泾阳Q2黄土剪切带微观结构研究

Study on micro-structure of slide-zone of Jingyang Q 2 loess

黄土地区滑带土剪切过程中的微观结构特性研究是黄土滑坡滑动机制的研究重点。针对目前研究中滑带土微观分析尺度单一且对剪切过程中的土体矿物组分分析研究几乎没有的现状。文中基于自主研发的分离式环刀纯剪切仪,采用剪切试验和扫描电镜试验相结合的方式,开展了47.5μm剪切位移下黄土剪切带的多尺度(微米级到毫米级)结构的微观结构与矿物特性表征。结果表明:在仅施加47.5μm位移下,剪切缝已完全贯穿,最大缝宽155.95μm,最小缝宽11.5μm,形成了良好的导水通道。剪切缝中的矿物在剪切作用下,矿物颗粒脱离原来的位置并且在剪切缝中被挤压,揉搓,剪破,变成更小的矿物颗粒;摩擦作用使得剪切缝两侧剪切面的微小矿物颗粒被揉搓脱落,剪切缝宽变大,在剪切缝两侧颗粒的矿物属性无法对应。剪切缝中有团聚体形成骨架支撑的现象,显示剪切缝在形成过程中不仅仅存着滑动摩擦,还存在着颗粒的滚动摩擦。文中所观察到的颗粒的滚动摩擦现象为解释滑坡,如远程高速滑坡的滑动机制提供了新思路。

The microstructure characteristics of slip zone soil during the shearing process is the focus of research on the mechanism of loess landslides.Due to the facts that the microstructure analysis of slip zone soil only has a single scale and there was nearly no research on the analysis of mineral composition during shearing,this paper explored the characteristics of the multi-scale(micron to millimeter)structure and the mineralogical characteristic of loess shear zone under 47.5μm shear displacement based on the separated ring knife pure shearing instrument developed by ourselves and scanning electron microscope(SEM),using the shear test and scanning electron microscope tese.The results show that:by applying only 47.5μm displacement,the shear crack has been completely penetrated.The maximum and minimum seam width is 155.95um,11.5μm,forming a good water guiding channel.It was found that under the shearing action,the mineral particles in the middle of the shear joint were removed from the original position and the frictional resistance was increased in the shear joint to change into the mineral particles.It issqueezed,smashed,cut and turned into smaller mineral particles.The mineral particles are separated from the original position in the shear fracture,but the mineral properties of the particles on both sides of the shear fracture can not be matched.The fact that aggregates form skeleton support in the shear joint shows that there exist not only sliding friction but also rolling friction of particles in the process of shear joint formation.The examination of rolling friction of particles provides a new idea for explaining the sliding mechanism of landslides,such as long-distance high-speed landslides.