Estimation of resilient behavior of crushed waste rocks using repeated load CBR tests

Abstract

Crushed waste rocks (CWR), generated from mining operations, have been widely used for the construction of mine haul roads because of their low-cost, high-strength, and availability. Resilient modulus is a necessary input to mechanistic design for mine haul roads, but its determination usually requires advanced and complex equipment such as repeated load triaxial (RLT) test. Repeated load CBR (RLCBR) tests are simpler and more often available, and were therefore investigated in this study to estimate CWR resilient behavior under low and high stress levels. RLCBR equivalent modulus calculated using various equations were validated using RLT resilient modulus. The MR-θ model showed good representation and prediction of CWR resilient behavior under both low and high stress levels. A new equation was also proposed to predict more precisely the equivalent modulus of CWR based on RLCBR tests. Results showed that the impact of loading frequency and waveform was limited, while the measured equivalent modulus increased significantly with contact stress (especially when contact stress < 10%). The effect of dry density and soaking on equivalent modulus was negligible, but specimen drying resulted in a marked increase of the equivalent modulus. The good agreement between RLCBR equivalent modulus and RLT resilient modulus indicates that RLCBR tests could be an effective alternative to RLT tests to estimate resilient behavior of CWR used in mine haul roads.