Effects of bentonite permeation on sand’s small strain stiffness

Abstract

The nature of bentonite which delays the generation of mean excess pore pressure, increases threshold shear strain and cyclic resistance ratios in sands; as well as its enhanced benefits with aging and longer hydration periods serve as an incentive for delving deeper into the use of this nanomaterial as a soil improvement technique. Given the numerous benefits of bentonite as a liquefaction mitigation agent, it is necessary to explore its effects on soil shear strength parameters. The consequences of bentonite permeation on sand friction angle and cohesion are negligeable; nevertheless, the small strain shear stiffness has not been targeted comprehensively. This report aims on laying a foundation for studying the impacts of permeation using bentonite suspensions on the small strain shear modulus of sands. Specimen preparation techniques; dry method and permeation; are discussed. Their results should be contrasted to check effects on the microstructure of sand. Clean sand specimens should be utilized for the base of comparison. Bender element assessment ought to be conducted to record the shear modulus at different stages of triaxial testing. Expected results are likely to reveal a similar shear modulus for permeated and clean specimen and marginally lower values for dry mixed samples. With loadings simulating earthquake scenarios, the small strain shear modulus is anticipated to decrease for all samples. The reduction is expected to be the less significant in permeated specimens, followed by dry mixed specimens and finally clean ones. The report helps present bentonite permeation as a prospective liquefaction mitigation technique while drawing the attention to probable challenges in field applications.