Analysis On The Spatial Effect Of Foundation Pit And The Effect Of Bottom Roof Uplift In Soft Soil Area

With the rapid development of China's national economy,urban space has become increasingly tense,three-dimensional urban space has begun to be developed as an important natural resources.It can be said that the development and utilization of underground space is the direction of urban construction in the 21st century.Since the 20th century,China's urban subway construction has developed rapidly,at the same time,the subway deep foundation pit project also developed rapidly.Deep foundation pit engineering is a complex interdisciplinary subject,which is related to many factors.It is a systematic project.Although domestic and foreign experts and scholars have carried out extensive investigation on deep foundation pit engineering,some successful experiences have been made,but the theory is not yet mature.Deep foundation pit accident has two main problems:First,deep foundation pit support system instability;Second,deep excavation environmental conditions,both around the safety of facilities,and even lead to serious engineering accidents.The main contents of this paper are as follows:(1)This paper summarizes the research status of the stability and deformation of the foundation pit,and introduces the deformation law of the foundation pit and the deformation relationship between the supporting structure and the surrounding soil.(2)The theoretical analysis of the deformation of the foundation pit is introduced,and the theoretical knowledge of the foundation uplift and the spatial effect is summarized.(3)The influence of the aspect ratio on the spatial effect of the foundation pit is studied by finite element method.The feasibility of the optimization of the foundation pit is verified by the spatial effect.The causes of the deformation of the foundation pit are analyzed,and the numerical simulation is used to study the foundation Influencing factors.(4)The numerical simulation results of the underground space project in the core area of Taihu new town,Suzhou,are calculated and compared with the field monitoring data.The main conclusions are as follows:(1)When the aspect ratio L/B of the foundation pit is less than 2,the design and construction of the foundation pit are more economical in consideration of the spatial effect.When the aspect ratio L/B is greater than 2,the two-dimensional plane analysis is more simple and safe.(2)According to the Terzaghi assumption,the fonnula of the basement uplift influence scope width is deduced,it can be seen from the formula that the width of the influence range of the basement uplift is mainly affected by the embedding depth,width of the foundation pit and the internal friction angle of the soil parameters.(3)The deformation laws and results calculated by numerical simulation can be used to predict the deformation of the foundation pit in the soft soil area.