Experimental Investigation on Damage Characteristics and Early Warning of Frozen Coal under Uniaxial Compression

Abstract

This article conducted acoustic emission tests of natural coal, natural frozen coal, and saturated frozen coal to explore the damage characteristics of frozen coal and in view of the frozen coal damage early warning problems and explored the strength deformation and acoustic emission characteristics of coal samples. The test results showed that the compressive strength of the frozen coal samples decreased significantly, and the strength of the saturated frozen coal samples was the lowest; more acoustic emissions were generated at the initial loading stage. The damage parameters were defined using the acoustic emission parameters. The damage characteristics of the coal samples were analyzed. The damage model of the coal samples was established based on the power function. The early warning parameter VAEi to analyze the evolution characteristics of the variance curve was proposed; the sudden jump point b of VAEi from the stable development stage to the rapid growth stage was defined as a general early warning point; the endpoint point c of the parameter rapid growth stage was defined as a key early warning point; a zonal and hierarchical early warning was finally proposed.

Experimental Study of the Multiple Fractalisation of Coal and Rock Failure Subjected to the Coupled Effects of Water, Temperature and Dynamic Loads

“…Kodama et al [8] investigated the effects of water content, temperature, and loading rate on the strength and damage process of frozen rock and concluded that the rock's strength increased with increasing water content and loading rate, with the effects being more pronounced at lower temperatures. Sun et al [9] explored the damage characteristics of frozen coal by conducting acoustic emission tests on frozen coal, and they proposed early warning parameters for the characterisation of the evolution of the variance curve, where the compressive strength of frozen coal samples significantly decreased and the saturated frozen coal samples had the lowest compressive strength. Wang et al [10], by observing the microscopic pore structure of sandstone, also found that low temperatures had this promoting effect on coal and rock samples.…”