Numerical Simulation Analysis Of Deep Foundation Pit Support In Soft Soil Area Based On MIDAS-GTS

In recent years,with the rapid development of society and the continuous improvement of economic benefits,the rapid development of urban construction,including large-scale municipal projects are also increasing.In order to solve the problem of urban land shortage,the excavation depth of foundation pit is getting deeper and deeper,and the supporting forms are becoming more complex and diverse,which makes the supporting structure design and excavation construction scheme of deep foundation pit engineering become one of the important research topics in the field of construction engineering.This paper takes a deep foundation pit project in Jiangdong District of Ningbo City as the research background.This project is located in a water-rich soft soil area.There are some problems in the design of supporting structure and excavation construction scheme.On the basis of relevant theory,the above problems are deeply explored by using finite element software MIDAS-GTS,in order to achieve good economic and social benefits.The main research contents are as follows:(1)Understand the hydrogeological conditions and the selection of supporting structures in the area where the foundation pit project is located.According to the construction procedure of the foundation pit,establish three-dimensional finite element models under the conditions of dewatering and non-dewatering respectively and calculate them.(2)Contrastive analysis of simulation results:settlement of soil around foundation pit;change of foundation pit floor uplift;vertical displacement of foundation pit column pile and horizontal and vertical displacement of retaining pile;internal force of supporting structure;settlement of adjacent buildings of foundation pit;verification of corner effect of foundation pit,etc.(3)The monitoring data in the construction process are summarized and compared with the simulation results to verify whether the finite element numerical simulation has guiding significance for the actual project.By comparing the simulation results and monitoring data with the simulation results,the following conclusions are drawn:(1)The influence of each dewatering on the internal force of the internal support beam is much greater than that of each excavation of the foundation pit;each dewatering of the foundation pit will lead to a small drop in the pile of the foundation pit,and each excavation will lead to a large uplift of the pile of the foundation pit,and the final uplift value is much larger than the settlement value of the surrounding soil layer;the settlement value of the top of the retaining pile is slightly larger than the horizontal displacement value of the pile body;and the settlement value of the top of the retain Displacement value,etc.(2)Under the condition of dewatering and non-dewatering,the former causes the foundation pit bottom heave,the settlement of surrounding buildings and the internal force of internal support are larger than the latter,so dewatering can not be ignored in foundation pit engineering in water-rich soft soil area.(3)Whether dewatering or not,the settlement value of the soil layer in the longitudinal and transverse middle area of the foundation pit is much larger than that in the corner area of the foundation pit,and its size is about three times,which verifies the existence of the corner effect in the rectangular foundation pit.(4)There is a slight difference between the field monitoring data and the numerical simulation results,but the trend of the simulation data is basically in line with the actual monitoring situation,so the pre-risk assessment of the actual project can be carried out by the finite element analysis software.Figure[58]table[9]reference[51].