Influence of heating/cooling cycles on the micro/macrocracking characteristics of Rucheng granite under unconfined compression

• Published in: Bulletin of engineering geology and the environment 2020-04, Vol.79 (3), p.1289-1309
• Main Authors: Weng, Lei, Wu, Zhijun, Liu, Quansheng
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-019-01638-4

This study experimentally investigates the influence of heating/cooling cycles on the mechanical properties and cracking features of Rucheng granite. The specimens, which were previously subjected to various numbers of heating (350 °C) and cooling (in 21 °C tap water) cycles, were tested under unconfined compression. Integrated acoustic emission (AE) and digital image correlation (DIC) techniques were used to study the micro/macrocracking characteristics of the specimens upon different heating/cooling cycles. The changes in the amount of surface cracks and microcracks, P-wave velocity, unconfined compressive strength (UCS), elastic modulus, and Poisson’s ratio of the specimens prior to and after various heating/cooling cycles were comprehensively analyzed. The results showed that as the number of heating/cooling cycles increased, more surface cracks and internal microcracks (including intergranular and intragranular) were observed, leading to more remarkable decreases in P-wave velocity and substantial loss of the strength and stiffness. The change in the P-wave velocity is more sensitive than the UCS upon the cyclic heating/cooling treatments. An increase in the cycle number yielded an increase in the brittleness and a decrease in the ductility with respect to the stress-strain response. Furthermore, after exposure to a greater number of heating/cooling treatment cycles, the onset of unstable crack propagation will initiate at a lower stress threshold, while the postpeak softening response becomes more prominent. In addition, the failure mode changes from a typical shear failure to an axial splitting fashion as the number of heating/cooling cycles increases.