VERTICAL DRAINS Prefabricated vertical drains (PVD), also known as wick drains, are used to accelerate the consolidation of impervious soft silts and clays. PVD are supplied in rolls with cross sections that are either rectangular or circular shaped. shaped A non-woven geotextile filter covers the PVD's hard core. The filter allows water to flow into the drain, and the core provides the drain's stiffness and flow path. path The PVD mast that can be in excess of 50 m high is connected to an excavator base or a crane. The wick drain roll is guided to the top of the mast, and into a hollow steel mandrel that is pushed into the ground to refusal or a target depth. depth Before being pushed into int the ground, the PVD is connected to a steel plate that prevents soil from entering the mandrel, mandrel and anchors the wick drain into the ground when the mandrel is withdrawn. A temporary surcharge is commonly used in conjunction with the vertical drains to pre-load load the ground, ground and to reach primary consolidation. tion. PVD spacing and preload fill height depend on the soil properties, load intensity and design specifications. specifications Real time consolidation can be monitored by installing appropriate instruments. Rev2 VERTICAL DRAINS Vertical Drain Installation The illustration shows a PVD mast mounted on an excavator. EADS Airbus A380 Factory 30,000,000 m of PVD were installed for the platform preparation works of EADS Airbus Plant in Hamburg, Germany. The site was reclaimed from the Elbe River, and was to be built on up to 14 m of very soft river mud. 17 rigs working at double shifts were mobilised, and implemented to complete this project. Recent References Perth Waterfront a.k.a. Riverside Stage 2 (Perth, WA Australia) - Broad Construction -Platform preparation - 575,000 lm Alcoa RSA1 (Pinjarra, WA Australia) - Leighton Contractors - Residual storage area - 500,000 lm Fisherman’s Island J2S2 (QLD, Australia) - Port of Brisbane Corporation Fisherman’s Island S3A & S3B (QLD, Australia) - Port of Brisbane Corporation Otway Gas Project (VIC, Australia) Port Saeed Power Plant (Egypt) - 3EC - Platform and buildings - 1,600,000 lm Pearl of the Gulf (Qatar) - Qatar - Platform and villas -700,000 lm GFWA Web: www.gfwa.com.au GFWA Perth Sydney MENARD BACHY Brisbane Melbourne MARCH Christchurch 113 Radium Street Welshpool WA 6106 Tel: +61 8 9350 5394 Fax: +61 8 9358 3095 13-15 Lyonpark Road Macquarie Park NSW 2113 Tel: +61 2 9491 7100 Fax: +61 2 9491 7111 6 Chapman Place Eagle Farm QLD 4009 Tel: +61 7 3354 9100 Fax: +61 7 3354 9111 217 Arden Street North Melbourne VIC 3051 Tel: +61 3 9321 1333 Fax: +61 3 9326 8996 1220 Main North Rd Belfast 8083 New Zealand Tel: +64 3 323 8085 Fax: +64 3 323 7584 Rev2
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