Skempton (1964,1985) reports measurements of residual strength on clays of similar physical properties in the range of 13° to 15°. Results of our measurements of residual friction angles of the colluvium varied from about 24° to 12° for different types of tests and methods of sample preparation (table 3). The largest values were obtained from untreated but remolded samples tested in a direct-shear machine. The smallest values were obtained on samples that had the coarse fraction (>30 and >230 mesh) removed and were tested in a ring-shear device. After the tests, we inspected the failure surfaces developed during shearing. Samples having larger residual strength invariably contained sand-size particles along the planes of failure.