Reaction of Soils and Foundations to Vibration
Reaction of Soils and Foundations to Vibration
(OP)
I am trying to gauge the effect of vibration (from generators and a rolling mill) on underlying soils, and subsequently the foundations on which the vibrating sources are supported. I have various calcs for particle velocity, particle acceleration, displacement, propogation and transfer factor, I just can't quire figure how to relate them all. Does anyone have any tips on how to gauge this? Unfortunately I don't have a frequency for the vibratory sources.





RE: Reaction of Soils and Foundations to Vibration
Bowles has a section on Dynamic Analysis. I believe you need to determine the dynamic modulus. I was recently involved in a project where seismic refraction was used to determine the dynamic modulus. I am mot familiar with the analysis beyond that.
RE: Reaction of Soils and Foundations to Vibration
The Bowles book chapter on foundation vibrations is pretty good.
The reference though is still Gazeta's "Foundation vibrations" in Foundation Engineering Handbook, Fang, 1991. Lots of plots, graphs, illustrations.
More recently, Wolf And Deeks 2004 proposed a cone-model, whose result are identical to Gazeta's model with axialsymmetrical foundations. Their book has a link to a standalone calculation program (CONAN).
Other authors are Puri and Prakash (various years of publication.
According to Gazetas when dealing with machinery vibrations the strains are so small that the dynamic shear modulus Go should be used (might not be the same when strong earthquakes are involved).
Go may be calculated from Vs, shear wave velocity, or Eo, young's modulus at small strains.
In the case of shallow rigid bedrock, I would suggest today to use Nakamura's method (microtremors) to measure directly the frequency of resonance of the ground, since the solutions give very high settlements when the frequency of machinery is close to that.
RE: Reaction of Soils and Foundations to Vibration
RE: Reaction of Soils and Foundations to Vibration
Now, you can imagine better than I what would happen should the machinery work with that same frequency. In the Gazetas model that would result in a very small dynamic subgrade modulus hence a substantial settlement.
RE: Reaction of Soils and Foundations to Vibration
Bear in mind, dynamic parameters can only be derived from dynamic tests and not static parameters - but you probably know that, so apologies if I am "telling you how to use a scewdriver'.