Comparison of 1-D seismic site response analysis tools for layered liquefiable deposits at an offshore windfarm site

¹ DNV GL, Renewables Advisory, 1601 Rio Grande St, Suite 400 Austin, TX, USA
² DNV GL, Renewables Advisory, 9665 Chesapeake Drive, Suite 435 San Diego, CA USA
³ DNV GL, Renewables Advisory, 4100 Rue Molson, #100, Montreal, Canada

^* Corresponding author: chris.yu@dnvgl.com

Abstract

Various offshore wind farms have been proposed in the Taiwan strait with a long-term target of installing 4.2 gigawatts by 2030. The proposed projects will be in areas with various known faults and areal seismic sources which should be accounted for in design. A reliable prediction of site response for soil deposits is crucial for seismic loading evaluation of existing energy structures and for design of new structures including offshore wind farms in seismically active regions. This paper presents generic results of 1-D site response analyses based on work performed for an offshore wind power plant development site in the Taiwan strait. The deposits in the project area generally consist of layered deposits with liquefiable layers. The site response analyses were initially performed using two different open-source tools, DEEPSOIL and Cyclic 1D. Both equivalent linear and non-linear approaches were adopted for the analyses and additional evaluations were subsequently performed using PLAXIS 2D for comparison with the results from the open source tools. The results from the different tools were systematically compared and provided useful insight on peak ground (seabed) acceleration, acceleration time histories and shear strains at specific depths and design response spectra. The paper includes a discussion of the sensitivity of the outputs to various input parameters for each of the tools utilized in the analyses and the suitability and limitations of each approach for assessing liquefaction potential are also discussed.