Reinforcement effectiveness of stacked prefabricated vertical drain (S-PVD) vacuum preloading method: A case study

To address the issue of vacuum pressure attenuation in traditional vacuum preloading ground reinforcement methods, this study proposes a stacked prefabricated vertical drain (S-PVD) vacuum preloading method based on the stratified sealing drainage technology. A comprehensive field test was conducted to comparatively analyze the reinforcement effectiveness of three vacuum preloading approaches: conventional prefabricated vertical drains (PVDs), reverse prefabricated vertical drains (R-PVDs), and the novel S-PVDs. Test results demonstrate that the S-PVD method not only significantly enhances the ground reinforcement effect, effectively increasing surface settlement and vane shear strength of the soil, but also improves the uniformity of the reinforced soil, with only a 4.6 % difference in the vane shear strength between the top and bottom of the drainage board. In addition, the S-PVD method can meet the unloading criteria in less than 30 days, reducing the consolidation period by 34.1 %. The optimized S-PVD system demonstrates notable cost-effectiveness through energy-efficient operation and accelerated consolidation, achieving 26.5 % reduction in unit area cost of materials and electricity compared to conventional vacuum preloading. These findings suggest that the S-PVD method represents a promising innovation in deep soil stabilization technology, offering a technically and economically viable solution for soft ground improvement in coastal regions.