MECHANISED TUNNELLING | TECHNICAL
DRIVING SLURRY ROCK TUNNELLING IN SMALL DIAMETERS
A discussion on the latest trends and technologies for small-diameter slurry mechanised tunnelling in rock. This article is based on two papers by Herrenknecht engineers – ‘Rock tunnelling in small diameter: latest trends and technologies’9
, and ‘Slurry pipe jacking in hard rock: Pushing boundaries for sustainable infrastructure’11
IMPETUS FOR EVOLUTION Trenchless installation methods like slurry pipejacking are important to performing the fast and safe installation of underground utilities while having minimal impact on the project surroundings. Slurry pipejacking originally comes from the more
traditional applications of sewerage and water tunnel construction. Today, new no-dig methods offer planners, power grid operators and construction companies a wide range of potential solutions to build their infrastructure networks. The range of applications includes trenchless cable or pipeline routes, outfall and intake tunnels for seawater desalination, or pipeline landfalls. Use of the tunnelling technique covers the geological
spectrum and is flexible on diameters, drive lengths, and depths of installation. In the past, from a geotechnical point of view, though, its applicability was limited in hard rock conditions and in the non-accessible diameter range, respectively. Today, utility infrastructure projects must cope with
a wide range of geological settings, including small overburden, weathered rock, rock-soil transitions
as well as fractured and intact hard rock with high strength and abrasivity. Slurry microtunnelling now plays a wider role to help designers and contractors meet project requirements. Technological development has continued with major developments, such as innovations in machine performance, cutting tool design, peripheral equipment, and digital solutions. Together, these technical developments have been
pushing back the boundaries for small-diameter slurry microtunnelling TBMs (MTBMs) in hard rock.
NEW ROCK GENERATION: AVN 800 HR As utility tunnelling calls for longer drives, especially in the small diameter range, technologies have developed to extend the application range of slurry microtunnelling. While this has created more possibilities for how to, practically and economically, design and create underground assets there has been the continued challenge of ground conditions for small diameter tunnelling, notably in hard rock. For that purpose, Herrenknecht developed a new MTBM – the new AVN 800 HR – for small diameter tunnelling in hard rock conditions. The machine is
Above, figures 1a & 1b: Herrenknecht’s AVN 800 HR for hard rock with compact jacking station IMAGES COURTESY OF HERRENKNECHT AG UNLESS OTHERWISE STATED
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