When mining is carried out by the caving method, the roof of the empty area or the rock on the upper plate may fall. With the expansion of the goaf range, the range of slump and uneven subsidence will involve large rock masses, and the roadways will also be dragged to cause deformation and damage. In order to protect the wellbore, there is usually a pillar, but the size of the pillar may not be sufficient. If the rock stratum is inclined, and there is a good continuous inter-layer fault or mud layer, then after a large amount of goafing around the security pillar, the rock stratum on the pillar will slip and move along such discontinuous surface. It is possible that the wellbore will be damaged by the tie.
When the ground angle is large, the ground slope may also slip. If the slip surface passes through the wellbore, it will also damage the wellbore.
The root cause of the failure of the joint is the slippage and deformation of the rock caused by mining, which is different from the general ground pressure damage.
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