渗流作用下土层之间的接触面是较易发生渗透破坏的薄弱环节。在开展砂砾石渗透破坏试验研究的基础上，针对砂砾石与砂的接触面渗流及渗透破坏特性，利用大型竖向渗透仪和自主研制的环状径向水平渗透仪，研究了竖向和水平渗流作用下接触面渗流和渗透破坏的影响因素及接触冲刷的发生、发展过程。研究结果表明，典型的砂砾石与砂的接触冲刷破坏过程可分为稳定渗流阶段、过渡阶段和破坏阶段3个阶段，可用2个特征水力坡降进行划分，稳定渗流阶段与过渡阶段的分界点对应的水力坡降称为启动坡降，过渡阶段与破坏阶段的分界点对应的水力坡降称为破坏坡降；砂砾石与砂组合试样的渗透系数随砂砾石密度的增大、颗粒变细而减小，砂砾石与砂接触冲刷的抗渗坡降则随砂砾石密度的增大、颗粒变细而增大，在水平渗流情况下试样的渗透系数较竖向的大，但接触冲刷的抗渗坡降较竖向的小。

The interface between two soils is a weak place where the seepage failure occurs easily. In order to investigate the seepage and seepage resistance properties of the interface between sandy gravel and sand, based on the seepage failure tests for the sandy gravel, the impact factors of the seepages and seepage failure, the occurrence and evolution of contact scouring under the conditions of vertical and horizontal seepages are studied by using large-scale vertical permeameter and self-built annular radial horizontal permeameter. It is concluded from the test results that the typical contact scouring process can be divided into three stages, i.e., stable seepage, transitional and failure stages. The three stages can be divided by two characteristic hydraulic gradients. The hydraulic gradient corresponding to the limit of the stable seepage stage is called starting gradient and that of the transitional stage is called failure gradient. The permeability of the combined sample of sandy gravel and sand decreases with increasing of the dry density, or decreasing of the particle size of the sandy gravel. But the seepage resistance of contact scouring increases with increasing of the dry density, or decreasing of the particle size of the sandy gravel. On the condition of horizontal seepage, the permeability of the sample is larger but the seepage resistance of contact scouring is less than that of vertical seepage.