Reasearch On The Constitutive Model Of Unsaturated Remodeling Loess

The unsaturated soil mechanics has developed rapidly in recent years.The non-saturated soil constitutive model has been an important direction and tool for studying the mechanical properties of unsaturated soils.It has been the focus of scholars at home and abroad.As a typical unsaturated soil,compacted loess is commonly found in engineering construction projects such as artificial foundations and fill slopes.Its special mechanical properties greatly affect the construction of loess areas.Therefore,the stress-strain test of unsaturated compacted loess and the study of unsaturated soil constitutive model have important theoretical and engineering practical significance for engineering construction in loess area.In this paper,the L₆ compacted loess of Yan'an Land Creation Project is selected as the research object,and the basic physical and mechanical parameters of the compacted loess are obtained through relevant experiments.Based on the classical unsaturated soil constitutive model in the literature,the evolution of the unsaturated state variable ?_s in the basic model is improved.Based on this,the confining pressure factor P_ar is introduced,which is more suitable for unsaturated reshaping.The constitutive model of loess.?1?The basic physical parameters of Yan'an L₆ loess and the compression coefficient and springback coefficient of reconstituted saturated loess in one-dimensional consolidation and isotropic consolidation are obtained through experiments.The preparation method of remolded loess samples was optimized,and the advantages and disadvantages of reshaping triaxial specimens in one molding and sub-lamination were analyzed.?2?Combining the existing data with the groping of the test itself,through the experience of communicating with the technicians and teachers and students familiar with the unsaturated triaxial instrument,the operation of a set of GDS unsaturated soil triaxial apparatus is summarized.The process,as detailed as possible,describes the pre-test preparation,sample and instrument installation and test parameter settings,as well as some problems that may arise in the test and corresponding solutions.?3?The unsaturated triaxial tests under different confining pressures and different suction conditions were carried out,and the changes of saturation and volume change in the consolidation stage,the stress-strain curves in the shear stage and the photographs after the shearing of the samples were given.The effects of net stress and suction on the deviatoric stress and volume change of the specimen during shearing were analyzed.?4?The inverse ?_s according to the test results indicates that S_r and ?_s are not simply linear relations,and the normal consolidation lines with different saturations are not equally spaced in the e-lnp plane.Based on the unsaturated soil constitutive model proposed by Zhang et al.,the evolution of the unsaturated state variable ?_s is improved.Based on this,the confining pressure factor P_ar is introduced and the constitutive model suitable for unsaturated remolded loess is derived.