Blast and Impact Dynamics

Department of Civil & Structural Engineering

Strain-rate effects in quartz sand

Sand

Details

Soil-filled wire and geotextile gabions are commonly used to construct perimeter walls and other defensive infrastructure in military bases. They serve to protect personnel and key assets from the effects of blast and fragmentation. The attenuating properties of soil make it a highly effective defence against such threats, and as it is readily available in most locations, large structures can be erected at relatively low cost. However, ‘soil’ is an incredibly variable material, and its high-strain-rate behaviour is not well understood. In order to develop robust constitutive models to adapt to new soils and new threats, fortifications designers require high-pressure data on the behaviour of soils over a wide range of strain rates and ground conditions.

This project considered the effects of strain rate on the behaviour of a variety of sandy soils using quasi-static uniaxial strain tests to 800 MPa, alongside high-strain-rate experiments using a split-Hopkinson pressure bar. The sensitivity of this effect to changes in moisture content was also investigated, and recovery experiments were used to assess particle breakage. The high-pressure data was used to characterise the compressibility and yield surface of a soil to over 800 MPa, greatly improving the soil data available to numerical modellers. A dispersion-correction algorithm was also implemented to improve the accuracy of stress measurements in the split Hopkinson pressure bar experiments.

Sponsor

EPSRC CASE Studentship with support from Blastech

Software

dispersion.m - A MatLab script for phase angle and amplitude correction of pressure bar signals

In processing the signals from split Hopkinson pressure bar (SHPB) experiments it is often assumed that longitudinal stress waves in the pressure bars propagate one-dimensionally at a common velocity c_0, and so measurements taken at the strain gauges are often simply translated to the end of the bar using a...