Towards the development of integrated monitoring system for retreat mining operations

Abstract

Through cooperative research between the government, the private sector, mining companies and equipment manufacturers, considerable progress had been made during the last decade in studying the mechanics of strata failure and acquiring the knowledge needed to develop an integrated monitoring system for assessing local roof stability. Because of higher geotechnical risks in retreat mining operations, it was both important to develop panel layout designs that control convergence and stress and to monitor ground response during operations to verify designs and provide warning of impending stability problems. For detecting both localized roof stability problems and global overburden collapse mechanisms, the proposes an integrated panel-wide monitoring system which combines the capabilities of load rate monitoring of mobile roof supports (MRSs) with deformation measurements using an extensive array of sensors located near the mining face and throughout the panel. Two monitoring methods for the detection of localized roof stability problems have been evaluated on the basis of mine measurements and numerical modeling considerations. These are load rate monitoring of the hydraulic cylinders of mobile roof support (MRS) and re mote monitoring of roof movements. Analyses of field data in retreat sections show that roof instabilities are influenced by: (1) pillar failure, (2) pillar yielding, (3) mine seismicity (bumps), (4) geologic structures, and (5) panel layout designs and practice. Pillar yielding and unloading can be conveniently monitored by the load rate monitoring device, but to detect impending localized roof falls, additional ground deformation measurements are needed near the mining face. By increasing the number of deformation measurements in the entire panel, additional safeguards can be achieved for detecting overburden collapse mechanisms while continuously monitoring local roof stability close to the retreat line.