An experimental study of pullout resistance of a multifunctional geosynthetic in fine grained fills using an innovative pullout apparatus

This paper presents the results of a test program investigating the pullout performance of a novel multi-functional drainage-reinforcement geosynthetic and a conventional geogrid in a marginal fill. Testing investigated the influence of confining stress, pullout rate and moisture content of the soil on pullout resistance in a novel pullout rig, which facilitated pore pressure dissipation. The design of the rig and test procedures are presented. Higher confining stresses and increased moisture content in the marginal fill resulted in reduced pullout resistance for the conventional geosynthetic. Faster pullout rates generated greater pullout resistances in both the conventional geogrid and combined drainage-reinforcement geosynthetic. The reinforcement-drainage geocomposite was seen to produce higher pullout resistances than the conventional geosynthetic for all drainage conditions examined; zero, partial and full dissipation of excess pore pressures in the marginal fill. This increase was greatest at higher confining stresses and was attributed to rapid dissipation of excess pore water pressures by the drainage element of the geocomposite.