Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Abstract

Coal mass is deformed and fractured under stress to generate electrical potential (EP) signals. The mechanical properties of coal change with the adsorption of gas. To investigate the EP response characteristics of gas-bearing coal during deformation and fracture, a test system to monitor multi-parameters of gas-bearing coal under load was designed. The results showed that abundant EP signals were generated during the loading process and the EP response corresponded well with the stress change and crack expansion, and validated this with the results from acoustic emission (AE) and high-speed photography. The higher stress level and the greater the sudden stress change led to the greater EP abnormal response. With the increase of gas pressure, the confining action and erosion effect are promoted, causing the damage evolution impacted and failure characteristics changes. As a result, the EP response is similar while the characteristics were promoted. The EP response was generated due to the charge separation caused by the friction effect etc. during the damage and deformation of the coal. Furthermore, the main factors of the EP response were different under diverse loading stages. The presence of gas promoted the EP effect. When the failure of the coal occurred, EP value rapidly rose to a maximum, which could be considered as an anomalous characteristic for monitoring the stability and revealing failure of gas-bearing coal. The research results are beneficial for further investigating the damage-evolution process of gas-bearing coal.

Study of the influence of the characteristics of loose residual coal on the spontaneous combustion of coal gob

“…The minimum CSC period was introduced by Kalenkin. [39][40][41] He defined it as the time required for the coal to absorb oxygen in adiabatic conditions, to heat the coal, to release the water and gas from the coal, and to increase the temperature of the coal to the ignition temperature. He used this to establish a calculation model for the minimum CSC period:…”

Experimental Test and Field Observations of an Electric Potential Monitoring Device for Dynamic Hazards during Mining Activities

“…Previous studies show that the deformation and rupture process of a coal body can generate significant electric potential (EP) signals, and the EP response is closely related to the damage evolution process and stress state of the coal body [9,10]. Studying the EP response characteristics of a coal body during damage and failure processes can indirectly monitor the damage evolution process of a coal body and identify the precursor information of instability and failure of coal and rock mass [11]. Eccles et al observed abnormal signals of EP response before rock fracture under different experimental conditions [12].…”

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“…Shkuratnik et al [25] investigated the memory effects of AE by conducting uniaxial and triaxial cyclic unloading tests. With recent advancements in electronic technologies and high-speed photography, several modern techniques for rock mechanics research have been commonly adopted in the recent years [26], for example, electromagnetic radiation technology [27,28], scanning electron microscope, infrared thermal image technology [29], and electrical resistivity technology [22]. However, the application of these technologies is limited to the study of coal and rock damage/failure, while the influence of water content and soaking is rarely considered.…”