关键词: 薄层岩体, 抗弯性能, 破裂模式, 拉伸模量, 三点弯曲试验

Abstract: Bending failures are common phenomena in thin-bedded rock mass during underground construction. In order to investigate deformation feature and failure process of rock under bending conditions, three-point bending tests were conducted on single-layer limestone samples and bedded specimens with weak planes. Our results illustrate that a close relationship exists between flexural capacity of the specimen and bed thickness, and the variations of the peak moment per width and the deflection at the peak force with specimen thickness can be reasonably predicted by the beam theory. It is shown that various fracture modes appear during testing, including mode I cracks perpendicular to bedding, zigzag cracks with changing direction at interfaces(weak planes), and oblique cracks across bedding. Theoretically, crack paths in thin-bedded rock mass are mainly controlled by the relative magnitudes of strengths (or fracture toughness) between rocks and interfaces. Tensile modulus is obtained by iteratively using the double modulus theory. Iteration process converges relatively slowly when the difference between compressive and tensile moduli is significant. These findings prove to be helpful in understanding the deformation characteristics and failure mechanisms of thin-bedded rock masses under bending conditions.

Key words: thin-bedded rock mass, flexural behavior, fracture mode, tensile modulus, three-point bending test