Experimental Study And Simulation Study On The Horizontal Force Characteristics Of Root Caisson Foundation

With the rapid development of economy and society,ensuring transportation has become the top priority of the country’s economic development.In the face of my country’s rich water system environment,accelerating bridge construction can better alleviate the existing traffic tension.At present,the development of bridge construction projects in China is relatively rapid,and the construction technology and technology of many large bridges have reached the world’s leading level.Among them,the commonly used foundation forms in the existing large-scale bridge engineering include caisson foundation,caisson foundation,pipe pile foundation,enlarged foundation or multiple combined foundation forms,etc.As the construction conditions become more complex,on-site technicians have innovatively proposed the design concept of root caisson.The root caisson foundation is to add a horizontal root key around the traditional caisson foundation.During the load process,the root key drives the soil in the surrounding area of the caisson foundation to jointly bear the load,thereby increasing the overall bearing capacity of the foundation and increasing the foundation The stability.This paper mainly uses pre-designed indoor scale model test schemes to study the horizontal bearing performance of root caisson foundation in sand under different conditions,and uses finite element simulation software to verify actual working conditions.The main research content as follows:（1）Through the model test,comparative analysis of the horizontal bearing capacity of the caisson foundation under different conditions such as the number of root keys,the number of root key layers,the length of root keys,the position of root keys,and the spacing between layers of root keys,etc.The test results show that increasing the number of root keys and layers can limit the horizontal displacement of the root caisson foundation and reduce the overall bending moment and shear force of the body,which can improve the horizontal bearing capacity of the root caisson foundation.The length can drive a wider range of soil between piles,and the internal force law of the well remains the same and the change value is small;increasing the vertical load can compact the soil at the bottom of the foundation and improve the soil strength,so it can effectively reduce the horizontal The displacement and the internal force of the wellbore have a certain effect on the bearing capacity.（2）The failure mode of the caisson foundation belongs to rigid failure,and the horizontal ultimate bearing capacity of the foundation is mainly controlled by the strength of the surrounding soil.According to the theory of soil pressure,the self-weight stress of soil increases correspondingly with the increase of foundation depth.Deep soil can provide greater soil resistance to prevent overturning and rotational damage of the caisson foundation,which is very important for limiting the horizontal displacement of the foundation and improving the horizontal limit of the foundation.Bearing capacity has a significant effect.（3）The finite element analysis method is used to establish the model body corresponding to the test conditions,and the whole process of horizontal loading of the caisson foundation is simulated.The simulation results show that the law of the simulation results is consistent with the law of the scaled model test,and by analyzing the lateral friction resistance of the root bond,it can be seen that the stress at the distal surface of the root bond is relatively large,the stress at other corners is relatively small,and the middle root bond is in the middle.It plays the main bearing role in the process of horizontal loading.