Analysis on fractal mechanics and simulation of roof pre-splitting blasting in shallow depth coal mining face

Accoding to a pre-stilting blasting of the straght line boreholes aplid to No.621-02 shallow depth coal mining face in Nalinmia No. 2 Mine,when aprimary breaking ofthe basic of ocured a serious mine pressure behavior phenomenon would ocur.Based on the analysis of the pre- s litig blasting mechanismof the roof and the fractal geomery thaory of the blasting borehole layut.the fractal dimension expression of the different blasting borehole layout mode was providedThe fractal dimension of the deia layout blasting boreholes was calculated as 1.15 and was obviously igher than the fractal dimensionof thestraght line layout blastng boreholes as1.0.Therefore,the pre- pliting blasting iproved plan with the deta layout blasting boreholes was provided.The fnte element nonlinea dynamics software LS- DYNA was applied to the numercal sinulation analysis on the Mises stress evoludion aw ofthe two blasting plans.The resuts showed that the wrk efifc ofthe reflecion stress wave for the improved plan woult be better and the attenuation of the stress wave would be more slovw and favorable to the blasting energy tofulybreak the rocks.