The complexities of Irish geology 

Ireland’s complex geology, particularly across Greater Dublin and the surrounding areas, is among the most variable and challenging in the country.   

The city centre and north of Dublin sit on the ‘Dublin Basin’, a region of fine-grained, dark limestone and shale, often called “Calp”. The west side, towards Kildare, is made up of huge, pure Carboniferous limestones. In the south of the region, the limestone transitions into igneous rock, which is mainly Leinster Granite. Much of the bedrock is layered by thick glacial deposits, the most common being the ‘Dublin Boulder Clay’, which is a mix of clay, silt, cobbles and boulders. These varying bedrocks, makes it difficult to predict how the ground will behave. 

River valleys also pose certain challenges. Soft, alluvial soils built up over thousands of years in low-lying areas are more susceptible to settlement when subjected to frequent, heavy loads imposed by the rolling stock. A network’s proximity to rivers and lakes adds more complexities as there is a higher risk of erosion affecting embankments over time.  

Such complexities in the ground conditions are challenging for major infrastructure projects as soils can vary dramatically over very short distances. 

The risks of overlooking ground conditions 

These complex ground conditions create a set of risks for rail infrastructure that need to be understood and addressed before construction work can begin.  

One of the most significant issues is differential settlement, which refers to the uneven sinking of the subgrade. This can cause railway tracks and associated structures to move unevenly. Even the most subtle settlement differences can trigger costly intervention.  

Void formation is another concern. Voids can develop gradually beneath platforms, structures and embankments, which are often created by the consolidation of loose fill, the decay of organic material, or water movement through permeable ground. These voids are invisible until something on the surface moves or fails. The remediation works required to fix the issue is typically far more extensive than early treatment would have been.  

The cost implications are significant too. Ground movement identified during construction or planned engineering works costs far more than what proactive investigation requires. For major infrastructure projects with fixed programmes and budgets, especially those bound by public funding accountability, it’s not a risk asset owners or project managers should take.  

Getting ground risk management right 

There are ways to manage the risks as long as they are deployed at the right stage of the project. A proactive approach to identifying and managing the risks early on in the programme will help prevent further costs and delays once construction is underway.  

Arranging a thorough ground assessment ahead of construction is vital as it allows engineers to build an accurate picture of what’s happening in the subgrade. If weak substrates are identified, targeted ground improvement works can be carried out in advance of construction. These works can strengthen the ground and reduce the risk of differential settlement or void formation during or after the build.  

How Mainmark Ireland supports infrastructure projects 

Mainmark is a ground engineering specialist with extensive experience in delivering ground improvement and void filling solutions on time-sensitive infrastructure projects across Ireland.  

Our modern techniques such as resin injection can be used to strengthen or improve the subgrade beneath the track or platform structure, requiring no excavations. Our specialists can treat large sections of the railway one section at a time, allowing the railway line to be restored and ready for use again almost immediately. 

For engineers and project teams working on Ireland’s rail expansion, taking a proactive approach is essential in avoiding extensive or costly repairs when something goes wrong. Early engagement with a ground engineering specialist, is one of the most important risk management decisions you can make. 

If you want to discuss ground investigation or improvement needs on your infrastructure project, contact the Mainmark Ireland team today.