Study On The Influence Of The Propulsion Speed Of Fully Mechanized Caving Face On The Mining Stress And The Mechanical Characteristics Of Coal Sample

With the continuous increase of mining intensity and mining depth,the damage trend of loading and unloading caused by mining in working face is becoming more and more serious.In this paper,based on the fully mechanized top-coal caving mining at B3+6 coal seam+425 level in the south area of Wudong Coal Mine,theoretical analysis,numerical simulation,mechanical test of coal samples and other research methods are used to study the evolution law of mining stress under the influence of advancing speed,and analyze the mechanical characteristics of coal samples under the mining action of steeply inclined coal seam.Based on the theoretical formula of loading and unloading stress of single mining and drawing in fully mechanized top coal caving face,it is concluded that there is a positive correlation between loading stress in coal mining stage and unloading stress in coal drawing stage and propulsion speed in fully mechanized top coal caving face.The effects of different propulsion speed on loading rate and loading and unloading stress path are analyzed by numerical simulation.With the increase of pushing speed,the cyclic loading and unloading amplitude under mining path increases,and the number of loading and unloading cycles decreases.The range of the main influence area increases,but the action time decreases.At different advancing speeds,the peak value of mining stress is the highest,the accumulation effect of high energy is relatively obvious,and the width of the plastic zone in front of the working face is the largest in the coal mining stage.There is an obvious exponential increasing function relationship between the strength and elastic modulus of coal samples and the loading rate,and the increasing trend of Poisson's ratio in the cyclic loading and unloading stage of coal samples under high-speed stress path is obvious.The strength of coal sample increases with the increase of loading rate and the corresponding propulsion speed of loading and unloading path,and the increasing effect of coal sample strength increases obviously with the synchronous increase of the two factors due to the double influence of loading rate and stress path.The accumulative release elasticity,dissipative plastic property and input strain energy of 3.2m/d under low speed propulsion are obviously lower than those at medium speed and high speed.By comparing the evaluation indexes of rock burst in coal mines,it is found that the coal samples under the stress path of 6.4m/d can be regarded as rock burst coal samples.Combined with the introduction of loading and unloading response ratio,the evaluation index of cyclic loading and unloading response ratio of coal samples under the influence of mining path is put forward,and it is found that the advancing speed of 4.8m/d can better meet the safe and efficient mining of B3+6 coal seam+425 level in Wudong Coal Mine.This study provides a reference for safe and efficient mining of fully mechanized top-coal caving face in steep seam.