赵家岸滑坡地区马兰黄土物理力学特性试验研究

摘要

Inundating or humidifying process can easily destroy the distinct metastable structure of loess and control its mechanical behavior.This paper analyzes the microstructure of Malan loess at Zhaojiaan landslide area.It uses grain size analysis,scanning electron microscope,and mercury intrusion porosimetry.The results demonstrate that as the loess depth increases from surface to deep,the cementation of clay mineral is increasing gradually,the trellis pores is compressed obviously,and micro-pore is unchanged nearly.Triaxial compression test on loess with different initial water content shows that the strength of loess at top and bottom location decreases with increasing in water content.Since the loess at bottom location has higher clay cementation,its strength is larger than that at top.The cohesion strength parameter c is much more sensitive to water than the internal frictional angle φ.Therefore the strength reduction with depth is caused primarily by the decreasing of c.Water content increasing of loess at the bottom due to rising of ground water level can cause the parts of clay mineral to soften,undermine the cementation between particles,and continuously destruct the microstructure of loess,which resulted in wriggles of Zhaojiaan landslide.%浸水或增湿过程中，黄土特有的不稳定结构极易发生破坏，约束黄土的力学行为特征。通过粒度分析、扫描电镜和压汞实验对赵家岸滑坡地区黄土的微观结构进行分析，得到由上到下黏土的胶结作用升高，架空孔隙压缩明显，小孔隙几乎没有变化的特征。不同初始含水量条件下三轴压缩实验显示该区的顶部和底部黄土的强度均随初始含水量的增大而减小。由于底部黄土黏土胶结作用较高，黄土的强度减小速率大于顶部黄土。同时发现 c 值对于水的敏感性明显大于φ值，强度的降低主要是 c 值的减小导致。由于地下水位的升高，滑坡底部黄土的含水量增加，颗粒之间主要承担胶结作用的黏土矿物软化，导致附近的黄土微观结构持续破坏，导致赵家岸滑坡发生蠕动。