Experimental Study on Cemented Tailings Backfill Based on Microbially Induced Calcite Precipitation

Abstract

The backfill mining method is an effective method to control ground pressure and prevent surface subsidence in the process of underground resources exploitation. Tailings backfill not only relieves the pressure of tailings reservoir but also protects the environment. However, traditional Portland cement as the cementing material results in groundwater pollution. In addition, the production process of Portland cement consumes a significant amount of mineral resources and causes air pollution. Therefore, a cementation method for tailings based on microbially induced calcite precipitation (MICP) is proposed in this paper. Tailings cementation by the MICP technology with facultative anaerobic bacteria (Castellaniella denitrificans) can overcome the problems of MICP technology based on urea hydrolysis of aerobic bacteria (Sporosarcina pasteurii), which cannot be applied in anoxic or anaerobic environment. In addition, in view of the small amount and poor uniformity of calcium carbonate precipitation in the specimens cemented by facultative anaerobic bacteria alone, a mixture of facultative anaerobic bacteria and aerobic bacteria was adopted for tailings cementation in this study. The results showed that, with increasing Castellaniella denitrificans concentration, the cementation effect improved. The tailings sand was cemented into a compact specimen when the OD600 of the bacterial solution was one and the uniaxial compressive strength could reach 987.93 kPa. Compared to cementation induced by a single strain, the amount of calcite precipitation induced by the mixed bacteria increased from 2.54% to 3.59%, the uniaxial compressive strength was enhanced by 29.9%, and the shear strength increased by 24.4%. This study indicates that MICP technology with facultative anaerobic bacteria has great potential in tailings cementation, and it can provide a solution to replace cement as the cementing material for tailings.