A Review of the Design Formulations for Static Axial Response of Deep Foundations From CPT Data-Article

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The paper reviews the development of methods for estimating the static axial capacity of deep foundations from cone penetration test (CPT) data. These methods use CPT measurements to predict pile shaft resistance and end-bearing resistance, offering a faster, more economical alternative to relying solely on conventional borings and laboratory testing. Approaches are broadly divided into indirect methods, which infer soil properties before calculating pile resistance, and direct methods, which correlate cone readings with pile capacity.<br /><br />The review traces how direct CPT-based methods have expanded to account for pile and soil type, installation procedure, pile dimensions, open- or closed-ended conditions, soil plugging, and other factors. It examines five methods that use multiple CPTu measurements, noting that each has limitations related to its calibration database or range of applicability. Reliable use also requires attention to corrected cone resistance, the soil influence zone around the pile tip, how CPT readings are averaged, pile geometry, and the criterion used to define capacity.<br /><br />The study refines the UniCone method using 153 pile load tests from 52 sites, covering varied pile types and geomaterials. It expands the method’s soil classification from five zones to eleven and develops continuous correlations between CPT soil behavior index and shaft and toe resistance coefficients. These functions may simplify resistance estimates, but the study finds shaft-resistance predictions more statistically reliable than toe-resistance predictions.<br /><br />The authors caution that no empirical method is universally reliable: performance depends on how closely a project resembles the data used to develop the method. They recommend checking predictions against other methods and applying engineering judgment. Future research should use larger, more diverse load-test databases and make fuller use of seismic piezocone (SCPTu) data. In particular, shear-wave velocity measurements could help extend predictions beyond ultimate capacity to the pile’s full load–settlement response.

Keywords

cone penetration test

CPT data

deep foundations

axial capacity

pile resistance

shaft resistance

end-bearing resistance

direct methods

UniCone method

load test database