Influence Of Concrete Bracing On Ground Road By Cover And Dig For Concrete Support Of Subway Station With Fine Silty Sand

With the rapid development of Wuhan urban economy in China,the increase in the size of the city has accelerated the rapid increase in population.More and more motor vehicles have caused traffic deterioration and even traffic congestion and congestion,resulting in serious traffic accidents and casualties.The utilization of space in many cities has gradually decreased,and it has been unable to meet people's needs.Coupled with the serious environmental pollution in the city and the reduction of green vegetation,these problems have caused people's travel problems.Therefore,subway construction has gradually become an effective way to slow down traffic congestion on the ground.In this paper,the Xujiapeng shed water-rich silt powder land layer subway station No.5,No.7 is replaced by a full-cover excavation method.The ABAQUS finite element software numerical simulation calculation and on-site measurement analysis are used to make water-rich silt.Analysis and optimization of the influence of the raft support on the road during the excavation of the foundation pit during the excavation of the foundation in the silt layer station.The main research contents and conclusions are as follows:(1)According to the change of No.5 and No.7 of Xujiapeng Metro Station in Wuhan,a finite element numerical calculation model was established through ABAQUS,and the influence of the truss support on the cross-section settlement and bending stress of the road was simulated.The analysis shows that the settlement of the cross section of the road is gradually reduced before the excavation to the temporary raft support.After the completion of the raft support construction and the completion of the main structure,the settlement of the cross section of the road suddenly increases until it drops rapidly.However,the bending stress of the pavement gradually increases,and the completion of the negative two-layer excavation body gradually slows down until it stabilizes.It also shows that as the deep foundation pit is further excavated after the excavation is continued until the completion of the negative one-story floor slab,the restraining ability of the temporary support to the ground displacement is basically replaced by the lower layer of the lower layer structural middle plate.The road surface settlement control effect is general.It is also proved that the underground continuous wall and the structural floor are not only part of the main structure,but also the main structure to restrain the displacement of the formation and the settlement of the road surface,and the supporting effect of the temporary concrete support is gradually weakened with the increase of the excavation depth.(2)Better control of urban road pavement settlement outside the foundation pit enclosure.In the actual construction process of the entire subway station,the actual measurement data and the feasibility of the model establishment were compared and analyzed.From the comparison of the cross-section of the road surface,we find that the settlement value near the foundation pit side is the largest.With the direction away from the foundation pit,the settlement value gradually decreases and tends to be stable.The cumulative value of the settlement of the cross-section tends to be basically consistent with the simulated value.The model is established.(3)An unsupported finite element model was established.The analysis showed that under the condition of(without)temporary raft support,the additional bending stress change of the pavement during construction and the final settlement of the pavement,the analysis showed that there was(no)concrete support to the pavement.The settlement control effect is weak.The longitudinal additional bending stress value produced by the excavation of the deep foundation pit is small,but the lateral additional bending stress value is large.Compared with the case without the temporary raft support,the temporary raft support can effectively reduce the additional bending of the road surface stress.(4)Based on the comparative calculation and analysis of the previous section,the additional bending stress control effect on the lateral and longitudinal directions of the pavement during the excavation process is more obvious.Therefore,the SMW method is used to optimize the raft support,and the finite element model is used to control the additional bending stress value and settlement of the pavement during the excavation process.After pre-supporting the advance construction of the temporary raft support,it was found that the final settlement value of the surface was not obvious.After the temporary support and super-strength and reinforcement,the lateral bending stress value of the road surface during the excavation process is significantly reduced.It shows that the optimized raft support can restrain the lateral bending stress of the road surface and further reduce the settlement on the road surface.