Evaluation of the Shear Strength and Dilatancy Behavior of Sand-Clay Mixtures Under Direct Shear Tests

Dilatancy behavior is a critical factor in the study of granular materials’ shear strength and deformation characteristics, as it affects several other geotechnical issues as it plays a vital role in various geotechnical problems such as the stability of slopes, earth dams, and retaining walls, etc. This paper focuses on sand-clay mixtures’ shear and dilatancy behavior with varying levels of moisture content (10%, 15%, 20%) and normal stresses (100 kPa, 200 kPa, 300 kPa). The goal is to investigate the factors that influence the dilatancy behavior of soil to improve the accuracy of geotechnical models and optimize design parameters for structures such as retaining walls, dams, embankments, etc. A series of unconsolidated undrained direct shear experiments in a shear-box apparatus were conducted to observe the evolution of the shear and dilatancy behavior of the sand-clay mixtures. The results show that as the ratio of bentonite clay is 10%, the shear resistance of the soil is not affected by moisture content (10%, 15%, 20%) and normal stresses (100 kPa, 200 kPa, 300 kPa), whereas the dilatancy angle of soil increases with increasing moisture content and decreases with increasing normal stress.