The Research On Stability Of Shallow Tunnel Surrounding Rock And The Effect Of Initial Supprot

With the rapid development of China’s public transport,the number and type of tunnel works are increasing.In practical engineering,due to the complexity of terrain and geological structure of uncertainty,the tunnel is often in a biased state.In order to study the surface angle and depth of the tunnel influence on the tunnel stability,In this paper the tunnel with span 10 m and height 7m as the research object,the research work was carried out by means of model test and numerical simulation.It provides a reference for the judgment and construction of tunnel stability under the condition of shallow buried bias.The main contents and conclusions are as follows:(1)In the model test,the variation of stress is most obvious at 0 times of the tunnel span,and the stress of the arch foot is smaller than the arch waist.When the surface angle over 30 degrees,the stress at both sides of the arch is obvious,surface angle of 30 degrees is the tunnel bias trend becomes obvious turning point;when the tunnel depth increases,both sides of the tunnel arch foot stress value increases,both sides trend gradually tend to be consistent,when the depth is more than 25 m,the left arch waist stress begins to decrease,both sides of the tunnel stress variation tends to be symmetrical.(2)With the increase of the inclination angle,the tunnel bias effect is gradually enhanced.When the ground inclination angle is greater than or equal to 30°,the bias effect becomes obvious.The stress and displacement fields of the surrounding rock are gradually increased with the increase of the buried depth of the tunnel.When the depth of the tunnel is more than 25 m,the bias effect of the tunnel is obviously weakened,but the tunnel is still affected by the bias.(3)V grade tunnel of surrounding rock with a dip angle of 30 degrees.The center diaphragm method has the best effect on restraining the deformation of surrounding rock and reducing the area of plastic zone,the second is reserved core soil method,the step method the worst,the center diaphragm will be the drawbacks of the construction of the center diaphragm method,excavation side of the need to install temporary support structure,resulting in longer duration.