PFC numerical analysis on crack initiation mechanism of fracture grouting in top of Ordovician limestone
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摘要: 超前区域注浆是煤层底板灰岩水害防治的有效手段，而注浆工程中的劈裂注浆过程是决定注浆效果的关键环节，但由于对受注灰岩地层裂隙起裂机制认识不清，致使劈裂注浆过程中注浆压力、浆液水灰比等参数缺少有效控制，难以保证注浆效果。针对上述问题，利用颗粒元(Particle Flow Code，PFC)数值模拟软件，考虑浆液水灰比、地应力水平、弱面和裂隙的倾角和宽度等因素，开展奥陶系灰岩顶部劈裂注浆数值模拟计算。结果表明：在弱面和裂隙条件下起裂压力均随浆液水灰比(1∶1、2∶1、3∶1)的增大而减小，随最大主应力与最小主应力差值(9、12、15 MPa)的减小而增大，随弱面或裂隙宽度(3、8、15 mm)及其与最大主应力夹角(30°、60°、90°)的增大而减小；起裂裂隙沿平行于最大主应力方向延展；起裂压力值随弱面与基质强度比(0.30、0.03)的减小而减小，当弱面强度较高时，起裂压力大于裂隙条件下的起裂压力，而且沿着基质起裂；当注浆孔置于弱面两端或裂隙中间时，起裂裂隙沿弱面或裂隙的两端起裂，当注浆孔置于弱面中间位置时，起裂裂隙沿中间位置的基质起裂。研究结果有助于底板水害超前区域改造劈裂注浆的有效控制，指导注浆参数的选取，为解放深部煤炭资源提供技术支撑。Abstract: The advanced regional grouting is an effective means to prevent and control the water hazard of limestone in coal seam floor, and the fracture grouting projects is a key link to determine the effect of the grouting in floor against water hazard. However, due to the unclear understanding of the fracture initiation mechanism of the injected limestone stratum, the grouting pressure, grout water-cement ratio and other grouting parameters in the process of fracture grouting are not effectively controlled. Thus, it is difficult to guarantee the grouting effect. In order to solve the above problems, numerical simulation calculation was conducted for the fracture grouting in top of Ordovician limestone with the Particle Flow Code (PFC) numerical simulation software, considering the grout water-cement ratio, in-situ stress, and the dip angle and width of weak surface and crack. The results show that: The fracture initiation pressure decreases with the increase of the grout water-cement ratio (1∶1, 2∶1, 3∶1), but increases with the decrease of the difference between the maximum and minimum principal stresses (9, 12 and 15 MPa) under the weak surface and fracture conditions. Besides, the crack initiation pressure decreases with the increase of the width of the weak surface or crack (3, 8, 15 mm) and the angle between the weak surface/crack and the maximum principal stress (30°, 60°, 90°). The initiated cracks propagate along the direction parallel to the maximum principal stress. The fracture initiation pressure decreases with the decrease of strength ratio of weak surface to matrix (0.30, 0.03). In case of weak surface with high strength, the fracture initiation pressure is greater than that under the fracture condition, and the cracks propagate along the matrix. When the grouting hole is located at both ends of the weak surface or in the middle of the crack, the cracks are initiated along the weak surface or at both ends of the crack. When the grouting hole is located in the middle of the weak surface, the cracks propagate along the matrix in the middle position. Generally, the research results are helpful to the effective control of fracture grouting in the advanced regional for floor reconstruction against water hazard, and guide the selection of grouting parameters, thus providing technical support for the development of deep coal resources.
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图 7 不同计算时步不同水灰比下注浆劈裂裂隙形态
Fig. 7 Fracture grouting fracture morphology at different calculation time-step and water-cement ratio
图 8 弱面强度比0.03注浆压力曲线与裂缝数量
Fig. 8 Variation curves of grouting pressure vs cracks (weak surface to matrix strength ratio 0.03)
图 9 弱面与基质强度比0.03时的注浆裂隙扩展路径
Fig. 9 Expansion path of grouting crack (weak surface to matrix strength ratio 0.03)
图 11 不同计算时间步长的注浆劈裂裂隙形态
Fig. 11 Fracture grouting fracture morphology at different calculation time-step and water-cement ratio
图 12 弱面或裂隙条件下劈裂注浆起裂压力随浆液水灰比变化曲线
Fig. 12 Curves of fracture initiation pressure with grout water cement ratio under weak surface or crack condition
图 13 不同地应力条件下注浆孔应力分布情况
注：黑色线段表示压力；红色线段表示拉力。
Fig. 13 Stress distribution of grouting holes under different in-situ stress conditions
图 14 3种地应力条件下注浆浆液扩展路径
注：绿色颗粒表示路径。
Fig. 14 Grouting grout expansion paths under three in-situ stress conditions
图 15 弱面与基质强度比0.03时注浆压力与裂缝数量变化曲线
Fig. 15 Variation curves of grouting pressure vs cracks (weak surface to matrix strengh ratio 0.03)
图 16 裂隙与基质强度比为0.03时不同地应力水平下注浆劈裂裂隙
Fig. 16 Grouting split cracks at different in-situ stresses (fracture to matrix strength ratio 0.03)
图 18 3×104计算时间步长时注浆劈裂裂隙形态
Fig. 18 Fracture morphology 3×104 time step grouting split cracks
图 19 9×104计算时间步长时注浆劈裂裂隙形态
Fig. 19 Fracture morphology 9×104 time step grouting split cracks
图 20 3种地应力水平下注浆浆液扩展最终路径
Fig. 20 The final paths of grouting grout expansion under three in-situ stress conditions
图 21 弱面或裂隙条件下劈裂注浆起裂压力随最大主应力与最小主应力差值变化曲线
Fig. 21 The curves of fracture grouting initiation pressure changing with difference between the maximum and minimum principal stresses under the condition of weak surface or crack
图 22 弱面与基质强度比为0.30时不同弱面宽度注浆压力与裂缝数量变化曲线
Fig. 22 When the strength ratio of weak surface to matrix is 0.30, grouting pressure and cracks change curves of different weak surface widths under
图 23 不同弱面宽度下劈裂注浆压裂裂隙
Fig. 23 Fracture of splitting grouting with different weak surface widths
图 24 3种弱面宽度条件下注浆扩散路径及劈裂裂隙扩展最终形态
Fig. 24 The grouting diffusion paths and the final morphology of split fracture expansion under three weak surface widths
图 25 弱面与基质强度比为0.03时不同弱面宽度注浆劈裂裂隙形态
Fig. 25 Fracture morphology of weak surface grouting with different weak surface widths under strength ratio 0.03 of weak face to martrix
图 26 弱面与基质强度比为0.03时不同弱面倾角注浆劈裂裂隙形态
Fig. 26 When the strength ratio of weak surface to matrix is 0.03, the fracture morphology of weak plane grouting with different dip angles
图 27 3种裂隙倾角条件下浆液扩散路径及裂隙扩展形态
Fig. 27 Slurry diffusion paths and fracture propagation morphology under three fracture dip angles
图 28 3种裂隙倾角条件下注浆扩散路径及劈裂裂隙扩展最终形态
Fig. 28 The grouting diffusion paths and final morphology of fracture propagation under three fracture dip angles
图 30 3种裂隙开度条件下注浆扩散路径及劈裂裂隙扩展最终形态
Fig. 30 The grouting diffusion paths and final morphology of fracture propagation under three crack widths
图 33 弱面或裂隙条件下劈裂注浆起裂压力随裂隙或弱面宽度变化曲线
Fig. 33 Variation curves of fracture initiation pressure with angle of crack or weak surface opening under weak surface or fracture condition
图 32 弱面或裂隙条件下劈裂注浆起裂压力随裂隙与最大主应力夹角变化曲线
Fig. 32 Variation curves of fracture initiation pressure with angle between fracture and maximum principal stress under weak surface or fracture condition
表 1 数值模拟与室内试验试样宏观力学性质对比
Table 1 Comparison of macroscopic mechanical properties between numerical simulation and laboratory test samples
类型 单轴抗压强度/MPa 弹性模量/GPa 泊松比 室内试验 30.30 4.07 0.25 数值模拟 31.83 3.96 0.25 
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表 2 劈裂注浆模型试样微观参数
Table 2 Microscopic parameters of split grouting model specimen
类型 弹性模量/GPa 刚度比 摩擦因数 最大最小半径比 颗粒最小半径/mm 密度/(g·cm−3) 法向强度/MPa 切向强度/MPa 半径系数 颗粒单元 2.75 2.25 0.50 1.66 0.55 2.73 黏结 2.75 2.25 21.5±4.0 21.5±4.0 1
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表 3 峰峰矿区九龙矿地应力测量结果[23]
Table 3 In-situ stress measurement results of Fengfeng mining area, Jiulong Mine[23]
钻孔位置 深度/m 测点号 主应力 垂向应力/MPa 主应力类型 数值/MPa 方位角/(°) 倾角/(°) 231工作面(运料巷55车后) 560 九龙4号点 σ1 27.2 93 −5 15.1 σ2 16.3 2 −3 σ3 15.0 238 −83 北外泄水巷 750 九龙5号点 σ1 24.4 109 −22 20.3 σ2 22.7 −13 −52 σ3 10.0 212 −28
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表 4 数值模拟方案
Table 4 Numerical simulation scheme
影响因素 σ1/MPa σ3/MPa 水灰比值 浆液黏度/(Pa·s) 裂隙倾角/(°) 裂隙开度/mm 裂隙长度/mm 水灰比 25 16 1.0 0.1153 30 8 70 25 16 2.0 0.0967 30 8 25 16 3.0 0.0285 30 8 裂隙倾角 25 16 3.0 0.0285 60 8 25 16 3.0 0.0285 90 8 应力水平 25 13 3.0 0.0285 30 8 25 10 3.0 0.0285 30 8 裂隙宽度 25 16 3.0 0.0285 30 3 25 16 3.0 0.0285 30 15
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表 5 劈裂注浆过程中计算参数
Table 5 Fracturing parameters in the process of fracture grouting
计算模型 浆液黏度/
(10−3 Pa∙s)浆液体积
模量/GPa渗透率/
(m·d–1)注入速率/
(m3·s−1)颗粒元模型 115/97/29 10 2 2.0×10−8
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[1] 虎维岳. 华北东部深部岩溶及煤矿岩溶水害特征[J]. 煤田地质与勘探,2010,38(2):23−27.HU Weiyue. The characteristics of karst and deep coal mine karst water hazards in eastern North China[J]. Coal Geology & Exploration,2010,38(2):23−27. [2] 柳昭星,董书宁,南生辉,等. 邯邢矿区中奥灰顶部空隙特征显微CT分析[J]. 采矿与安全工程学报,2021,38(2):343−352.LIU Zhaoxing,DONG Shuning,NAN Shenghui,et al. Micro–CT analysis of void characteristics at the top of middle Ordovician limestone in Hanxing Mining Area[J]. Journal of Mining & Safety Engineering,2021,38(2):343−352. [3] 董书宁,柳昭星,郑士田,等. 基于岩体宏细观特征的大型帷幕注浆保水开采技术及应用[J]. 煤炭学报,2020,45(3):1137−1149.DONG Shuning,LIU Zhaoxing,ZHENG Shitian,et al. Technology and application of large curtain grouting water conservation mining based on macroscopic and mesoscopic characteristics of rock mass[J]. Journal of China Coal Society,2020,45(3):1137−1149. [4] 董书宁,刘其声. 华北型煤田中奥陶系灰岩顶部相对隔水段研究[J]. 煤炭学报,2009,34(3):289−292.DONG Shuning,LIU Qisheng. Study on relative aguiclude existed in mid–Ordovician limestone top in North China coal field[J]. Journal of China Coal Society,2009,34(3):289−292. [5] 董书宁,王皓,张文忠. 华北型煤田奥灰顶部利用与改造判别准则及底板破坏深度[J]. 煤炭学报,2019,44(7):2216−2226.DONG Shuning,WANG Hao,ZHANG Wenzhong. Judgement criteria with utilization and grouting reconstruction of top Ordovician limestone and floor damage depth in North China coal field[J]. Journal of China Coal Society,2019,44(7):2216−2226. [6] 郑士田. 两淮煤田煤层底板灰岩水害区域超前探查治理技术[J]. 煤田地质与勘探,2018,46(4):142−146.ZHENG Shitian. Advanced exploration and control technology of limestone water hazard in coal seam floor in Huainan and Huaibei coalfields[J]. Coal Geology & Exploration,2018,46(4):142−146. [7] 郑安兴,罗先启,陈振华. 基于扩展有限元法的岩体水力劈裂耦合模型[J]. 岩土力学,2019,40(2):799−808.ZHENG Anxing,LUO Xianqi,CHEN Zhenhua. Hydraulic fracturing coupling model of rock mass based on extended finite element method[J]. Rock and Soil Mechanics,2019,40(2):799−808. [8] FRANGI A, NOVATI G, SPRINGHETTI R, et al. 3D fracture analysis by the symmetric Galerkin BEM[J]. Computational Mechanics, 2002, 28(3/4): 220–232. [9] RAO B N,RAHMAN S. An efficient meshless method for fracture analysis of cracks[J]. Computational Mechanics,2000,26(4):398−408.. doi: 10.1007/s004660000189 [10] 袁敬强,陈卫忠,谭贤君,等. 软弱地层注浆的细观力学模拟研究[J]. 岩土力学,2011,32(增刊2):653−659.YUAN Jingqiang,CHEN Weizhong,TAN Xianjun,et al. Mesomechanical simulation of grouting in weak strata[J]. Rock and Soil Mechanics,2011,32(Sup.2):653−659. [11] TAN X C, KOU S Q, LINDQVIST P A. Application of the DDM and fracture mechanics model on the simulation of rock breakage by mechanical tools[J]. Engineering Geology, 1998, 49(3/4): 277–284. [12] 严成增. 模拟水压致裂的另一种二维FDEM–flow方法[J]. 岩土力学,2017,38(6):1789−1796.YAN Chengzeng. A new two–dimensional FDEM–flow method for simulating hydraulic fracturing[J]. Rock and Soil Mechanics,2017,38(6):1789−1796. [13] CHEN Tielin,ZHANG Liangyi,ZHANG Dingli. An FEM/VOF hybrid formulation for fracture grouting modelling[J]. Computers and Geotechnics,2014,58:14−27.. doi: 10.1016/j.compgeo.2014.02.002 [14] 尤田,刘军,吴玉勤,等. 富水粉细砂地层注浆三维颗粒流数值模拟分析[J]. 轨道交通与地下工程,2015,33(6):68−71.YOU Tian,LIU Jun,WU Yuqin,et al. Numerical simulation analysis of grouting in water–rich sand stratum by three–dimensional particle flow software[J]. Track Traffic & Underground Engineering,2015,33(6):68−71. [15] ZHANG Zhenlong,SHAO Zhushan,FANG Xiaobo,et al. Research on the fracture grouting mechanism and PFC numerical simulation in loess[J]. Advances in Materials Science & Engineering,2018,2018:1−7. [16] ZHANG Qi,ZHANG Xiaoping,JI Peiqi. Numerical study of interaction between a hydraulic fracture and a weak plane using the bonded–particle model based on moment tensors[J]. Computers and Geotechnics,2019,105:79−93.. doi: 10.1016/j.compgeo.2018.09.012 [17] 孙锋,张顶立,陈铁林,等. 土体劈裂注浆过程的细观模拟研究[J]. 岩土工程学报,2010,32(3):474−480.SUN Feng,ZHANG Dingli,CHEN Tielin,et al. Meso–mechanical simulation of fracture grouting in soil[J]. Chinese Journal of Geotechnical Engineering,2010,32(3):474−480. [18] 秦鹏飞. 不良地质体注浆细观力学模拟研究[J]. 煤炭学报,2020,45(7):2646−2654.QIN Pengfei. Study on meso–mechanical simulation of grouting in bad geo–body[J]. Journal of China Coal Society,2020,45(7):2646−2654. [19] 耿萍,卢志楷,丁梯,等. 基于颗粒流的围岩注浆动态过程模拟研究[J]. 铁道工程学报,2017,34(3):34−40.. doi: 10.3969/j.issn.1006-2106.2017.03.007GENG Ping,LU Zhikai,DING Ti,et al. Research on the dynamic process simulation of rock grouting based on particle flow[J]. Journal of Railway Engineering Society,2017,34(3):34−40.. doi: 10.3969/j.issn.1006-2106.2017.03.007 [20] Itasca Consulting Group. PFC2D user’s manual (version3.1)[M]. Minneapolis, Minnesota: Itasca Consulting Group Inc., 2004. [21] Itasca Consulting Group. PFC2D (particle flow code in 2D) theory and background[R]. Minneapolis, Minnesota: Itasca Consulting Group Inc., 2008. [22] 赵庆彪,赵兵文,付永刚,等. 大采深矿井地面区域治理奥灰水害关键技术研究[J]. 煤炭科学技术,2016,44(8):14−20.ZHAO Qingbiao,ZHAO Bingwen,FU Yonggang,et al. Research on key technology to control Ordovician limestone water disaster on surface region of deep mining depth mine[J]. Coal Science and Technology,2016,44(8):14−20. [23] 胡宝玉. 邯邢矿区深部开采煤层底板奥灰突水机理及防治关键技术[D]. 北京: 煤炭科学研究总院, 2020.HU Baoyu. Mechanism of water inrush from Ordovician limestone and key technology of prevention and control in deep mining seam floor of Hanxing Mining Area[D]. Beijing: China Coal Research Institute, 2020. [24] LIU Zhaoxing,DONG Shuning,WANG Hao,et al. Influences on the performance of cement–based grout used to reform the upper middle Ordovician limestone in Hanxing Mining Area[J]. Arabian Journal of Geosciences,2021,14(13):1272.. doi: 10.1007/s12517-021-07512-6 -
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