| Deep-hole presplitting explosion provides an new and effective method to increase permeability of high gassy and low permeability coal seam, and farther solves the difficult problem of gas drainage in this high gassy and low permeability coal seam. In this dissertation, several researching methods, such as theory analysis and numerical simulation and on-field experiment as well as practical engineering application, are used to systematically study the promoting permeability effect of deep-hole presplitting explosion as well as action mechanism of promoting gas drainage and preventing coal-gas outburst. Several effect factors to effect of deep-hole presplitting explosion, such as rigidity of coal and buried height as well as diameter of explosive holes and couple coefficient of explosion and distance between explosive holes and control holes in the same rigidity of coal and buried height and explosion intensity condition, are acquired, and several new results are acquired as followings:(1) The propagation rules of stress wave by explosion in viscous-elastic media is acquired:①explosion generated stress waves attenuate as spreading distance;②when spreading distance is less than 10m, stress waves' attenuation becomes minishing as the augment of delay time, and after spreading distance is larger than 10m, stress waves' attenuation becomes augment as the augment of delay time;(2) Rigidity of coal have big effect on explosion result: less rigidity of coal, easier to be destroyed. Under explosion generated stress waves, coal around explosive holes are very easy to crush. And crush circle zone is form, which has cushioning effect, and stops further growth of cracks. So bigger rigidity of coal, more abundant the cracks grow;(3) Under the same explosion intensity, buried height of coal has little effect to the result of deep-hole presplitting explosion. So this technology of deep-hole presplitting explosion can also be used in deep-buried coal bed;(4) After analysis, diameter of explosive holes' effect to result of deep-hole presplitting explosion is acquired. As the augment of diameter of explosive holes, the peak value of supporting stress in coal around explosive holes become high, and distance of peak value becomes large, but that fluctuates within a narrow range. So, when diameter of explosive holes become large, stress relief radius also becomes large, and stress relief radius R_a fluctuates between 2.7 and 3.5m.(5) Powder charge couple coefficient's effect to result of explosive is acquired: when couple coefficient B_l =0.6, ground stress curve has maximum and minimum value, and stress concentration form around explosive holes, so stress relief effect is very little; when couple coefficient B_l is between 0.8 and 1.0, long perfoliate cracks are generated. So ground peak value and stress relief distance is large, and stress relief result is good. So powder charge couple coefficient has great effect to ground stress relief, and larger couple coefficient, better stress relief;(6) Reasonable distance between explosive holes and control holes is increased: when distance L between explosive holes and control holes is in the range of 3～4m, stress relief radius becomes large as the augment of L, and relief result of ground stress become good;From experiment effect of on-field experiment, permeability of coal bed is remarkably increased by deep-hole presplitting explosion, and drainage gas concentration and volume of gas flow is remarkably increased, and effective relief radius is 3～3.5m. And this shows that the technology of deep-hole presplitting explosion is a kind of feasible method to increase permeability of low permeability and high gas coal bed, and this technology provides dependable technology safeguard to effectively and intensively mine coal for low permeability and high gas coal bed.
|
PDF Full Text Request