Effect of Low-Plastic Fines Content on the Properties of Clean Sand

Abstract

Physical properties of clean sand and pure clay are well established with different theories in the geotechnical literature; however, the properties of sand with fines soils are still not well determined and not fully understood. To address such matter, a series of laboratory tests were performed to investigate the effects of low-plastic silty/clayey fines on the engineering and mechanical properties of clean sand. Poorly graded clean sand was mixed with fines content percentages of 0%, 10%, 20%, and 40%. The results indicate that the shear strength parameters of tested sand measured using consolidated drained triaxial tests decrease with the increase of fines content. The internal friction angle dropped from 35° at 0% fines content to 26.86° at 40% fines content. As for the sand deformability, the modulus of elasticity (E50) measured at a confining pressure of 100 kPa dropped from a value of 12823 kPa at 0% fines content to 5720 kPa at 40% fines content. The void ratio decreased as fines content increased up to 15%, then increased dramatically with further increase in fines content. Finally, to investigate the potential of using sand with fines as backfill for mechanically stabilized earth walls, the effect of fines content on interface properties between sandy soils and geogrid is also investigated by collecting data from literature and conducting regression analyses to determine the interface strength reduction factor (Rinter) to be used in the numerical modeling of such walls.