Study On Unified Characterization Of Mechanical Properties And Constitutive Parameters Of Sand And Clay

The scale of geotechnical engineering in our country is expanding day by day.More and more large buildings and high-heavy geotechnical projects have made it an inevitable trend to pay attention to and study the relationship between soil stress and strain.In order to ensure the safe and smooth progress of geotechnical engineering construction and avoid geotechnical engineering disasters as much as possible,it is particularly necessary to analyze and study the mechanical properties of geotechnical engineering.The rationality of the analysis of soil mechanical behavior mainly depends on the rationality of the selected model and parameters.my country has a vast territory and a wide range of geotechnical materials,and the soil layers are often composed of multiple soils.However,the soil constitutive models proposed or improved or innovated by most scholars usually only focus on the mechanical properties of a certain kind of soil.To discuss,only simulate the mechanical behavior of a specific kind of soil,which is not convenient for the application of complex engineering geological conditions.In this paper,a series of systematic conventional triaxial tests are carried out on the mixed soil made of Fujian standard sand,silt and clay in Suzhou area,non-cohesive soil and cohesive soil to analyze the mechanical properties of general geotechnical materials under normal pressure.Based on the existing research results,through the analysis of the upper and lower loading surface models,the model related parameters are systematically explained,and the constitutive parameters are uniformly analyzed and fitted according to the upper and lower loading surface models,and constitutive calculations are performed.Through simulation and comparison,the commonality of geotechnical materials is shown,and the feasibility of the upper and lower loading surface model system to describe the mechanical behavior of general geotechnical materials is verified.The research results of the thesis include the following points:1.The triaxial test results of different soils show that the deviator stress-axial strain relationship curve of Fujian standard sand under normal pressure conditions shows strain softening characteristics,and the shear dilatancy trend is in the shearing process;silt,clay,and the mixed soil prepared with sand and silt,according to the mass ratio of 0.5,shows the characteristics of strain hardening and shrinkage in shear.2.The peak stress ratio of sand is affected by the initial state of sand and the pressure conditions.The residual stress ratio of sand,silt,clay,and mixed soil with a mass ratio of 0.5 is basically not affected by the initial void ratio and confining pressure.3.The isotropic consolidation curve and critical state curve of sand,silt,clay,and mixed soil with a mass ratio of 0.5 are exponentially attenuating,and the fitting relationship of the consolidation curve conforms to the relationship e=a-b(lnp)~c,the fitting relationship of the critical state conforms to the relationship e=a-b(lnp).Compared with silt clay and clay,the consolidation curve of sand is more difficult to converge.4.The mechanical parameters determined according to the concepts of the superloading and subloading can describe the general mechanical behavior of sand,silt,clay,and mixed soil with a mass ratio of 0.5.The applicability of the model to uniformly describe the mechanical behavior of general geomaterials is verified.