临近边坡毫秒延时爆破合理延时时间试验

Experimental study on reasonable delay time of millisecond delay blasting near slope

临近边坡毫秒延时爆破时需综合考虑岩体爆破效果及保留岩体稳定两方面因素,结合数码电子雷管开展毫秒延时爆破相似模型试验,采用动态应变测试仪及高速相机分别对边坡应力场和岩体裂缝扩展情况进行监测。结果表明:减振沟作用下,边坡表面径向应力峰值由2.26MPa降低为0.84MPa,切向应力峰值由1.16MPa降低为0.95MPa,径向与切向应变平均减振率分别为49.4%和35.2%;孔间延时时间为15ms或25ms时,可降低延时时间对应变峰值影响;孔间延时时间为11ms时,裂缝宽度平均值为11.79mm,可形成新自由面,孔间延时时间大于15ms,后孔爆破时,前序药包残余应力场几近消失。试验条件下,最优孔间延时时间为15ms。

The rock blasting effect and stability of reserved rock mass should be considered at the same time in millisecond delay blasting near slope.Combined with digital electronic detonators,the similar model test of millisecond delay blasting was designed and carried out.Dynamic strain tester and high-speed camera were used to monitor stress field and crack propagation of slope rock mass respectively.The results showed that,under the action of damping ditch and on the slope surface,radial peak stress decreased from 2.26 MPa to 0.84 MPa,tangential peak stress decreased from 1.16 MPa to 0.95 MPa,and the average damping rates of radial and tangential strain were 49.4% and 35.2%respectively.The influence of delay time on the peak strain was reduced with 15 ms or 25 ms.The average width of crack was 11.79 mm that could form new free surface with delay time of 11 ms.The residual stress field of previous explosive charge almost disappeared when subsequent explosive charge detonated with delay time longer than 15 ms.Under experimental conditions,the optimal delay time between blasting holes was15 ms.