Study On Stress Characteristics And Surrounding Settlement Of Large Caisson During Sinking Process

In recent years,large caisson foundation has been widely used in many large bridge projects in china.Large caisson foundation as a kind of underground deep foundation are often faced with complex problems: the characteristics of soil are always anisotropic,nonlinear,discrete and uncertainty.The attitude and the velocity of sinking is difficult to control during the sinking process.It is difficult to forecast the sudden sinking and the impact on the surrounding environment.In order to solve the above problems,it is necessary to study the variation law of reaction force,internal force and surrounding soil settlement during the process of caisson sinking.This paper researches on the north anchorage caisson foundation of the suspension bridge at Guanting Reservoir in Huailai,Hebei Province,which is under construction.The sinking process of the caisson is monitored in real time,according to monitoring data and the results of finite element numerical simulation analysis,the variation law of reaction force,internal force and surrounding railway settlement during the sinking process of caisson is studied:(1)By analyzing the measured data of side wall frictional resistance,the variation law of side wall friction during the sinking process is studied,then a new calculation model of lateral friction is proposed according to the theory of mathematical statistics.Finally,several kinds of side wall friction calculation models are compared.(2)Based on the analysis of the internal force monitoring data of the first sinking process,the variation law of the internal force of the caisson is studied.The variation law of the stress of steel bars and the strain of steel plate at the partition wall and the bottom of cutting edge is mainly studied.The finite element simulation analysis of several theoretical conditions that may occur in the sinking process of caisson is carried out at the same time.In the finite element analysis,the calculation model of the side wall friction is based on the new model proposed in the third chapter.(3)Through ABAQUS numerical modeling analysis,the settlement variation law of surrounding railway during caisson sinking is studied.Firstly,the settlement of surrounding railway in the two cases of setting up protective piles and without protecting piles is studied.Then,the influence of these parameters on the settlement of the railway around the caisson is studied by changing the diameter of the pile,the concrete strength and the length of the pile.