Behavior and Impact of Vacuum Pressure and Pore Pressure during Monitoring Process of Vacuum Preloading

ABSTRACT During the monitoring process of vacuum preloading, varying measurement operations lead to discrepancies in the recorded values and interpretations of vacuum pressure (VP) and pore water pressure (PP) persist. This study presents a series of vacuum preloading tests to investigate the attenuation patterns of VP and PP in soil across different locations and their relationship. The impact of several operational factors, including distance from the drainage boundary, water content, groundwater, vacuum pump power, and vacuum pipe length, is analyzed. Results show that VP and PP in the soil changed consistently during vacuum preloading, and both attenuated from the input 98 kPa to 60–70 kPa at 5 cm from the drainage boundary. This attenuation, which was intensified by increasing propagation distance and groundwater presence, reduced the consolidation pressure on the soil and led to a lower degree of consolidation. Both lower vacuum pump power and longer vacuum pipes delayed the initial VP reading by 39–48 h and increased the VP monitoring error to around 30–40 kPa. Using PP provided a more accurate representation of soil consolidation in practical applications.