Testing study of expanding and cracking outburst coal seam by the static expansion agent

By testing the expanding and cracking effect of the M3 outburst coal seam in the No. 1235 haulage roadway in a coal mine,the static expansion forces and the endoscopic figures of the internal face of the drainage holes were ob- tained,and the feasibility was further verified by the static expanding and cracking the outburst coal seam. The site test shows that:① With the development of the hydration reaction of the static expansion agent in the expansion holes,the internal faces of the drainage hole near the expansion holes produce the static expansion force with gradual increase until to the peak value,which then decrease gradually until to disappear;② In the test scheme with the same hole di- ameter,the scheme I produces the static expansion force with the maximum value among the test schemes with three different hole diameters,and the expansion holes with a diameter 94 mm cause the most peak value of the static expan- sion force;③ Under the test condition,the reasonable ratioμbetween hole spacing and hole diameter is about 14-15; ④ In the different schemes with the sameμ,the expanding and cracking effect of the internal faces of the drainage holes are in an obvious increase trend with the hole diameters increase.