The Mont-Royal Tunnel – tribute to the builders and future challenges

André J. Rancourt, Mario Ruel

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Rock Engineering and Civil Infrastructures

ABSTRACT: The Mont-Royal tunnel was built between 1912 and 1916, by the Canadian Northern Railway, to reach Montreal™s downtown directly from the North passing underneath the Mont-Royal. The 8.7 m wide by 4.5 m high D-shaped tunnel is 5.57 km long and has two railway tracks. The tunnel has also a 55 m high 5 m square section ventilation shaft. Two drill and blast headings were started in 1912 one from the north and the other from the south, and on the morning of Dec. 10, 1913, after 16 months of digging, they blasted the final break through round. Around 357,000 m3 of rock was excavated and hauled out of the tunnel by small rail cars. The partial lining required over 56,000 m3 of concrete. All of this work was completed in four years, but would have finished earlier if it had not been stopped momentarily by the 1st Great War. This tunnel was a remarkable construction achievement considering the technology of the day. It was a historical moment and a turning point for the development of the city and the north side of the mountain.

RÉSUMÉ: Le tunnel du Mont-Royal a été construit entre 1912 et 1916 par la Canadian Northern Railway pour accéder directement au centre-ville de Montréal par le nord en passant sous le Mont-Royal. Le tunnel de 5,57 km de long est de forme rectangulaire de 8,7 m de large et 4,5 m de haut avec une voûte arqué. Le tunnel est muni de deux voies et possède également un puits de ventilation de section carré de 5 m et de 55 m de profondeur. Deux chantiers d™abattages pilotes ont été entreprit en 1912, un au nord et l™autre au sud, et au matin du 10 décembre 1913, après 16 mois d™excavation, la ronde qui relia les deux extrémités fut mise à feu. Environ 357 000 m3 a été excavé et transporté au moyen de charriots sur rails. Le revêtement partiel a nécessité plus de 56 000 m3 de béton. Tous ces travaux ont été complété en quatre ans, mais aurait pu se terminer avant n™eut été d™un arrêt en raison de la première grande guerre. Ce tunnel représente une réalisation exceptionnelle considérant la technologie de l™époque. Cette construction demeure un moment historique et un point tournant pour le développement de la ville de Montréal et du côté nord de la montagne. 1 A VISION OF THE FUTURE A century ago, the project that many Montreal citizens had perceived as an eccentric idea, had become a reality as the first shovels of earth were removed from the ground. The project was to drive a tunnel through the Mont-Royal, the mountain of 211 m height in the centre of the city of Montreal. At that time, many major railways that include tunnels were under construction in the north and the west of the country. So for men like Sir William Mackenzie and Sir Donald Mann, the founders of the Canadian Northern Railway, the idea of boring a tunnel across the mountain seemed the obvious way to reach the city centre. Most of the information presented in this paper was taken from Clegg (2008), although both authors have inspected the tunnel several times, the major contribution for the saving of historical facts and details must be granted to M. Glegg™s book. 1.1 Transport In 1912 the Canadian Northern Railway had access to Montreal only via the east to the remote Moreau Street Station. The Grand Trunk Railway and the Canadian Pacific Railway both had access to downtown from the east and the west respectively. So all favorable routes were closed to the Canadian Northern Railway until Mackenzie and Mann undertook the ambitious project of building a tunnel and a train terminal in the city. 1.2 Town of Mont-Royal: the model city The project also included to build a model city; the town of Mont-Royal on the north end of the tunnel. The right angles layout of the street was crossed by diagonal business streets converging on the railway station (see figure 1). Restrictions were incorporated into deeds of sale to ensure a high quality of construction and development. For example each residence had to be at least two stories, built of stone, brick or cement, on stone, brick or cement foundations. Only detached or semi-detached residences were permitted, etc. These lands soon become very valuable since the tunnel would bring the Montreal downtown within ten minute by train. 1.3 The tunnel The double track, 8.7 m wide by 4.5 m high, D-shaped tunnel was planned to be 5.57 km long. The tunnel would also have a 55 m high 5 m square section ventilation shaft. The plan and profile as presented by the Canadian Northern Railway is shown in figure 1.

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