Numerical study of the deformation performance and failure mechanisms of TDM pile-supported embankments

The T-shaped deep cement mixing (TDM) pile is a technique newly used to support embankments built on soft clays. However, comprehensive studies considering the cost effectiveness have not yet been performed, and the TDM pile bending moment behavior under embankment loading is not fully understood. Hence, this paper aims to evaluate the performance of a TDM pile-supported embankment (TPSE) over soft foundation subsoils using 3D numerical modeling based on a case history of a conventional deep cement mixing (DCM) pile-supported embankment (DPSE). The performances of pile-embankment systems are investigated and discussed through several parameters, including the embankment center settlement, lateral embankment toe movement, deflection and bending moment of the pile at the embankment shoulder, and embankment stability. First, to capture the thickness effect of the uppermost fill material layer, numerical analyses with different fill material thicknesses are examined. Subsequently, extensive parametric studies of TPSE are carried out to assess the TDM pile cap size and length influences. The results of the parametric studies are analyzed and compared to those obtained from DPSE systems with equivalent embankment loading and volume between the TDM and DCM piles. Finally, a preliminary guideline for evaluating the overall improvement performance of TPSE is proposed to determine the best TDM pile cap size for each pile length in comparison with the DPSE case. Some guidelines are also defined, and small TDM piles with thicker caps are suggested to improve pile-embankment systems.