Cofra is an experienced installer of mixed in trench walls using our own trencher. Over the years we have executed projects in Europe and Africa, often in combination with our Geolock product using this special trencher. Our specialists are happy to inform and assist you, in pre-tender as well as during your project phase.

What it is

Our trenched techniques consist of application in which our trencher is used. The following application areas are suitable for the use of our trench:

  • Installation of a sand wall with or without an horizontal drain up to a depth of 8m below the surface
  • Installation of an horizontal drain into a mixed soil up to a depth of 12m below the surface
  • Pulling in a horizontal liner up to adepth of 5m below the surface
  • Creation of a mixed in trench wall for the installation of our Geolock product up to a depth of 12m
  • Creating of mixed in place wall consisting of bentonite, cement bentonite, soil-bentonite, soil-cement-bentonite or any other slurry up to a depth of 12m
  • Mixing or placement of ZVI, Zeolite, Active Carbon, Mulch and any other reactive materials on contaminated sites up to a depth of 8 to 12m depending on the need to mix or have a clean insertion of material. 

How it works

All applications are installed using the trencher. The chain is lowered into the soil from a horizontal position into a vertical position. With the direction of the chain material is removed from the trench or remains largely in place. Special attachments are used for the different applications which are pulled through the soil after the chain of the trencher.

Why it's used

The system is used for various reasons.

  • When a (liner) wall is created by mixing material into the soil, the main purpose is to block (potentially polluted) groundwater flow at for instance waste disposal-, factory- and mining sites. In civil applications the system is used to block waterflow through dikes, dams and polder constructions.
  • When reactive material are placed, the purpose of the wall is to neutralize the contamination by inserting the reactive material. 
  • When a horizontal drain is installed or a sand wall is installed the main purpose is to drain water from the ground or replace part of the soil with a stronger material to increase the strength parameters of the material.  


Application area

Our trencher is used in the following markets:

Infrastructure: In Infrastructure the trencher is used to create sandwalls to consolidate compressible material or to creat impermeable mixed in trench walls to be able to lower the waterlevel.

Dredging and land reclamations: Mixed in trench wall can be used to lower the water table and accelerate consolidation.

Mining: Mixed in trench walls or liner walls can be used to block contaminated waterflow. The insertion of reactive material can be used to neutralize contaminated water 

Pollution management: The mixed in trench walls can be installed around landfill sites to prevent any leakage of pollutants.The insertion of reactive material can be used to neutralize contaminated water 

Flood protection: In the flood protection market the mixed in trench can be used to block waterflow in sandy layers and prevent the buildup of pressures in the polders behind the levees and dikes.

How it is installed

The application areas are all based on the use of the trencher with or without an attachment behind the chain. At the start of the installation the chain is positioned on the edge of the trench in a horizontal position. It is cut into the soil like a knife until the chain is in a vertical position. Once in this position, the installation of the application starts. With the direction of the chain, running forwards or backwards, the amount of soil left in the trench, can be controlled. Depending on the cassette behind the chain and purpose, the trench is empties or a slurry is mixed with the soil. In the image below the mixed in trench method is given as an example.




Contact us (regional contacts on our contact page)

A selection of our barrier projects

Back to top