Study On Constitutive Model Of Unsaturated Soil In The Wide Suction Range

The suction is an important reason for the complex properties of unsaturated soil,and existing research has confirmed that suction has a significant impact on the strength and deformation characteristics of unsaturated soil.Existing experiments have shown that with the continuous increase of suction,soil failure will transform from hardening characteristics to softening characteristics,and even develop into brittle characteristics.Correspondingly,the deformation of soil will also develop from shear shrinkage to weak shear expansion,further leading to strong shear expansion.Although a large number of theoretical models for unsaturated soils have been developed,most of these models focus on the mechanical behavior of soil under low suction,and models describing the deformation and strength characteristics of soil under high suction and even wide suction are still very limited.Based on the concept of disturbance state,this article establishes a constitutive model suitable for the strength and deformation characteristics of unsaturated soil in the wide suction range.The main achievements are as follows:(1)The elastic model of unsaturated soil in the wide suction range was studied.Considering the influence of matrix suction,void ratio and confining pressure,a calculation method of elastic shear modulus of unsaturated soil in a wide suction range is proposed.Through data validation and comparison,it is concluded that the calculation method of elastic shear modulus proposed in this paper has the advantages of few parameters,ideal prediction results and a wide range of applicable matrix suction.(2)Based on the concept of disturbance state,ideal elastic-plastic models of dry soil and saturated soil were selected to represent the relatively complete state and widey adjusted state,respectively.A new disturbance function was proposed,and a wide suction range unsaturated soil model was constructed,which can better describe the strength and shear characteristics of the soil.The model was validated using literature experimental data,indicating that the prediction results of the hardening,softening,and brittle response of the soil within the wide suction range are relatively ideal.(3)Based on the perturbation state theory,the ideal elastic-plastic model of dry soil and the modified Cambridge model of saturated soil were selected to represent the relatively complete state and widey adjusted state,respectively,and a constitutive model of unsaturated soil within the wide suction range was constructed.The model was validated using literature experimental data,indicating that the prediction results of the strength and deformation characteristics of unsaturated soil within the wide suction range are relatively ideal.