沿層ボーリングにおける炭層の破壊
沿層ボーリング中のAE活動に関する研究 (第2報)
1984 年 100 巻 1157 号 p. 569-574
詳細
1984 年 100 巻 1157 号 p. 569-574
In this research, the coal fracturing activity due to advance boring was observed by the acoustic emission methods in order to obtain the informations for judging the hazard of coal and gas outburst.
Practically, one-dimensional source location were conducted from acoustic emission signals detected in the stress relief boring for coal seam. Furthermore the amount of cuttings in addition to acoustic emission activity was measured at every unit drilled length in that boring and the shield boring designed specially to prevent the collapse of a borehole. The fracture criterion of the coal seam saturated with gas under high pressure was analyzed to explain the characteristics of the acoustic emission activity in advance boring. The main concluding remarks are as follows:
1) In many cases the acoustic emissions due to fractures of coal seam occurred near the cutting points and in some cases at a distance ahead from the region of the stress concentration associated with the bottom of a borehole.
2) In the former cases the amount of cuttings increases and decreases almost without retard of the acoustic emission activity, while in the latte r cases in some retard.
3) The retard of the discharge of cuttings from the acoustic emission activity is considered to be an useful information for judging the hazard of coal and gas outburst because this retard is due to the local coal fractures which are caused by the change in gas pressure in coal seam at a distance ahead from the bottom of a borehole.
