ABSTRACT
ABSTRACT: Post-earthquake investigations were performed for three types of geotechnical structures, including geosynthetic-reinforced soil block walls, concrete-covered earth-core levees, and soil retaining walls. Comparative studies were also performed based on the result of soil borings, soil testing, and pseudo-static analyses to highlight the mechanism controlling different seismic-resisting behavior. It was found that seriously damaged soil structures in the 1999 Chi-Chi earthquake were always intrinsic with deficiencies resulted from bad design and/or construction practices. Two geosynthetic-reinforced modular block walls with excessive displacements or collapsed facing columns were found to have a vertical spacing of reinforcement equal to 0.8 m and a relatively loose backfill with an internal friction angle of about 30◦. A synergistic effect of large vertical spacing of reinforcement and low backfill strength accounted for the excessive lateral thrust and deformation of the wall. A seriously damaged earth levee with a plain concrete cover exemplifies another bad practice of placing a brittle structure on a deformable (or liquefiable) foundation. Some leaning-type soil retaining walls built on hillsides suffered great settlement and lateral movement during the earthquake. It was found that these damaged leaning-type retaining walls had small base width to wall height ratios, resulting in low safety factors against failure even under static conditions.
