Behaviour of a geosynthetic reinforced steep slope constructed with cohesive backfill under earthquake loading

Abstract

The use of geosynthetics as reinforcement elements of granular backfills has been widely used and their behaviour either during the service life or under seismic loading has been studied by several authors [1, 2]. However the use of fine grained soils, often referred as marginal fills, are not strongly implemented and, since they are susceptible for pore water pressure, not recommended by some international guidelines and standards. The use of soils locally available has cost benefits and sustainable gains. Therefore it is important to study the behaviour of geosynthetic reinforced steep slopes constructed with cohesive backfills. In this work the two-dimensional finite difference program Fast Lagrangian Analysis of Continua (FLAC) was used to model the seismic behaviour of an 8.4 m high geogrid-reinforced steep slope. The embankment was reinforced with 14 horizontal reinforcement layers and its face is inclined of 60°. The seismic behaviour of the structure constructed with cohesive backfill was compared to its behaviour if a granular material was selected. Two constitutive models were used to model the cohesive backfills: the Mohr-Coulomb model and a Strain-Softening model. In order to investigate the influence of input motion on the seismic behaviour of the structure, two earthquake ground motions artificially generated and two variable amplitude harmonic motions were considered. The numerical simulations of the structure behaviour under seismic loading showed that the possible decrease of the backfill shear strength properties with the shear strain during cycling is an important issue. Even so, it could be concluded that a well compacted and drained cohesive soil can be used as backfill material in geosynthetic reinforced steep slopes.