Effect of drainage conditions, bed thickness, and age on the shear strength of mine tailings in a very low stress range

摘要

The present study utilized a specially built tilting tank to measure the shear strength of deposited mine tailings beds under different degrees of drainage and in the stress range below 1 kPa. Two modes of tilting were employed to simulate drained and partially drained conditions. The slow tilting mode ensured that the excess pore pressure generated in the tailings bed in response to shearing remained low and did not influence the shear strength of the bed. During rapid tilting, the excess pore pressure build-up was significant and ultimately led to bed failure. Failure occurred at a plane parallel to the surface of the bed and at a depth of 0.4 to 1.5 cm. Linear drained and partially drained shear strength envelopes with zero cohesion intercept were defined over the vertical stress range of 0 to 1 kPa. The effective friction angles were determined to be 40.4° and 40.8° for the 3 and 12 day old beds, respectively. For beds of the same thickness and age, the total friction angles obtained from partially drained tests were 23.3° and 23.8°, respectively. Small variations in total and effective friction angles with consolidation time were observed.