Mechanical Behavior of Mine Overburden Soil Stabilized Using Calcium-Based Stabilizer Used for Pavement Application

Abstract

Mine overburden material (OBM) is the discarded soil–rock mixture, which is abundantly dumped around coal mines. These dumps create a lot of instability and environmental issues. The present study attempts to sustainably utilize the mine OBM in the construction of mine haul roads. Mine OBM is generally a soil–rock mixture with differently graded materials lacking the specific requirements for use in pavement subgrade. To utilize the OBM, stabilizers like lime and cement alone may not work due to the heterogeneity of the OBM. Hence, Road Building International (RBI) grade 81, a novel calcium-based stabilizer was used in this study to increase the mechanical properties of the soils, as it can stabilize various ranges of soils. The collected soils were silty sand (SM), intermediate compressible clay (CI), and clayey sand (SC), which possessed different plasticity characteristics. To assess the strength properties of modified mixtures, the California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were conducted along with rutting resistance at different curing periods. The study shows that increasing RBI content enhances the soaked CBR values, with a peak of 135% for stabilized mixtures (SM) soil stabilized with 4% RBI. While the UCS values rose 16 to 18 times, reaching 1,355 kPa for intermediate compressive clay (CI) soil with 4% RBI. Wheel tracking tests demonstrated a 5 to 30-fold reduction in rut depth, dropping below 1.5 mm at 520 kPa stress, even at lower RBI levels for all composite mixtures. The use of RBI has proven to be effective in increasing the subgrade performance for all types of soils in OBM, while for CI soils it is more effective.