空隙特征对砂岩水致劣化规律的影响

针对南京秦淮东河开挖后的稳定性问题，选取黄马青组（T2h）砂岩为研究对象，对砂岩在吸水-干燥循环条件下的单轴抗压、抗拉特性进行试验研究。考虑到未来边坡运营过程中水的影响，试验时分别考虑自然吸水和饱和吸水两种情况。根据试验结果对所研究砂岩的空隙特征、水致劣化特征和劣化机制进行了详细分析。随着吸水-干燥循环次数增加，岩石的抗压、抗拉强度和凝聚力均呈劣化趋势，说明循环次数的增加对岩石的损伤有累积作用。岩石自然吸水条件下（小开空隙未进水时）强度和弹性模量下降速度较慢，而饱和吸水条件下（开空隙被水充满时）强度和弹性模量下降速度较快，表明岩石中小开空隙对岩石的劣化效果显著。微观结构分析结果表明，随着吸水-干燥循环次数增加，岩石中空隙率增大。结合抗剪强度特征分析认为，干-湿循环导致岩石的黏结强度不断下降，而摩擦强度变化较小，表明黏结强度劣化是岩石水致劣化的主要原因，干-湿循环导致水-岩反应，岩石颗粒胶结物发生松散，边缘发生开裂，宏观上表现为岩石劣化。该研究成果对于新开挖河道边坡稳定性分析具有较大的参考价值，为河岸边坡的长期稳定性分析提供了依据。

Effect of void characteristics on deteriorating rules of sandstone due to water

In this paper, the sandstones of the Huangmaqing Group (T2h) were taken as the study object. The compressive and tensile tests were carried out on the rock samples, considering the influencing factors of the slope along the Qinhuai East River in Nanjing city. Since water is the main factor that affects the stability of the excavated slope, both the natural and saturated soaking-drying cycles were taken into account during the experiments. Based on the experimental results of the sandstones, the void and deterioration characteristics and deteriorating mechanism were analyzed in detail. With the increasing number of the soaking-drying cycle, the compressive and tensile strengths, and the cohesion of the sand rock samples all gradually deteriorate. The more the cycle numbers, the more serious damage of the rock mass, which indicates that the cycles have cumulative damage on the samples. Under the natural water absorption conditions (no water entering the small open voids), the strength and modulus of the rock slowly decrease. However, under the saturated water absorption conditions (the small open voids are filled with water), the strength and modulus rapidly decrease, which indicates that the deterioration effect due to existence of the small open voids is obvious. The micro-structures indicate that the voids in the rock increase with the number of soaking-drying cycle. Combined with the shear strength characteristics results, the declination of the cohesive strength is the main factor of rock strength deterioration, and the frictional strength almost has no change. The cycles lead to the water-rock reaction, causing gradual loss of rock particle cementation and cracking of the edges, and the rock is degraded in macroscopic scale. Research results have an important reference for the study of stability of new excavation slope, and provide favorable evidences for the long-term stability analysis of river bank slopes.