Lateral Compression Model Of Foundation Soil And Its Settlement Analysis Method

The calculation of foundation settlement is one of the important decision bases for the evaluation of foundation bearing stability.The reasonable calculation value of foundation subsidence will make the decision of engineering design,construction and operation more reasonable.It is of great theoretical significance and engineering application value to explore its more reasonable calculation method.Based on the summary and analysis of the existing research status of lateral limit compression test,compression analysis model and settlement calculation method of foundation soil,the indoor side limit compression test of clay and non-clay soil is carried out in this paper.Furthermore,a new lateral compression analysis model is proposed,which can reflect the characteristics of initial compression,unloading springback and recompression of soil.On this basis,a new method for calculating the settlement of foundation soil based on pore medium model is established,which can reflect the change of three-dimensional stress field and deformation modulus.The rationality and effectiveness of the established model and analysis method are verified by the comparative analysis of engineering examples.Through the study,the paper draws the following conclusions:(1)The stress-strain relationship between macroscopic soil and microscopic soil particle skeleton is established by introducing porosity,and the microscopic stress-strain relationship of unearthed particles is determined by linear elastic Hook's law,and then the macroscopic stress-strain relationship of soil is established.Then the simulation analysis method of soil side limit compression process is established by using the relationship between macroscopic deformation and pore ratio of soil and the deformation characteristics of soil under side limit condition.Based on the fact that the lateral deformation of soil does not occur in the process of lateral compression test,but only the axial deformation,and the axial stress and strain are in accordance with hyperbolic relationship,the e-p curve model of initial compression of soil is established.The pore ratio of initial and recompressed soil is the same when the compressive stress tends to infinity,and the relationship between compressive stress and strain is still hyperbolic when the recompression consolidation test is carried out under the condition of side limit,the curve model of soil recompression is established.(2)According to the characteristics that the macroscopic deformation of soil canbe divided into two parts: unrecoverable and elastic recoverable,it is assumed that the plastic deformation is caused by the void part and the elastic deformation is generated by the pore skeleton part.Based on this,a macroscopic deformation analysis model of soil which can distinguish unrecoverable and recoverable elastic micro deformation is established,and the micro deformation analysis method of ideal void and pore skeleton is discussed,the analytical model of initial compression of side limit of soil is established;based on the characteristic that the strain of gap part does not change with the decrease of stress during unloading spring back,the analytical model of lateral limit unloading spring back of soil is established.Combined with the analytical model of side limit initial compression,it can reflect the influence of stress path and loading and unloading cycle on the compression deformation process of soil;the deformation of gap part in the process of recompression is changed and the newly generated unrecoverable deformation part is relatively reduced,the analytical model of lateral limited recompression of soil is established,which can reflect the influence of stress history on the compression deformation process of soil by combining with the analytical model of lateral limited initial compression.(3)Based on the analysis of the force and micro-deformation of foundation soil,the pore media analysis model reflecting the relationship between the apparent deformation mechanical parameters of soil mass and the actual deformation mechanical parameters of grain skeleton was established.Introducing the idea of graded loading,an analytical model for the influence of additional stress,initial stress or stress history on mechanical parameters of foundation soil deformation is established.It can be seen that the relationship between poisson's ratio of foundation soil and its particle skeleton poisson's ratio is related to the deformation caused by stress.And their influence law can be described by the established influence rule analysis model.Then an improved hierarchical summation analysis method of foundation is established by using the hierarchical summation method to reflect the nonlinear characteristics of mechanical parameters of soil deformation.The results show that the deformation mechanics parameters of foundation soil change with the change of buried depth and additional stress,which avoids the dependence of the traditional foundation settlement analysis method on the compression test curve of foundation soil.(4)Adopting the analysis method of combining macro and micro.Using Walsh's formula and equivalent inclusion theory,the relationship between the deformationmodulus of foundation soil,the deformation modulus of granular framework and the porosity was determined.Based on the nonlinear characteristics of the deformation modulus of foundation soil and the idea of graded loading,two kinds of recursive variation relations of the deformation modulus of foundation soil before and after the action of the volume stress of foundation are constructed.Then,using the idea of hierarchical summation and incremental generalized hooke's law,the settlement analysis method of foundation soil considering the change of deformation modulus and the influence of three-dimensional stress under the action of initial ground stress(or buried depth)and additional stress is obtained.In order to avoid the use of foundation soil compression test curve or the foundation static load test curve,and the applicable conditions of foundation settlement analysis method is expanded.(5)The results of indoor compression tests verify the rationality of the soil lateral compression analysis model established in this paper,which reflects the characteristics of soil initial compression,unloading rebound and re-compression,etc.The comparative analysis of four engineering examples verifies the validity of the foundation soil settlement calculation method based on the pore medium model and reflecting the change of three-dimensional stress field and deformation modulus.In addition,combined with the results of the indoor compression test and the practical engineering case,the parameter sensitivity of influencing factors was analyzed.