水土化学作用对土体黏聚力的影响——以蒙脱石-石英砂重塑土为例

发布时间：2018-08-27 15:20

【摘要】：为研究水土化学作用对土体黏聚力的影响,通过将蒙脱石-石英砂重塑土分别浸泡于超纯水(正常水体)、p H=3的HNO3(酸雨)和p H=13.5的Na OH溶液(碱性废液)中,对黏聚力变化规律和机制进行了探讨。研究发现:超纯水条件下,黏聚力先上升后下降再上升;酸性条件下,黏聚力先下降后上升再下降;碱性条件下,黏聚力先下降后上升再下降,后期出现反弹。温度对各种条件下的反应均有促进作用,但程度不一。X射线衍射(XRD)结果表明,酸会溶蚀胶结物蒙脱石,且没有新物质生成,导致黏聚力下降,浸泡中期黏聚力增大的原因尚不明确。碱性条件下有水化硅酸钙(CSH)生成,超纯水条件下还有碳酸钙(Ca CO3)生成。两种新胶结物均为离子化合物,晶胞之间以化学键相连,其键强度远大于相邻蒙脱石层组间的结合力强度。新生胶结物造成超纯水和碱性条件下黏聚力上升,化学溶蚀和离子交换是黏聚力下降的主要原因。此外,结合土质滑坡垂压和内摩擦角情况,分析了水土化学作用下的土体抗剪强度变化。超纯水条件下,抗剪强度总体变化不大;酸性条件下,抗剪强度变化与黏聚力变化一致;碱性条件下,抗剪强度表现为总体增大。
[Abstract]:In order to study the effect of soil and water chemistry on soil cohesion, montmorillonite and quartz sand remolded soil were immersed in HNO3 (acid rain) of ultrapure water (normal water) and Na OH solution (alkaline waste liquid) of pH 13.5, respectively. The change law and mechanism of cohesive force are discussed. The results showed that the cohesion first increased and then decreased and then increased under ultra-pure water condition; in acidic condition the cohesion first decreased and then increased and then decreased; in alkaline condition the cohesion first decreased and then increased and then decreased and then rebounded. The results of X-ray diffraction (XRD) show that the acid can dissolve the cemented montmorillonite, and there is no new substance, which leads to the decrease of cohesion. The reasons for the increase of cohesion in soaking period are not clear. Hydrated calcium silicate (CSH) was formed in alkaline condition, and calcium carbonate (Ca CO3) was formed in ultrapure water. The two new binders are ionic compounds, which are connected with each other by chemical bonds, and the bond strength is much higher than that between adjacent montmorillonite layers. The new cementation resulted in the increase of cohesion in ultrapure water and alkalinity. Chemical dissolution and ion exchange were the main reasons for the decrease of cohesion. In addition, the variation of soil shear strength under the action of soil and water chemistry is analyzed in combination with the vertical pressure and the angle of internal friction of the soil landslide. Under the condition of ultra-pure water, the overall change of shear strength is not obvious; in acidic condition, the change of shear strength is consistent with the change of cohesive force; in alkaline condition, the shear strength is increased as a whole.
【作者单位】：中国科学院水利部成都山地灾害与环境研究所中国科学院山地灾害与地表过程重点实验室;中国科学院大学;中国科学院青藏高原地球科学卓越创新中心;
【基金】：国家科技支撑计划课题(No.2012BAC06B02) 中国科学院重点部署项目(No.KZZD-EW-05-01)~~
【分类号】：TU43

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