Study On Bearing Capacity Of Variable Stiffness Piles-diaphragm Wall Combined Foundation Under Lateral Load

The variable stiffness piles-diaphragm wall combined foundation is a new combined foundation based on the development of closed underground continuous wall and variable stiffness group pile foundation.The upper wall is mainly used to bear the lateral load,and the lower piles is coordinated to change the pile stiffness.The new foundation has the characteristics of large overall rigidity and uniform force.Compared with the common lateral load foundation,the variable stiffness piles-diaphragm wall combined foundation can reduce the amount of the base material under the same lateral load.At present,there are few studies on the variable stiffness piles-diaphragm wall combined foundation,and its bearing performance and deformation characteristics are not yet clear.Based on the school-enterprise cooperation project,the paper studies the bearing capacity and deformation law of the combined foundation through theoretical calculation,indoor model experiment and numerical analysis,and discusses the factors such as changing the pile number,pile length and pile diameter.The main research results are:(1)Based on the interaction concept of pile,diaphragm wall and soil,the paper calculate the force magnitude and failure form of the variable stiffness piles-diaphragm wall combined foundation,and propose the formula for checking the anti-overturning and anti-sliding of combined foundation.According to the “m” method,the MATLAB calculation program is used to investigate the effects of changing the number of piles and pile diameter on the deformation of the combined foundation.The results show that with the increase of the number of piles(pile diameter),the displacement of the combined foundation is gradually reduced,and the bending moment of the pile body is gradually increased.When the number of piles(pile diameter)reaches a certain value,the number of piles(pile diameter)is increased.The horizontal displacement decreases and the trend becomes slower.(2)Through the indoor model experiment,the paper discusses the force deformation law of the variable stiffness piles-diaphragm wall combined foundation under lateral load.The results show that the force and deformation of the combined foundation become larger with the increase of the load;the force and deformation of the wall on both sides of the combined foundation are obvious;In a certain lateral load range,the earth pressure increases with the increase of lateral load.The type increases,when the load reaches a certain value,the soil is destroyed and the earth pressure is reduced.(3)Using Plaxis-3D finite element software for numerical simulation,the main research is to change the influence of the number of piles,pile diameter and pile length on the combined foundation deformation and internal force.The results show that within a certain range,better deformation and deformation performance and economic benefits can be achieved by adjusting the stiffness of the lower pile of the combined foundation.