For release in Europe, Africa and the Middle East: 30 August 2010
The Ceneri Base Tunnel under construction to extend the Swiss AlpTransit line
Besides the works of the renown Gotthard Base Tunnel in Switzerland, part of the Swiss AlpTransit line, this spring work also started on initial drill and blast of another important tunnel: the 15.4 km long Ceneri Base Tunnel in the canton of Ticino from the north portal near Camorino, the south portal at Vezia and in the installations cavern of the intermediate heading at Sigirino. This tunnel with two single-track bores continues the Swiss AlpTransit line south of the Gotthard Base Tunnel and is, like Gotthard, built under contract from the Swiss Federal Government by Alptransit Gotthard AG.
The commercial operation of the Ceneri Base Tunnel is planned to start at the end of 2019. Upon its completion it will allow high-speed rail and heavy freight trains, both of which were not possible in the existing steep track over the mountain of Monte Ceneri.
Tunnelling on the main 2.3 km long access adit to the cavern already started in 2008, using a 9.7 m diameter Robbins TBM. The construction site for the two railway tunnels will be in full swing in autumn 2010. Excavation, support and lining work should be finished in 2016.
The tunnel contractor consortium Condotte Cossi had a long hard look at several manufactures who were bidding for the lucrative machinery order. They opted for the Swiss Cat dealer Avesco who was able to offer the most of the needed machinery to complete the excavation of the twin tunnels. For the Ceneri Base Tunnel Project Avesco, Italian Cat dealer CGT and Zeppelin, the Cat dealer from Germany, are working together. Another plus for Avesco was the experience they gained with supplying and maintaining machinery for the Sedrun section of the Gotthard Base Tunnel. As the “Bautechnik” branch of Avesco is the official dealer for Sandvik, they were able to offer a complete package including eight drilling jumbos, four underground wheel loaders, eight compact radius tunnelling excavators, eight hydraulic hammers, eight special wheel loaders and some support equipment.
The Cat 314D LCR and 328D LCR excavators, customized by the dealer for tunnelling purposes, are a rare species among the large Cat excavator family. While the track frames and the upper-structures look familiar, both booms and dippers are unconventional in shape and size. A further feature on both excavators is the heavy-duty dozer blade fitted to the carbody. Strong covers protect the top side of the blade cylinders. It ensures outstanding stability and also enables any levelling work to be undertaken. While clearing the tunnel crown and vertical face from loose rock, the blade at the rear prevents the machine from creeping backwards. Like every other machine that works on the Ceneri tunnelling site, the eight compact radius excavators are equipped with two fire extinguishers, one in the cab and one on the outside of the excavator.
To change a standard Cat compact radius 314D LCR into a 15.5 tonne tunnelling excavator, Avesco invested a lot of man-hours. What first pops up in one’s eye is the short main boom. The mechanics removed the original 4.65 m long booms and the welders built new 2.01 m long ultra short booms. Except for the strong cylinder cover, the stick and the hydraulic quick coupler are standard. Besides the vicious-looking ripping claw, a 1330 kg Sandvik BR2266 hydraulic hammer and a standard backhoe bucket for loading purposes can be attached to the quick coupler. To protect the operator, a Falling Object Guarding System (FOGS) was added to the cab.
With an operating weight of 43.5 tonnes the Cat 328D LCR is so far the only short radius tunnelling excavator in the 40-tonne-class. The tail swing radius of just 1.90 m only marginally protrudes over the undercarriage. The 328D LCR shares the upper-structure of the 329D and the undercarriage of the 336D L. Its specially designed boom with torsion resistant cross-sections is built by the German Cat dealer Zeppelin. The main boom of the 328D LCR pivots 45 degrees to the left or right of centre. This tilting mechanism allows the excavator to reach maximum operational flexibility in narrow tunnel profiles. The bucket stick is 4.65 m long and can be equipped with all kinds of buckets, hammers and drum cutters. Avesco delivered four 2370 kg Sandvik BR3088 hydraulic breakers for the Cat 328D LCR tunnelling excavators.
For the loading and shovelling duties within the narrow connecting galleries between the two single-track tunnels, Avesco modified four Cat 938H wheel loaders. To make them tunnelling proof, the mechanics shortened the fenders on each side and removed parts of the rear fenders. The maximum width of the loader is now 2.6 m. To better protect the operator from falling rocks, the welders fixed a second roof on the cab and a front windshield guarding. A moving cover prevents damage to the dump-cylinder and heavy steelbeams on the counterweight protect the radiator from side-impacts. The sidedumping buckets were built up to specifications by the Swiss based attachment specialist Ullmann. Like every other Cat machine that works on this tunnelling site, the engine of the 938H wheel loader is equipped with a diesel particle filter and with a ”Fogmaker” fire extinguishing system. In case of an emergency the operator can also manually activate the system.
Every operator has a sticker on the back of his helmet which shows that he has received the proper training from Avesco and is authorized to operate the indicated piece of machinery.
When the drill and blast operation is at full swing, the crew of the intermediate heading at Sigirino will drive the two tunnels simultaneous to the north and south. After each blast a 328D LCR tunnelling excavator moves in and clears the crown and the face from any loose rock and finishes off the tunnel profile with the hydraulic hammer. The cleared area will then be secured with rock bolts, steel meshes and shotcrete before the Sandvik underground wheel loader removes the muck at the tunnel face and side-dumps it into a mobile crushing plant. The broken material leaves the tunnel on an extendible belt conveyor system. About 20 percent of the excavated rock can be reused for onsite concrete production. The rest will be disposed for landscaping the area around the construction site.