| Liquefaction-induced lateral spreading has caused substantial damage to pile foundations. Large uncertainties remain regarding lateral spreading and its effects on pile foundations. Of special concern are the associated maximum soil pressure on piles due to lateral spreading, and the potential relevance of vertical earthquake ground motions.; To address these issues, the characteristics of vertical motions were first investigated. Effects of these motions on lateral spreading were subsequently examined by a finite element study. To improve the understanding of pile behavior during lateral spreading, a unique set of large scale one-g shake-table data was analyzed. Within this scope, six experiments were conducted to augment data from additional tests in Japan. A three-dimensional solid-fluid fully coupled dynamic finite element study was also conducted.; It was found that significant high frequency prevailed in all seismic vertical motion records. Site distance from source had a noticeable effect on spectral shape. A simple one-dimensional vertical wave propagation model did not appear adequate for modeling available seismic downhole array records. For the studied saturated ground scenario and earthquake motions, the inclusion of vertical component resulted in significantly larger lateral displacement.; Data from the shake-table experiments showed that maximum lateral soil pressure on piles was found to occur immediately upon liquefaction. This pressure was found to be considerably higher than some current recommendations. A liquefied passive pressure procedure is proposed based on the results of the experiments. In this procedure, a small friction angle of about 3° was found to characterize the strength of liquefied soils. In the observed response, a reduction factor of about 0.5 was found to crudely account for pile group effects and shadowing effects. Finite element simulations show apparent pile pinning effects that may significantly reduce the extent of lateral spreading of the ground. |
