The current design practice of using gravel drains as a liquefaction countermeasure involves the selection of the drain spacing and drain diameter to keep the peak excess pore water pressure ratio low. As it has mostly been verified through small-scale 1 g shaking tests, its validity for the field-scale prototype has yet to be well investigated. In this study, a series of centrifuge tests was conducted to gain insight into the stress-dependent behavior of loose sand deposits with a level surface improved by gravel drains. Meanwhile, the current design procedure was validated with experimental data. The results revealed that the effects of gravel drains in suppressing the excess pore pressures depend significantly on the depth of the drains. The current design procedure has failed to elucidate the depth-dependent behavior of sand deposits. One of the important features of the mechanical properties of the soil used for the design of gravel drains was revealed through laboratory tests in which the coefficient of volumetric compressibility, m_v, was found to be highly dependent on the stress level, while m_v was assumed to be fixed in the design procedure. It was also found that the water flow regime in gravel drains can be a turbulent flow. The Reynolds number in drains increases from the bottom to the top, and the permeability coefficient decreases accordingly, resulting in more significant well resistance than expected based on the current design procedure. In the present study, when stress level-dependent m_v and Reynolds number-dependent k_w were used as input soil parameters, the axisymmetric diffusion equation, with consideration given to the well resistance, satisfactorily predicted the excess pore pressures in sand with gravel drains.

当前使用砾石排水管作为液化对策的设计实践涉及选择排水管间距和排水管直径以保持峰值超孔隙水压力比较低。由于它主要通过小规模的 1 g 振动测试得到验证，因此其对现场规模原型的有效性尚未得到充分研究。在这项研究中，进行了一系列离心机测试，以深入了解松散沙子沉积物的应力相关行为，该沉积物具有通过砾石排水沟改善的水平表面。同时，通过实验数据验证了当前的设计程序。结果表明，砾石排水管抑制超孔隙压力的效果显着取决于排水管的深度。当前的设计程序未能阐明砂沉积物的深度相关行为。发现m _v高度依赖于应力水平，而m _v被假定在设计程序中是固定的。还发现砾石排水沟中的水流状态可能是湍流。排水管中的雷诺数自下而上增大，渗透系数相应减小，导致井阻力比根据当前设计程序预期的更显着。在本研究中，当应力水平依赖m _v和雷诺数依赖k _w 被用作输入土壤参数，轴对称扩散方程，考虑到井阻力，令人满意地预测了砂砾排水砂中的超孔隙压力。