Experimental Study of Creep Acoustic Emission Characteristics of Coal Bodies around Boreholes under Different Moisture Contents

Abstract

Water content is an important factor in the deformation-destruction process of coal bodies. To analyze the influence of water on the creep acoustic emission (AE) characteristics of coal rock surrounding a borehole, we conducted graded loading creep AE tests of single-hole specimens with different water contents (0%, 4%, 8% and water-saturation) under uniaxial loading. The findings include the following: the water content affects the creep mechanical properties of the coal body around a borehole. The creep transient strain and steady-state strain increased exponentially with rising water content; the saturated specimen showed the highest increase, reaching 44.5% and 28.6%, respectively. The specimen water content affected the cumulative ringing count (CRC) and the axial strain during creep. The axial strain increased with rising water content, the CRC increased linearly with rising axial strain. The higher the water content, the greater the CRC rise. At different stress levels, the CRC in the 4%, 8% and saturated water content specimens changed by 43%, 53% and 74%, respectively. The AE ringing rate showed a pattern of grow–decline–stabilize at each creep stage. The AEs decreased significantly with the rising water content and the creep curve lagged behind the AE data. This paper provides guidelines for gas extraction, borehole maintenance and AE detection.

Fractal characteristics and damage evaluation of corroded beams under four-point bending tests based on acoustic emission techniques

“…Numerous research results have shown that AE ringing count is a characteristic parameter that can well reflect the variety of material properties because it is proportional to the strain energy released by the motion of dislocations and crack extension inside the material [9,47,48]. Therefore, AE ringing counts and cumulative ringing counts are used as parameters to represent the damage evolution of non-corroded and corroded beams.…”

Research on Hole Collapse Monitoring Technology of Coal Seam Gas Extraction Boreholes

“…In the process of gas management, the hole formation quality of a gas extraction borehole is an important factor in determining the efficiency of gas extraction [5][6][7][8][9]. Under the influence of ground stress and mining, gas extraction boreholes are prone to collapse and deformation, which seriously affects gas management [10,11]. Borehole monitoring is a prerequisite to solving the problem of borehole collapse, can obtain the status information of the borehole, and can effectively prevent the occurrence of borehole collapse, as well as provide services to optimize the arrangement of the borehole, playing a positive role in deepening the process of drilling refinement operation, and greatly improving the effect of gas extraction in a borehole [12][13][14][15].…”