| Slope reinforcement using geosynthetics is a relatively new technology in geotechnical engineering. Most of the research work in the literature is focused on reinforced slopes constructed with granular materials. To achieve a better understanding of the reinforcement mechanism of cohesive soil slopes and to provide guidelines for design and construction of reinforced cohesive soil slopes, a test fill was built near Devon, Alberta.; The test fill, 12 m high with 1:1 side slopes, was constructed in three stages. There are four sections in the test fill. Three sections were reinforced with different geogrid materials, namely Tensar SR2, Signode TNX5001 and Paragrid 50S, and the fourth section was unreinforced for the purpose of comparison. The test fill was monitored using extensive field instrumentation, including electrical wire resistance strain gauges, inductance coils, horizontal and vertical extensometers and inclinometers, and piezometers. Field measurements were taken during and after the fill construction and were interpreted as tensile strains in the geogrids, horizontal and vertical deformations of the fill and the foundation soils and pore pressures in the fill and the foundation soils.; Stability analyses of the reinforced slopes were conducted using limit equilibrium methods. The modified Bishop's method, modified Spencer's method and the two-part wedge method were used. Calculated factors of safety and predicted failure surfaces were compared with the field measurements and observations. It was concluded that the failure modes of reinforced cohesive soil slopes are rotational shear surfaces and that the modified Bishop's method is the most appropriate method for stability analysis in practice.; Based on the field measurements, the reinforcement mechanisms of cohesive soil slopes were analyzed in aspects of horizontal and vertical load transfer. It was found that the geogrids stabilize the soil by allowing horizontal load transfer from overstressed zones to understressed zones of soil and by reducing the vertical transfer of horizontal loads from the soil above a reinforcement layer to the soil below the layer. The interaction between the soil and the geogrids in both the resistant and active zones was also analyzed. Implications of the analyses and recommendations on design methods are discussed as the practical significance of the research. |
