DM Civil have a pilot boring machine suitable for direct installation of DN150, DN225, DN300 & DN375 PVC sewer pipes into dry soil conditions, which allow the DN75 pilot head to displace the soil; e.g. sands and soft clay.
The technique utilises a pilot steering head, which can be tracked via a right angle theodolite in the boring pit, viewing the LED lights in the head for line & level through hollow tube drill rods and steered as necessary as the rods are inserted. The pilot steering head is attached to 1 metre long threaded hollow tube rods and the head is spun, steered and pushed into position with the rods following behind. The steering head and pilot rods merely compress and displace the soil.
Once all the rods are in position, 1 metre long PVC product pipe with centralised steel auger tubes and flights inside are attached to the threaded pilot rods via a cutting head. This is driven by the boring machine, in the boring pit and spoil is transported down the auger tubes back into the boring pit. The product pipe is jacked in behind the rods, which guides the cutting head and pipes.
As the product pipe is inserted, the pilot rods are removed when they come into the receival pit. Once all the rods are pushed out and the product pipe is in position, the auger tubes and flights are pulled out of the product pipe revealing the finished gravity sewer main.
Bore lengths up to approximately 100 metres with an accuracy of +/- 20mm are achievable.
At DM Civil we have also utilised PVC pipe installed with the pilot boring machine as pilot rods for larger diameter auger boring using essentially the same technique. This methodology allows for longer, more accurate auger boring of steel casing to be undertaken. This technique is a very cost effective methodology used for bores under roads, railway lines, services and structures, in dry ground conditions, where line, level and grade are critical