Model Pile Pull-Out Tests Using Polyethylene Sheets to Reduce Downdrag on Cast In Situ Piles

摘要

Low-density polyethylene sheets (LDPE) were used in this study to investigate its effectiveness in reducing downdrag on cast in situ piles. Eight model pile pull-out tests were conducted using three reinforced concrete circular model piles with different surface conditions (smooth, smooth with necking and bulging, and rough) in combination with three different LDPE sheet arrangements (one-sheet, two-sheet, and three-sheet). The pile was embedded partially in Ottawa sand with a surcharge of 19.3 kPa on sand surface. The test results showed that an arrangement with 3 pieces of 0.25-mm thick LDPE sheet was most effective in reducing side friction up to an average of 89%. It was also found that the effectiveness of LDPE sheets is independent of the concrete surface roughness. However, the presence of necking and bulging was found to increase the side resistance up to 40% for the plain pile without LDPE sheets.