Research Projects

India, with its extensive 7600 km coastline, has immense potential for harnessing offshore wind energy. The Indian government has set an ambitious target to achieve 30 GW of offshore wind energy capacity by 2030. This goal is pivotal for diversifying the nation's energy mix and fulfilling commitments to carbon reduction and global climate change mitigation efforts. However, achieving this target presents significant engineering challenges, especially in regions with carbonate sediments, which are prevalent along the West Coast of India and are known for their complex geotechnical properties. Compared to silica sand, carbonate sand possesses higher angularity, lower grain hardness, and greater intraparticle porosity. These distinct properties significantly affect the behaviour of foundations built on carbonate sediments and can strongly impact the stability and long-term performance of offshore foundations. Further, carbonate sediments possess distinct characteristics, and not all carbonate grains display the same attributes. Experience from regions such as the Middle East and Australia, where carbonate sediments are common, underscores the importance of tailored design practices. For instance, standard procedures in these areas often limit pile shaft resistance to 15–20 kPa. However, limited field studies from India's West Coast have reported instances of higher shaft resistance, at times reaching up to 80 kPa, highlighting the necessity for region-specific geotechnical analyses. Further, under cyclic loading, literature suggests that particle crushing can increase due to shearing, producing more fines content, which impacts soil behaviour. This project seeks to bridge the knowledge gap by providing crucial insights into the behaviour of carbonate sediments and developing optimised foundation design methodologies. Laboratory characterisation tests, such as direct shear, ring shear, and cyclic simple shear will be conducted to quantify particle crushing under various conditions and to identify the parameters governing this behaviour. Stress-dilatancy characteristics will be evaluated, as well as the influence of in-situ conditions on the critical state line and the state parameter affected by particle crushing. Soil-steel interface interactions will also be examined in detail. This project will study the cyclic response of carbonate sediments, assessing the influence of various cyclic loading characteristics. The findings will guide the evaluation of existing constitutive models, including those developed for crushable sands. Should the need arise, a new constitutive model accommodating compression and shear-induced particle breakage specific to carbonate sands will be proposed. The outcomes of this project will enhance the understanding and design of offshore foundations in carbonate sediments, benefiting offshore wind energy and other marine structures, and supporting sustainable offshore development in India.