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

Study of meso-damage and macroscopic shear performance of silty clay-concrete interface under freeze-thaw cycles

为了探究冻融循环作用对粉质黏土-混凝土界面剪切性能的影响,进行不同冻融循环次数条件下的粉质黏土-混凝土界面直剪试验,界面区土体扫描电镜试验(SEM)及粉质黏土上表面电子显微镜试验。宏细观相结合,探究冻融循环作用下界面区土体的细观损伤及粉质黏土-混凝土界面的宏观剪切性能,并考虑法向应力及土体初始含水率的影响。试验结果表明:在细观层面,界面区粉质黏土的孔隙在冻融循环作用下逐渐发展,且界面区土体的黏聚性逐渐降低,界面区粉质黏土的孔隙率与冻融循环次数正相关,土颗粒间的接触方式逐渐由面-面接触转变为点-面接触及点-点接触;在宏观层面,粉质黏土-混凝土界面的剪切性能在冻融循环作用下逐渐劣化,粉质黏土-混凝土界面的抗剪强度、黏聚力及内摩擦角均与冻融循环次数负相关,但冻融循环作用不会改变粉质黏土-混凝土界面剪切应力-位移曲线的应变硬化形式。基于室内试验结果,宏细观相结合,探究冻融循环作用下粉质黏土-混凝土界面剪切性能的劣化机制,为季冻区土-混凝土界面的剪切性能研究提供了参考依据。

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.