Analysis On Influence Of Static Load And Overconsolidation Ratio On Bearing Capacity Of Soft Foundation

When the soft clay foundation is designed,the choice of shear strength indexes is crucial.In the traditonal design method the shear strength indexes is gained before the construction of the structure.However,the consolidation of the soft clay foundation will continue due to the incresing upper load along with the construction of the structure,whic will affect the shear strength of the soft clay.On the other hand,differernt foundations have different consolidation history,and the shear strength of different foundation differ from each other due to the consolidation history.Hence,it is necessary to ivestigate the change law of the shear strength indexes under different consodidation and the static deviator stress.Next,based on the large-scale finite element analysis software ABAQUS,the numerical model is computed considering the change law of the shear strength indexes of the soft clay by user subroutine,hence the safety factor of the bearing capacity of the soft clay foundation is computed more accurately.This paper included the following several aspects:(1)The triaxial consolidation undrained shear test is conducted by using the sample of the mucky silty clay.This chapter tend to analysis the changing law of shearing capacity and the shear strength indexes along with the consolidation degree and the axial upper stress.Finally,the formula of the variation of strength index c,? with consolidation degree is put forward in the engineering practice.By means of contrast experiment,the influence of the static deviator stress to the shearing strength is analyzed.(2)Based on the large-scale finite element analysis software ABAQUS,the user subroutine of USDFLD is used to make a secondary development for the material of soft clay according to the Mohr-Coulomb constitutive model,then the shearing strength indexes of the soft clay can change according to the degree of consolidation and the additional static deviator stress,and the change condition will be the foundation of analysis of the soft clay foundation.(3)Aimed at the gravity caisson breakwater,the numerical simulation model of the interaction between the gravity caisson breakwater and the soft clay foundation is made considering the change law of the shearing strength indexes of the soft clay.Through this method,the change condition of the soft clay under different conditions is gained,which will be the first step for the analysis of the bearing capacity of the foundation.Through the contrast between considering the consolidation and not considering the consolidation,the influence of secondary consolidation due to the additional upper load to the safety factor of the bearing capacity is discussed.According to this method,the influence of the factors(thickness in stirring,the width of rubble base,the upper load)to the shearing strength indexes and the bearing capacity is also analyzed.(4)Aimed at the gravity caisson breakwater,the influence of the additional static stress under different consolidation degree to the bearing capacity is analyzed,considering the changing law of the shearing strength indexes by indoor triaxial shear test.Through the contrast between considering or not considering the influence of the additional stress,the vertical and horizontal bearing capacity safety factor is computed under these two conditions.Through large amount of numerical simulation,the result shows that it is very important to consider the consolidation state and the additional stress when we analyze the safety factors of bearing capacity for the soft clay foundation.