Study On The Mechanical Properties And Constitutive Model Of Loess Under Different Stress Paths

Natural loess has typical structural properties,and the stress path has a great influence on the mechanical properties of natural loess.This paper m ainly conducted four indoor stress path tests on structural loess,analyzed and summarized the stress-strain relationship and the volume-strain relationship under different stress paths;gave the expressions of damage rate and shear contribution rate,A binary medium constitutive model and its strength criterion of saturated structural loess are established.The specific conclusions are as follows:(1)In the triaxial compression test,structural loess exhibits strain softening and volume expansion characteristics under low confining pressure;it exhibits strain hardening and volume shrinkage characteristics under high confining pressure.The remolded loess exhibits strain hardening and shrinkage characteristics under low confining pressure and high confining pressure.In the triaxial extension test,the structural loess showed strain softening and bulk expansion characteristics.In the triaxial equal-average elongation test,structural loess showed softening and volume expansion characteristics;in the triaxial equal-average compression test,structural loess showed hardening and volume shrinkage characteristics.(2)The strength characteristic curves of structural loess under four stress paths are drawn and analyzed.Its strength value is in order:strength value of triaxial compression test,strength value of triaxial extension test,equal average compression test strength value,equal average extension test strength value;in the strength characteristic curve,the strength characteristic curve when the stress is lower The relationship is nonlinear,and the strength characteristic curve is linear when the stress is high.And analyze the cohesion and internal friction angle of the specimen during the shearing process.(3)The failure mechanism of structural loess was studied,the existing binary medium model was revised,the full and incremental binary medium model and the calculation method of the damage parameters in the formula were given,and the saturation was derived.Binary medium model of structured loess.The results of the conventional triaxial test are used to verify the calculation results of the incremental binary medium model,which shows its rationality.(4)According to the shear strength criterion of the binary medium,the relationship between the shear contribution rate and the minimum principal stress is introduced,and the existing shear strength criterion of the binary medium is revised.The strength values of the triaxial compression test and the triaxial extension test are used to verify the theoretical calculation results of the binary medium’s shear strength,which shows its rationality.