Study On The Evolution Of Mechanical Properties Of Surrounding Rock By Coupling Stress Field With Deformation Field

Mechanical properties and parameters of rock mass have to be considered in engineering design and construction, especially in large-complex undergroud projects. Before excavating, the mechanical properties and parameters of rock mass can be acquired through site survey, experiments and numerical analysis, etc. However, surrounding rock and mechanical properties would also be changed with the variations of occurence environment of surrounding rock after excavating. Whether engineering excavation methods and structure of rock mass can be adapted this changes or not is determining the stability of engineering structure and the security of the project. So how to address this problem is a key issue considered by researchers before project design. The mechanical properties and parameters of surrounding rock determining accurately not only relates to the selection of excavation schemes, construction measures and supporting design but also relates to the stability of surrounding rock and the safety of the project.In this paper, we present one of methods of back analysis, called back analysis of coupling stress field with deformation field, to calculate the mechanicis parameters of surrounding rock from the early stages of the excavation to present, based on the fields of stress and deformation. The main research contents of this paper are as follows:(1) Initial geostress field is determined accurately. Fitting initial geostress field of the dam area based on the measured data of geostress and deformation, and then fitting initial geostress in the area of hydropower plants by using the boundary stress and the measured data of geostress and deformation in the plant area of this hydropower station.(2) Dynamic evolution laws of surrounding rock under excavation conditions. The underground caverns are excavated according to engineering design and supporting of the underground caverns after acquiring the initial geostress field in the area of powerhouses. And finally, we show the evolution raws of the stress and deformation of surrounding rock after excavating by numerical simulation based on the actual measured data of stress and deformation.(3) Based on the evolution raws of above stress and defromation of surrounding rock, the mechanical parameters of surrounding rock are acquired by using back analysis of coupling stress with deformation.