Performance of micropiled rafts in clay: Numerical investigation

摘要

The micropiled raft (MPR) offers an efficient foundation system that combines the advantages of micropiles and piled rafts that can be used as primary foundation system or to enhance an existing raft foundation. In this paper, a finite element model (FEM) calibrated and verified with centrifuge tests was used to carry out a numerical investigation on the performance of MPR in clay. A total of 26 different cases were analyzed in this study to assess the behaviour of MPR in clay taking into account a number of factors that may influence its behaviour such as: the number of micropiles (MPs), the spacing to micropile diameter (S/D-mp), the raft thickness, and type of loading. The outcomes of this investigation should help in understanding the effect of these factors on the MPR axial stiffness, including; differential settlement; load sharing between the MPs and the raft; the raft bending moment and micropiles skin friction. Moreover, the ability of the Poulos-Davis-Randolph (PDR) method to evaluate the axial stiffness of a MPR for the preliminary design stage is examined. It was found that the MPR system can increase the tolerable bearing pressure by 100% compared to an isolated raft system. In addition, an adjustment factor (omega(PR)) for PDR method was introduced to account for the raft flexibility. Equations were proposed in order to design MPR systems in terms of load sharing between micropiles and the raft.