Project Rationale
This project aims to advance the understanding and design of foundation systems on rock seabeds, to support the necessary expansion of offshore renewables energy (ORE, e.g. wind turbines or wave energy converters). The project will develop new analysis techniques, inspired by new approaches for experimental testing of small scale foundation models installed in rock material.
ORE devices are often located in energetic sites (e.g. Celtic Sea), where sediments have been washed away, leaving a bare rocky seabed. The design of ORE device’s foundations or anchors (e.g. drilled piles) is very conservative and costly because of a lack of
· understanding of rock-foundation interactions;
· design guidance
Innovation and new design guidance are needed to drive foundation cost down, and must be supported by experimental evidence. However, field testing of large scale foundations is extremely expensive. Smaller scale lab testing is limited to intact rock samples, with no geological features (e.g. discontinuities). So advanced modelling is needed at an intermediate scale.
We propose to develop a process to create artificial rock samples (rock analogues), which will mimic the main geological features of rock masses encountered in the field. This will enable the testing of small scale foundations in a repeatable/reliable way.
Methodology
The project will be organised into four work packages, each associated with a specific objective.
WP1. Characterisation of rock masses in situ (rock types, discontinuities…). This will be based on the existing literature, data available in industry and at NOC. Representative synthetic tests sites will be elaborated.
WP2. Creation of rock analogues. Firstly, a process to create pseudo intact rocks must be developed. The process will consist of finding the adequate mix of geomaterials (sand, cement… as per [1]) leading to mechanical properties similar to actual rocks identified in WP1. Secondly, a process to create representative rock masses, including discontinuities, must be developed.
WP3. Sample monitoring. Measuring techniques (e.g. geophysics) will be used to characterise the samples, in order to ensure reproducibility of the experiments.
WP4. Foundation modelling and analysis. Small-scale models of pile foundations will be tested in the rock mass samples. The geotechnical centrifuge facility will be used to scale the initial stress within the sample [2] and the model will be subjected to realistic loading conditions, especially cyclic loading, to measure potential fatigue effect [3]. A simplified theoretical model will be used to interpret the results and predict the behaviour of real scale foundations.
Training
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at Department of Civil, Maritime and Environmental Engineering. Specific training will include:
· State of the art design practice for offshore foundations;
· Advanced physical modelling of foundations (geotechnical centrifuge, actuators, sensors)
· Geophysical monitoring (sensors, data recording, data analysis)
· Utilisation of lab apparatus for rock characterisation (uniaxial testing)
· Lab result interpretation
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