Abstract: Defects exist in vertical reinforcement, such as drainage capacity and large bearing capacity cannot be achieved at the same time. This study developed a new type of porous pipe pile with drainage function. It is assumed the tube flow for pore fluid, and the continuous pore pressure according to Poiseuille equation. Then, the analytical solution of strain consolidation is deduced. The drainage pile presents the best consolidation capacity compared to sand drain, gravel pile and undrained pile. The effect of pile modulus, mattress modulus and radius ratio on consolidation are also analyzed. Drainage capacity and modulus are two main factors that affect the consolidation performance. The drainage capacity is the most important. Within the same drainage capacity, greater the modulus of the pile produces faster consolidation process.

Key words: composite foundation, porous pipe pile, consolidation analysis, drainage capacity, modulus