Fracture patterns in deep-textured shales play a pivotal role in determining the structural stability of engineering constructions and optimizing energy utilization. This study utilizes a numerical model of a semicircular bending (SCB) specimen developed through the finite discrete element method to unveil the mixed fracture mechanical characteristics inherent in deep-textured shales. The investigation delves into the influence of prefabricated crack inclination, texture inclination, and texture strength on mixed fracture toughness, with the specimen’s damage process elucidated by analyzing the evolution of the acoustic emission distribution. The findings disclose the following insights: (1) An increase in the inclination of the texture leads to a concomitant rise in the tortuosity and length of the crack, followed by subsequent decreases. Elevating the inclination of the prefabricated crack reduces the requisite load force for specimen damage and significantly mitigates crack deflection. (2) Textured shale specimens manifest four distinct damage modes: penetrating extension, deflection extension, tangential extension, and mixed extension. The reduction in texture strength amplifies the probability of mixed extension and concurrently augments the shear damage rate of the specimen. (3) Mixed fracture toughness displays a linear decrease with crack inclination and a linear increase with texture strength. (4) The toughening mechanism of textured shales is categorized into three classes: separation along the texture, fracture path deflection, and texture cracking. The preeminent controlling effects on toughening mechanisms, in descending order of strength, are texture strength > texture inclination > prefabricated crack inclination.