基于渗透性的膨胀土裂隙各向异性研究

Quantitatively research works have been carried out on fissures growth and their impacts on expansive soils strength through former project supported by National Science Foundation for Young Scholar of China. It is found that the fissures in expansive soils usually have obvious preferential orientation, which results in the anisotropic characteristics of the soil. Preliminary gas permeability tests results show that this kind of anisotropic characteristics can be represented by soils permeability characteristics, which can indicate the extent of fissures developement as well. The impacts of fissures on expansive soils can be only throughtly figured out until anisotropic characteristics are well known of the fissurs distribution. Therefore, in-situ and laboratory tests are intended to carried out with developed testing methods and equipments. Expansive soils samples will be investigated by CT method, electrical method and electrical conductance method to quantitatively obtain the anisotropic characteristics of fissures distribution in space and the evolution. Permeability tests will be carried out on both gas and water on fissured expansive soil samples. Supposed to set up a new pore distribution model to discribe the anisotropic characteristics of the fissurs. Meanwhile, numerical simulation will be adorpted to analysis the anisotropic characteristics of soil permeability. Then the influence mechanism will be revealed of fissures distribution on soil permeability and the the law will be found of soil permeability varing with fissures distribution. The most distiguisched feature and innovation of this proposal is that all the research works are put forward quantitatively, combined with numerical simulation and theoretial analysis on the anisotropic characteristics of fissures and on their impaction. Upcoming research works and results will definitely be helpful to understand expansive soils better, to improve the theory and investigation methods for special soils, and to find reasonable engineering measures for expansive soil problems solution.

青年基金项目对裂隙发展及其对土体强度影响规律进行了定量化研究，结果显示，膨胀土中裂隙分布具有明显的方向性，土体工程力学性质也因此呈现出各向异性特征。初步渗气试验结果表明，渗透性不仅能反映裂隙发育程度，也可表征裂隙的各向异性特征。要真正搞清裂隙对膨胀土性质的影响规律，深入研究裂隙分布的各向异性是前提和基础。本项目拟改进和完善现有测试手段和方法，采用CT法和电（导）法，在现场和室内进行膨胀土裂隙观测试验，研究裂隙的空间分布各向异性特征及演化规律；进行渗气和渗水试验，建立反映膨胀土裂隙各向异性的孔隙分布模型，结合数值模拟手段，分析裂隙形态及分布对土体渗透性各向异性特征的影响机理和规律。试验结合理论研究，定量地揭示膨胀土裂隙各向异性特征及其影响的相关规律，是本项目的特色和创新之处。本项目的研究将有助于加深对膨胀土特性的认识，进一步丰富特殊土研究理论和方法，也有助于膨胀土工程合理处置措施的选择。

本项目主要就膨胀土的渗透性及其裂隙分布的各向异性进行了研究。开展了膨胀土裂隙的定量观测研究,改进了图像处理程序和算法，开展了较长历时的现场裂隙观测试验，提出了一种新的、基于电导法的裂隙分布及开展深度的观测方法。进行了裂隙膨胀土渗透性试验研究，揭示了试样尺寸、裂隙发展不同程度、渗透方向等对裂隙膨胀土渗透性的影响规律，初步建立了裂隙与膨胀土渗透性间的关系模型。进行了土体孔隙模型试验和数值模拟研究。完善了均匀分布的孔隙模型，研究了用PFC软件模拟孔隙结构和定量统计孔隙特征指标的方法，并开发了相应的程序。研究了膨胀土裂隙各向异性对边坡渗流场的影响，揭示了裂隙诱导各向异性方向、各向异性程度以及各向异性分布对边坡流场的影响规律。结合实际工程，进行了膨胀土边坡防护方法试验和排水措施数值模拟，建议了实际工程中合适的防护方法和排水措施。