Herrenknecht AG discusses recent advancements in slurry microtunnelling methods that expand its broad application range, especially for small-diameter pipeline and underground cable installations.
Australia is making significant strides in clean energy generation and reliable power grids, as confirmed by the Australian Energy Market Operator’s (AEMO) latest roadmap. Currently, 40 per cent of the electricity in Australia’s main grid comes from renewable sources, leading to cheaper, cleaner, and more reliable energy.
With the closure of ageing coal-fired power stations, AEMO emphasises the urgent need to accelerate the rollout of renewable energy, transmission, and storage. The focus is on harnessing proven technologies to build a sustainable, clean energy grid for the future.
Since the early 1980s, slurry microtunnelling has established itself. Numerous projects worldwide and the broad range of applications in pipe jacking, along with the achieved records in large and long-distance drives, attest to its success. Predominantly, tunnel boring machines with slurry conveyance are used in these applications. The explanation of the AVN technology, with its extensive geological application spectrum, tailored cutterhead designs and hard rock concepts, further underscores its significance. Thus, slurry microtunnelling methods boast the widest range of applications, in terms of pipe material, ground conditions, diameter, installation length and depth.
Microtunnell boring machines (MTBMs) with slurry conveyance are nowadays employed in various microtunnelling processes from classic pipe jacking of concrete pipes to the installation of steel pipes, pipelines, and all kinds of HDPE protective pipes. In response to the requirements of pipeline construction and underground cable installations, Direct Pipe and E-Power Pipe have been developed based on microtunnelling techniques.
These methods create the borehole in a single step and utilise a tunnel boring machine with slurry conveyance, providing continuous mechanical support of the borehole.
The role of jet pumps
A crucial aspect is the installation of pipes in small diameters over long distances. To address this, the concept of the jet pump has been integrated into Herrenknecht AG’s AVN concept, creating the AVNS machine range. As a single slurry pump, the jet pump is integrated into the MTBM and enables a high conveying capacity simultaneously requiring very little space. Due to its compact size, it can be installed in slurry machines from approximately 20-inches and larger, resulting in drive lengths of up to currently 2000m.
E-Power pipe method
Herrenknecht AG’s E-Power Pipe technology has been designed for the installation of non-pressure-resistant HDPE pipes as cable protective pipes but can also be used for small-diameter pipelines of 10-inches to 28-inches diameter underground, wherever conventional methods, like HDD, reach their technical limits.
It is suitable for crossings in difficult, non-stable ground conditions or drilling with low ground cover, and long distances.
The two-stage process integrates aspects of the proven horizontal directional drilling (HDD) technology and of slurry microtunnelling. The broad spectrum of applications ranges from the installation of cable protection pipes for underground cables and bundles to pipelines for gas supply, district heating or the transport of hydrogen.
In the first step the AVNS Slurry MTBM and the reusable, temporary steel jacking pipes are pushed through the ground along the specified alignment by a rack and pinion jacking frame installed in the launch shaft.
After breakthrough at the target point, the MTBM is separated from the pipe string and a pullhead is then attached instead. The prefabricated product pipe lying ready for installation is then connected. Whilst the temporary jacking pipes are pulled back by the jacking frame, the product pipe is also successively pulled in.
The borehole thus remains mechanically supported the entire time. During insertion, the product pipe can be connected to the ground with the addition of backfill material.
E-Power Pipe can work in shallow depths, with high precision and in a wide range of ground conditions. Minimal earthmoving, no heavy equipment between launch and target pits, thus less noise and exhaust emissions, with less impact on the surface are other benefits of this slurry microtunnelling method.
These features are of special interest to modern pipeline projects, with landowners’ concerns, environmental protection, and strict regulation all critical considerations for a project to be realised.
To date, several projects have been executed with E-Power Pipe with an overall total length of 12km. The world record length has been achieved in the Netherlands in January 2022, where a bundle of cable casings has been installed with E-Power Pipe on a significant length of 2km.
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This feature also appears in the September edition of The Australian Pipeliner.