Seismic Response of Geocell Retaining Walls: Experimental Studies

This paper summarizes the seismic response of five large-scale retaining walls having a geocell facing. The walls were $2.8\mathrm{m}$ high and the backfill and foundation soil were a fine sand compacted to 90% standard Proctor density (relative density of 55%). The first two walls were of the same geometry, with a tapered facing made of geocells each of height $20\mathrm{cm}$ , one infilled with gravel and the other with sand. In Wall 3, a facing of depth $60\mathrm{cm}$ was constructed while the backfill sand was reinforced with a polyester geogrid. Wall 4 was similar to Wall 3 except that the backfill was reinforced with several geocell layers. Wall 5 had thin geocell layers of $5\mathrm{cm}$ height as reinforcements in order to improve the performance compared with Wall 4. The walls were subjected to the scaled horizontal and vertical motions as recorded during the 1995 Kobe earthquake, $4.5\mathrm{m}∕{\mathrm{s}}^2$ $\left(450\mathrm{gal}\right)$ and $9.0\mathrm{m}∕{\mathrm{s}}^2$ $\left(900\mathrm{gal}\right)$ maximum horizontal accelerations in the first and second excitations, respectively. In an attempt to induce failure, and therefore, to investigate the failure mechanism, Walls 3–5 were subjected to a third shaking in which the horizontal accelerations were scaled to $12.0\mathrm{m}∕{\mathrm{s}}^2$ $\left(\mathrm{1,200}\mathrm{gal}\right)$ . The walls were fully instrumented with accelerometers, laser displacement transducers, force transducers, and strain gauges. All five walls performed satisfactorily under the simulated earthquake motions. An improved wall performance was seen with the geocells acting as reinforcement layers. The study showed that geocells can be used successfully to form gravity walls as well as reinforcement layers even when subjected to a very high seismic load beyond that of the Kobe earthquake.