Seismic displacements of geosynthetic-reinforced soil modular block walls

Four geosynthetic-reinforced soil modular block (GRS-MB) retaining walls that behaved differently during the 1999 Taiwan Chi-Chi earthquake were investigated by field surveying and soil testing. Pseudo-static analyses based on the two-wedge failure mechanism were performed to investigate the seismic stability of such GRS-MB walls. The analyses considered the structural function of the stacked block facing and the contribution of reinforcement-facing connection strength to the seismic stability of GRS-MB retaining walls. It was found that the facing-reinforcement connection strength and the block-block shear resistance strongly affect the seismic stability and seismic displacement of GRS-MB retaining walls. Newmark's sliding block theory together with a 'displacement diagram' were used to evaluate the seismic displacements of the investigated walls. The displacement analyses give the values of horizontal seismic displacement of the discrete modular block facing and the vertical settlement of the backfill soil. It was found that the calculated values of wall displacements were comparable with the measured ones when the structural effects of the facing were properly accounted for. The effect of buckling mode deformation of the stacked blocks on the horizontal displacement of the GRS-MB walls is also evaluated quantitatively.