Experimental Study on the G_max Characteristics of the Sand-Silt Mixed Soil Materials Using Bender Element Testing

To study the small strain shear modulus (G_max) of saturated sand-silt mixed soil materials, a series of tests were conducted using the bender element apparatus, and the influences of fines content (FC), relative density (D_r), and effective confining pressure (σ'3c) were taken into consideration. The test results indicate that the G_max of the mixed soil materials decreases first and then increases with the FC up to 100% with D_r = 35% and 50%, while the G_max decreases with the increasing FC when D_r = 60%. Moreover, for a given D_r, the G_max increases with the increasing σ'3c, and the increase rate keeps constant under various FCs. The G_max of specimens under various FCs decreases with the increase of the void ratio (e). The decrease rate between the G_max and e differs when the σ'3c is given, which is influenced by the FC. The G_max of the mixed soil materials can be evaluated by the Hardin model when the FC is determined. The best-fitting parameter A of the Hardin model first decreases and then increases as FC increases. The revised Hardin model, considering the influence of FC, σ'3c, and e, can be used to evaluate the G_max for different types of sand-silt mixed soil materials. The error between the evaluated and tested G_max is less than 10%.