Research On Deformation Characteristics And Optimization Design Of Deep Excavation In Houyan Station Of Dalian

With the continuous development of China’s economy,people have put forward higher requirements for the utilization of space in large cities,and urban buildings have gradually expanded to higher and deeper levels.In this paper,based on the actual engineering of the deep excavation of Houyan Station of Dalian Metro Line 5,on the basis of actual construction conditions,engineering geological data and on-site measured data,the Midas GTS NX finite element software is used to simulate the dewatering and excavation of the foundation pit.During the process,the deformation characteristics of the foundation pit during the dewatering and excavation of the foundation pit were studied in detail,the deformation law of the foundation pit was summarized,and the corresponding optimization measures were put forward to provide some technical support and experience for the design and construction of the deep excavation engineering of similar stations.The main research contents and results are as follows:(1)Carry out on-site monitoring research on the deep excavation of Houyan Station,conduct statistical analysis of monitoring data,and draw curve change graphs.According to the on-site monitoring data,the surface settlement and deformation curve around the foundation pit is distributed in a spoon shape,and the maximum settlement value of the surface around the foundation pit of this project is about 0.026%H(H is the excavation depth of the foundation pit).The horizontal displacement of the enclosure structure is in the shape of a mirror image "c",which is large in the middle and small at both ends,and the maximum horizontal displacement of the enclosure structure is about 0.043%H(H is the excavation depth of the foundation pit).The monitoring results show that the surface subsidence and the horizontal displacement of the enclosure structure at the standard section of the foundation pit are slightly higher than those at the end well,and the monitoring frequency of the standard section of the foundation pit can be appropriately increased.(2)Using the method of numerical simulation,a three-dimensional seepage-stress coupling numerical calculation model was established to simulate the actual foundation pit dewatering and excavation process.The variation law of the displacement field reveals the deformation characteristics of the deep excavation project of Houyan Station.Comparing the simulation calculation results with the measured data,it is concluded that the simulation calculation results are basically the same as the measured data,which verifies the feasibility of the simulation calculation.(3)Change the embedded depth of the enclosure pile,the diameter of the enclosure pile,the diameter of the steel support,the preloaded axial force of the rigid support,the vertical spacing of the support,and the thickness of the strongly weathered rock to explore its influence on the deformation of the foundation pit.The sensitivity analysis of the above 6influencing factors is carried out,and the sensitivity relationship of the influence of the foundation pit deformation of the foundation pit is obtained as follows: the embedded depth of the enclosure pile>the diameter of the enclosure pile>the pre-axial force of the steel support>the diameter of the steel support>Support vertical spacing>Thickness of strongly weathered rock.(4)According to the sensitivity relationship between the actual characteristics of the project and the influencing factors of the foundation pit deformation,an economical and reasonable optimal design of the support system is proposed.