The mountains of Ischigualasto in Argentina?s northern province of San Juan, boast the world?s largest collection of dinosaur remains from the Triassic period (195?225 million years ago). But there?s nothing prehistoric about the yellow giants that are now making their way through the rock.
These are Atlas Copco drill rigs ? a Boomer E2 C and a Boomer XE3 C, the first of its kind in Argentina ? that are being used to drive a series of six road tunnels along Route 150 near the Chilean border.
When the project is complete in 2013, the tunnels will help to link up the complex national road network of Argentina and will also eventually provide a modern road system stretching across the entire continent from the Atlantic to the Pacific.
Route 150 runs through a section of the Ischigualast-o mountains with geological formations older than the Andes. Once a fertile paradise for the dinosaurs that roamed the land, it is now a hostile desert with temperatures ranging from ?10° to +45°, just a few days of rain per year and winds that blow every afternoon at 20?40 km per hour. The occasional ?zonda? wind from the west, which blows even harder, increases the heat to an unbearable level.
The fact that the people working for Jose Cartellone Construcciones Civiles (JCCC) are also 300 km from the nearest town, does not make things any easier. As Daniel Castro, Road Construc-tion and Mining Manager says: ?We are very isolated and that makes it very difficult to get personnel, equipment and other resources we need to survive and work here.?
On top of that, the tunnel sites are in a preservation area created to protect the fossils which dictates not only the direction that the roads and tunnels are permitted to take but also their characteristics.
The tunnels are located 1 600 to 1 700 m above sea level and have a total length of 2 400 m, the longest being 500 m, and they all have cross sections of 95 m2.
When M&C visited the area at the end of September, five of them had been excavated and the sixth was well under way. A Boomer XE3 C was working in the final opening of Tunnel 1 while a Boomer E2 C was carrying out limited blasthole drilling and scaling in Tunnel 3.
Due to the difficult geology ? mostly consolidated sandstone formations and heavily fractured shale ? some of the original plans had to be changed.
Fausto Cervini, Tunnel Production Manager, who has extensive international tunneling experience, explains: ?In twenty to thirty per cent of the excavations we found rock of medium difficulty which we call Type 3, and difficult to very difficult rock, Type 4 and 5, in the rest. In tunnel six we even found pure sand that demanded a lot of support work in the initial stage.?
Cervini continues: ?The problem is that the rock is very heterogeneous and very mixed. We have hard and extremely hard limestone embedded in completely loose material, particularly in Tunnel 3. This makes it difficul-t to install grouted bolts and we have to re-drill three or four times.
?In most of the tunnels the Boomer rigs drilled the blast holes without any problems but Tunnel 3 is special. Here, 90 per cent of the work has been done mechanically with hydraulic hammers and cutters of different sizes. Most of the drilling has been for high precision smooth blasting to minimize over-break.?
Cervini has been familiar with Atlas Copco technology for most of his career. JCCC employs Atlas Copco low profile loaders, compressors and generators and has a number of Boomer rigs in mines. When the Route 150 was tendered, it was his recommendation that the latest Atlas Copco rigs be used.
In February when simultaneous excavation of the tunnels was in full process, there were more than 600 workers at the site. Today there are 480. Drilling crews work 14-day shifts with seven days off while ground engineering and civil construction teams work 11 day-shifts and three days off.
JCCC has a turnkey contract to deliver a new 24 km stretch of road complete with six tunnels and five bridges and is responsible for all civil works.
Founded 90 years ago by José Cartellone, JCCC was the first company in the Argentine mining industry. Today, it has extensive activities in heavy engineering, tunnels, hydroelectric plants and road construction with operations in almost all Latin American countries as well as in Saudi Arabia.
Mario Laudani, of Atlas Copco Argentina, comments: ?Cartellone is a company with a prestigious past and a very interesting future. Its commitment to quality, safety, and the environment has put them in an outstanding position and the fact that it is now the first company to use this Boomer XE3 C in Argentina is no coincidence.?
Daniel Castro says he is impressed with the performance of the rigs. ?We are very proud to be the first to get this three-boom jumbo. It is the new generation Boomer with the RCS control system and a laser-guided function that allows the driller to select the coordinates x, y and z and a progam that defines the exact position for each hole.
?We use the rig in the ABC Regular mode and I think it is excellent. The performance is high, even for our high safety and quality standards. The driller works in a comfortable and protected environment ? the way everybody should work in a modern company.?
He continues: ?We tested the new rigs against older rigs of a different brand in similar conditions, and the benefits that the Atlas Copco rigs bring to our fleet and to the Ruta 150 project were clear.
?The cost is substantial but in my opinion it is worth it. And the same goes for our Boomer E2 C, which has the same technology but with only two booms and which is being used in the shorter tunnels.?
The rigs are equipped with raiseable, high-reach cabins, heavy-duty hydraulic booms BUT 45 and COP 1838 rock drills. Working round the clock, the rigs drill blastholes 45 mm in diameter and 4 m long. The average penetration rate in hard rock is 1?1.5 m/min. Eighty holes are drilled for each round and the tunnel is advanced at the rate of 6 m per day. Bolt holes 51 mm in diameter are also drilled.
Training and service
Atlas Copco delivered the Boomer E2 C to the site in 2010 and the three-boom rig in February this year and also provided training.
Castro continues: ?The best thing with these rigs is that they are not complicated. When the rigs arrived, two Atlas Copco technicians from Sweden came and trained our drillers, who were then able to train other drillers, and they also trained our service and maintenance technicians within the context of a three-month support contract. ?This meant that the crews were able to operate the rigs very quickly and since then they have been operating continuously. The value of this training is that we have not had a single breakdown caused by misuse or incorrect operation.?
Castro adds that if tunnelling is to be efficient, it must operate ?like an industry?. ?I believe that drilling, blasting and mucking should be one continuous process. Continuity is the key factor and the service schedule has to be followed very closely. If something stops working, advance is impossible.?
Comfort and safety
For the drillers the Boomer XE3 C represents a big improvement and has helped them to overcome the difficult geology and and harsh conditions. ?One of the best aspects is the extra comfort,? says operator Diego Molina, ?that and the rig?s drilling power.?
Diego and his brother Luís, both from Ecuador, operate the rig in different shifts and both have previous experience of computerized rigs which Diego Molina says made it easier for them to adapt to the Boomer XE3 C.
?It?s a very modern and advanced machine,? he adds, ?and I particulary like the high-reach cab and the 360-degree visibility. It gives you complete control. You can be sure that there is no-one near the rig when it is in operation and that there are no problems with any hoses. This makes it a really safe rig to handle.?
Epiroc operated under the trademark “Atlas Copco” prior to January 1, 2018.