Study On Numerical Simulating Creep Mechanism Of Tunnel Surrounding In Softrock Stratum

The increasing tunnels have to go throughout more complicated soft rock stratum, and support and the stability of tunnel in soft rock layer become much more difficult, so understanding the creep deformation mechanism of surrounding rock is the first step for exploring the stability of tunnel. However, based on creep characteristics curves of them under uniaxial compression in different water content conditions, mudstone creep model is selected and its mechanical parameters are ascertained. The creep mechanism of tunnel surrounding is also simulated depending on these parameters by FLAC3D. Several creep mechanisms are made as following:1、Analyzing the uniaxial creep characteristics curves and the numerical fitting curve, the results show that with water content increasing the rock modulus and viscosity coefficient lower and creep displacement and creep rate increase.2、Numerically simulating creep deformation characteristics curves of viscoelastic and viscoelastic-plastic tunnel surrounding reveals that creep rate is maximum while it is excavated and it enters the attenuation creep stage and steady creep stage. With surrounding rock deeper, creep deformation and creep rate decrease in turn. 3、The stress of viscoelastic surrounding rock has an adjustment period at the beginning, and then varies slowly while it the steady creep stage. Hoop stress value of tunnel surface is the maximum, and its concentrative factor tends to2. Viscoelastic-plastic rock has a peak hoop stress whose location is the boundary between elastic region and plastic region Plastic zone increases all the time in the initial creep stage, and no longer expand when it reaches the steady-state stage.4、With water content increasing, the deformation and deformation rate of surrounding rock increase, and the plastic zone increases. Sudden change in deformation occur when water content increase in the creep process. It is equivalent to an additional force applied in the surrounding rock. In order to maintaining the stability of tunnel engineering in soft rock, the water adverse impact on the surrounding should be controlled.