Geotechnical Evaluation of Gold Mining Tailings-Silty Soil Mixtures for Road Subgrade Construction

The present investigation examines the utilization of gold mining tailings blended with a silty soil as a pavement material. Gold mining tailings present a significant environmental concern. Tailings storage facilities pose risks to nearby communities and occupy valuable land that could be utilized for other purposes. Incorporating these tailings into road subgrades offers a potential solution to address this environmental issue in a sustainable manner. A series of geotechnical tests were performed to evaluate this application. According to Unified Soil Classification System, the soil and gold tailings were classified as SM and ML, respectively, with high bulk specific gravity and a predominance of silt and clay particles. The compaction curve of the soil shows that the tailings' maximum dry density is lower than the soil's due to their higher specific gravity. The incorporation of 10% and 20% tailings into the soil modifies its compaction characteristics. While the California bearing ratio values of the natural soil and soil-tailings mixtures meet the minimum design values for subgrade applications, the tailings alone do not meet the minimum requirements. The expansion results indicate that the pure soil has a volumetric expansion between 1.15 and 1.54, which meets the Peruvian standard's threshold of 2% for subgrade layers. Additionally, the soil-tailings mixtures with a dry density higher than 1.75 g/cm³ exhibit expansion values below 2%. This study demonstrates the potential use of gold mining tailings mixed with a silty soil as pavement base material.