Cofra B.V. products

Since the development of the synthetic prefabricated vertical drain (PVD) also known as wick drain in the late 1970ties, Cofra is worldwide one of the leading contractors. Cofra has installation rigs available for each soil type, varying from very soft soils to very stiff intermediate layers. Installing worldwide, we encounter depths of 3 to over 60 meter! Our heavy installation sets are the strongest in the world and able to penetrate 25 to 30MPa sands. For working offshore, we have the necessary experience and equipment. Our installation rigs are designed for containerized transport and thus easy to ship to any project location in the world.

Since the development of the synthetic prefabricated vertical drain (PVD) in the late 1970ties, Cofra is worldwide one of the leading contractors in this segment. Cofra has installation rigs available for each soil type, varying from very soft soils to very stiff intermediate layers that can be deployed on pontoons. Our installation rigs are designed for containerized transport and thus easy to ship to any project location in the world. Being part of maritime service provider Boskalis gives us a unique access to resources and floating equipment to help execute your project

Cofra has a long track record in the field of vacuum consolidation. We have multiple vacuum consolidation systems within our range of techniques, amongst which Beaudrain, BeauDrain-S and the traditional vacuum consolidation method using a synthetic liner. All concepts, except for the BeauDrain system which uses an in-house developed special plough, are installed by using our own PVD rigs. Every system has its own solution to overcome loss of vacuum in sand layers. Ask us about the possibilities.

Cutoff walls are used for both environmental and civil projects. Cofra has many years experience in the manufacture and installation of Geolock cutoff wall. With Geolock, Cofra has realised projects in Europe, North America and Asia. Geolock is used for the isolation of existing waste disposal sites and the waterproofing of dikes, dams and motorways in cuttings. Geolock has an infinite number of applications and is competitive with traditional materials. Wherever a horizontal underground flow of groundwater, contaminated or otherwise, has to be blocked, Geolock offers the optimal watertight cutoff wall solution.

The Cofra Roller Compaction (CRC) method, also referred to as High Energy Impact Compaction (HEIC), is a technique that densifies loose granular materials up to a depth of 2 to 3 meters below the surface by pulling a non-circular roller over the surface of an area.

Cofra Dynamic Compaction (CDC) method, also referred to as Rapid impact compaction (RIC),  is a technique that densifies loose granular materials up to a depth of 7 to 9 meters below the surface by repeatedly dropping an hydraulically accelerated weight from a height of 1.2 to 1.5m onto a foot which remains in contact with the soil. This provides a highly save and sound operational process when compared to Dynamic Compaction. We have hammer available ranging in drop weights from 9 ton up to 16 ton. 

Vacuum consolidation was first introduced in 1952 by W. Kjellman, the inventor of the pre-fabricated vertical drain. Since then, vacuum consolidation has been in frequent use in constructions with a high risk for instability. The BeauDrain technique was developed at the beginning of this century as an alternative to the traditional vacuum technique.

The function of BeauDrain-S vacuum consolidation is based on the use of an air-tight hose. In this system, vertical drainage is only used in the compressible and sealing layers. The top layers of sand, where there is a risk of air or excess water inflow, are sealed off from the system with the aid of a thyleen hose. As a result, a vacuum can be applied to the drain. The vacuum in the drain translates into an equivalent (fictitious) vertical load at ground level. For each project the subsoil is studied carefully in order to ensure that the system will function as desired. A soft sealing layer of clay or peat must be present just below the surface.

Cofra has started with the application of Geotextile Encased Columns when former Mobius sections, in the past the market leader in the installation of GEC, were acquired by our parent company Boskalis. Due to our strong relationship with Huesker Cofra has become one of their preferred installers to install the GEC columns on every location in the world.

Stone columns are widely used as ground improvement method for unsuitable soils to improve its bearing capacity and limit settlements. Cofra has the capability to install stone columns using special rigs attached to our standard base units. Ask us for the possibilities in applying stone columns for your project.