Study on the pore water pressure dissipation method as a liquefaction countermeasure using soil-water coupled finite deformation analysis equipped with a macro-element method

A numerical simulation of the pore water pressure dissipation method was performed using the GEOASIA soil-water coupled finite deformation analysis code, which is capable of accounting for inertial forces, together with the elasto-plastic constitutive SYS Cam-clay model based on the soil skeleton structure concept, with the goal of quantitatively assessing the effects of this method as a countermeasure to liquefaction. At the same time, an effort was made to improve/enhance the calculation efficiency of the GEOASIA analysis code by incorporating a macro-element method, which up to this point has only been applied to consolidation problems. The main findings of this study are as follows: (1) the macro-element method is capable of yielding highly accurate approximations even for dynamic problems, (2) the method is capable of reproducing the suppression effect of the increase in pore water pressure associated with the pore water pressure dissipation method, even when a relatively coarse mesh is used, (3) the method is capable of reproducing the suppression effect of the decrease in effective stress due to the pore water pressure dissipation method, along with the resulting reduction in shear stiffness, lateral ground movement, and settlement and (4) it is possible to efficiently design the pore water pressure dissipation method with this method by first performing calculations using a 1-D mesh to determine the effective drain spacing prior to performing calculations using 2-D or 3-D meshes.