基于GIS的甘肃北山花岗岩裂隙密度地质统计分析
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摘要
以甘肃北山花岗岩中发育的构造裂隙(主要指节理)为研究对象,采用高精度GPS、罗盘等对其进行现场测量,获取裂隙的迹长及产状信息,并将信息导入ArcGIS平台建立裂隙属性数据库;进而应用地质统计分析理论,以裂隙面密度P21为地质统计分析的区域性变量,探索花岗岩岩体裂隙空间分布特征;然后借助ArcGIS软件平台建立变异函数模型,利用地质统计学的普通克里金插值方法得到整个区域的面密度预测分布图。结果表明:芨芨槽块段所测某区域裂隙面密度值的半变异函数变程值在20～30m之间,NS和EW方向有明显差异,由此知该区域裂隙面密度分布具有显著空间自相关性,但分布特征不均匀;此结论对北山花岗岩裂隙空间分布特征的深入研究以及三维裂隙网络建模具有重要参考价值。
Geometrical parameters of fractures such as joints in natural rocks are important parameters in fluid dynamics of fracture systems,and are also mainly considered factors for the stability analysis of large-scale projects during construction.Therefore,the importance of these parameters has been fully recognized by engineering scientists.The Jijicao block of the Beishan area in Gansu province is chosen as the studied area in this paper.It is a candidate area for high level waste repository in China.The paper chooses the rock mass fracture system of the granite in Jijicao block as the study object.The trace lengths of fracture system are measured by GPS-RTK technique in detail.The occurrence of the bedrock outcrop fractures is surveyed with compass.Then the ArcGIS software is used in the data statistics and calculation and also applied to studying fracture density in the granite area in the Jijicao block.Finally,geostatistical analysis is used to study the spatial autocorrelation and variability of fracture density.By this way the spatial distribution characteristics of fracture can be recognized.The research results indicate that the fracture density has a strong spatial autocorrelation.Variogram analysis demonstrates that P21 values become antocorrelated at a step of about 20～30m.The difference between the ranges of NS and EW demonstrates that there is heterogeneity in the spatial distribution of fractures.At last the prediction map of P21 value is obtained with the method of ordinary kringing interpolation method.
Geometrical parameters of fractures such as joints in natural rocks are important parameters in fluid dynamics of fracture systems,and are also mainly considered factors for the stability analysis of large-scale projects during construction.Therefore,the importance of these parameters has been fully recognized by engineering scientists.The Jijicao block of the Beishan area in Gansu province is chosen as the studied area in this paper.It is a candidate area for high level waste repository in China.The paper chooses the rock mass fracture system of the granite in Jijicao block as the study object.The trace lengths of fracture system are measured by GPS-RTK technique in detail.The occurrence of the bedrock outcrop fractures is surveyed with compass.Then the ArcGIS software is used in the data statistics and calculation and also applied to studying fracture density in the granite area in the Jijicao block.Finally,geostatistical analysis is used to study the spatial autocorrelation and variability of fracture density.By this way the spatial distribution characteristics of fracture can be recognized.The research results indicate that the fracture density has a strong spatial autocorrelation.Variogram analysis demonstrates that P21 values become antocorrelated at a step of about 20～30m.The difference between the ranges of NS and EW demonstrates that there is heterogeneity in the spatial distribution of fractures.At last the prediction map of P21 value is obtained with the method of ordinary kringing interpolation method.
引文
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[15]Dershowitz William,Herda Hans H.Interpretation of fracturespacing and intensity.U.S.Symposium on Rock Mechanics.1992,757.
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[18]Dae S.Young,Steven F.Hoerger.岩体裂隙的空间变化性和地质统计学模型[J].地质科技情报,1988,7(1):110～115.Dae S.Young,Steven F.Hoerger.The spatial variation andgeostatistical model of rock fracture.Geological Science andTechnology Information,1988,7(1):110～115.
[19]Raymond Munier,Svensk Krnbrnslehantering AB.StatisticalAnalysis of Fracture Data,Adapted for Modelling DiscreteFracture Networks-Version 2.SKB R-04-66,2004,8:20～47.
[2]Priest SD,Hudson J.Discontinuity spacing in rock.Int.J.RockMech.Min.Sci.,1976,13:135～148.
[3]Kulatilake PHSW,Wu TH.Estimation of mean trace length ofdiscontinuities.Rock Mech.Rock Eng.,1984,17:215～232.
[4]Dershowitz WS,Einstein HH.Characterizing rock joint geometrywith joint system models.Rock Mech.Rock Eng.,1988,21:21～51.
[5]Chile's JP.Fractal and geostatistical methods for modelling of afracture network.Math.Geol.,1987,20:631～654.
[6]Ayalew L,Reik G,Busch W.Characterizing weathered rock masses-A geostatistical approach.Int.J.Rock Mech.Min.Sci.,2002,39:105～114.
[7]Rafiee,M.Vinches.Application of geostatistical characteristics ofrock mass fracture systems in 3D model generation.InternationalJournal of Rock Mechanics&Mining Sciences,2008,45:644～652.
[8]张仁铎.空间变异理论及应用[M].北京:科学出版社,2005.Zhang Renduo.Spatial Variability Theory and Applications.Beijing:Science Press,2005.
[9]徐建华.现代地理学中的数学方法(第二版)[M].北京:高等教育出版社,2002.Xu Jianhua.Mathematical Methods in Modern Geography(secondedition).Beijing:Higher Education Press,2002.
[10]杨继红,刘汉东,等.考虑土性参数空间变异性的边坡可靠度分析[J].工程地质学报,2007,15(2):205～211.Yang Jihong,Liu Handong,et al.Reliability analysis of slopestability taking into consideration of spatial variability of soilparameters.Journal of Engineering Geology,2007,15(2):205～211.
[11]张先伟,孔令伟,郭爱国,拓勇飞.湛江强结构性黏土的物理力学性质指标及相关性分析[J].工程地质学报,2011,19(4):447～454.Zhang Xianwei,Kong Lingwei,Guo Aiguo,Tuo Yongfei.Physical and mechanical indexes and correlation analysis of claywith noticeble structures in Zhanjiang area.Journal ofEngineering Geology,2011,19(4):447～454.
[12]王华敬,胡应德,吴光先.固结系数的空间变异性对一维固结的影响分析[J].工程地质学报,2006,14(5):627～631.Wang Huajing,Hu Yingde,Wu Guangxian.Influence of thespatial variability of the coefficient of consolidation on the one-dimensional consolidation of soft soils.Journal of EngineeringGeology,2006,14(5):627～631.
[13]卢永森.GPS-RTK在地质测绘应用与探讨[J].现代测绘,2010,33(3):31～33.Lu Yongsen.Application and discussion about GPS-Ptk ingeological mapping.Modern Surveying and Mapping,2010,33(3):31～33.
[14]汤国安,杨昕.ArcGIS地理信息系统空间分析实验教程[M].北京:科学出版社,2006.Tang Guo'an,Yang Xin.The ArcGIS Experimental Course ofSpatial Analysis about Geographic Information System.Beijing:Science Press,2006.
[15]Dershowitz William,Herda Hans H.Interpretation of fracturespacing and intensity.U.S.Symposium on Rock Mechanics.1992,757.
[16]李晓昭,周扬一,等.测量统计范围大小对结构面迹长估计的影响[J].岩石力学与工程学报,2011,30(10):2049～2056.Li Xiaozhao,Zhou Yangyi,et al.Effects of measurement rangeon estimation of trace length of discontinuities.Chinese Journal ofRock Mechanics and Engineering,2011,30(10):2049～2056.
[17]Esri Support Center.How Spatial Autocorrelation:Moran's I(Spatial Statistics)works.2009,1.http:∥webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How%20Spatial%20Autocorrelation:%20Moran's%20I%20(Spatial%20Statistics)%20works.
[18]Dae S.Young,Steven F.Hoerger.岩体裂隙的空间变化性和地质统计学模型[J].地质科技情报,1988,7(1):110～115.Dae S.Young,Steven F.Hoerger.The spatial variation andgeostatistical model of rock fracture.Geological Science andTechnology Information,1988,7(1):110～115.
[19]Raymond Munier,Svensk Krnbrnslehantering AB.StatisticalAnalysis of Fracture Data,Adapted for Modelling DiscreteFracture Networks-Version 2.SKB R-04-66,2004,8:20～47.