Rate effects in fine grained soils
Lead Research Organisation:
University of Dundee
Department Name: Civil Engineering
Abstract
Soils display strain rate dependant behaviour which has implications for the understanding of a wide range of geotechnical events. However, the current understanding of the results of varying strain rate on soil behaviour are often ignored in design, field studies, laboratory testing and soil mechanics frameworks. Where previous work to understand rate effects has been undertaken it focuses on relatively low strain rates or narrow ranges of strain rates that do not reflect the rates of field events. In addition several field testing techniques rely on the evaluation of rate effects for analysis. These parameters are often derived from costly field studies or specialised laboratory testing. It is the intention through this proposal to examine the behaviour of fine grained soils over a wide range of strain rates whilst varying soil composition. This approach will identify both behaviour at key strain rates and allow understanding of what the main controlling factors are at soil micro structural level. This will be achieved through the use of high speed monotonic triaxial testing with on-sample strain and pore pressure measurement. In parallel the soils will be characterised using simple standardised laboratory testing techniques. The high strain rate testing and standard testing will then be compared to develop a predictive framework which will allow the determination of soil rate potential from standardised laboratory tests without the need for specialised testing or empirical studies. This research study will lead to improved understanding of what soil properties influence rate effect potential and how to quantify them which will be exploitable by academics and industry alike.
Publications
Brown M
(2012)
Comparison of rapid load pile testing of driven and CFA piles installed in high OCR clay
in Soils and Foundations
Brown M
(2013)
Comparison of Rapid Load Test Analysis Techniques in Clay Soils
in Journal of Geotechnical and Geoenvironmental Engineering
Robinson S
(2013)
Factors influencing rate effects in fine grained soils
Brown MJ
(2016)
Design methods based upon rapid load tests
Robinson Scott
(2019)
Rate effect behaviour of different clays from high speed triaxial element testing
Description | The project looked at the behaviour of fine grained soils subject to shearing at high strain rates and the material controls on this behaviour. The significant effects of a wide strain rates on soil shear strength and small strain behaviour were reported for different soils. The influence of clay type was also examined. |
Exploitation Route | Many construction processes occur at relatively high speeds but historically these rate dependent effects have been ignored with design and construction processes effectively treated as static. The project highlights the need for construction approaches to account for these effects and offers advice on how such effects can be considered and incorporated. The research can be used by academics to improve constitutive models in numerical modelling of soil behaviour and construction processes. The work also allows academics and industrial parties involved in soil installation processes to predict the rate effects and improve how they take account of this. This may lead to improved design and understanding of variable rate installation processes. |
Sectors | Construction |
Description | CEN/TC 341/WG 7: Non-static tests on piles, Working group convenor |
Geographic Reach | Multiple continents/international |
Policy Influence Type | Membership of a guideline committee |
Description | Rate Effects in Fine Grained Soils |
Amount | £60,000 (GBP) |
Organisation | University of Dundee |
Sector | Academic/University |
Country | United Kingdom |
Start | 08/2011 |
End | 09/2014 |
Description | Rate Effects in Fine Grained Soils- Equipment funding |
Amount | £5,000 (GBP) |
Organisation | Institution of Civil Engineers |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 04/2013 |
End | 05/2014 |
Description | Rate Effects in Fine Grained Soils- Equipment funding |
Amount | £5,000 (GBP) |
Organisation | Institution of Civil Engineers |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 01/2013 |
End | 09/2014 |
Description | BRE |
Organisation | Building Research Establishment |
Country | United Kingdom |
Sector | Private |
PI Contribution | Expertise and intellectual input to BRE research project on the Rapid Load Testing of piles including scoping of testing and analysis of results from tests. |
Collaborator Contribution | Access to field obtained soil samples to enhance the scope of the laboratory testing. |
Impact | Working with BRE contributed to Dr Michael Brown being chosen as the UK representative on ISSMGE Technial Committee TC212: Deep Foundations and CEN/TC 341/WG 7: Non-static tests on piles which is charged with drafting execution codes for inclusion in Eurocode 7. |
Start Year | 2007 |