Dynamic mechanical and failure behaviour of some limestones
摘要
As an engineering material, rocks can be exposed to high-rate stress during engineering processes such as drilling and blasting. Engineering structures such as tunnels and mines may require estimating the strength behavior of rock under dynamic loads for safety and optimization purposes. The relationship between the mechanical behavior of rocks and high strain rates needs to be studied in detail for specific rock types. In this paper, three different limestone samples have been loaded under uniaxial loading via a Split Hopkinson Pressure Bar (SHPB) apparatus for characterizing them in the 60–700 s− 1 strain rate range, which is the common range for impact and blasting type of events. Characteristics of the different behaviors and their threshold values, as well as strain rate relations with input energy density, failure strain, and failure energy accompanied by fragmentation studies, have been analyzed. It has been found that the high-strain-rate strength of limestone types investigated is higher than their respective quasi-static compressive strengths. At higher strain rates, although the correlation between compressive strength and strain rate is observed to be low, the failure strain and failure energy tend to increase with increasing strain rate. Behavior changes have been observed after reaching a specific value of input energy density and failure energy. The power regression relations between fragment size and strain rate have also been found in this study. Results of this study can be used to analyse the performances of percussive drilling and blasting applications and other mechanical excavations in dynamic deformation conditions.