The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering. Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles. The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system. The results indicate that the tensile strength is observably reduced after cyclic wetting-drying, and the extent of the reduction is not only related to the number of wetting-drying cycle, but also closely related to the clay mineral content of the sample. In addition, as the cycles of wetting-drying increase, the effect of each single cycle on tensile strength get reduced until it becomes constant. Moreover, the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases, which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone. Meanwhile, the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle. Furthermore, through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles, it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction, chemical and corrosive deterioration.

对循环湿润干燥后岩石抗张强度减弱机制的理解对于岩石工程至关重要。在总共35个具有不同干湿循环的砂岩样品上进行了拉伸强度测试。测试样品的裂纹扩展过程和声发射特性是通过高速摄像头和声发射系统获得的。结果表明，循环润湿干燥后抗拉强度明显降低，降低的程度不仅与润湿干燥循环次数有关，而且与样品中粘土矿物含量密切相关。另外，随着干湿循环的增加，每个单一循环对拉伸强度的影响减小，直到变得恒定为止。此外，随着干湿循环次数的增加，裂纹的萌生和渗透时间延长，这表明干湿循环削弱了岩石的刚度，增强了砂岩的延展性。同时，测试样品的声发射特性进一步证实了随着干湿循环的增加，砂岩样品的延性。此外，通过对不同干湿循环样品的微观结构和矿物组成的分析，可以得出结论，含粘土矿物的砂岩的主要弱化机理是摩擦还原，化学腐蚀和腐蚀劣化。同时，测试样品的声发射特性进一步证实了随着干湿循环的增加，砂岩样品的延性。此外，通过对不同干湿循环样品的微观结构和矿物组成的分析，可以得出结论，含粘土矿物的砂岩的主要弱化机理是摩擦还原，化学腐蚀和腐蚀劣化。同时，测试样品的声发射特性进一步证实了随着干湿循环的增加，砂岩样品的延性。此外，通过对不同干湿循环样品的微观结构和矿物组成的分析，可以得出结论，含粘土矿物的砂岩的主要弱化机理是摩擦还原，化学腐蚀和腐蚀劣化。