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Question
Hi,

You answered a question in 22nd May 2008 regarding conversion of PPV to G. I was wondering if this is the same as converting the PPV to the seismic coefficient? If this is so could you also please direct me where I could look for further reading on the subject as I am currently looking into it for my Masters thesis.

Many thanks

Answer
I suppose you could apply the conversion but the problem is that the seismic coefficient is defined for generalized horizontal ground motion and the peak particle velocities are measured in two horizontal components, radial and transverse.  However they both are in units of gravity.

The other thing to appreciate is that the usual manner of converting from ppv to G is differentiating the velocity time history.  Blasting seismographs do this by assuming simple harmonic motion applied to the zero-crossing frequency, essentially applying the factor 2(pi)f.  It's an OK approximation for the extensive time histories that you get with blasting, pile driving, and the like, most of which is high frequency, relative to the frequencies of earthquake ground motions.  However the frequency content of earthquake motions is different from that of blasting in that the low-frequency component tends to dominate, so a small difference in frequency would have a large effect on the calculated acceleration.  Coupled with the fact that shear and surface waves dominate in earthquake motions and the best way to get earthquake motions is with an accelerometer.

The reason for using ppv to calculate a seismic coefficient would, in my mind, be applying seismic design provisions built into a design (according to a predicted horizontal seismic coefficient) to ground motions that would be measured in ppv.  As I said, this presents issues with comparability and measurement technique.  

As a starting point I'd recommend reading the book Construction Vibrations by Dowding -- he goes into the use of earthquake engineering techniques and the measurement of vibrations from construction.

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Robert Cummings, P.E.

Expertise

I can answer questions related to rock blasting, rock and soil excavation (such as tunnels and highway cuts), stability of such excavations, and foundations in rock and soil. I can also answer questions related to geology and mining.

Experience

30+ years as a geotechnical engineer and minerals engineer. Active consulting practice in rock blasting, geotechnical engineering, and rock mechanics for mining and heavy construction.

Organizations
Society of Mining Engineers, Deep Foundations Institute, Association of Engineering Geologists, and International Society of Explosives Engineers.

Publications
Mining Engineering, AEG Bulletin.

Education/Credentials
BS and MS Geological Engineering

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