Permeability and Piping in Fractured Rocks

Design criteria for compacted fine grained soil placed against coarser material ensure protection of the soil from being eroded. However, not much attention has been paid to the problem of erosion and piping when compacted soil is placed against jointed rock. This paper reports the results of preliminary laboratory investigations to study the erosion of a compacted silty soil into rough or smooth fractures of a cylindrical rock specimen under radial flow conditions. The tests show that erosion of soil particles and subsequent transport through the fractures are functions of fracture-aperture, pressure-difference causing flow, and size of soil particles. The largest dimension of the soil particles eroded generally increased with the pressure difference causing flow. Cycling of water pressure seems to have a pronounced effect on the erodibility and transport of soil particles.