The Shear Strength of Granular Materials with Dispersed and Non-Dispersed Oversized Particles

摘要

Soils containing dispersed and non-dispersed large particles (greater than # 4 sieve) form part of many engineered fills, glacial tills, debris flows, and residual soil deposits. Very little is known about the effect that the large particles have on the shear strength of the soil-large particles mixtures. In this study, the influence of the large particles on the shear strength of the mixtures was evaluated experimentally and numerically. The experimental analysis used direct shear tests on simulated granular materials containing large dispersed particles as well as on real sand-gravel mixtures. The numerical analysis used the Discrete Element Method (DEM). For the dispersed case (the large particles are not in contact), the laboratory and the DEM simulation results indicated that the shear strength of the mixtures increased with the concentration (C) of the large particles in the mixtures. The shear strength of the mixtures with dispersed oversize particles can be obtained from the following relationship: Sc = Sm (1 + αC). In this relationship, Sc is the shear strength of the mixture, Sm is the shear strength of the granular matrix without the oversize particles, C is the concentration by volume of the oversize particles, and α is a constant that varies between 0.4 and 2.5. For the case of the non-dispersed oversize particles (the oversize particles are in contact in the mixture), direct shear tests on sand-gravel mixtures indicated the shear strength of the mixtures can be obtained from the following relationship: Sc = Sm (1 + 0.7C +1.8 C2). In general, it was determined that the addition of oversize particles increases the shear strength of the soil in which the oversize particles are either dispersed or non-dispersed.