PIPEJACKING AWAY IN THE UK

Contractor B&W Tunneling Ltd. achieves record production with Akkerman TBM!

Akkerman equipment has been used throughout North America for over twenty-eight years but now our TBMs are getting noticed on the other side of the Atlantic as well. South Wales specialty contractor B&W Tunneling Ltd. recently used a 1.78 meter diameter Akkerman manned tunnel boring machine for pipejacking operatins on the Cardiff, South Wales Sewerage Scheme, being built for the Dwr Cymru Welsh Water Company by main contractor David Lewis Civil Engineering Ltd. With Akkerman's planned increase in activity in the United Kingdom, we couldn't ask for better tunneling production results than B&W Tunneling Ltd. was able to achieve in Cardiff, Wales.

The tunneling and pipejacking industry in the United Kingdom is somewhat closer knit and perhaps has a longer history than in the U.S.A. With many experienced tunneling and pipejacking hands located in a smaller locale there would tend to be more competition; not only for the project itself, but also, with the sharing of labor forces between companies that had the work, as crews hired on, might lead to competition between different crews. Another competitive influence might come from having a strong allegiance to one's 'football' team from cradle to grave. Whatever the reason, there has always been healthy competition in the UK trenchless industry, both at the bid table and while digging at the heading. Competing to get the work is one thing, but these guys have made it a game to compete on tunneling production footage. Those who keep track say that B&W Tunneling and Akkerman have set a production record in the 1780 mm diameter range this past summer in Wales.

B&W Tunneling, an experienced tunneling sub-contractor, had previously teamed up with prime contractor David Lewis Civil Engineering (DLCE) on other work. Steve Williams, B&W's managing director, has plenty of experience tunneling and was probably himself very competitive at the heading at one time or another. Steve and Nick John, Project Manager for DLCE, both were aware of Akkerman equipment and had seen one of our machines in action in the UK with Barhale, another contractor. Perhaps they had found a faster, more mechanized means. Additionally, it was the expected ground conditions of the project that really dictated the use of tunneling or pipejacking instead of open cut trenching.

The geotechnical investigation showed the conditions to be silty estuarine clays with bands of peat. With about 16 feet to pipe invert, the conditions were wet. With the presence of water, the clay would soften and become fluid if subjected to disturbance or vibration. DLCD's Nick John was concerned that even if open trenching could be accomplished, construction activity over or around newly laid pipe would cause settlement and mis-alignment of the completed work. There also could be difficulties with moving heavy equipment; crane mats would be required to avoid getting stuck in the local terrain. Hence the decision to go trenchless. With that came the choice of trenchless methods: slurry microtunneling or a manned TBM. With soil conditions such as silty clays, difficulties could be expected in separating out the spoil from the slurry of a microtunneling operation. In addition, it was thought that the production rate would be higher with a TBM that didn't have to digest the clay in order to advance, a machine that could just cut and remove it without too much disturbance, which would tend to liquify the material. With a dirt bar on the drum and the option to change between a belt or a screw conveyor, the Akkerman 1780 mm TBM was the "right horse for the race course".

B&W Tunneling and David Lewis Civil Engineering have worked together on other projects for DCWW. On this project DLCE and Dwr Cymru Welsh Water utilized a partnering agreement approach on the 20 million (pounds UK) worth of work to build a new collection network and wastewater treatment plant and eliminate the current discharge of inadequately treated sewage into the coastal estuary. The partnering agreement allowed all parties to the contract to influence design and gave the ability to change and use innovative methods of construction as a way to reduce costs while the project progressed. B&W was also a part of the partnering team and, by association through supplying the tunneling equipment. Akkerman was involved as well. It wasn't until Maynard Akkerman visited the site and met with team members that the deal was completed. In the words of Jeff Martin, Project Director for Hyder, the Project Engineer: "While we had faith in the expertise at Akkerman, their visit to assess our local conditions was necessary to give additional confidence before placing this order". It was specifically the partnering agreement that allowed and prompted the suggested change from open-cut to trenchless methods. According to some of the participants, the main difference is that more disciplines are involved throughout the process and that requires a broader viewpoint on the part of all the individuals involved.

B&W quickly mastered the equipment operation with the help of our venerable and well-traveled technician, Red Lowe, who was dispatched with the TBM for the first drive. Initially, the belt conveyor was used but the sticky clay proved to be a problem. A screw conveyor was then used instead, with the belt reserved only for launching the machine, as it is shorter in the pit than the screw. Due to the sticky nature of the clays, it was necessary to spray water on the face and conveying system to prevent material buildup. Interestingly, tidal changes had an effect on the clay too, increasing and decreasing the jacking forces as the tide levels changed throughout the day. Daily initial jacking forces were high but diminished with movement and lubrication. Water ingress did not prove to be a problem and even with shallow cover, little settlement occurred. During production the TBM was able to fill the dirt bucket in about 60 seconds. A winch driven haul system was used to muck out. B&W Tunneling completed six drives and successfully pipejacked a total of 4,570 feet, finishing ahead of the program schedule. According to NATM, New Amalgamated Tunneling Magazine, an industry publication in the UK, on one of the later launches, B&W was able to lower the TBM into the shaft and start tunneling only forty-five minutes later! They also claim that 187 feet of tunnel in a 12 hour shift was a record in that diameter. B&W Tunneling and David Lewis Civil Engineering can certainly be proud of that, Akkerman Inc. surely is.