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Very often, the biggest challenge for most excavation Engineers is complaints about noise and vibrations from the neighbourhood; if it involves Rock blasting, the first thing the Neighbours assume is that the blasting is certainly going to damage their properties.

Ground vibrations are not caused just by Rock blasting alone but bye by many activities that cause ground movement, such as traffic train moment, Pile driving, Machinery movement etc. In that case, why people complain only when blasting Rock but not when the heavy machine is being used in the neighbourhood or a train passes at a very high speed.

Familiarity is the answer. Most of us are used to traffic noise, and we don’t consider traffic as an intrusion in to hour our day-to-day life.

We are prepared for it; it doesn’t surprise us.

Whereas blasting noise is sudden and is something unexpected. There is the notion that rock blasting will certainly cause damage. Fly rock and noise only add to enhance this image.

In one of the experiments in Kerala, which is known as god’s own country, we increased the ground vibrations and decreased the noise; the neighbours felt the second blast, where the ground vibrations were higher, was better than the first blast, where actually the ground vibrations were lower, but the noise was higher.

A common man cannot differentiate between noise and ground vibrations; the only thing he knows is vibrations are causing damage. It is the blasting engineer’s job to understand the real problem and solve it.

Is every ground vibration dangerous?

No, not at all; all the structures are designed to withstand certain amount of vibrations. As long as the vibrations are generated or within these limits, the chances of damage are zero. It’s often observed that A bus travelling at a very high speed induces higher vibrations than a carefully designed blast.

Vibrations limits 

The damage due to continuous exposure to vibrations, sometimes due to traffic etc.. is much higher than the limited exposure for a short duration. Traffic vibrations come in the first category and have lower allowable limits than blasting vibrations.

Continuous vibrations expose a structure to creep (https://uttamblastech.com/knowledge-corner/blasting-damage/   and https://en.wikipedia.org/wiki/Creep_(deformation) ) like stress and may be more dangerous than higher exposure for a very short duration.

Hence many countries have different limits for different activities.

Vibration Limits : 

Visit to know the vibration limits of different countries.

Unfortunately, India doesn’t have Vibration limits for different activities. India only follows the limits described bye by the Director General of Mines Safety Vide their circular number 07 of 1997

How do you measure vibrations?

Vibrations are measured using a Seismograph. A seismograph measures the ground vibrations in 3 axes that is X, Y and Z. As long as vibrations or within acceptable limits, there is no issue, but comparing with the right standards is the key.

Download seismograph brochure 

Who should measure?

It is always better to delegate vibration measurement to a third party who is specialised in doing this. This also helps in gaining the confidence of the neighbours and in case of a dispute, the third party acts as a reliable witness.

Place of Measurement:

At the foundation of the nearest structure is the place to measure. If the nearest structure is safe, then the farther structure is certainly safe, unless it’s a different type of structure or there is geological change causing a change in the propagation of ground vibrations.

Authenticity of Point of Measurement:

The best way to dispel doubt is to go for continuous measurement. Today seismographs can be set up to measure all the vibrations on a 24/7 basis.

These stations record all the vibrations irrespective of time and source. Automatic alerts are sent whenever Vibrations are above a preset limit.

The Singareni Collieries Company Limited is the first company in India to try this at their JVR OCP.

Another method is to take readings with a seismograph with GPS. These seismographs note the GPS coordinates of the instrument and the Satellite time of the measurement. By clicking the coordinates in the report location of the instrument is visible on Google Maps with the time.

No more manipulation of time and location.

Uttam Blastech is the only company in India offering these.

Contact crm@uttamblastech.com to get commercial details of the above.
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