不同含水状态砂岩的单轴循环荷载微观损伤机制研究

Study on microscopic damage mechanism of sandstone under uniaxial cyclic loading in different water-bearing states

为探究不同含水状态的岩石循环加卸载条件下的微观损伤机制,该文以砂岩为研究对象,运用MTS815试验机开展4种含水率,3种频率条件下的岩石单轴循环加卸载试验。结果表明:岩石的横向损伤发生主要集中在每个应力水平阶段的前10个周次,其中第1周次导致岩石横向产生最大损伤。含水率对岩石的横向累计不可逆应变的影响比应力水平大。同一含水状态下,加卸载频率越高,岩石的扩容点提前。揭示含水状态下的岩石在循环加卸载条件下的微裂纹扩展机制:裂纹空间在低应力水平循环荷载条件下,产生空间塌缩,体积减小,填充水充满了裂纹空间;随着循环应力水平的不断加大,裂纹内部填充水受到挤压,产生超孔隙水压力,向裂纹两端施压,导致裂纹两端的开展。循环加卸载对裂纹扩展起到主导作用,水的存在对裂纹扩展起到辅助作用。研究成果对富水地区的岩质边坡防护工程技术具有参考价值。

To explore the microscopic damage mechanism of rock under cyclic loading and unloading conditions with different water contents,this paper takes sandstone as the research object and conducts uniaxial cyclic loading and unloading tests with MTS815 testing machine under four water content and three frequency contents.The results show that the transverse damage of rock is mainly concentrated in the first 10 cycles of each stress level stage,and the first cycle leads to the maximum transverse damage of rock.The influence of water content on the lateral cumulative irreversible strain of rock is greater than that of stress level.Under the same water condition,the higher the loading and unloading frequency,the earlier the rock expansion point.The micro-crack propagation mechanism of rock under a water-bearing state under cyclic loading and unloading conditions was revealed.Under low-stress level cyclic loading conditions,the crack space collapsed,the volume decreased,and the fillng water filled the crack space.With the increasing level of cyclic stress,the filling water inside the crack is squeezed,resulting in excess pore water pressure,which is applied to both ends of the crack,leading to the development of both ends of the crack.Cyclic loading and unloading plays a leading role in crack propagation,and the existence of water plays an auxiliary role in crack propagation.The research results have reference value for rock slope protection engineering technology in water-rich areas.