Fig 1.
Flow diagram of MS monitoring of coal and gas outburst.
Fig 2.
Detection technology principles of seismic wave tomography.
Table 1.
Relationship between positive wave speed anomalies and stress concentration.
Table 2.
Relationship between negative wave speed anomalies and stress reduction.
Table 3.
Detailed description of coal and gas outbursts in Jinjia Mine.
Fig 3.
Location of Jinjia coal mine, Liupanshui city, Guizhou province, China.
Fig 4.
(a) Working face No. 11224 and the location of MS sensors; (b) the coal seams 3#, 7#and 9# had been mined above working face No. 11224; the 22# coal seam was mainly monitored for this paper; the coal seams 17#, 181#, 18# and 24# were original unexploited.
The red dots represent the locations of the sensors.
Fig 5.
The planar distribution of MS events.
Fig 6.
Accumulated energy and frequency of MS events from the heading face to the geological structure.
The above results indicate that the distribution characteristics of the MS events are closely related to mining activities and anomalous geological bodies.
Fig 7.
Timing of changes in MS signals around the heading area.
Fig 8.
The relation between MS frequency, release energy and tunneling speed.
Fig 9.
(a) Contour map of the wave velocity anomaly coefficient An in the 6/15–7/04 gas drainage period; (b) Contour map of the wave velocity anomaly coefficient An in the 7/05–7/14 roadway excavation period; (c) Contour map of the wave velocity anomaly coefficient An in the 7/15–7/31 gas drainage period.
Fig 10.
(a) Variation in coal seam thickness and gas content with distance to a geological structure; (b) Variation in the coal seam thickness and firmness coefficient f with distance to a geological structure.
Fig 11.
Monitoring principles and scheme of the KBD5 monitor.
Fig 12.
Monitoring results from the KBD5 monitor.
Table 4.
The date and result of K1 value determination in Jinjia Mine.
Fig 13.
Summary of roadway excavation information.