On the basis of summarizing the above hypotheses, and on the basis of mass production practice and on-site observation of rock mass internal movement, Chinese scholars proposed the mechanical model of “masonry beam†of rock mass structure in the late 1970s and early 1980s. The above related hypothesis.
The hypothesis says:
In addition to the formation of “three belts†(falling belts, regular moving belts and curved sinking belts), in the overlying strata of the stope, in the regular moving belt and above, the fractured rock blocks may form a shape such as a beam. In fact, it is the structure of the arch.
Because the rock blocks are arranged like "masonry", they can be called masonry beams.
This structure is supported by the “ coal wall – bracket – goaf degraded vermiculiteâ€. Due to the existence of this structure, the overlying strata in the mining direction can be divided into three zones: coal wall support affected zone, separated layer Zone and re-compact zone.
And assume:
1. The rock mass structure of the overlying strata is mainly composed of each hard rock layer.
To this end, the overburden can be divided into several groups, each group with a hard rock layer as the bottom layer.
2. The soft rock formations in each group can be considered as loads of hard rock formations, and in many cases it will follow the movement of hard rock formations.
3. Due to the impact of mining, the hard rock formation has broken into a well-arranged rock mass.
4. Since the friction between the layers cannot block the rotation and horizontal movement of the rock block, it can be assumed that the soft rock layer is regarded as an infinite number of vertical rods, that is, only the vertical load can be transmitted, and the horizontal force cannot be prevented.
5. When the rock mass returns to the horizontal position by the rotation, the shear force between the blocks becomes zero again. For this reason, the later rock blocks can be replaced by a horizontal link.
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