Foundation, Concrete and Earthquake Engineering

Foundation Settlement Due to Vibration

Generally vibration occurs in foundation when pile driving and blasting operation are done. This may be a part of construction operation of surrounding under construction buildings or for the new structure, that’s soil settlement are considered in design. The both operations are performed as a concept of compacting loose sand and subsidence is expected for new building but not expected for existing neighbor building if any.

As an example in a loose deposit of cohesionless soil 100 piles of 50 ft length were driven for same purpose of compaction. The result were occupied ground area settled 6 in. It was noticed that the settlement gradually decrease apart from pile driving area as an example at 50 ft apart the settlement was recorded only 1/8 in. So foundation engineers should be conscious about pile driving in such loose sand to avoid damage to surrounding structure. Sometimes other construction options are to be chosen leaving such vibration type foundation treatment.
Epoxy Grouts to reduce vibration from machine provided on foundation
Another source of vibration is arrived from machine foundation. It is very important to design machine foundation to have a period that has safe difference from the period of

Thickened foundation for machine foundation to absorb vibration.JPGadjacent soil to avoid possible resonance. Normally foundation weight is increased to absorb vibrations and distinguish period of both soil and foundation. There have a thumb rule of providing 2.5 times weight to foundation than that of machine to be supported.

Now, which type of soils suffers more due to vibration?
he cohesive soil suffers less impact from vibration. But alarming increment of relative density of cohessoinless soils are observed in this regard. This condition becomes worse to sands under water table or sand that is relatively dry. But sands above water table sometimes show sufficient cohesion not to re-arrange grain structure.

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