Abstract：The initiation and propagation law of hydraulic fractures in altered gold ore hold paramount importance for the hydraulic fracturing exploitation of gold mines. This study conducted true triaxial hydraulic fracturing experiments on altered gold ore under varying water injection rates，minimum horizontal principal stresses，and angles between water injection holes and joint surfaces. Results indicate that：(1) when the difference in horizontal principal stress for altered gold ore ranges from 1 to 3 MPa，initiation stress spans 22.2 to 40.0 MPa. With increasing water injection rates(from 5 mL/min to 15 and 30 mL/min)，initiation stress rises by 17.4% and 34.3%，respectively. An elevation in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) results in initiation stress increases by 37.4% and 80.2%，respectively. The angle between water injection holes and joint surfaces(from 0° to 45 and 90°) induces initiation stress increases by 6.3% and 24.9%，respectively. Altered gold ore，under similar in-situ stress conditions，exhibits higher initiation stresses compared to sedimentary rocks. (2) Hydraulic fractures in altered gold ore can be categorized into two modes: linear and polygonal propagation. Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min) results in heightening perpendicularity between the fracture propagation direction and the minimum horizontal principal stress direction，with a reduction in the number of turns from 2 times to 0. An increase in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) leads to an increase in the number of turns from 0 to 1 and 3 times，with larger turning angles. With the increasing angle between water injection holes and joint surfaces(from 0° to 45 and 90°)，interference from joint surfaces is intensified，causing propagation deviations towards the joint surfaces. Hydraulic fractures in altered gold ore predominantly exhibit main fractures，with fewer and simpler secondary fractures，whereas sedimentary rocks display a higher number of complexly distributed secondary fractures. (3) The fracture surfaces in altered gold ore can be classified based on morphological characteristics into smooth and rough surfaces. Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min) results in a decrease in protrusion size on the fracture surfaces，with the protrusion area decreasing from 63% to 45% and 0%. Increasing the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa) leads to an increase in the protrusion area from 0% to 40% and 45%. Increasing the angle between water injection holes and joint surfaces(from 0° to 45° and 90°) all maintains joint surface features on the fracture surfaces with smooth and non-protruding characteristics. The fracture surfaces of altered gold ore are rough，while those of sedimentary rocks are comparatively smoother.
[1] DETOURNAY E. Mechanics of hydraulic fractures[J]. Annual review of fluid mechanics，2016，48：311–339.
[2] LIU Y，LI G，CHEN J，et al. Numerical simulation of hydraulic fracturing assisted depressurization development in hydrate bearing layers based on discrete fracture models[J]. Energy，2023，263：126146.
[3] HE Q，SUORINENI F T，OH J. Strategies for creating prescribed hydraulic fractures in cave mining[J]. Rock Mechanics and Rock Engineering，2017，50(4)：967–993.
[4] 付海峰，黄刘科，张丰收，等. 射孔模式对水力压裂裂缝起裂与扩展的影响机制研究[J]. 岩石力学与工程学报，2021，40(增2)：3 163–3 173.(FU Haifeng，HUANG Liuke，ZHANG Fengshou，et al. Effect of perforation technologies on the initiation and propagation of hydraulic fracture[J]. Chinese Journal of Rock Mechanics and Engineering，2021，40(Supp.2)：3 163–3 173.(in Chinese))
[5] ROCHE V，VAN D，PREISIG G. A study of 3D modeling of hydraulic fracturing and stress perturbations during fluid injection[J]. Journal of Petroleum Science and Engineering，2018，170：829–843.
[6] RASHID H，OLORODE O，CHUKWUDOZIE C. An iteratively coupled model for flow，deformation，and fracture propagation in the fractured unconventional reservoirs[J]. Journal of Petroleum Science and Engineering，2022，214：110468.
[7] 王恩元，张国锐，张超林，等. 我国煤与瓦斯凸出防治理论技术研究进展与展望[J]. 煤炭学报，2022，47(1)：297–322.(WANG Enyuan，ZHANG Guorui，ZHANG Chaolin，et al. Research progress and prospect on theory and technology for coal and gas outburst control and protection in China[J]. Journal of China Coal Society，2022，47(1)：297–322.(in Chinese ))
[8] PATEL S M，SONDERGELD C H，RAI C S. Hydraulic fracture permeability estimation using stimulation pressure data[J]. International Journal of Rock Mechanics and Mining Sciences，2018，101：50–53.
[9] JIANG Y，LIAN H，VINH P，et al. Propagation behavior of hydraulic fracture across the coal-rock interface under different interfacial friction coefficients and a new prediction model[J]. Journal of Natural Gas Science and Engineering，2019，68：102894.
[10] 潘俊锋，马文涛，刘少虹，等. 坚硬顶板水射流预制缝槽定向预裂防冲技术试验[J]. 岩石力学与工程学报，2021，40(8)：1 591–1 602. (PAN Junfeng，MA Wentao，LIU Shaohong，et al. A prevention technology of rock burst based on directional presplitting of water jet prefabricated slot in hard roof[J]. Chinese Journal of Rock Mechanics and Engineering，2021，40(8)：1 591–1 602.(in Chinese))
[11] 林 健，郭 凯，孙志勇，等. 强烈动压巷道水力压裂切顶卸压压裂时机研究[J]. 煤炭学报，2021，46(增1)：140–148.(LIN Jian，GUO Kai，SUN Zhiyong，et al. Study on fracturing timing of hydraulic fracturing top-cutting and pressure relief in roadway with strong dynamic pressure[J]. Chinese Journal of Rock Mechanics and Engineering，2021，46(Supp.1)：140–148.(in Chinese))
[12] TRIPOPPOOM S，WANG X，LIU Z，et al. Characterizing hydraulic and natural fractures properties in shale oil well in Permian basin using assisted history matching[J]. Fuel，2020，275：117950.
[13] CHEN S，ZHANG J，YIN D，et al. Relative permeability measurement of coal microchannels using advanced microchip technology[J]. Fuel，2022，312(3)：122633.
[14] 王 涛，柳占立，庄 茁. 页岩气高效开采的可压裂度和射孔簇间距预测[J]. 力学学报，2022，54(2)：517–525.(WANG Tao，LIU Zhanli，ZHUANG Zhuo. Fracturing degree and prediction of perforation cluster spacing for efficient exploitation of shale gas[J]. Chinese Journal of Theoretical and Applied Mechanics，2022，54(2)：517–525.(in Chinese))
[15] 张洪伟，张 通，万志军，等. 高温高压下岩石水力压裂实验新型封隔技术[J]. 东北大学学报，2021，42(3)：422–427.(ZHANG Hongwei，ZHANG Tong，WAN Zhijun，et al. New sealing techniques for hydraulic fracturing experiment of rock under high temperature and high pressure conditions[J]. Journal of Northeastern University，2021，42(3)：422–427.(in Chinese))
[16] CHENG Y，ZHANG Y，YU Z，et al. Investigation on reservoir stimulation characteristics in hot dry rock geothermal formations of China during hydraulic fracturing[J]. Rock Mechanics and Rock Engineering，2021，54：3 817–3 845.
[17] KUMARI W G，RANJITH P G，PERERA M S，et al. Hydraulic fracturing under high temperature and pressure conditions with micro-CT applications：geothermal energy from hot dry rocks[J]. Fuel，2018，230：138–154.
[18] 唐书恒，朱宝存，颜志丰. 地应力对煤层气井水力压裂裂缝发育的影响[J]. 煤炭学报，2011，36(1)：65–69.(TANG Shuheng，ZHU Baocun，YAN Zhifeng. Effect of crustal stress on hydraulic fracturing in coalbed methane wells[J]. Journal of China Coal Society，2011，36(1)：65–69.(in Chinese ))
[19] 朱 葛，董世民，潘子卜. 水力压裂非稳定激励下储层内动应力仿真模型[J]. 煤炭学报，2021，46(增1)：149–156.(ZHU Ge，DONG Shimin，PAN Zibo. Simulation model of dynamic stress in reservoir under unsteady excitation of hydraulic fracturing[J]. Journal of China Coal Society，2021，46(Supp.1)：149–156.(in Chinese ))
[20] 宋明春，林少一，杨立强，等. 胶东金矿成矿模式[J]. 矿床地质，2020，39(2)：215–236.(SONG Mingchun，LIN Shaoyi，YANG Liqiang，et al. Metallogenic model of Jiaodong Peninsula gold deposits[J]. Mineral Deposits，2020，39(2)：215–236.(in Chinese ))
[21] ZHUANG L，JUNG S G，DIAZ M，et al. Laboratory true triaxial hydraulic fracturing of granite under six fluid injection schemes and grain-scale fracture observations[J]. Rock Mechanics and Rock Engineering，2020，53：4 329–4 344.
[22] STEPHANSSON O，SEMIKOVA H，ZIMMERMANN G，et al. Laboratory pulse test of hydraulic fracturing on granitic sample cores from Äspö HRL，Sweden[J]. Rock Mechanics and Rock Engineering，2019，52(2)：629–633.
[23] 蔺海晓，杜春志. 煤岩拟三轴水力压裂实验研究[J]. 煤炭学报，2011，36(11)：1 801–1 805.(LIN Haixiao，DU Chunzhi. Experimental research on the quasi three-axis hydraulic fracturing of coal[J]. Journal of China Coal Society，2011，36(11)：1 801–1 805.(in Chinese ))
[24] 周 舟，金 衍，曾义金，等. 青海共和盆地干热岩地热储层水力压裂物理模拟和裂缝起裂与扩展形态研究[J]. 吉林大学学报，2019，49(5)：1 425–1 430.(ZHOU Zhou，JIN Yan，ZENG Yijin，et al. Experimental study on hydraulic fracturing physics simulation，crack initiation and propagation in hot dry rock geothermal reservoir in Gonghe basin，Qinghai[J]. Journal of Jilin University，2019，49(5)：1 425–1 430.(in Chinese ))
[25] SCHWARTZKOPFF A K，MELKOUMIAN N S，XU C . Breakdown pressure and propagation surface of a hydraulically pressurized circular notch within a rock material[J]. Rock Mechanics and Rock Engineering，2021，54：191–218.
[26] MOU P，PAN J，WANG K，et al. Influences of hydraulic fracturing on microfractures of high-rank coal under different in-situ stress conditions[J]. Fuel，2020，287：119566.
[27] 杨永明，李 霄，汪 震，等. 射孔参数对非均质砂岩水力压裂裂缝扩展规律的影响[J]. 土木工程学报，2022，55(1)：1–9.(YANG Yongming，LI Xiao，WANG Zhen，et al. Influence of perforation parameters on propagation laws of hydraulic fracture in heterogeneous sandstones[J]. China Civil Engineering Journal，2022，55(1)：1–9.(in Chinese))
[28] 陈 勉，庞 飞，金 衍. 大尺寸真三轴水力压裂模拟与分析[J]. 岩石力学与工程学报，2000，19(增1)：868–872.(CHEN Mian，PANG Fei，JIN Yan. Experiments and analysis on hydraulic fracturing by a large-size triaxial simulator[J]. Chinese Journal of Rock Mechanics and Engineering，2000，19(Supp.1)：868–872.(in Chinese))
[29] 石欣雨，文国军，白江浩，等. 煤岩水力压裂裂缝扩展物理模拟实验[J]. 煤炭学报，2016，41(5)：1 145–1 151.(SHI Xinyu，WEN Guojun，BAI Jianghao，et al. A physical simulation experiment on fracture propagation of coal petrography in hydraulic fracturing[J] Journal of China Coal Society，2016，41(5)：1 145–1 151.(in Chinese ))
[30] ZHANG X，DETOURNAY E，JEFFREY R. Propagation of a penny-shaped hydraulic fracture parallel to a free surface with application to inducing rock mass caving for mining[J]. International Journal of Fracture，2002，115：125–158.
[31] 曾义金，周 俊，王海涛，等. 深层页岩真三轴变排量水力压裂物理模拟研究[J]. 岩石力学与工程学报，2019，38(9)：1 758–1 766. (ZENG Yijin，ZHOU Jun，WANG Haitao，et al. Research on true triaxial hydraulic fracturing in deep shale with varying pumping rates[J]. Chinese Journal of Rock Mechanics and Engineering，2019，38(9)：1 758–1 766.(in Chinese))
[32] 吴拥政，杨建威. 煤矿砂岩横向切槽真三轴定向水力压裂试验[J]. 煤炭学报，2020，45(3)：927–935.(WU Yongzheng，YANG Jianwei．True tri-axial directional hydraulic fracturing test on sandstone with transverse groove coal mine[J]. Journal of China Coal Society，2020，45(3)：927–935.(in Chinese ))
[33] 谭 鹏，金 衍，侯 冰，等. 煤岩定向井水力裂缝起裂及非平面扩展实验[J]. 石油勘探与开发，2017，44(3)：439–445.(TAN Peng，JIN Yan，HOU Bing，et al. Experimental investigation on fracture initiation and non-planar propagation of hydraulic fractures in coal seams[J]. Petroleum Exploration and Development，2017，44(3)：439–445.(in Chinese))
[34] 刘永莉，周文佐，郭 斌，等. 相似模型实验中泥灰岩相似材料研究[J]. 岩石力学与工程学报，2020，39(增1)：2 795–2 803.(LIU Yongli，ZHOU Wenzuo，GUO Bin，et al. Study on marl similar materials in similar simulation test[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(Supp.1)：2 795–2 803.(in Chinese))
[35] 姜婷婷，张建华，黄 刚. 煤岩水力压裂裂缝扩展形态试验研究[J]. 岩土力学，2018，39(10)：3 677–3 684.(JIANG Tingting，ZHANG Jianhua，HUANG Gang. Experimental study of fracture geometry during hydraulic fracturing in coal[J]. Rock and Soil Mechanics，2018，39(10)：3 677–3 684.(in Chinese ))
[36] 陶云奇，刘 东，许 江，等. 大尺寸复杂应力水力压裂裂缝扩展模拟试验研究[J]. 采矿与安全工程学报，2019，36(2)：405–412.(TAO Yunqi，LIU Dong，XU Jiang，et al. Experimental study on hydraulic fracturing propagation in coal/rock with large size and complex stress[J]. Journal of Mining and Safety Engineering，2019，36(2)：405–412.(in Chinese ))
[37] 马 耕，张 帆，刘 晓，等. 地应力对破裂压力和水力裂缝影响的试验研究[J]. 岩土力学，2016，37(增2)：216–222.(MA Geng，ZHANG Fan，LIU Xiao，et al. Experimental study of impact of crustal stress on fracture pressure and hydraulic fracture[J]. Rock and Soil Mechanics，2016，37(Supp.2)：216–222.(in Chinese))
[38] YANG W，GENG Y，ZHOU Z，et al. True triaxial hydraulic fracturing test and numerical simulation of limestone[J]. Journal of Central South University，2020，27(10)：3 025–3 039.
[39] 邵长跃，潘鹏志，赵德才，等. 流量对水力压裂破裂压力和增压率的影响研究[J]. 岩土力学，2020，41(7)：2 411–2 421.(SHAO Changyue，PAN Pengzhi，ZHAO Decai，et al. Effect of pumping rate on hydraulic fracturing breakdown pressure and pressurization rate[J]. Rock and Soil Mechanics，2020，41(7)：2 411–2 421.(in Chinese))
[40] 夏彬伟，刘 浪，彭子烨，等. 致密砂岩水平井多裂缝扩展及转向规律研究[J]. 岩土工程学报，2020，42(8)：1 549–1 555.(XIA Binwei，LIU Lang，PENG Ziye，et al. Multi-fracture propagation and deflection laws of horizontal wells in tight sandstone[J]. Chinese Journal of Geotechnical Engineering，2020，42(8)：1 549–1 555.(in Chinese))
[41] 魏元龙，杨春和，郭印同，等. 须家河组致密砂岩水力压裂裂缝形态的试验研究[J]. 岩石力学与工程学报，2016，35(增1)：2 720–2 731.(WEI Yuanlong，YANG Chunhe，GUO Yintong，et al. Experimental study on hydraulic fracture geometry of tight sandstone from Xujiahe group[J]. Chinese Journal of Rock Mechanics and Engineering，2016，35(Supp.1)：2 720–2 731.(in Chinese ))
[42] 刘正和，杨录胜，廉浩杰，等. 砂岩钻孔轴向预制裂缝定向压裂试验研究[J].煤炭学报，2019，44(7)：2 057–2 065.(LIU Zhenghe，YANG Lusheng，LIAN Haojie，et al． Experimental study of directional fracturing in sandstones with prefabricated cracks in the axial direction of borehole[J]. Journal of China Coal Society，2019，44(7)：2 057–2 065.(in Chinese))
[43] HE J，LIN C，LI X，et al. Initiation，propagation，closure and morphology of hydraulic fractures in sandstone cores[J]. Fuel，2017，208(15)：65–70.
[44] 孙可明，张树翠. 含层理页岩气藏水力压裂裂纹扩展规律解析分析[J]. 力学学报，2016，48(5)：1 229–1 237.(SUN Keming，ZHANG Shucui. Hydraulic fracture propagation in shale gas bedding reservoir analytical analysis[J]. Chinese Journal of Theoretical and Applied Mechanics，2016，48(5)：1 229–1 237.(in Chinese))
[45] 衡 帅，杨春和，曾义金，等. 页岩水力压裂裂缝形态的试验研究[J]. 岩土工程学报，2014，36(7)：1 243–1 251.(HENG Shuai，YANG Chunhe，ZENG Yijin，et al. Experimental study on hydraulic fracture geometry of shale[J]. Chinese Journal of Geotechnical Engineering，2014，36(7)：1 243–1 251.(in Chinese))
[46] 郭印同，杨春和，贾长贵，等. 页岩水力压裂物理模拟与裂缝表征方法研究[J]. 岩石力学与工程学报，2014，33(1)：52–59.(GUO Yintong，YANG Chunhe，JIA Changgui，et al. Research on hydraulic fracturing physical simulation of shale and fracture characterization methods[J]. Chinese Journal of Rock Mechanics and Engineering，2014，33(1)：52–59.(in Chinese ))
[47] 侯振坤，杨春和，王 磊，等. 大尺寸真三轴页岩水平井水力压裂物理模拟试验与裂缝延伸规律分析[J]. 岩土力学，2016，37(2)：407–414.(HOU Zhenkun，YANG Chunhe，WANG Lei，et al. Hydraulic fracture propagation of shale horizontal well by large-scale true triaxial physical simulation test[J]. Rock and Soil Mechanics，2016，37(2)：407–414.(in Chinese))
[48] 侯 冰，陈 勉，程 万，等. 页岩气储层变排量压裂的造缝机制[J]. 岩土工程学报，2014，36(11)：2 149–2 152.(HOU Bing，CHEN Mian，CHENG Wan，et al. Fracturing mechanism of shale gas reservoir with variable pump rates[J]. Chinese Journal of Geotechnical Engineering，2014，36(11)：2 149–2 152.(in Chinese))
[49] HUBBERT M K，WILLIS D G. Mechanics of hydraulic fracturing[J]. American Association of Petroleum Geologists，1972，18：153–166.
[50] 武倩宇，韩登林，张吉振，等. 页岩储层中颗粒尺寸效应对微裂缝发育的影响：以威远地区志留系龙马溪组页岩储层为例[J]. 中南大学学报，2022，53(9)：3 603–3 614.(WU Qianyu，HAN Denglin，ZHANG Jizhen，et al. Influence of particle size effect on microfracture development in shale reservoir：a case study of the Silurian Longmaxi Formation shale reservoir in Weiyuan area[J]. Journal of Central South University，2022，53(9)：3 603–3 614.(in Chinese))
2024, Vol. 43 
