الفهرس | Only 14 pages are availabe for public view |
Abstract Piles are one of the widely spread used systems to transfer high level of stresses to deeper soil strata when the subsurface strata cannot bear the needed stress level. Piles are commonly connected using a raft to maintain group action and to ensure overcoming any expected differential settlement. Although the raft is in direct contact with the sub- surface strata, conventional design systems ignore the load transferred from the raft to the soil due to this contact and encounter on the pile group bearing capacity and settlement. This system is named as pile group system. The behavior of piled raft system depends on many factors starting from the behavior of single pile (pile-soil interaction) to the raft-soil interaction and the pile-soil-pile interaction. This fact highlights the importance of studying single pile load transfer mechanism prior to the study of group action to be able to validate the main parameters used in modeling. For the sake of validating the software package used and the estimation of the different input parameters needed for the modeling of different pile group system, a pile load test that was performed on ALZEY Bridge in Germany conducted by Sommer & Hammabach (EI-Mossallamy 1999) was chosen to be numerically modeled and the analysis results were compared to the results obtained from field. Different parameters affecting the pile-soil interaction were examined and compared to the field results to select the most representing parameters for the shaft interface and the pile tip interface element simulating the real behavior of the pile in the field To study pile group action and the effect of the raft contact in the piled raft system, pile group was modeled with and without full raft contact with the soil. Calculated loadsettlement curves for both systems were compared. Moreover load-settlement curves of different pile positions were investigated to study the effect of pile arrangement (position) on the load transferred by the pile. Studying the effects of piles spacing and length to diameter ratio was also conducted to evaluate the different parameters affecting the piled raft system. Finally, the capacity of selected piled rafts were examined and compared to the procedure suggested by Poulos (2002). |