HIGH WALL MINING PRATEEK SHARMA B.TECH MINING II YEAR UNIVERSITY OF PETROLEUM AND ENERGY STUDIES (UPES)

INTRODUCTION High wall is the unexcavated face of exposed overburden and coal in a a surface mine. High wall mining is a remotely operated mining method to extract coal from thin seams or underlying seams in the high wall. In this method extraction of coal is done from a series of parallel entries driven in the seam from the face of the high wall without roof support. This technology provides an economical way to extract coal reserves locked up in the high wall.

APPLICABILITY OF THE TECHNOLOGY When the open pit mining has reached beyond the stripping ratio or the limit of mining operations. When coal is present in thin seams for which no conventional mining method is available or economically viable. Can be applied where coal is present in the boundaries. The seam should be flat ( -5 to 8 degree). Coal seam thickness should be thicker than 80cm.

EQUIPMENTS USED Continuous miner machine Push beams Cutter unit Conveyor Generator Anchoring system

Recovery Rate SHM vs Auger 60% 30% 300 m = 100% 150 m= 50% SHM 60% Auger 15% 4x

AUGER DISADVANTAGES OVER HIGH WALL MINING Diminishing power with increased depth. Fixed cutting height that diminishes the coal size degradation and depth. Rigid structure of the auger drill due to which no ability to negotiate dip in the seam. Low production rate.

METHODOLOGY In high wall mining the coal seam is penetrated by a continuous miner propelled by a hydraulic push beam transfer mechanism. Cycle includes sumping (launch pushing forward) and shearing (raising and lower the cutter head boom to cut the entire height of the coal seam). The push beam transfer mechanism (PTM) automatically inserts a 6.01m long rectangular push beam (screw conveyor segment) into the center section of the machine between the power head and the cutter head.

The push beam system can penetrate nearly 300m into the coal seam. High wall mining system use auger enclosed inside the push beam that prevent the mined coal from being contaminated by rock debris during the conveyance process. Using a video imaging and/or a gamma ray sensor and/or other geo radar system like a coal-rock interface detection sensor the operator can see ahead projection of the seam rock interface and guide the continuous miner’s progress.

Contour mining

CONTINUOS MINER USED FOR HWM Length base = 16-17 m Width base = 8-9 m Weight = 225 ton Length of push beam = 6m 50 push beams per miner Weight of push beam = 5150 kg

THE MACHINE CUTTERHEAD MODULE

PUSHBEAM(FRONT) PUSHBEAM (BACK)

PUSHBEAM Push beam plays an important role for parallel drivage of entries. It contains two contra-rotating augurs for transportation of coal from the coal face. It allows the cutter head to negotiate the undulating contour of the coal seam. Normal length of push beam is about 6.0 m.

ADVANTAGES OF HIGH WALL MINING Coal which is blocked in high wall can be recovered at reasonable cost. Maximum conservation of coal No man power is required to enter into the entries made by high wall miner, hence this method is good from safety aspect. Operation is unmanned and remote. Operates with 4-5 worker per shift. Upto 65% coal recovery is achieved. Low establish cost.

LIMITATIONS The roof and floor should be strong. Length of push beam is generally 300m. Their should not be geological disturbances such as faults.

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