Yoshihisa Ichihara

Coal Mining Technology. Visualization System for Roof Rock using the Mechanical Data of Roofbolter.

It is important to obtain information about geostructure of roof rock for effective rock bolting at the roadway in underground coal mine. Information on the variation in rock types and the distribution of discontinuities, such as layer boundaries, separation of strata and cracks, is especially important. For in situ evaluation of roof rock, we developed a measurement-while-drilling (MWD) system using mechanical data obtained from a drilling machine. The hardware of this system detects the torque, thrust, revolution and stroke of the machine as the mechanical data, and the software analyzes the mechanical data log and displays the locations of discontinuities by Neural Network techniques. This system also enables estimation of the 3-D geostructure of roof rock with regard to the change in rock types and distribution of discontinuities in the case of an array arrangement of drill holes. For displaying images inside the 3-D geostructure, animation consisted of slicing images and/or a 3-D model describing the boundary plane of layers by VRML(virtual reality modeling language) in virtual space are employed. We conducted some feasibility studies of this system using a pneumatic and a hydraulic drilling machine in roadways of Taiheiyo Coal Mine, Japan. The results of feasibility studies confirmed that the 3-D geostructure, including the distribution of crack density, can be reconstructed by the analysis system. Animation and display by VRML for the 3-D geostructure were useful for understanding inner structure of rocks.