遇水作用下冰水堆积体角砾土微观结构与抗剪强度

Microstructure and shear strength of the breccia soil in glacial deposit body under water action

利用粉晶X射线衍射、扫描电镜(SEM)、土水化学效应试验和现场大型剪切试验等手段对角砾土在浸水前后两种状态下的矿物、化学组分和微观结构及抗剪强度等变化特征进行表征。结果显示:矿物遇水后X射线衍射强度增加,大量钙镁质胶结物溶于水继而与阳离子发生交换作用,浸水后2 d左右浓度趋于稳定;浸水后的样品中出现大孔隙,样品中片状黏土矿物颗粒呈定向排列。大剪试样结果表明,原状角砾土具有较强的结构强度,浸水后黏聚力降低31%,而内摩擦角降低19%,水对黏聚力的影响高于对内摩擦角的影响。黏土矿物遇水细微观结构定向排列是角砾土内部结构产生损伤的主要原因,钙镁胶结物溶解与阳离子置换作用是试样抗剪强度衰减的直接结果。以上研究成果为遇水作用下冰水堆积物的结构损伤进行检测提供了依据,并丰富了对理县冰水堆积体的强度衰减机制认识。

In order to study the two types of variation characteristics of mineral and chemical composition, microstructure and shear strength of the breccia soil before and after the soaking process, a series of work through X-ray diffractometer, scanning electron microscope （SEM） , water-soil chemical effect tests and large scale in-situ shear tests were carried out. The results show that the X- ray diffraction intensity increased when the mineral are mixed with water. Large amounts of calcium and magnesium cementing materials dissolve in water and cation exchange interaction occurs in the water, and the solution concentration tends to be stable after 2 days. A large number of macro pores appeare after soaking and the flake clay minerals have a directional alignment. The undisturbed breccia soft has a strong structural strength but its cohesion decrease by 31% and friction angle decreases by 19% after the water immersion. Water has a greater influence on the cohesion than friction angle. The directional alignment of the clay microstructure after soaking is the main reason for the damage in breccia soil internal structure. The dissolving and the exchanging interaction of calcium and magnesium cementing materials are the direct results of the attenuation in sample＇ s shear strength. The results provide a basis for the structure damage in glacial deposit body under water action, and they enrich the study of the mechanisms of strength attenuation in the Lixian glacial deposit body.