Characteristics Of Mechanicals And Soil Water For Intact Loess During Wetting Under Triaxial Stress

Loess has strong water sensitivity.The deformation development,strength change characteristics and water-gas permeability characteristics of loess under different changes of wetting and loading are studied,and these studies are combined with the development of modern soil mechanics for unsaturated soils.It is of great theoretical significance and practical value to seek the theoretical support of loess soil mechanics and solve the loess engineering problems.In view of this,the consolidation and drainage triaxial shear test,the constant triaxial stress graded humidification test and the gas seepage test under the condition of triaxial stress were carried out on the intact loess.The deformation,strength and yield characteristics of intact loess under constant suction loading and constant stress humidification are compared and analyzed.The soilwater characteristics and water-gas permeability characteristics of intact loess under constant stress humidification were studied.The main research work and results are described below.(1)Based on the triaxial shear test of controlled suction consolidation and drainage,the influence of suction on isotropic compression and yield characteristics of intact loess is analyzed,and the suction and compressibility indexes(elastic index,compression index,yield stress)are obtained;The influence of suction on stress-strain and critical state characteristics is analyzed,and the relationship between shear strength parameters and suction of intact loess is obtained.The variation characteristics of saturation during isoaxial compression and triaxial shear are analyzed,and the influence of triaxial stress on soil water characteristics is revealed.(2)Based on the constant triaxial stress test during wetting,the relationship between strain and suction under triaxial stress is analyzed,and the effect of triaxial stress on the yield and strength characteristics of intact loess is discussed.The characteristics of wet pressure and wet shear reflected by water sensitivity of intact loess are revealed.The stress-strain and critical state characteristics of saturated intact loess under two kinds of wetting and loding path are analyzed,and the influence of wetting and loding path on the critical state of saturated intact loess is discussed.The modified V-G model of soil water characteristics characterized by saturation and suction under triaxial stress is obtained,and the influence of wetting and loding path on the critical state characteristics of saturated intact loess is discussed.It is revealed that triaxial stress has obvious influence on the relationship between seepage coefficient and suction and saturation,but has little effect on the relationship between relative seepage coefficient and suction ratio and saturation,and can be approximately described by the same humidifying water infiltration function.(3)Based on the gas infiltration test under the condition of triaxial stress,the gas permeability function which directly considers the influence of water content and triaxial stress is put forward,and it is revealed that the triaxial stress has great influence on the relationship between gas permeability coefficient and saturation and volume gas holdup.However,it has little effect on the relationship between relative gas permeability coefficient and saturation and relative volume gas holdup,and can be described by the same gas permeability function which indirectly considers the influence of stress and humidity.It is revealed that the triaxial stress has little effect on the relationship between the ratio of seepage coefficient and saturation,which can be approximately described by the same exponential function.