单自由面爆破振动特征的炮孔堵塞长度效应

Blasthole stemming length effects of single free-face blasting vibration characteristic

单自由面爆破条件下作用在岩体上的最有效破坏力小,而阻碍岩体破坏的作用力很大,使炮孔堵塞长度对爆破振动有较大影响。因此,研究单自由面爆破振动特征的炮孔堵塞长度效应有重要意义。进行了小规模的不同堵塞长度的单自由面爆破试验,并模拟了其爆破过程。研究表明,近距范围内爆破振动速度迅速衰减,中远距离爆破振动速度衰减趋缓;随着堵塞长度的增加,场地系数K不断增加,衰减指数α总体呈上升趋势;数值模拟振动速度值与实测值误差在15%以内;爆破后不同堵塞长度模型的堵塞物底部空腔半径基本相等,约为装药半径的3倍;试验最优堵塞长度为15～20 cm,相同条件下无堵塞爆破对孔口有效应力场影响较大、对孔底有效应力场影响较小。

The best valid breaking force on the rock mass is very weak,but the impeding force on the rock mass is quite strong under free-face blasting condition.Then blasthole stemming length has a great impact on the blasting vibration.Therefore,it is important to study the stemming length effects of single free-face blasting vibration characteristic.This paper carry out small scale experiment of single free-face blasting with different stemming lengths,and simulate the blasting process.It reveals that the velocity of the vibration due to blasting decreases rapidly in the near field and slowly in the far field.The values of site coefficient K and attenuation coefficient ？ increase with the increase of the stemming length.The error of simulated and measured vibration vilocity is less than 15%.The bottom of stem cavity radius of models with different stemming lengths is almost equal;and the cavity radius is about three times for the charge radius.The optimal of stemming length is 15-20 cm in this experiment,non-stemming blasting has greater effect on the effective stress field at the upper blasthole but less effect on the effective stress field at the bottom under the same conditions.