Pullout resistance of a novel multifunctional geosynthetic in fine grained marginal fills

Free draining granular fills have been the preferred choice for backfill materials for reinforced soil structures such as steep slopes owing to their good strength characteristics and ability to minimise the development of excess pore water pressures in the reinforced fill. Excess pore water pressures may result in possible stability and settlement problems. Large quantities of poor quality fine grained fills are excavated on construction sites each year. These materials can be effectively used to construct reinforced soil structures if adequate drainage is provided in the reinforced zone. This can be achieved through the use of novel multifunctional geocomposites which combine reinforcement and drainage functions. This paper presents the results of pullout testing on a combined reinforcement and drainage geosynthetic in a novel pullout test apparatus. Details of the test arrangement and operating procedures are presented. The pullout testing was performed on a marginal fill at a variety of confining pressures and moisture contents. Testing of a conventional reinforcement only geosynthetic was also performed for comparative purposes. Increasing confining stress and moisture content of the soil was shown to reduce pullout resistance while higher pullout rates resulted in greater pullout resistances. The reinforcement-drainage geocomposite was seen to produce higher pullout resistances than a conventional geosynthetic.