Abstract
The application of vacuum preloading to prefabricated vertical drains (PVDs) with different lengths is widely used in practical engineering to investigate their consolidation at the same depths of even and multilayer subsoils from the seabed. In a laboratory, model experiment was conducted using even subsoil and embedded PVDs with lengths of 0.6 and 1.2 m. The obtained results showed that in the even subsoil, the 1.2 m PVDs maintained a higher vacuum pressure in the shallow layer and demonstrated better consolidation behavior as compared to those of the 0.6 m PVDs. In the upper subsoil layer, the average vane shear strengths of these two systems increased to 18.2 and 22.6 kPa, respectively. The degree of consolidation of the upper subsoil layers in the two model experiments calculated from the pore water pressures under boundary drainage conditions were 51% and 68%, respectively. For practical verification purposes, similar experiments were conducted for multilayer subsoil by inserting PVDs with lengths of 6 and 15 m into different test sites. As a result, the vane shear strengths of the upper 6 m subsoil layers increased to 26.3 and 33 kPa, while the degree of consolidation were 72.1% and 80.9%, respectively, although some irregularities were observed at different depths.
Highlights
E application of vacuum preloading to prefabricated vertical drains (PVDs) with different lengths is widely used in practical engineering to investigate their consolidation at the same depths of even and multilayer subsoils from the seabed
Testing was performed as follows: (1) e PVD was first fixed on the customized cylindrical iron shelf, the piezometers used for measuring the pore water pressure and PVD blocks used for vacuum pressure in the subsoil were attached at depths of 0.3, 0.6, 0.9, and 1.2 m and radius of 0.15 m from the central PVD. e syringe needles were inserted into the central PVD at a length of 0.6 m and depths of 0.3 and 0.6 m for measuring their internal vacuum pressure
The vacuum pressure decreased, its losses observed for the depth from 0 to 0.6 m in both T1 and T2 amounted to approximately 20 kPa/m, which was consistent with the results obtained by Cai et al [22]. e depth in T1 spanning from 0.6 to 1.2 m exhibited even greater attenuation, indicating that it was impossible to achieve uniformly distributed vacuum pressure along the vertical direction in the improved soil under vacuum preloading [23, 24]. e signi cant di erences between T1 and T2 included the times required to reach measurable vacuum pressure levels within the subsoil and those passed until steady pressures value were attained
Summary
Academic Editor: Sanjay Nimbalkar e application of vacuum preloading to prefabricated vertical drains (PVDs) with different lengths is widely used in practical engineering to investigate their consolidation at the same depths of even and multilayer subsoils from the seabed. E degree of consolidation of the upper subsoil layers in the two model experiments calculated from the pore water pressures under boundary drainage conditions were 51% and 68%, respectively. The vane shear strengths of the upper 6 m subsoil layers increased to 26.3 and 33 kPa, while the degree of consolidation were 72.1% and 80.9%, respectively, some irregularities were observed at different depths. E objective of this study was to conduct a model experiment, in which PVDs with lengths of 0.6 and 1.2 m were embedded in even subsoil and compare the resulting vacuum pressures, pore water pressures, settlements, and other key parameters measured under vacuum preloading. Water contents, vane shear strengths, and degrees of consolidation were determined after stopping the vacuum pump, and the differences between the results of these two model experiments obtained for the upper and lower soil layers were compared.
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