【作者】 李亚萍；

【导师】 许建东；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2005， 硕士

【摘要】 发育于岩石中的天然裂隙几何学参数（密度、优势方位、长度、隙宽等）不仅是确定裂隙系统流体动力学的重要参数,而且也是大型工程施工和运行情况下稳定性分析中的重要考虑因素之一,一直以来倍受工程地质学家的重视。数十年来国内外学者分别采取构造地质研究（野外裂隙调查）、构造物理学的实验模拟和数值模拟试验与仿真等方法对岩石的裂隙几何学特征做了较为广泛而深入地研究,取得了丰硕的成果。 本文以我国高放废物处置库的重点预选区—甘肃北山旧井地段板滩单元花岗岩中发育的构造裂隙（主要指节理）为研究对象,通过现场野外调查测量,结合已有的区调成果和钻孔详细的裂隙分析资料,运用传统的概率统计方法和分形理论,在ArcGIS平台下对裂隙几何学要素（长度、方位、密度等）进行统计、计算和分析,研究花岗岩岩体中裂隙的分布特征,对裂隙的几何学参数予以定量描述,为核废料处置库的选择提供必要的基础数据。同时,把裂隙密度和裂隙网络的空间结构结合,对甘肃北山花岗岩的岩体工程质量进行初步评价。论文所取得的成果如下: 一、获得单个裂隙的几何学参数 对研究区花岗岩体地表露头中发育的构造节理进行数字测量与调查,共获得露头区五个测点、328m²数字化的二维裂隙空间分布图像。同时对裂隙图像进行几何变换和矫正处理,在Mapinfo平台下以人工目视判读、解译为基础,经配准、数字化获得数字化裂隙网络图。 根据甘肃北山区域裂隙发育状况,结合野外裂隙实地调查结果、钻孔裂隙特征,在ArcGIS平台下运用SQL查询语言进行裂隙分组、统计、计算,获得单个裂隙的几何参数,相关主要研究成果如下: 1.节理裂隙的长度分布具有不均匀性和方向性。优势方向上裂隙的总长度也呈现优势增长。裂隙长度变化并不是无规则的,而是连续的;当采样面积较大、裂隙数量较多时,裂隙长度分布可以用指数函数y=ce^kx来拟合;裂隙长度集中在0.5m～4m之间,其比例占到95%以上。裂隙长度概率密度函数符合幂函数分布;在不分组的情况下,长短裂隙的比例在1～2之间。更多还原

【Abstract】 Geometrical parameters of fractures developing in natural rocks, such as density, dominant orientations, length, fracture aperture, are long recognized by engineering scientists because they are not only important parameters to fluid dynamics of fracture systems but also main considering factors for large-scale projects during construction and stability analysis. In several decades many scholars have made wide and deep research to fracture geometrical parameters using tectonic geology, tectonophysical test simulation and numerical experimentation and emulator and obtained abundant results.In this thesis, as a candidate area for high level waste repository (HLW) in China, the rock mass fracture system of the Bantan unit granite of the Jiujing block the Beishan area in Gansu province, is chosen as the study object. The fracture system is studied in detail by field survey bedrock outcrop fractures surveying and combining completed regional geological survey results with acoustic borehole television measurements. Traditional probabilistic statistics and the fractal theory are used to analyze fracture geometric parameter including fracture length, azimuth and density . Statistics and calculation using the ArcGIS software is made to study fracture distribution characteristics in the granite rock mass.Quantitative description is performed to fracture geometrical parameters in order to provide necessary basic data for the selection of HLW. In the same time combining fracture density with fracture network spatial structure, using RQD and fractal dimension the quality of rock mass of the Bantan unit granite is assessed.The result is of this thesis are as follows:Firstly, fracture geometrical parameters are obtained by statistics on ArcGIS.Using numeral camera I investigate tectonic joints developed in the Bantan unit granite rock mass. Five specimens including 328 square meters of digital planar fracture images were finished. Then by geometrical transform and rectification disposal, manual judgments, interpretation, digitalization, fracture network digitalized map can be obtained. According to regional conditions for fracture development,combined with outcrop field fracture survey results and borehole fracture features, fractures are grouped, counted and calculated by Select Query Language (SQL.) in ArcGIS software.Fracture length distribution is inhomogeneous and anisotropic. Total fracture length of preferential orientation show rapid increasing. Fracture lengths change continuously. When the sampling area is bigger and the fracture number is large, fracture lengths accord with an exponential function. Fracture lengths mostly fall between 0.5 and 4 meters and their proportion reaches 95 percent. The probability density function of fracture lengths follows a power function. The proportion of long and short fractures is between 1 and 2.Fracture planar density reflects fracture developing degrees on a rock cross section. Its value is related to fracture number and size. Bigger density indicates well developed fractures. Two of 5 specimens are 4.642 and 4.113 in density, respectively, the others change near 3.Fracture permeability ratio is directly proportional to the cube of fracture aperture. So fracture aperture distribution is very important to study fracture permeability. By the statistics and analysis of outcrop fractures, it is found that the fracture aperture between 0.1 to 0.3 centimeter accounts for 78%, that between 0.3 and 0.5 centimeter is 12%, and greater than 1 centimeter is less than 5%. According to the description recommended by ISRM, the fractures of the Bantan unit granite of the beishan area mainly belong to the open-rupture type.Joint statistics is characterized by sizes effect. Different size of survey grids bring about distinct statistical results. This work chooses the sample of No.3 borehole-3 to simulate that fracture geometrical parameters are characterized by orientations and sizes when the of survey grid changes. Analysis result shows that the relatively increasing mode of fracture lengths fits the exponent function y=ce x whatever the measuring size is. With increasing of the survey size the length increasing trend becomes slow. The total characteristics of fracture density are from small-scale unstable change to large scale gradual steady. Survey orientations affect strongly calculated results.Secondly, spatial structure of fracture network is studied by the fractal theory. On the basis of box-counting dimension, a simple way to calculate fractal dimension is developed on the fracture network map of Beishan. The result shows that spatial structure of the fracture system is fit for fractal distribution within the range from 10 centimeters to 200 centimeters. At the same sampling site fractal dimensions of fractures in different group vary for different fracture developing degrees. While in the different survey places, because of varied survey grid sizes, fracture numbers, fracture lengths, fracture azimuths and fracture developing degrees fractal dimensions present different values. Fractal dimensions of two sites with relatively well developed fractures are big, separately 1.724 and 1.636. The other three of five average about 1.6.Many natures of rock mass fractures have fractal features to some degree, but their fractal properties are not often strict rather in a statistical sense. So, different measure areas correspond to obviously distinctive results. The research results are not comparable with each other. How to define the scale invariant section deserves deep investigation. This work seeks for a brief way to solve this problem.Fractal dimensions indicate complexity of fracture networks. A lot of impact factors have effects on their values. From the six aspects such as planar density, fracture number, fracture size, fracture predominant orientation, the ratio of long and short fracture, and area of survey grid, I think fore-three items affect obviously, in which density is related to linear correlation coefficient R up to 0.914.Finally, the rock mass engineering quality of the Bantan unit granite is appraised by RQD (Rock Quality Designation) and the fractal method.RQD (Rock Quality Designation) judges the good and bad rock mass qualities by intact degrees of drilling core and classifies rock mass. Using finished drilling data I analyze RQD of BSOl and BS03 and conclude that RQD of BSOl is between 75% and 100% accounts up 75.84%, and averages 74.4%. The RQD of BS03 is generally big. So, the engineering quality of the Bantan unit granite borehole belongs to the good class with intact core.Fractal dimensions not only describe fracture number of rock mass but alsoreflect homogeneous degree of fracture distribution and the intact and cracked conditions. So rock mass quality classified by fractal dimensions combined with RQD is more objective and efficient than single RQD index. Above research indicates that the fracture network is characterized by fractal distribution. Fractal dimensions of five sampling sites are in turn 1.636, 1.548, 1.596, 1.724, and 1.604, respectively, and fall into between 1.5 and 1.75. According to the rock mass quality classified by fractal dimensions, the Bantan unit granite belongs to rock mass with fracture well developed and normal quality.更多还原