Investigation of Pile Driving Resistance in Glauconite Sand Using Centrifuge Testing

**INVESTIGATION OF PILE DRIVING RESISTANCE IN GLAUCONITE SAND USING CENTRIFUGE TESTING**:

- Réf **ABG-128914**
- Sujet de Thèse
- 26/02/2025
- Contrat doctoral
- Université Gustave Eiffel
- Lieu de travail- Nantes - Pays de la Loire - France
- Intitulé du sujet- INVESTIGATION OF PILE DRIVING RESISTANCE IN GLAUCONITE SAND USING CENTRIFUGE TESTING
- Champs scientifiques- Génie civil, BTP
- Sciences de l’ingénieur
- Mots clés- offshore wind, monopile, installation, glauconite, centrifuge testing

**Description du sujet**:
**1 | Project description**

This PhD aims at providing better understanding of the behaviour of offshore wind foundations in challenging Glauconite soil conditions to permit further development of marine renewable energy along the US West Coast. In partnership with the US Joint Industry Project (JIP) Piling In Glauconitic Sands (PIGS) and the University of Massachusetts Amherst, this exciting position offers the opportunity to work on a unique experimental research project in collaboration with world-leading researchers and industry partners in offshore geotechnics in both France and the US.

Offshore wind development in the US has focused on the North Atlantic and Mid-Atlantic Outer Continental Shelf (OCS), primarily due to its proximity to high energy demand, shallow water depths suitable for fixed-bottom foundations, and strong wind speeds. The foundation types constructed to date, or now in the design stage, are primarily deep foundations consisting of jacket piles or monopiles. The Atlantic Outer Continental Shelf (OCS) features glauconite-rich sediments, which transform from coarse-grained soil to fine-grained soil upon shearing, causing uncertainty in geotechnical behaviour related to site characterisation and pile foundation installation and long term axial and lateral response.

The PhD student will take part in this JIP effort that aims to address the uncertainties arising from the behaviour of glauconite soils around piles through experimental testing comprising geotechnical centrifuge model testing and laboratory element testing.

**2 | Project Objectives**

The main objective of the PhD project is to develop an understanding of glauconite soil behaviour related to site characterisation and soil-structure interaction to develop a framework for assessing the impact of glauconite on offshore wind infrastructure development related to pile foundations.

The project will utilize authigenic glauconite sediments collected from the US Atlantic coastal plain understood to be source material found at some offshore wind lease areas. The test program will focus on replicating aspects of the JIP onshore test site in New Jersey (Search Farm) and extending the work to other types of soils including allogenic (i.e. reworked) glauconite sands. Samples of crushed glauconite sands will be collected from the model pile walls to determine the degree of particle degradation from the driving process. Extensive instrumentation of the pile including strain gauges and optical fibre sensors will permit analysis of key mechanisms influencing the pile installation and long term performance, providing a unique dataset for future design of pile foundations in glauconite sands.

**3 | Technical approach**
- Research Axis 1: Centrifuge test preparation_
- Test program design using analytical and numerical analysis (provided by PIGS project personnel, see below in « Collaboration »)
- Model pile fabrication and instrumentation
- Design of the experimental set-up to install the model pile by impact hammering and subsequently load testing the model pile axially and/or laterally
- Research Axis 2: Glauconite sand behaviour_
- Pre-processing and laboratory testing of glauconite sand bulk samples collected from Search Farm and other outcrop locations
- Preparation of glauconite centrifuge samples
- Pile extraction and crushed soil sampling and testing
- Research Axis 3: Experimental campaign in centrifuge_
- Geotechnical characterization of centrifuge samples (CPT test, bender element testing)
- Model pile driving and load testing under different glauconite sand conditions
- Research Axis 4: Test Analysis, modelling and discussion_
- Global behaviour analysis of the piles using strain gauges at the pile head for driving forces and axial and lateral capacity assessment
- Local behaviour analysis using optical fibre sensors to assess pile bending, strain and internal force distribution.
- Calibration of SRD models and axial / lateral capacity and response prediction models for glauconite sands.

**4 | Supervision**

**PhD co-director** - Dr. Zack Westgate, from the University of Massachusetts Amherst, is an Associate Professor in the Department of Civil and Environmental Engineering and a faculty member of the UMass Wind Energy Center. He has 20 years of experience in industry and academia in the area of offshore geotechnics, investigating and teaching on topics related to site characterization, offshore foundation de