Using intelligent inclined borehole optical imager to interpret geometrical characteristics of fractures in crystalline rock mass

With the characteristic of high digital record and by overcoming a series of problems in the process of engineering drilling, such as discontinuity in drilled cores, missing information of fracture geometric elements and so on, the technology of intelligent borehole optical imager is widely used in engineering investigations all over the world. However, at present the technology is mostly used for vertical boreholes, less for inclined ones. Combined with the results of the inclined boreholes applied with the technology of intelligent borehole optical imager, which come from the project on gas storage in underground caverns with groundwater in a certain region, this paper introduces the interpretation approach of the fractures derived from the results of inclined boreholes recorded by means of intelligent borehole optical imager. The approach can convert the apparent occurrence of discontinuities to the real occurrence with the method of spatial coordinate transformation. A statistical analysis on the geometric elements of the fractures in deep crystalline rock mass under the condition of the development of fractures in the vicinity of the storage caverns and water curtain system is made. The characteristics in the occurrence and in the vertical direction of the development in fractures are examined. The results indicate that fractures originated from the tectonic movement develop in a superior position with a strike of NE20°~40° and NW20°~40°, the trend in the quantity of the fractures is that decreases at first, then increases gradually and at last stays at a stable state. The resluts can provide reliable data for evaluating the stability of the surrounding rock of caverns and the effect of the water curtain system that prevents gas leakage.