The elastic moduli of clays with dispersed oversized particles

To calculate the elastic deformations experienced by soils subjected to static or dynamic loads, knowledge of their elastic moduli is required. The elastic moduli are normally evaluated in the laboratory using conventional triaxial compressive tests on cylindrical samples. For meaningful test results, it is necessary to maintain a ratio of sample diameter to maximum particle size of approximately 6 to 1 or greater. However some soils have dispersed oversized particles that make it impossible to test them in the conventional triaxial apparatus. This study presents the application of a theoretical method developed by Hashin that calculates the elastic moduli of a composite made of an elastic matrix containing large dispersed particles. The Hashin method requires only knowledge of the elastic moduli of the matrix (which can be obtained from conventional triaxial compression tests) coupled with the concentration by volume of the large particles in order to calculate the elastic moduli of the mixture. The Hashin method was applied to dry and unsatutrated clay-sand mixtures, and it was found to predict well their measured elastic moduli. The accuracy of the prediction of the elastic moduli by the Hashin method was determined from a statistical analysis of the laboratory and the theoretical results. The measurement of the elastic moduli of the soil mixtures was carried out using an ultrasonic velocity apparatus.