Analysis Of Structural Redundancy In The Demolition Of Metro Foundation Pit Support

In the field of civil engineering,redundancy is considered to be the ability of a structure or member to resist continuous collapse.The research on continuous collapse failure of superstructures at home and abroad is relatively complete,and there are many research results on improving the continuous collapse resistance of structures.It is proposed that redundancy can be used as a judgment condition for continuous collapse resistance,and continuous collapse failure of foundation pits is a common The foundation pit safety accidents have not attracted enough attention and lack of relevant redundancy research.At present,the research on the redundancy of the foundation pit support system is mostly based on the design stage,and the research methods are mostly based on the layered excavation of the foundation pit.The demolition method is used to support the "full support" state.The system conducts redundancy research,and there are few studies on the dismantling and supporting stage of the foundation pit supporting structure.In order to study the redundancy of the foundation pit supporting system under the condition of dismantling and bracing,the following research was carried out on the foundation pit using the layered and segmented excavation method:(1)The internal force and deformation of the foundation pit supporting structure were calculated using the F-SPW7.0 design software for the deep foundation pit supporting structure,and the internal force and deformation characteristics of the foundation pit supporting structure under different working conditions were analyzed.The horizontal deformation of the supporting structure is larger when the three supports are supported,and this working condition is the most unfavorable working condition of the supporting member.(2)The three-dimensional finite element model was established through Flac3 D,and the simulated excavation conditions were divided according to the actual excavation conditions.The internal force and deformation of the foundation pit using the layered and segmented excavation method were analyzed.The results show that the deformation of the foundation pit was in a safe range during the excavation simulation.(3)By comparing the actual monitoring data with the simulation data of the finite element model,the difference between the simulated value and the actual monitoring value is analyzed.The analysis results show that the model has good accuracy,and the next step can be studied based on this model.(4)Based on the finite element model under the condition of disassembly and support,using the method of dismantling components and the calculation formula of redundancy,the redundancy of the supporting system after the failure of single or multi-channel supports is studied,and the angle of redundancy is determined The key support of the support system under the condition of disassembly and support,an optimized scheme for adjusting the pre-loaded axial force of the support is proposed for the case where the redundancy of the support system is the most unfavorable after the single-channel support fails.It is recommended to perform redundancy analysis on the design and monitoring of the deep foundation pit engineering of the subway.