The scale direct shear test effect on the shear strength characteristics of different sands in Lahore, Pakistan

Abstract

The direct shear test is a widely used method for determining soil and material shear strength parameters. This study examines the impact of shear box size on the shear strength properties of poorly graded sands collected from Lahore, Pakistan. Sand samples were classified using the Unified Soil Classification System and tested at dry densities ranging from 1.601 to 1.825 g/cm3 using shear boxes with 60 mm, 100 mm, and 160 mm diameters. Tests were performed at a constant rate of 1.25 mm/min under normal stresses of 23.42, 35.76, and 48.11 kPa. Results indicate that increasing box size leads to higher cohesion and lower friction angles, while increasing soil density enhances both parameters. Regression relationships were developed to relate small-scale and large-scale test results. These findings underscore the importance of accounting for scale effects in laboratory shear testing and offer guidance on extrapolating small-scale results to design applications. The study highlights the significance of considering container size effects in the interpretation of laboratory shear tests. Future research may explore varying soil types and moisture contents to generalise these findings further. Understanding these scale effects is crucial for improving the accuracy of geotechnical assessments and ensuring safe construction practices