| China is a country dominated by mountainous terrain.Tunnel construction schemes in mountainous areas have attracted more and more attention.Therefore,it is of great significance to accurately evaluate the stability of tunnel surrounding rocks.Based on the Huangyu Tunnel Project and the results of investigation and experiment,the stability of surrounding rock of the tunnel is studied by means of multiple methods.The main conclusions are as follows:(1)By using fuzzy matter-element evaluation method,selecting six parameters such as uniaxial saturated compressive strength as classification index and combining subjective and objective weights of each index,the surrounding rock of Huangyu Tunnel can be divided into grade III,grade IV and grade V.The proportion of surrounding rock sections is 22.56%,47.07% and 26.5% respectively.The result of BQ method is consistent with that of fuzzy matter-element evaluation method.(2)3DEC is used to simulate the stress and displacement changes of surrounding rock after excavation.The stress release of vault roof and vault bottom is obvious.The stress of arch shoulder and vault foot is the most concentrated,and the critical stress of falling block is close to 0.After excavation,the numerical simulation results show that the grade III surrounding rock is stable,followed by grade IV surrounding rock,and the stability of grade V surrounding rock is the worst.The maximum vertical displacements of the vault after excavation are 5.6mm,17.3mm and 36.4mm respectively.By monitoring the displacement around the tunnel,it is found that the stable settlement of grade III,IV and V surrounding rock sections is 3.6mm,6.1mm and 13.5mm respectively.The influence distance of excavation deformation is about 14 m,24m and 48 m respectively.(3)Based on 3D EC built-in fish language,a program for calculating the area of shear slip zone is compiled.The area of shear slip zone is taken as the criterion for determining tunnel stability.Combined with orthogonal test,it is found that in the comprehensive properties of joints and rock blocks,the order of influence degree of each factor on tunnel stability is joint in-plane friction angle > rock elastic modulus > joint normal stiffness > joint cohesion.(4)Through orthogonal test,it is known that the main controlling factor of stability of fractured rock mass and surrounding rock failure is shear failure between joints.In lining construction,support measures should be taken to strengthen the cohesive force between cracks.On the other hand,for the surrounding rock with low elastic modulus,advance geological prediction should be conducted,and support parameters should be modified or strengthened in time to ensure the safe construction and the safe use of the tunnel. |
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