Cone Penetration Testing (CPT)
The benefits of CPT
Cone Penetration Testing (CPT) is one of the most widely accepted methods of soil investigation used to evaluate soil conditions and properties. The benefits of CPT for geotechnical testing and site investigation are numerous, including high-quality data, efficiency, speed, cost-effectiveness, and minimal ground disturbance. CPT tests do not require a borehole for testing, which means there is no boring involved, resulting in minimal ground disturbance.
The Cone Penetration Test (CPT), also known as the cone penetrometer test, is an in-situ geotechnical investigation method that assesses soil properties by pushing an instrumented cone into the ground at a constant rate (typically 2 cm/s). It measures tip resistance, sleeve friction, and friction ratio to determine soil stratigraphy, strength, and behaviour.
CPTu (piezocone testing) builds on standard CPT. In addition to measuring tip resistance and sleeve friction, it records pore water pressure as the cone advances. This extra data greatly improves soil classification, helps identify drainage characteristics, and allows assessment of consolidation behaviour — particularly valuable in soft clays, silts, and other fine-grained soils.
Mag + CPT and Mag + CPTu (commonly referred to as Dual Cone testing) combine standard Cone Penetration Testing with a high-sensitivity magnetometer in a single push. As the cone is advanced into the ground, it simultaneously collects detailed geotechnical data — tip resistance, sleeve friction, and (in the case of Mag + CPTu) pore water pressure — while continuously monitoring the Earth’s magnetic field. Any ferrous objects, such as unexploded ordnance (UXO) create detectable magnetic anomalies that are recorded in real time. This dual-purpose method is highly efficient. It provides both a continuous soil profile and clearance information for potential buried metal hazards in one operation, significantly reducing time and cost compared with carrying out separate CPT and magnetometer surveys. It is particularly valuable on sites requiring deep foundations, piling, or where UXO risk has been identified.
Together, CPT and CPTu deliver accurate, real-time information that supports safer foundation design, infrastructure development, and environmental assessments.
