Shear mechanical property of soil-rock mixture based on large-scale laminated ring shear test

ObjectiveTo simulate the shear deformation during geotechnical engineering and reveal the shear mechanical properties of soil-rock mixture more accurately, an apparatus for large-scale laminated ring shear test was developed.MethodFirst, the ring shear test and direct shear test were conducted on soil-rock mixture with rock block proportion of 60%. The shear strength, strength parameters, and relational features between shear stress and shear-displacement ratio, measured with two test methods, were compared in detail. Subsequently, the laminated ring shear test was conducted on soil-rock mixture with different rock block proportions, investigating the influence of rock block proportion on shear stress-shear displacement curves, shear strength and strength parameters.ResultThe final shear strength obtained from laminated ring shear test is higher than that from direct shear test; and its stress-strain curve can be divided into three stages of shear densification, nearly elastic and strain hardening. The shear strength is positively correlated with rock block proportion and normal pressure, conforming to the Mohr-Coulomb strength criterion. The variations of shear stress-shear displacement curves are similar for soil-rock mixture with different rock block proportions; while the shear strength parameters vary significantly. The cohesion decreases with an increase of rock block proportion, while the internal friction angle increases. Moreover, cohesion is more sensitive to the variation of rock block proportion. The relation between rock block proportion and cohesion, as well as the relation between rock block proportion and internal friction angle, both exhibit the power function relation.ConclusionThe proposed apparatus can more accurately reflect the shear properties of soil-rock mixture. The rock block proportion is a key factor affecting its mechanical properties, and the power function can provide reference for the selection of engineering parameters.