54th U.S. Rock Mechanics/Geomechanics Symposium,
28 June - 1 July,
physical event cancelled
2020. American Rock Mechanics Association
2 in the last 30 days
10 since 2007
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In present paper, an underground powerhouse complex constructed in a hard rock environment in the North-Eastern part of India has been analysed. The analysis of the powerhouse cavern under various stages of excavation was performed using the Finite Element Method (FEM) for a realistic estimation of the rock mass behavior around the cavern. The effect of the face support along the longitudinal axis of the cavern has been considered in a 2-dimensional analysis by using a material softening effect. An analysis was also carried out for optimizing the orientation of the powerhouse cavern against wedge instability using the Unwedge analytical program. After alignment optimization, a stress deformation analysis of the cavern was performed for the determination of the support requirement of the rock mass around the powerhouse. The analysis concluded that the rock mass can support itself.
The objective of the project is to analyse and design a typical underground powerhouse complex. A powerhouse is that component of a hydropower project where the actual generation of electricity is carried out. When it is not feasible to locate a powerhouse on the surface, then it is constructed underground and termed as an underground powerhouse. When transformer hall is not placed inside a powerhouse but in a separate cavern, then the underground powerhouse is called as an underground powerhouse complex. Cavern which houses the transformer is called as the transformer house cavern (THC), while the cavern having all the utilities required for the generation of electricity is termed as the powerhouse cavern (PHC) (Figure 1).
The objective of an underground structure designer is to design the underground openings with minimum external supports in which the rock medium is the prime structural member. According to Obert and Duvall (1966), a self-supporting system is one in which the structural stresses are carried on the walls, pillars and other unexcavated parts of the opening rather than cavity's support system. Lunardi (2000) stated that the characteristic of underground structure design that have to be given sufficient weight is the stage where the underground structure is subjected to most stress. This stage is not the final stage where the cavity is finished and lined, but the intermediate construction stage. The intermediate construction stage is very much a more delicate stage because it is at this stage that the disturbances caused by the excavation have not yet been restrained by the support systems. Pender (1980), also keeping in line with this, proposed that underground openings that are excavated in a prestressed medium lead to a release of stresses that cause displacements around the openings.
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