Study On Failure Mode And Construction Scheme Adaptability Of Shallow-buried Extra-large-span Tunnel

With the development and utilization of urban underground space,the subway tunnel has the characteristics of complex terrain and large span in some special parts.The existing projects have shown that such tunnels have a large disturbance to the stratum during construction,and the deformation of the stratum often has a significant overall sinking tendency,which caused a more sudden damage.This brings many problems to the design and construction of the tunnel.Thus,this paper mainly carried out the following work:(1)The failure mode and regularity of surrounding rock in shallow buried tunnel under unsymmetrical pressure are studied.Taking the rupture angle as the research index of the tunnel failure mode,the formula of the rupture angle considering the tunnel section size and topographical characteristics is derived.Based on the formula,the law of rupture angle varying with tunnel section size and topographical characteristics is analyzed,and the corresponding relationship among tunnel failure mode,surrounding rock pressure and rupture angle is established.(2)Through the combined application of the shceme decision theory,an evaluation model for the adaptive comparison of tunnel construction schemes is established.The model is applied to the whole process of excavation-disassembly of the three-lane tunnel of Liangmaoshan Station of Shenzhen Metro Line 10.The results show that the evaluation model can clarify the subtle differences of different schemes through mathematical algorithms,thus providing a scientific basis for determining the optimal construction scheme.(3)In order to verify the applicability of the optimization scheme in practical engineering,the three-dimensional finite element simulation is used to study the mechanical properties of the whole process construction of the tunnel with shallow buried depth,unsymmetrical pressure,and extra-large span.The results show that the surface subsidence,vault settlements and horizontal convergence meet the requirements,and the numerical results agree well with the monitoring data,indicating that the optimization scheme is feasible.