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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。
In order to study the influence of chemical and chemical reaction on the cohesion of soil, the monolayer-quartz sand remodeling soil was soaked in ultrapure water (normal water), HNO3 (acid rain) with p H = 3 and p H = 13.5 Of NaOH solution (alkaline waste), the cohesion of the law and mechanism were discussed. The results showed that under the condition of ultrapure water, the cohesive force firstly increased, then decreased then increased again. Under acidic condition, cohesion decreased first and then increased then decreased again. Under alkaline condition, the cohesion decreased first and then decreased and then decreased Bounce Temperature has a stimulating effect on various conditions, but to varying degrees. The results of X-ray diffraction (XRD) show that the acid will dissolve the cemented montmorillonite and no new material is formed, which leads to the decrease of cohesion and the increase of cohesion in the middle of soaking. Calcium silicate hydrate (CSH) is formed under alkaline conditions and calcium carbonate (CaCO 3) is formed under ultrapure water conditions. The two new cements are ionic compounds, and the unit cells are chemically bonded. The bond strength is much greater than that between adjacent montmorillonite layers. New born cement caused by ultrapure water and alkaline cohesion increased chemical dissolution and ion exchange is the main reason for the decline in cohesion. In addition, the change of soil shear strength under the action of soil-water chemistry is analyzed based on the conditions of vertical pressure and internal friction angle. Under the condition of ultrapure water, the shear strength does not change much in general. Under acidic conditions, the change of shear strength is consistent with the change of cohesion. Under alkaline conditions, the shear strength increases generally.