Study On Deformation Characteristics Of Deep Foundation Pit In Deep Soft Soil Layer Considering Time And Space Effect

With the rapid development of urban construction,foundation pit engineering is becoming more and more complex,especially in the deep foundation pit in soft soil stratum,which has the characteristics of large deformation of the retaining structure and obvious time-space effect,which brings many problems to the design and construction.Based on the deep foundation pit project of Dadun station(hereinafter referred to as Dadun station)in deep soft soil layer of Foshan Metro Line 3,this paper analyzes the deformation characteristics of deep foundation pit based on the time-space effect.The main research contents are as follows:1.Based on the comprehensive discussion of the research results of deep foundation pit deformation at home and abroad,especially the deformation of deep foundation pit in soft soil layer and its time-space effect,this paper puts forward the research topics and research contents for the time-space effect of deep foundation pit deformation in deep soft soil layer.2.The deformation mechanism and time-space effect principle of foundation pit excavation are described,and the deformation calculation of retaining structure considering time-space effect is analyzed.Based on the field monitoring data of Dadun station deep foundation pit,the influence of time-space effect on the horizontal displacement and surface settlement of diaphragm wall in the process of foundation pit excavation is analyzed.3.Based on the simplex method of inverse analysis of m-value of horizontal resistance coefficient proportion coefficient,this paper proposes to divide the same soil layer into several sub layers,and take the weighted average value of m-value after optimization of each sub layer as the final optimization result of this layer of soil.Taking the deep foundation pit project of Dadun station as an example,the inverse analysis of m-value of each layer of soil is carried out,and the value range of m-value considering space-time effect is obtained.4.The modified Mohr Coulomb constitutive model is used to establish the threedimensional finite element model of diaphragm wall and foundation pit excavation of Dadun station deep foundation pit project,to discuss the value of soft soil strength parameters considering the time-space effect,and to analyze the influence of diaphragm wall thickness and horizontal support number on the time-space effect of diaphragm wall deformation and ground surface settlement.