GIS BASED GEOSTATISTICAL ANALYSIS of FRACTURE DENSITY of GRANITE ROCK in BEISHan AREA GANSU PROVINCE

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.