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Project
The constitutive behaviour of granular soils under repeated dynamic loading
The aim of this project is to develop an advanced numerical method for the calculation of the dynamic behavior of granular soils under repeated small amplitude dynamic loading. This allows to study long term effects of vibrations on structures, as arising from road and railway traffic or construction activities. Under this repeated dynamic loading, the soil behaves (almost) elastically on the short term, whereas a non-negligible plastic behavior is observed over a large number of load cycles. This phenomenon is referred to as strain accumulation, since plastic deformations accumulate in very small increments per load cycle. Strain accumulation is attributed to rearrangement of grains, drainage effects, and abrasion of soil particles.
A phenomenological approach is commonly followed, where observations made in cyclic tri-axial tests are cast into constitutive laws. Phenomenological models often only give satisfactory results for the range of stress paths for which they have been developed. Models attempting to represent a wider range of phenomena must incorporate a large number of parameters. In most cases, these parameters lack physical meaning and are difficult to determine.
As an alternative to phenomenological models, a micro-mechanical approach to the analysis of granular soils can be followed. The incorporation of information at the particle scale only requires physical properties of particles and their interactions, as opposed to poorly understood model parameters in a phenomenological approach. This should result in a more profound understanding of the underlying physical processes and a better prediction of the behavior of sands under repeated dynamic loading. A homogenization approach is followed to tackle foundation settlement problems at the macro scale.
The development of these innovative constitutive models is supported by laboratory tests, focusing on both the micro and macro mechanical scales. For this purpose, a cyclic tri-axial test where bender elements can be incorporated is available.
A phenomenological approach is commonly followed, where observations made in cyclic tri-axial tests are cast into constitutive laws. Phenomenological models often only give satisfactory results for the range of stress paths for which they have been developed. Models attempting to represent a wider range of phenomena must incorporate a large number of parameters. In most cases, these parameters lack physical meaning and are difficult to determine.
As an alternative to phenomenological models, a micro-mechanical approach to the analysis of granular soils can be followed. The incorporation of information at the particle scale only requires physical properties of particles and their interactions, as opposed to poorly understood model parameters in a phenomenological approach. This should result in a more profound understanding of the underlying physical processes and a better prediction of the behavior of sands under repeated dynamic loading. A homogenization approach is followed to tackle foundation settlement problems at the macro scale.
The development of these innovative constitutive models is supported by laboratory tests, focusing on both the micro and macro mechanical scales. For this purpose, a cyclic tri-axial test where bender elements can be incorporated is available.
Date:1 Oct 2009 → 31 Dec 2011
Keywords:Dynamic loading, Granular soils
Disciplines:Structural engineering, Other civil and building engineering
Project type:PhD project