Saturday, April 26, 2014

Risk Bumpers

We engineers, from time to time, make a recommendation to do something, not to do something, to wait a period of time before building, or whatever.

Along come the owner, contractor, general engineer, and in the words of Dino, "you geotechnials are too conservative" and try to ignore our recommendations. I no longer care if you do not follow my recommendations. You may receiver a letter like this;

Our recommendations are not binding on you. If you wish to assume greater risk of movement, which is in fact the total risk, you may do so.

Engineered fill suffers from movement from a number of sources:
- time dependent elastic and plastic movements, compaction and consolidation of the underlying soils,
- stress changes and moisture changes in the engineered fill
- swelling or shrinkage brought about by changes in the water table changes due to a new moisture regime

If anyone thinks they can estimate these for the first year, which are the large portions of movements, just have at it and accept the risk.  Anyone who is risk adverse will wait the first year, which will account for something like 50% of the movements.

In summary, you can do as you like, but all movements are your problem.

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