Development of a roof-logging system by rockbolt drilling

Rockbolting has been tentatively introduced into some underground coal mines in Japan as a support system for entry roadways. For effective support it is important to gain an understanding of the geological and geomechanical conditions around the roadways - especially to obtain information about the boundary layers, changes in rock types and separation of the strata. Such data make it possible to select the optimal rockbolt type and length and bolting density. To obtain in-situ data before rockbolting a real-time logging system is being developed for implementation during drilling of the rockbolt holes and field trials with the prototype system were conducted in an underground coal mine. At present, the system for a small-size drilling and bolt-setting machine is composed of transducers for mechanical data acquisition and a data-logger with a memory card. The results of laboratory experiments, an outline of the roof-logging system and typical results of field tests are presented, and a method of data analysis is described that employs neural-network pattern-recognition algorithms.