Key Takeaways & Executive Findings
- •• Dynamic load amplitude and frequency significantly accelerate the failure of high static load coal-rock combinations, reducing the number of cycles to failure and increasing irreversible strain. • Acoustic emission event counts decrease with higher dynamic load amplitude but increase with higher frequency, indicating distinct damage mechanisms. • Fractal dimension of broken particles increases more with frequency, while total energy and cumulative elastic energy increase more with amplitude, revealing energy evolution patterns. • These findings provide critical insights for predicting and mitigating dynamic-static load-induced instability in deep coal mines, enhancing safety and support design.
Abstract
Based on MTS Landmark 370.50 rock dynamic and static load fatigue test system and acoustic emission (AE) monitoring method, the damage characteristics and energy evolution law of high static load coal-rock combination (CRC) under the influence of dynamic load parameters were studied. The main results are as follows: 1) Dynamic load increases the rheological properties and damage fracture development of CRC. With the increase of the amplitude and frequency of the dynamic load, the number of dynamic load cycles required for the failure of the CRC decreases, the irreversible strain increases, and the failure of sample accelerates; 2) The AE positioning events during the loading process of the specimen decrease with the increase of the dynamic load amplitude, and increase with the increase of the dynamic load frequency; 3) The fractal dimension, total energy and cumulative elastic energy of the broken particles of the CRC increase with the increase of the amplitude and frequency of the dynamic load. The fractal dimension corresponding to the increase of the dynamic load frequency is larger, and the energy and cumulative elastic energy corresponding to the increase of the dynamic load amplitude are larger.
1. Introduction
During the mining of a working face, the coal-rock mass in the mining roadway is subjected not only to static load superposition due to stress redistribution but also to dynamic load disturbances from main roof breakage, adjacent face mining, and underground blasting [1−3]. This results in the roadway being affected by coupled dynamic and static loading. With the depth of coal mining increasing at a rate of 10−25 m/a, many mines in China have entered deep mining phases [4]. Under conditions of high static loads and strong disturbances at these depths, the coal-rock mass in mining roadways is prone to instability and failure due to high dynamic-static load coupling [5, 6]. This leads to severe roadway deformation and damage to support components, significantly impacting the safe and efficient production of mines.
To reveal the instability and failure mechanisms and precursor information of coal-rock mass in mining roadways under dynamic-static load coupling, many researchers have conducted uniaxial and triaxial compression tests and Hopkinson bar experiments. These studies focus on the mechanical properties, damage characteristics, and energy evolution of coal-rock masses under dynamic-static load conditions [7−9]. In studies on individual coal-rock masses, researchers have analyzed the effects of pre-static loads and frequent dynamic disturbances on the damage characteristics of deep rock masses, developing corresponding damage constitutive models and identifying the relationship between rock damage evolution rate and disturbance frequency [10]. They found that frequent dynamic disturbances promote shear fracturing and weakening, reducing rock’s energy storage capacity and resistance to failure [11, 12]. Additionally, it was observed that the uniaxial compressive strength of coal samples under static load alone is higher than that under combined dynamic-static disturbances, with more severe deformation and failure occurring in the latter case [13]. Furthermore, the failure mode of discontinuous jointed rock masses is primarily determined by joint dip angle rather than the amplitude or frequency of micro-disturbances [14, 15].
As deep mining research progresses, scholars have recognized that deep coal-rock mass failure is influenced more by the structure of the coal-rock combination (CRC) than by individual fracture structures, with dynamic disasters resulting from the overall instability of the composite system [16]. Researchers have studied the failure patterns and mechanical properties of CRC under dynamic-static load coupling. They found that under dynamic loads, the elastic modulus of the composite decreases, peak stress is positively correlated with dynamic load level, and peak strain is negatively correlated [17]. They also explored the evolution of acoustic emission characteristics under different dynamic load parameters.
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TANG Long, TU Shi-hao, TU Hong-sheng, MIAO Kai-jun, GUO Ben-huan, ZHAO Hong-bin, MA Jie-yang (2025). Damage characteristics and energy evolution law of high static load coal-rock combination under the influence of dynamic load parameters. Journal of Central South University. https://doi.org/10.1007/s11771-025-6133-x
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Frequently Asked Questions
What is the main objective of this study?
The study investigates the damage characteristics and energy evolution of high static load coal-rock combinations under varying dynamic load parameters (amplitude and frequency) using acoustic emission monitoring.
How do dynamic load amplitude and frequency affect the failure of coal-rock combinations?
Increasing dynamic load amplitude or frequency reduces the number of cycles to failure, increases irreversible strain, and accelerates sample failure, indicating enhanced damage and rheological behavior.
What is the role of acoustic emission in this research?
Acoustic emission monitoring is used to track damage evolution. The number of AE events decreases with higher amplitude but increases with higher frequency, providing insights into fracture development.
What are the practical implications of this study for deep mining?
The findings help predict instability and failure of coal-rock masses under dynamic-static loading, aiding in the design of support systems and safety measures to prevent dynamic disasters in deep mines.
How does the fractal dimension of broken particles relate to dynamic load parameters?
The fractal dimension increases with both amplitude and frequency, but the increase is more pronounced with frequency, indicating more complex fragmentation patterns under higher frequency disturbances.
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