Effect of in-situ stress on the cracking and permeability enhancement in coal seams by deep-hole cumulative blasting
-
摘要: 針對地應力對煤層深孔聚能爆破致裂增透問題，在分析鉆孔圍巖應力場、爆生裂隙擴展及動態卸載效應的基礎上，對不同地應力條件下聚能爆破作用過程及裂隙發育特征進行了數值模擬，并通過在不同埋深下的聚能爆破現場試驗，探討了地應力對煤層深孔聚能爆破致裂增透的作用。結果表明：在高地應力煤層進行深孔聚能爆破時，地應力在煤層深孔聚能爆破裂隙擴展不同階段的作用存在較大區別，在未進行聚能爆破時，鉆孔圍巖應力狀態及形變特征由鉆孔形態以及地應力共同決定。在聚能爆破作用初始階段，由于聚能爆破對圍巖產生的沖擊作用明顯強于地應力，因此爆生裂隙在初期的擴展方向主要由聚能裝藥結構控制，沿聚能槽開口方向形成定向裂隙；隨著裂隙向四周擴展，爆破作用逐漸減弱，地應力作用逐漸顯現，鉆孔圍巖在地應力作用下產生切向壓應力，限制了爆破徑向裂隙擴展。同時，與主應力方向不同的煤體裂隙在較強的剪應力作用下逐漸沿最大主應力方向偏轉。當爆破作用產生的等效動態應力無法繼續使煤體進一步壓縮時，鉆孔圍巖內積聚的彈性應變能開始朝爆破中心方向釋放，形成新的裂隙。此外，不同方向上的裂隙擴展范圍受側壓系數控制，當垂直主應力一定時，隨著側壓系數增大，最小主應力方向的裂隙范圍進一步減小。Abstract: With the gradual development of coal mining to deeper levels, the in-situ stress of coal seams shows an increasing trend, resulting in a gradual decrease in permeability, and the stress state of the coal and rock mass and the properties of the surrounding rock also change. The mechanical properties and mechanical parameters of coal and rock mass greatly differ between depths, which influences the cracking and permeability enhancement effect of coal seam deep-hole cumulative blasting. Aiming at the problem of the increasing permeability of coal seams by deep-hole cumulative blasting under in-situ stress, on the basis of an analysis of the stress field of the surrounding rock and the stress of the blasting crack surface, the process of cumulative blasting and crack development characteristics under different confining pressures were numerically simulated. Through field tests of cumulative blasting under different buried depths, the influence of in-situ stress on the cracking and permeability enhancement effect of coal seam deep-hole cumulative blasting was discussed. The results show that the role of in-situ stress differs greatly between the stages of radial crack expansion of coal seam deep-hole cumulative blasting. Before blasting, the stress state and deformation characteristics of the borehole surrounding rock are determined by borehole shape and in-situ stress. In the initial stage of cumulative blasting, the impact of cumulative blasting on the surrounding rock is obviously stronger than in-situ stress. Therefore, the expansion direction of blasting cracks in the initial stage is mainly determined by the cumulative structure, and directional cracks are formed along the opening direction of the cumulative charge groove. With the crack extension, the blasting effect is gradually weakened, and the in-situ stress is dominant. The surrounding rock of the borehole produces tangential compressive stress under the in-situ stress, which limits the radial crack expansion of blasting. Meanwhile, the coal cracks that are not collinear with the principal stress gradually deflect toward the direction of the maximum principal stress under the action of strong shear stress. When the equivalent dynamic stress produced by blasting cannot continue to compress the coal, the elastic strain energy accumulated in the surrounding rock of the borehole begins to release toward the blasting center, causing the coal to crack and produce new cracks. In addition, the crack expansion range in different directions is controlled by the lateral pressure coefficient. When the vertical principal stress is constant, the crack range toward minimum principal stress further decreases with increasing lateral pressure coefficient.
-
圖 2 鉆孔受力情況. (a) 圍巖受力情況; (b)單元受力情況
Figure 2. Stress diagram of the borehole: (a) stress condition of surrounding rock; (b) stress condition of unit
圖 3 地應力作用下鉆孔圍巖塑性區范圍
Figure 3. Range of the plastic zone of the borehole surrounding rock under in-situ stress
圖 7 煤體爆生裂隙發育特征. (a) σv=10 MPa, λ=1; (b) σv=10 MPa, λ=1.5; (c) σv=10 MPa, λ=2;(d) σv=20 MPa,λ=1; (e) σv=20 MPa, λ=1.5; (f) σv=20 MPa, λ=2
Figure 7. Development characteristics of coal cracks formed by blasting: (a) σv = 10 MPa, λ = 1; (b) σv = 10 MPa, λ = 1.5; (c) σv = 10 MPa, λ = 2; (d) σv=20 MPa, λ = 1; (e) σv = 20 MPa, λ = 1.5; (f) σv = 20 MPa, λ = 2
圖 8 聚能爆破裂隙發育過程. (a) t=268 μs; (b) t=600 μs; (c) t=1000 μs
Figure 8. Crack development process of cumulative blasting: (a) t = 268 μs; (b) t = 600 μs; (c) t = 1000 μs
圖 10 平煤股份十礦、十二礦地應力隨埋深關系
Figure 10. Relationship between in-situ stress and buried depth in the No.10 and No.12 coal mines of Pingdingshan
圖 11 煤層深孔聚能爆破試驗鉆孔布置示意圖. (a) 順層鉆孔；(b) 穿層鉆孔
Figure 11. Layout of the boreholes of deep-hole cumulative blasting in a coal seam: (a) borehole drilling along the seam; (b) borehole drilling across the seam
圖 12 煤層深孔聚能爆破后抽采孔內瓦斯體積分數及純流量變化. (a) 埋深 ≈ 837 m; (b) 埋深 ≈ 943 m; (c) 埋深 ≈ 1057 m
Figure 12. Variation in gas volume fraction and flow rate in the drainage hole before and after cumulative blasting: (a) buried depth ≈ 837 m; (b) buried depth ≈ 943 m; (c) buried depth ≈ 1057 m
圖 13 地應力作用下的聚能爆破煤體致裂過程. (a) 鉆孔初始受力階段; (b) 聚能爆破作用主控階段; (c) 地應力作用主控階段; (d) 圍巖動態卸載效應主控階段
Figure 13. Coal cracking process of cumulative blasting under in-situ stress: (a) initial stress stage of borehole; (b) main control stage of cumulative blasting; (c) main control stage of in-situ stress; (d) main control stage of surrounding rock dynamic unloading effect
久色视频表 1 試驗區鉆孔遠場圍巖應力狀態
Table 1. Stress state of the surrounding rock of the borehole in the test area
Experimental
locationBuried
depth/mAzimuth/
(°)Dip angle/
(°)σh/MPa σv/MPa λ 24100
Working face≈ 837 22.2 13 26.9 21.7 1.24 31060
Working face≈ 943 34.5 35.5 32.3 23.4 1.38 33200
Working face≈ 1057 24.0 12 30.9 26.4 1.17 
下載: 導出CSV
-
參考文獻
[1] Yuan L. Theory and Technology of Gas Drainage and Capture in Soft Multiple Coal Seams of Low Permeability Coal. Beijing. China Coal Industry Publishing House, 2004袁亮. 松軟低透煤層群瓦斯抽采理論與技術. 北京: 煤炭工業出版社, 2004 [2] Mu C M, Wang H L, Huang W Y, et al. Increasing permeability mechanism using directional cumulative blasting in coal seams with high concentration of gas and low permeability. Rock Soil Mech, 2013, 34(9): 2496穆朝民, 王海露, 黃文堯, 等. 高瓦斯低透氣性煤體定向聚能爆破增透機制. 巖土力學, 2013, 34(9):2496 [3] Liu J, Liu Z G, Gao K, et al. Experimental study and application of directional focused energy blasting in deep boreholes. Chin J Rock Mech Eng, 2014, 33(12): 2490劉健, 劉澤功, 高魁, 等. 深孔定向聚能爆破增透機制模擬試驗研究及現場應用. 巖石力學與工程學報, 2014, 33(12):2490 [4] Guo D Y, Zhao J C, Zhang C, et al. Mechanism of control hole on coal crack initiation and propagation under deep-hole cumulative blasting in coal seam. Chin J Rock Mech Eng, 2018, 37(4): 919郭德勇, 趙杰超, 張超, 等. 煤層深孔聚能爆破控制孔作用機制研究. 巖石力學與工程學報, 2018, 37(4):919 [5] Guo D Y, Lv P F, Zhao J C, et al. Research progress on permeability improvement mechanisms and technologies of coalbed deep-hole cumulative blasting. Int J Coal Sci Technol, 2020, 7(2): 329 doi: 10.1007/s40789-020-00320-5 [6] He M C, Xie H P, Peng S P, et al. Study on rock mechanics in deep mining engineering. Chin J Rock Mech Eng, 2005, 24(16): 2803 doi: 10.3321/j.issn:1000-6915.2005.16.001何滿潮, 謝和平, 彭蘇萍, 等. 深部開采巖體力學研究. 巖石力學與工程學報, 2005, 24(16):2803 doi: 10.3321/j.issn:1000-6915.2005.16.001 [7] Xie H P. Research review of the state key research development program of China: Deep rock mechanics and mining theory. J China Coal Soc, 2019, 44(5): 1283謝和平. 深部巖體力學與開采理論研究進展. 煤炭學報, 2019, 44(5):1283 [8] Fairhurst C. Some challenges of deep mining. Engineering, 2017, 3(4): 527 doi: 10.1016/J.ENG.2017.04.017 [9] Zhao B Y, Wang H D. Feasibility of deep-hole blasting technology for outburst prevention and permeability enhancement in high-gas-content coal seams with low-permeability subjected to high geo-stresses. Explos Shock Waves, 2014, 34(2): 145 doi: 10.11883/1001-1455(2014)02-0145-08趙寶友, 王海東. 深孔爆破技術在高地應力低透氣性高瓦斯煤層增透防突中的適用性. 爆炸與沖擊, 2014, 34(2):145 doi: 10.11883/1001-1455(2014)02-0145-08 [10] Xiao S Y, Jiang Y J, Liu Z X, et al. Hard rock blasting energy distribution and fragmentation characteristics under high earth stress. J Vib Shock, 2018, 37(15): 143 doi: 10.13465/j.cnki.jvs.2018.15.020肖思友, 姜元俊, 劉志祥, 等. 高地應力下硬巖爆破破巖特性及能量分布研究. 振動與沖擊, 2018, 37(15):143 doi: 10.13465/j.cnki.jvs.2018.15.020 [11] Zhao J J, Zhang Y, Ranjith P G. Numerical modelling of blast-induced fractures in coal masses under high in situ stresses. Eng Fract Mech, 2020, 225: 106749 doi: 10.1016/j.engfracmech.2019.106749 [12] Kutter H K, Fairhurst C. On the fracture process in blasting. Int J Rock Mech Min Sci Geomech Abstr, 1971, 8(3): 181 doi: 10.1016/0148-9062(71)90018-0 [13] Mu C M. Model investigation on coal crack growth under coupling action of blasting loads and crustal stress. J Exp Mech, 2012, 27(4): 511穆朝民. 爆炸荷載和地應力耦合作用下煤體裂紋擴展的模型實驗研究. 實驗力學, 2012, 27(4):511 [14] Mu C M, Pan F. Numerical study on the damage of the coal under blasting loads coupled with geostatic stress. Chin J High Press Phys, 2013, 27(3): 403 doi: 10.11858/gywlxb.2013.03.014穆朝民, 潘飛. 煤體在爆炸荷載和地應力耦合作用下裂紋擴展的數值模擬. 高壓物理學報, 2013, 27(3):403 doi: 10.11858/gywlxb.2013.03.014 [15] Chen M, Lu W B, Zhou C B, et al. Influence of initial in situ stress on blasting-induced cracking zone in tunnel excavation. Rock Soil Mech, 2009, 30(8): 2254 doi: 10.3969/j.issn.1000-7598.2009.08.009陳明, 盧文波, 周創兵, 等. 初始地應力對隧洞開挖爆生裂隙區的影響研究. 巖土力學, 2009, 30(8):2254 doi: 10.3969/j.issn.1000-7598.2009.08.009 [16] Tao J, Yang X G, Li H T, et al. Effects of in-situ stresses on dynamic rock responses under blast loading. Mech Mater, 2020, 145: 103374 doi: 10.1016/j.mechmat.2020.103374 [17] Yang L Y, Ding C X. Fracture mechanism due to blast-imposed loading under high static stress conditions. Int J Rock Mech Min Sci, 2018, 107: 150 doi: 10.1016/j.ijrmms.2018.04.039 [18] Yang R S, Ding C X, Li Y L, et al. Crack propagation behavior in slit charge blasting under high static stress conditions. Int J Rock Mech Min Sci, 2019, 119: 117 doi: 10.1016/j.ijrmms.2019.05.002 [19] Lu W B, Yang J H, Yan P, et al. Dynamic response of rock mass induced by the transient release of in situ stress. Int J Rock Mech Min Sci, 2012, 53: 129 doi: 10.1016/j.ijrmms.2012.05.001 [20] Zhang F P, Peng J Y, Qiu Z G, et al. Rock-like brittle material fragmentation under coupled static stress and spherical charge explosion. Eng Geol, 2017, 220: 266 doi: 10.1016/j.enggeo.2017.02.016 [21] Xiao S Y, Su L J, Jiang Y J, et al. Numerical analysis of hard rock blasting unloading effects in high in situ stress fields. Bull Eng Geol Environ, 2019, 78(2): 867 doi: 10.1007/s10064-017-1067-7 [22] Guo D Y, Zhao J C, Lü P F, et al. Dynamic effects of deep-hole cumulative blasting in coal seam and its application. Chin J Eng, 2016, 38(12): 1681郭德勇, 趙杰超, 呂鵬飛, 等. 煤層深孔聚能爆破動力效應分析與應用. 工程科學學報, 2016, 38(12):1681 [23] Wu S C. Rock Mechanics. Beijing: Higher Education Press, 2021吳順川. 巖石力學. 北京: 高等教育出版社, 2021 [24] Sih G C, Paris P C, Erdogan F. Crack-tip, stress-intensity factors for plane extension and plate bending problems. J Appl Mech, 1962, 29(2): 306 doi: 10.1115/1.3640546 [25] Williams J G, Ewing P D. Fracture under complex stress—The angled crack problem. Int J Fract, 1972, 8(4): 441 doi: 10.1007/BF00191106 [26] Xie H P, Ju Y, Li L Y. Criteria for strength and structural failure of rocks based on energy dissipation and energy release principles. Chin J Rock Mech Eng, 2005, 24(17): 3003 doi: 10.3321/j.issn:1000-6915.2005.17.001謝和平, 鞠楊, 黎立云. 基于能量耗散與釋放原理的巖石強度與整體破壞準則. 巖石力學與工程學報, 2005, 24(17):3003 doi: 10.3321/j.issn:1000-6915.2005.17.001 [27] Yang J H, Jiang Q H, Zhang Q B, et al. Dynamic stress adjustment and rock damage during blasting excavation in a deep-buried circular tunnel. Tunn Undergr Space Technol, 2018, 71: 591 doi: 10.1016/j.tust.2017.10.010 [28] Tao M, Li X B, Wu C Q. Characteristics of the unloading process of rocks under high initial stress. Comput Geotech, 2012, 45: 83 doi: 10.1016/j.compgeo.2012.05.002 [29] Livermore Software Technology Corporation. LS-DYNA keyword users manual: version 971 [Z/OL]. LSTC (2007-05)[2022-01-25].https://www.dynasupport.com/manuals/ls-dyna-manuals/ls-dyna-971/view [30] Zhang J G. Study on the Disaster Mechanism and Prevention Key Technologies of Deep Mine Dynamic Disasters in Pingdingshan Coal Mine [Dissertation]. Xuzhou: China University of Mining and Technology, 2012張建國. 平頂山礦區深井動力災害災變機理及防治關鍵技術研究[學位論文]. 徐州: 中國礦業大學, 2012 [31] Cai M F, Guo Q F, Li Y, et al. In situ stress measurement and its application in the 10th Mine of Pingdingshan Coal Group. J Univ Sci Technol Beijing, 2013, 35(11): 1399蔡美峰, 郭奇峰, 李遠, 等. 平煤十礦地應力測量及其應用. 北京科技大學學報, 2013, 35(11):1399 [32] Wang Y C, Jing H W, Chen K F, et al. Study of distribution regularities and regional division of in situ stresses for Pingdingshan mining area. Chin J Rock Mech Eng, 2014, 33(Suppl 1): 2620王迎超, 靖洪文, 陳坤福, 等. 平頂山礦區地應力分布規律與空間區劃研究. 巖石力學與工程學報, 2014, 33(增刊1): 2620 -
點擊查看大圖
計量
- 文章訪問數: 356
- HTML全文瀏覽量: 138
- PDF下載量: 39
- 被引次數: 0
