Numerical Analysis Of Mechanical And Construction Process Of Circular Assembled Foundation Pit Retaining Structure

The construction of the foundation pit support structure can realize the purpose of convenient construction,shorten the construction period and save the cost.It is widely used in the construction of the shaft in the underground engineering construction such as shield,pipe jacking and so on.Shield,the number of shafts in the project,the construction period is tight,the specifications are single,the environment is complex and the safety requirements are high,and it belongs to the temporary project.After the completion of the project,it is necessary to carry out the dismantling of the supporting structure and the backfilling of the foundation pit.Assembly support structure of the useless.The results of the previous research mainly focused on the strength and force characteristics of a single component or single-layer assembly structure.However,the overall mechanical performance of the cylindrical structural system formed by the combination of the ring and vertical connecting members is still lacking.In addition,the support structure in the construction of the depth of support in the excavation depth of a certain distance(a single excavation depth),the more the lower excavation,after a single excavation has not yet support the poor stability of the temporary,The need to explicitly give a single excavation depth of the foundation pit can maintain a stable maximum excavation depth.Based on the structural characteristics of the assembly support system,the JGJ130-2011 "construction fastener type" is used to build the finite element model of the three-dimensional structure composed of the standard steel plate member,the circumferential preloading member and the vertical connecting member by using the SAP2000 structural finite element program.Steel pipe scaffold safety technical specification "on the assembly support structure in the permanent load and construction load under a variety of combined conditions of the force and deformation of the analysis.The results show that the bearing capacity of the supporting structure under the combined load of unfavorable loads has sufficient safety reserve and can meet the requirements of the specification.Based on the PLAXIS2 D finite element program,the numerical model of foundation pit considering soil-structure-groundwater interaction is constructed.The construction process of layered excavation and stratified support of the supporting structure is analyzed,and the results are analyzed.The depth of the excavation depth is the maximum excavation depth of the foundation pit,and the following conclusions are obtained: In the sandy soil and soft soil layer,the excavation depth of the foundation pit decreases with the increase of the single excavation depth.In the cohesive soil layer,the cohesive force,the internal friction angle and the soil stiffness parameters have a great influence on the maximum excavation depth of the foundation pit.The depth of the excavation depth of the foundation pit Dug depth effect is not obvious.However,in the soft soil layer,due to the greater the depth of a single excavation,the exposed surface of the air more,and the soft soil stiffness is small,prone to deformation,so the temporary surface of the soil easily reach the destruction of the state,Which results in a relatively small value of the maximum excavation depth of the foundation pit in the soft soil layer.