非等向应力条件下水泥砾质土心墙料渗透机理研究

Permeability characteristics of cement-gravel soil as core material for high earth-rockfill dam is one of the key factors of restraining its application in practical engineering. However, permeability of cement-gravel soil is studied under isotropic stress condition which is not consistent with the actual stress. Based on the reason, permeability rule is studied under anisotropic stress condition by means of theoretical analysis and laboratory experiment . The optimal composition level among gravel, clay and cement of cement-gravel soil is found out through orthogonal experiment. By use of large triaxial permeability experiment, permeability rule of the cement-gravel soil is researched under anisotropic stress condition. Seepage pressure effect on deformation is investigated by bilinear method. Then the permeability model of the cement-gravel soil is established based on anisotropic stress state. Finally, the model is verified and improved by permeability experiment data of cement-gravel soil under different compositions and stress levels. The permeability mechanism of cement-gravel soil is analyzed thoroughly to make the model have reliability and applicability under anisotropic stress condition. The anticipated results can provide scientific support for permeability characteristics research of cement-gravel soil using as the core material of high earth-rockfill dam.

作为高土石坝心墙材料，水泥砾质土的渗透特性是制约其应用于实际工程的关键因素之一。对水泥砾质土渗透特性的研究通常是在等向应力状态下进行的，与实际应力状态存在较大差异。鉴于此，项目通过理论分析和室内试验等手段，研究非等向应力条件下水泥砾质土心墙料的渗透规律。采用正交试验方法优选水泥砾质土中各掺料间的最优组合水平；利用大型三轴渗透试验对水泥砾质土在非等向应力条件下的渗透规律进行研究；基于“双线法”分析渗透压力对变形的影响；建立非等向应力状态下水泥砾质土的渗透模型；并用不同掺量组合和应力水平条件下水泥砾质土的渗透试验数据对该模型进行验证和完善，使其具有较好的可靠性和适用性，揭示非等向应力状态下水泥砾质土渗透机理。预期成果可为水泥砾质土应用于高土石坝心墙材料渗透特性研究提供科学支撑。

作为高土石坝心墙材料，水泥砾质土的渗透特性是制约其应用于实际工程的关键因素之一。通常对水泥砾质土渗透特性的研究是在等向应力状态下进行的，与实际应力状态存在较大差异。鉴于此，项目通过理论分析和室内试验等手段，研究了水泥砾质土在不同水泥掺入比下压实特性及水泥砾质土中各掺料间的组合水平；获得随着水泥掺入比的增加，水泥砾质土的最大干密度呈递减趋势，最优含水率呈递增趋势。利用研制的三向渗透试验装置，对水泥砾质土在非等向应力条件下渗透特性开展研究，发现剪切变形对水泥砾质土渗透性具有显著影响。剪切变形起始阶段水泥砾质土渗透系数是剪切结束阶段的5~10倍，且围压对剪切结束阶段水泥砾质土渗透性能影较小。非等向应力条件下水泥砾质土在x、y、z三个方向的渗透系数总体变化趋势相似，x方向和y方向渗透系数接近，但竖直方向渗透系数低于水平方向。提出修正椭圆-抛物双屈服面模型三维化改进后能够较好地反映水泥砾质土力学特性，为其在非等向应力条件下渗透性能研究提供基础。构建了围压、水泥掺入比、应力水平和孔隙比与水泥砾质土渗透系数的内在关系式，建立非等向应力条件下水泥砾质土渗透数学模型，揭示了非等向应力条件下水泥砾质土渗透机理。研究成果对揭示水泥砾质土渗透机理、完善土体渗流理论具有重要的学术价值，并将有助于推动水泥砾质土应用于高土石坝建设。