Process-based soil behaviour modelling for subsea structure foundations in carbonate sand environment

Lead Research Organisation: University of Liverpool
Department Name: Civil Engineering and Industrial Design

Abstract

Over the next decades, there will be a huge expansion of offshore renewable energy facilities to add electricity to the grid and reduce greenhouse gas emissions around the world. Globally, an estimated 17% annual growth from 22 GW to 154 GW in total installed offshore wind power capacity will be seen by 2030. The UK's Offshore Wind Sector Deal (2019) also sets out a goal for the offshore wind sector output being 30 GW by 2030. To meet the ambition of offshore wind energy exploration, it is of great importance to design cost-efficient foundations which, due to the complexity of subsea soil behaviour, remains a major challenge.

Offshore foundation designs are well known to be conservative, which has led in part to the foundations accounting for 25-34% of the overall budget of offshore wind farms. The design of offshore foundations is particularly difficult for carbonate soils which cover roughly 35% of the ocean floor because (1) the complex mechanical behaviour of carbonate soils for which a reliable constitutive model is yet unavailable and (2) carbonate soils around foundations often experience large deformations, such as during foundation installation, leading to significant changes of their properties which are difficult to evaluate using traditional finite element techniques.

The research proposed in this project aims to develop advanced computer models capable of predicting the mechanical response of carbonate sands at offshore foundations from the installation stage to the operational stage. This will be achieved by developing a novel numerical approach called the particle finite element method (PFEM), for analysing large-deformation soil-water-foundation interactions, and a self-learning simulation framework based on advanced deep-learning techniques for training data-driven constitutive models for carbonate sands. The developed PFEM with the trained data-driven constitutive model for modelling the responses of carbonate sands at offshore structure foundations will be validated under both standard laboratory conditions and high gravity centrifuge testing conditions. The success of the proposed research will not only improve our understanding of the behaviour of carbonate sands surrounding offshore foundations but also provide engineers with a robust open-source computer tool to analyse interactions between submerged carbonate sands and foundations with large deformations and help achieve cost-effective foundation solutions for offshore renewable energy developments.
 
Description 1. Spatial variation of soil strength has a significant influence on the stability of geostructure.
2. Deep learning techniques are powerful; however, for its application to training data-driven soil models, physics should be further considered which may considerably improve its performance.
3. Although a number of numerical approaches have been developed for large deformation analysis, coupled modelling of soil-foundation interaction such as foundation installation and followed consolidation are still a big challenge.
Exploitation Route 1. The developed large deformation analysis model and tool can be used by researchers and scholars in different discipline for granular flow problems.
2. Findings about the influence of foundation installation on post-construction performance can be used to guide offshore foundation design.
Sectors Digital/Communication/Information Technologies (including Software),Energy

 
Title Nodal integration based PFEM (N-PFEM) 
Description A 2D Nodal integration based Particle Finite Element Method (N-PFEM) and the associated computer code have been developed. The numerical model is capable of modelling soils undergoing extreme deformation and free-surface evolution. Details on this method have been documented in the paper 'Zhang, Xue, Jingjing Meng, and Shengyang Yuan. "An implicit nodal integration based PFEM for soil flow problems." Computers and Geotechnics 142 (2022): 104571.' 
Type Of Material Computer model/algorithm 
Year Produced 2022 
Provided To Others? No  
Impact The developed model may be used to analyse post-construction performance of piles in soils. 
 
Description 3D PFEM modelling of large deformation soil flow problems 
Organisation ETH Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution Developed 3D PFEM model and software package.
Collaborator Contribution Dr Liang Wang from ETH Zurich made a significant contribution to the coding of 3D PFEM.
Impact Wang, L., Zhang, X., Lei, Q. et al. A three-dimensional particle finite element model for simulating soil flow with elastoplasticity. Acta Geotech. 17, 5639-5653 (2022).
Start Year 2021
 
Description Development of nodal-integration based method for large deformation analysis of soil flow problem 
Organisation LuleƄ University of Technology
Country Sweden 
Sector Academic/University 
PI Contribution 1. Introduce the Particle Finite Element Method (PFEM) to the researchers from the partner institutions Lulea University of Technology (Sweden) and Southwest Jiaotong University (China); 2. Provide the collaborators with the source code of the PFEM; 3. Provide the ideas on incorporating the nodal integration technique into the PFEM and advice on the theoretical development.
Collaborator Contribution Researchers from the partner institutions further developed the PFEM to make it work based on the nodal integration and form the Nodal integration based PFEM. The extended version is more suitable for modelling history-dependent materials (e.g. soils) because no variable mapping operation is required.
Impact Zhang, Xue, Jingjing Meng, and Shengyang Yuan. "An implicit nodal integration based PFEM for soil flow problems." Computers and Geotechnics 142 (2022): 104571.
Start Year 2021
 
Description Development of nodal-integration based method for large deformation analysis of soil flow problem 
Organisation Southwest Jiaotong University
Country China 
Sector Academic/University 
PI Contribution 1. Introduce the Particle Finite Element Method (PFEM) to the researchers from the partner institutions Lulea University of Technology (Sweden) and Southwest Jiaotong University (China); 2. Provide the collaborators with the source code of the PFEM; 3. Provide the ideas on incorporating the nodal integration technique into the PFEM and advice on the theoretical development.
Collaborator Contribution Researchers from the partner institutions further developed the PFEM to make it work based on the nodal integration and form the Nodal integration based PFEM. The extended version is more suitable for modelling history-dependent materials (e.g. soils) because no variable mapping operation is required.
Impact Zhang, Xue, Jingjing Meng, and Shengyang Yuan. "An implicit nodal integration based PFEM for soil flow problems." Computers and Geotechnics 142 (2022): 104571.
Start Year 2021
 
Description Random field stability analysis of slope in Crag deposit 
Organisation In Situ Site Investigation
Country United Kingdom 
Sector Private 
PI Contribution 1. Analyse the rough CPT data provided by the industrial partner and disclose the spatial variation distribution of the soil strength in Crag deposit in East UK. 2. Estimate the stability of slope in Crag Deposit in East UK.
Collaborator Contribution Provide us with the rough data of CPT tests in Crag deposit, East UK.
Impact Agbaje, Samzu, Xue Zhang, Darren Ward, Luisa Dhimitri, and Edoardo Patelli. "Spatial variability characteristics of the effective friction angle of Crag deposits and its effects on slope stability." Computers and Geotechnics 141 (2022): 104532.
Start Year 2021
 
Description Workshop on numerical simulation method 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact 150 postgraduate students and academics from 12 countries attended this online workshop. Presentations were made followed by questions and discussions. Attendees gained deeper understandings of the available numerical approaches for large deformation analysis.
Year(s) Of Engagement Activity 2021
 
Description iPACT - Morecambe 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact A workshop for connecting researchers, engineers from industry, and local council. It aims to identify people-focused, infrastructure-based solutions to the complex problem of improving social well-being and prosperity in coastal communities through resilient and sustainable regeneration.
Year(s) Of Engagement Activity 2022