We are currently completing a 111-meter Ø550 (GRP) drilling operation at the Maasvlakte, crossing three railroad tracks and a pipe and cable route.
The drilling (actually pressing) is being carried out using of the Closed Front Technique, starting from a pressing shaft. Using a press frame equipped with hydraulic jacks, the drill shield is pressed into the ground, after which the pipes are pressed into the ground in sections. This creates a long train of drill pipes. The drilling mud created by mixing the soil to be removed with water in the drill head is discharged through the new drilled pipes with hoses. A so-called cuff or water trap ensures that no flushing takes place along the outside of the tube. Depending on the type of soil and the amount of casing friction on the pipe, we determine whether an intermediate pressure station is needed. For longer boreholes this distributes the pressing force, something that was not necessary for this borehole.
This Closed Front Technique guarantees accurate positioning. This is because the position of the drill head is continuously monitored by means of a laser, so that in case of deviations, adjustments can be made and the pipe is placed on the designed route.