BUILDING DAMAGE ASSOCIATED WITH GEOTECHNICAL PROBLEMS

An overview of the geotechnical aspects of the building damage in the 1995 Hyogoken-Nambu earthquake is presented. It is shown that (1) the damage to buildings was caused by either strong ground shaking or ground problems, each of which combined with inadequate design of buildings, and (2) the pattern, extent, and distribution of the damage were significantly affected by local soil conditions as well as ground failures including soil liquefaction. Typical features of the ground problems are settlement and/or tilting of buildings. Possible causes of the foundation damage include : (1) horizontal forces and overturning moments imposed on the foundation from the superstructures, (2) kinematic forces acting on deep foundations due to shear deformation of soils, (3) reduction in bearing capacity due to ground failures including liquefaction, and (4) lateral spreading. The damage to pile foundations caused by Categories (1) and (4) has posed particularly serious problems. Despite extensive soil liquefaction, the engineered buildings on Port and Rokko Islands performed relatively well, probably due to (1) ground surface motions attenuated by soil liquefaction, and (2) indirect effects of foundation designs related to consolidation settlement. The buildings for which remedial measures were undertaken to mitigate liquefaction hazards, were found to have performed well.