Synergistic mechanism of physical chemistry and acid bacteria: Product evolution of sulphides during tunnel mining

Tunnel waste constitutes a prevalent by-product of highway construction in high-altitude mountainous and hilly regions. Sulphide minerals exhibit a unique distribution pattern within the alpine hills. Consequently, tunnel excavation can disrupt the stability of these sulphide minerals, rendering the tunnel waste susceptible to generating secondary environmental hazards during stockpiling. This research delves into the migration and transformation dynamics of potential environmental pollutants in tunnel waste through geoenvironmental simulation techniques. Controlled variables were employed to simulate various conditions, including surface illumination, internal anaerobiosis, water content and aerobic environments. The study's findings indicate that the presence of pyrite in the waste stream primarily drives the secondary contamination of the tunnel waste. Pyrite within the slag tends to react and form sulphuric acid in the stockpile environment, thus creating an acidic milieu that exacerbates the release of existing contaminants. The emergence of an anaerobic environment and a photocatalytic system composed of Fe/Ti substances in the waste stream serves to further accelerate pollutant release. This study thoroughly investigates the primary causes of environmental pollution during the stockpiling of tunnel slag and assesses the potential environmental impact scenarios. The outcomes of this research offer substantial theoretical and empirical support for the management of slag generated during the tunnel construction process.