Tarcisio B. Celestino began his career in tunnelling, as did so many, as a civil engineer.
“But even though I graduated from the University of Sao Paulo Polytechnic School – which is one of the best, if not the best of the, engineering schools in Brazil – I had never heard about tunnelling on my course. Mine was not the only engineering school which did not teach about tunnelling. Very many engineering schools around the world do not teach it. And that is a problem that I would come back to later in my career, because addressing it became a mission for me when I was ITA President (2016-2019).
His first involvement with tunnelling did not come until about second to third year in his engineering career.
“I was working on the water conveyance system for the city of Sao Paulo. Before then I had only worked on dam design, but I was really attracted by the work in tunnelling. I had a very good mentor in my company at that time, which I am glad about; and, shortly after that I went to Berkeley for my Ph.D. where I had a formal education under Tor Brekke. A Norwegian, he had been professor at the University of Trondheim (NTNU) before Berkley. I am very proud to have been his student.”
Brekke, who died in 2009, was a renowned tunneller and teacher, and many of his students hold him in similar regard.
“Even there, though, my Ph.D. did not deal with tunnels specifically; it was on rock mechanics. But after that I came back to Brazil and I have always been involved with one or more tunnelling projects ever since. I have worked or been a consultant on projects in Brazil, across South America, and all over the world. So I have been around many projects internationally.
“In addition to my career as an engineer, I am a professor at University of Sao Paulo. I am not full time but I hold responsibilities related to both teaching and research.
“I was very fortunate to be invited for this position because it’s actually a very nice blend. The rest of the time I work for Themag Engenharia Ltda., which is a major consulting company in Brazil. I am involved with designs of non-conventional work, so there is a blend of research in my work there also. I take subjects from real designs for the company to research at the university, and vice versa: we can apply results to real projects. And that has worked very well. When I joined the university it had no research department for underground works but I created once. I have been supervising quite a few Ph.D. and Masters students on tunnelling, and that has been rewarding.
“The Masters programme here is much more research oriented than it is, for example, in the United States. In Brazil, the programme involves a thesis, and therefore a level of research. Actually, some of the Masters programmes that I supervised have resulted in publications in journals. So I feel that is part of the return I get from my work.
“As well as my involvement with the University of Sao Paulo, I am co-supervisor of a Ph.D. programme at Purdue University in the US. The main supervisor is Professor Antonio Bobet, whom I met a long time ago; it works very well.
“That mix of academic and commercial work suits me – doing practical work to see a project through and also helping others to research. The academic position also creates some kind of visibility which work at the company does not necessarily provide.
“I can give an example. I got a phone call a couple of weeks ago from a former student of mine who teaches at another Brazilian university. His assignments are to do with tunnelling techniques, safety, and so on, but he has also very interesting projects related to unconventional views of underground space.
“There are some former amethyst mines in the south of Brazil. The amethyst is found in basalt lava flows, and it was mined not by large companies but, as I understand it, by individual miners working on their own. The amethyst mines are now exhausted and the miners have gone, but they left behind the underground spaces which they created and which you might expect to be abandoned. But this is in an urban environment and someone had the idea of using that underground space. So now they have wine cellars in them, they have fancy stores, they have restaurants. The galleries were excavated from a scarp horizontally, so the access is very easy.
An enquiry came to his former student because someone asked: ‘is this safe?’
“It was not designed for the public, for people who are not miners, who are not trained in looking at the roof to see whether or not there is an instability. So he was called in to advise, and he in turn called me,” Celestino says. “I have not visited it yet but I am very happy to have been asked and I shall probably get involved in this.
“I would never have got that invitation if I had only been working for the company. It was only because he was one of my former Ph.D. students that he called me. There have been many situations like that. There are non-academic opportunities that open because of my academic career.
“In my non-academic career I am responsible for the areas of Geotechnical Engineering, Engineering Geology and Transportation Engineering at Themag Engenharia. The consulting company was created more than 60 years ago, in fact, to specialise in designs for hydroelectric plants. This was the time when big power plants were beginning to be constructed in Brazil; there had been small ones before then but when major scaling up began this company was created, and it became quite big in the area of hydroelectric plant design. It actually holds the world record of being the company that designed the greatest amount of generating power at the same time – 27,000 MW. Nowadays, the company works in all areas of infrastructure design, not only on hydro plants but also metro systems, highways and so on.
“With Themag, I worked on hydroelectric power plants and they involved underground works. There was one project in particular that I would like to mention because it sparked one of the interests in my career. It was almost at the beginning of my time with the company – it was the underground powerhouse for a hydroelectric power plant, Paulo Afonso IV. Another company, not ours, had designed it; and the width required for the turbines in the cavern hall was 26m. The lining of this turbine hall was very heavy, however. It was designed as a 2mthick arch of heavily reinforced concrete, cast insitu.
“Unfortunately, it was an unfeasible design, and it was already being constructed. The contractors ran into difficulties. The scale of excavation required – a 32mspan – was too large for the site along with the heavy concrete arch. Eletrobras, which is the federal government organisation for hydroelectric power in the country, realised that the design was unfeasible and put a stop to construction, and also put a hold on the power company developer’s licence.
“They hired Themag, the company I was working for, to sort it out, to remedy the situation. Of course, I had nothing to do with that; I was just a young engineer. But I was very fortunate to have been involved with the company then to learn, for they decided to change the design completely. Instead of a 32mspan, the cavern excavation ended up as only 26m; and, the change was possible because the new design used sprayed concrete lining, which the original design had not considered. Instead of a 2mthick concrete arch, therefore, a 150mmthick shotcrete shell and rockbolts were adopted for the reduced span of the powerhouse cavern excavation.
“So this material, this socalled shotcrete, caught my attention when I was a young engineer, and I saw that it enabled a design that was only made feasible because of it. So my interest in sprayed concrete started right there, even though at that time I did not even know what it exactly was. Later on, on designs with which I have been involved for conventional tunnelling, the use of sprayed concrete has often been central to the solution.
“Another area of work for which I have been involved, as a consultant, is a rock salt solution mining project underneath part of an important city in Northeastern Brazil. Subsidence became a serious problem and the owner decided about four years ago to establish a board of consultants of which I am a member. It has been challenging to interact with very high-level professionals and international companies responsible for state-of-the-art laboratory and in-situ investigation work as well as sophisticated numerical models. Mitigation measures have been implemented based on the results of the numerical models. Following the results from the instrumentation and checking the effectiveness of the mitigation measures has been rewarding.”
Sustainability is another theme of interest. The construction of tunnels uses energy and has high carbon and emissions cost, but their use when considered over the longterm, he says, almost always repays that cost many times over – both in reduction of emissions and in other measures of quality of life.
“Sao Paulo metro is an example of this,” he says. Extension of the city’s Metro Line 5 was recently completed; the new Metro Line 6, under construction and scheduled for opening in 2025, is claimed as the largest current infrastructure project in South America.
“Pollution caused by cars has a lot of negative consequences in cost and in morbidity,” he says. “The Sao Paulo metro has hugely reduced the number of cars in the city. Just think of the monetary savings; and, think as well of the number of people who were suffering and even dying from pollution.”
The World Bank has estimated the greenhouse gas savings over the lifetime of the assets from the extension and modernisation of Metro Line 5 to be 2,960,000 tonnes of CO2 equivalent, when savings from the modal shift away from automobiles and buses to the metro are included. Economic benefits related to these emissions savings are expected to amount to US$75.6 million over 50 years.
He has local tunnelling projects that he is passionate about. One concerns the city of Santos, which is the port that serves Sao Paulo some 80km away. It is actually the largest container port in South America.
“The city of Guarujá lies opposite across the estuary. For decades there has been talk of linking the cities, by tunnel or bridge.” Some local politicians, he says, argue for the bridge. “It would have to be high, to allow shipping to pass; therefore it would need long approach ramps; the bridge and ramps together would total 6km in length; and, those ramps would take a huge amount of riverside land and, worse, would add many kilometres to the journey of each truck making the crossing. We did an analysis and found that the total extra CO2 emissions from lorries and passengers cars on those ramps would add up to much more than having an immersed tube tunnel solution –by an astonishing additional six thousand tonnes per year of CO2 plus 25 million kilometres of extra travel distance,” he says.
A tunnel, on the other hand, he says, would require shorter ramps, to be partly underground or submerged, and it need be only 1.5km long, of which 800m would be underwater. (The road distance between the two cities at present is 45km) Current proposals are for an immersed tube tunnel – the first such tunnel to be constructed in Brazil. It would carry six lanes of traffic, at a maximum depth of 21m. No waterfront land would be taken up; and traffic emissions would clearly be far less. And adds that the only advantage of a bridge over the tunnel, he says, is that the bridge would look good on tourist postcards.
He also notes that Sao Paulo, in addition to being 80km distant from Santos, sits on a plateau at 760m higher elevation; goods unloaded at Santos port must be trucked up the steep and winding gradients of the Serra do Mar escarpment to reach Sao Paulo. Here, too, his imagination suggests a solution that reflects sustainability goals: “A straight rail tunnel, at a constant gradient, with electric locomotives could carry them with far fewer emissions.”
And even the locomotives might be minimised: he suggests, perhaps playfully, an electrically counterbalanced arrangement of carriages, with exporting goods on the downhill carriages pulling the opposite ones uphill. That may sound fanciful. But I tell him that my own home town, on the English south coast, has two Victorian-era funicular railways working on exactly that principle – though admittedly they are metres rather than kilometres long. But why should not the imagination soar, in tunnelling as in everything else? In Tarcisio B Celestino, tunnelling imagination is not in short supply.
