Vertical drainage


  • Vertical drainage

    Prefabricated vertical drains, also known as wick drains, are one of the most commonly used techniques to make soft compressible subsoil with a low bearing capacity constructible. Vertical drainage together with a surcharge reduces the time of settlement substantially. Area’s that are sensitive to settlement are characterized by a high water content as well as an open structure between the grains. When loads are placed, excess pore pressures are formed because of the low permeability of the soil layers. Without taking measures, this excess pore water will flow out very slowly. This leads to a long period with high settlements and possible stability problems when loads are being placed too soon. Cofra’s vertical  drainage system consists of a synthetic prefabricated vertical drains that are being installed vertically from the surface level up to the bottom of the weak layer. This creates vertical drainage paths in the subsoil that shorten the drainage path of the excess pore water considerably. Vertical drainage results in a reduction of the consolidation process from tens of years to half a year or even less. It will also increase the stability which makes it possible to place embankments faster.

  • Vertical drainage


Installation of vertical drainage

Since the development of the prefabricated vertical drain, Cofra has been one of the largests and most advanced contractor in the world. The experience, gained in the Netherlands as well as in other countries around the world, has made it possible to make a sound estimation of which equipment is most suitable for the execution of a specific project. This is done with the support of our geotechnical department, and an extensive database of previously completed projects. Cofra has a solution for every size, depth and difficulty of a vertical drainage project. With the use of several excavator sizes, ranging from small (CAT 330) to very large (larger than CAT 385), and stitcher types available, various projects can be executed ranging from small in very soft soils, to large in difficult soil requiring equipment for deep or difficult installation. Even for working “off shore” Cofra has the necessary experience and equipment. Furthermore, Cofra has at its immediate disposal, drilling equipment for extreme hard layers encountered during installation (CPT values above 25-30 Mpa over thick sections), specialized equipment constructed to work near or below high voltage power lines and well-equipped workshops for long and large projects.
The prefabricated vertical drains are installed using a wide range of exclusively built patented stitchers, developed in-house by Cofra. The principal of installation of the vertical drainage is based on the insertion of a steel mandrel with a drain inside. This mandrel is moved up and down through a system of cylinders and winches, which in turn are propelled by the excavators’ hydraulic system. The drain extension at the bottom of the mandrel is connected to an anchor plate which closes off the opening so no soil can enter. The mandrel then takes the drain to the desired depth. When the mandrel is at this depth, it is withdrawn and the resistance created by the anchor plate upon retraction ensures that the drain remains in place at the right depth. After the mandrel has reached the surface, the drain is cut and a new anchor plate is connected to the bottom of the next drain.
Vertical drainage installation
During the vertical drainage installation period, a wide range of parameters can be registered. These guarantee a high quality standard and a proven end product. Through specially developed computer programmes; depth, time, penetration force, speed, position and straightness can be recorded. Subject to the wishes of the customer these results can be reported after installation. Furthermore, machines are always operated by qualified operators with extensive experience, supported by a professional technical service team.

Even if Cofra has not previously encountered a specific problem, a solution will be guaranteed, using the company’s innovative qualities. This is, of course, done in close cooperation with the customer.


The application areas for vertical drainage are:

  • Soil improvement of residential or construction areas
  • The construction of infrastructure (roads, railways, harbours, airports)
  • Construction of dykes
  • Land reclamation projects


The advantages of applying vertical drainage are:

  • The slight disturbance of the different soil layers
  • Guaranteed water drainage, even at high soil pressures and settlements
  • The possible adjustment of the core and filter to the local soil conditions
  • Shortening the consolidation period by applying a close drain distance
  • Rapid installation: on average 8000m per day, per machine
  • No water required for installation
  • Installation to a maximum depth of 65m
  • Monitoring of installation with a data logger, if required equiped with GPS
  • Clean execution without releasing soil

If you have any questions about the installation of vertical drainage or if you need advice concerning a necessary ground improvement, you can always contact us.
In addition, more information is available under the other tabs.

Note that vertical drains are also called: wick drains, band drain, MebraDrains, prefabricated vertical drains(PVD).


Reference vertical drainage projects Length(m) Project report Video
Makarov Embankment St. Petersburg, Russia 280.000
Knooppunt Joure A6-A7, The Netherlands 13.227
De Brinkhorst Moordrecht, Netherlands 395.000
Thiendenland II en Zevender fase 3 Schoonhoven, Netherlands 140.000
Voorbelasting Kreekrijk Assendelft, Netherlands 10.200
Voorbelasting Kleyweg Den Hoorn, Netherlands 21.000
Collecteur du Trichon Roubaix, France 7.700
N236 reconstructie en Vechtbrug Weesp, Netherlands 26.000
Weespertrekvaart fase 3 Amsterdam, Netherlands 10.000
Houthavens Kistdam Amsterdam,Netherlands 19.880
Lindeweyde Linschoten, Netherlands 20.600
Groene Oever Amsterdam, Netherlands 260.000
N305 Waterlandseweg Almere, Netherlands 39.000
Oktyabrsky Island 2nd stage, 1st phase Kaliningrad, Russia 1.300.000
Westrandplan 4-5 Wervershoof, Netherlands 55.386
Centrale As noord, Dokkum, Netherlands 88.105
BRM Haastrecht Haastrecht, Netherlands 78.000
Herinrichting N241 Schagen, Netherlands 336.872
Versertraverse Beverwijk, Netherlands 65.480
Containeropslag Pernis Rotterdam, Netherlands 97.424
BRM 380kV Station Breukelen, Netherlands 21.000
BRM bouw Zwembad Kampen, Netherlands 31.500
Weespertrekvaart Amsterdam, Netherlands 216.129
Winkelcentrum Hoog Dalem Gorinchem, Netherlands 68.320
Hoeksewaard Spui Oost Goudsewaard, Netherlands 450.000
A4 Middendelfland Schiedam, Netherlands 100.000
Oude Tol 3 fase 2 Reeuwijk, Netherlands 75.000
Voorbelasten Paardekooper Den Hoorn, Netherlands 352.120
Hoekselijn goederenoverdrachtspoor Schiedam, Netherlands 72.950
Dijkversterking Hoeksewaard zuid Strijen, Netherlands 126.000
IJsseldelta Kampen, Netherlands 1.000.000
Voorbelasten Noordvork Aalsmeer, Netherlands 2.500
Proefterp Eemdijk Bunschoten, Netherlands 2.079
Weespertrekvaart fase 2 Amsterdam, Netherlands 90.080
Verzorgingsplaats Ruwiel Breukelen, Netherlands 85.750
Greenport Horti Campus fase 1 Naaldwijk, Netherlands 247.050
Vrijebanselaan A13 Rijswijk, Netherlands 19.248
Beverwijk BOR spoorlijn Beverwijk, Netherlands 24.831
Het Klooster Nieuwegein, Netherlands 48.500
PSA Terminal, Panama 1.400.000 Project report
FOT Container terminal Onne port, Nigeria 1.400.000
Krestovski Island, Russia 1.200.000
RD1032 Ribécourt – Noyon, France 60.000
Echangeur d’Hellange, Luxemburg 29.000 Project report Video
Offshore drains Oslo, Norway 235.000
New Istanbul Airport Project, Turkey 575.000
Interikea Commercial Centre Stage 2, France 21.300
LGV Nîmes – Montpellier, France 250.000
Contournement RN88, France 2.400
Suppression du PN68, France 13.000
Word Cup 2018 Football Soccer Stadium, Russia 517.000
Breakwater Cowes offshore drains, Great Brittain 206.000 Video
Interikea Commercial Centre, France 390.000
Liaison RD1032, France 20.000
Sir Solomon Hochoy Highway, Trinidad & Tobago 260.000
Harmelen, Netherlands 325.000 Video
Deurganckdoksluis, Belgium 16.000
B207 Lübeck, Germany 50.000
Taparura Sfax, Tunesia 18.000
Ostrow Brdowski island, Poland 185.000
New IKEA store Bayonne 940.000
LGV SEA Lot 3 Tours, France 140.000
Lailesse , France 48.000
Semsamar Point-à-Pitre, Guadeloupe 31.000
Leroyerlin Epagny, France 50.000
Port of Balboa, Panama 300.000 Project report
LGV BPL Leans, France 25.000
Mombasa, Kenya 500.000 Project report
RD642 Hazebrouck, France 79.000
ZAC de l’Echange Besançon, France 22.000
Vieux Port de Saint Raphaël, France 19.000
Simpson Bay Causeway, Sint Maarten 35.000
Jadeweser Port Wilhelmshaven, Germany 27.000
A7ons, Belgium 70.000
London Gate access road, United kingdom 230.000
N207 rijbaanverdubbeling Hillegom, Netherlands 616.180
Déviation RD475 Pesmes, France 25.000
Insteekhaven Hendrik Ido Ambacht, Netherlands 6.450
A10/A1 Amsterdam Oost, The Netherlands 531.270
Gezondheidsplein Hengelo, The Netherlands 56.000
Voorbelasting Bentwoudpark ,The Netherlands 36.450
Commerciale La Francheville Charleville, France 60.000
Bedrijfspark Heron Pijnacker, Netherlands 166.280
Klimaatbuffer Albrandswaard Rhoon,Netherlands 114.223
Veilingvaart Roelofarendsveen, Netherlands 30.450
Terminal Felixtowe, United Kingdom 750.000
Voorbelasting 1B Kaag & Braasem, Netherlands 79.800
Oostelijke rondweg Boskoop, The Netherlands 61.250
Sluiseiland Gouda, The Netherlands 50.000
Inrichting Sluiseiland Gouda, Netherlands 58.900
MET terrein Europoort Rotterdam, Netherlands 19.000
Offshore drains Beirut, Lebanon 122.000 Project report
N242/N241 Heerhugowaard, Netherlands 20.000
BRM Trambaan Broek in Waterland, Netherlands 25.000
Bermweg Capelle a/d Ijssel, Netherlands 22.500
Merellaan Capelle a/d Ijssel, Netherlands 11.000
B212 Berne, Germany 28.000
Dijkversterking Bergambacht, Netherlands 36.500
Verlegde Dreef Waddinxveen, Netherlands 11.000
N201-A9 Fokkerweg Amstelveen, Netherlands 54.600
Auto Estrada do Norte Lissabon, Portugal 1.300.000
Gouwepark fase 5oordrecht, Netherlands 25.000
N201 fase 2 Zijdelweg, Netherlands 67.500
Offshore drains Oslo, Norway 180.000
Liegeplatz 9 Fase II Cuxhaven, Germany 226.000
BRM Bollocatie Schoonhoven, Netherlands 13.200
Coenecoop III Waddinxveen, Netherlands 34.500
OOIJ trajectdeel 3 Amsterdam, Netherlands 64.600
Chambéry, France 5.000
Bassin de rétention de EP Parijs, France 800
Fortweg Houten, Netherlands 25.000
Abcoude, Netherlands 610.000
Schortens B210, Germany 770.000
Maison duondearseille, France 212.000
Malaga luchthaven fase 2 en 3, Spain 90.000 Project report Video
IC Terminal Singapore 1.195.000
Orts Umgehung Bauen II Hamburg, Germany 700.000
Taraguilla, San Roque fase 2, Spain 70.000
Barcelona, Spain 900.000
Cruise Ship Terminal Falmouth, Jamaica 45.750 Project report
Tramoyes A432 Ring Lyon, France 150.000
Londonderry A2, United Kingdom 300.000
Westrandweg, Netherlands 1.300.000
Coentunnel, Netherlands 999.500
Beharovce, Slovakia 55.200
Malaga luchthaven fase 2, Spain 50.000
Hulin R55 Praag, Czech Republic 42.000
Roelofarendsveen, Netherlands 80.000
Brass LNG plant, Nigeria 900.000 Project report Video
Bonny LNG Plant, Nigeria 90.000 Video
Malaga Airport, Spain 3.500.000
Soyo, Angola 2.100.000 Project report
Kingston, Jamaica 2.700.000
Bremerhaven Kaiserscheuse, Germany 225.000
Lot A1 A2 Auxonne, France 252.000
A75 Déviation de Valros, France 73.000
Harbour Waalhaven Rotterdam, Netherlands 175.000
Development Industrial Pijnacker, Netherlands 450.000
GTM / OPA2, France 158.000
Container Terminal Suriname 650.000
Land reclamation Shell ECC Project, Singapore 1.000.000
Drains Tunesia ETEP 300.000
Drains Zagreb, Croatia 240.000
Carlisle, Scotland 120.000
Persant Snoepweg Leiderdorp, The Netherlands 159.500
Kiel, Germany 171.800
Newport, Wales 750.000
Rabenov & Kojetin, Czech Republic 26.000
Kolubarsk Belgrado, Servia 600.000
Drains A2 Holendrecht, Netherlands 2.000.000
Hardinxveld Giessendam West III, Netherlands 713.000
Drains Bremerhaven, Germany 65.000
Brake, Germany 140.000
Tuas view, Singapore 1.000.000
Lansingerland Bergschenhoek, Netherlands 645.000
MCRZ Rotterdam, Netherlands 214.000
Land reclamation Brisbane, Australia 750.000
Container teminal Trinity, Great Brittain 1.000.000
Highway embankment A2, The Netherlands 1.500.000
Highway embankment A26 phase 2, Germany 1.800.000
Housing area Steigereiland IJburg, Netherlands 320.000
Railway Sloelijn, Netherlands 420.000
Highway embankment, Slovakia 1.615.000
N470, Netherlands 500.000
Waterwork Oslo Sjuroya, Norway 80.000
Keizershof Pijnacker, Netherlands 900.000
Harbour Area St. Nazaire, France 380.000
Felixtowe, Great Brittain 1.300.000
Motorway D47-4704 Belotin, Czech Republic 385.000
Finkenwerder Knoten, Germany 325.000
Singori Nuclear Power Station, South Korea 695.000
Autoroute Tanger-Port de Qued, Morocco 1.000.000
Autoroute Teteon-Friqed,orocco 1.200.000
Railwayurcia Ete, Spain 1.300.000
Sewerage plant Conakry, Guinee 100.000
Container Terminal Felixtow, Great Brittain 300.000
IJburg Amsterdam, Netherlands 4.000.000 Project report
Changi Airport, Singapore 48.000.000 Project report



Design information Vertical Drains

The required drain distance and installation depth of vertical drains are dependent on the project and are determined using design calculations. The drain distance is highly dependent on the available time for the consolidation process and on the requirements with regards to the residual settlements after the construction period. The depth of installation is in its turn dependent on the local geology and geohydrological conditions.

There are, next to simple formulas for a 1-layer system, several calculation methods available for the design of vertical drains, like the Dutch Koppejan method and several isotach methods. These methods are programmed into commercial software to make calculations easier. A well known software package in Holland is Msettle (Delftgeosystems) , able to calculate, next to a drain distance, the settlements and residual settlement also the application of BeauDrain.

Cofra uses, next to Msettle, an internally developed program based on the isotach theory. Cofra is able to provide you with the complete design package for small and large projects, by using the expertise of Hydronamic, the engineering firm of Boskalis Westminster, with over 10 geotechnical engineers. Two of them are resident engineers based in Amsterdam. Next to design work, second opinions can be given on completed designs.

The calculations, using the internally developed calculation program, are performed for a multi layered 1 dimensional profile using the isotach theory of Yin and Graham 1989 with Terzaghi consolidation. The drains are modeled using the derivation of Barron-Carillo. It is possible to model, within the calculation model, a staged construction with and without vertical drains and calculate the settlement, residual settlement and degree of consolidation in time.

In the case you would like us to perform a design, the following information is required:


  • existing surface level
  • future surface level
  • waterlevel
  • sketch indicating the area and location where the ground improvement is required

Geotechnical data

  • soil profiles ( boreholes, SPT data, CPT data)
  • Geotechnical parameters (unit weights, compressibility characteristics of the soil

Operational figures

  • maximum extend of the consolidation period
  • wishes with regards to surcharge levels or drain distances


  • settlement, residual settlement or minimal degree of consolidation demands

In the case you have only a limited amount of data available for the design, you can always contact our geotechnical department in order to see if we can perform a design using the available data, or whether there is a need for additional site investigation.

Specifications MebraDrain

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