Effects of uniaxial compression on acoustic emission and damage evolution characteristics of sandstone–concrete composites containing T-shaped fissures

As a fundamental component of engineering structures such as tunnel linings and dam foundations, the mechanical performance of rock-concrete composites is significantly governed by the propagation behavior of natural cracks within the rock mass, and the associated damage evolution poses a direct threat to structural safety. This study employs the discrete element method to simulate the influence of T-shaped prefabricated sandstone cracks with varying lengths and dip angles on the mechanical behavior and damage evolution of sandstone–concrete composites, with validation through laboratory experiments. The results of the studies that the presence of prefabricated cracks significantly reduces the mechanical strength of the composites. The peak strength of intact specimens was higher than that of cracked specimens, and the axial compressive strength decreased progressively with increasing crack length and inclination angle. When the crack length increased from 10 to 20 mm, the compressive strength exhibited a nonlinear, accelerated attenuation trend, with the rate of decline positively correlated with crack length. Meanwhile, the strength showed a non-uniform variation with increasing crack inclination, and the influence of inclination angle on strength was weakened as the crack length increased. During loading, the acoustic emission (AE) signals exhibited distinct temporal characteristics. At the stage of global structural failure, the AE signal frequency dropped noticeably, while the AE amplitude reached its peak. The crack propagation trends revealed the internal damage evolution mechanisms of the specimens, with cracks ultimately forming a “pyramidal” distribution pattern concentrated around the interface and crack tips.