Hydraulic response and oxygen barrier performance of earthen cover constructed with solid wastes: from soil column test to field demonstration

Reducing the source of acid mine drainage is very important for the ecological restoration of acid mines and tailings dumps. The research and development of earthen cover constructed with solid wastes is of great scientific and engineering value for achieving seepage prevention, oxygen barrier and reducing generation of acidic mine drainage in acidic solid waste sites. In this paper, typical solid wastes, e.g., neutralization slag and construction muck were used to construct a composite earthen cover, and its performances in reducing water percolation and oxygen entry at the base of the cover were studied through soil column test and field demonstration in turn. Firstly, the indoor soil column test was carried out. Soil column test results showed that the oxygen flux of this earthen cover was 0.48 mol/(m2*year), which was lower than the 2 mol/(m2 * year) in North America; No bottom leakage was found in the cover after applying an extreme rainfall with 50-year return period in the humid area of southern China. Thereafter, the first full-scale test of earthen cover constructed using solid wastes was built in acid mining dumps in Sui Chang Gold Mine, Li Shui City, Zhejiang Province. Its anti-seepage and oxygen barrier performance were monitored for one year so far. During the one-year monitoring period, the total rainfall was 1193.2 mm, and the cumulative leakage at the base of the cover was 20.0 mm, which meets the annual leakage control standard of 30 mm in North America. The oxygen flux during monitoring was 0.75 mol/(m 2*year), which was less than the North American oxygen flux control standard of 2 mol/(m2 * year). The vegetation in the experimental area grows well, covering 100% area. These results show that the earthen cover constructed with solid wastes has broad application prospects in reducing water percolation and oxygen entry at the base of the cover in acid solid waste dumps, leading to a significant reduction of acid mine drainage.