Relationship between deformation of surrounding rock and in-situ stress in deep-buried tunnel

With the burial depth from 450m to 800m,the surrounding rock of a iron mine is deformed severely,supports lose their effects and the deformation is lasting.The testing results of in-situ stress shows that these tunnels are under the action of modern ground tectonic stresses with the maximum principal stress of 13～21MPa,and that the general feature of modern ground stress field is that σ_V≥σ_Hσ_h.The surrounding rock of strong deformation belongs to the fissured rock,whose strength is low.The results of FEM analysis show that the maximum stress within surrounding rock is about 40MPa after excavation.According to the analysis,it is considered that the strong deformation of surrounding rock of tunnel from the joint actions of very strong tectonic stress and vertical gravity stress;and that the soft fissured surrounding rock can not bear such actions,which causes continuous large rheological deformation.Engineering practice indicates that usual spouting concrete anchorage wall rock can not meet with the fissured surrounding rock stability under high stresses.Through the analysis of deformation mechanics of surrounding rock and defects of prophase support system,this research finding is of great significance to the reinforcement and repair of surrounding rock of iron mine.