A new macro-element method with water absorption and discharge functions proposed by the authors was incorporated into a soil-water coupled finite deformation analysis code capable of accounting for inertial forces and verified by simulating an actual ground behavior observed in a peaty ground improved with vertical drains and vacuum consolidation. It was found that the proposed method was capable of simulating a range of ground behaviors including the temporal change in pore water pressure, horizontal displacement, and the settlement of the surrounding ground. Because a continuous middle sand layer was found to exist spanning the entire improved area at the actual site, additional simulations were performed to elucidate the effect of this layer. Furthermore, based on a series of simulations with a particular focus on the influence of drain spacing, it was revealed that although the vacuum consolidation method is effective in cases where it is necessary to limit deformation of the surrounding ground, the same reduction in residual settlement can be achieved using vertical drains alone, provided that the drains are deployed at a sufficient frequency.