A dynamic stress state analysis at the pressure tunnel of upper Tamakoshi HPP, Nepal

摘要

In theory, in-situ stress state of an area of concern is mainly governed by gravity-induced stress, tectonic activity and topographic condition of that area. The tectonic and geological environment such as faulting and shearing in the rock mass greatly influences magnitude of the in-situ stress of area under investigation. The Himalaya is renowned with its active tectonic movement resulting periodic dynamic earthquakes, which causes accumulation and sudden release of strain energy instigating changes in the in-situ stress environment. This paper aims to evaluate the influence by local shear fault on in-situ stress state along shotcrete lined high pressure tunnel of Upper Tamakoshi Project, where considerable hydrostatic head will act on the rock mass. A detailed assessment of in-situ stress state is carried out by using both measured data and three-dimensional numerical analysis using FLAC~(3D). Furthermore, an attempt has been made to evaluate changes on in-situ stress state caused by seismic activities (dynamic loading).