A dynamic analysis of in-situ stress state at the Upper Tamakoshi Hydroelectric Project area

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 envi-ronment in the rock mass. This paper evaluates the influence by local shear fault on the in-situ stress state along the shotcrete lined high pressure tunnel of the Upper Tamakoshi Hydroelectric Project. A detailed as-sessment 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).