The back-analysis of shear modulus reduction with strain in weathered mudstone beneath an instrumented embankment
The back-analysis of shear modulus reduction with strain in weathered mudstone beneath an instrumented embankment
Full-scale earthworks trials were undertaken in advance of the construction of the High Speed 2 (HS2) railway between London and the West Midlands. They provided in-situ measurements of the ground response due to loading and unloading from the overlying earthworks. Results from the trials were used by HS2 Ltd to refine the design parameters, make cost savings and eliminate the need for engineering interventions to control ground movement. However, the instrumented trials also provided more fundamental information about the engineering properties of the ground. This is particularly useful in difficult ground such as weathered mudstone.
This paper presents results from back-analyses of in-situ measurements at an embankment trial, 14 km north of Banbury, to measure the stiffness of the underlying, weathered mudstone.
Geophysical shear wave velocity measurements were undertaken to determine the in-situ shear modulus at very small strain. These showed that the shear modulus of the ground profile increased linearly with depth in the clay, consistent with empirical equations. During well-defined construction loading stages, measurements were obtained from extensometers installed beneath the embankment. These were used to measure deformation and strains within the underlying ground profile and calculate the in-situ shear modulus. The shear modulus was normalised to compare with empirical equations for shear modulus reduction with strain. The results showed that the gradient of the normalised, non-linear stiffness of the clays was comparable with those measured in laboratory tests of fine-grained soils, at a range of strains. However, the values for the reference strain (where the maximum shear modulus reduces by 50%) were lower than was predicted by the empirical equations.
Briggs, Kevin
8974f7ce-2757-4481-9dbc-07510b416de4
González, Yuderka Trinidad
e54faa6d-0108-4fe2-b706-3cabe8836729
Meijer, Gerrit J.
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Powrie, William
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Butler, Simon
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Sartain, Nick
f11351ef-d9c0-4c08-ac7c-c69846ce1e44
15 September 2025
Briggs, Kevin
8974f7ce-2757-4481-9dbc-07510b416de4
González, Yuderka Trinidad
e54faa6d-0108-4fe2-b706-3cabe8836729
Meijer, Gerrit J.
0d6d3604-d0e3-43eb-afbe-6638ae74c4ce
Powrie, William
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Butler, Simon
2b577323-b35b-45aa-b6a8-597a3ba25fa6
Sartain, Nick
f11351ef-d9c0-4c08-ac7c-c69846ce1e44
Briggs, Kevin, González, Yuderka Trinidad, Meijer, Gerrit J., Powrie, William, Butler, Simon and Sartain, Nick
(2025)
The back-analysis of shear modulus reduction with strain in weathered mudstone beneath an instrumented embankment.
Earthworks 2025: Proceedings of the 4th Biennial Conference of the British Geotechnical Association, University of Birmingham, Birmingham, United Kingdom.
15 - 18 Sep 2025.
7 pp
.
Record type:
Conference or Workshop Item
(Paper)
Abstract
Full-scale earthworks trials were undertaken in advance of the construction of the High Speed 2 (HS2) railway between London and the West Midlands. They provided in-situ measurements of the ground response due to loading and unloading from the overlying earthworks. Results from the trials were used by HS2 Ltd to refine the design parameters, make cost savings and eliminate the need for engineering interventions to control ground movement. However, the instrumented trials also provided more fundamental information about the engineering properties of the ground. This is particularly useful in difficult ground such as weathered mudstone.
This paper presents results from back-analyses of in-situ measurements at an embankment trial, 14 km north of Banbury, to measure the stiffness of the underlying, weathered mudstone.
Geophysical shear wave velocity measurements were undertaken to determine the in-situ shear modulus at very small strain. These showed that the shear modulus of the ground profile increased linearly with depth in the clay, consistent with empirical equations. During well-defined construction loading stages, measurements were obtained from extensometers installed beneath the embankment. These were used to measure deformation and strains within the underlying ground profile and calculate the in-situ shear modulus. The shear modulus was normalised to compare with empirical equations for shear modulus reduction with strain. The results showed that the gradient of the normalised, non-linear stiffness of the clays was comparable with those measured in laboratory tests of fine-grained soils, at a range of strains. However, the values for the reference strain (where the maximum shear modulus reduces by 50%) were lower than was predicted by the empirical equations.
Text
Earthworks 2025_BRIGGSetal_final_June2025
- Accepted Manuscript
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Published date: 15 September 2025
Venue - Dates:
Earthworks 2025: Proceedings of the 4th Biennial Conference of the British Geotechnical Association, University of Birmingham, Birmingham, United Kingdom, 2025-09-15 - 2025-09-18
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Local EPrints ID: 508632
URI: http://eprints.soton.ac.uk/id/eprint/508632
PURE UUID: 93673dec-287a-4d18-8e32-3d640d538789
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Date deposited: 28 Jan 2026 17:55
Last modified: 29 Jan 2026 03:24
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Contributors
Author:
Kevin Briggs
Author:
Yuderka Trinidad González
Author:
Gerrit J. Meijer
Author:
Simon Butler
Author:
Nick Sartain
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