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EVOLUTION CHARACTERISTICS AND MECHANISM OF SILT CLAY PROPERTIES UNDER DRY-WET CYCLE OF POLLUTION FROM LIVING SOURCES
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摘要: 以生活源污染质降解终端产物Na2CO3和Na3PO4的混合溶液为污染质溶液对中国徐州地区粉质黏土进行渗流，完成了10次干湿循环试验，分析了在生活源污染质干湿循环下粉质黏土性质的演化特征，并揭示了其演化机理。研究结果表明：粉质黏土在经过生活源污染质10次干湿循环的过程中，土体渗透性增强1~2个数量级，电阻率降低20~25Ω ·m，密度先减小到2g ·cm-3以下后有所回升，抗剪强度降低30kPa左右，且渗流路径长的土体性质变化具有一定的滞后性；在干湿循环过程中土体表面干缩裂缝逐渐发育扩展；干湿循环土样渗流路径越短，元素的密度变化量越大；生活源污染质干湿循环下土体性质发生变化的主要原因是渗流冲刷作用、化学反应、Na+离子吸附作用、湿胀干缩作用和重力下渗作用共同作用的结果。Abstract: This paper uses the mixed solution of Na2CO3 and Na3PO4 to percolate the silty clay in Xuzhou of China. It completes 10 times dry-wet cycles. The solution is a terminal product of degradation of municipal waste. The evolution characteristics of the properties of silty clay under the dry-wet cycles are analyzed, and the evolution mechanism is revealed. The results show that the permeability of silty clay increases, the resistivity decreases, the density first decreases and then rises, the cohesion and the angle of internal friction decrease, and the change of soil properties with a long seepage path has a certain lag, the dry shrinkage cracks on the surface of the soil develop and expand gradually, and the seepage path of the soil develops gradually during the dry and wet cycles. The shorter the seepage path of the soil samples, the greater the density variation of elements. The main reasons for the change of soil properties under the dry-wet cycles are the combination of seepage erosion, chemical reaction, Na+ion adsorption, wet expansion, dry shrinkage, and gravity infiltration.
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Key words:
- Dry-wet cycle /
- Seepage /
- Pollution from living sources /
- Property evolution /
- Mechanism
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图 3 土体渗透系数随干湿循环次数的变化曲线
Figure 3. Change curve of soil permeability coefficient with the times of dry-wet cycle
图 4 土体密度和电阻率随干湿循环次数的变化曲线
a. 密度；b. 电阻率
Figure 4. Change of soil density and resistivity with the number of cycles under the condition of dry-wet cycle
图 5 土体抗剪强度随干湿循环次数的变化曲线
a. 抗剪强度; b. 黏聚力; c. 内摩擦角
Figure 5. Shear strength curve of soil under the condition of dry-wet cycle
图 6 土体干缩裂缝随干湿循环次数的变化
Figure 6. The relationship between the dry shrinkage cracks of soil and the number of dry-wet cycles
图 7 土体开裂表观裂隙率与干湿循环次数的关系曲线
Figure 7. Relationship between apparent crack rate of soil cracking and dry-wet cycles
图 8 代表性元素的密度变化量随干湿循环次数的变化曲线
a. Si; b. Al; c. Ca; d. P; e. Na; f. C
Figure 8. Variation curve of density of representative elements with the number of dry wet cycles
图 9 生活源污染质降解终端产物对土体进行干湿循环作用机理
a. 相互关系; b. 自然蒸发过程; c. 渗流过程
Figure 9. Mechanism of dry-wet cycle of end products of degradation of pollutants from domestic sources on soil
表 1 未污染土体基本性质指标
Table 1. Basic properties of unpolluted soil
天然含水率/% 液限/% 塑限/% 塑性指数/% 土体定名 23.00 29.4 16.5 12.9 粉质黏土 天然密度/g·cm-3 比重 最优含水率/% 最大干密度/g·cm-3 1.642 2.811 20.7 1.80 
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表 2 黏土矿物相对含量
Table 2. Relative content of clay minerals
高岭石/% 伊利石/% 蒙脱石/% 伊蒙混层/% 绿泥石/% 17.00 36.00 14.00 27.00 6.00
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