Levee stability and the evolution of ‘A’ a lava flow-fields

  • Marie Nolan

    Student thesis: Doctoral Thesis


    The capability to predict the final dimensions of an ‘a’a flow-field and the timeline for emplacement is key to effective lava hazard management. Levee breaching and the subsequent generation of secondary flows has been recognised as an intrinsic process in flow-field development. However, the conditions, locations and mechanisms for levee failure are not fully understood and so a multidisciplinary approach was taken utilising field studies of extant flow-fields on Mount Etna and Tenerife, analogue modelling and uniaxial compression tests to investigate levee failure.

    The experimental results were used to define three stages of flow-field development – lengthening, widening and thickening, a modification of the classification of Kilburn and Lopes (1991). Levee breaching was identified to be a key process by which flow-fields widen during stage two of emplacement. Four mechanisms for breaching are identified, providing a classification system for levee failure. Secondary flows originating from breaching consistently formed at an angle of 30 – 50o to the original channel, significantly contributing to overall flow-field width.

    Uniaxial compression tests were performed to quantify the mechanical properties of levees. Levee strength was shown to change with direction according to the size, orientation and distribution of vesicles. Samples with vesicle alignment orientated obliquely to the angle of principal stress were consistently weaker. A set of conditions, relating to the mechanical properties of the levee, is therefore identified under which levees are more susceptible to failure.

    The results of the study have been combined to produce a set of guidelines to the locations and conditions under which levee breaching is more likely to occur, aiding decision making for lava hazard management.
    Date of AwardApr 2014
    Original languageEnglish
    Awarding Institution
    • University of Portsmouth
    SupervisorCarmen Solana (Supervisor) & Christopher R. J. Kilburn (Supervisor)

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