Estimation Of Initial Ground Stress In Underground Powerhouse And Stability Analysis Of Surrounding Rock

Initial ground stress reflected the natural stress condition before excavation. It is not only one of the important factors that affect the mechanical properties of the rock, but also the force which lead to excavation deformation and destruction of rock mass. Identifying the initial ground stress is crucial for the stability analysis of engineering slope, rock mass around underground cavern. Especially, in the construction of large-scale geotechnical engineering, whether the reliable initial stress could be obtained will directly affect reliability and security of engineering design. So how to properly simulate initial stress field of rock has always been an important issue of geotechnical mechanics.Including gravity action, tectonic movement, faultage, mechanical parameter, topography and so on, the influencing factors of initial ground stress are more complex. Vast engineering practices indicate that gravity action and tectonic movement are major forming factors of initial ground stress. So the initial ground stress could be thought to the superposition of self-weight stress and tectonic stress. In this article, the inversion method of the initial ground stress field is mainly aimed at tectonic stresses, and can work in the condition in which tectonic stresses are linear along depth.According to existing inversion methods and basic distribution laws of ground stress, based on systematic analysis and summary of previous research results, considered the formation of ground stress and influence of topography, an inversion procedure of ground stress is proposed. In this procedure, non-linear mapping relation between rock mechanics parameters and deformation of excavation is obtained by using RSM and FEM. An example of underground powerhouse of baishan was taken. Then, by the definition of the objective function, the inversion problem was changed into optimization. Finally, genetic algorithm was used to optimization calculation, and tectonic stress of rock mass was got.By the comparison between predicting deformation and the monitoring deformation, the validity of this inversion method was proved. Based on inversion results and some measured mechanical parameters of rock mass, on two conditions, the excavation processes was simulated by FEM software. The results show that deformation during excavation was not constrained effectively by the support, but extension of plastic zone was controlled.