STUDY ON THE PERMEABILITY AND STABILITY OF LANDSLIDE DAM MATERIALS

Landslide dams are natural dams formed by collapse, landslide, debris flow, etc. Landslide dams are different from man-made dams for its lack of sufficient consolidation, leading to loose dam structure and highly non-homogeneous materials. Large water head caused by rising of water level could trigger seepage deformation of soil and influence landslide dam stability, which may lead to dam breach and catastrophic damage. Due to the presence of large diameter particles in landslide dams, the conventional penetration test device is difficult to meet the requirements. A large diameter infiltration device with the diameter of 60cm was developed. The paper reports the experimental study on the seepage characteristics of landslide dam material. It was observed that piping and soil flow are the two seepage failure modes of landslide dams. The landslide dams with coarse grain in majority are prone to piping failure, and the dams with fine grain in majority and gap-graded materials are prone to soil flow failure. The experiments showed the permeability coefficient reduces with the increase of the dry density and is influenced by the amount of fine particles. Using the nonuniformity coefficient or the curvature coefficient independently is not suitable for evaluating the permeability coefficient change. A discriminant formula for the seepage failure and a critical hydraulic gradient equation for piping are provided based on the experimental data.