Drainage Systems
A drainage system allows water to egress from behind a piled wall to release hydrostatic pressure and control the flow of ground water to prevent consequential damage and deterioration.
Structural problems such as oxidisation (rusting) of reinforcement mesh and anchors, and issues created by standing water are addressed by the installation, at construction phase, of drainage systems and waterproof membrane barriers, combined with concrete waterproofing additives mixed within the matrix of the concrete materials.
Geotextile drainage systems
Proprietary geotextile drainage is frequently used within the cusp of the pile to control ground water egress. Perforated pipe (up to 100mm dia) is fied into the cusp of the pile at predetermined centres, according to design, but typically every pile gap (frequency dependant on ground water conditions) and fixed with resin anchored L bars or IDMR fixings and/or light weight mesh. This becomes a permanent fixture following infill and overlay with sprayed concrete.
Cavidrain or Pile drain systems
Pile-drain is a geo-composite drain comprising of an impermeable single cuspated HDPE core with a non-woven geo-texile wrap across the cuspated face and bonded to the edges of the core. This system is typically specified when spraying a concrete overlay to larger diameter piles, together with wider pile gaps (over 100mm).
No-fines drainage systems
Typically utilised in areas where there is an increased risk posed by water egress due to high ground water, or geology that allows excessive flows that would potentially overwheal proprietary geotextile drainage systems. Expanded metal reinforcement is used to contain no-fines aggregates (such as pea gravel) or other porous materials which allow fast drainage of water and prevents the buid up of hydrostatic pressure.
