Abstract
In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone samples with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the samples start to crack earlier; the cracks grow slowly; the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure; more secondary cracks are produced. The saturated samples release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated samples release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the amplitude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.
Highlights
Due to the exhaustion of shallow resources, the exploitation of mineral resources and oil-gas energy has gradually entered the deep part of the Earth
Water can significantly affect the mechanical properties of rocks, especially sedimentary rocks containing clay minerals such as sandstone and shale [4,5]
The study of mechanical behavior of fractured rock mass under load and its signal monitoring are related to the stability and safety of the project
Summary
Due to the exhaustion of shallow resources, the exploitation of mineral resources and oil-gas energy has gradually entered the deep part of the Earth. The study of mechanical behavior of fractured rock mass under load and its signal monitoring are related to the stability and safety of the project To address this issue, many scholars have carried out a series of experiments by making prefabricated cracks with different shapes, quantities and arrangements [22,23,24,25,26]. The effect of water on rock micro-fracture mode and corresponding acoustic emission signal response were discussed This is of great significance to investigate the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.
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