ABSTRACT
At the beginning, the coal and rock is in thermodynamic equilibrium state, once rock drift was excavated, this state of equilibrium will be destroyed, into a new kind of non equilibrium state[3]. If the rock drift is a circle, its external force equation (1):
σ γ H (1)
In the equation (1): σ
∞ —Infinity static level pressure;
γ —Specific gravity of rock; H-Buried depth of rock drift.
