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The deformation and fracture of surrounding rock in deep underground engineering have the characteristics of time mutation and space continuity. In order to monitor and provide early warning of the dynamic deformation and fracture characteristics of deep surrounding rock, a real‐time digital displacement measuring instrument was developed in this paper. The proposed device represented a kind of surrounding rock deformation and fracture monitoring method, which had the continuous and real‐time advantages. Based upon the simulation experiments, the dynamic deformation and fracture of deep roadway surrounding rock were measured synchronously using the digital displacement measuring instrument testing system (DDMITS) and the V‐STARS measurement system. Comparative measurement results indicated that the DDMITS had a higher reliability. The deformation of roadway surrounding rock gradually increased with the increase of loading. The roof deformation and caving changing patterns in coal seam mining were studied using similar simulation experiments based on the DDMITS. The vertical displacement response of rock strata was more obvious than the horizontal displacement. There was a sharp increase in the vertical displacement during the collapse of the rock strata. Additionally, the vertical displacement velocity showed fluctuations. Meanwhile, the fluctuations in the vertical displacement acceleration increased significantly. The DDMITS could achieve full‐field measurement and the noncontact measurement of three‐dimensional deformation. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing can evidently improve the coalbed methane production in underground coal mines, but it is difficult to delimit the stimulated area accurately. In order to evaluate the stimulated area, microseismic (MS) monitoring technique is proposed to investigate the seismic responses of the induced fractures of hydraulic fracturing. Three coal seams were targeted to be treated in a coal mine. An array of geophones was set along the underground roadway to detect the MS signals caused by HF. In order to verify the result of MS monitoring, water content of each coal seam has been measured before and after HF treatment. The results showed that a series of MS events were detected during the entire HF process, and a sharp MS event usually occurred during the first hour of HF process. The energy of the sharp MS event had higher magnitude than others. The MS distribution exhibited complex morphological features. The directionless MS response was distributed over a radius of less than 40 m but tended to be significantly conjugated with a radius of more than 40 m. HF could stimulate both the coal seam and the rock layers nearby. The achievable stimulated area in the coal seam was determined to be 50 m × 50 m according to the MS density and water content. The stimulated area in terms of MS density was easily found to be broader than the area of water direct intrusion. The present study indicated that MS monitoring technique could potentially be used for evaluation of HF in underground coal mine. [ABSTRACT FROM AUTHOR]