The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform

Nadir Plasencia - One of the best experts on this subject based on the ideXlab platform.

  • First Infilling of the Venda Nova II Unlined High-Pressure Tunnel: Observed Behaviour and Numerical Modelling
    Rock Mechanics and Rock Engineering, 2014
    Co-Authors: Luís N. Lamas, Noemí S. Leitão, Carlos Esteves, Nadir Plasencia
    Abstract:

    The underground structures of the Venda Nova II reversible hydroelectric power scheme present features that make it an interesting case study. Worthy of mention are the inclination and length of the unlined Pressure Tunnel, the high water head and the great depth of the powerhouse cavern. In projects of this type, the main effect of the internal water Pressure in the Pressure Tunnel is the establishment of seepage from the Tunnel into the rock mass, which can reach the adits and the powerhouse cavern. This seepage is influenced by several factors, such as the geometry of the underground openings, the rock mass properties—namely, the joints characteristics—and the stress state resulting from the excavation and from the internal water Pressure. This article presents the main features of the underground structures of the Venda Nova II scheme and a detailed description of the observed behaviour during the first infilling of the Pressure Tunnel. A three-dimensional multi-laminated numerical model of the rock mass hydromechanical behaviour was developed to help understand the observed behaviour. The model assumptions in regard to the geometry of the openings, the jointing pattern, the rock mass hydraulic and mechanical behaviour, as well as the hydromechanical interaction, are described. Results obtained with the numerical model are presented and compared with the observed behaviour. Finally, the validity and importance of the numerical tools for the interpretation of the rock mass hydromechanical behaviour is discussed.

Krishna Kanta Panthi - One of the best experts on this subject based on the ideXlab platform.

  • Detailed engineering geological assessment of a shotcrete lined Pressure Tunnel in the Himalayan rock mass conditions: a case study from Nepal
    Bulletin of Engineering Geology and the Environment, 2020
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    The complex topography, geology, and tectonic environment prevailing in the Himalaya are the main challenges while applying the unlined or shotcrete lined Pressure Tunnel concept for hydropower projects. In addition, rock masses in the Himalayan region are influenced by faulting, folding, schistosity, and jointing to a varying degree representing geological complexity. Similarly, frequent occurrence of large scale earthquakes changes in situ stress dynamics. In spite of these challenges, an unlined/shotcrete lined Pressure Tunnel is being constructed at the headrace Tunnel system of Upper Tamakoshi Hydroelectric Project (UTHP) in the Nepal Himalaya. This article studies the unlined or shotcrete lined Pressure Tunnel in terms of the topographical conditions, in situ stress state, and overall rock engineering aspects. First, the Pressure Tunnel alignment is assessed using the Norwegian confinement criteria. Second, the minimum principal stress state is assessed using numerical simulation by validating measured in situ stress conditions. Finally, a comprehensive assessment on the rock engineering aspects of the headrace Tunnel is carried out. It has been found that if there exist good quality rock mass with tight joints, it is possible to apply the unlined/shotcrete lined Pressure Tunnel system in the Himalaya provided that the stress requirement is fulfilled. It was also found that the Norwegian confinement criteria are too optimistic for direct use in the design of high Pressure headrace Tunnel alignment. The detailed rock engineering assessment and stress state analysis indicated that there are some critical locations along the Upper Tamakoshi headrace Tunnel alignment. This is specially the case for an about 700 m downstream stretch of the headrace Tunnel from where there is a risk of hydraulic jacking, which may possibly lead to excessive water leakage during power plant operation.

  • Evaluation of earthquake impact on magnitude of the minimum principal stress along a shotcrete lined Pressure Tunnel in Nepal
    Journal of rock mechanics and geotechnical engineering, 2019
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    Abstract In situ stress condition in rock mass is influenced by both tectonic activity and geological environment such as faulting and shearing in the rock mass. This influence is of significance in the Himalayan region, where the tectonic movement is active, resulting in 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 first highlights the importance of the magnitude of the minimum principal stress in the design of unlined or shotcrete lined Pressure Tunnel as water conveyance system used for hydropower schemes. Then we evaluated the influence of local shear faults on the magnitude of the minimum principal stress along the shotcrete lined high Pressure Tunnel of Upper Tamakoshi Hydroelectric Project (UTHP) in Nepal. A detailed assessment of the in situ stress state is carried out using both measured data and three-dimensional (3D) numerical analyses with FLAC3D. Finally, analysis is carried out on the possible changes in the magnitude of the minimum principal stress in the rock mass caused by seismic movement (dynamic loading). A permanent change in the stress state at and nearby the area of shear zones along the Tunnel alignment is found to be an eminent process.

  • 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, 2019
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    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.

  • a dynamic analysis of in situ stress state at the upper tamakoshi hydroelectric project area
    Hydro Nepal: Journal of Water Energy and Environment, 2018
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    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

  • Groundwater Effect on Faulted Rock Mass: An Evaluation of Modi Khola Pressure Tunnel in the Nepal Himalaya
    Rock Mechanics and Rock Engineering, 2013
    Co-Authors: Pawan Kumar Shrestha, Krishna Kanta Panthi
    Abstract:

    Groundwater has a negative impact not only in construction activity, but also in stability of a Tunnel. Severity increases particularly in Tunnels passing through fault gouge and breccia, where rock material is completely crushed and extremely weak. Instantaneous collapse and excessive plastic deformation is most likely in Tunnels passing through such zones. Often, ‘flowing’ conditions may prevail if groundwater is mixed in the rock mass. This paper presents one such Tunnel case in the Nepal Himalaya; i.e. the Modi Pressure Tunnel. This Pressure Tunnel passes through a tectonic fault consisting of gouge material. High deformation in the Tunnel was observed while excavating the Tunnel through the fault. Based on the Tunnel deformation that was actually measured, the paper first back-calculates the rock mass strength by analytical approach. Then, the extent of in-situ stress condition in the area is determined by numerical modeling for the rock mass with no ground water in consideration. The ground water effect is then analyzed. We found that the effect of ground water with a static head

Reinhold Gerstner - One of the best experts on this subject based on the ideXlab platform.

  • Kopswerk II headrace Tunnel – construction of the Pressure Tunnel and associated works / Triebwasserstollen Kopswerk II – Bauarbeiten Druckstollen und Nebenanlagen
    Geomechanik Und Tunnelbau, 2011
    Co-Authors: Herbert Schnetzer, Reinhold Gerstner
    Abstract:

    The article concerns the construction of the Kopswerk II Pressure Tunnel and associated works. Important details of the construction and construction sequence are described, particularly the logistics of a large site in the high mountains. In addition to a summary of the various drill and blast Tunnels, the article concentrates on the TBM drive and the drilling and grouting works in the Pressure Tunnel. Der Beitrag befasst sich mit den Bauarbeiten fur den Druckstollen des Kopswerkes II und dessen Nebenanlagen. Dabei werden die Eckpfeiler der Bauausfuhrung und des Bauablaufes, insbesondere auch die Logistik einer Baustelle im Hochgebirge beschrieben. Neben einem Abriss uber die verschiedenen Sprengvortriebe wird vor allem uber den TBM-Vortrieb und die Bohr- und Injektionsarbeiten im Druckstollen berichtet.

  • kopswerk ii headrace Tunnel construction of the Pressure Tunnel and associated works triebwasserstollen kopswerk ii bauarbeiten druckstollen und nebenanlagen
    Geomechanik Und Tunnelbau, 2011
    Co-Authors: Herbert Schnetzer, Reinhold Gerstner
    Abstract:

    The article concerns the construction of the Kopswerk II Pressure Tunnel and associated works. Important details of the construction and construction sequence are described, particularly the logistics of a large site in the high mountains. In addition to a summary of the various drill and blast Tunnels, the article concentrates on the TBM drive and the drilling and grouting works in the Pressure Tunnel. Der Beitrag befasst sich mit den Bauarbeiten fur den Druckstollen des Kopswerkes II und dessen Nebenanlagen. Dabei werden die Eckpfeiler der Bauausfuhrung und des Bauablaufes, insbesondere auch die Logistik einer Baustelle im Hochgebirge beschrieben. Neben einem Abriss uber die verschiedenen Sprengvortriebe wird vor allem uber den TBM-Vortrieb und die Bohr- und Injektionsarbeiten im Druckstollen berichtet.

Luís N. Lamas - One of the best experts on this subject based on the ideXlab platform.

  • First Infilling of the Venda Nova II Unlined High-Pressure Tunnel: Observed Behaviour and Numerical Modelling
    Rock Mechanics and Rock Engineering, 2014
    Co-Authors: Luís N. Lamas, Noemí S. Leitão, Carlos Esteves, Nadir Plasencia
    Abstract:

    The underground structures of the Venda Nova II reversible hydroelectric power scheme present features that make it an interesting case study. Worthy of mention are the inclination and length of the unlined Pressure Tunnel, the high water head and the great depth of the powerhouse cavern. In projects of this type, the main effect of the internal water Pressure in the Pressure Tunnel is the establishment of seepage from the Tunnel into the rock mass, which can reach the adits and the powerhouse cavern. This seepage is influenced by several factors, such as the geometry of the underground openings, the rock mass properties—namely, the joints characteristics—and the stress state resulting from the excavation and from the internal water Pressure. This article presents the main features of the underground structures of the Venda Nova II scheme and a detailed description of the observed behaviour during the first infilling of the Pressure Tunnel. A three-dimensional multi-laminated numerical model of the rock mass hydromechanical behaviour was developed to help understand the observed behaviour. The model assumptions in regard to the geometry of the openings, the jointing pattern, the rock mass hydraulic and mechanical behaviour, as well as the hydromechanical interaction, are described. Results obtained with the numerical model are presented and compared with the observed behaviour. Finally, the validity and importance of the numerical tools for the interpretation of the rock mass hydromechanical behaviour is discussed.

Chhatra Bahadur Basnet - One of the best experts on this subject based on the ideXlab platform.

  • Detailed engineering geological assessment of a shotcrete lined Pressure Tunnel in the Himalayan rock mass conditions: a case study from Nepal
    Bulletin of Engineering Geology and the Environment, 2020
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    The complex topography, geology, and tectonic environment prevailing in the Himalaya are the main challenges while applying the unlined or shotcrete lined Pressure Tunnel concept for hydropower projects. In addition, rock masses in the Himalayan region are influenced by faulting, folding, schistosity, and jointing to a varying degree representing geological complexity. Similarly, frequent occurrence of large scale earthquakes changes in situ stress dynamics. In spite of these challenges, an unlined/shotcrete lined Pressure Tunnel is being constructed at the headrace Tunnel system of Upper Tamakoshi Hydroelectric Project (UTHP) in the Nepal Himalaya. This article studies the unlined or shotcrete lined Pressure Tunnel in terms of the topographical conditions, in situ stress state, and overall rock engineering aspects. First, the Pressure Tunnel alignment is assessed using the Norwegian confinement criteria. Second, the minimum principal stress state is assessed using numerical simulation by validating measured in situ stress conditions. Finally, a comprehensive assessment on the rock engineering aspects of the headrace Tunnel is carried out. It has been found that if there exist good quality rock mass with tight joints, it is possible to apply the unlined/shotcrete lined Pressure Tunnel system in the Himalaya provided that the stress requirement is fulfilled. It was also found that the Norwegian confinement criteria are too optimistic for direct use in the design of high Pressure headrace Tunnel alignment. The detailed rock engineering assessment and stress state analysis indicated that there are some critical locations along the Upper Tamakoshi headrace Tunnel alignment. This is specially the case for an about 700 m downstream stretch of the headrace Tunnel from where there is a risk of hydraulic jacking, which may possibly lead to excessive water leakage during power plant operation.

  • Evaluation of earthquake impact on magnitude of the minimum principal stress along a shotcrete lined Pressure Tunnel in Nepal
    Journal of rock mechanics and geotechnical engineering, 2019
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    Abstract In situ stress condition in rock mass is influenced by both tectonic activity and geological environment such as faulting and shearing in the rock mass. This influence is of significance in the Himalayan region, where the tectonic movement is active, resulting in 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 first highlights the importance of the magnitude of the minimum principal stress in the design of unlined or shotcrete lined Pressure Tunnel as water conveyance system used for hydropower schemes. Then we evaluated the influence of local shear faults on the magnitude of the minimum principal stress along the shotcrete lined high Pressure Tunnel of Upper Tamakoshi Hydroelectric Project (UTHP) in Nepal. A detailed assessment of the in situ stress state is carried out using both measured data and three-dimensional (3D) numerical analyses with FLAC3D. Finally, analysis is carried out on the possible changes in the magnitude of the minimum principal stress in the rock mass caused by seismic movement (dynamic loading). A permanent change in the stress state at and nearby the area of shear zones along the Tunnel alignment is found to be an eminent process.

  • 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, 2019
    Co-Authors: Chhatra Bahadur Basnet, Krishna Kanta Panthi
    Abstract:

    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.

  • a dynamic analysis of in situ stress state at the upper tamakoshi hydroelectric project area
    Hydro Nepal: Journal of Water Energy and Environment, 2018
    Co-Authors: Krishna Kanta Panthi, Chhatra Bahadur Basnet
    Abstract:

    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