Tunnelling challenges: what could be holding construction projects back?

Large tunnelling projects easily stretch out into several years before completion, which make it all the more inhibiting to the project’s progress when something halts tunnelling or construction.
With countless dangers and pitfalls, not to mention simple stumbling blocks, potentially holding back the progress of large projects, the experts at Coleman Tunnelling have compiled this brief list of just some recent examples of when things don’t go to plan and stop a project dead in its tracks.
Leftover Anchors, Cables & Piping
A recent project for a Malaysian firm called MRT was halted during the tunnelling phases when underground anchors and cables were discovered – something which almost set the project back from its 2016 ‘Phase One’ deadline.
The anchoring cables were used during previous building projects to hold supporting underground walls in place during the building process, but were not removed when the building’s construction was finished. The project’s manager, Marcus Karakashian, told the Rakyat Post: “Our Tunnel Boring Machines (TBM) simply tore through these cables forcing us to stop and remove them to avoid damaging the TBMs.”
Tunnel Collapses
Perhaps the most catastrophic, dangerous and time-inhibiting situations that can occur with any tunnelling project is a collapse. There can be countless reasons for why a tunnel collapses from sand inflow and ineffective supporting shields to water inflow and fissure intersection. The knock-on effects from a tunnel collapse, whether that’s simple clean-up operations or more severe outcomes such as rescue operations or fire control, can hold a project back by months or even years.
The online Tunnelling Journal has catalogued an extensive list of tunnel collapses including causes, reasons for collapse, how the issue was resolved and lessons learnt for future projects. If you work in the tunnelling industry, or regularly work with firms for project management, then it’s definitely worth reading – you can always learn from past experiences.
Difficult-To-Bore Materials
The strength of rock and solid materials, when referring to construction, boring and tunnelling, is typically measured in psi UCS – or ‘unconfined compressive strength’. Difficulties can arise, then, when the strength of a material is higher than typically anticipated – and this can be further compounded when the size of the tunnel required is relatively small. This is the exact challenged faced by a US-based team of tunnelling experts when they had to drill a 36-inch diameter hole through rock with a strength of 28,000 psi UCS for sewer lines in Virginia.
You can read a full case study of their project and its challenges here, including their combination of blasting and specialist boring equipment to create the pipelines needed for the sewer installations. 

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