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Pipe Jacking Open Front Technique (OFT)
When to choose Pipe Jacking?
Auger Method
Using this technique a pipe, fitted with a cutting edge or cutting head is pressed trough, crossing any obstacle. An inner tube fitted with an Auger transports the incoming soil back to the pipe’s starting point. We apply this method to laying pipe diameters from 200 mm to 1600 mm.
a. Pilot Guided Auger Boring (GAB)
The first step when performing a Guided Auger Boring is drilling a so called ‘straight pilot boring’. This allows us to define the exact trajectory for the placement of the final jacking tube. We use the Guided Auger Boring method to place tubes ranging in diameter from 200 mm to 1600 mm with greater precision.
When drilling the pilot rod we use a modified theodolite and a led probe to monitor direction and depth. Then we connect the jacket tube’s cutting head to the pilot rod. As it is driven into the ground the pipe will now follow the path of the pilot rod which will be removed in sections at the receiving end. An Auger transports the incoming soil back to the starting point. As a result of this method the jacking tube is now placed in the exact trajectory of the pilot rod.
What are the advantages?
- Cutting head on the front of the pipe element prevents the drill front from eroding.
How does it work?
Manual excavation is a precise and safe microtunneling technique. Pipe elements are driven into the ground, while the incoming material is manually shovelled into a chute. A tube running back to the operating shaft transports the soil by use of an auger or conveyor belt. We own several different machines for this specialisation which allows us to install pipes up to 3000 mm in diameter. Due to manual labour inside the pipes the minimally required diameter is set to 1200 mm.
Because of the accessibility of the drill front, the pressing direction can be accurately controlled. The front tube element is fitted with a cutting head to prevent calving at the drill front and also reduces pressure on the jacking tube. This method can also be applied for the installation of rectangular profiles.
Pipe Jacking
Pipe Ramming (OFT-R)
When to choose Pipe Ramming?
Pneumatic press through is often used for a press through under a road and therefor has the advantage that it causes a minimum impact to the environment. Another advantage is that it is cheap in comparison to hydraulic pressing. Only a straight drilling route can be used. The diameter depending on the method used is limited. VLTT offers this technique for pressing through steel pipes in diameters ranging from 114 mm to 1220 mm (4” – 48”). Drilling and pressing through is possible in lengths of 25 m – 80 m. This technique is harder to control and has limited accuracy and is therefore quite sensitive to deviations.
What are the advantages?
- Minimal impact or disturbance to the surrounding areas
- Cheaper in comparison to hydraulic pressing
How does it work?
The bottom press rocket can drive the pipeline into the ground or pull behind it. The missile consists of a steel cylinder shaped like a torpedo in which a pneumatically movable piston fits. The piston strikes an anvil in the front of the cylinder with force. Due to the thrust of the piston against the cylinder, the rocket shoots forward a bit. The piston is then moved backwards and the process repeats. During the backward movement of the piston, the rocket remains in place due to the friction between the ground and the cylinder.