To further understand the fracture behavior of rock materials containing en echelon flaws\nand determine precursor information for the final collapse of damaged mineral assemblies under\ncompression, a series of uniaxial compression experiments using a loading system, an acoustic\nemission system and a video camera was conducted on sandstone specimens containing en echelon\nflaws. The mechanical properties, energy dissipation characteristics and acoustic emission\nparameters of compression failure of selected specimens were successively analyzed. The results\nshowed that crack initiation was accompanied by a stress drop, step-like characteristics on the\nenergy consumption curve and increased crackling noises, which were used as early warning\nsignals before the final collapse happened. In addition, we used the histogram statistics method\nand maximum likelihood method to analyze the distribution of acoustic emission energy and\ndetermined that the acoustic emission energy distributions of sandstone specimens containing en\nechelon flaws followed a power law. With the progress of the experiment, the optimum exponents\nchanged in different stages and gradually decreased as failure was approached, which could also\nbe used as an early warning signal before the final collapse happened. This paper may provide\nsome theoretical basis for monitoring and warning about the collapse and instability of engineering\nrock masses containing en echelon flaws.
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