Wick drains employed on malton by-pass : Beyer, M G; Falconer, J S Ground Engng, V11, N1, Jan 1978, P16–18

Abstract

The purpose of this new type of vertical drainage system is to accelerate the process of consolidation of soft alluvial deposits under embankment loading. An economical method of accelerating the consolidation process is achieved by shortening the distance between the drainage paths by means of highly permeable vertical drains inserted into the ground. The wick drain is a high quality special non-woven polyester fabric which is resistant to all acids and basic chemicals in soils, to bacteria, frost, and UV radiation. Its pore volume in excess of 80% accounts for the drain's high water transmissibility. The wick drain is 300 mm wide and 4 mm thick and is supplied in roles of up to 300 m in length. The route of the bypass crosses a flood plain before rejoining the original truck road. Problems were anticipated with settlement and stability of the embankments. Because of potential flooding, the embankment was formed above the flooding level with rock fill arising from the cutting. To reduce the drainage path within the aluvium and accelerate the consolidation settlement and increase shear strength, vertical drains were installed to an average depth of 5 m below ground level. A specially designed tubular steel lance was vibrated into the ground through which the wick drain was passed through and into the ground. The drain was then cut off approximately 0.5 m above ground level. Instrumentation was provided to monitor the construction of the embankments as well as both the drained and undrained areas of the special embankment.