Research On Deformation Law And Optimization Design Of Supporting Structure In Deep Foundation Pit

Since entering the 21 st century,China's economy has developed rapidly.The urban population has increased dramatically,and transportation problems have become increasingly prominent.Therefore,China has been vigorously developing rail transit construction.Metro stations are generally constructed in the center of the city,therefore,the stability of station foundation pits has a major impact on the safety of the project.That is why the selection of supporting structures for foundation pits is very important.This paper studies the internal support of deep foundation pit supporting structure,discusses the deformation law of supporting structure in deep foundation pit and the optimal design of support and protection.The work carried out in this paper and the results achieved are as follows:(1)The types and scope of support for deep foundation pit support system are summarized,and the deformation characteristics of support system are described.The types of support structures in deep foundation pits,design optimization theories for deep pit support design,and deep foundation pit support are introduced as well as structural displacement algorithm,calculation of surrounding ground settlement,etc.(2)Analyzed the deformation law of foundation pit support based on the monitoring data of deep foundation pit support: With the excavation of foundation pit,the horizontal displacement of the enclosure structure increases with the excavation depth,and the overall shape is small at both ends and the shape of the middle is large.The maximum horizontal shift position gradually moves down to the middle of the pit.The surface settlement around the ground is a "groove type" distribution,and the axial force of the supporting shaft is gradually increasing.(3)Using the deep foundation pit support software--Lizheng,the overall stability,anti-overturning stability and anti-uplift stability of the pit were checked.The internal force and displacement change law of the foundation pit supporting structure are analyzed,and the overall stability of the foundation pit is obtained.The design of the supporting structure is reasonable.(4)Using MIDAS/GTS to simulate the deep excavation process,the simulation results are in good match with the monitoring results.The simulated value of surface settlement is smaller than the measured value,and the lateral displacement value of the envelope matches with the measured value,except that the supporting axial force at the extended corner of the foundation pit changes greatly,the supporting axial force of the standard section is in accordance with the measured results.This model simulates the feasibility of excavation.(5)Using MIDAS/GTS software to simulate the influence of changes in the number of supporting elements,supporting spacing,and supporting stiffness on the lateral displacement of the wall and the settlement of the ground outside the pit.It is concluded that increasing the number of supporting paths,supporting spacing,and supporting stiffness within a certain range can significantly control the lateral deformation of the envelope structure and the surface settlement deformation outside the pit.