LiDAR mapping of ground damage in a heading re-orientation case study

The Subtropolis Mine is a room-and-pillar mine extracting the Vanport limestone near Petersburg,Ohio,U.S.In February of 2018,mine management began implementing a heading re-orientation to better control the negative effects of excessive levels of horizontal stress.The conditions in the headings improved,but as expected,stress-related damage concentrated within crosscuts.The mine operator has worked to lessen the impact of the instabilities in the outby crosscuts by implementing several engineering controls.With the implementation of each control,conditions were monitored and analyzed using observational and measurement techniques including 3D LiDAR surveys.Since the heading re-orientation,several 3D LiDAR surveys have been conducted and analyzed by researchers from the National Institute for Occupational Safety and Health(NIOSH).This study examines(1)the characteristics of each 3D LiDAR survey,(2)the change in the detailed strata conditions in response to stress concentrations,and(3)the change detection techniques between 3D LiDAR surveys to assess entry stability.Ultimately,the 3D LiDAR surveys proved to be a useful tool for characterizing ground instability and assessing the effectiveness of the engineering controls used in the heading re-orientation at the Subtropolis Mine.

Evaluation of stress-control layout at the Subtropolis Mine,Petersburg,Ohio

The Subtropolis room-and-pillar mine extracts the Vanport Limestone(Allegheny Formation,Pennsylvanian System)near Petersburg,Ohio.Strata instability problems associated with excessive concentrations of lateral stress caused the mine operator to implement a change in layout design.This mining method has been identified as a stress control layout and has been used by other underground stone mines in the past with varying degrees of success.Practical experience has shown that entry headings advance in the direction of the principal lateral stress,producing lower stress concentrations with better mining conditions.It is important to minimize stress concentrations along the mining front,so an arrowshaped advance is recommended.This technique advances more developments(headings)in a"good"direction and reduces developments(crosscuts)in the"bad direction."As is expected,the stress control layout enhances the potential for shear failures in crosscuts.It is,therefore,important to focus crosscut engineering interventions that either:(a)lower stress concentrations(for example,an arched roof)or(b)enhance strength of the strata containing the shears(for example,rock reinforcement).This study focuses on observing strata conditions on a regular basis and monitoring the response of these strata to changing geologic and mining conditions through 3D Dynamic LiDAR scans.