A Model Experimental Study And Numerical Simulations Of The Upheaval Vs. Overall Stability Of Deep Slender Foundation Pits

With the continuous development of municipal engineering in China,the use of deep foundation pit with small plane size and deep supporting structure is increasing gradually,and its safety and economy are also paid more and more attention.It is one of the main factors affecting the stability of foundation pit excavation,but the existing methods are too conservative,and the obvious spatial effect of deep foundation pit barrel type is not very suitable,so the research on the stability of foundation pit deep slender becomes very necessary.On the basis of reading related literatures at home and abroad,this paper puts forward the overall analysis method for anti-upheaval stability and overall stability of deep slender foundation pit,and carries out model test to study the problem of deep foundation pit's anti-upheaval stability and overall stability.Then,ABAQUS software is used to establish the three-dimensional finite element model for numerical simulation.Finally,combined with the model test and numerical simulation,the deep slender antiupheaval stability failure mode and its influencing factors are proposed.The main contents of this paper:1.The model test was carried out to study the influence of the plane size of the foundation pit,the insertion ratio,the stiffness of the retaining structure and the overloading on the anti-upheaval stability and the overall stability of the deep foundation pit.The results show that the stiffness of the supporting structure has little effect on the anti-upheaval stability of the foundation pit,and the plane size of the foundation pit and the excavation depth of the foundation pit have a great influence on the anti-upheaval stability of the foundation pit.With the excavation of foundation pit,the foundation pit is prone to upheaval and stability damage,but it is difficult to take place similar to the overall stability of a wall failure.When overloading of the model test,a part of the pit was extroverted into the pit under the overload of the pit,and the other part of the soil was upwards.The upheaval phenomenon of foundation pit is more obvious than that without overloading under the action of overloading.2.The three-dimensional finite element model of deep foundation pit was established by using ABAQUS software.The influence of plane dimension,soil parameters,ground overloading and the insertion ratio,depth and stiffness of retaining structure on the foundation pit were studied.The failure mode and influence factors of the anti-upheaval stability of the deep slender foundation pit were obtained.3.According to the experimental results and numerical simulation results,the three-dimensional failure modes of two kinds of deep slender foundation pit were put forward,and the concept of composite circumferential axis was put forward,and the partial safety factor of the foundation pit was calculated respectively.Then,the final stability safety factor of the foundation pit anti-upheaval was obtained.On this basis,a large number of parameters were analyzed,and the factors affecting the stability of deep slender foundation pit were obtained.Through the research in this paper,the overall stability and anti-upheaval stability of the deep slender foundation pit are analyzed,and the influence of different factors on the stability of the deep slender foundation pit was obtained.The overall analysis method of deep slender foundation pit is put forward,which provides a theoretical basis for evaluating anti-upheaval stability and overall stability of deep slender foundation pit.