裂隙粘土的裂隙动态演化规律及饱和/非饱和渗透特性研究

Cracks prevail in natural soil grounds in the background of global warming and frequent drought flood disaster. The existence of crack will cause most important effect about soil’s properties and make the soil’s mechanical property to be discontinuous and reduce the soil’s strength. It will also provide preferential pathways for fluid flow, which relates to water infiltration into soil and contaminate solute transport underground. The program based on the research foundation of the candidate’s doctoral thesis and taken fissured clay of Huangshan Slope in Zhenjiang city as research object. First, the soil crack evolution test will be conducted and the crack development path in the process of desiccation and hygroscopic will be acquired. The dynamic evolution law of soil crack under the effect of climate will be revealed. Then, the distribution characteristics and statistical law of cracks will be acquired and the 3D crack network will be build. At last, the calculated method to determine saturated/unsaturated permeability tensor of fissured clay will be presented based on the 3D crack network. The method to predict the soil-water characteristic curve and permeability function for a fissured clay considering development process of cracks will also be presented. The research will establish the foundations for the analysis of saturated and unsaturated seepage of fissured clay, and it is of great importance to engineering construction on the fissured soil area.

在全球日益变暖和旱涝灾害日渐频繁发生的背景下, 土体开裂现象日趋普遍。裂隙的存在对土体的强度、变形等性质产生重要的影响，导致裂土的工程性质很差。土体中的裂隙还为液体的流动提供了高渗透通道，影响了液体在土壤中的运移规律。本课题拟承接博士论文基础，以镇江黄山边坡裂隙粘土为主要研究对象，首先开展土体裂隙演化试验，得到裂隙粘土收缩开裂、吸湿膨胀过程中的裂隙发展路径，揭示气候作用下土体裂隙的动态演化规律；然后通过调查得到土体裂隙几何参数，确定裂隙的分布特征，构建土体的三维裂隙网络模型；最后对裂隙粘土的饱和/非饱和渗透特性进行研究，建立确定裂隙粘土饱和/非饱和渗透张量的方法，并依据裂隙发展路径，提出考虑裂隙动态变化的非饱和裂隙粘土土水特征曲线和渗透函数确定方法。研究将为裂隙粘土饱和/非饱和渗流分析奠定基础，对裂土地区工程建设具有重要意义。

针对开裂导致土体重要性质改变的问题，研究了裂隙粘土的裂隙演化规律及渗透特性。通过气候环境作用下土体开裂正交试验，定量分析了环境因素对土体开裂的影响，揭示了开裂过程中裂隙特征参数的变化规律，明确了温度是影响粘土开裂的主控因素。开展了蒸发作用下裂隙粘土湿热特性试验和数值模拟研究，揭示了蒸发过程中土体含水率、基质吸力和温度的时空分布规律。基于裂隙几何参数的概率密度分布模型，采用Voronoi图法生成了土体水平方向二维随机裂隙网络，分析了裂隙深度和宽度的线性函数关系，确定了裂隙垂直方向形态，构建了与实际形态较为接近的土体三维随机裂隙网络模型。通过模拟水在裂隙网络水平方向和垂直方向的流动，建立了裂隙粘土饱和渗透张量和非饱和土水特征曲线与渗透函数的确定方法，揭示了裂隙粘土各向异性渗透特性。依据土体裂隙在蒸发作用下的发展路径，提出了考虑裂隙动态变化的裂隙粘土土水特征曲线和渗透函数确定方法。研究成果对裂隙粘土边坡渗流与稳定分析、农业灌溉效能提高及垃圾填埋场防渗垫层开裂后的污染物控制等问题具有重要的参考价值和指导意义。