Uniaxial compressive strength measurements of limestone plugs and cores: a size comparison and X-ray CT study

Abstract

In many geo-engineering fields, the uniaxial compressive strength (UCS) of a rock material is the parameter most commonly used to define a rock’s mechanical strength. Several international standards have been developed for determining this value, which require the tested material to have certain minimum dimensions and shapes. In many applications, however, sample material is limited. Therefore, this study investigates the possibility of determining the UCS on rock plugs smaller than the minimum dimensions in the most common standards. The materials investigated are four different depositional limestones from the Paris Basin which are often used as building material in France and Belgium. Results from UCS tests in a small-scale uniaxial compressive device are compared to standard-sized tests according to the governing international standards. The results show that the strength determined on the small-scale plugs is very similar to the UCS determined on standard-sized cores. Using high-resolution X-ray computed tomography, it was possible to investigate the failure modes of the small-scale plugs and link them to their internal rock fabric. Obtaining a three-dimensional visualization provides valuable insights into the origin of the variability in the UCS measurements in small-scale plugs.