Enhancing Infrastructure Resilience Through Technology: A Study on Fracture and Damage Evolution in Beishan Granite Under Cyclic Loading

The fracture behavior of Beishan granite is a critical scientific basis for evaluating and ensuring the long-term safety of geological repositories for high-level radioactive waste under extreme thermal–mechanical conditions. With increasing emphasis on climate-resilient infrastructure, understanding the mechanical response of deep geological materials under cyclic loading and simulating long-term environmental conditions are essential for sustainable engineering management. Previous studies have predominantly concentrated on the fracture characteristics under static loading tests, with limited research conducted on the characteristic parameters of acoustic emission (AE) during cyclic loading and the morphology of fractures post-failure. Contributing to the field of resilient infrastructure, this paper presents static and cyclic loading tests using MTS815 equipment on Beishan deep granite (CCNBD type). To determine the rock fracture toughness of mode I and fracture roughness, static loading and cyclic loading tests were conducted using MTS815 equipment with Beishan deep granite (CCNBD type) as the subject of study. AE and 3D laser scanning were employed to acquire the characteristic parameters of acoustic emission (AE) during loading and the morphology of fracture surfaces after failure in the specimens. The results revealed that CCNBD specimens demonstrated pronounced brittle tensile failure under static and cyclic loading conditions. The rock fracture toughness obtained in static tests was 1.180 MPa·m1/2, whereas under cyclic loading, it was 1.153 MPa·m1/2. In comparison to static loading, cyclic loading led to a greater accumulation of microcracks inside the specimens, resulting in a 9.8% increase in the length of the fracture process zone. A 57.5% increase in section roughness (fractal dimension) was observed after the failure of the specimen in comparison to static loading.