The variation of large strain viscous rate effects from undrained triaxial element testing of Kaolin clay

TY - JOUR

T1 - The variation of large strain viscous rate effects from undrained triaxial element testing of Kaolin clay

AU - Robinson, Scott

AU - Brown, Michael

AU - Knappett, Jonathan

AU - Brennan, Andrew

AU - Arroyo, Marcos

AU - Duran Caballero, Diego

N1 - Publisher Copyright: © The Author(s) 2025.

PY - 2025/10/22

Y1 - 2025/10/22

N2 - Viscous (undrained) rate effects lead to an increase in the shear strength of fine-grained soils such as clays when sheared at high strain rates. Correct rate effect parameters are key to accurate predictions of behaviour in a range of geotechnical applications, from subsea cable ploughing and rapid load testing of piles through to numerical modelling of offshore foundation systems. The factors influencing the magnitude of rate effects are, however, still poorly understood. Through a series of 100 mm diameter high-speed undrained triaxial tests (strain rates ranging from 300 to 180,000 %/hr and initial effective stresses from 300 to 1350 kPa) on Kaolin clay, this paper investigates the influence of the soil state and stress history on rate effects across a wide strain range. Viscous rate effects ranging from 10 to 16 % per log cycle are observed, and the liquidity index is observed to correlate to the magnitude of the rate effects. Viscous rate effects are also shown to reduce with increasing strain level, and a model is proposed which allows the rate effect in Kaolin to be predicted accounting for both of these factors. This model is potentially useful in analytical and numerical studies.

AB - Viscous (undrained) rate effects lead to an increase in the shear strength of fine-grained soils such as clays when sheared at high strain rates. Correct rate effect parameters are key to accurate predictions of behaviour in a range of geotechnical applications, from subsea cable ploughing and rapid load testing of piles through to numerical modelling of offshore foundation systems. The factors influencing the magnitude of rate effects are, however, still poorly understood. Through a series of 100 mm diameter high-speed undrained triaxial tests (strain rates ranging from 300 to 180,000 %/hr and initial effective stresses from 300 to 1350 kPa) on Kaolin clay, this paper investigates the influence of the soil state and stress history on rate effects across a wide strain range. Viscous rate effects ranging from 10 to 16 % per log cycle are observed, and the liquidity index is observed to correlate to the magnitude of the rate effects. Viscous rate effects are also shown to reduce with increasing strain level, and a model is proposed which allows the rate effect in Kaolin to be predicted accounting for both of these factors. This model is potentially useful in analytical and numerical studies.

KW - Rate effects

KW - Viscous effect

KW - Kaolin clay

KW - Triaxial test

KW - high speed triaxial

KW - Clay

KW - Liquidity index

KW - Strain level

KW - Strain-rate

KW - Viscous rate effects

KW - Triaxial testing

UR - https://www.scopus.com/pages/publications/105019573353

U2 - 10.1007/s11440-025-02797-3

DO - 10.1007/s11440-025-02797-3

M3 - Article

SN - 1861-1125

JO - Acta Geotechnica

JF - Acta Geotechnica

ER -