Discussing the Negative Pressure Distribution Mode in Vacuum-Preloaded Soft Foundation Drainage Structures: A Numerical Study

Abstract

The aim of this paper is to clarify the negative pressure distribution in drainage structures of soft foundations reinforced by vacuum preloading. The focus of this study was an actual engineering project, the Beijing–Shanghai high-speed railway; four different soil consolidation models were established using FLAC3D to consider various loading conditions. The consolidation process of the soft foundation was calculated and analyzed in detail. The results show that (1) the settlement developed rapidly within the first 30 days, slowed during the period between 20 and 30 days, and finally stabilized. (2) The settlement curves obtained from the four different models were highly consistent with the site monitoring curve for the first 5 days, after which point significant differences appeared. (3) During the first 20 days, the pore water pressure decreased noticeably within the depth range of 0–18 m. Between days 20 and 30, the rate of pore water pressure decrease slowed down, and after the 30th day, the pore water pressure remained constant at all depths. (4) Vacuum preloading affected the soil to a depth of approximately 16 m. A concave or linear distribution of negative pressure in the drainage structure was found to be a reasonable assumption, providing a reference for the numerical analysis of vacuum preloading.