At present, the understanding of the mechanism of impact ore pressure can be summarized as: strength theory, energy theory and impact tendency theory. Strength theory According to this theory, the harder top and bottom plates can clamp the ore body, and the coal body clamping hinders the unloading deformation of the deep ore body itself or the coal-surrounding rock junction. This impedance effect means that the lateral forces (frictional resistance and lateral resistance) parallel to the layer hinder the unloading movement of the ore body along the layer, making the coal body more compact, withstand higher pressure, and accumulate more Elastic energy. In the sense of limit equilibrium and elastic energy release, the clamping acts as a latch. Accordingly, the mechanical effects produced by the ore body clamping belt are: high pressure and storage of relatively high elastic energy; the high pressure zone and the elastic energy accumulation zone may be located near the mine wall. Once the high stress suddenly increases or the system resistance suddenly decreases, the ore body can suddenly break and move, throwing into the occupied space to form the impact rock pressure. Energy theory Soviet scholar c. T. Avilshen, and the British scholar Cook et al. in the mid-1960s proposed that the impactor pressure would occur when the energy released by the mechanical equilibrium of the ore body and the surrounding rock system was greater than the energy consumed. It clarifies the energy conversion relationship between the ore body and the surrounding rock, and the causes of the sudden destruction of coal and rock mass. Since the full stress-strain curve of the rock was obtained on a rigid press, it was revealed that the instability of the non-rigid press and the test piece system caused a sudden breakage of the test piece near the peak strength. In 1972, Black promoted it to the condition of impact rock pressure. It is considered that the rigidity of the mine structure (orbit) is greater than the stiffness of the mine load system (surrounding rock). This is also called the stiffness theory. In fact, it is also an energy theory that considers the energy stored in the system and the energy consumed by damage and motion, but this theory has not been fully confirmed, that is, it also occurs when the stiffness of the surrounding rock is greater than the stiffness of the coal. The impact of the mine pressure. Impact tendency theory The ability of a rock medium to produce impact damage is called an impact tendency. Thus, some experimental or measured indicators can be used to estimate or predict the extent of the impact of the mine pressure. The measure of this indicator is called the tendency of impact. The condition is that the actual impact tendency of the medium is greater than the specified limit value. These indicators mainly include: elastic deformation index, effective impact energy index, ultimate stiffness ratio, and failure rate index. Some scholars believe that this method can also be called the theory of impact tendency.
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May 04, 2023