| The improvement of the city’s comprehensive transportation system has long-term significance for the development of the city.As a part of urban rail transportation,the subway has an unparalleled advantage in alleviating the traffic pressure which the city faced.The construction sites of subway stations are often surrounded with numerous buildings and complex environments.Therefore,Deformation control of foundation pits is particularly important.This paper uses MIDAS GTS/NX software to analyze the deformation of the foundation pit of a subway station in Changchun as the research background.In this process,By changing the bracing and support parameters of the foundation pit to discuss its effect on the foundation pit.The main content of this paper and the results obtained are as follows:(1)Summarized the current research status of foundation pit deformation at home and abroad,analyzed the influencing factors of foundation pit deformation,introduced the stability calculation method of foundation pit,discussed the prediction and calculation method of foundation pit deformation,and the common use of foundation pit Support methods are introduced;(2)Through software simulation calculation to the foundation pit,it is found that the surface settlement deformation of the foundation pit is "groove" shape,and its deformation is the largest along the longitudinal middle of the foundation pit;(3)According to the calculation results,it can be found that in the initial stage of excavation of the foundation pit,the largest horizontal displacement of the bracing structure happened at the top position.In the eighth to the eleventh stage of the excavation of the foundation pit,the maximum horizontal displacement of the retaining and structure is The position gradually moved downwards and finally stayed at a point which distance the surface 11.29 m.The pit bottom uplift deformation value of the foundation pit gradually increases in the early stage of excavation,and reaches the maximum value of 0.01552 m in stage 6.The uplift deformation is smaller at the boundary position of the foundation pit at the bottom of the foundation pit,and is bigger at the middle position of the bottom of the foundation pit;(4)The differences in the deformation of the foundation pit under the four conditions of 22.771 m,25.771 m,28.771 m and 31.771 m in the soil depth of the bracing structure are discussed.The results show that with the increase of the soil depth of the retaining structure,the ground settlement deformation value of the foundation pit,the horizontal displacement deformation value of the retaining structure all have a significant decrease;(5)The differences in the deformation of foundation pits without anchor cable,one-layer anchor cable,three-layer anchor cable,five-layer anchor cable and seven-layer anchor cable are compared and analyzed.The calculated results show that the increase in the number of layers of anchor cables has a positive effect on the deformation control of the foundation pit.However,the seven-layer anchor cable has a limited amount of deformation control compared to the original five-layer anchor cable;(6)The influence of anchorage position on deformation is discussed.Choose to cancel one and two layers of anchor cables,two and three layers of anchor cables,three and four layers of anchor cables,and four and five layers of anchor cables to compare the differences between them.The results show that the anchor cables at the middle and lower positions which cancel three and four layers of anchor cables affect the deformation of the foundation pit are most obvious,at the same time,the position of the anchor cable has little effect on the uplift deformation of the foundation pit.In various analysis situations,the difference of uplift deformation is less than 1mm. |
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