A general solution for leakage through geomembrane defects overlain by saturated tailings and underlain by highly permeable subgrade

Abstract

Experimental data is presented for leakage through slits, square, and rectangular geomembrane defects overlain by silty sand tailings and underlain by a well-graded gravel. The rectangular GMB defects have a range of widths, B, lengths, L, and aspect ratios (L/B), and ratios of defect length to thickness of tailings above the geomembrane (L/T). A blade cut slit (or simulated stress crack) widens to an extent dependant on the subgrade and stress level. For L= 100 mm, increasing B (0.15 < B/L ≤ 1) from 1.6 (slit) to 100 mm (square), decreases the leakage from about twice to essentially the same as that for a circular hole of equal area. The ratio (h1/H) of head loss within the hole, h1, relative to the total head loss, H, is independent of loading conditions and constant for any particular hole shape (B/L), area (B∙L), and relative depth (L/T). A semi-empirical general solution is developed for a rectangle within the range of 0 ≤ B/L ≤ 1 with the solution converging to that for a strip for B/L→ 0 and to a circle for B/L→ 1. The solution gives calculated leakage in encouraging agreement with the experimental data.