Study On 3D Foundation Bearing Capacity Of Ultra-Deep And Large Round-ended Caisson Foundation

With the rapid development of large-scale bridge projects in my country,the requirements for foundation depth and size are getting higher and higher.At present,there is a large gap between foundation bearing capacity theory and engineering practice,and further research is needed on the foundation bearing capacity of ultra-deep and large foundations.Taking the Changtai Yangtze River Bridge as the backing project,the main channel bridge is the main pier caisson foundation of the double-tower,double-cable-plane,double-layer road-rail dual-use long-span cable-stayed bridge as the engineering background.Further study the bearing capacity of the foundation.This paper mainly uses theoretical analysis and derivation,numerical simulation test and centrifuge model test to carry out in-depth research on the three-dimensional foundation bearing capacity of the ultra-deep and large caisson.The main research contents are as follows:（1）According to the existing theoretical formula and standard method of foundation bearing capacity,the bearing capacity theory of the three-dimensional circular foundation is derived,and the Hankel transformation method for solving the axisymmetric problem in elastic mechanics space is used to solve the bottom of the circular foundation by MATLAB software Corresponding to the limit load P_1/4at the depth of 1/4 times the diameter,refer to the calculation formula for the bearing capacity of the strip foundation,and use the shape factor to establish a simplified formula for the limit load P_1/4of the three-dimensional circular foundation,based on the area The principle of equivalence,this formula can be extended and applied to the calculation of foundation bearing capacity under any shape.（2）On the basis of theoretical analysis,the finite element numerical simulation analysis method was used to carry out numerical simulation experiments on strip foundations and circular foundations respectively.The results showed that the numerical solution of the strip foundation bearing capacity is completely consistent with the analytical solution.The numerical solution of the bearing capacity of the shaped foundation is in good agreement with the result of the formula.It can be seen that the calculation formula of the three-dimensional foundation bearing capacity proposed in this paper is reasonable and reliable.（3）According to the engineering characteristics,the centrifuge model test plan and the finite element numerical simulation test are designed to comprehensively evaluate the overall settlement deformation and the bearing capacity of the foundation under the engineering load.The results show that after the upper load of 280,000 tons of the caisson foundation is applied,the average soil settlement of the centrifuge model test prototype foundation is 203.16mm;the finite element numerical simulation foundation settlement is 217.12mm.When the load reaches the ultimate load,the load The settlement curve has no obvious inflection point,and the settlement change is very stable;the centrifuge model test and the numerical simulation test show that the results of the allowable foundation bearing capacity of the foundation bearing capacity are basically the same,which are 2.1 MPa and 2.24MPa respectively.（4）According to the actual stress state of the soil at the bottom of the caisson,the value of the compressive modulus of the deep soil is studied,and the settlement analysis of the caisson foundation under constant load is carried out using the standardized layered sum method.The results show that The settlement value calculated from the actual stress state for the compression modulus is 218mm,which is consistent with the centrifuge model test and finite element numerical simulation calculation results,and the foundation bearing capacity calculated by the three-dimensional bearing capacity formula is 1.82MPa than the centrifuge Model tests and finite element numerical simulation results are small,and the foundation bearing capacity meets the design requirements.It can be seen that the results obtained by the three-dimensional foundation bearing capacity formula in this supporting project are reasonable.Figure[92]table[23]reference[54]...