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Title: High strain rate properties of geological materials
Author: Braithwaite, Christopher Henry
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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The dynamic response of various geological materials has been investigated through a series of plate impact experiments. The materials involved were supplied from various mines by De Beers and Rio Tinto and were generically termed: sandstone, scilified siltstone, kimberlite, quartz/feldspathic gneiss, biotite schist, amphibolite, amphibolitic gneiss, basalt and iron ore. Investigations into compressional, shear and tensional behaviour were carried out. This project was part of a larger international study to develop models for the explosive loading of rock in a mining environment. This model is known as the Hybrid Stress Blasting Model, or HSBM. For this model to be accurate and relevant to the mining process it is essential to have dynamic data on the various rock types concerned. This was the purpose of the current project. As the material data are destined for use in a computer modelling programme it was essential to attempt to develop prediction methodologies to avoid the need for expensive dynamic characterisation of any new materials encountered in the mining environment. Much of the static data provided with the materials from De Beers proved of little use in predicting behaviour, although crucially it was not possible to determine sufficient dynamic tensile strengths in this investigation to make comparisons with the De Beers data. More success was found in predicting the slope of the Hugoniot with the elastic impedance of the material (for the non-porous linear Hugoniot materials). A fairly strong trend was found, which was backed up with data from the literature. Additionally some effort at further analysis using mineral data was undertaken. Attempts at predicting the HEL were also partially successful. While no specific quantitative prediction method was found, it was noted that the HEL did seem to scale with grain size, in that the large grained materials had a lower value of the HEL (below 2 GPa) compared with the finer grained materials (around 4 GPa and above).
Supervisor: Proud, William Sponsor: De Beers ; Pilbara Iron Company (a subsidiary of Rio Tinto)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Geological Materials ; Shock physics ; Mechanical Properties