Dear All,
We are aware that the stress around a borehole blasting are dependent on the blast loading rate , i was doubtful if PPV is affected by the loading rate?
Yes, PPV is depend on the quantity of explosive blast in one time. If you blast huge quantity of explosive the PPV will be increases and minimize with distance.
Yes, that is definite thing and is accounted in the very scaled distance, i am asking about the loading rate lets say using the same amount of weight of explosive.
All right, after concerning with my mentor I confirm that PPV is not affected by loading rate either you pour into bore hole at slow rate or fast rate.
Loading rate is totally related with density of explosive and PPV is not much affected by density.
I think the loading rate has a great impact on PPV. Assuming that the total energy is the same, if the rock is impacted at low speed for a long time, the PPV it excites is obviously lower than the PPV at high speed for a short time. Similarly, I think the frequency may also be affected by the loading rate.
Shengtao Zhou Yes you are absolutely correct and i had studied the impact of loading rate on both breakage an PPV which were directly proportional.Even though the total energy remains same , in case of a fast loading rate the initial energy spent is much higher than the later case which results in PPV.
Thank you for your answer.
Regards,
Partha
The question from Shengtao is very good and all discussions you have done are very interesting. First we need to define what is Blast loading rate. If this rate means the original detonation wave from explosive explosion, the loading rate is extremely high since the front of the wave is shock wave whose rising time is only a few microseconds for commercial explosive if the holes are fully charged. If the holes are not fully charged, the rising time may be longer. After the shock wave goes into the rock from the blasthole, shock wave attenuation occurs fast due to rock fracture and other factors. as we talk about PPV, usually we mean the vibration in the far field where the PPV is affected by many factors such rock fracture/fragmentation, confining pressure to the rock, free surface or interface, detonator or primer position, properties of the explosive and the rock.
Zongxian Zhang ,Thank You for this answers , specifically pointing out that PPV is measured at a distance(far field) and indeed many other factors , other than loading rate affect it.
Thank You,
Regards,
Partha
Partha Pinaki. Thanks for your comment and understanding. PPV is usually used for vibration control or study. That is why it is measured in the far field although some researchers measured that also in the location not far from blast source. If you work in the field of vibration control, it is better to know blasting very well. A same amount of explosive charge in a same size borehole can cause totally different vibrations at a same location where you have monitor recording the waves. For example, a cut hole blasting can produce much higher vibration than other holes in tunneling.
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