7-1 Classification of Longwall Mining Techniques [1]

Longwall mining techniques, In accordance with the production capacities [2] and the technico-economic conditions, can usually be classified into three types.

A. The drilling and blasting mining [3]: it is the oldest mining technique. Nowadays, the technique and equipment of drilling and blasting mining has been improved. The three kinds of new techniques, the millisecond blasting [4], the individual hydraulic props [5] and the large power chine conveyors, have been spreaded and applied in the drilling and blasting faces.

B. The mechanized mining [6]: the mechanized mining

characterized by using the shearer or plow [7], integrally removable chain conveyor and hydraulic props.

C. The fully mechanized mining [8]: the fully mechanized mining face consists of shearer or plow, armored face conveyor (AFC) [9], powered supports, and stage loader [10] and belt conveyor [11] in the headentry.

7-2 The Operated Procedures in a Fully Mechanized Face

Coal at longwall face is cut by either a shearer loader or a plow . The shearer loaders generally ride on the panline [12] of an armored face conveyer (AFC), which is laid on the floor parallel to the faceline [13]. The shearer loader moves by means of a self-contained motorized winch [14] running along a static chain whose ends are anchored at the ends of the face near or at the drive units of the AFC. In the recent models, the shearer loaders are self-propelled along a special track without the aid of the chain. Thus the AFC serves as the track for the cutting machine to move on and as a guide to hold the machine in place.

Single or double drums similar in some respect to those used in continuous miners but larger in diameter are mounted on the face side of the shearer loader. The cutting position of a drum can be fixed or hydraulically adjusted by the ranging arms. The cutting force [15] is provided by the rotating torque available at the axis of the drum. The widths of cuts or webs made by shearer loaders are about 20-36 in. (0.50-0.91m) wide. A plow is generally mounted on the face side of the AFC and pulled by a continuous chain enclosed in a special guide channel [16] on either the face side or the gob side of the armored face conveyor. The continuous chains is powered by two drive units located at both ends of the face. The cutting force is provided by the continuous chain that pulls the plow. The widths of cut for the plow range from 2 to 7 in.(0.05-0.18m) .

Coal cut by the shearer or plow is loaded onto the AFC and transported to the headentry T-junction [17]. A T-junction is the intersection of the longwall face and the headentry or tailentry. At the headentry T-junction, coal is dumped onto a stage loader, which in turn empties to the entry belt conveyor some distance outby the T-junction. A stage loader is a chain conveyor

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