探究具有不同初始损伤的软硬互层岩体的力学性质，对于评估震后损伤岩体在周期性干湿循环交替环境下的稳定性极为关键。本研究以变质砂岩和千枚岩互层岩体为研究对象，采用MTS岩石仪、声发射系统和数字图像相关技术，通过循环加卸载试验和随后的干湿循环试验，制备了具有不同初始损伤度的试样，然后开展单轴压缩试验，研究了不同初始损伤试样的变形破坏特征、裂纹演化过程、强度劣化规律，探究了试样破坏的前兆特征，并从微观角度揭示了试样的损伤劣化机制。结果表明：（1）软硬互层岩体表面的变形并不同步，千枚岩岩层的变形大于变质砂岩层，并最先出现局部高应变区，变形差异系数能够量化试样表面不同区域的变形差异，当变形差异系数由减小阶段转换为增大阶段时，表明局部裂纹发生了贯通。（2）穿晶裂纹和晶间裂纹的扩展贯穿整个加载过程，其破裂形式主要以张拉破裂为主。在塑性阶段，剪切破裂特征会变得明显，并引起RA/AF值变异系数CV的增大，当CV增加至6.5时，试样临近破坏。（3）试样的剪切破坏模式主要受岩体结构特征的控制，初始损伤则影响试样的破裂类型和裂纹的发育特征，初始损伤度越大，微裂纹数量越多，剪切破裂特征愈发显著。（4）初始损伤引起弹性模量，抗压强度和破坏位移的下降。微裂纹的增多、颗粒间胶结作用的减弱是导致岩体宏观力学性能劣化的根本原因。

Exploring the mechanical properties of soft-hard interbedded rock mass with different initial damage is crucial for assessing the stability of post-seismic damaged rock masses under cyclic drying and wetting conditions. This study focuses on the interbedded rock mass of metasandstone and phyllite, using an MTS rock testing machine, an acoustic emission system, and digital image correlation technology. Through cyclic loading and unloading tests followed by cyclic drying and wetting tests, the samples with different initial damage degrees were prepared. Subsequently, uniaxial compression tests were conducted to investigate the deformation and failure characteristics, crack evolution process, and strength degradation laws of samples with different initial damage degrees, explore the precursor information of sample failure, and reveal the damage degradation mechanism from a micro perspective. The results indicate: (1) Deformation on the surface of the soft-hard interbedded rock mass is not concurrent; the deformation of the phyllite layers exceeds that of the metasandstone layers, and the first signs of local high strain zones emerge. The deformation difference coefficient can quantify the discrepancies in deformation across different areas of the sample surface. A shift from a decreasing to an increasing deformation difference coefficient indicates that local cracks have coalesced. (2) The propagation of transcrystalline crack and intercrystalline crack extends throughout the loading process, with tensile fracturing being the primary mode of failure. During the plastic stage, shear fracturing characteristics become more evident, leading to an increase in the coefficient of variation (CV) of the RA/AF values. When the CV reaches 6.5, the sample is approaching failure. (3) The shear failure mode of the sample is primarily governed by the structural features of the rock mass, while initial damage influences the type of failure and the development of cracks. Higher initial damage degrees result in more microcracks and more pronounced shear fracturing characteristics. (4) Initial damage leads to a decrease in elastic modulus, compressive strength, and failure displacement. The increase in microcracks and the weakening of interparticle bonding are the fundamental causes of the deterioration of the rock mass's macroscopic mechanical properties.

TU452

国家自然科学基金项目(U22A20603)；国家重点研发计划项目(2023YFC3008300)