Adhesion in Rock
Final rept. 1 Feb-31 Dec 1971
BUREAU OF MINES TWIN CITIES MN TWIN CITIES MINING RESEARCH CENTER
Pagination or Media Count:
A direct method has been developed for estimating the strength of intergranular adhesion in rock. It involves the separation of a bicrystal from the rock and a determination of the tensile strength at the solid-solid interface. This technique has been successfully applied to the study of quartz- feldspar interfaces separated from pegmatites, graphic granite, and the Rockville granite yielding average tensile strengths of 5.86, 8.62, and 10.65 MNmsq 850, 1,250, and 1,524 psi respectively. The data generated by this technique indicate that the members of these bicrystals are strongly adhernet. Examination of bicrystals broken at the crystalline interfaces indicates that the bonds responsible for this adhesion operate only over a portion of the interfacial area. The significance of this work is that it demonstrates that tensile strength tests can be conducted on small selected areas, e.g. grain boundaries in rock. This permits a determination of small scale zones of strength or weakness which may be related to the overall strength of the rock. Selected area microindentation hardness testing has also been performed to probe hardness variations near phase boundaries.
- Geology, Geochemistry and Mineralogy