Predicting the small strain shear modulus of coarse-grained soils

Abstract Coarse-grained soils are important geotechnical materials widely used in construction. The contribution of particle size distribution on the small strain shear modulus Gmax of coarse-grained soils has not yet been fully recognized. This paper presents an experimental investigation into the effects of the uniformity coefficient Cu and the mean particle size D50 on the small strain shear modulus of coarse-grained soils. To this end, a series of shear wave velocity tests were conducted at different confining stresses and void ratios on reconstituted specimens covering a wide range of particle size distributions. All tests were performed by taking advantage of a custom-developed measurement device in a large-scale triaxial apparatus. The results demonstrate that Cu and D50 have pronounced but opposite effects on Gmax. Specifically, Gmax decreases with Cu and increases with D50. The effects of Cu and D50 were then quantified to generate two types of empirical equations, type-A and type-B, that are representative of a broad family of Gmax equations accounting for the influence of particle size distribution. The equations are tuned based on model parameters A, x and n. In both equations, n is a function of Cu. The difference between the two types of equations is that x is the function of Cu and D50 and A is the function of Cu in the type-A equation, while x is constant and A is the function of Cu and D50 in the type-B equation. The proposed equations for predicting Gmax were used to produce acceptable estimates for both coarse-grained soils in this study and from existing literature. The findings acquired from this study are expected to provide a reference for estimating the small strain shear modulus of coarse-grained soils at the beginning of the project when the test data have not yet been obtained.