Development of a high-energy centrifuge model impact hammer for pile-driving

The offshore wind energy industry continues to expand rapidly around the world in response to the demand for clean energy. Research to investigate monopile performance under cyclic lateral loading needs to replicate the installation process as well as the cyclic loading regimes. This has provided the impetus for the development of model pile driving hammers for use in geotechnical centrifuges. This paper presents a new model-scale centrifuge impact hammer that is capable of in-flight driving of large-diameter piles into dense sediments with the flexibility of varying the energy during a test for a more controlled installation. The new hammer is activated by a pair of rotating cams, improving on the pneumatically activated hammer developed in the 1980s, giving greater energy and much better reliability. This paper provides full details of the hammer, together with data obtained at 80g acceleration, driving prototype 4 m wide (50 mm in model scale) piles into dense, dry sand to depths of over 20 m (over 5D) in <1000 blows.