by Matt McLean, Operations Manager at Mainmark Civil and Mining
As traffic density continues to increase with population, keeping society from grinding to a halt often rests on tunnel infrastructure.
Tunnels help to alleviate congestion, promote smoother traffic flow, and minimise disruption in built-up areas. They are a highly valued element when developing urban environments, which is why a number of tunnels have been included in the national infrastructure boom, such as the new Sydney Harbour tunnel in New South Wales and the North East Link project in Victoria.
These important infrastructure projects are particularly valuable for major cities in growing metropolitan areas.
New South Wales, for example, saw 5,892,206 motor vehicles registered in 2020 according to the latest motor vehicle census, with many of those vehicles expected to travel through Greater Sydney.
Tunnels are complex structures that require funding in areas which can sometimes be overlooked, yet this 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 such as Sydney, 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.
The serious implications of water ingress in tunnel infrastructure cannot be ignored, so having a plan and budget for proactive mitigation, like waterproofing and ground reinforcement to minimise the likelihood of costly structural issues post-construction, is essential.
Remediating problems before they occur
With increasing pressure on roads in expanding urban centres, the need for tunnel infrastructure across Australia will be ongoing.
Therefore it is 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 surveying and a thorough geotechnical analysis of the surrounding ground conditions should take place well before construction begins.
This should then be followed with tailored solutions like specialised resins, gels and coatings that are engineered for civil infrastructure use, and introduced before and during the tunnel construction phase.
Based on the experience of Mainmark’s technicians with remediating and strengthening tunnels, understanding what solutions and application techniques to use for different tunnel systems and ground conditions is vital to mitigating potential issues.
By utilising the right solutions, the quality and longevity of Australia’s existing and future tunnel infrastructure can be ensured for decades to come.
About the author
Matt McLean is the operations manager for the civil and mining division at Mainmark. He is a concrete remediation, specialised coatings, resins and waterstop injection specialist with a long history of working with ground stabilisation and grouting technologies.
This is a sponsored article brought to you by Mainmark, for more information go to: https://mainmark.com/
