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Krishna Kanta Panthi - One of the best experts on this subject based on the ideXlab platform.
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Evaluation on the Minimum Principal Stress State and Potential Hydraulic Jacking from the Shotcrete-Lined Pressure Tunnel: A Case from Nepal
Rock Mechanics and Rock Engineering, 2019Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:Reliable estimation of in Situ Stress State is very important in implementing unlined/shotcrete-lined pressure tunnels and shafts. The topography, local tectonic setting and geological environment greatly influence the magnitude of in Situ Stress level. This paper aims to evaluate in Situ Stress State at the Upper Tamakoshi Hydroelectric Project (UTHP), where unlined/shotcrete-lined headrace tunnel with considerable hydrostatic head is being implemented. Initially measured minimum principal Stress indicated much lower values than the hydrostatic pressure at the downstream end of the headrace tunnel, which led to shift the alignment at the upper elevation with reduced hydrostatic pressure. In order to explore the reason behind much lower Stress level as expected, a comprehensive assessment is carried out by developing a full rock Stress model so that the minimum principal Stress along the unlined pressure tunnel is evaluated. To address the complex geotectonic and topographic environment of the UTHP project area, a final rock Stress model (FRSM) concept as suggested by Stephansson and Zang (2012) has been utilized. The FRSM concept considers stepwise evaluation of the in Situ Stress State analysis integrating the best estimate Stress model (BESM), Stress measurement methods (SMM) and integrated Stress determination methods (ISD). The analysis carried out revealed that the in Situ Stress State at the project area has high degree of spatial variation even at the similar overburden due to the presence of complex topography and the presence of local shear and weakness zones. The analysis further demonstrates that a presence of local shear/weakness zone has considerable de-Stressing effect, which leads to the reduction of in Situ minimum principal Stress magnitude. The reduction in the minimum principal Stress along the pressure tunnel increases the risk for the potential hydraulic jacking and leakage if static water pressure is higher than the magnitude of minimum principal Stress.
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evaluation of in Situ Stress State along the shotcrete lined high pressure headrace tunnel at a complex himalayan geological condition
Geosystem Engineering, 2018Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:ABSTRACTThe Himalayan region is renowned with its complex topography and active tectonic movement, which causes accumulation and sudden release of strain energy instigating changes in the in-Situ s...
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a dynamic analysis of in Situ Stress State at the upper tamakoshi hydroelectric project area
Hydro Nepal: Journal of Water Energy and Environment, 2018Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur BasnetAbstract:The in-Situ Stress condition in the rock mass is influenced by both tectonic and geological environment, such as faulting and shearing in the rock mass. This influence is of considerable magnitude in the Himalayan region where the tectonic movement is active, resulting periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy instigating changes in the in-Situ Stress environment in the rock mass. This paper evaluates the influence of local shear fault on the in-Situ Stress State along the shot crete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project, 456 MW in Nepal. A detailed assessment of the in-Situ Stress State is carried out by using both; measured data and three-dimensional numerical analysis using FLAC3D. The analysis includes evaluation on the possible changes in the in-Situ Stress State in the rock mass caused by seismic activities (dynamic loading). HYDRO Nepal JournalJournal of Water, Energy and Environment Issue: 23Year: 2018
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3D in-Situ Stress Model of Upper Tamakoshi Hydroelectric Project Area
Hydro Nepal: Journal of Water Energy and Environment, 2017Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:Reliable estimation of in-Situ Stress State is very important in implementing the shotcrete lined/ unlined tunnels and shafts. The in-Situ Stress State of the area of concern is mainly governed by the gravity-induced Stress, tectonic activity of the earth’s crust and topographic condition of that area. The local tectonic and geological environment such as faulting and shearing activities in general influences the magnitude of tectonic Stress level. The Himalayan region is renowned with its active tectonic movement (earthquake activities), which causes accumulation and sudden release of strain energy instigating changes in the Stress environment. This paper aims to evaluate in-Situ Stress State at the Upper Tamakoshi Hydroelectric Project, where shotcrete lined/ unlined headrace tunnel with considerable hydrostatic head is being implemented. A detailed assessment of the in-Situ Stress State is carried out by using both measured data and three-dimensional numerical analysis using FLAC3D. HYDRO Nepal Journal Journal of Water Energy and Environment Issue: 21, July, 2017 Page: 34-41 Upload Date: July 18, 2017
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evaluation of rock bursting phenomena in a tunnel in the himalayas
Bulletin of Engineering Geology and the Environment, 2012Co-Authors: Krishna Kanta PanthiAbstract:Tunnels passing beneath deep rock cover (overburden) are subject to instabilities caused by induced rock Stresses. In a relatively unjointed massive rock mass the instability is associated with rock spalling/rock bursting, while if the rock mass is weak, schistose, sheared and deformed, squeezing is more likely. This paper reports a study which reviews Stress-induced instability along the Parbati II headrace tunnel, evaluates the rock mechanical properties directly linked to the Stress-induced instabilities and back-calculates the magnitude of the in Situ Stress State using finite element numerical modeling. An attempt is made to evaluate the magnitude of the tectonic horizontal Stress component and to estimate the rock burst depth-impact. It is emphasized that more cases of tunnel damage should be studied to verify the applicability of the proposed equations and to establish the approximate range of the horizontal tectonic Stress component along the Himalayan chain.
Chhatra Bahadur Basnet - One of the best experts on this subject based on the ideXlab platform.
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Evaluation on the Minimum Principal Stress State and Potential Hydraulic Jacking from the Shotcrete-Lined Pressure Tunnel: A Case from Nepal
Rock Mechanics and Rock Engineering, 2019Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:Reliable estimation of in Situ Stress State is very important in implementing unlined/shotcrete-lined pressure tunnels and shafts. The topography, local tectonic setting and geological environment greatly influence the magnitude of in Situ Stress level. This paper aims to evaluate in Situ Stress State at the Upper Tamakoshi Hydroelectric Project (UTHP), where unlined/shotcrete-lined headrace tunnel with considerable hydrostatic head is being implemented. Initially measured minimum principal Stress indicated much lower values than the hydrostatic pressure at the downstream end of the headrace tunnel, which led to shift the alignment at the upper elevation with reduced hydrostatic pressure. In order to explore the reason behind much lower Stress level as expected, a comprehensive assessment is carried out by developing a full rock Stress model so that the minimum principal Stress along the unlined pressure tunnel is evaluated. To address the complex geotectonic and topographic environment of the UTHP project area, a final rock Stress model (FRSM) concept as suggested by Stephansson and Zang (2012) has been utilized. The FRSM concept considers stepwise evaluation of the in Situ Stress State analysis integrating the best estimate Stress model (BESM), Stress measurement methods (SMM) and integrated Stress determination methods (ISD). The analysis carried out revealed that the in Situ Stress State at the project area has high degree of spatial variation even at the similar overburden due to the presence of complex topography and the presence of local shear and weakness zones. The analysis further demonstrates that a presence of local shear/weakness zone has considerable de-Stressing effect, which leads to the reduction of in Situ minimum principal Stress magnitude. The reduction in the minimum principal Stress along the pressure tunnel increases the risk for the potential hydraulic jacking and leakage if static water pressure is higher than the magnitude of minimum principal Stress.
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evaluation of in Situ Stress State along the shotcrete lined high pressure headrace tunnel at a complex himalayan geological condition
Geosystem Engineering, 2018Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:ABSTRACTThe Himalayan region is renowned with its complex topography and active tectonic movement, which causes accumulation and sudden release of strain energy instigating changes in the in-Situ s...
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a dynamic analysis of in Situ Stress State at the upper tamakoshi hydroelectric project area
Hydro Nepal: Journal of Water Energy and Environment, 2018Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur BasnetAbstract:The in-Situ Stress condition in the rock mass is influenced by both tectonic and geological environment, such as faulting and shearing in the rock mass. This influence is of considerable magnitude in the Himalayan region where the tectonic movement is active, resulting periodic dynamic earthquakes. Each large-scale earthquake causes both accumulation and sudden release of strain energy instigating changes in the in-Situ Stress environment in the rock mass. This paper evaluates the influence of local shear fault on the in-Situ Stress State along the shot crete lined high pressure tunnel of Upper Tamakoshi Hydroelectric Project, 456 MW in Nepal. A detailed assessment of the in-Situ Stress State is carried out by using both; measured data and three-dimensional numerical analysis using FLAC3D. The analysis includes evaluation on the possible changes in the in-Situ Stress State in the rock mass caused by seismic activities (dynamic loading). HYDRO Nepal JournalJournal of Water, Energy and Environment Issue: 23Year: 2018
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3D in-Situ Stress Model of Upper Tamakoshi Hydroelectric Project Area
Hydro Nepal: Journal of Water Energy and Environment, 2017Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta PanthiAbstract:Reliable estimation of in-Situ Stress State is very important in implementing the shotcrete lined/ unlined tunnels and shafts. The in-Situ Stress State of the area of concern is mainly governed by the gravity-induced Stress, tectonic activity of the earth’s crust and topographic condition of that area. The local tectonic and geological environment such as faulting and shearing activities in general influences the magnitude of tectonic Stress level. The Himalayan region is renowned with its active tectonic movement (earthquake activities), which causes accumulation and sudden release of strain energy instigating changes in the Stress environment. This paper aims to evaluate in-Situ Stress State at the Upper Tamakoshi Hydroelectric Project, where shotcrete lined/ unlined headrace tunnel with considerable hydrostatic head is being implemented. A detailed assessment of the in-Situ Stress State is carried out by using both measured data and three-dimensional numerical analysis using FLAC3D. HYDRO Nepal Journal Journal of Water Energy and Environment Issue: 21, July, 2017 Page: 34-41 Upload Date: July 18, 2017
Wei Ju - One of the best experts on this subject based on the ideXlab platform.
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a preliminary study of the present day in Situ Stress State in the ahe tight gas reservoir dibei gasfield kuqa depression
Marine and Petroleum Geology, 2018Co-Authors: Wei Ju, Ke WangAbstract:Abstract Knowledge of the present-day in-Situ Stress State has significant applications in the exploration and development of tight gas reservoirs. The Ahe Formation is an important tight gas reservoir in the Dibei Gasfield of Kuqa Depression. However, prior to this study, little attention has been paid to the present-day in-Situ Stress field within the formation. In the present study, the in-Situ Stress orientation and magnitudes were investigated based on well log calculations and geomechanical modeling. The horizontal maximum principal Stress (SHmax) orientation was determined from interpretations of drilling-induced tensile fractures (DITFs) and borehole breakouts in imaging logs, which showed variations between NNW-SSE-trending and NNE-SSW-trending in the Dibei Gasfield. The in-Situ Stress magnitudes were calculated in four wells based on well logs, the results indicated a normal faulting Stress regime within the Ahe tight gas reservoir. Numerical simulation of the present-day in-Situ Stresses showed that the magnitudes of vertical Stress (Sv), SHmax and horizontal minimum principal Stress (Shmin) were −105.5 MPa∼-191.0 MPa, −88.9 MPa∼-142.9 MPa, and −79.1 MPa∼-127.7 MPa within the Ahe Formation, respectively. In addition, considering the present-day in-Situ Stress State in the Ahe Formation of Dibei Gasfield, natural fractures in directions parallel/sub-parallel to the SHmax orientation with high fracture angles showed great contributions to subsurface fluid flow. Borehole instability may become a potentially significant problem when drilling vertical wells and horizontal wells deviated toward the SHmax orientation in the Ahe tight gas reservoir of Dibei Gasfield.
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characteristics of in Situ Stress State and prediction of the permeability in the upper permian coalbed methane reservoir western guizhou region sw china
Journal of Petroleum Science and Engineering, 2018Co-Authors: Wei Ju, Zhaobiao Yang, Tongsheng Yi, Zhengguang ZhangAbstract:Abstract Coal permeability and in-Situ Stress State are important parameters for coalbed methane (CBM) exploration and development; however, the distribution pattern of the Upper Permian CBM reservoir permeability is poorly understood in the western Guizhou region, SW China. In the present study, based on measured injection/falloff and in-Situ Stress data in the Upper Permian coal seams of western Guizhou region, the present-day in-Situ Stress field, and its correlation with coal permeability were investigated. The orientation of the horizontal maximum principal Stress (SHmax) indicated a dominant ∼ NW-SE-trending. In addition, the present-day in-Situ Stress field showed an important control on coal permeability. The permeability in the Upper Permian coal seams decreased exponentially with the increased effective in-Situ Stress magnitude. By utilizing the finite element method (FEM), the present-day in-Situ Stress field in the western Guizhou was numerically analyzed based on a geomechanical two-dimensional (2D) model. Distribution of coal permeability in the Upper Permian CBM reservoir was predicted based on the relationship between coal permeability and effective in-Situ Stress magnitude. The results indicated that, in the western Guizhou region, vertically, coal permeability was relatively high and widely distributed shallower than approximately 780 m below ground level (bgl), whereas, it was extremely low and regularly varied with burial depth deeper than approximately 780 m bgl. Laterally, the distribution pattern of coal permeability was characterized by strong heterogeneity due to well-developed faults and folds. High values of the Upper Permian coal permeability were located in regions around Nayong-Zhijin, Panxian-Anlong and along Shuicheng-Liuzhi-Ziyun. The present study may provide geological references for the CBM reservoir productivity and subsequent analysis (e.g., wellbore stability, hydraulic fracturing design, and fault reactivation studies, etc.) in the western Guizhou region.
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In-Situ Stress distribution and coalbed methane reservoir permeability in the Linxing area, eastern Ordos Basin, China
Frontiers in Earth Science, 2017Co-Authors: Wei Ju, Jian Shen, Shangzhi Meng, Guozhang Li, Chao Li, Guang YangAbstract:Understanding the distribution of in-Situ Stresses is extremely important in a wide range of fields such as oil and gas exploration and development, CO2 sequestration, borehole stability, and Stress-related geohazards assessment. In the present study, the in-Situ Stress distribution in the Linxing area of eastern Ordos Basin, China, was analyzed based on well tested parameters. The maximum horizontal principal Stress (SHmax), minimum horizontal principal Stress (Shmin), and vertical Stress (Sv) were calculated, and they were linearly correlated with burial depth. In general, two types of in-Situ Stress fields were determined in the Linxing area: (i) the in-Situ Stress State followed the relation Sv>SHmax>Shmin in shallow layers with burial depths of less than about 940 m, indicating a normal faulting Stress regime; (ii) the SHmax magnitude increased conspicuously and was greater than the Sv magnitude in deep layers with depths more than about 940 m, and the in-Situ Stress State followed the relation SHmax>Sv>Shmin, demonstrating a strike-slip faulting Stress regime. The horizontal differential Stress (SHmax–Shmin) increased with burial depth, indicating that wellbore instability may be a potentially significant problem when drilling deep vertical wells. The lateral Stress coefficient ranged from 0.73 to 1.08 with an average of 0.93 in the Linxing area. The coalbed methane (CBM) reservoir permeability was also analyzed. No obvious exponential relationship was found between coal permeability and effective in-Situ Stress magnitude. Coal permeability was relatively high under a larger effective in-Situ Stress magnitude. Multiple factors, including fracture development, contribute to the variation of CBM reservoir permeability in the Linxing area of eastern Ordos Basin.
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in Situ Stress State in the linxing region eastern ordos basin china implications for unconventional gas exploration and production
Marine and Petroleum Geology, 2017Co-Authors: Wei Ju, Jian Shen, Shangzhi Meng, Caifang Wu, Yulin Shen, Zhaobiao Yang, Guozhang Li, Chao LiAbstract:Abstract The Carboniferous and Permian sedimentary rocks (mainly the Shanxi and Taiyuan formations) in the Linxing region, eastern Ordos Basin, China, host a significant volume of unconventional gas resources (coalbed methane, shale gas and tight sandstone gas). Currently, the in-Situ Stress State is poorly understood but knowledge of this is extremely important for a range of applications, such as gas exploration and production, fracture stimulation and wellbore stability. The maximum horizontal Stress ( S Hmax ), minimum horizontal Stress ( S hmin ) and vertical Stress ( S v ) magnitudes, and the S Hmax orientation in the Linxing region were systematically analyzed for the first time in the present study, which can provide a reference for subsequent numerical simulation and hydraulic fracturing design. Based on borehole breakouts and drilling-induced tensile fractures interpreted from borehole imaging logs, the S Hmax orientation rotates from ∼NEE-SWW-trending in the southern part to ∼ NWW-SEE-trending in the northern part of the Linxing region. Both conventional logs and extended leak-off tests were used for Stress magnitude determination. The results revealed three types of in-Situ Stress fields ( S v > S Hmax > S hmin , S Hmax > S v > S hmin and S Hmax > S v ≈ S hmin ), and a dominant strike-slip Stress regime ( S Hmax > S v ≥ S hmin ) was found for the entire well section in the target Shanxi Formation and Taiyuan Formation in the Linxing region. In addition, differential Stress increased with depth in the Linxing region, which indicates that wellbore instability might be a potentially significant problem when drilling wells that are vertical or ∼ N-S-trending.
Liang Zhao - One of the best experts on this subject based on the ideXlab platform.
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Strain Sensors with Temperature Compensation Employed for InSitu Stress Monitor
2020Co-Authors: Liang ZhaoAbstract:The hollow inclusion strain sensors employed for in-Situ Stress monitor use strain gages to detect strain changes of the rock, and the detected strain changes are transmitted to resistance changes in a Whetstone bridge, then the output voltage values of the bridge are finally used for in-Situ Stress calculation. In order to correct the temperature influence on the strain gages, thermistors are used to record the temperature changes during the monitor and achieve the temperature compensation. A monitor network containing 9 hollow inclusion strain sensors with temperature compensation were built to measure the inSitu Stress in an undersea mine, and the measuring results discover the distribution law of 3D in-Situ Stress State in the mine which can be used to optimize the mining design.
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Research on Hollow Inclusion Strain Sensors with Temperature Compensation Employed for In-Situ Stress Monitor Network
Indonesian Journal of Electrical Engineering and Computer Science, 2013Co-Authors: Liang ZhaoAbstract:The hollow inclusion strain sensors employed for in-Situ Stress monitor use strain gages to detect strain changes of the rock, and the detected strain changes are transmitted to resistance changes in a Whetstone bridge, then the output voltage values of the bridge are finally used for in-Situ Stress calculation. In order to correct the temperature influence on the strain gages, thermistors are used to record the temperature changes during the monitor and achieve the temperature compensation. A monitor network containing 9 hollow inclusion strain sensors with temperature compensation were built to measure the in-Situ Stress in an undersea mine, and the measuring results discover the distribution law of 3D in-Situ Stress State in the mine which can be used to optimize the mining design. DOI: http://dx.doi.org/10.11591/telkomnika.v11i11.2948 Full Text: PDF
Brendan Casey - One of the best experts on this subject based on the ideXlab platform.
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in Situ Stress State and strength in mudrocks
Journal of Geophysical Research, 2016Co-Authors: Brendan Casey, John T Germaine, P B Flemings, Brian FahyAbstract:The Stress State of mudrocks buried under uniaxial strain conditions is defined through a large number of laboratory triaxial tests performed on water-saturated resedimented mudrocks from a diverse set of geologic backgrounds. Unique relationships are found between the horizontal Stresses that develop during normal uniaxial compression (given by K0NC), critical State friction angle, and shear strength during undrained loading. Tests were performed over the effective Stress range of 0.1 to 100 MPa. Smectite-rich mudrocks display a more rapid reduction in shear strength with increasing effective Stress, which corresponds with a more rapid increase in horizontal Stresses. The relationship between horizontal Stresses and critical State friction angle found in this study compares favorably with the well-known correlation of Jâky (1948) which was developed for very low Stresses, even for friction angle values as low as 11°. Results for one mudrock suggest that this relationship also applies to mudrocks sheared from an unloaded (overconsolidated) State. The correlation between friction angle and K0NC is independent of the Stress path applied during the compression phase of a test. This is not the case for shearing under undrained conditions, however, and the application of a Stress path that produces uniaxial compression is necessary to measure a reliable shear strength. Systematic variations in K0NC and strength properties reflect an overall change in the shape and orientation of a mudrock's yield surface with effective Stress level. The results of this study can aid in estimating the in Situ Stress State and strength properties of mudrocks and this will have significant impact on a range of geoscience and engineering problems.