Investigation and Analysis of a Pile Foundation Damaged by Liquefaction during the 1995 Hyogoken-Nambu Earthquake

ABSTRACT During the 1995 Hyogoken-Nambu earthquake, extensive liquefaction occurred on reclaimed lands causing serious damage to pile foundations. This paper reports the investigation of the damage to a pile foundation located in a liquefied soil as well as the results of its static and dynamic response analyses. Three piles of the building were examined by inserting a remote controlled television camera and an inclinometer into the hollow spaces of the piles. Serious damage was observed at the bottom of the fill where the piles were bent toward southwest. No serious damage was observed near the pile heads except for a shear crack found on one pile. Dynamic effective stress response analyses were conducted on a soil column and a soil-pile-building system and the process of the damage to piles was analyzed. The effect of the non-liquefied crust overlying liquefied soils on pile stresses due to inertial force is analyzed in detail, and the soil stiffness to be used in analyses is proposed. Pseudo-static analyses were conducted using a model consisting of a beam on nonlinear Winkler type springs. The effects of input parameters and the applicability of the pseudo-static analysis are examined by comparing the numerical results with the observed damage and with the results of the dynamic analyses.