Microtunneling Closed Front Technique (CFT)
When to choose Microtunneling?
Using our own microtunneling equipment VLTT installs pipes ranging from 400mm up to 3000mm in diameter. All known pipe types such as steel, concrete, fibreglass reinforced, and polymer can be used. Other materials are also possible, for example plastic pipes to ensure a safe disposal of liquid waste from laboratories.
A major advantage of working with a microtunneling machine is that it can be carried out ‘in the wet’, meaning without having to disrupt natural groundwater levels in the drilling area. If dewatering of the start and ending shafts is not an option, a sheet pile construction in combination with an underwater concrete floor provides an ideal solution.
What are the advantages?
- Can be carried out ‘in the wet’
- Possibility to drill longer stretches compared to open front technique
- Lowering groundwater levels is not necessary in route to be drilled
- By applying intermediate stations, long lengths of track can be laid at once
How does it work?
A tube element is pressed into the ground from the press tub. When a pipe element is pushed out, the jacks are retracted and a new element can be installed and pushed away. If the frictional resistance on the pipe is to heavy, causing the pressing capacity to be exceeded, intermediate stations are installed between the pipe elements. To reduce the frictional resistance between the pipe element and the ground, bentonite is injected along the outer circumference of the pipe during the drilling process. The position of the drill head is continuously monitored by a positioning laser-guided system.