Dawn T. Nicholson and Frank H. Nicholson
Ten sedimentary rocks were subjected to repeated cycles of freezing and thawing. In addition to monitoring sample weight loss and fracture density throughout testing, a detailed graphic record was made of deterioration mode and its relationship to pre-existing rock flaws. Results suggest that the presence or absence of rock flaws alone does not control deterioration mode, but rather, that it is the coupled relationship between these flaws, and rock strength and textural properties which exerts greatest influence.
While some pre-existing flaws such as syn-depositional deformation structures do not appear to influence breakdown, others, such as incipient discontinuities, cavities and minor lithological boundaries frequently coincide with concentrations of deterioration. Characteristic modes of deterioration which are independent of pre-existing flaws tend to develop in sandstone, an indication of the influence, in this case, of rock texture. Particularly strong rocks such as crystalline limestone and metasediment tend to fracture preferentially along distinct linear weaknesses such as mineral veins, stylolites and incipient discontinuities. Particularly weak rocks such as low density chalk breakdown in a random fashion without regard to pre-existing flaws.
In addition to providing some insight into the role of pre-existing flaws in rock deterioration, this work also has practical implications for (i) the selection of representative rock samples in durability testing for building stone, and (ii) for the evaluation of rockslope deterioration.