水-岩作用下砂岩声发射与红外辐射耦合研究

Coupling Study of Acoustic Emission and Infrared Radiation in Sandstone under Water-Rock Interaction

为探究水-岩作用下的砂岩破裂变形机制,开展天然与饱水砂岩单轴压缩声发射实验与红外辐射观测实验,通过对各变形阶段的轴向应力、声发射能率、分形维数以及红外辐射频数直方图与偏度共同分析了水对砂岩力学性质、声发射以及红外辐射变化的影响。研究结果表明:水对岩石的抗压强度、承载能力等力学性质有明显弱化作用;水抑制了岩石的声发射活动以及裂纹发育规模,天然试样的平均峰值能率、能率释放活跃阶段的持续时间以及幅度均大于饱水试样,能率与应力同步性较饱水试样好;两类岩石声发射能率的关联维数均为升-降-升-降的变化规律,饱水试样声发射对裂隙离散无序发育以及聚集有序发育的响应时间均较天然试样晚,能率的释放较天然试样呈现更高的无序性;水增强了红外辐射的敏感性,饱水试样受载过程中升温区域逐渐增大,破坏时表现为岩石表面大面积升温,天然试样受载过程中温度变化幅度小且不稳定,破坏时表现为出现少数高温异常点,两类岩石峰值应力前均出现温度变化平静期。研究成果可为岩石灾变时地球物理信号响应机制提供理论参考。

The fracture and deformation mechanism of sandstone under water-rock interaction was investigated via uniaxial compression acoustic emission(AE)experiment and infrared radiation(IR)observation experiment on both natural and saturated sandstone specimens.The influence of water on the mechanical properties as well as AE and IR changes of sandstone were examined through analyzing the axial stress,AE energy rate,fractal dimension,IR frequency histogram and partial degree of each transformation stage.Results demonstrated that the mechanical properties of sandstone such as compressive strength and bearing capacity were evidently weakened by water.Water inhibited the AE activity and crack development scale of sandstone as reflected by larger average peak energy rate,larger amplitude and longer duration of active energy release phase,as well as better synchronicity of energy rate and stress of natural samples than those of water-saturated samples.The correlation dimensions of AE energy rates of both natural and water-saturated sandstone specimens changed in a cyclic upward-downward trend.The AE of water-saturated samples responded to the discrete disordered development and aggregation ordered development of cracks later than that of natural samples,and the release of energy rate was more disordered than that of natural samples.In the meantime,water enhanced the sensitivity of IR,as reflected by the gradual increase in heating area of water-saturated samples during loading and the large heating area of rock surface during failure.On the contrary,natural samples saw slight and unstable temperature changes during loading,and only some high-temperature points during failure.However,both natural and water-saturated specimens experienced a calm period of temperature change before the peak stress.