Theoretical and field investigation into the vacuum formation in the siphon-vacuum drainage system for soft ground improvement

Compared to the traditional drainage consolidation measures for soft ground improvement, the siphon-vacuum drainage method (SVD) offers more advantages, e.g., improved drainage efficiency, lower maintenance costs, lower demand for energy and materials, and less environmental impact. Hence, it is expected to be widely applied in soft ground improvement. However, the mechanism of vacuum formation in the system remains unclear. In this work, the vacuum formation mechanism of SVD is investigated based on the theoretical deduction of the variations of the water level and air pressures during the siphon drainage and seepage processes. A theoretical model is developed to describe the vacuum formation, allowing the estimation of the varying air pressure, water level, seepage rate, and discharge rate in the system. Moreover, a field investigation was carried out in Zhoushan, Zhejiang Province, to further validate the correctness of the developed model. This work also provides further insights and suggestions into the field application of SVD for soft ground improvement.