Experimental Study On Wet-shear And Wet-shear Properties Of Unsaturated Loess

There are many engineering problems in more and more engineering construction in loess area,and wet shear of unsaturated loess is one of the key problems.Natural unsaturated loess has remarkable structure and water sensitivity due to its own aerial structure system with large pores.The strength deformation of unsaturated loess varies greatly under disturbance,charge and water immersion.For example,the shear failure of a slope with unchanged stress can occur only because of humidification.In the tunnel structure,the arch of the tunnel will be damaged due to the flood and collapse deformation.Therefore,it is of great significance for practical engineering to conduct experimental research with true triaxial apparatus.In this paper,humidification-shear and shear-humidification tests under different net consolidation confining pressures,different matric suction differences and different principal stress parameter B values are conducted to compare and analyze the similarities and differences between the two loading paths.(1)Matric suction measurements of the dehumidification process of the undisturbed and remolded loess were carried out with the unsaturated soil consolidation instrument and soil-water characteristic curves were obtained.The analysis shows that the matric suction decreases with the increase of water content,and the variation degree is different under different water content.When the water content is high,the variation is obvious,but with the decrease of water content,the variation becomes smaller and smaller.It was found that the moisture content of undisturbed loess was higher than that of remolded loess under the same matric suction.(2)The true triaxial humidification-shear test shows that the consolidation deformation increases with the increase of net consolidation confining pressure and decreases with the increase of net consolidation confining pressure.The increase of net consolidation confining pressure can improve the strength and stability of soil mass.The increase of matric suction can also improve soil strength and reduce soil deformation.The increase of b value can reduce soil strength and increase soil deformation.(3)The true triaxial shear-humidification test shows that the deformation of soil under the pellet stress is small,but with the increase of the ball stress,the soil deformation is large.When the matric suction difference was 200-50kPa,the soil mass produced the greatest deformation.This indicates that the water sensitivity of soil is the strongest under the stress condition.(4)By comparing the experimental analysis under two loading paths,it is found that the total deformation of the soil under the humidification-shear path is large,and the experimental results under the two loading paths are less and less as the ball stress increases.