Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

Abstract

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

Experimental Study on Strength, Acoustic Emission, and Energy Dissipation of Coal under Naturally and Forcedly Saturated Conditions

“…It is generally believed that the acoustic signals are accompanied by microcracks generation and propagation, so the AE counts reflect the rupture situation in coal samples indirectly. e less the AE counts, the less the number of brittle cracks [33]. erefore, the crack number of forcedly saturated coal samples is significantly less than the naturally saturated coal samples.…”

“…ere are many different modulus to represent the elastic modulus of coal samples, such as average modulus, secant modulus and tangent modulus [33]. e average modulus was selected in this study.…”

Experimental Study on Stress Evolution and Microseismic Signals under Vibration Conditions of Coal during Excavation and Subsequent Waiting Time

“…During the past 20 years, microseismic monitoring has been widely used in major mineral-producing regions and countries, such as Europe, South Africa, North America, Canada, and China [3][4][5][6]. Since the 1970s, the United States has used microseismic monitoring in mines to ensure the safety of underground personnel and developed supporting software and hardware for this purpose [7].…”

Strength and Failure Characteristics of Natural and Water‐Saturated Coal Specimens under Static and Dynamic Loads

“…Water injection may alleviate or prevent the occurrence of rock bursts [20,21]. Numerous research studies have been carried out on the mechanical properties of coal specimens under static loading: Su et al [22,23] studied the effects of saturation time on the coal burst tendency index; Pan et al [24] conducted research on the saturated time effect in the Qianqiu coal mine as well as the coal seam water injection method; and Liu et al [25,26] investigated the mechanical properties of water-injected coal specimens by using water injection test equipment. However, the dynamic mechanical properties of saturated coal specimens have rarely been studied.…”