Pinhole Test for Identifying Dispersive Soils

A new laboratory test has been developed for direct measurement of erodibility of fine-grained soils, using a flow of water through a small hole in a specimen. The main purpose is reliable identification and improved understanding of dispersive clays, which have recently been shown to have been responsible for serious erosion damage and failure of earth dams and other structures. After considerable experimental effort a test procedure was found which gives reliably reproducible results and differentiates between dispersive and nondispersive clays. For dispersive clay the water flowing through the specimen carries a cloudy colored suspension of colloids, whereas water running through ordinary, erosion resistant clays is crystal clear.