A research team led by Kang Song Il, a researcher at the Faculty of Mining Engineering, has developed a load cell capable of precisely measuring mechanical properties of coal faces in full consideration of the effect of eccentric load in order to explain ground pressure characteristics.
The load cell consists of an elastic body and a resistance wire sensor.
The elastic body consists of four beams whose two sides are fixed and each beam has two resistance wire sensors on both sides. A total of 16 resistance wire sensors form a bridge circuit.
As four resistance wire sensors are connected in series on each branch of the bridge circuit, different deformations generated from them do not affect the overall measurement results. Instead, only total resistance change generated on the four resistance wire sensors is related to the measurement results.
The load on the elastic body is represented as the change of the sensor as it is transferred to the resistance wire sensor. Resistance values are calculated from the relationship between the resistance and the change, and displayed as resistance values in the multi-channel measuring device.
The load cell is installed in the support of a coal face. Vertical load is measured by a ground pressure meter between a beam and a middle support, which is set up in the middle of a beam of the support, while side load is measured by the meter in a lagging, which is set up between a coal wall and a bridge of the support.
The ground pressure characteristics in an area can be figured out by the properties of a certain area obtained in a mathematical method from measured values and the properties of known areas.
This device is helpful to get a correct description of ground pressure characteristics found in all kinds of coal mines and faces in different geological conditions, and to measure precisely the mechanical properties of corresponding rock mass such as cohesion, angle of internal friction and Poisson coefficient, which makes it possible to establish suitable methods of supporting mines. It will lead to a significant reduction in the consumption of materials such as supports, and safe working conditions and stability of coal production.
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