WET News

rotating cutting wheel with 25 cutters at the front, through challenging ground which included boulders, clay, hard sandstone, glacial tills and old coal workings. The team involved in the Shieldhall Tunnel for Scottish Water, known as the Glasgow Tunnel Partnership, is the commercial joint venture between Costain and VINCI Construction Grands Projets (CVJV). CVJV carried out prepara- tory work, including mine working consolidation, utility diversion work, constructing the first sha„, service cham- ber, cut and cover and the tun- nel boring machine (TBM) launch chamber at Craigton in advance of tunnelling begin- ning last year. The tunnel was launched from a former tram depot site in the Craigton area of Glas- gow, in the south-west of the city. The route of the tunnel goes under Bellahouston Park, Pollok Park, beneath Titwood PROJECT SPECS • Construct a 3.1km tunnel or sewer beneath the south of Glasgow from Craigton to Queen's Park • Tackle flooding and improve river water quality in the Glasgow area TECHKNOW • The TBM had to lay six of the concrete wedges to create one circular ring • It tunnelled at a speed of about two millimetres per minute • The machine's cutting wheel comprised 25 cutters at the front THE VERDICT "The completion of the tunnel construction is testament to the skills, knowledge and determination of our team who have safely delivered a high-quality piece of infrastructure that will have a huge positive impact for the city now and in the future" Neil Grosset, CVJV NEED TO KNOW 1 The engineers' have been working 12-hour shifts as the machine tunnelled away 2 More than 1.5 million man hours of work have been completed on its construction 3 The tunnel is more than five times as long as the Clyde Tunnel Engineers have worked 12-hour shifts on the construction project Staff worked at depths of 35m on the project Road and then under Queen's Park where it will connect with the main sewer system. A sha„ was sunk at Queen's Park to allow the TBM to be recovered when the tunnelling is completed. The route for the tunnel has taken advantage of the large amount of parkland and the wide roads on Glasgow's southside. This was selected to cut down on noise and other disruptions to the area's busi- nesses and residents The TBM has been mining in a varying geology (from very so„ soil to hard and abrasive sand stone) and mixed faces with the possibility of untreated coal seams, or old mine sha„s, have constituted a high-level TBM mining exer- cise for CVJV. The choice of slurry TBM and its data acquisition system (CAP system + Tim), allowed the full control of all TBM min- ing parameters in real time. A slurry treatment plant (STP) with a capacity of 1,200m 3 /h of slurry flow and a treatment capacity in line with the programmed progress rate in each type of ground was installed at Craigton main compound area. All excavated materials have been pumped from the TBM excavation chamber inside slurry pipes until reach- ing the STP outside the tunnel. This avoided any direct contact or possible contamination of the working space inside the tunnel with gas. The STP had been designed to deal with any presence of gas during the slurry treatment works. It was also designed to reuse, as much as is possible, the processed water and reduce the amount of rejected bentonite. The rejected bentonite was in the form of fines mixed with the fines coming from the ground and filtered and pressed to become solid tiles and evacuated. The tunnel lining geometry brought innovation in the methodology of tunnel lining building. The precast seg- ments have all trapezoidal or parallelogram shapes without a small key stone. This is believed to increase the qual- ity of ring built and the productivity. Engineers worked at depths of as much as 32m as the TBM excavated earth and stone and the tunnel's lining in the form of massive concrete rings. The team building the tunnel had worked on some of the biggest construction projects in the world, including the Channel Tunnel. The engineers' have been working 12-hour shi„s as the machine tunnelled away, night and day. A„er arriving on site at Craigton industrial estate the men receive a briefing from the shi„ manager, including an overview of the type of ground they will be working in, and then head for the main entry point to the tunnel, a giant 20m-deep sha„. Having been individually checked above-ground, and given their own tally or num- ber, the engineers climbed down four flights of metal stairs, descending into what looked like an unfinished underground railway station but is actually the entry and exit point to the tunnel and TBM, for all men, materials and equipment. Covered by a sound-proof- ing roof to minimise noise inconvenience to local resi- dents, the sha„ is a vast indus- trial cavern which houses a small-gauge railway and is all rolling stock, cranes, ducting and pipes. The tunnel is more than five times as long as the Clyde Tun- nel – and 4.65m in diameter, big enough to fit a dou- ble-decker bus inside. ONSITE TUNNELLING DECEMBER 2017 WET NEWS 15 The TBM, nicknamed Daisy the Driller, before it started tunnelling 15 months ago

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