基于水压致裂法的岩石抗拉强度研究
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摘要
为了揭示水压致裂法和巴西劈裂法测量岩石抗拉强度的关系,开展了理论和现场试验研究。基于经典的水压致裂法理论,推导了不同围压下钻孔破裂压力和抗拉强度。利用断裂力学理论建立了水压致裂法和巴西劈裂法测得抗拉强度的关系。利用预制切槽方法模拟天然裂纹,对水力裂缝的起裂压力进行了研究。结果表明:围压为最大主应力等于3倍最小主应力测得的抗拉强度大于围压为0测得的抗拉强度;水压致裂法和巴西劈裂法测量抗拉强度关系与应力场、裂纹长度、断裂韧度3个变量有关;通过在晋城矿区王台铺矿的预制切槽试验,运用断裂力学建立的抗拉强度计算式更为符合现场实际。研究结果可为坚硬难垮落顶板预制切槽的水力压裂设计提供参考。
Theoretical and field experiments were carried out to reveal the relationship between the hydraulic fracturing method and the Brazilian splitting method for measuring the tensile strength of rock. Based on the classical hydraulic fracturing theory, borehole rupture pressure and tensile strength of rock were deduced under different confining pressures. The fracture mechanics theory was applied to establish the relationship between these two methods. Meanwhile, the crack initiation pressure of the hydraulic fracture was studied by using the prefabricated crack method to simulate natural crack. The results show that when the maximum principal stress was three times the minimum principal stress, its measured tensile strength was higher than that without confining pressure. The relationship between these two methods was related to three variables, including stress field, crack length and fracture toughness. The prefabricated crack experiment was performed at Wangtaipu Mine in Jincheng mine area. It was proved that the tensile strength formula established by fracture mechanics was more suitable for practical applications. The research results can provide references for the hydraulic fracturing design of prefabricated cracks in the hard and stable roof.
Theoretical and field experiments were carried out to reveal the relationship between the hydraulic fracturing method and the Brazilian splitting method for measuring the tensile strength of rock. Based on the classical hydraulic fracturing theory, borehole rupture pressure and tensile strength of rock were deduced under different confining pressures. The fracture mechanics theory was applied to establish the relationship between these two methods. Meanwhile, the crack initiation pressure of the hydraulic fracture was studied by using the prefabricated crack method to simulate natural crack. The results show that when the maximum principal stress was three times the minimum principal stress, its measured tensile strength was higher than that without confining pressure. The relationship between these two methods was related to three variables, including stress field, crack length and fracture toughness. The prefabricated crack experiment was performed at Wangtaipu Mine in Jincheng mine area. It was proved that the tensile strength formula established by fracture mechanics was more suitable for practical applications. The research results can provide references for the hydraulic fracturing design of prefabricated cracks in the hard and stable roof.
引文
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[18]尤明庆.水压致裂法测量地应力方法的研究[J].岩土工程学报,2005,27(3):350-353.YOU Ming-qing.Study on the geo-stresses measurement with hydro-fracture of borehole[J].Chinese Journal of Geotechnical Engineering,2005,27(3):350-353.
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[21]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1981.China Aviation Research Institute.Stress intensity factor handbook[M].Beijing:Science Press,1981.
[2]郭翔,王学滨,白雪元,等.加载方式及抗拉强度对巴西圆盘试验影响的连续-非连续方法数值模拟[J].岩土力学,2017,38(1):214-220.GUO Xiang,WANG Xue-bin,BAI Xue-yuan,et al.Numerical simulation of effects of loading types and tensile strengths on Brazilian disk test by use of a continuum-discontinuum method[J].Rock and Soil Mechanics,2017,38(1):214-220.
[3]邓华锋,张小景,张恒宾,等.巴西劈裂法在层状岩体抗拉强度测试中的分析与讨论[J].岩土力学,2016,(增刊2):309-315.DENG Hua-feng,ZHANG Xiao-jing,ZHANG Heng-bin,et al.Analysis and discussion on Brazilian tests on layered rock tensile strength[J].Rock and Soil Mechanics,2016,(Supp.2):309-315.
[4]贾愚如,范正绮.用水力破裂法测得岩石抗拉强度的统计分析[J].岩石力学与工程学报,1987,6(3):277-286.JIA Yu-ru,FAN Zheng-qi.The statistical analysis for tensile strength of rock by laboratory hydraulic fracturing method[J].Chinese Journal of Rock Mechanics and Enineering,1987,6(3):277-286.
[5]颜玉定,廖远群,吴景浓,等.围压条件下岩石的抗拉强度[J].华南地震,1991,11(2):1-12.YAN Yu-ding,LIAO Yuan-qun,WU Jing-nong.Tension resistent strength of rock under confining pressure[J].South China Journal of Seismology,1991,11(2):1-12.
[6]颜玉定.岩石室内的水压致裂研究[J].岩石力学与工程学报,1988,7(2):115-126.YAN Yu-ding.Study on rock fracture under hydraulic pressure in lab-test[J].Chinese Journal of Rock Mechanics and Engineering,1988,7(2):115-126.
[7]李敬兰,李益明.运用水压破裂法测试岩石的抗拉强度[J].地球科学进展,2004,19(增刊):373-375.LI Jing-lan,LI Yi-ming.The rock tensile strength measurement using hydraulic pressure text[J].Advance in Earth Science,2004,19(Supp.):373-375.
[8]余建华,刘翔鹗.室内真三轴水压致裂模拟实验中的岩石特性[J].石油勘探与开发,1986,(3):63-68.YU Jian-hua,LIU Xiang-e.Some rock characteristics exhibited in a simulated hrdrofracturing text on a true3-Dimensional apparatus[J].Petroleum Exploration and Development,1986,(3):63-68.
[9]张伯崇,江南生,刘长义,等.房山大理岩试件的水压致裂试验[J].地震,1983,(2):24-33.ZHANG Bo-chong,JIANG Nan-sheng,LIU Chang-yi,et al.Fangshan marble specimens of hydraulic fracturing test[J].Earthquake,1983,(2):24-33.
[10]仇万禧.水压致裂的实验研究[J].中国矿业大学学报,1988,(1):39-45.CHOU Wan-xi.Laboratory experiments on hydraulic fracture[J].Journal of Chinese University of Mining&Technology,1988,(1):39-45.
[11]康红普.煤岩体地质力学原位测试及在围岩控制中的应用[M].北京:科学出版社,2013:61-63.KANG Hong-pu.In-situ measurement of coal-rock mass with geo-mechanics and its application in surrounding rock control[M].Beijing:Science Press,2002:40-42.
[12]HAIMSON B,FAIRHURST C.Initiation and extension of hydraulic fractures in rocks[J].Society of Petroleum Engineers Journal,1967,(7):310-318.
[13]徐秉业,刘信声.应用弹塑性力学[M].北京:清华大学出版社,1995:183-203.XU Bing-ye,LIU Xin-sheng.Application of elastoplastic mechanics[M].Beijing:Tsinghua University Press,1995:183-203.
[14]李铀,袁亮,刘冠学,等.深部开采圆形巷道围岩破损区与支护压力的确定[J].岩土力学,2014,35(1):226-231.LI You,YUAN Liang,LIU Guan-xue.Determination of failure zone and support pressure of circular roadway under deep mining[J].Rock and Soil Mechanics,2014,35(1):226-231.
[15]侯朝炯,康红普,马念杰,等.巷道围岩控制[M].北京:中国矿业大学出版社,2013.HOU Chao-jiong,KANG Hong-pu,MA Nian-jie,et al.Roadway surrounding rock control[M].Beijing:China University of Mining and Technology Press,2013.
[16]WANG Y,DUSSEAULT M B.Borehole yield and hydraulic fracture initiation in poorly consolidated rock strata—partⅠ:impermeable media[J].International Journal of Rock Mechanics and Mining Sciences&Geomechanics Abstracts,1991,28(4):235-246.
[17]WANG Y,DUSSEAULT M B.Borehole yield and hydraulic fracture initiation in poorly consolidated rock strata—partⅡ:permeable media[J].International Journal of Rock Mechanics and Mining Sciences&Geomechanics Abstracts,1991,28(4):247-260.
[18]尤明庆.水压致裂法测量地应力方法的研究[J].岩土工程学报,2005,27(3):350-353.YOU Ming-qing.Study on the geo-stresses measurement with hydro-fracture of borehole[J].Chinese Journal of Geotechnical Engineering,2005,27(3):350-353.
[19]RUMMEL F.断裂力学应用于水压致裂应力测量[C]//岩石断裂力学.北京:地震出版社,1992:231-253.RUMMEL F.Fracture mechanics for hydrofracturing stress measurement[C]//Rock Fracture Mechanics.Beijing:Earthquake Press,1992:231-253.
[20]ZHANG Z X,KOU S Q,LINDQVIST P A,et al.The relationship between the fracture toughness and tensile strength of rock[C]//Strength Theories:Applications,Evelopment&Prospects for 21st Century.Beijing:Science Press,1998:215-223.
[21]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1981.China Aviation Research Institute.Stress intensity factor handbook[M].Beijing:Science Press,1981.