UNDERSTANDING RATE EFFECTS IN GEOMATERIALS

Supervisor: Dr Sam Clarke

Joint Supervisor: Dr Mihail Petkovski

Concrete is often used as a material of choice when designing civilian systems to withstand the effect of explosions or high velocity projectiles, such as might be generated by the detonation of a terrorist vehicle bomb. For military defence purposes, especially in impromptu defensive structures, other geomaterials such as sand may be used, the classic example being the sand-bag wall. Both these types of geomaterials share the common property that the way they respond to loading is dependent on the lateral confining pressure applied to the material. Put simply, the higher the lateral confining pressure, the greater the strength of the material. Under extremely high magnitude, very rapid loading, the lateral inertia of the material may apply some degree of confinement, and correctly quantifying this can be crucial in allowing designers to properly determine the resistance of a protective system. The situation is further complicated by the fact that the materials behaviour may be different at static and rapid dynamic rates of loading.

There is thus a pressing requirement on materials researchers to identify how geomaterials respond under differing lateral confinement conditions, and hence, develop material models which can be used by computational modellers to predict response to intense transient loading. The Civil & Structural Engineering Department at UoS has an excellent combination of expertise and facilities for the study of this problem, including the world-leading Mac2t triaxial material testing rig, which can apply highly controlled multi-axial stress conditions to geomaterials at quasi-static loading rates, the Buxton blast & impact laboratory which can conduct high-rate confined tests, and strong geotechnical and concrete materials research groups.

The purpose of this project will be to conduct experimental work to identify:

*The triaxial behaviour of different geomaterials at a range of loading rates and

*The parameters which affect the geomaterials sensitivity to loading rate

The outcome of this work will be well validated material models which can be used in computational analysis models to predict the response of protection systems to intense transient loading.