Triaxial Shear Characteristics of Clayey Gravel Soils

During recent years, the Bureau of Reclam ation’s Earth Laboratory has been studying all of the physical properties of gravelly soils because these soils are used extensively in Bureau earth dams,
canal embankments, and earth canal linings, and because prior soils research has been largely limited to testing the finer soil fraction. This paper was prepared to present the results of recent research tests for studying the shear characteristics of impervious gravel soils which contained varying amounts of a clayey soil matrix.
Large-scale triaxial testing equipment was used for this study on the clayey gravel soils. The testing program was formulated to evaluate the effect of gravel content on shear strength for materials containing particles up to 3 inches in size. The shear test results are presented on the basis of effective stresses and pertinent information on positive and negative pore pressures measured during the tests is given. Also included in the paper is a very brief review of the previously reported shear tests made on pervious sandy gravels, for the purpose of comparing the shear properties of the pervious materials with those of the impervious clayey gravels. The conclusions reported in this paper are based on the analysis of 20 individual shear specimens of the clayey gravel soils.