Study On Mechanical Properties Of Expansive Soil Based On High-order Continuous Theory

Expansive soil is a kind of special soil rich in strong hydrophilic clay minerals,and has two characteristics of water swelling and water shrinkage.Expansive soil has the characteristics of "double structure",and its macroscopic deformation characteristics have a direct relationship with its internal microstructural features.Only by comprehensively considering macroscopic and microscopic levels can we truly understand the deformation law of expansive soil and establish a reasonable constitutive model of soil.In this paper,high-order terms and scale influence factors are used to describe the influence of microstructure features on macroscopic performance.High-order continuous theory is applied to the study of expansive soils with the values of scale fator was calculated by experimental study and scale influence laws are studied.(1)It is assumed that the micro-scale effect of expansive soil only needs to consider the volumetric strain gradient.On the basis of the traditional strain gradient theory,the influence of the partial strain gradient is neglected.Only the influence of the volumetric strain gradient is considered,A simplified high-order continuous theoretical model that can be reflected the law of microscale effect of the expansive soil can be derived.(2)Based on the simplified strain gradient model,the displacement fourth-order differential equation with the radius as the variable and the generalized stress-radius relationship in the axisymmetric loading environment are derived in the cylindrical coordinate system,and numerical solution is calculated to study the influence of scale factor on displacement and stress.At the same time,the scale factor calculation formula is derived based on the simplified strain gradient theory,which provides a theoretical basis for the experimental test scale factor.(3)Taking the expansive soil of Dengzhou Road section of the NeiDeng Expressway in Nanyang City as the research object,the deformation test scheme of hollow cylindrical expansive soil with different water content was designed by GDS hollow torsional shear tester.The influence of reference stress and volume strain gradient on the microstructure of expansive soil was studied.The scale factor calculation formula of the derivation is used to estimate the value of scale factor at rate of water content,and the scale influence law is analyzed.