Microtunneling (Earth & Rock)

One of DM Civil's key trenchless technology capabilities are our slurry microtunneling machines which are capable of installing pipes from DN150 up to DN1800 into soils up to 5MPa strength and rock up to 100MPa strength. These types of microtunneling machines utilise the slurry shield system and can operate in dry or water charged ground conditions.

Slurry is batched at the boring pit, inserted into a slurry tank and pumped through a charge line to the front of microtunneling machine where it is mixed with the cuttings from the cutting head. The mixed cuttings and slurry is then sucked out through a discharge pipe into the boring pit, where it is then pumped up to a vibrating screen separator located on top of the slurry tank. Solids are discharged off the end of the vibrating screens and the slurry falls through to the tank and reused.

The cutting head is driven by an electric motor in the boring head and the articulated head is steered via hydraulic rams. Steering of the machine is adjusted to keep a laser light, set up to line level & grade in the boring pit, on the centre of a target in the boring head.

Either welded steel casing or rubber ring jointed clay, concrete, GRP or GRC jacking pipe is installed behind the boring head. These are inserted with slurry charge and discharge pipes, electrical cables, hydraulic lines and communications cables in 2, 2.4, 3, 4 or 6 metre lengths.

In 2014 DM Civil constructed the Yanchep DN500 gravity sewer utilising DN800 steel casing attached to our Rockman TRW800 microtunneling machine, into which the DN500 GRP sewer pipe was sleeved and grouted.

The technology has the capability of bore lengths up to 300 metres with an accuracy of +/- 20mm using additional in line booster pumps and intermediate jacking stations.

This technique is a very cost effective methodology used for bores under roads, railway lines, services and structures, in wet or dry ground conditions, where line, level and grade are critical.