Loading from Shallow Buried Blast Events and the Effect on Plate Deformations

This thesis describes the design and construction of an experimental apparatus
to enable the repeatable testing of appliqué protective systems against buried
charges. This thesis highlights the difficulties in understanding and predicting
buried blast loading, as well as why it is important to know the distribution of
impulse as well as how quickly it is delivered.
A review of the literature investigating the phenomenology of buried charge
testing is presented, along with previous work which has looked into the factors
which can affect the output of a buried charge. Tests were conducted using
the developed apparatus, with the detailed output of 21 tests against varying
thicknesses of Armox 440T steel being presented within this thesis. The testing
was conducted at 1/2 scale, with charge sizes between 400 and 1000 grams,
and nominal plate thicknesses between 6 and 12 mm. For each test the full
deformation profile was provided along with dynamic (peak) and residual deflections
to enable numerical model validation. The preparation of the soil bed
for the testing has been carefully controlled based on previous experience at
the University of Sheffield. The test series used Leighton Buzzard 14/25 sand
which is a silica based uniform soil with particle sizes between 0.6–1.18 mm.
This was prepared to a moisture content of 5% and dry density of 1620 kg/m3.
Analysis of the test series was done using the Nurick and Martin (1989) analysis
method with modified correction factor based on the distribution of kinetic
energy. This analysis has shown that for the appliqué systems tested, the normalised
deflection can be predicted if the normalised total impulse as well as the
distribution of impulse imparted to the system is known; this finding should be
the basis of a fast running engineering model for plate deformation from shallow
buried blast and other non-uniform impulsive loading.