Seismic Response of Basal Geogrid Reinforced Embankments Supported on a Group of Vertical and Batter Piles

Basal geogrid reinforced embankments supported on vertical piles are proven to be a feasible and effective solution for constructing embankments over thick soft clay deposits and bridge approaching embankments. These solutions minimize the lateral displacements, total and differential settlements of embankment crest and toe by transmitting embankment loads into the deeper stratum through pile foundations and arching action of geogrid. Basal geogrid reinforcements provide good restraint against lateral spreading of the toe. Providing batter piles near the toe will further enhance this restraint against lateral spreading. Not many studies are available in literature on performance of batter piles below embankment toe, especially under seismic excitations. The present study aims to find the advantages of providing batter piles below embankment toe under seismic excitations. A 6 m high basal geogrid reinforced embankment having 1 V:1.5H side slope constructed over 28 m thick soft clay is considered for the 3-Dimensional finite element analysis. The soft clay is stabilized with 22 m long 300 mm diameter vertical and batter piles spaced at three times the pile diameter. Embankment crest vertical displacements, toe horizontal displacements, maximum differential settlements at the crest and crest lateral accelerations are analysed for different batter angles of 0°, 5°, 10°, 15°. Analysis of results reveals that larger the batter angle more is the reduction of toe horizontal displacements.