APRIL- MAY 2022
Time and planning essential for tunnel projects As traffic density continues to increase with population, keeping society from grinding to a halt often rests on our tunnel infrastructure, Mainmark Civil and Mining Operations Manager Matt McLean says
T
unnels help to alleviate congestion, promote smoother traffic flow, and minimise disruption in built-up areas. They are complex structures that require funding in areas which can sometimes be overlooked, yet the investment is essential to ensure the safety, quality and longevity of these heavily utilised transport corridors.
The relationship between tunnel infrastructure and ground conditions When surrounding ground conditions have not been fully considered during construction, tunnels can become more susceptible to degradation. For example, unconsolidated soil can result in a soft and often precarious envelope for tunnels that is prone to shifting.
This can be problematic in areas where ground conditions are rife with water tables, palaeochannels and weak and unconsolidated sandstone. If these geological occurrences are not identified and planned for in advance, they can affect a tunnel’s structural integrity by causing ground movement and cracking, or significant water ingress
that can slowly degrade the structure. Unfortunately, costly and irreversible damage may not appear for some time as significant deterioration can take a decade or more. In some cases issues may even be completely overlooked due to competing priorities such as meeting the community’s expectation to complete a tunnel quickly to alleviate serious traffic congestion. Yet the serious implications of water ingress in tunnel infrastructure cannot be ignored and having a plan and budget in place for proactive mitigation, like waterproofing and ground reinforcement to minimise the likelihood of costly structural issues postconstruction, is essential. Remediating problems before they occur With increasing pressure on roads in our expanding urban centres, the need for tunnel infrastructure will be ongoing. It is therefore vital that tunnel construction includes a combination of careful pre-construction planning, ground and risk analysis, and the specification of appropriate remediation solutions. Detailed planning, site
38 infrastructurenews.co.nz
