Pressing techniques

This is the technique we use most, and we can justifiably say that it is our specialisation. We can use various pressing techniques, depending on the nature of the work. The techniques that we can use are suitable if the (casing) tubes can be put in place above the groundwater level (or if the groundwater level can be lowered sufficiently). Sometimes, for technical and/or environmental reasons the groundwater level can and/or may not be lowered. Then, we have the techniques in house that are needed to take up the challenge. Strukton Infratechnieken has various types of drilling and boring equipment of its own and with it can drill the most commonly occurring diameters.

Vianen I

Strukton Infratechnieken uses the following techniques: 

Open front drilling with an auger

Using hydraulic cylinders, a tube with an open front is pushed into the embankment. The auger, a drill, removes the soil. In this way, bores with a diameter from 100 to 800 mm are made. 

Open front drilling with manual excavation

With diameters greater than 800 mm, the soil at the front of the tube, which may or may not be fitted with a controllable cutting ring, is removed manually. 

Open front drilling with mechanical excavation

Diameters from 1600 to 3500 mm are tackled with diggers that grip in the front of the tube. An Excavator is used as the digger. This is a hydraulic digging arm that is placed in the tube and excavates the front of the bore mechanically, while there is visual control. The excavated soil is fed into a soil carrier on a conveyor belt and then transported to the excavation pit. This method is also suitable for rectangular sections or tunnel cross sections where conventional diggers are used to excavate the soil. 

Closed front drilling with a shield drill

With the closed front drilling technique we use a microtunnelling machine with a slurry shield. With a slurry shield, with pumps, a drilling liquid, water or bentonite, is pumped to the drilling machine through a pipe system in the bore. The front of the drilling machine is fitted with a cutter that rotates and is pressed into the soil by the hydraulic jacks. In this way the soil is supported and dug away into the chamber behind the cutter, the flushing chamber. Here the soil is mixed with the drilling liquid. The cuttings are transported away via the discharge line towards the pressure cylinder, after which it reaches the separator. This separator removes the coarser particles from the drilling liquid, which means that this can be used again to be pumped to the drilling machine. From the pressure cylinder the bore is continually increased in length with standard tube sections until the receiving side is reached. 

Directional auger drilling method

This drilling system is suitable for diameters up to about 600 mm and can be used both above and below the groundwater level. Below groundwater level it is a good (economic) alternative to closed front drilling. Because the bore is preceded by a guiding pilot bar, great accuracy is achieved. Partly because of this, this pressing technique is used for laying passages for wildlife. This method is also extremely well suited for working in areas where space is limited.