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Title: Strain-rate effects in quartz sand
Author: Barr, A. D.
ISNI:       0000 0004 6058 5434
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Soil-filled wire and geotextile gabions are commonly used to construct defensive infrastructure in military bases, where the attenuating properties of soil are used to protect personnel and key assets from the effects of blast and fragmentation. The behaviour of soils in these extreme loading regimes is not well understood, and so designers require data at these high pressures and strain rates in order to develop robust soil constitutive models and adapt to new threats. The one-dimensional compression of three sandy soils was compared under quasi-static loading to axial stresses of 800 MPa. Trends in behaviour were identified with respect to the particle size distributions of the soils, and were found to correspond to the relationships observed at lower stresses. Split Hopkinson pressure bar (SHPB) experiments were used to investigate the strain rate dependence of this behaviour. Measurements of radial stress indicated that an increase in the axial stiffness of the soils between strain rates of 10^-3 s^-1 and 10^3 s^-1 was likely due to radial inertial effects. Potential sources of error were identified in the SHPB experiments, leading to the implementation of a dispersion-correction algorithm, which improved the measurement of axial stresses. Analysis of the electromagnetic activity around the specimen isolated the cause of erroneous radial stress measurements. Quasi-static experiments were used to investigate the effect of moisture content on soil stiffness at high pressures, and SHPB experiments at the same moisture contents were used to consider the effect of strain rate on the quasi-static behaviour. Recovery SHPB experiments were designed to enable reliable post-test particle size analyses to be performed, and the range of moisture contents was expanded to investigate the change in soil behaviour on reaching full saturation. Reduced triaxial compression experiments were used to define the yield surface of a sand to a mean stress of 400 MPa. The high-pressure compression and yield strength data was used to calibrate LS-DYNA soil models, and the performance of the models was assessed through modelling of the SHPB experiments.
Supervisor: Clarke, S. D. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available