Consolidation Effect of Prefabricated Vertical Drains with Different Lengths for Soft Subsoil under Vacuum Preloading

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.

A comprehensive study on the effects of initial water content, suction magnitude, and drainage zone size on self-weight consolidation and vacuum preloading of soft soils and slurried mine tailings

“…It should be noted that in most studies of vacuum preloading, the vertical drains fully penetrate the ground layer (i.e., the vertical drain length and the thickness of the whole layer are equal). Only a few attempts were made to investigate the performance of vacuum preloading with partially penetrated drains, including analytical and numerical studies [73,74] as well as experimental research [75].…”

Consolidation Attributes and Deformation Response of Soft Clay Reinforced with Vertical Scoria Drains under Road Embankment

“…In order to accurately perform a consolidation analysis, a reasonable time step has to be selected. Terefore, the analysis of clay consolidation should allow for a time-stepping procedure that takes into account timebased incremental loading [59]. In a specifc context, the main intention of introducing drains to clay soil is to accomplish the consolidation process within predefned time duration, to attain a required minimum excess pore pressure, or to attain the required degree of consolidation [60,61].…”

“…Tis is due to the fact that higher the length of drain, higher is dissipation rate of excess pore water and so is rate of settlement. In relation to this, Hammad and Lou et al [13,59,68] pointed out that the time it takes for pore water to dissipate and the prolonged settlement decrease as the length of vertical drains grows.…”