that are joined together. This phenomenon of fracture union is known as coalescence. Stability analysis, like probability analysis or limit equilibrium analysis are currently utilized to evaluate this kind of failures, but its important to develop a numerical model to represent and reinforce these theories. This work aims to evaluate the use of Discrete Element Method to model step-path failure mechanism on a stability analysis and to compare the results with limit equilibrium method. The program used to simulate the slope is PFC (2D and 3D) and the program FracGen was used to generate three-dimensional fractures. Three-dimensional analysis was done by a coupling between PFC3D and FracGen. The research includes the analysis and modeling of coalescence phenomenon on rock samples, as well as the analysis of the anisotropy influence on rock strength obtained from triaxial tests.
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Hou, Xiaoping. "Composite element method for modelling transient groundwater flow in fractured media and its application to slope stability problem." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10051/document.
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Ce travail de thèse propose un modèle numérique complet pour l'écoulement transitoire des eaux souterraines dans les milieux poreux et fracturés et son application sur l’analyse de la stabilité des pentes sous l’effet d’une diminution du niveau de l’eau dans un réservoir. L’écouement de l’eau dans les milieux fracturés est complexe, en raison de la présence d'un grand nombre de fractures et de fortes variations dans les propriétés géométriques et hydrauliques de ces milieux.La thèse est organisée en six chapitres.Le premier chapitre pésente les problèmes abordés et les objectifs de la thèse. Le 2nd chapitre présente une synthèse des analyses numériques de l'écoulement dans les milieux fracturés et de ses effets sur la stabilité des pentes. Le 3ème chapitre présente le développment d’un modèle numérique d'écoulement transitoire saturé dans des milieux fracturés avec une surface libre en utilisant la méthode des éléments composites (CEM). Le 4ème chapitre présente un modèle numérique d'écoulement transitoire à saturation variable, dans les milieux fracturés à l'aide du CEM.Le 5ème chapitre présente une étude de la stabilité des pentes sous l’effet de variation des paramètres hydrauliques et de résistance des sols, et da géométrie des pentes.Le 6ème chapitre présente une étude paramétrique de l'influence des caractéristiques de fracture sur l'écoulement transitoire et la stabilité d’une pente soumise à des conditions de diminutionThis thesis presents a comprehensive numerical method for analyzing transient groundwater flow in porous and fractured media and its application to the analysis of the stability of soil and rock slopes subjected to transient groundwater flow induced by reservoir drawdown conditions. Compared to that of porous media, the analysis of flow in fractured media is relatively complex, due to the presence of a large number of fractures and strong variations in geometric and hydraulic properties.The thesis is organized in six chapters. Chapter 1 presents the issues to be addressed and the thesis objectives. Chapter 2 discusses basic theories related to the numerical analysis of groundwater flow in fractured media and its effects on slope stability.Chapter 3 develops the numerical model of transient, saturated flow in fractured media with a free surface using the composite element method (CEM). Chapter 4 presents the numerical model of transient, variably-saturated flow in fractured media using the CEM.Chapter 5 includes an investigation of the stability of homogeneous soil slopes under drawdown conditions, depending on the drawdown rate, hydraulic and strength parameters of soils, and slope geometry.The last chapter presents a parametric study on the influence of fracture characteristics on transient flow and stability of layered rock slope subjected to drawdown conditions
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Shaghaghi, Tahereh. "FEM and XFEM approaches to Investigate the Hydromechanical Interactions within a jointed soft-rock slope." Thesis, Federation University Australia, 2020. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/177426.
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One of the most significant challenges of open-cut mining is to provide stability for the excavated slopes. Unrealistic predictions of the slopes’ behaviour during and after mining operations can lead to the failure of slopes, and this may pose a threat to human lives, the economy, and the environment. By excavating soft rock masses in open-cut mines, pre-existing joints can open and new joints can form behind excavated slopes. This phenomenon is due to the geotechnical character of the materials and stress relief movements of the excavated slopes. The stability of slopes in the rock masses is significantly influenced by the existence of discontinuities such as joints. The water flows in the opened joints can change the pore water pressure distribution in the slopes. The interaction between the joints and the water may impose different loading scenarios on the open-cut mines and put the safety of mining operations at risk. The analysis of slope stability can become more complicated because of the presence of water, discontinuities, and their interaction within the slopes in open-cut mines. This study investigates the hydromechanical interactions in the saturated jointed slopes due to pore water pressure changes. The second-largest open-cut mine in Australia, the Yallourn brown coal open-cut mine located in Victoria, was chosen as the case study for this research. In this study, several coupled pore fluid diffusion and stress-strain analyses are conducted using the extended finite element method (XFEM) in conjunction with the finite element method (FEM). This study firstly examines a joint aperture and pore water pressure changes of the excavated jointed slope due to installing a drainage system and backfilling in front of the slope. Secondly, a series of sensitivity analyses are carried out on the pore water pressure distribution changes to the variation of the permeability magnitude of the material and leakage properties of the joint surfaces. Finally, to control the pore water pressure of the saturated jointed slope, a series of drainage systems is designed. The arrangement and length of the drains are optimised by conducting a series of sensitivity analyses on the leakage properties of the joint and the permeability of the soft rock.Doctor of Philosophy
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Styles, Thomas Daniel. "Numerical modelling and analysis of slope stability within fracture dominated rock masses." Thesis, University of Exeter, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496103.
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Numerical modelling of rock slopes can involve a number and variety of techniques, the selection and requirement of which depends on the factors deemed to control the potential for Instability. This thesis presents a number of case studies involving slopes in fractured rock, encompassing a range of scales. The case study slopes have provided a means to question the way in which particular slope instabilities should be analysed. Currently there are few methods available for analysing the complex behaviour within slopes of fractured rock. A review of available techniques is given within this thesis, with the use of limit equilibrium, finite element and hybrid methods, to highlight their specific advantages and limitations for the chosen case study slopes. By modelling slope Instability within fractured rock, the understanding of both discrete and mass behaviour increases considerably. Numerical modelling can therefore be used as a tool to help improve both the safety and efficiency of open pit mining and the management of natural rock slopes.
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Kim, Sihyun. "Shear band and landslide dynamics in submerged and subaerial slopes." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54245.
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Submarine landslides, commonly triggered by earthquakes, significantly affect tsunami wave heights. Subaerial landslides can also generate tsunamis (if the land flows into a body of water) and may be catastrophic in nature, causing human casualties and direct property damage. This work focuses on landslides associated with shear band that develops beneath the slipping mass. Accordingly, we consider a landslide as a dynamic process when a shear band emerges along the potential failure surface. Within this band, the shear strength decreases due to the softening behaviour of the particulate material. Material above the band moves downwards, causing the band to propagate dynamically. This already produces a landslide velocity before the slide reaches the post-failure stage and begins separating from the substrata and generating tsunami. However, existing models of tsunamigenic landslides assume zero initial slide velocity.
Previous analyses of the catastrophic shear band propagation in slopes of normally- and over-consolidated sediments have shown that a relatively short initial failure zone is sufficient to cause a full-scale landslide. For the shear band to propagate, the energy produced in the body by an incremental propagation of the shear band must exceed the energy required for the propagation. This consideration separates the shear band growth into progressive (stable) and catastrophic (dynamic) stages and treats the band growth as a true physical process rather than an instantaneously appearing discontinuity.
This work considers a dynamic shear band problem formulated within the framework of the Palmer and Rice’s [1973] approach. We obtain the exact, closed-form solution for the shear band and landslide velocities as well as for the spatial and temporal distributions of strain and material velocity. This solution assesses when the slide fails due to the limiting condition near the propagating tip of the shear band. We also obtain a simple asymptotic solution, which is compared to the exact solution. In the case of submerged slopes, the obtained solutions are used in landslide and tsunami height analyses.
Our results suggest that the conventional static approach to the slope stability analysis leads to a significant underestimation of the slide size (volume). In most cases, the volumes of catastrophic slides are roughly twice the volumes of progressive slides. For submerged slides, this dynamic effect further manifests itself in increasing the tsunami magnitude compared to the static case.
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Gwynn, Xander Peter. "Assessment of remote data capture systems for the characterisation of rock fracture networks within slopes." Thesis, University of Exeter, 2009. http://hdl.handle.net/10036/104498.
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The use of remote techniques to capture the geometrical characteristics of rock masses has seen increased use and development in recent years. Apart from the obvious improved Health and Safety aspects, remote techniques allow rapid collection of digital data that can be subsequently analysed to provide input parameters for a variety of geomechanical applications. Remote data capture is a new technique used to collect geotechnical data and little independent work has been done concerning the comparative limitations and benefits of photogrammetry and laser scanning. Photogrammetry and laser scanning produce three dimensional digital representations of a studied rock face which can then be mapped for geotechnical data using specialist software. Research conducted at Camborne School of Mines, University of Exeter has focussed on developing robust and flexible methodologies for remote data capture techniques, namely photogrammetry and laser scanning. Geotechnical characterisation for photogrammetry was tested using the CSIRO Sirovision software and laser scanning was used with SplitFX from Split Engineering. A comparative method of assessing the error between orientation measurements was developed based on calculating the pole vector difference between remotely captured and traditionally hand-mapped data. This allowed for testing of the benefits of the remote data capture systems and limitations whilst comparing them with conventional hand-mapping. The thesis also describes the results of detailed comparisons between hand-mapping, photogrammetric and laser scanned data collection for discontinuity orientation, roughness, discontinuity trace lengths and potential end-use applications. During fieldwork in Cornwall, Brighton Cliffs and northern France it was found that remote data capture techniques struggled to collect orientation data from intensely fractured rock masses where features are primarily represented as discontinuity traces. It was found that both photogrammetry and laser scanning produce orientation data comparable to traditionally mapped data, with an average pole vector difference less than 12° from data mapped from the Tremough Campus road cutting to the University of Exeter’s Cornwall Campus. Set analysis on 151 comparable data points yielded a maximum set pole vector difference of 9.8°, where the closest difference was 2.24°. Testing the accuracy of discontinuity trace orientations captured by photogrammetry using the pole vector difference methods indicate that planar derived orientations are more accurate, with an average difference of 16.67° compared to 37.72°. This thesis contains the reviews and analyses of photogrammetry and laser scanning for use in characterising natural and manmade rock slopes. Improved field and post-processing methodologies have been developed to aid the safe, efficient and suitable geotechnical characterisation of rock fracture networks. The continual development and use of remote mapping techniques, whilst supplementing their unique qualities with traditional mapping, have the capability to revolutionise rock mass mapping. Particular development needed is the implementation of ISRM guidelines to standardise photogrammetric and laser scanning fieldwork and post-processing data analysis.
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Paul, Anne. "Modélisation numérique des déformations d'un édifice volcanique : applications au Mont St Helens." Grenoble 1, 1986. http://www.theses.fr/1986GRE10006.
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La mesure des déplacements de surface liés â l'activité volcanique est une méthode très utilisée dans la surveillance et l'étude des volcans actifs. De nombreux modèles mécaniques ont été réalisés pour tenter de déduire la structure interne de ces données de déplacements, et notamment pour localiser les chambres magmatiques. Mais ils négligent tous le caractère fortement hétérogène et discontinu des édifices volcaniques. Un nouveau modèle permettant précisément l'étude des milieux hétérogènes et fracturés est utilisé. Son hypothèse de base est que l'édifice se comporte comme s'il était constitué d'un assemblage de blocs se déplaçant les uns par rapport aux autres. L'éruption très bien documentée du Mont St Helens (1980) sert de test pour cette méthode de blocs, en permettant de comparer déplacements calculés et déplacements mesurés. Quatre modèles bi-dimensionnels de ce volcan sont construits à partir d'une coupe géologique nord-sud. Chacun d'eux permet de tester l'effet d'un paramètre du modèle (géométrie, conditions aux limites, coefficient de frottement entre blocs, chemin de sollicitation). L'intrusion d'un dôme de lave à l'intérieur du flanc nord est simulée par l'application d'une montée en pression incrémentale puis les modèles sont soumis à une accélération horizontale simulant un séisme. Les résultats de cette modélisation mettent en évidence la dépendance des modes de déformation et de rupture vis à vis du coefficient de frottement entre les blocs. On obtient un assez bon accord avec les observations pour la plus faible des deux valeurs de ce coefficient testées (O. S). La rupture du flanc nord en grand glissement de terrain se produit aussi bien sous la seule influence de la montée en pression que sous pression et séisme combinés. Mais le second type de chargement donne un meilleur accord des résultats avec la réalité, et confirme ainsi qu'un séisme était bien à l'origine de l'éruption. Enfin, on discute, à la lumière de ces résultats, de la possibilité d'appréhender les structures internes et les mouvements du magma, à partir des mesures de déplacements de surface
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Tanays, Eric. "Approche algorithmique des conceptions geometriques et geotechniques de mines a ciel ouvert : application a la mine de carmaux (u.e. tarn, h.b.c.m., cdf)." Paris, ENMP, 1989. http://www.theses.fr/1989ENMP0142.
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Le travail de recherche a pour objectif la realisation du logiciel degres destine a la prevision de la geometrie de la fosse d'une mine a ciel ouvert et la detection des risques de rupture. Il a ete mis en oeuvre sur le site de la "grande decouverte" de carmaux (tarn - france)
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Abdelhedi, Anouar. "Modélisation de l'effet de groupe dans le clouage des pentes." Paris 6, 1986. http://www.theses.fr/1986PA066042.
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De récentes expérimentations réalisées sur des sites réels, ont permis de mettre en évidence la complexité du comportement de groupe de pieux dans une pente instable. On fait le point sur les méthodes existantes et on approfondit l'étude du mécanisme du comportement du sol au voisinage d'une rangée de pieux en se limitant au phénomène d'interaction sol-pieu. Apres étude bibliographique du phénomène donnant lieu à la programmation de deux des méthodes les plus significatives, on réalise deux approches en déformation: modélisation en continuum élastique permettant de prendre en compte une géométrie de maillage des pieux quelconques et d'appliquer au groupe une sollicitation en déplacement très générale, modélisation s'appuyant sur la méthode des éléments finis et sur un modèle bidimensionnel horizontal simulant l'écoulement du sol entre une rangée de pieux. Comparaison de diverses méthodes.
Books on the topic "Fractured Slope"
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H, Dowding C., American Society of Civil Engineers. Geotechnical Engineering Division., and ASCE National Convention (1985 : Denver, Colo.), eds. Rock masses: Modeling of underground openings, probability of slope failure, fracture of intact rock : proceedings of the symposium. New York, N.Y: ASCE, 1985.
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Dowding, Charles H. Rock Masses: Modeling of Underground Openings/Probability of Slope Failure/Fracture of Intact Rock : Proceedings of the Symposium Sponsored by the Geotechnical eng. Amer Society of Civil Engineers, 1985.
Find full textBook chapters on the topic "Fractured Slope"
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Yatabe, R., N. Yagi, K. Yokota, and N. P. Bhandary. "Landslide clay behavior and countermeasures works at the fractured zone of Median Tectonic Line." In Slope Stability Engineering, 1199–202. London: Routledge, 2021. http://dx.doi.org/10.1201/9780203739600-99.
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Zhang, Zhiyong. "Characterization and Monitoring of an Unstable Rock Face by Microseismic Methods." In Civil and Environmental Engineering for the Sustainable Development Goals, 97–108. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99593-5_8.
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AbstractUnstable rock slopes are likely to cause rockfalls, threatening human lives and properties, industrial activities, and transportation infrastructures in mountain areas. There is an increasing demand to forecast and mitigate the potential damage of rockfalls by developing a reliable early warning system. In this thesis, an unstable mountain slope in northern Italy was selected as the research target. A microseismic monitoring network has been operating since 2013 as a field research laboratory to study the microseismic monitoring technique in the perspective of developing rockfall early warning systems. Locating microseismic events is a basic step of this technique to obtain the location of developing cracks as possible precursors of rockfalls. However, it is still a challenging task due to the heterogeneity of fractured rock slopes. The main purpose of this thesis is to address the issues related to event localization for microseismic monitoring strategy applied to the unstable rock face. Graphical Abstract
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Ogita, N., Y. Kito, T. Kimizu, and R. Yatabe. "Physical properties of clay from landslides in large fracture zones." In Slope Stability Engineering, 1229–32. London: Routledge, 2021. http://dx.doi.org/10.1201/9780203739600-105.
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Nishimura, F., R. Yatabe, N. Yagi, K. Yokota, and T. Shibata. "Characteristics of groundwater quality in fracture zone landslides at Shikoku area." In Slope Stability Engineering, 1159–63. London: Routledge, 2021. http://dx.doi.org/10.1201/9780203739600-92.
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Zhang, Ke. "Fracture Mechanics Method." In Failure Mechanism and Stability Analysis of Rock Slope, 227–48. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5743-9_11.
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Merrien-Soukatchoff, Véronique, Jérôme Duriez, Muriel Gasc-Barbier, Félix Darve, and Frédéric-Victor Donzé. "Mechanical Stability Analyses of Fractured Rock Slopes." In Rockfall Engineering, 67–112. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118601532.ch3.
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Pan, Qi Xin, and Lai Shan Chang. "A Study of Application about FLAC-3D in Damage of Rock Mass Slope." In Fracture and Strength of Solids VI, 1427–32. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-989-x.1427.
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Liu, Y. Q., Hai Bo Li, H. C. Dai, Jun Ru Li, and Qing Chun Zhou. "Preliminary Study on the Progressive Failure of a Layered Rock Slope under Explosions." In Fracture and Strength of Solids VI, 1461–66. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-989-x.1461.
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Zhang, Qiang Yong, X. T. Zhang, and W. Xiang. "Application of Sliding Block Computation Model in Stability Evaluation for Anchored Rockmass Slope." In Fracture and Strength of Solids VI, 1515–0. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-989-x.1515.
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Lin, San-Shyan, Jen-Cheng Liao, Sheng-Der Yang, and Li-Yuan Huang. "Remediation of a Failed Slope Located at Fault Fracture Zone." In Geotechnical Hazards from Large Earthquakes and Heavy Rainfalls, 421–30. Tokyo: Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56205-4_39.
Full textConference papers on the topic "Fractured Slope"
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Hu, Jingyun, Shulin Li, Ping Li, Feng Lin, Z. Xing, Fuhua Peng, Z. LIn, J. Bao, and Zheng-fang Yu. "Research on quality factor for evaluating stability of high and steep rock slope fractured by underground mining." In First Asia Pacific Slope Stability in Mining Conference. Australian Centre for Geomechanics, Perth, 2016. http://dx.doi.org/10.36487/acg_rep/1604_45_hu.
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Ibrahim, Ahmed Farid, Mazher Ibrahim, Matt Sinkey, Thomas Johnston, and Wes Johnson. "Unique Fall Off Signatures for Stage Fracture Characterization, Actual Field Cases." In SPE Western Regional Meeting. SPE, 2021. http://dx.doi.org/10.2118/200887-ms.
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Abstract Multistage hydraulic fracturing is the common stimulation technique for shale formations. The treatment design, formation in-situ stress, and reservoir heterogeneity govern the fracture network propagation. Different techniques have been used to evaluate the fracture geometry and the completion efficiency including Chemical Tracers, Microseismic, Fiber Optics, and Production Logs. Most of these methods are post-fracture as well as time and cost intensive processes. The current study presents the use of fall-off data during and after stage fracturing to characterize producing surface area, permeability, and fracture conductivity. Shut-in data (15-30 minutes) was collected after each stage was completed. The fall-off data was processed first to remove the noise and water hammer effects. Log-Log derivative diagnostic plots were used to define the flow regime and the data were then matched with an analytical model to calculate producing surface area, permeability, and fracture conductivity. Diagnostic plots showed a unique signature of flow regimes. A long period of a spherical flow regime with negative half-slope was observed as an indication for limited entry flow either vertically or horizontally. A positive half-slope derivative represents a linear flow regime in an infinitely conductive tensile fracture. The quarter-slope derivative was observed in a bilinear flow regime that represents a finite conductivity fracture system. An extended radial flow regime was observed with zero slope derivative which represents a highly shear fractured network around the wellbore. For a long fall-off period, formation recharge may appear with a slope between unit and 1.5 slopes derivative, especially in over-pressured dry gas reservoirs. Analyzing fall-off data after stages are completed provides a free and real-time investigation method to estimate the fracture geometry and a measure of completion efficiency. Knowing the stage properties allows the reservoir engineer to build a simulation model to forecast the well performance and improve the well spacing.
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Liu, Zhanyuan, Tamer Moussa, and Hassan Dehghanpour. "Flowback Pattern-Recognition to Distinguish Between Formation and Fracturing Water Recovery." In SPE Canadian Energy Technology Conference. SPE, 2022. http://dx.doi.org/10.2118/208959-ms.
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Abstract We analyze flowback production data of 502 multi-fractured horizontal oil and gas wells completed in the Montney Formation and 83 oil wells completed in the Duvernay and Horn River Formations. The main goal of this paper is to evaluate the possibility of distinguishing between formation and fracturing water based on the water-flowback response. We hypothesize that: 1) the slope of water-flowback harmonic decline (HD) profile is reversely proportional to formation water mobility, 2) the deviations from the unit slope on rate-normalized pressure (RNP) plots is proportional to the slope of HD, and 3) the slope of water-flowback HD correlates with the initial water saturation (Swi). To verify our hypothesis, we 1) classify the observed HD trends of water-flowback rate based on slopes, 2) construct RNP diagnostic plots of the studied wells, 3) analyze log data and estimate average Swi by using Archie equation (1952) for the studied wells. 4) investigate the effects of Swi on the water-flowback pattern. The results show that there are two distinct flowback patterns. The first flowback pattern shows sharp slope (>10-41/day) of water-flowback HD profile and relatively high slope values (0.64 to 0.984 kpa/m3) of the corresponding RNP plots. However, the second pattern shows very low slope of HD (<5 × 10-5 1/day), with some wells showing no significant decline of water rate through the entire flowback process, also relatively low slope values (0 to 0.23) of the corresponding RNP plots. Analysis of the log data shows a positive correlation between Swi and slope of water-flowback HD profile. We also found that the slopes are proportional to the slope of RNP. These results indicate that as Swi increases, slope of HD decreases and there is more deviation from the unit-slope on the RNP plots.
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Zhang, Junjing, Nola Zwarich, Robert Burton, Paul Carman, Eric Davis, Manabu Nozaki, Brian Buck, Adam Lewis, and Brett Wendt. "Optimizing Longitudinal Fracture Design for Horizontal Well Completions in Laminated Sandstone Reservoirs." In SPE Hydraulic Fracturing Technology Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/209158-ms.
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Abstract Horizontal wells with multi-stage longitudinal fractures have been widely used to develop low-to-moderate permeability sandstone formations in enhanced oil recovery schemes. A long-held misconception exists that high fracture conductivity is not essential to well productivity for longitudinal fractures in openhole completions because the pressure drop through the fracture is small due to the geometry. This study provides workflows to optimize longitudinal fracture design for horizontal well completions on the North Slope of Alaska and presents practical considerations that challenge this misconception. Mechanical properties of core samples across the reservoir interval were evaluated by hardness-based strength calculators and tri-axial compression tests. Based on the rock strength profile, candidate intervals were selected for fracture conductivity measurements. Both summer (low salinity) and winter (high salinity) seawater based fracturing fluids were injected through the propped fracture cell containing both sandstone and mudstone lithologies. Numerical fracture models were built and matched to bottomhole pressures acquired during project appraisal well stimulations. Proppant concentration distribution along the fracture was generated for different design scenarios by varying proppant volume, proppant size, pump schedule, etc. The impact of various design scenarios on well production was also investigated. Full alignment between the fracture plane and the wellbore results in the highest productivity for fractured horizontal wells with openhole completions. However, calculations demonstrate that even a few degrees of misalignment between horizontal well orientation and the maximum horizontal principal stress results in fracture deviation from the open hole. Due to flow along the fracture and convergence from the fracture to the wellbore, fracture conductivity dominates the pressure drop and completion skin factor for this geometry. Since actual fracture conductivities in wells on the North Slope of Alaska are not infinite, it is therefore inappropriate to use "infinitely-acting" fracture assumptions as has often been used historically for longitudinally fractured horizontal wells with openhole completions. Fracture conductivity tests show severe conductivity loss due to gel residue as well as mudstone and seawater interactions. Realistic discount factors for fracture conductivities in the targeted shallow sandstone-mudstone formations were developed for subsequent reservoir studies. Modeling results suggest that larger job sizes and bigger proppant are needed to achieve desirable skin factors and well inflow performance when the fracture becomes misaligned from the wellbore.
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Sun, Zhaole, Linsong Cheng, Xulin Du, Pin Jia, Renyi Cao, and Yongchao Xue. "Typical Curve and Diagnosis Method for Identifying Fracture Closure Points of Fractured Wells in Flowback and Early-Time Production Period for Tight Oil Reservoir – A Field Example from Ordos Basin in China." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210272-ms.
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Abstract Fracturing fluids will carry an amount of proppant flowing back to the wellbore due to the inappropriate flowback schedule, which causes some parts of fractures to be closed without support. The appearance of closed fracture sections without support (pinch point) has a serious negative effect on well performance and is also a potential signal of refracturing. A four-region model considering fracture closure is developed to detect pinch points by analyzing production data in material equilibrium time. Therefore, a novel four-region flow model is proposed to study the influence of pinch points on well dynamics performance in the initial stage of production and to diagnose the pinch point. In this model, the fluid flow to the wellbore is regarded as three parts: matrix, fracture, and pinch points. The position of the pinch point on the fracture (near wellbore) is considered. The existence of pinch points makes the fracture conductivity segmented, and the partial closure of fracture can be simulated by setting different fracture lengths, widths, and permeability. The flow in each region is treated as the linear flow and is coupled through boundary conditions and flux supply. Thereby, the mathematical model of flow containing pinch points is established. This paper analyzes the production data of oil well, draws the logarithmic curve of RNP and its derivative RNP’ versus the material balance time (MBT), and conducts rate transient analysis to determine the occurrence of pinch points. In the case of the near-wellbore pinch point, the slope of the first half of RNP curves is relatively small, while the slope of the back section is about 1/2. Compared with RNP curves, the early slope of RNP’ curves is relatively large and gradually changes into the linear flow stage with a slope of 1/2. Different properties of pinch points mainly affect the slope of the left and right ends of RNP and RNP’ curves. The new analysis method can be used to analyze the influence of fracture closure position and degree of fracture closure on well productivity. Finally, the novel four-region flow analysis model was applied to the analysis of oil production data from a typical well in Ordos Basin. The length, width, and permeability of the near-wellbore fracture closure section can be obtained by fitting the proposed chart. The novel four-region flow model method and its curve characteristics provided in this article can be used as an important reference for judging whether there is a pinch point in fracture. It has a certain guiding significance for the formulation of fracturing schemes for new wells and whether old wells need refracturing in actual production.
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Cao, Chong, Tamer Moussa, and Hassan Dehghanpour. "Parent Well Characterization by Comparative Analysis of Initial and Second Flowback." In SPE Hydraulic Fracturing Technology Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212368-ms.
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Abstract Infill drilling is becoming a common practice for more efficient development of tight reservoirs. However, child-well stimulation may lead to a parent-child well interference or a fracture hit. To mitigate the negative impacts of a fracture hit, the parent well is preloaded before the stimulation of child wells. Then, the injected water during the pre-loading period is later produced back to the surface. The preloading flowback (second flowback) data of parent wells may provide an opportunity for fracture charactrization. The main objective of this research is to compare the responses of initial and second flowback to capture the changes in fracture characterstics after production and preload processes. We construct rate-normalized pressure (RNP) diagnostic plots on both initial and second flowback (IFB and SFB, respectively) of six multi-fractured horizontal wells completed in Niobrara and Codell formations in DJ Basin. In general, the slope of RNP versus MBT during the SFB period is higher than that during the IFB period, except for well 1. We estimate the changes in average effective fracture volume (Vef) by analyzing the changes in the RNP slope and total compressibility during these two flowback periods. Compared to the IFB period, the Vef is generally decreased during the SFB period. The loss percentage of effective fracture volume (RVef) is estimated at 10-40%. We also compare the drive mechanisms for the two flowback periods by calculating the compaction drive index (CDI), hydrocarbon-drive index (HDI), and water-drive index (WDI). The dominant driving mechanism during both flowback periods is CDI, but its contribution is reduced by 12% in the SFB period. This drop is generally compensated by a relatively higher HDI during this period. Finally, we investigate the effects of duration of production (tp) on RVef. There is a positive correlation between tp and RVef during the two flowback periods. Therefore, the loss of effective fracture volume might be attributed to the pressure depletion in fractures caused by the long production period (more than 800 days).
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Roche, Jeff, Jack Harfoushian, Ashish Datey, Dale Lewis, and Francis Advent. "Integration of Wireline Formation Tester Pressures with Advanced Formation Evaluation and Image Logs in Fractured Marine Slope Carbonates." In SPE Asia Pacific Oil & Gas Conference and Exhibition. Society of Petroleum Engineers, 2016. http://dx.doi.org/10.2118/182412-ms.
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Sheikh, Hafiz Mustafa Ud Din, W. J. Lee, H. S. Jha, and Sheraz Ahmed. "Establishing Flow Regimes for Multi-Fractured Horizontal Wells in Low-Permeability Reservoirs." In International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22694-ms.
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Abstract This paper presents rigorous theoretical guidelines for durations of flow regimes for multi-fractured horizontal wells in ultra-low permeability reservoirs. Theory and practice lead us to expect four regimes: early ramp-up, transient, transition, and boundary-dominated flow (BDF) in these wells. We must model each of these flow regimes for proper forecasting and for construction of TWPs (aka type wells or type curves), but, without guidance from theory and verification in practice, the durations of these flow regimes are difficult to observe in production histories or to predict when forecasting. These forecasts have significant impact on financial decisions regarding low-permeability reservoir development. We can most readily identify flow regimes using log-log plots of pressure-normalized rate vs. time for wells produced at near-constant bottom-hole pressure. This is adequate to determine the start and end of transient flow, with a straight line whose slope is near −1/2. Diagnosis is enhanced if we add normalized rate vs. material-balance time plots, which transform the well response to an equivalent constant-rate profile, on which we can identify BDF with a straight line with −1 slope. On this plot, the transition flow regime lies between the end of transient flow and the start of BDF. In some wells, with relatively longer production histories, we can readily identify these flow regimes, but many if not most wells in a play will display neither transition nor BDF regimes. To fill this gap in knowledge, we simulated flow histories using analytical solutions, which provide shapes and durations of the flow regimes. Starts and ends of flow regimes depend on arbitrary assumptions about deviations from straight lines, which can be determined in theory using derivatives of the analytical solutions. In practice, wells do not follow theory exactly by any means, but we find in our examination of actual well production histories that theory provides excellent guidance that enhances our understanding of actual production profiles. We present our simulated production histories for wells in terms of dimensionless variables, which generalizes their applicability. For actual situations, with known or estimated reservoir and completion properties, we can use these plots of dimensionless variables to determine approximate durations of flow regimes. Importantly, for the common situation in which no production data are available beyond transient flow, we can estimate the shape of the remaining production profile in a way significantly superior to the common two-segment Arps decline model with an assumed terminal decline rate at an assumed time. Critics of the industry, particularly in the financial community, have suggested that this common approach leads to optimistic production forecasts. Realistic forecasts of production profiles for individual wells, which our workflow based on rigorous theory enhances, can improve the credibility of resource evaluators within and beyond individual companies. This is especially important for TWP construction, on which many important financial decisions are based.
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Behmanesh, H., H. Hamdi, and C. R. Clarkson. "Analysis of Transient Linear Flow Associated with Hydraulically-Fractured Tight Oil Wells Exhibiting Multi-Phase Flow." In SPE Middle East Unconventional Resources Conference and Exhibition. SPE, 2015. http://dx.doi.org/10.2118/spe-172928-ms.
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Abstract Hydraulically-fractured vertical and horizontal wells completed in the tight formations typically exhibit long periods of transient linear flow that may last many years or decades. From this transient linear flow period, the linear flow parameter (xf√k) may be extracted. However, changes in effective permeability to the oil phase during production, caused by wellbore pressure falling below the saturation pressure, affect the flow dynamics in tight oil reservoirs and complicate the analysis. The use of methods that assume single-phase flow properties, such as the square-root of time plot, can lead to significant errors in linear flow parameter estimates. In this study, an analytical method is introduced to mathematically correct the slope of the square-root-of-time plot for the effects of multi-phase flow through the use of modified pseudovariables. Although the correction was derived for wells producing at constant flowing pressure during transient linear flow, the method is extended for wells producing at variable rate/flowing pressures. In order to evaluate pseudovariables used in the correction, the saturation-pressure relationship must be known. In this work, an analytical method for evaluating the saturation-pressure relationship is also developed. The results of our new analytical method for linear flow analysis are validated against numerical simulation. The new method yields linear flow parameter estimates that are within 10% of those input into the numerical simulator.
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Zhao, Y., and K. Esmaeili. "Probabilistic Step-Path Slope Stability Analysis Using Spatially Constrained DFN Models – A Case Study at Tasiast Mine." In 3rd International Discrete Fracture Network Engineering Conference. ARMA, 2022. http://dx.doi.org/10.56952/arma-dfne-22-0030.
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Abstract In this paper, geotechnical and structural data from an open pit mine were used to generate spatially constrained largescale DFN models. Data from geotechnical boreholes were used to develop 3D block models of volumetric fracture intensity (P32), using a geostatistical simulation method. The block models were used for spatially constraining 3D geo-cellular DFN models. The fracture centers within the DFN cellular grid are controlled by the cellular P32 values, estimated using the 3D block model. The joints orientation was bootstrapped from drillhole loggings whereas trace length data, collected across the pit area, were used to further calibrate the geo-cellular models. The resulting DFN models represented the spatial variation of fracture geometry and intensity along the pit area and were employed for numerical modeling of step-path slope stability analysis of the pit slopes. 2D cross sections of the 3D DFN models were embedded into 2D finite element models of the pit slope for a probabilistic step path stability analysis. In addition, the DFN models were used to estimate the rock bridge percentage along the pit walls which was ultimately used to assess the composite rock mass strength for a limit equilibrium analysis of the overall pit slope. The results of the two numerical approaches were compared to a simplistic approach assuming an average rock mass structural condition.
Reports on the topic "Fractured Slope"
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Chen, Z., S. E. Grasby, C. Deblonde, and X. Liu. AI-enabled remote sensing data interpretation for geothermal resource evaluation as applied to the Mount Meager geothermal prospective area. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330008.
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The objective of this study is to search for features and indicators from the identified geothermal resource sweet spot in the south Mount Meager area that are applicable to other volcanic complexes in the Garibaldi Volcanic Belt. A Landsat 8 multi-spectral band dataset, for a total of 57 images ranging from visible through infrared to thermal infrared frequency channels and covering different years and seasons, were selected. Specific features that are indicative of high geothermal heat flux, fractured permeable zones, and groundwater circulation, the three key elements in exploring for geothermal resource, were extracted. The thermal infrared images from different seasons show occurrence of high temperature anomalies and their association with volcanic and intrusive bodies, and reveal the variation in location and intensity of the anomalies with time over four seasons, allowing inference of specific heat transform mechanisms. Automatically extracted linear features using AI/ML algorithms developed for computer vision from various frequency bands show various linear segment groups that are likely surface expression associated with local volcanic activities, regional deformation and slope failure. In conjunction with regional structural models and field observations, the anomalies and features from remotely sensed images were interpreted to provide new insights for improving our understanding of the Mount Meager geothermal system and its characteristics. After validation, the methods developed and indicators identified in this study can be applied to other volcanic complexes in the Garibaldi, or other volcanic belts for geothermal resource reconnaissance.