冻融循环条件下粉质黏土-混凝土界面细观损伤及宏观剪切性能研究

In order to investigate the effects of freeze-thaw cycles on the shear performance at silty clay-concrete interface,direct shear tests, electron microscopy tests and scanning electron microscope(SEM) tests were conducted at the silty clay-concrete interface with different numbers of freeze-thaw cylces. The meso-damage of soil in the interface area and the macroscopic shear performance of the silty clay-concrete interface were studied by combining macroscopic and microscopic views. Furthermore,the effects of normal stress and the initial moisture content of soil were also considered. At the microscopic level,the pores of silty clay in the interface area gradually develop and the cohesiveness gradually decreases under the action of freeze-thaw cycles. The porosity of the silty clay in the interface area is positively correlated with the number of freeze-thaw cycles and the contact mode of the soil changes from surface-surface to point-surface and point-point. While at the macroscopic level, the shear properties of the silty clay-concrete interface gradually deteriorate under the action of freeze-thaw cycles. The shear strength,cohesion and internal friction angle of the silty clay-concrete interface decrease with the increasing freeze-thaw cycles but the shear stress-displacement curves are still in strain-hardening form. The deterioration mechanism of the shear performance under the action of freeze-thaw cycles was investigated in combined macroscopic and microscopic views on the basis of laboratory testing results. It provides a reference for the study of the shear performance at the soil-concrete interface in seasonal frozen soil regions.