| The national economy is developing at a rapid pace.The number of permanent residents in first-and second-tier cities is also increasing.The original public transportation system in some cities is no longer able to satisfy people’s travel.At the same time as the ground transportation continued to improve,the development of underground transportation came into being.The subway was very good to alleviate the traffic pressure.The subway lines were almost completed within a few years from planning and construction to putting into use.However,the subway construction involves many deep foundation pit excavation projects.There are many engineering safety hazards worthy of our attention.It is of great practical significance to study the deformation law of deep foundation pits.This paper takes a metro station in Guangdong as the engineering background,and uses theoretical calculation,numerical simulation and construction monitoring to study the deformation of the foundation pit during the excavation of the deep foundation pit of the metro station.The main research contents and results are as follows:(1)Organizing and collecting engineering materials,detailing the project,engineering geology,hydrogeology and construction monitoring,and briefly analyzing the monitoring data of the deep foundation pit of the metro station,providing detailed information for the theoretical calculation and numerical simulation of the deep foundation pit of the subway.(2)The Midas/GTS finite element software is used to simulate the deep foundation pit of the metro station.The simulated deformation results are basically consistent with the construction monitoring and analysis results.The maximum displacement position of the retaining pile in the standard section of the foundation pit is between 1/3 and 2/5 of the length of the pile from the top of the pile..The maximum horizontal displacement of the enclosure pile at the end of the shield well is smaller than the maximum horizontal displacement of the standard section and appears at the 7m position.(3)Reasonable numerical simulation has certain guiding significance for the construction of deep foundation pit of subway.On the original foundation pit model,the analysis of construction stage is adopted,the construction stage of blank group is set,and the influence of lifting position of the trolley on the deformation of foundation pit is analyzed.(1)The hoisting position is 2 m,5 m and 10 m from the foundation pit respectively.Corresponding to the blank construction stage,the maximum horizontal displacement of the enclosure pile increases by 2.38%,2.22%and 1.37% respectively.The influence of the bulge value at the bottom of the foundation pit is smaller than that of the blank construction stage,and the maximum increase of the ridge value relative to the previous stage is 0.658‰,0.573‰ and 0.504‰,respectively;(2)When hoisting work,the effect of temporary dismantling of internal support is relatively close and all within the safe range.However,it can be seen from the results that the temporary removal position is more inclined to remove the support within the non-section position of the lifting point and the maximum horizontal displacement value of the retaining pile caused by temporary removal of the inner support cannot be ignored.;(3)The hoisting position is the shield well end and the standard section 5m away from the side of the foundation pit,and the corresponding maximum horizontal displacement value of the enclosure pile is 5.31% and 12.57% respectively compared with the blankconstruction stage,and the shield well enclosure structure is obviously stronger than the Standard section. |
