Analysis Of Excavation Of Large Cross Section Tunnel In Rich Water Fault Fracture Zone With Fluid-Structure Coupling Effect

For the high-pressure tunnel in the fault zone,the reinforcement of bad geology and the treatment of groundwater are very important measures.Based on the theoretical analysis,numerical simulation,field test and other methods,based on the actual engineering background,the paper studies the important engineering problems such as different drainage prevention measures and bad geological reinforcement methods,and puts forward the general research results.Similar engineering practice can also provide a reference basis.In this paper,the method of large cross-section tunneling in the water-rich fault zone is studied by theoretical derivation and numerical analysis.The theoretical relationship between the seepage coefficient and the vertical stress is deduced,and the ABAQUS user subroutine was programmed to considering the influence of grouting parameters on the stability of the face in numerical calculation,and the effect of the advanced drainage method was analyzed.The main conclusions are as follows:(1)After a lot of calculations,it is found that if the deep-buried tunnel adopts the method of advanced grouting reinforcement,the plastic zone of the excavated surface is different from that of the shallow tunnel.The plastic zone does not have the tendency to penetrate the surface,and is the type of parabola.The expansion pattern of the soil behind the excavation surface of the deep tunnel is as follows:the plastic zone first appears in the inverted arch,and with the increase of the excavation,the plastic zone also increases,and the plastic zone is further expanded.Adjacenting to the non-grouting area,the grouting area may first appear plastic area,and with the further excavation,the plastic zone of the grouting area extends to the non-grouting area.(2)In this paper,the influence of internal friction angle and cohesion on the stability of excavation surface is studied by changing the internal friction angle and cohesive force of rock mass in a certain range.The calculation shows that the influence of the friction angle and cohesion on the stability of the excavation surface is similar,and the increase of the two parameter can effectively improve the stability of the excavation surface,reduce the safety distance of the tunnel surface stability and the maximum displacement.At the same time,The relationship between the change of the internal friction angle and the maximum displacement of the excavation surface is the concave curve,that is,with the increase of the internal friction angle and the cohesion,the benefit is reduced.Therefore,it is effective to improve the mechanical parameters of rock and soil by grouting to ensure the stability of excavation surface,but the excessive pursuit of rock and soil parameters is lack of economic benefits.(3)In this paper,the influence of the stability on the excavation surface of deep buried mountain tunnel is studied by setting four different drainage holes.The results show that the bottom drain hole can minimize the maximum displacement of the excavation surface when only a single advanced drainage hole is set,but the impact on the safety distance is small;and setting the side drainage hole can effectively reduce the safe distance to ensure the stability of the excavation surface,but the reduce ratio of the maximum displacement of the excavation surface is less than the bottom drain hole and middle drain hole.(4)The actual working condition of the excavation of the double-lane tunnel shows that the stability of the excavation surface is better,when the two tunnels are excavated separatedly.And after the bottom and middle drainage holes are set,the maximum displacement of the excavation surface reduced by more than 50%.