'innovators
by nature'
"Using in-house developed equipment, VLTT conducts shield drilling with diameters from 400 mm to 3000 mm. We do so using various drill pipe materials, such as steel, concrete, glazed stoneware, glassfibre reinforced and polymer concrete. This technique is also referred to as closed front (CFT) or microtunnelling."
CLOSED FRONT DRILLING (CFT)
What are the advantages of closed front drilling?
A great advantage of shield drilling is that it can be carried out ‘in wet works’, without requiring water recession in the trajectory to be drilled.
What are the advantages of closed front drilling?
- Can be executed ‘in wet works’
- Longer drilling trajectories possible versus open front technique
- No groundwater recession necessary in the drilling trajectory
- Intermediate stations allow large lengths of trajectory to be installed at once
How does it work?
A pipe element is driven out of a delivery funnel into the soil. Once a pipe element has been driven into place, the jacks are withdrawn and a new element can be attached and driven. Should the friction resistance on the pipeline become excessive, resulting in exceeding the driving capacity, intermediate stations can be installed between the pipe elements. Bentonite is injected around the outside of the pipeline during drilling, in order to reduce the friction resistance between the pipe element and the soil. The position of the drill head is continuously monitored using a laser positioning system.