Compression Characteristics Of Sewage Sludge As Barrier For Controlling Acid Mine Drainage

Acid mine drainage (AMD) generates from the natural oxidation of mining tailings and rocks enriched in metals sulfide minerals. From the principle of waste encapsulation disposal, a new idea of sewage sludge barrier has been proposed to control acid mine drainage. Sewage sludge barrier not only has a low hydraulic conductivity as traditional hydraulic barrier, but also posses strong reducing environment, where favor the formation of precipitation of metal sulfide. It has been proven that the sewage sludge barrier could effectively control the migration of heavy metal ions through physical blocking and chemical reactions. Therefore, it’s feasible that sewage sludge barrier deal with acid mine drainage.Compacted sludge as the main barrier material at the bottom of tailings disposal site, will suffer continuous pressure for a long time. There must be complex compression and other mechanical processes. Only by grasping the compression characteristics of compacted sludge, can we provide a theoretical reference to engineering practice. The paper briefly describes the mechanisms of sewage sludge barrier for controlling acid mine drainage. The paper mainly studies the compression characteristics of the sludge specimens, and analyzes the compression relationships of different pore solutions, with dry density and water content. By comparing and analyzing the compression properties of natural fresh sludge, modified sludge, compacted sludge and other organic soils, this paper provides a relevant parameters support for future research.The test results show that for the compacted sludge specimens of same water content, void ratio decreases with increasing dry density, eventually tending to1, and for the same dry density, the specimen’s void ratios of optimum water content reduce fastest as stress increases. The compression coefficients decrease with increasing dry density, and increase first and then decrease with increasing water content. The compression coefficient obtains the peak value in the range of60%-80%of water content, reaching0.8MPa-1under condition of optimum water content. The compression coefficient of compacted sludge is significantly less than the modified sludge and natural sludge. Compared with peat and peaty soil, the compression coefficient of natural sludge is smaller. The leachate of AMD can raise specimen compression coefficients. Therefore, in the practical application, it needs to increase the thickness of the sludge barrier material to satisfy process requirements. Theoretically the compacted sludge can be selected as a barrier material with a water content of65%, the compression coefficient of which is close to0.8MPa-1...