Influence of supporting opportunity on stress characteristics of soft-weak surrounding rocks in highway tunnels

In order to fully understand the influences of different supporting opportunities on the mechanical characteristics of soft-weak surrounding rocks in highway tunnels,the developed geomechanical model tests as well as the simple and practical tools and methods adopted in tunnel excavation are used.The highway tunnel model tests are systematically launched based on the idea of construction after loading.The influences of supporting opportunity on the surrounding pressure,the size and the distribution of shear stress of lining in soft-weak rocks in highway tunnels are studied.The results show that the influences are notable,and a 200 mm reserved deformation is reasonable when the excavation diameter is about 12 m under different stress fields in soft-weak surrounding rocks(the elastic modulus of surrounding rocks is 210 MPa).Under such conditions,the shear stress and the surrounding stress are lower,and the distribution is also comparatively homogeneous,which is the most beneficial to lining force.In the actual project we should strengthen monitoring and measurement,sum up experience and choose the best opportunity to achieve smaller stress of lining as far as possible.