Reply to the two discussions on my paper "An alternative mechanism of pile failure in liquefiable deposits during earthquakes"
This paper proposes an alternative mechanism of pile failure in liquefiable deposits during earthquakes. This failure mechanism, based on pile buckling, is formulated by back-analysing 14 case histories of pile foundation performance during earthquakes and verified using dynamic centrifuge tests. A new parameter, the slenderness ratio of a pile, is introduced to classify pile performance in liquefiable soils. This parameter fits very well both the reported case histories and the centrifuge test results.
BUILDING DAMAGE ASSOCIATED WITH GEOTECHNICAL PROBLEMS
ABSTRACT 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.
Design procedures for dynamically loaded foundations
Practical methods for the analysis of foundations subjected to dynamic loadings are discussed and design methods are proposed. These methods use a system of lumped masses, springs, and dashpots approximately equivalent to the actual foundation soil system. The key step of evaluating the lumped parameters of the system was obtained from the theories of footings resting on semi-infinite elastic bodies.