Drilling Under Railway Lines Milligan Street, Perth

The scope of this project was to horizontal drill new ducts and pipes for relocation of existing services, construction of two manholes over new and existing communications ducting.

Works carried out as part of the New Metro Rail project consisted off. Directional Drilling of 10 x DN160 11KV ducts 5M under rail lines for power, 55M Directional Drilling of 3 x DN400 ducts for carrier pipe for new Telstra & Optus ducting, 55M Directional Drilling of 7 x DN355 ducts for 132kv underground power cables, 100M Construct 2 cutover manholes to pick up new and existing Telstra and Optus cables, 20m2 each Directional Drilling of 1 x DN225 PE gas sleeve for High Pressure, 85M.

The project had many challenging components such as;

• Laying out the 100 metre sections of pipe in close proximity to heavy traffic, pedestrians and active trains.
• Disposing of the ground water, with only one point of regulated discharge, the planning for the job had to take this into consideration with the scheduling of drilling that did not require dewatering to allow discharge pipes to be temporarily installed in the ducts to be used later in the job for cabling.
• The depth of bores under the rail lines, in the water table, interference from the rail lines and overhead powerlines made the job of tracking the drill head difficult but not impossible, the tracking system and bore planner worked well under these conditions.
• Shoring of the manhole excavation on Roe street proved to be difficult given the size of the manhole and the requirement to have no beams or props across the area obstructing the construction of the manholes, sheet piling though ideal proved to be cost prohibitive, so steel beams where installed in the partially excavated manhole location using a standard crane borer at centres suitable to the depth and available steel shields, the system worked well ,providing a safe area for the works to be carried out, at a fraction of the cost of sheet piling, with no risk to the existing services passing through the excavation.
• The manholes required a concrete slab over the top of the units, the plans called for a cast institute slab on each, the idea of precast was put to the client and with consultation with suppliers a system of interlocking components where constructed, enabling the casting to be done off site and the manhole top slabs be installed by crane, this reduced construction time on site and avoided the use of specialised trades on site, for that part of the works.

The entire project was a success with the project being completed on time and to our customer’s satisfaction.