A Novel Analytical Solution for Slurry Consolidation Induced by a Vacuum-Assisted Prefabricated Horizontal Drain

Vacuum preloading via prefabricated horizontal drains (PHDs) is an efficient technique to accelerate the consolidation of dredged soft soils. However, this technique lacks a clear and concise theoretical solution to the PHD vacuum consolidation analysis for slurry. To address this issue, this study proposes a novel analytical solution based on a mathematical logical procedure. The governing equations are first derived based on square PHD consolidation unit cells given the assumption of equal strain, taking into account various drainage conditions at the boundaries and the horizontal and vertical spacings of PHD. A seepage direction coefficient, directly determined through PHD spacing without additional identification, is further introduced into the derived formulation to enhance the solution to be more consistent with the results of free strain consolidation analysis. Then, the proposed analytical solution is validated based on three laboratory and field tests. The proposed solution is successfully applied to estimate the consolidation behavior at a site in Aomori Prefecture, Japan, involving PHD vacuum preloading. All results demonstrate that the proposed analytical solution is applicable for the design and management of PHD vacuum preloading construction projects and practically useful for engineers. Furthermore, the influences of the large strain effect, variable hydraulic conductivity, and variable compressibility on the consolidation analysis are discussed.