Formation mechanism of dynamic impact failure zone of super dynamic water inrush in coal mine

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1 t D W ET K E TD74 A (2011) (1984 ) qweiqlm@163.com Formation mechanism of dynamic impact failure zone of super dynamic water inrush in coal mine QIAO Wei 1, 2, LI Wen-ping 1, SUN Ru-hua 1, LI Xiao-qin 1, HU Ge 3 (1. School of Resources and Earth Science, China University of Mining and Technology, Xuzhou , China; 2. Postdoctoral Workstation, Yankuang Group, Zoucheng , China; 3. Shangdong Institute and Laboratory of Geological Sciences, Jinan , China) Abstract: The elastic energy accumulates in the hard rock stratum with whole blocky structure because of underground mining. The hard rock stratum will fail with the increase of the elastic energy and instantaneously release massive energy of motion, which induces high water pressure in the aquifer near the hard rock stratum. The high water pressure creates the water-conducting which is impacted instantly between the aquifer and excavation free face so as to form the dynamic water inrush. Haizi Coal Mine is taken as a case study. The geological conditions and main factors of separation layer water are analyzed based on field investigation and numerical simulation. The burst tendency indices (Dt, W ET and K E ) of the hard rock stratum are tested. The excess hydrostatic pressure under the action of the impact dynamics is obtained by the relevant tests. Thus, the formation mechanism of dynamic impact failure zone is preliminarily studied based on the theory of blasting dynamic mechanics. Key words: mining engineering; separation layer water; dynamic water inrush; excess hydrostatic pressure; impact dynamics [1] [2] [3-6] [7]

2 m 3 /h 18 min 905 m 3 /h 3.5 h 139 m 3 /h 300 m 3 1 m [7-8] [7-13] m 10 2 m 0.05 m m 745 # m RQD 100% MPa MPa GPa 0.17 # MPa MPa m 745 # MPa R m 1.4 m m 3 m 1 Fig. 1 Borehole televiewer photos for separation layer zone in siltstone # m m m m Fig. 2 Borehole televiewer photos for separation layer zone in medium-sandstone # # 7 34 m # m # 7 3

4 Fig. 3 Overburden separation layer and major principal stress after working face No completed m # m # 7 34 m 2 3 m m Fig. 4 Overburden separation layer and major principal stress at.location of 150 m in working face No t D W ET K E 3 Y11 Y t D ms W ET 3.27~10.40 K E t D ms W ET K E Y11 t D W ET K E Fig. 5 Test curves of t D, W ET and K E for igneous rock of Y11 group

5 MTS φ 30 mm φ 50 mm 20 mm φ 4 mm 7 Fig. 7 Sealed rock specimens including water MTS Pw 0.2 MPa Pw 8 Y17 t D W ET K E Fig. 6 Test curves of t D, W ET and K E for medium-sandstone of Y17 group 745 Fig. 8 Failure rock specimens 2 9 Table 1 Evalution of burst tendency for igneous rock and medium-sandstone /m t D W ET K E Y5 R Y6 R Y7 R Y10 R Y11 R Y13 R Y14 R Y16 R Y17 R Y18 R Y19 R

6 Table 1 Test results of excess hydrostatic pressure under action of impact dynamics /s /MPa /s /MPa LR-R LR-R LR-R MS-R LR-R FS-R Fig. 9 Variation of excess hydrostatic pressure with time 2 3 m MPa 1 # m 2

7 a 10 b 10 c 2r b r 0 r b =0.5W max W max, 2 U = q L 5 /576EI (1) 2 L = 2 h R / q (2) 0 T U = ( h /12 E) 2 R / q (3) q MN/m E MPa I I = h 3 /12 R T MPa h m T [14-15] P = B/ R α (4) P R MPa B B =72 MPa α α = 0.72 R R = R/ Q Q c TNT Q c = Q/ Q vt kg/m P 0 c α α 2 2 B Q B Q P0 = α = α (5) R QVT r0 QVT r 0 r0 rb + 0.5Wmax r b r b = L 0 /2π Q Fig. 10 Process of simplified model for formation mechanism of.dynamic impact failure zone MJ/m Q VT TNT Q VT = MJ/kg

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