Fracture Characteristics and Evolution Law of Water-Bearing Coal Rock with Longitudinal Fractures
The longitudinal fractures and water content in coal rock have a significant effect on the mechanical properties and fracture characteristics of coal rock.Uniaxial compression tests were conducted on water-bearing coal rocks with longitudinal fractures,and acoustic emission events were monitored.The influences of longitudinal fractures on the peak stress,peak strain,elastic modulus,and failure mode of water-bearing coal rock were analyzed,and the relationship between water content and mechanical properties of coal rock was explored.The study reveals the significant difference in failure modes between intact coal rock and coal rock with longitudinal fracture,that is intact coal rock tends to self-sustaining failure,while coal rock with longitudinal fracture shows non-self-sustaining failure,and the peak strength decreases by about 20％.In addition,during the loading process of coal rock with longitudinal fracture,when the loading time reaches 48.5％-62.6％,the acoustic emission events will agglomerate in the failure center area of the coal rock.It is also found that the relationship between water content(ωa)and soaking time(t)is ωa=0.821nt+0.31,and the relationship between peak strength(σ)and water content(ωa)isσ=19.77-3.1iωa.These experimental results not only provide a basis for the qualitative description of the failure mode,failure range,and failure strength of coal rock,but also have an important reference for exploring the deformation and failure mechanism of coal rock and the stability analysis of underground engineering.
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