Experimental Study On Critical State Characteristics Of Structural Soil

Aiming at the silty clay encountered in the construction of Wangfujing transfer station,the failure mechanism and evolution law of soil structure are explored,and the appropriate constitutive model is constructed to provide theoretical basis for the subsequent numerical analysis.However,it is difficult to directly obtain the structural soil in nature.Many scholars use the method of artificial preparation of structural soil to simulate the cementation and the arrangement of soil particles in structural soil.In this paper,the remolded silty clay is mixed with a certain proportion of cement and salt.According to the characteristics of silty clay,a "dry powder sample preparation method" is used to prepare structural silty clay,and the cement content is used to describe the cementation content of structural soil,so as to reflect the structural changes of structural soil.In this paper,saturated structural clay is taken as the research object,a large number of tests are carried out on the conventional triaxial apparatus,and based on the original geological survey report,the sample preparation ratio which can reduce the strength of undisturbed soil sample is found out,The deformation and strength characteristics of saturated structured silty clay only considering cementation are obtained.The results show that the critical state line of saturated structured soil is higher than that of saturated remolded soil,and the higher the degree of structural cementation,the higher the critical state line.In order to accurately describe the cementation strength,macropore and high strength characteristics of natural structural soil,a constitutive model suitable for structural soil should be established.Therefore,on the basis of the existing unified hardening model of overconsolidated soil,a state parameter considering the cementation characteristics is introduced,and the three-dimensional method is used to transform the above model into a three-dimensional elastic-plastic model.The new state parameters can effectively simulate the shrinkage and strain softening of soil under different cementation states.The state stress ratio which can reflect the structural strength is introduced into the hardening parameters,so that the whole hardening rule can consider the influence of structure.Based on the GNST criterion transformation stress method,the stress expression of the model is extended.The generalized model can describe the stress-strain relationship under true triaxial test.Through the comparison of previous experimental results and model prediction,the threedimensional structural constitutive model can better reflect the structure of soil,and has strong applicability and application value.This paper has 46 pictures,4 tables and 69 references.