Analysis of the Effectiveness of the Step Vacuum Preloading Method: A Case Study on High Clay Content Dredger Fill in Tianjin, China

Abstract

As a solution to avoid the blockage of the drainage pipe by traditional vacuum preloading, step vacuum preloading (SVP) has been progressively studied. However, the effectiveness of this technique has yet to be systematically analyzed. In this study, an indoor model test was conducted in which vacuum pressure was applied in five stages (10, 20, 40, 60, and 80 kPa) to dredger soil with high clay content at a reclamation site in Binhai New Area, Tianjin, China. The extent of the consolidation effect of the soil was determined, and the effectiveness of the step vacuum preloading method to address drainage pipe blockage was evaluated. The results indicate that soil settlement increases at each stage of vacuum pressure treatment and the degree of vertical consolidation at each stage exceeds 90%. At the end of the treatment stage with vacuum pressure of 80 kPa, the weakly bound water was discharged. Dissipation of pore water pressure occurred in all stages. On the basis of these results, it is shown that SVP can efficiently reinforce dredger fill. Moreover, after SVP, the grain size of the soil and void ratio are still uniformly distributed. Regardless of their location from the drainage pipe, soil exhibits permeability coefficients within the same order of magnitude. The consolidation effect of soil in each stage and the increased drainage rate in the initial stage of vacuum preloading with 80 kPa indicate that the test in the current study can decrease the horizontal displacement of fine particles and can avoid drainage pipe blockage.

Study on the Interaction between the Reduction and Remediation of Dredged Sediments from Tai Lake Based on Vacuum Electro-Osmosis

“…T3 : I = 0.277 e (−0.068t) + 0.050 (10) T4 : I = 0.211 e (−0.072t) + 0.037 (11) T6 : I = 0.265 e (−0.039t) + 0.083…”

“…The advantage of this method is the simple construction technology and low cost [7][8][9]. However, as a traditional mechanical dehydration method, the vacuum preloading method has a long construction period, and the treatment effect is difficult to meet the requirements [10]. Additionally, the electro-osmosis method can be used to reduce the volume of dredged sediment, and has a better edge in dealing with this kind of fine-grained clay.…”

Recent Developments in the Vacuum Preloading Technique in China

“…When using the conventional vacuum preloading technique to consolidate the newly pumped dredged clay, there is often a reduction in drainage capacity due to the clogging of the filter sleeves of PVDs. A multiple-step vacuum applied method has been investigated in recent years through laboratory model tests [25][26][27] and field cases [28,29]. The vacuum pressure could be applied in two-step of 40 and 80 kPa, in three-step of 20, 40, and 80 kPa, and even in five-step of 10, 20, 40, 60, and 80 kPa [29].…”

Analysis of Factors Affecting Vacuum Formation and Drainage in the Siphon-Vacuum Drainage Method for Marine Reclamation

“…Marine dredged soil, commonly utilized in reclamation, has characteristics including high compressibility, high water content, low bearing capacity, and low permeability [2][3][4]. The drainage consolidation method is economical and efficient, making it a prevalent choice for large-scale marine reclamation [5][6][7][8]. Techniques such as surcharge preloading, vacuum preloading, and electroosmosis are often employed for drainage [9][10][11].…”