Liquefaction Resistance of Thickened Tailings

Abstract

A new method is presented for analysis of the potential for triggering liquefaction, i.e., a flow slide, in liquefiable soil masses. The method is based on the principle of steady state deformation. In conventional mine tailings disposal operations, the tailings are pumped as a water suspension into extensive flat containment ponds. These ponds generally are formed by construction of large tailings dams. However, if the tailings are thickened substantially before discharge, the tailing slurry will form a sloping deposit. Maximum slope angles of 3.5° are normally recommended. Use of thickened tailings is less costly and has much less environmental impact than conventional tailings because tailings dams and their associated slime ponds are eliminated. In this paper, the resistance to liquefaction due to earthquakes of a proposed bauxite tailings deposit placed at a 2.9° slope is analyzed. The water content of the thickened tailings is high enough to make them susceptible to liquefaction even when placed at such gentle slopes. However, due to the clay content and thixotropic nature of these tailings, earthquakes that induce 0.1 g peak ground acceleration do not cause enough strain to trigger liquefaction.