Research On Rheological Properties Of Surrounding Rock And Net Distance Optimization Of Soft Rock Tunnel With Large Deformation And Minor Clear Distance

In order to study the influence of the net distance on the stability of surrounding rock and the safety of the supporting system,and to optimize the net distance of the tunnel,based on the engineering background of a small net distance highway tunnel,combined with the construction site monitoring data,use the large finite element software(ANSYS)to simulate the construction process of the tunnel,and the characteristics of surrounding rock deformation and supporting structure are studied,then,the net distance of small clear distance tunnels is optimized by using analytic hierarchy process,and the results are as follows:1)The main cause for the large deformation of the small clear distance tunnel is weathered tuff of surrounding rock,which is rock crushing and self stabilizing ability is low,large deformation of surrounding rock and support damage phenomenon always appear in excavation process,the cumulative deformation is large and vault settlement is larger than the horizontal convergence2)Through the triaxial rheological test results show that the small clear distance tunnel in weathered tuff has obvious rheological property,by H-K model to describe its rheological properties is more reasonable,the considered flow "and" does not consider the rheological "two ideas of tuff deformation small clear distance tunnel construction process is analyzed with numerical simulation,and compare with the actual detection,Considering Rheological simulation results are closer to the actual project and the numerical simulation model is established;3)Based on the tunnel construction,the settlement,horizontal convergence,support force and surrounding rock stress were simulated,and the numerical and variation characteristics of the small clear distance tunnel under different condition were obtained.Then,the optimal selection of the net distance of the tunnel was obtained by using multi-objective optimization method-AHP.Finally,The net distance of the small clear distance tunnel is optimized,and the reasonable distance of the tunnel is 0.8B.The scientific nature and rationality of the optimization method are confirmed by combining with the actual project.