Category: From the Field
The Oldest Robbins TBM still in Action? We visit a jobsite in Canada that may be using the World’s Ultimate Workhorse TBM
It’s a long-standing question in the world of tunneling: Which TBM has been operating the longest? What makes it so durable?
In May 2011, I visited the site of the Centennial Parkway Sanitary Sewer Tunnel in Hamilton, Ontario, Canada to find some answers. The rock portion of the tunnel, located in the shale of the Niagara Escarpment, is being bored by a Robbins Main Beam TBM in operation since 1968. The 2.7 m (8.8 ft) diameter machine was first used for a Hydroelectric Tunnel in Tasmania, and is now owned by McNally Construction, who has used it on multiple sewer tunnels in Toronto and Ottawa since 1972.
I arrived at the Centennial Parkway site on a sunny Friday afternoon along with Tunnels & Tunnelling North America editor Nicole Robinson, where we were greeted by McNally Project Sponsor Dave Bax and Field Technician Kenny Baxter.
After giving us some safety instructions, we were handed full rubber suits and boots. “You’re going to need these,” said Kenny. “It’s muddy on the shaft floor, and the material is red. It gets everywhere.” A quick look around the jobsite confirmed his statement—red clay-like material caked nearly everything, from trailers to trucks to boots.
We climbed down a long ladder into the shaft, and were given a tour of the small diameter tunnel. Kenny explained that the ring beams and wooden lagging installed at the tunnel entrance were due to the softer clay material encountered at that point. The rest of the rock portion of tunnel was being supported with rock bolts and steel straps. “The shale material is being recycled to use as brick. The clay was used by a local gun club for berms on their grounds.”
Single track muck cars rolled out as we walked out of the tunnel, carrying more heaps of reddish shale, before they were lifted by a crane and dumped on the surface.
Bax and Kenny mentioned that daily maintenance shifts have helped keep the veteran machine in good working order. Crews regularly check the 12-inch (304 mm) diameter disc cutters, and inspect the cutterhead and critical sub-systems. “We are not expecting a lot of wear. Our estimated completion for this tunnel is about two months,” said Bax. At the time of our Centennial visit, the TBM had advanced 200 m, at 1.8 to 2.1 m (6.0 to 7.0 ft) per hour, with no major issues.
The competent shale rock is certainly also a factor in limiting wear to the machine’s cutterhead and main bearing. Robust core components, including the main beam and gripper system, are key in keeping a TBM running for a long time (43 years, in this case).
Overall, the machine looked to be well equipped for its latest tunnel drive, and though it is impossible to know if it’s the world’s oldest working Robbins machine, it is certainly on the list. If you know of a Robbins machine that’s been operating longer, drop us a line in the comments section. We’d be interested to hear about it, and maybe even visit it!
Being in Field Service can have some interesting moments, particularly when working overseas and in countries where the English language might not be the first language. We are a department of personnel drawn from all over the world, so we each have our own take on English and the way to speak it. Add to this workers who speak a local dialect, and even communicating with each other can be confusing or comical, to say the least. Read below for some lighthearted moments at field service projects around the world.
Field Service personnel often get by with sign language, drawings on the back of cigarette packets (a rarely used device these days as most of us have quit!) and by any means possible to get a point or question across. In some of the more frustrating conversations we resort to shouting the same question, as it would appear we think people can understand English by raising our voices.
On occasion we could be in a scene from a Monty Python Sketch–A reply to the question “Do we have no cutter wedges?” was met with a positive “yes” answer. “So where are they then?”, “We have none.” It’s all very confusing, but the way the question was asked prompted the answer, so “Yes, we have no cutter wedges,” would appear to be correct when taken literally. A few years ago one of our guys (no names mentioned) was trying to explain to the waitress that we wanted one of those fancy Italian Ice Creams for dessert. Imitating holding the ice cream and moving it to his mouth several times didn’t go down too well, with a somewhat embarrassed waitress as I recall, but it was all taken in good humor (we got the ice cream by the way).
Lost in Translation
When we try to get smart and speak the local language the results are even worse…or better depending on your outlook. In Spain while ordering lunch, Macaroni with Tomato Sauce (Maccarones con tomate) came out as ‘Maricones con tomate’, which turned out to be ‘Gays with Tomatoes’…that brought more than a few smiles to the table and a bewildered look to the waiter’s face. We still talk about it to this day.
During a lunchtime chat between three of our guys, two Americans and a Scottish guy, the topic of conversation came around to hunting. The two American guys mentioned that they had been hunting Moose somewhere in the USA a few years back and that they had needed special ammunition for the rifle. “Hunting Moose!” said the Scotsman in his strong dialect, with a confused look on his face, “Where I come from a Moose (dialect for a Mouse) is only 3 inches long!”
A few months ago we were working in China and came across this sign in Shanghai:
I did as instructed, went down the stairs, turned around and walked backwards… I couldn’t find the restroom or a Policeman??
So as you can see, communication in the field is important. There is no need to shout. Be humble and respectful, and think about the question and the way to ask it–whatever country or situation you’re in. Sometimes what you say or the sign language you use to get your message across can be misinterpreted, often with unexpected results.
As is often said: “When in Rome, do as the Romans do.” And a final word of advice…be careful of any sign language you use, especially when asking for ice cream, more so if you’re in Italy, you’d probably end up with a slap there!!
Visiting Mexico City’s Newest Metro Tunnel: How the Country’s Capital is Upgrading its Aging Infrastructure
I was lucky enough to visit the jobsite of the Mexico City Metro Line 12 tunnel in October, along with Tunnels & Tunnelling International’s features editor Nicole Robinson. The country’s largest TBM, a 10.2 m (33.5 ft) diameter Robbins EPB, is excavating Mexico’s first new rail route in 10 years, below southern areas of the city. The 7.7 km (4.8 mi) long Mexico City Metro Line 12 is being excavated just 7 m (23 ft) below downtown areas in mixed ground including watery clay and boulders up to 800 mm (32 in) in diameter. The project is one of two major tunnels being constructed in Mexico City, the other being the 62 km (39 mi) long Emisor Oriente wastewater project, using six TBMs including three 8.93 m (29.3 ft) diameter Robbins EPBs.
During our visit to the site, the machine was between its first and second cut and cover station sites (it will hole through into seven such sites during the course of tunneling). We walked through the tunnel to view the machine, and later sat down with metro director Enrique Horcasitas of the Mexican Federal District for an interview on the current state of tunneling in Mexico.
Interview with Metro Director Enrique Horcasitas
Q: Were other methods besides tunneling with an EPB TBM considered for this tunnel?
A: Originally, the line was envisioned to be constructed using a technique of slurry walls cast in place. Most of Mexico City’s underground lines were built using this method. However, opening and closing city streets was not possible for a large portion of this route, while open cutting would interfere with existing municipal facilities and fragile archeological sites. In addition, cost estimates placed open cut excavation of the entire 24 km (15 mi) line at 19.5 billion pesos (USD $1.57 billion).
Our engineers needed a solution that would reduce risks and adverse impacts to traffic flow, as well as reduce project cost. For several weeks, methods were studied, and it was ultimately determined that a solution using multiple methods would work best. The 7.7 km (4.8 mi) long tunnel between Mexicaltzingo and Mixcoac would be excavated using a mixed ground EPB TBM, while the rest of the line between Atatonilco and Tláhuac, in much more difficult ground, would be constructed on the surface. Smaller portions of the tunnel would be constructed using cut and cover methods. The overall plan has a budget of 17.58 billion pesos (USD $1.41 billion).
Q: What does the city forecast for future ridership?
A: In the short term, it is expected this project will meet an average demand of 437,000 users per weekday. By 2030, this number is expected to grow to 600,000 users.
Q: How was the route of this line determined?
A: There is a long history associated with Mexico City’s metro plan. Engineers used to think it was impossible to excavate underground, given Mexico City’s highly complex geology. But in the 1950s and 60s, crews hand-mined the city’s main wastewater line, Emisor Central, about 100 m (330 ft) below ground. After the encouraging results, about 41 years ago, the project’s current contractor ICA (Ingenieros Civiles Asociados) began to make feasibility studies about metro lines running through the city. ICA was contracted to excavate the capital’s first metro lines, and 10 years later ICA gave the Federal District a gift: A master plan with over 300 km (185 mi) of rail that would serve as our template for decades to come.
The master plan is reviewed every 10 years, and it was most recently determined to build Line 12. The alignment is almost entirely true to the master plan, though it was made a bit longer after being reviewed by advisors, to match public demand for transportation.
Q: Are there any other metro expansions that the city is considering?
A: We are looking at doing an extension of the new Line 12, depending on the available budget. This extension would include 1,400 m (4,600 ft) of tunnels west of Mixcoac.
The next line we are considering in the master plan is Line 15, which would run directly below Insurgentes, the longest avenue in the world (18.8 km/11.7 mi), which goes straight through the city. A metro is absolutely needed on this route, as there are currently about 10,000 people per hour riding on just buses alone in each direction.
Q: Do you think current opinion about TBMs is changing in Mexico? What is the current climate towards TBMs?
A: I think the public can see the success of this tunnel—we arrived into the first station with precision, only 1 cm (0.4 in) to the side. We are monitoring settlement, and have detected only about 2 cm (0.8 in) at maximum—well within the limits and not enough to affect buildings. The public voted on where to excavate the next new line, they decided where to go, and so there is a consensus in society. I think that is why there has been a high degree of acceptance.
The operation of TBMs is seen as more favorable than hand mining or open cut, because there is less inconvenience at the surface, and building the tunnel itself is safer. For this reason, I think TBM tunneling will continue to increase in Mexico.
With the six TBMs currently excavating or being readied to excavate the new Emisor Oriente wastewater line, we now have seven TBMs operating in the country—this has never happened before. I think this is a tunneling boom!
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