Free-Strain Consolidation of Soft Ground Improved with Alternating Length PVDs

Abstract

In practice, installation of alternating length prefabricated vertical drains (PVDs) cannot only satisfy the strength requirements for the upper soil layer, but also improve the lower soil layer to a certain extent, which is conducive to improving the overall strength and stability of the ground. In this paper, the original three-dimensional consolidation model for alternating length PVDs is simplified into a plane equivalent model, considering only well resistance by the model equivalence technique. Subsequently, a novel semi-analytical solution for soft ground with alternating length PVDs is derived using the boundary transform and local discretization methods. Accuracy analysis of local discretization is conducted to determine the appropriate segment number for PVD-soil interface boundaries. The effectiveness of the proposed solution is demonstrated by comparing the results from numerical analyses. Finally, the influence of the penetration depth of short and long PVDs on the consolidation efficiency is studied. Results show that the installation of alternating length PVDs is more effective compared to the conventional scheme of equal length installation. Both the average degrees of consolidation within and below a design depth for the ground with alternating length PVDs are higher than in the case with equal length PVDs.OPEN ACCESS Received: 20/03/2025 Accepted: 22/05/2025 Published: 14/07/2025

Document