THE ROMAINE 3 temporary diversion contract is part of the construction of a 1,550MW hydroelectric complex.
Located 980km northeast of Montreal, the project includes a dam 95m high, a reservoir of 38 square kilometers and a 1,690m-long intake tunnel.
Hydro-Quebec granted contract works for the hydroelectric development of Romaine 3 to the EBC-Neilson consortium.
Works consisted mainly of above ground and underground excavation, concrete work of the temporary diversion and associated works: road design, construction and maintenance of temporary roads, scaling and consolidation of rock cliffs, excavation of overburden and rock to open the upstream portal, intake channel excavation, tailrace and spillway excavation and underground excavation of the diversion tunnel. Also included were concrete works, shotcrete, drilling and blasting and rock surface cleaning.
The open cut excavation for the intake and outlet channels of the diversion tunnel required the removal of 108,000m3 of overburden material and 212,000m3 of rock excavation.
Tunnel Advance
The contract bid by EBC-Neilson was to build the river diversion to allow construction of the dam.
EBC-Neilson chose to drive this tunnel full face. The normal way of driving a tunnel of that size would be in two steps. First, the top of the tunnel would be driven with a jumbo, followed by benching of the bottom section with conventional surface drills.
In construction the tendency is to believe that full face advance is more expensive than benching. At first, it looks that way, but benching is not efficient and it is time consuming,
because of the need to install the ventilation and services twice. This makes it difficult to meet the schedule, which is probably the most important aspect of a construction project. EBC-Neilson chose to use the full face method with two jumbo Tamrock Axera T12-315. The Tamrock was modified to reach 13 meters for the Toulnustouc project done in 2002 and 2003. EBC was the first to own a T-12 in North America and the first owner in the world for a T- 12 capable of reaching 13m.
These jumbos offer other advantages besides their full face capability. The T-12 jumbos are fully computerized. The drilling layout is inserted in the jumbo’s computer; the jumbo is stationed at the face, aligned by tunnel laser and, finally, the operator pushes the start button.
The computer is then in charge of the drilling. The operator can overrule the computer and drill manually, but after seeing the _ nal results, anyone would prefer to leave the computer do the job. The advantages of the computerised jumbo could be summarised as follows below:
¦ Less over break;
¦ All drilling data are kept in the jumbo’s computer;
¦ Penetration rate is maximised;
¦ Time between holes is reduced;
¦ The face does not have to be marked up for drilling;
¦ Blasting results are improved;
¦ Less manpower for the drilling operation.
EBC started digging 85m in the tunnel at the upstream portal to allow the beginning of the portal concrete as fast as possible considering the tight schedule. After, EBC-Neilson mobilised the crew on the downstream tunnel to carry on with the finishing 266m.
The blast design was developed by our specialized engineer and Dyno Nobel experts. A typical round had 197 holes, 57mm in diameter and 5.8m deep.
The cut was a normal Canadian cut, which works well in the hard rock of the Canadian Shield, in which the tunnels were driven.
Roof, wall and floor holes had to be angled out of the contour about 300mm to allow space for the drilling equipment for the coming round keeping the designed area. The other holes were drilled with a 3 degree upward angle (except the lifter holes) to allow drainage of the water. The explosive loading was performed using two skytrack 10054 equipped with big man basket.
For blasting, EBC-Neilson used Dyno Nobel products and long delay detonators. Blasting vibration was monitored at 30m distance and was limited to 150mm/s Peak Particle Velocity.
The tunnel mucking was done with a Caterpillar 988H wheel loader and five 55t Komastu HD465. Fifty five thousand cubic meters (55,000m3) of rock were excavated by EBCNeilson in this tunnel. A Caterpillar 345D excavator was used for scaling but manual scaling was done afterwards to insure a safe environment.
Ventilation
EBC-Neilson used one 2.1m diameter fan for ventilation. This was a positive system. A 2m diameter flexible ventilation tube was used, manufactured by ABC Canada. Concrete Portal
A concrete portal with two sliding gates was constructed at the upstream end of the diversion. This will allow Hydro- Québec to close the gates to commence filling the reservoir. More than 5,600m3 of concrete were required for the construction of the portal. EBC-Neilson also produced the necessary concrete coarse aggregates using the previously excavated rock material and a sand from a borrow pit.
Rock Plug
Two rock plugs were blasted in this project. The one at the upstream had 9,672 cubic meters and at the downstream 4,250 cubic meters. An electronic initiation system was used for the two rock plug blast. This system provides accurate timing benefits and a better fragmentation to facilitate the mucking.
Ground Support
The ground was supported with 4m and 6m hollow-core mechanical bolts. The drilling was done with two jumbo Atlas Copco 353. Bolts were put in place using a telescopic boom aerial platform called the Titan boom machine. Final torque was done manually. Then flexible wire mesh was put in place using the same platform, all the way up to the face. When far enough from blasting, all mechanical bolts were checked again for torque and grouted in place.
While the water level was very high (5m) during the spring flood waters following the rock plug blast, the rock was removed from the swollen blasted rock that created an access ramp for the mucking crew.
Biological Hydraulic oil was used with the PC800 LC8 for mucking the rock plug blast to avoid the contamination of the Conclusion
EBC-Neilson, and its project management team was supported by efficient, dedicated employees. This collaboration and combined efforts were the fundamental elements in making this project a substantial success.
Innovation and creativity were also major factors.
The project was delivered one month ahead of Hydro-Quebec schedule allowing the diversion of the river behind the original schedule by the dam contractor
