Shaking table tests on combined use of EPS and geogrid to improve seismic stability of bridge abutments

In order to study the effects of combined use of EPS (block of expanded polystyrene) and geogrid to improve seismic stability of bridge abutments, a series of 1-g shaking table tests are conducted on a reduced-scale model of a cantilever type bridge abutment and its backfill soil. The test results re-vealed that, under severe excitation conditions at 700 to 1000 gals, both the base sliding and the tilting of the wall could be reduced by placing geogrid-reinforcement in the backfill soil. In addition, instead of placing the upper geogrid-reinforcement, the base sliding of the wall could be further reduced by replac-ing partly the backfill soil with blocks of EPS in combination with the use of the middle-height geogrid. Placing EPS blocks above the middle-height geogrid was more effective than placing them below the geogrid. The relative settlement of the backfill soil at the interface with the wall could be also reduced by the combined use of EPS and geogrid.