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CPT Testing Dublin | Cone Penetration Test for Irish Soil Conditions

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The Irish National Annex to IS EN 1997-2:2007 explicitly recognizes the cone penetration test as a primary site investigation method, and in Dublin's complex glacial and post-glacial geology, it is often the only reliable way to profile soft deposits without disturbing the sample. From the stiff Dublin boulder clay that underlies much of the city centre to the alluvial silts along the Liffey and Tolka estuaries, we have seen firsthand how a single CPT sounding can replace multiple boreholes when the stratigraphy is layered and variable. Our accredited laboratory processes the data following ISO 22476-1, providing continuous profiles of cone resistance, sleeve friction, and pore pressure that feed directly into bearing capacity and settlement calculations. For projects where the till transitions into loose sands at depth, we often combine the CPT with a seismic refraction survey to map the bedrock interface without additional drilling.

A single CPT sounding in Dublin boulder clay can deliver continuous stratigraphy, undrained shear strength, and consolidation parameters without removing a single sample from the ground.

Process overview

There is a marked difference in CPT response between the dense lodgement till found in south Dublin suburbs like Sandyford and the softer, normally consolidated silts encountered in the Docklands and Ringsend areas. In Sandyford, cone resistance typically exceeds 15 MPa within the first few metres, allowing shallow foundations with minimal settlement. Down along the quays, however, tip resistance often stays below 2 MPa for the first 10 to 12 metres, which forces deep foundation solutions or Improvement. Our field crews use a 20-tonne CPT truck with continuous hydraulic pushing, and we can reach refusal depths of up to 25 metres in the till before the cone encounters rock. When the client needs to verify the shear strength parameters derived from the CPT, we recommend a triaxial test on undisturbed samples taken from a companion borehole. For granular layers where sampling is impossible, the pore pressure dissipation tests we run during the CPT session give us a direct measurement of the coefficient of consolidation, a parameter that controls the rate of settlement under embankment loads. In industrial estates near the M50, where historical fill overlies natural deposits, the friction ratio from the CPT helps us distinguish between made ground and natural soils, something a standard SPT cannot do with the same resolution. We have also found that running a MASW survey alongside the CPT in the deeper Liffey valley provides the shear wave velocity profile needed for seismic site classification according to Eurocode 8.
CPT Testing Dublin | Cone Penetration Test for Irish Soil Conditions
Technical reference — Dublin

Local context

Dublin's population surpassed 1.2 million in the 2022 census, and with the city expanding onto brownfield sites along the Tolka Valley and the Poolbeg peninsula, the risk of encountering undocumented fill and soft estuarine deposits has never been higher. We have seen projects where a desk study suggested competent gravels, but the first CPT sounding revealed 8 metres of very soft clay with an undrained shear strength below 15 kPa — a condition that would cause bearing failure under a conventional strip footing. The economic impact of redesigning foundations after construction has started can run into tens of thousands of euro, and the delay in programme is often worse. For this reason, the liquefaction assessment based on CPT data is becoming a standard requirement for sites near the reclaimed lands of Dublin Bay, where loose saturated sands are susceptible to cyclic mobility even at the moderate seismicity levels assigned to eastern Ireland under Eurocode 8. Our CPT rigs can deploy on sites with limited access, including back gardens and basement excavations, which means you can get the subsurface information before committing to a land purchase.

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Reference standards

IS EN 1997-2:2007 (Eurocode 7 – Ground investigation and testing), ISO 22476-1:2012 (Geotechnical investigation and testing – Field testing – Part 1: Electrical cone and piezocone penetration test), IS EN 1998-1:2005 (Eurocode 8 – Design of structures for earthquake resistance, Irish National Annex), I.S. 260:2014 (Site investigations for building and civil engineering works), I.S. EN ISO 22476-1 (Standard Test Method for Electronic Friction Cone and Piezocone Penetration Testing)

Technical data

ParameterTypical value
Cone typePiezocone CPTu (10 cm²)
Maximum thrust capacity20 tonnes (200 kN)
Typical refusal depth in Dublin till15 to 25 metres below ground level
Parameters measuredCone resistance (qc), sleeve friction (fs), pore pressure (u2)
Data acquisition standardISO 22476-1, Class 1
Pore pressure dissipation testsAvailable at any depth for consolidation coefficient
Reporting formatGEF or AGS digital file, plus interpreted PDF
Derived parametersUndrained shear strength, relative density, OCR, constrained modulus

Common questions

How much does a CPT test cost in Dublin?

For a standard CPT sounding in the Dublin area, budget between €140 and €250 per metre for a single shift mobilization, including the engineer's time, the rig, data acquisition, and a full interpretive report. The cost per metre decreases for multiple soundings on the same site because the mobilization charge is spread across the work. Sites with difficult access or requiring traffic management on Dublin city streets may incur additional logistics costs.

How deep can a CPT rig penetrate in Dublin boulder clay?

In the dense lodgement till that covers much of south and central Dublin, our 20-tonne CPT truck typically reaches refusal between 15 and 25 metres, depending on the degree of overconsolidation and the presence of cobbles. In softer alluvial deposits along the Liffey and Tolka corridors, we can achieve depths of 30 metres or more before encountering rockhead.

Can CPT testing be done on a small residential site in Dublin?

Yes, we operate smaller tracked CPT rigs that can pass through a standard side gate and work in confined spaces such as terraced house back gardens. These units still deliver the same Class 1 data quality as the full-size truck, with thrust capacities of 10 to 15 tonnes, which is sufficient for most shallow-to-intermediate depth investigations in Dublin's suburban areas.

What is the difference between CPT and SPT for a Dublin site investigation?

The cone penetration test provides a continuous, high-resolution profile of soil behaviour without disturbing the ground, whereas the standard penetration test gives a single blow count at discrete intervals of 1.5 metres and disturbs the sample. In Dublin's interbedded till and alluvial sequences, the CPT can identify thin sand lenses and soft clay layers that an SPT would miss entirely. The CPT also measures pore pressure, which is critical for assessing consolidation and drainage conditions.

Location and service area

We serve projects across Dublin and surrounding areas.

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