Experimental and numerical simulation of loading rate effects on failure and strain energy characteristics of coal-rock composite samples

Abstract

The deformation and failure of coal and rock is energy-driving results according to thermodynamics. It is important to study the strain energy characteristics of coal-rock composite samples to better understand the deformation and failure mechanism of of coal-rock composite structures. In this research, laboratory tests and numerical simulation of uniaxial compressions of coal-rock composite samples were carried out with five different loading rates. The test results show that strength, deformation, acoustic emission (AE) and energy evolution of coal-rock composite sample all have obvious loading rate effects. The uniaxial compressive strength and elastic modulus increase with the increase of loading rate. And with the increase of loading rate, the AE energy at the peak strength of coal-rock composites increases first, then decreases, and then increases. With the increase of loading rate, the AE cumulative count first decreases and then increases. And the total absorption energy and dissipation energy of coal-rock composite samples show non-linear increasing trends, while release elastic strain energy increases first and then decreases. The laboratory experiments conducted on coal-rock composite samples were simulated numerically using the particle flow code (PFC). With careful selection of suitable material constitutive models for coal and rock, and accurate estimation and calibration of mechanical parameters of coal-rock composite sample, it was possible to obtain a good agreement between the laboratory experimental and numerical results. This research can provide references for understanding failure of underground coal-rock composite structure by using energy related measuring methods.

Keywords

coal-rock composite samples / uniaxial compression / loading rate / acoustic emission / energy evolution

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