This project will produce learning on improved designs for OHL tower foundations, including a better understanding of the optimal edge profile/roughness, and how this can reduce the materials/space required. It will also provide an understanding of any associated cost
savings and benefits. Preliminary work estimates that the cost savings generated by the more efficient design, per tower with pad and column foundations, could be between 5 – 10%. Average Transmission circuits have hundreds of towers which means that the average
saving per new circuit could be in excess of £1million.
Benefits
The learning from this project can facilitate energy system transition by better understanding OHL Foundation Design and potentially –
• Reduction in embedded C02 and C02 expended in construction due to smaller foundation size and less concrete used.
• Reduced disruption to land as a small area is excavated.
• The potential to deliver required reinforcements at lower cost to customers.
Learnings
Outcomes
Technical and research outcomes:
The project delivered a strengthened evidence base supporting the Giampa (2019) uplift capacity design approach for overhead line foundations in granular soils. Expanded centrifuge testing and 3D finite element analysis (FEA) confirmed that the method provides good agreement with measured uplift capacity when the effective embedment depth is defined based on the observed failure surface origin. This outcome increases confidence in the method and associated partial factors for foundation reassessment and new design.
The project demonstrated that optimising foundation geometry, specifically through the introduction of chamfered pad designs, provides a reliable means of increasing uplift capacity. Both numerical modelling and centrifuge testing showed that chamfer angles above approximately 20–30° shift the failure surface to a deeper origin, increasing mobilised soil mass and shear resistance and delivering uplift capacity improvements of up to ~40% in some granular soil conditions at serviceability displacements.
The geometry optimisation work also quantified material efficiency benefits. A 30° chamfered pad was shown to reduce concrete volume by approximately 18%, increasing to ~35% at 50°, compared with a conventional flat pad of equivalent plan dimensions. This directly supports reductions in embodied carbon and CO₂ emissions while maintaining or improving uplift performance.
The project rigorously assessed the use of geogrids and ground‑improvement solutions as potential means of increasing the uplift capacity of existing foundations. Centrifuge testing and numerical modelling showed that, at serviceability‑relevant displacements (~25 mm), geogrid inclusion does not provide a consistent or reliable uplift capacity improvement, with observed changes ranging from modest increases to reductions. This outcome provides clear, evidence‑based guidance on where such solutions are not appropriate, avoiding unnecessary cost and complexity.
Performance improvement attributable to the Project:
The project demonstrated that foundation geometry optimisation can deliver uplift capacity improvements without increasing foundation size or depth, while simultaneously reducing material use.
It provided a validated basis for less conservative reassessment of existing foundations in granular soils using the Giampa (2019) approach, potentially avoiding unnecessary foundation strengthening.
It reduced uncertainty around retrofit solutions by clearly identifying approaches that do not deliver reliable benefit under operational conditions.
Technology Readiness Level (TRL):
The validated design methodologies for chamfered pad foundations and Giampa‑based uplift assessment have progressed from TRL 2 to TRL 4 through combined centrifuge testing 3D numerical modelling and large-scale laboratory testing.
Opportunities to develop the learning further:
See section 10 for opportunities to develop the learning further.
Detailed deliverable progress reports from University of Dundee and University of Bristol are available upon request.
Significant new learning from the project has been delivered and published in technical journal papers and presented at industry conferences.
Lessons Learnt
Integrated physical and numerical modelling is essential:
Combining centrifuge testing with 3D finite element analysis proved critical to understanding uplift behaviour and validating design approaches. Neither method alone would have provided sufficient confidence in failure mechanisms or capacity assessment.
Geometry optimisation is more effective than additive solutions:
Optimising foundation geometry (e.g. chamfered pads) delivered more reliable and predictable uplift capacity improvements than retrofit solutions such as geogrids or ground improvement, while also reducing material use and carbon impact.
Evidence‑based challenge of assumptions adds value:
The project benefited from testing both positive and negative hypotheses. Demonstrating where solutions do not provide benefit is as valuable as identifying effective innovations, helping avoid unnecessary cost and complexity in future projects.
