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Reverse circulation drilling
Reverse circulation air injection drilling (RCD)
Reverse circulation drilling is a method of hydraulic circulation drilling to produce boreholes of up to approx. 3.2 meter diameter. In most cases drilling with hammer grab is first carried out. The soil is conveyed using the mammoth pump principle. The flushing current flows in the annular space between borehole wall and drill rod to the bottom of the borehole, from where the flushing current rises inside the drill rod conveying the cuttings with it.
Process sequence for reverse circulation drilling
1. Drilling in the casing and drilling it out by the grab drilling process
2. Setting the RCD apparatus on the casing
3. Connection of the supply pipes and folding down the crowd frame
4. Lifting the cutting head, stabilisers and drilling linkage
5. Filling the borehole with water and start of drilling with the RCD apparatus
6. When necessary, lengthening the drilling linkage until the final depth is reached
Positioning the unit for reverse circulation air injection drilling
The duty cycle crawler crane positions the unit for reverse circulation air injection drilling on the casing. There it is fixed with hydraulically activated clamps.
Drill rod
Single hollow drill rods are screwed together to form a complete drill string. Thus, the required depth can be reached.
Drilling head
Using the drilling head the ground is loosened. This is a cylindrical body fitted with various teeth and bits at its lower end.
RCD drilling with HS 8130 as carrier machine
Piles of 50m depth for a new residential complex in Hong Kong.
Land reclamation in Hong Kong using RCD drilling method
Reverse circulation drilling to create piles up to 80m in hard rock layer with strength of 150 MPa.
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