摘要
To analyze the water swelling characteristics of black cotton soil(BCS),X-ray fluorescence and X-ray diffraction characterizations were performed to investigate the chemical compositions and types of clay minerals in BCS.A montmorillonite crystal lattice was established to simulate the hydration of interlayer cations by applying the SPC/E potential energy model,universal force field,algorithm of charge balance,and periodic boundary.Results indicated that the main clay mineral found in the BCS was montmorillonite(32.6%)with small amounts of interstratified illite-montmorillonite(10.9%),illite(2.3%),and kaolinite(1.5%).The high expansive potential of BCS comes from the strong adsorption property of montmorillonite with a high content of magnesium and sodium ions to water molecules.The exchangeable cations of Na^(+)in BCS were only 3.73%,but they enhanced the adsorption capacity of clay to water molecules and accelerated the hydration of Mg^(2+)(47.1%)and Ca^(2+)(4.78%).The free swell index can be used as a classification index of the swelling potential of BCS.
为了分析黑棉土的吸水膨胀特性,采用X射线荧光光谱(XRF)和X射线衍射(XRD),测试了黑棉土的化学成分和矿物组成,应用SPC/E位能模型、UFF力场、电荷平衡(QEq)算法和周期性边界,建立了蒙脱石晶胞模型,模拟了黏土矿物的层间阳离子水化.结果表明,黑棉土中的黏土矿物主要为蒙脱石(32.6%),以及少量的伊/蒙混层矿物(10.9%)、伊利石(2.3%)和高岭石(1.5%).黑棉土的高膨胀潜势来自于土壤中高镁离子含量和高钠离子含量的蒙脱石对水分子的强大吸附性能.黑棉土中的交换性钠离子含量仅有3.73%,但其提高了黏土对水分子的吸附能力,并加速了镁离子(47.1%)和钙离子(4.78%)的水化.差分自由膨胀率可以作为黑棉土胀缩潜势的分类指标.
基金
The National Natural Science Foundation of China(No.51778139)
Jiangsu Planned Projects for Postdoctoral Research Funds(No.2020Z422).
