The design of axially loaded driven piles in chalk

• Main Authors: Buckley, R, Jardine, R, Kontoe, S, Schroeder, F, Barbosa, P
• Other Authors: Technology Strategy Board, Institution of Civil Engineers
• Format: Conference Object
• Language: unknown
• Published: Icelandic Geotechnical Society 2019
• Subjects: Iceland
• Online Access: http://hdl.handle.net/10044/1/74976; https://doi.org/10.32075/17ECSMGE-2019-0161

The behaviour of driven piles in chalk is poorly understood; their installation resistance, set-up characteristics and response to cyclic and static loading all warrant further investigation. Current axial capacity design methods have poor reliability, particularly in low-medium density chalk. This paper gives an overviewof research which combined systematic investigations at an onshore chalk site in Kent, UK, with careful analysis of large scale offshore tests. The onshore studies involved reduced-scale open-ended driven piles and heavily instrumented closed-ended Imperial College Piles. The offshore analyses addressed static and dynamic pile tests conducted on full scale open-ended steel tubular piles driven in glacial till and low-to-medium density chalk. The understanding drawn from both streams of research form the basis for a new Chalk ICP-18 effective stress-based design approach, which centres on the key physical phenomena identified: (i) the close correlation between pile resistances and local variations in CPT cone resistance (ii) the marked effect of the relativedepth, h/R*, of the pile tip below any given chalk horizon (iii) the effective stress shaft interface shear failure characteristics and (iv) very significant capacity gains over time. The new method offersbetter predictions of field behaviourwith time than the current industry method.