Pipe Jacking method
In a situation where the sewerage pipes have to be laid in deeper ground (3 to 7 meters), the pipe jacking method will be adopted. This method not only minimises the digging of the trench to lay the new pipes but also alleviates disruption to the public.
2. The soil in the temporary shaft is excavated
3. The pipe jacking machine is then set up at the base of the shaft. Upon confirmation of the alignment, the roller cutter at the face of the cutting head machine cuts the soil in front of it.
4. The excavated soil is then fed to the crusher through a pipe and further crushed to smaller pieces, after which it is transported up to the ground surface in a fluid form using a slurry pump.
5. The excavated soil in slurry form is treated by passing it through a number of screens.
6. The dry spoil is then removed from site, so as to keep the works area clean.
7. The new pipe is lowered in sections behind the cutting head machine and gradually pushed behind the cutting head machine into the area excavated. The excavation and pipe installation cycle continues until the cutting head machine reaches the receiving station with the new pipeline laid behind it.
8. A new manhole structure is then constructed in the receiving shaft.
9. Once the manhole construction is completed, the temporary shaft is backfilled and surrounding area reinstated.
10. Finally the manhole is cleaned and inspected by the relevant agency for handing over and commissioning of the new line.