The short- and long-term compressive behavior of high-density polyethylene geonet and geocomposite under inclined conditions

The short- and long-term compressive behavior of high density polyethylene (HDPE) geonet were evaluated at four inclined conditions: the horizontal (0°), 1(V)-to-5(H), 1(V)-to-4(H), and 1(V)-to-3(H), to investigate the effect of the combined stresses (i.e., normal and shear) on the side slope of the landfill. The results of short-term compressive tests indicated that the compressive strength was largely unchanged at different inclined conditions; whereas the compressive strain increased with degree of inclination. The long-term compressive behavior (i.e., creep) was evaluated using the stepped isothermal method (SIM). Applied stresses at 20 % and 60 % of normal compressive strength were used at four inclined conditions. The results indicated that the creep compressive strain increased with degree of inclination at both applied stresses. The primary creep stage was observed at all inclined conditions under the applied stress of 20 % and at the horizontal and 1-to-5 under the applied stress of 60%, while the onset of secondary creep stage was obtained at inclined conditions of 1-to-4 and 1-to-3 under the applied stress of 60%. In addition, the creep reduction factors were calculated using the strain at 104 hours. The reduction factor increased with degree of inclination, particularly at inclined conditions that exhibited secondary creep stage