A 20-tonne CPT truck with hydraulic rams pushing a cone at 2 cm/s into the silts behind Aberdeen Harbour. That's how we start. The rig's continuous sleeve friction and pore pressure readings feed straight into the cyclic stress ratio model. Aberdeen sits on the boundary between the Dalradian metamorphic basement and deep Quaternary deposits—over 25 m of loose to medium-dense sand along the lower Dee valley. When the water table sits barely 1.5 m below ground, as it does in Torry and Footdee, the risk of flow liquefaction under a 0.10g peak ground acceleration becomes a design constraint, not a footnote. We run the CPT test for continuous profiling and pair it with SPT drilling where gravel lenses distort cone data. The combination gives us a reliable factor of safety against liquefaction for every layer.
A factor of safety of 1.0 means the soil has liquefied. We design for 1.25 minimum in residential and 1.5 in critical infrastructure.
Our approach and scope
Site-specific factors
Compare two sites in Aberdeen. One on the granite outcrop near the Royal Infirmary at Foresterhill—competent rock, no liquefaction concern. Another 3 km east in the harbour area, where 18 m of loose marine sand overlies glacial till. Same earthquake, utterly different outcomes. The harbour site could see 40 mm of post-liquefaction settlement in a single event. The granite site won't move. This is why a city-wide seismic microzonation matters. Aberdeen's industrial zones along the River Don—particularly the energy park at Bridge of Don—sit on alluvial terraces with high water tables. We've measured SPT N-values as low as 6 in the upper 5 m there. That's a clear trigger for ground improvement or deep foundations. Mitigation options include stone columns for densification and drainage or vibrocompaction for clean sands. The decision tree starts with a defensible liquefaction assessment—not a generic report—so the contractor knows which cubic metres of soil need treatment.
Regulatory framework
BS EN 1998-1:2004 + UK National Annex (Eurocode 8, seismic design), BS EN 1997-1:2004 + UK National Annex (Eurocode 7, geotechnical design), BS 5930:2015+A1:2020 (Code of practice for ground investigations), BS EN ISO 22476-1:2012 (CPT) and BS EN ISO 22476-3:2005 (SPT), BS 1377-8:1990 (cyclic triaxial strength tests)
Complementary services
Screening-Level Liquefaction Assessment
Desktop study with geological mapping review, groundwater data and existing borehole logs. We apply the Chinese criteria and Bray & Sancio (2006) fines-content screening to determine whether a full investigation is required. Suitable for low-risk sites on competent strata.
Field-Based Liquefaction Analysis
CPTu and SPT field campaign with hammer energy calibration. We compute cyclic stress ratio, cyclic resistance ratio and factor of safety per layer. Includes liquefaction potential index mapping across the site. Deliverables meet BS EN 1998-5 Annex B requirements.
Advanced Laboratory & Mitigation Design
Cyclic triaxial and cyclic simple shear testing on high-quality samples. Site-specific ground response analysis using DEEPSOIL or equivalent. We design ground improvement (stone columns, vibrocompaction) and provide post-treatment verification testing to confirm performance.
Typical parameters
Common questions
What is the cost of a liquefaction analysis in Aberdeen?
A screening-level assessment starts around £1,970 for a single residential plot. A full field investigation with CPT and SPT, lab testing and a signed report under BS EN 1998 typically ranges from £2,800 to £3,410, depending on borehole depth and the number of test locations. Complex sites requiring cyclic triaxial testing and ground response analysis will cost more. We provide a fixed-price proposal after reviewing the site geology.
Does Aberdeen actually need liquefaction studies given the low seismicity?
Yes, for certain ground conditions. UK National Annex to BS EN 1998-1 mandates liquefaction assessment for sites classified as ground type D, E or S2. Much of Aberdeen's harbour, riverside and alluvial terrace land falls into these categories due to saturated granular soils and a shallow water table. The 2020 North Sea tremor is a reminder that intraplate earthquakes, while rare, can generate accelerations that matter for loose sands.
What field tests do you use for liquefaction analysis?
We primarily use the Cone Penetration Test with pore pressure measurement (CPTu) for continuous soil profiling and Standard Penetration Tests (SPT) where gravels or obstructions prevent cone penetration. CPTu gives us sleeve friction, tip resistance and pore pressure in one push—ideal for the Robertson (2009) soil behaviour type classification. We calibrate SPT hammers to measure energy ratio and correct N-values per NCEER guidelines. For Vs-based methods, we run MASW surveys.
How do you calculate post-liquefaction settlement?
We apply the Zhang, Robertson and Brachman (2002) method using CPT data or the Ishihara and Yoshimine (1992) method when working from SPT data. Both correlate the factor of safety against liquefaction to volumetric strain, which we then integrate over the liquefied layer thickness. For critical infrastructure, we validate these empirical estimates with cyclic triaxial test results on undisturbed samples from the project site.