Rate effects in fine grained soils

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.