Research Of Bearing Capacity Of Root Foundation Based On Numerical Analysis

Root foundation is to add several root keys to the side wall of the pile on the basis of the original equal section pile,and to increase the vertical bearing capacity by increasing the contact area between the side wall of the pile body and the soil so as to drive the soil to resist the displacement of the foundation.Because of the complexity of the underlying mechanism,the understanding of the bearing characteristics of the root foundation is not fully understood.The theoretical research process of root foundation lags far behind the application of actual engineering.This paper combines the existing research results at home and abroad,using finite difference software analysis as a means to carry out the research on the vertical bearing characteristics of the foundation.(1)Establish a finite difference model of root foundation and a finite difference model of common piles,and perform vertical foundation bearing performance analysis.The results show that,compared with ordinary piles,root foundation can significantly reduce the settlement of the pile and improve the ultimate bearing capacity of the vertical compressive force.Under the vertical load,the displacement field of the soil is wavy in the range of one root key length from the side of the pile body,and the dislocation of the pile and soil is inconsistent.The existence of the root makes the root foundation have a significant change in bearing characteristics such as axial force,pile friction resistance,ultimate bearing capacity,etc.,compared to ordinary piles.The horizontal force acting on the lower surface of the root of each layer appears as an “L” type,that is to say,the maximum surface tension under the root appears at the connection between the root and the pile.The trend of the tension on the lower surface of the root along the distance from the pile is gradually weakening.The lower surface gradually begins to compress,and the compressive stress increases first and then decreases.When designing the root foundation,the root should focus on the stress of the connection between the root and the pile.(2)Establishing a root foundation finite difference model with different horizontal layouts of root,different numbers of roo,and different length of root systematically analyses the impact of performance with the horizontal arrangement of root,the number of root,the length of root,etc..The results show that different horizontal layouts of root have little effect on the vertical ultimate bearing capacity of the root foundation,but the root has a shielding effect on the side friction resistance of the pile when it is arranged at equal angles compared to the quincunx arrangement.It is more obvious that the root should be arranged in a plum shape as far as possible.The increase in the number of root will increase the vertical ultimate bearing capacity of the root foundation,but excessive setting of the root will reduce the economic efficiency of the root foundation.The length of the root can increase the ultimate bearing capacity of the foundation,but if the root is too long,the root may be locally damaged.(3)Analyze the load transfer mechanism of the root foundation and study the failure modes under the pressure state.The results show that the failure mechanism of the root foundation is related to factors such as the arrangement of the basic root,the soil distribution around the pile and its deformation modulus,and the nature of the bottom soil of the foundation,and the stiffness of the root.The strength and stiffness of the root and the strength of the pile are the factors that directly affect the bearing capacity.The structural damage of the radical foundation is divided into local destruction of the root and overall destruction.Combined with the empirical formula,the ultimate bearing capacity formula and settlement calculation of the foundation are deduced.