WICK DRAIN GUIDE SPECIFICATION (METHOD)

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The Deep Foundations Institute’s 2014 guide provides a method specification for installing prefabricated vertical (wick) drains. These geocomposite strips, made of a polymer drainage core wrapped in geotextile, shorten the path for water to escape from soft, compressible soils. Used often with preload or surcharge, they accelerate consolidation and strength gain, reduce waiting time between embankment lifts, and help settlement occur before a structure enters service.<br /><br />The specification sets minimum contractor experience and requires submittals at least 30 days before work, including project references, drain samples and material data, equipment and mandrel details, anchorage, and proposed installation methods. Drains must meet stated flow-capacity and geotextile/core strength requirements; materials must be protected, labeled for quality control, and produced under independently monitored quality controls.<br /><br />Installation equipment must minimize soil disturbance. Drains are advanced in a protective mandrel using constant load or rate, anchored at the required depth, and installed without impact hammers or jetting. Vibration is allowed only in stiff upper soils. Work requires a stable platform and drainage layer, careful utility checks, marked locations, and control of alignment and depth. The guide also addresses splicing, obstruction clearance, rejected or abandoned drains, and the required length protruding above the working surface.<br /><br />Payment is based on mobilization, satisfactorily installed or authorized abandoned drain length, and obstruction-clearance length, with specified work and incidental costs included in the relevant bid prices.<br /><br />The document is a guide, not a universal prescription: the Engineer should adapt requirements to project conditions, and the guidance should be applied using competent engineering judgment.

Keywords

prefabricated vertical drains

wick drains

consolidation

preload surcharge

soft compressible soils

geotextile

polymer drainage core

installation specification

quality control

deep foundations