内部侵蚀作用对土体力学特性的影响机理研究

Internal erosion of soil resulted from piping, seepage or overtopping is found to be responsible for a larger number of hydraulic structure failures. Due to the difficulty in simulating piping effect in laboratory, there is little element experimental research on mechanical properties of the disturbed soil. Knowledge on the mechanism of piping erosion is still limited. In this research, a new method of preparing samples subjected to piping effect is achieved by dissolving water soluble material (glucose) in sandy soil. In this way, initiation and propagation of piping erosion can be clearly observed by means of 1D seepage model test. Also, qualitatively evaluation of the quasi-elastic properties of the disturbed soil at very small strain level could be achieved through a series of torsional shear test, which would help to establish the mechanical model of piping erosion. In addition, the “inherent anisotropy” caused by the continuous defect inside the sand is investigated for the first time by shearing the piping-influenced sand under different angle of the major principal stress. The output from this research will provide the theoretical basis for a better understanding of the mechanism of internal erosion.

由管涌等水土内部侵蚀作用产生的贯通侵蚀孔道是导致土体结构破坏以及边坡、水坝、堤防等失稳的重要原因之一。由于当前缺乏在单元试验中实现土体内部贯通侵蚀孔道的方法，针对侵蚀作用下扰动土体的力学特性研究仍非常有限，对管涌侵蚀发展机理的认识仍不够清晰。本项目拟通过渗流模型试验，利用溶解土样中预制的水溶性化学添加物的方法重现管涌发生、发展的侵蚀过程,揭示侵蚀作用的内部发育机理和演化规律；基于高精度的测量方法，进行侵蚀扰动后土体复杂应力路径下的空心圆柱扭剪试验，研究内部侵蚀作用对土样杨氏模量、泊松比与剪切模量等关键力学指标的影响；同时通过主应力旋转，探讨由管涌面引发的各向异性对土体力学行为的影响，以此建立侵蚀-变形-强度耦合作用下的管涌力学模型。研究成果将有助于阐明管涌的物理机制，认识内部侵蚀作用下土体力学特性的演化规律及对土体稳定性的影响，同时扩展对内含管涌面的扰动土体原生各向异性的认知。

土体的内部侵蚀作用，包括地下水渗流引起的管涌、流土等，是导致土体结构破坏并引发地面塌陷、边坡及大坝失稳的重要原因之一。本项目通过溶解预置于土样内部的水溶性化学添加物的方法，真实、有效地还原土体的管涌侵蚀作用，实现细观角度下的土体内部侵蚀作用演化机理研究。首先，在渗流模型试验中，重现了管涌发生、发展的全过程，结合小型锥尖贯入试验，获得了侵蚀影响范围及侵蚀后土体贯入阻力的衰减规律。其次，在三轴试验和空心圆柱试验中，基于高精度的测量手段，获得了侵蚀扰动作用对试样的杨氏模量、泊松比与剪切强度等关键力学指标的影响规律。结合不同主应力方向下的剪切试验，针对内含水平向、竖向侵蚀体的试样，分别探讨了侵蚀薄弱面引发的各向异性对土体小应变剪切模量和剪切强度的影响。最后，基于离散元数值模型，对管涌侵蚀过程进行模拟分析，研究了颗粒流失后土体力学强度的损失效应，进一步阐明了内部侵蚀作用下土体力学特性弱化的内在机制。