Experimental Study of Internal Erosion of Fine Grained Soils

Internal erosion has long been a major problem associated with earth structures. Laboratory experiments provide a potential insight into the processes involved. The design of dam embankments is usually based on hydraulic criteria. Some of the hydraulic criteria are based on sediment transport theory where the critical velocities are derived from the different approaches comparing the drag force of the particles and the hydraulic load. Many hydraulic criteria for suffusion are based on tests with consistent soil samples or on analytical descriptions of the particle and pore geometry derived from characteristic parameters. An experimental study of soil suffusion is performed on a laboratory column subjected to different flow conditions and soil parameters. The permeability variation along the soil column is controlled. The initiation and the kinetics of soil suffusion are investigated using a laboratory fine grained soil (mixed sand and clay) and a natural soil. Attempts are also made to assess the influence of the clay content and the type of fine particles. The results demonstrate that low hydraulic gradients can cause suffusion. The critical shear stresses for various soil tested differ slightly when the nature of grains and fines are varied. The hydraulic gradient affects the cumulative eroded mass upon a certain threshold value.