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Granular and Geological Materials

The Research

In recent years the group has conducted a significant amount of research concerning geological and granular materials. This has looked at many different materials including:

  • Fully dense and porous rock
  • Sands and soils
  • Concrete
  • Ceramics
  • Pressed metal powders
  • Metallic and polymer foams
  • Porous energetic materials

Much of this research involved measuring the response of these materials to quasi-static, dynamic and shock loading.

Geological and granular materials are important for many applications and most of this work has been done in collaboration with researchers from the mining, defence and aerospace sectors.

The group has investigated shock compaction in many porous materials. This research involved plate impact experiments to measure the Hugoniot and release of these porous materials and using shock compaction models to describe the behaviour. The group has also looked at the effect of grain size, morphology and moisture on the shock compaction.

Recent research has investigated the fracture and fragmentation of geological materials under dynamic and shock loading though brazilian disc and explosively driven expanding ring experiments. These experiments included the use of high speed photography to observe crack growth , fragment size analysis and fractography of the samples post-experiment.

The group is also interested in wave propagation in granular materials. The non-linear mechanical nature of grain contacts results in granular materials having significantly lower sound speeds compared to fully dense materials. This phenomenon has been investigated through sound speed measurements and high speed photography on real granular materials, like sand, and idealised systems such as chains of identical spheres.

Research has also looked at ballistic penetration into sand and concrete. In these experiments a flash X-ray system and digital image correlation was used to observe flow within the material during penetration.

The People

Current researchers in this field include Simon Kirk who is completing a PhD sponsored by Orica and James Perry who is sponsored by QinetiQ. Dr. Chris Braithwaite also retains a strong interest in this are having completed a PhD sponsored by De Beers.

The Impact