An evaluation of vacuum pressure effects in ground improvement using prefabricated vertical drain (PVD) = Đánh giá vai trò của áp lực chân không trong gia cố nền đất bằng bấc thấm

Abstract

This study critically assesses the role of vacuum pressure in enhancing the consolidation of soft soils treated with prefabricated vertical drains (PVDs) and surcharge loading. Three distinct approaches were employed: analytical modeling, finite element analysis using PLAXIS 2D, and validation against real-world field monitoring data. The results indicate that increasing the vacuum pressure from 70 kPa to 90 kPa leads to a settlement increase of up to 10.5%. The most significant acceleration in consolidation was observed within the first 90 days. The relationship between vacuum intensity and settlement was found to be nonlinear, yet stable. In the initial phase (0–30 days), the finite element model (FEM) overestimated settlement by approximately 47%. This discrepancy is primarily attributed to idealized assumptions of uniform vacuum distribution, which deviate from the actual in-situ vacuum pressure losses that occur with depth. However, this deviation decreased significantly over time. By day 180, the difference between the FEM results and field measurements was reduced to 5.6%, which is within an acceptable engineering margin. Although the field improvement achieved a high degree of consolidation (exceeding 90%), the process was not fully optimized, particularly during the early stages of vacuum application. Furthermore, the model did not account for staged embankment construction or variable vacuum schedules, both of which can significantly influence consolidation behavior. These findings highlight the need for more refined modeling techniques and advanced control strategies to maximize the performance of vacuum-assisted ground improvement systems.