Mechanism Analysis of Local Collapse in an Underground Powerhouse Based on Strength Reduction FEM and DEM

Abstract

Large collapse of underground house of a hydroelectric power station happened while excavation of the top arch. The volume of collapse was up to 5000m3. With consideration of the field geological conditions and practical construction, by strength reduction finite element method (FEM) and discrete element method (DEM), the process of collapse is simulated, which is compared with the field monitoring data. The mechanism of instability failure is analyzed. Some conclusions are obtained. Firstly, the development of fractured weak zone β80, faults, joints and fissures above the top arch are the basic factors to induce this collapse. Secondly, abrupt blasting without supporting is the direct factor. So collapse of underground house can be avoided by reinforcement and supporting on the geological weak zone in time.