Soil-geogrid interface behaviour under cyclic pullout conditions

One of the parameters necessary to design geosynthetic-reinforced soil structures is the interface apparent coefficient of friction, which allows determining the reinforced block size. The apparent coefficient of friction values to be used in seismic design based on the pseudo-static approach could be different from those used for static analyses. To evaluate this parameter, the writers carried out a series of pullout tests on HDPE extruded uniaxial geo-grids embedded in a compacted granular soil, under cyclic and post-cyclic loading conditions and for different vertical effective stress sigma'(n) values. The pullout tests have been performed at the cyclic frequency f = 1 Hz by means of a multistage procedure. In order to understand the post-cyclic behaviour of soil-geosynthetic interfaces during the pullout process, the influence of cyclic loading amplitude and sigma'(n) has been analysed.