Underground Coal mines generally use Bord and Pillar method for mining coal. In Bord & Pillar method set of rooms (these rooms are referred as bords or gallery) are developed in chess board pattern leaving massive pillars in between the bords for holding the roof. Dressing is common method used to bring down loose coal material from roof at regular intervals.
(refer videos at https://drive.google.com/open?id=1RYsVCtx7FIljosEYg_IMPjnjX33K5awf )
Bord and pillar mining method comprises two phases, i.e. development and depillaring. In the development phase, a series of narrow roads known as “bords” or “galleries” are progressed into the coal seam parallel to each other along the dip direction which are cut across at right angles by another series of roads driven along the strike. In depillaring stage, coal from pillars formed are extracted.
One of our underground coal mines, uses Bord & pillar method of mining at a depth of 500 metre below surface where gallery needs to be continuously progressed for pillar formation and depillaring. Currently, Dressing activity is performed manually, which can potentially be a very unsafe for the people carrying out dressing activity.
Hence, we are looking for mechanised dressing system for our underground coal mine. One of the options could be mobile robots with the ability to sense the crack, decode the crack type & its category and take appropriate decision for dressing down activity.
Underground coal mining process includes 3 broad operations – mine development, coal extraction and Loading & Conveying coal.
Coal by nature creates sedimentary rock with shale and sand stone. These sedimentary rocks in roof create cleats and cracks naturally or due to mining. With time, moisture and air contact these cracks and cleats loosen which creates safety risk as these loose parts can come down and injure someone.
So, Dressing activity is done by skilled and experienced human dresser carefully. Presently, human dresser uses 6 feet length hexagonal mild steel 25mm crow bar (crow bar is a metal bar with a single curved end & flattened points used for break and remove rocks) or ½ inch diameter Galvanised Iron pipe of 10 feet length tipped with crow bar as a tool for dressing the roof which is generally at a height of around 8 to 10 feet. Dressers and supervisors follow SOP but there is always a scope of misjudgement of cracks and injuries may happen to workers. Hence, we want to use mechanised dressing system. This system should be equipped with crack detector sensor guns to decode the crack type and use advanced data analytics to derive decisions for dressing down activity. This system may use existing crow bar or galvanized iron pipe or some other extensible hands with sharp edge pressure for dressing.