Mechanism of pore water seepage in soil reinforced by step vacuum preloading

Abstract

A laboratory model experiment of step vacuum preloading (SVP) for dredger fills was performed. The soil moisture content and water discharge rate were measured. The seepage mechanism of pore water was analyzed based on the theory of drainage consolidation. The results indicated that the seepage fluid mostly consisted of free water during self-weight sedimentation and under 10 kPa vacuum pressure in the SVP test. The stage corresponding to the application of 20 kPa vacuum pressure was the transitional stage in which both the free water and the loosely bound water participated in the seepage. When higher vacuum pressure was applied, the loosely bound water mostly participated in the seepage. In the SVP test, the complete potential difference channels were established in the test bucket during self-weight sedimentation. The vacuum channels at the center began to form when 10 kPa vacuum pressure was applied, and the free water near the sidewall was discharged through the potential difference channel. With 20 kPa vacuum pressure, the vacuum channel developed continuously from the drainage board to the sidewall of the test bucket, completing the process and ultimately stabilizing as the vacuum pressure increasing. The study of the seepage mechanism of pore water during SVP test is significant for the analysis of pore water seepage under vacuum pressure during the consolidation of soft soil foundation. This study contributes to the existing theory related to vacuum preloading consolidation methods, providing theoretical guidance for the analysis of soil consolidation under drainage conditions.