Suspension

When roadways are excavated in underground coal mines, the laminated immediate roof tends to detach from the main strata. Suspension theory assumes that the immediate roof of the excavation is weak whereas the upper layer is relatively stronger. In such situations, rockbolts hold the immediate roof to the self-supporting main roof via transmitting the dead weight load of the strata between face plates and anchors to the main roof. Figure 9 shows the weak roof strata suspended to the competent strata. It is required that the bolt should be long enough to anchor into the stable rock and that bolts should hold sufficient tensile strength to maintain the rock dead weight.

suspension
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