Design of a Mine Roof Strata Analyis Device

Abstract

Because the roof lithology in an underground coal mine is typically variable and poorly known, the safety and efficiency of these mines is reduced. To address this shortcoming, a device for analyzing rock properties by way of scratching a mine roof borehole was designed and tested in multiple different media with the goal of determining in situ mine roof properties with a nondestructive technique. Tools were developed for measuring extraction force and position of the scratching mechanism and those values were compared versus time for multiple tests to look for changes in applied force over changing positions. Because of signal stability and inconsistencies in scratch depths the data were found to contain too much variation to determine any rock properties or changing rock conditions from the simulated roof material in the concrete block. However, further scratch tests in a sandstone block indicated that increasing the diameter of the wire scratchers (and therefore increasing their stiffness and accompanying normal force) from 0.045 inches to 0.055 inches increased the average pull force from 6.24 to 9.96 lbs. Similar to that test, a scratch test was performed in a PVC pipe where it was found that increasing the scratcher diameter from 0.045 inches to 0.051 inches increased the pull force from a 2.81 lb average to a 36.46 lb average, with considerably better gouging of the host material.