Experimental Investigation of Influence of Air-Boost Pressure and Duration on Air-Boost Vacuum Preloading Consolidation

Abstract

The air-boost vacuum preloading method has become popular in soft soil foundation reinforcement, especially in land reclamation projects. However, there are still some consolidation mechanism issues that need to be investigated, especially with respect to the determination of the air-boost pressure and duration. In this study, a set of macro- and microlaboratory tests including scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) were carried out to investigate the improvement effects of different working pressures and durations. The test results indicated that air-boost vacuum preloading can enhance the consolidation efficiency, and the water discharge and surface settlement distinctly increased after gas injection. As a result, the tests with higher pressures and longer durations have higher strength and increment of the degree of consolidation (DOC). In some ranges, the higher pressure leads to the longer consolidation period, and the longer duration improves the effectiveness of each pressurization cycle. Based on the result analysis, the air-boost vacuum preloading process after pressurization could be divided into three stages, and the second stage was the most sensitive to changes in the air-boost pressure and duration. Furthermore, the increasing setting of air-boost pressure and duration was more suitable for the consolidation process in air-boost vacuum preloading.