中文摘要：

鉴于薄层岩体在实际地下工程中经常发生弯折破坏,利用三点弯曲试验对单层灰岩及含弱面灰岩试样进行抗弯性能测试,探究岩层受弯作用时的变形及破坏特征。试验结果表明,薄层灰岩的抗弯性能与层厚密切相关,单宽峰值弯矩及峰值力对应的岩梁挠度随层厚变化规律基本符合材料力学理论公式计算结果。薄层灰岩弯折破裂模式呈现多样化,既有垂直切穿层理的I型裂纹,也有在弱面处发生转折并沿弱面扩展的断续裂纹,以及与层理斜交的复合型裂纹等。理论分析表明,薄层岩体中的裂纹扩展路径主要受层面拉、剪强度（或断裂韧度）与岩石抗拉强度（或断裂韧度）的相对大小控制。利用双模量理论结合弯曲试验求解岩石拉伸模量需要进行迭代计算,拉压模量相差越大,迭代次数越多,收敛值越偏离初值。试验所得规律有助于深入理解薄层岩体弯曲变形特征及弯折破坏机制,并可作为对薄层岩体受弯作用理论及数值计算的有益补充。

英文摘要：

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.