Effects of Scalping on Direct Shear Strength of Crusher Run and Crusher Run/Geogrid Interface

Abstract

Crusher run is a type of construction aggregate produced in a quarry by breaking down the rock to various sizes using a mechanical crusher. Scalping is an essential process for a quarry to produce a series of crusher run products with specific grading specifications for various applications. To study the effects of scalping on the direct shear strength of crusher run, large-scale laboratory direct shear box tests were carried out on crusher run specimens scalped to pass 75, 37.5, 19, 9.5, 4.75, and 2.36 mm. Furthermore, to study the effects of scalping on interface shear strength between the crusher run and a geogrid, interface shear tests were also carried out between the crusher run scalpings and a geogrid reinforcement. The direct and interface shear-strength results were then analyzed to investigate the effects of scalping on the direct and interface shear stresses, failure envelopes, direct and interface friction angles, apparent cohesions and adhesions, and interface efficiencies. Sieving analyses were carried out before and after the shear tests to assess the degree of particle breakdown caused by loading and shearing in the direct and interface shear tests. The experimental shear test results show that scalping can cause a pronounced reduction in the direct and interface shear strengths. The results of the sieving analyses imply that the overall particle breakage of the crusher run specimens caused by large-scale direct and interface shear testing was not significant within a normal stress level of 1,000 kPa; however, some large-particle crushing on the top surface of the specimens was observed.