Settlement Monitoring And Numerical Simulation Analysis Of Super-deep And Large Caisson Foundation

With the rapid development of national economy,the infrastructure construction of our country has also taken a new step.Especially in the field of bridge construction in China,in recent years,new large-scale river-crossing and sea-crossing bridges have been built and opened to traffic,which has refreshed the world record of bridge construction time and again.Ultra-deep large caisson foundation is widely used in pier foundation and anchorage foundation of long-span bridges because of its large embedded depth and bearing area,strong integrity,good stability,and the ability to withstand large vertical and horizontal loads.However,there are not many research results on the bearing characteristics of super-deep caisson,such as settlement prediction,internal force distribution of caisson structure and stress distribution of foundation soil under upper load and high confining pressure of deep soil.Based on the background of the new Hutong Yangtze River Bridge project,this paper monitors the caisson foundation’s settlement of main tower’s pier 28 after the foundation’s bottom being sealed.The bearing characteristics of caisson foundation are numerically simulated and analyzed by ABAQUS,and the ultimate bearing capacity of large cross-section deep-embedded rectangular caisson foundation under different foundation width and depth is studied by finite element modeling.The main research contents and conclusions are as follows:(1)ABAQUS,a large-scale general applying finite element software,is used to simulate the construction condition of the 28# pier’s caisson foundation of Shanghai-Tong Yangtze River Bridge’s main tower after sealing the caisson’s bottom,and the load-settlement curve is obtained,which is consistent with the field monitoring result.The model is used to simulate the working condition of the caisson foundation under the designing load which will be imposed after the bridge enters the operating stage,and caisson foundation’s corresponding settlement value of the load is obtained.(2)By using the above finite element model,without considering the settlement limitation,the ultimate bearing capacity and safety factor of the foundation can be obtained by applying the load increment method on the basis of the design load until the foundation is destroyed,and the strain and stress distribution of caisson and foundation soil are analyzed.(3)The finite element model is used to analyze the stress distribution,plastic strain development,the influence depth of the vertical stress of the foundation soil and the internal force distribution of the caisson structure under the ultimate load.(4)25 groups of large cross-section rectangular caisson foundation models with different sizes and embedded depths were established by using finite element software ABAQUS.The ultimate bearing capacity of large cross-section rectangular caisson foundation was calculated by load increment method,and the variation rule of foundation soil’s ultimate bearing capacity with the changing of foundation’s width and depth is analyzed.