Stabilized dispersive soil with calcium bicarbonate formed by pseudo-karstification
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摘要: 分散性土具有遇水分散流失的工程特性,常采用石灰、水泥等对其进行改性处理,但这些改性材料对环境容易造成一定的破坏。通过针孔试验、碎块试验、双比重计试验以及扫描电镜试验、能谱分析试验等,研究了基于岩溶作用形成的碳酸氢钙溶液改性分散性土的影响因素及其作用机理。试验结果表明,采用抽滤或抽气的土水分离方式能够保证碳酸氢钙分解程度高,改性速率快,改性效果好。当仿岩溶碳酸氢钙溶液与分散性土的质量比为4∶1时,分散性土被改性为非分散性土。仿岩溶碳酸氢钙溶液加入到分散性土中后,增加了土体中钙离子的含量,降低了土体的碱性,新生成的碳酸钙具有填充和胶结作用,提高了土的抗水蚀性,降低了土体的分散性。研究表明,仿岩溶碳酸氢钙不仅具有环境友好的特点,而且能有效改性分散性土。Abstract: The dispersive soil has the engineering characteristics of dispersivity and loss in water. It is often stabilized by lime, cement, etc. But these stabilized materials are easy to cause certain damage to the environment. Through the pinhole tests, the crumb tests, the double-hydrometer tests, the scanning electron microscope tests and the energy spectrum analysis tests, the influence factors and the mechanism of the stabilized dispersive soil with calcium bicarbonate formed by pseudo-karstification are studied. The test results show that the separation of soil and liquid by suction filtration or suction can ensure the high decomposition degree of calcium bicarbonate, the fast modification rate and the good modification effect. When the mass ratio of karst calcium bicarbonate solution to dispersible soil is 4:1, the dispersive soil is modified into the non-dispersive soil. After the calcium bicarbonate solution by pseudo-karstification is added to the dispersive soil, the content of calcium ions in the soil increases, and the alkalinity of the soil decreases. The newly-generated calcium carbonate has a filling and cementing effect to improve the water resistance of the soil and to reduce its dispersivity. It has shown that the calcium bicarbonate solution by pseudo-karstification has the characteristics of environmental friendliness and can effectively stabilize the dispersive soil.
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Keywords:
- dispersive soil /
- karstification /
- calcium bicarbonate /
- calcium carbonate /
- stabilized mechanism
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图 1 仿岩溶碳酸氢钙溶液制备装置示意图
Figure 1. Diagram of devices for calcium bicarbonate formed by pseudo-karstification
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图 2 澄清液电导率与液固比的关系
Figure 2. Relationship between clarified liquid conductivity and liquid-solid ratio
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图 3 不同液固比抽滤风干处理后土样的针孔和碎块试验
Figure 3. Pinhole and crumb tests on soil samples after suction filtration and air-dried with different liquid-solid ratios
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图 4 不同处理后（液固比4∶1）土样干燥表面情况
Figure 4. Dry surface conditions of soil samples after different treatments (liquid-solid ratio 4∶1)
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图 7 不同液固比非常规颗粒级配试验开始后2 h量筒情况
Figure 7. Results of unconventional particle tests with different liquid-solid ratios after 2 h in graduated cylinder
表 1 土样的物理性质
Table 1 Physical properties of soil sample
土样名称 颗粒相对质量密度 液限 wL /%塑限 wP /%塑性指数 IP 最大干密度 ρdmax /(g·cm-3)最优含水率wop/% 分散性土 2.70 38.3 21.5 16.8 1.69 19.7 
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表 2 土样的化学性质
Table 2 Chemical properties of soil sample
土样名称 易溶盐含量/(g·kg-1) 难溶盐含量/(g·kg-1) 有机质含量/(g·kg-1) 酸碱度 分散性土 2.3 119.6 8.4 9.78
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表 3 土水分离方式的操作说明
Table 3 Instructions of soil-water separation mode
处理方式 操作说明 自然风干（静置） 将土体与碳酸氢钙溶液按不同液固比混合后,置于通风处,土水悬液中水分自由蒸发 抽滤风干 将土体与碳酸氢钙溶液按不同液固比混合后,采用真空泵进行抽滤,促使土水分离；然后将湿土土样置于通风处风干 抽气抽滤风干 将土体与碳酸氢钙溶液按不同液固比混合后,放入真空泵的饱和缸中抽气2 h,然后再抽滤风干
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表 4 仿岩溶碳酸氢钙改性分散性土的试验结果
Table 4 Results of stabilized dispersive soil with calcium bicarbonate formed by pseudo-karstification
土样处理方式 液固比 针孔试验 碎块试验 双比重计试验 综合判定 自然风干（静置） 0.5∶1 分 过 — 分 1∶1 分 过 — 分 2∶1 分 非 — 分 3∶1 分 非 — 分 4∶1 分 非 — 分 5∶1 分 非 — 分 6∶1 分 非 — 分 抽滤风干 0.5∶1 分 分 分 分 1∶1 分 分 过 分 2∶1 分 分 过 分 3∶1 过 过 过 过 4∶1 非 非 过 非 5∶1 非 非 非 非 6∶1 非 非 非 非 抽气抽滤风干 0.5∶1 分 分 — 分 1∶1 分 分 — 分 2∶1 分 分 — 分 3∶1 过 过 — 过 4∶1 非 非 — 非 5∶1 非 非 — 非 6∶1 非 非 — 非 纯水对照组（抽滤风干） 0.5∶1 分 分 分 分 1∶1 分 分 分 分 2∶1 分 分 分 分 3∶1 分 分 分 分 4∶1 分 分 分 分 5∶1 分 分 分 分 6∶1 分 分 分 分 注： 分表示分散性土,过表示过渡性土,非表示非分散性土。
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表 5 能谱分析钙元素试验结果
Table 5 Results of mineral analysis tests on calcium content
谱图（a） 谱图（b） 序号 Ca含量/% 序号 Ca含量/% 谱图1 7.17 谱图1 0.29 谱图2 6.22 谱图2 0.53 谱图3 5.78 谱图3 0.39 谱图4 3.31 谱图4 0.30 谱图5 5.95 谱图5 0.35 谱图6 4.08 谱图6 0.48 谱图7 4.30 — — 谱图8 2.79 — — 最大 7.17 最大 0.53 最小 2.79 最小 0.29 平均值 4.95 平均值 0.39
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