In conversations with industry, TTNA asked what is seen happening in the trends and activities in the trenchless, no-dig and microtunneling markets.
We are pleased to briefly share a range of responses reflecting on North American and international experience.
VIEWPOINT: BLACK & VEATCH Aswathy Sivaram, Tunnel Business Planning Lead, Black & Veatch
“Major conveyance projects are being planned and executed across North America.
“Trenchless installations have picked up momentum over the past 10+ years and we continue to see an uptick in projects.
“Trenchless intakes and outfalls are popping up in our clients’ radars.
“Outside of the traditional water/waste water markets, we are also seeing interest in the trenchless industry from power producers and process industries.
“The need to repair and rehabilitate aging infrastructure and to meet regulatory compliance is also driving an increase in condition assessment and rehabilitation projects.
We have also observed that once owners get a taste of a well-executed trenchless project, they come to rely on and become trenchless champions. Communities, in general, prefer trenchless work to open excavations due to minimal disruptions to their quality of life.’
The company recently completed work on project to construct a micro-tunneled water intake under the Missouri River, in Washburn, ND. A microtunnel boring machine (MTBM), named ‘Pamela’, was used to excavate and install a raw water intake and associated 72” Permalok pipeline under the Missouri.
VIEWPOINT: BESSAC Bernard Catalano, Tunneling Business Development Manager North America, Bessac
“On the microtunneling side, especially in the international side, we noticed that the internal diameter of the microtunnels is slowly increasing which allows the length of the tunnel drives to increase as well.
“Moreover, microtunneling contractors feel more and more comfortable to implement curves which eliminate intermediate shafts.”
The larger diameters allow some access for personnel “to maintain the equipment and intervene in the front of the face to change cutting tools,” which in turn means that reliance on shafts to help withy maintenance is reduced.
Fewer shafts allow for smoother alignments, too, allowing hydraulic efficiency of the infrastructure to improve. The alignments are smoother rather than sections connected by shafts, like lines joined by nodes.
This creates possibilities for different choices of alignments, and perhaps slightly shorter overall, at times – such as case for a project in Ecuador recently.
Counter points to watch for in engineering include the larger diameters have increased risk of face instability and also there larger tunnel volumes means more buoyancy forces have to be calculated out.
Among Bessac’s many projects, a recent one was undertaken was in Paris, France, involving a MTBM on VL8 package 3.
The works were to create a 2.5m (8.2ft) i.d. raw sewer over a length of 980m (1072yd), located upstream of a wastewater treatment plant. Tunneling for the MTBM involved a 500m-radius (547yd) curve. He adds that the radius is well within the capability of the industry for a curve without the need for a jack control system.
Geology along the alignment comprised conglomerate, limestones and sand.
VIEWPOINT: BARBCO Trenchless Tunneling using Guided Boring
There are various ways that trenchless tunneling is completed today. However, one of the most effective, and accurate is through the use of a guided boring machine (GBM).
Guided boring is a highly accurate method for the installation of pipes, conduits and cables using a surface launched drilling rig. A pilot bore is drilled using a rotating drill string and is then opened up to your required size for the product pipe by using a reamer.
The method of guided boring is used in a range of trenchless techniques, such as horizontal directional drilling (HDD), auger boring, and pipe ramming. During drilling when line and grade is crucial, the bit is laser guided allowing for a high degree of accuracy, often within 1 inch (or less) tolerances.
Barbco’s Pathfinder technology is a state of the art Guided Boring System, to combine the proven technology of a pilot tube steering system with the dependability of a conventional auger boring machine. The company says this delivers accurate casing installations up to 60” diameter. The Pathfinder Guided Boring System was introduced in 2005 and has been used in hundreds of instances, it adds
VIEWPOINT: BARHALE, FROM UK Rod Young, Chair of British Tunnelling Society (BTS) and Senior Contracts Manager & Construction Manager with Barhale
In a recent profile interview for his time so far as BTS Chair (since mid-2022), Young made the following points of his work in microtunneling:
“Most of the people who have been Chair of the BTS over the years have been involved in larger diameter projects – the likes of Crossrail, London Thames Tideway, HS2 – the prestige projects of the world just now and all the ones that have gone before.
“And the Chairs have tended to alternate between designers and people on the contracting side. I am neither: I am a practical person, and my background is very much in the smaller diameters. I’ve not done anything more than about 4m or 4.5m (13.1ft or 14.8ft).
“So I’m slightly different from my BTS predecessors. But though tunneling at 2m-diameter (6.5ft) and below may not be so glamorous it is still important. Cables, water, sewerage, communications – wherever something like that has to go under a road or railway you need it. You could call it bread and butter tunneling.”
Young continues: “We do a lot for Network Rail, for example, and there is a lot more of it, widespread around the country. They tend to be quick, small projects; I’m involved in quite a few at the moment. £2m (US$2.49m) is a typical upper budget, and that would include all the main laying of cable or piping as well as the tunneling itself and the linking up at either end.”
He adds: “In one sense microbore is not very different from large-bore tunnelling. It needs the same set of skills and standards. We still use TBMs, though smaller ones, with no onboard operators of course – though pipejacking and now directional drilling are also widely used methods. However, in some microtunnels you cannot actually enter the tunnel yourself, and that does make a big difference.”
Young says: “We are doing numerous crossings for various types of water mains, and these are within that range, 50m to 100m (54.7yd to 109.4yd). But still they take a lot of effort: a lot of time is spent preparing the shafts and putting the props in on either side of a rail track. You can be looking at a 15- to 20-week project by the time you put the access points in, one each side and set up the pipe jacks and associated works. But the actual microtunneling itself might take you four or five, maybe six shifts – and that’s it.
“So small-bore needs a much greater ratio of preparation time to tunneling time; but these tunnels are needed, and they are needed everywhere.”
