基于颗粒间作用力的分散性土渗透破坏机制研究

Dispersive soil is the kind of soil which can be spontaneously dispersed into soil particles in still low salt water because the exclusion force exceeds the attraction force of ion one another. It can cause the seepage failure of impervious bodies. More scientists have been researched a lot of studies on the dispersive mechanism and seepage failure, but little researched on the response mechanism between the inter-particle forces (micro-view) and the seepage failure (macro-view) of dispersive soil. So this study has important significance to further analyze of seepage failure and control methods of impervious bodies of dispersive soil from the micro view..Applicant found that the dispersive mechanism of cohesive soil had come from two aspects. One was the physical and chemical properties of soil, such as lower cement content, higher sodium content and stronger pH alkaline. The other was the chemical compositions and concentration of water. The attraction and exclusion among the soil particles were changed by the water, which could influence the cohesion and the dispersion of particles. Based on the previous studies, this project will utilize the test methods of atomic force microscope, zeta potential, tensile strength and seepage failure, combined with theories of the soil mechanics, soil chemistry, soil physics and colloid chemistry, in order to continue to further research on the response mechanism and control methods of seepage failure of dispersive soil based on the inter-particle forces. Two main scientific issues of this project are to resolved that the first is the model of inter-particle force of dispersive soil, and the second is the mechanism of seepage failure of dispersive soil based on the inter-particle forces.

分散性土在低含盐量水中由于离子间排斥力超过吸引力，引起土颗粒产生分散，进而导致防渗体的渗透破坏。前人已对其分散机制、渗透破坏等方面做了诸多研究，但对分散性土颗粒间作用力（微观）与渗透破坏（宏观）之间的响应关系研究甚少，而此研究对从微观角度进一步分析分散性土防渗体的渗透破坏与控制方法具有重要的意义。.申请者研究发现，粘性土产生分散的机制来源于两个方面，一是土中胶结物、钠离子和酸碱度等物理化学性质，二是水的化学组分和浓度。在水作用下土颗粒之间的斥力与引力发生改变，进而影响颗粒之间的分散与凝聚。本项目在已有研究的基础上，采用原子力显微镜、ζ-电位、抗拉强度、渗透破坏等试验方法，结合土力学、土壤化学、土壤物理学和胶体化学等理论，深入探讨基于颗粒间作用力的分散性土渗透破坏机制与控制方法。本项目拟解决的两个关键科学问题是：（1）分散性土颗粒间作用力的模型；（2）基于颗粒间作用力的分散性土渗透破坏机制。

分散性土在低含盐量水中由于离子间排斥力超过吸引力，引起土颗粒产生分散，进而导致防渗体的渗透破坏。本项目采用理论分析、数值与物理模拟、试验分析等方法，构建了分散性土颗粒间的作用力模型，提出了当量浓度与当量水头表征土颗粒间作用力的方法，研究了水-土环境变化对分散性土分散性能的影响，采用电阻率评价了分散性土的电学特性与分散特性、力学特性之间关系，分析了粉煤灰改性分散性土的影响因素及其作用机理，研究了铝酸复合改性剂（ACC）原位注浆改性分散性土的可行性，探索了仿岩溶碳酸氢钙（CFPK）制备与改性分散性土的方法，为科学指导分散性土的安全应用提供重要的理论依据与科技支撑。重要研究结果如下：. （1）根据粘性土的分散机理，选取液限（WL）、粘粒含量（PC）、钠百分比（PS）和pH值作为颗粒间的作用力指标，构建了土颗粒间作用力模型，即F=2WL+PC -（10pH+PS）；根据改进碎块试验、针孔试验，分别提出了采用当量浓度与当量水头表征土颗粒间作用力的方法，即F=C当量、F=H当量；采用原子力显微镜，探究了颗粒间作用力的测量方法。. （2）水环境中酸碱含量的增加可抑制土的分散性。分散性土的压缩模量、黏聚力、内摩擦角随着碱含量增大呈现先增后减，随酸含量的增大而减小。土体阳离子以钠为主的钠基土水稳性弱于以钙离子为主的钙基土。随着土中电解质溶液浓度的增加，土的水稳性逐步增强。. （3）分散性土的电阻率随温度的升高呈反比例函数；在同一温度下，非分散性土的电阻率明显高于分散性土，在低温条件下（T<10℃）表现尤为明显。随生石灰掺入量的增加，电阻率增大，抗压强度增大；随养护龄期的增加，电阻率减少，抗压强度增大；建立了采用电阻率评价改性土抗压强度的模型。. （4）粉煤灰、ACC、CFPK可有效改性分散性土。粉煤灰的改性效果受到剂量、龄期和压实度的影响。ACC原位注液改性效果与剂量、压实度、渗透系数与灌注方式有关。初步探索试验结果表明，CFPK形成的碳酸钙具有胶结与填充作用，增强抗水蚀能力，改善土体的分散性能。