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.