Engineering behaviour of Mercia Mudstone for offshore pile design

Mercia Mudstone deposits encountered offshore present a challenge for foundation design, due to the variable nature of the mudstone's physical and mechanical properties. However, the variation in properties can be broadly categorised based on the observed and measured weathering state of mudstone samples collected offshore. This paper presents an example of the characterisation of Mercia Mudstone, as sampled at the Walney offshore wind farm in the Irish Sea. For the purposes of pile design, the mudstone was broadly classified into the various weathering states; highly, intermediate and slightly weathered mudstone. Generalised parameters, including stress-strain response, were obtained for each weathering state based on laboratory data. These generalised stress-strain responses suggest that the peak and post-peak behaviour depend on the ratio of the measured undrained shear strength to the estimated in situ effective overburden stress. The paper briefly describes how the stress-strain data were input to plane strain finite element analyses to derive p-y curves for determining the undrained lateral response of piles in Mercia Mudstone at the Walney offshore wind farm.

Proceedings of the 8th International Conference, 12-14 September 2017, Royal Geographical Society, London, UK