Underground » Strata Control and Windblasts
The application of seismic monitoring techniques in Australian coal mining has been tested by a seismic monitoring study carried out at Gordonstone Mine. The intention was to map the extent of fracturing associated with longwall mining in the German Creek seam. The monitoring system that was used employed three strings of triaxial borehole geophones as well as two surface seismometers. Acquisition hardware was developed for the project. Analysis was undertaken using commercial software.
More than 1,200 events were recorded over a two month period. The seismicity was strongly correlated with periods of longwall production and occurred mainly within the panel in an accurate zone about 70m wide extending from behind the face at the gateroads and up to 70m ahead of the face in the middle of the panel. The zone extended upwards ark over the face at an angle of about 50 degrees from the vertical. There was lesser activity to a depth of about 30m into the floor. The fracturing did not intersect the overlying tertiary aquifers.
A number of applications for seismic monitoring have been identified. These include caving issues associated with cyclic loading, face failures, gathered failures, failure in overlying massive units and floor failures with associated gas emission. Already a number of mines have started their own seismic monitoring. Seismic monitoring is also part of a major new ACARP and industry supported project on ground behaviour about longwall faces and its effect on mining.