东秦岭东江口花岗岩体水压致裂法与AE法地应力测量对比研究
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摘要
中国东部现今构造应力场的特征表现为以水平应力为主,最大主压应力方向为近EW向,而秦巴地区已有地应力测量资料显示地应力最大主压应力方向以近SN向为主。为了查明其原因,结合三峡引水工程秦巴段地壳稳定性调查评价工作,在东秦岭东江口花岗岩体内布置一口地应力综合测量孔,进行水压致裂法与AE法地应力测量对比研究。在东江口花岗岩体600m深钻中,将埋深30～596m分27段进行水压致裂法地应力测量,获得20组水平主应力有效数据和25个裂缝破裂方向数据;同时,将埋深为75～599m分11段进行AE法现今最大主应力值测量,获得11个有效数据。将上述2种方法在同一测量深度的测量结果对比后发现:在200m深度以上,2种方法所得结果相近;在200m深度以下,水压致裂法测量的最大水平主应力值比AE法测量的最大主应力值大10MPa左右,前者与邻区已有的水压致裂测量数据相比,普遍偏高,而后者与邻区同一深度的测量结果相近。造成上述结果的原因是,在200m以下岩体中存在残余古构造应力,它与现今构造应力等叠加在一起构成地应力。综合研究结果表明:残余古构造应力是秦巴地区地应力的重要组成部分,不容忽视,上述研究结果对于充分认识秦岭中新生代造山带地应力场的分布规律具有重要的理论意义;同时,还可为穿越秦岭和大巴山的生命线工程的深埋长隧道的规划和设计提供依据。
The result of earthquake mechanism solutions shows that the maximum principal stress axes of the modern tectonic stress field are close upon horizontal and the direction of the maximum principal stress is close to EW in east China;but the result of geostress measurements show that the direction of the maximum horizontal principal stress is close to NS in the Qinling—Bashan Mountain.In order to find the reason,the geostress measurements by AE method and by hydraulic fracturing technique were carried out in the same borehole.The borehole with depth of 600 m was drilled in granite rock mass at Dongjianhkou,Shaanxi Province.From 30 to 596 m,20 valid data of horizontal principal stresses and 25 data of the directions of the fissure by the hydraulic fracturing technique are achieved;from 75 to 599 m,11 data of the maximum principal stresses by AE method are gained.Above 200 m,the data of the hydraulic fracturing technique is consistent with that of AE method at different points in the same depth;but below 200 m,the maximum horizontal stress by the hydraulic fracturing technique is 10 MPa larger than those by AE method.At the same time,the data are larger than those by the hydraulic fracturing technique in its neighbouring region.On the contrary,the data by AE method are consistent with it.The result is that the paleotectonic residual stress exists in granite rock mass below 200 m,and the geostress field is composed of the modern tectonic stress field and the paleotectonic residual stress field.The data by AE method are modern tectonic stress,but the data by the hydraulic fracturing technique are the geostress.The result shows that the paleotectonic residual stress is an important composition of the geostress in the Qinling—Bashan Mountain which is the Mesozoic-Cenozoic orogenic belt.
The result of earthquake mechanism solutions shows that the maximum principal stress axes of the modern tectonic stress field are close upon horizontal and the direction of the maximum principal stress is close to EW in east China;but the result of geostress measurements show that the direction of the maximum horizontal principal stress is close to NS in the Qinling—Bashan Mountain.In order to find the reason,the geostress measurements by AE method and by hydraulic fracturing technique were carried out in the same borehole.The borehole with depth of 600 m was drilled in granite rock mass at Dongjianhkou,Shaanxi Province.From 30 to 596 m,20 valid data of horizontal principal stresses and 25 data of the directions of the fissure by the hydraulic fracturing technique are achieved;from 75 to 599 m,11 data of the maximum principal stresses by AE method are gained.Above 200 m,the data of the hydraulic fracturing technique is consistent with that of AE method at different points in the same depth;but below 200 m,the maximum horizontal stress by the hydraulic fracturing technique is 10 MPa larger than those by AE method.At the same time,the data are larger than those by the hydraulic fracturing technique in its neighbouring region.On the contrary,the data by AE method are consistent with it.The result is that the paleotectonic residual stress exists in granite rock mass below 200 m,and the geostress field is composed of the modern tectonic stress field and the paleotectonic residual stress field.The data by AE method are modern tectonic stress,but the data by the hydraulic fracturing technique are the geostress.The result shows that the paleotectonic residual stress is an important composition of the geostress in the Qinling—Bashan Mountain which is the Mesozoic-Cenozoic orogenic belt.
引文
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[10]安欧.构造应力场[M].北京:地震出版社,1992.(AN Ou.Tectonic stress field[M].Beijing:Earthquake Press,1992.(in Chinese))
[2]孟祥连,宋丙林,毛建安.西康线秦岭特长隧道地应力测试方法及其应用:铁路工程地质实例[M].北京:中国铁道出版社,2002:477-484.(MENG Xianglian,SONG Binglin,MAO Jian′an.Methods of geostress and its application to the Qinling extra-long tunnel district along the Xi′an—Ankang railway:cases of railway engineering geology[M].Beijing:China Railway Publishing House,2002:477-484.(in Chinese))
[3]肖本职,罗超文,刘元坤.鄂西地应力测量与隧道岩爆预测分析[J].岩石力学与工程学报,2005,24(24):4 472-4 477.(XIAO Benzhi,LUO Chaowen,LIU Yuankun.In-situ stress measurement and prediction analysis of tunnel rockburst in West Hubei[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(24):4 472-4 477.(in Chinese))
[4]钟作武,龚壁新,吕国湘.三峡工程地下厂房区域地应力测量与研究[J].长江科学院院报,1996,13(Supp.):17-19.(ZHONG Zuowu,GONG Bixin,LU Guoxiang.The geostress measurement and investigation in underground powerhouse,the Three Gorges Project[J].Journal of Yangtze River Scientific Research Institute,1996,13(Supp.):17-19.(in Chinese))
[5]丁原辰,张大伦.声发射抹录不净现象及其在地应力测量中的应用[J].岩石力学与工程学报,1991,10(4):313-326.(DING Yuanchen,ZHANG Dalun.Application of the incomplete erasion phenomenon in acoustic emission activities to the measurement of geostress[J].Chinese Journal of Rock Mechanics and Engineering,1991,10(4):313-326.(in Chinese))
[6]丁原辰.矿区地应力状态声发射粗估法及其应用[J].煤炭工程,1992,(4):50-56.(DING Yuanchen.Rock stress measurement by the AE method and its application to mine[J].Coal Engineering,1992,(4):50-56.(in Chinese))
[7]丁原辰,孙宝珊,邵兆刚,等.AE法油田最大主应力的测量及其与油产关系[J].岩石力学与工程学报,1998,17(3):315-321.(DING Yuanchen,SUN Baoshan,SHAO Zhaogang,et al.The major principal stress of oil field determined by AE and its relation to production[J].Chinese Journal of Rock Mechanics and Engineering,1998,17(3):315-321.(in Chinese))
[8]王连捷,李朋武,崔军文,等.中国大陆科学钻孔主孔声发射法现今地应力状态的确定[J].中国地质,2005,32(2):259-264.(WANG Lianjie,LI Pengwu,CUI Junwen,et al.Determination of the present crustal stress state by using acoustic emission in the main borehole of the Chinese Continental Scientific Drilling[J].Geology in China,2005,32(2):259-264.(in Chinese))
[9]李宏,张伯崇.北京房山花岗岩原地应力状态AE法估计[J].岩石力学与工程学报,2004,23(8):1 349-1 352.(LI Hong,ZHANG Bochong.In-situ stress measurement of Fangshan Granite[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(8):1 349-1 352.(in Chinese))
[10]安欧.构造应力场[M].北京:地震出版社,1992.(AN Ou.Tectonic stress field[M].Beijing:Earthquake Press,1992.(in Chinese))
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