Finite Element Analysis For The Bearing Capacity & Deforming Behavior Of Layered Soil Under The Shallow Foundation Subjected To The Vertical Load

The bearing capacity and settlement of the shallow foundation on soil is the important subject of the soil mechanics and foundation engineering. The current Chinese foundation design code GBJ7-89 use limit equilibrium theoiy with elastic soil stress distribution to give Out bearing capacity design value calculating fonnula and use elastic soil model to evaluate foundation settlement. According to the above theories, code GBJ7-89 gives the correlative terms. But these do not accord with the practical mechanism of loaded soil below the shallow foundation and the elastoplastic property of natural soil so defects exist. With the development of the compute technology and the soil constitutive model. the finite element method (FEM) gradually becomes a comprehensively used numerical method in geotechnique engineering. The paper uses the coupled numerical method by combine the finite element method (FEM) with the infinite element method (IEM) to analysis the strength and deformation of the soil under the shallow foundation. The corresponding three-dimensional analytical program is devised by FORTRAN9O computer language. In the program. the used soil constitutive models include Duncan-Chang constitutive model, K-G model, modified Cambridge model, Yin Zongze model with two yield surfaces and Drucker-Prager elastoplastic model. With the program, the paper analysis the uniform soil condition and the layered soil condition separately. To uniform soil condition, the p-~s settlement curve of the center point at the bottom of the shallow' foundation and the different depth of the soil plastic zone in different load grade and the ultimate bearing capacity of the foundation are analyzed. To layered soil condition, by the comparisons of the p-s settlement curve of the center point at the bottom of the shallow foundation and the different style of the soil plastic zone in different load grade and the ultimate bearing capacity of the foundations of the six different layered soil, some conclusions of the layered soil condition are achieved. The ANSYS large finite element soft ware elastoplastic analysis is also used in the above all soil conditions with Drucker-Prager model. And the foundation capacity design value and the settlement of the soil in the above all soil conditions are calculated by Chinese foundation design code GBJ7-89 at the same time. The comparisons of the results in the analysis of theIIdevised program and the ANSYS software and the code GBJ7-89 show that the finite numerical method used in the paper can combine the analyses of the bearing capacity and the settlement of the foundation at the same time and can obtain the nonlinear settlement of the foundation under different load grade and the development of the soil plastic zone and the ultimate bearing capacity of the foundation and can imply the practical mechanism of loaded soil below the shallow foundation under the vertical load.