Development of a novel rock anchoring system for floating renewable energy mooring

This project will develop understanding and design procedures for a novel rock anchor that has been developed for simple installation in offshore environments where high tidal current velocities and environmental controls exist. The anchor concept has the benefit of being self-drilling and does not require any additional grouting operations. The anchor will be designed and optimised to operate under the specific requirements for floating tidal stream generators and future floating wind. The research will use a mix of advanced numerical simulation and laboratory validation to develop simplified design and specification techniques.

In 2011, the worldwide total capacity of energy generated from tidal stream almost doubled. By the end of 2011 it was responsible for 527 MW. Comparing the total capacity to other types of renewable energy (e.g. wind energy had 238 GW of total installed capacity, 2011), marine energy is at a relatively early stage of development and there is significant potential for increased output. 2.5 GW of tidal stream energy could be deployed by 2050, if the overall levelized cost of energy is reduced. By 2015, 2.1 MW of tidal stream energy was installed in the U.K. The Carbon Trust examined 36 sites around the UK, which have 99.5% of the U.K.’s identified tidal current resource. In terms of UK potential, in Scottish waters this is believed to be a significant proportion. The Northern Isles represents 8%, Up to 8% from the North West and 61% from the Pentland region and Orkney Islands. The key to accessing this potential is improved generator performance and reduction of installation costs where foundation and anchoring can form up to 30% of these.

The industrial partner has developed a rock anchor from the perspective of ease of installation and mechanical performance but requires assistance in developing a robust and efficient design methodology that works in different rock types, strengths and structures. They are also interested in any efficiencies the research can bring in driving down the cost of the anchors both from a material input perspective and through better understanding of performance. It is often thought that rock anchoring is a well understood and straight forward method of anchoring, with its basis in onshore civil engineering works. These anchors though rely on grouted-in tendons to operate, and design is based upon the failure at the weakest point which is the grout anchor tendon bond or the grout-rock bond. The Sustainable Marine Energy (SME) anchor does not use these elements and works on a self-drilling expanding concept that is designed to push failure into the rock and significantly increase holding capacity. Thus, it removes the need for grouting and multiple under water operations which are dangerous for divers and lead to environmental discharge. Unfortunately, as rock-rock failure is rarely considered the most likely failure mechanism in a classic rock anchor, design on this basis has not evolved since the 1970s and is highly conservative and simplistic which leads to anchors that are large, over designed and expensive. To investigate the true performance of the SME anchor concept requires a mix of specialist numerical modelling and laboratory testing which is not available in the private sector and could not be undertaken to the appropriate degree of rigour under commercial pressures. The project requires specialist knowledge of modelling in rock and how this could be translated into commercially efficient numerical approaches (e.g. Limit State approaches) and distillation of this challenging material and rock-anchor interaction behaviour into a simplistic but robust design methodology allow deployment in a variety of rock types.

You will be co-supervised by Professor Ana Ivanovic (University of Aberdeen) and Mr Adam Caton (Sustainable Marine Energy).