Research On Space Effect Of Tunnel Surrounding Rock Deformation

Surrounding rock deformation is an important reference index for reflecting the structural stability and instability characteristics after the excavation of the underground engineering. It will cause the surrounding rock burst and internal stress changes. Due to the bearing capacity of surrounding rock and the remaining peak strength after destroyed and considering the spatial effect of surrounding rock of its elastic-plastic deformation which has the characteristics of secondary releasing, surrounding rock supporting structure will reach a new equilibrium state by several times in the release of displacement. Present research which consider the effect of advancing excavation face is still rare, loose zone of surrounding rock stress and strain calculation is not yet perfect. The excavation surface affects area is limited by the surrounding rock mass of surrounding rock and the displacement releasing is divided into three stages.This article set about from the basic mechanism of deformation of surrounding rock basing on the elastic-plastic theory and doing theoretical calculation on the stress and displacement of surrounding rock after excavation of the tunnel. Using numerical simulation software to simulate the process of tunnel excavation, sum up the basic law of space effect. The specific research contents and results are as follows:(1)Take axisymmetric circular tunnels as an example,calculate the stress and deformation of surrounding rock in the M–C yield criterion;analyze the damage of surrounding rock. Simplify the excavation disturbance as single degree of freedom vibration;The influence factors of deformation and failure of surrounding rock is analyzed.(2)Elaborate the space effect theory for further content and do a process simplification. This article do a detailed analysis of effects of space curve and discussed the supporting time;analysis supporting interaction considering the effect of space surrounding rock supporting;calculate under the rule of D–P and H–B considering the space effect of the mechanical parameters of surrounding rock loose circle;forecast the changes of parameters of surrounding rock caused by space effect.(3)Under the condition of elastoplastic,full face excavation model is established by using finite element software MIDAS. The data of vault subsidence and lateral displacement which located before or after the working face when the excavation face was pushed to advance. By compared with the simulation results, it shows that the excavation distance for 1~2 times the cavity diameter range, excavation time in 5 to 10 days the vault subsidence increase quickly, then flatten out.This article provided the calculation method of stress and displacement under different yield criterion and the calculation method of tunnel deformation calculation provide the more convenient access to obtain the surrounding rock loose in general. The research of excavation face space provides the reasonable support distance and time and provide reference for optimization of supporting.