Liquefaction Settlements in Stratified Soils

Soil liquefaction is often one of the major sources of damage from earthquakes. Liquefaction is predominantly a problem of saturated sandy soils. In particular, structures founded on liquefiable soils may undergo large settlements and tilts that can render the structure unusable in the event of an earthquake. Homes can become uninhabitable and key lifelines such as bridges can become impassable, hindering the recovery process and causing heavy economic losses. In terms of timescale, these settlements can occur both during the earthquake and during the long period following shaking, when the soil retains high pore water pressures and remains in a softened liquefied state until the fluid can fully dissipate. While a large body of work is accumulating on the behaviour of liquefiable soils and its remediation, the effects of low-permeability layers within the soil mass have more recently been identified as a problem comprising unique behaviour. This project aims to examine specifically the role of such stratifications on building settlement / the important variable from a practical viewpoint / as well as provide detailed information on the pore pressure regime within the soils which is important for understanding the timescales of the settlements. This will be achieved through dynamic centrifuge modelling using the new centrifuge earthquake shaker at Dundee University. Based on this, the relative importance of the factors in the soil stratigraphy, such as layer thickness and the number of layers, can be quantified to enable the informed identification of problematic and non-problematic sites. In addition, the existing scientific knowledge concerning the behaviour of such soils and the associated fluid-particle behaviour will be extended, with particular reference to the phenomena of water films and sand boils. The philosophy will be to balance practical useable results with enhanced knowledge of the underlying science.