Picture above: The interaction between the Pacific and Australian plates creates one of the most seismically active tectonic environments in the world.
For offshore wind development, seismic assessments are performed as part of the design process for turbine foundation and also for the equipment used to install the turbines (e.g. installation jack-ups).
In addition to the seismic activity, there are generally other challenges that need to be considered in the assessment, such as complex seabed conditions, highly degradable soil due to cyclic loading and challenging environmental conditions (e.g., storm, typhoon). Consequently, more sophisticated analyses than those specified in the codes may need to be performed to satisfy design requirements. At NGI, we consider all aspects holistically to ensure that appropriate assessments are undertaken to achieve the objectives.
NGI's specialist expertise
With our extensive knowledge and experience in the interpretation and modelling of different types of soils (e.g. fine-grained, coarse-grained, carbonate, micaceous, etc), we are well-resourced to perform complete assessment of seismic aspects for offshore wind development, including:
- development of site investigation and laboratory testing programme
- advanced laboratory testing and interpretation of test results
- probabilistic seismic hazard analysis (PHSA)
- site response analysis (SRA) and liquefaction assessment
- assessment of foundation capacity and settlement due to seismic/cyclic loading
- modelling of soil-foundation-structure interaction for wind turbine foundation and installation vessels subjected to seismic/cyclic loading.
In performing the assessments, NGI adopt a systematic approach to optimise the quantity of analyses without compromising the quality and safety.
Research and development
Current research and development activities on this topic include:
- development of total stress model for site response analysis and soil-foundation-structure interaction analysis
- improvement of liquefaction assessment which consider static bias, and its implementation in 2D and 3D scenarios
- improvement of pseudostatic approach for foundation capacity assessment
- implementation of macro foundation elements into a simplified structural analysis software
- improvement of liquefaction hazard models for performance based engineering.
In addition to the above, NGI participates in a joint industry project (JIP) on wind turbine installation jackup guidelines, which includes several geotechnical related topics. Our expertise and involvement in the industry place us at the forefront of innovation and improvement related to assessments for offshore wind development.