Effect of Bentonite Permeation on the Fabric and Strength of Ottawa Sand

Abstract

Soil fabric controls the mechanical response of the soil through the interlocking forces between its particles. This is quantified using small strain stiffness modulus Gmax, which is an important soil property that provides an understanding about the elastic behavior of the soil and its response to dynamic vibrations, such as earthquakes. Maintaining Gmax is as important as increasing the cyclic resistance in any proposed mitigation measure against soil liquefaction. Previous studies have shown the effective use of bentonite in loose Ottawa sand samples for liquefaction mitigation using dry-mixing and permeation sample preparation techniques. However, resonant column tests on bentonite-treated dry mixed Ottawa Sand samples showed a decrease of the small strain stiffness modulus (Gmax) and thus a decrease in the shear strength of the treated soil compared to that of clean Ottawa Sand samples. This work investigated the effect of permeation on the small-strain stiffness of bentonite-treated loose Ottawa sand samples. Static triaxial tests and bender element tests on these samples showed that bentonite-treated sand samples at least maintained the same shear strength and small-strain stiffness modulus as those of clean sand samples. This work proves the effectiveness of the use of the permeation method using bentonite as a non-disruptive liquefaction mitigation technique.