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This paper describes the full-scale laboratory testing (pipe box testing) of a 380-mm-diameter, corrugated, polyethylene toe drain with a knitted geotextile sock, backfilled with a sand envelope material. The test results are compared with previous small-scale and full-scale pipe box tests using pipe with 3-mm and 6-mm perforations, but no geotextile. Use of the geotextile optimized toe drain performance both with respect to flow and with respect to loss of the sand envelope. The long-term flow rate was 260 liters per minute per linear meter of pipe, which was significantly higher (by a factor of 3 to 12) than the earlier tests without geotextile. The total loss of sand envelope was only 165 grams per linear meter of pipe, which was significantly lower (by a factor of 4 to 17) than the earlier tests without geotextile. The test with geotextile was run for 31 days at a constant head of 0.75 m above the pipe invert with no indication of clogging. Based on these results, use of geotextile sock in conjunction with a sand envelope is recommended for future toe drain installations in areas with fine-grained native soils.
geotextile, sock, knitted, drainpipe, toe drain, perforations, testing, clogging, laboratory testing, flow, soil retention, envelope
Materials Engineer Technical Specialist PE, Materials Engineering Research Laboratory, US Bureau of Reclamation, Denver, CO