Calculation of direct roof subsidence of retracement channel and analysis of its influencing factors

The direct roof subsidence of retracement channel is of utmost importanie to the withdrawal of equipment in the final mining stage.Based on the basic roof fracture position, a mechanical model of the direct roof deflection of the withdrawal channel after penetration was established.The expression of the supporting stress was simplified to the n-th parabolic function of x fitted to it.The value of n varies with the fracture position, the expression of the direct roof subsidence at the center line of the roof of the retreat channel was derived.The basic roof fracture position d of 312 working face was about 12 m, at this time n was taken as 4, and the direct roof subsidence was about 105 mm.On the basis of theoretical calculations, the factors affecting the direct roof subsidence were analyzed.The results showed: The direct roof subsidence increases with the increase of the basic roof fracture location, coal seam depth, stress concentration coefficient and the span of the retreat channel, and decreases with the increase of the direct roof thickness and elastic modulus.The influence of other factors is not significant.Under the condition of ensuring the equipment withdrawal space, the span of the withdrawal channel should be reduced as much as possible to control the direct subsidence of the withdrawal channel.