关键词: 岩体裂隙, 分维, 裂隙几何学参数, 甘肃北山

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 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 in the Beishan area, Gansu province, is chosen as the study object. The fracture system is studied in detail by field bedrock outcrop fractures surveying and combining the completed regional geological survey results with acoustic borehole television measurements. Traditional probabilistic statistics and the fractal theory are used to analyze the fracture geometric parameters including fracture length, azimuth and density. Statistics and calculation using the ArcGIS software are made to study fracture distribution characteristics in the granite rock mass. Quantitative description of fracture geometrical parameters is performed in order to provide necessary basic data for the selection of HLW. In the same time, by combining fracture density with fracture network spatial structure and using fractal dimension, the quality of rock mass of the Bantan unit granite is assessed. Fractal dimensions not only describe fracture number of rock mass but also reflect 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 the range 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.

Key words: fracture, fractal dimension, fracture geometrical parameter