When is Testing Needed? 1

[cbear1]

Hi All,
I have noticed as of late that soils reports include less and less lab testing. It seems that people take some blow counts, measure the moisture and call it a day based on some loose correlations with phi values, cohesion and bearing capacity.
When do you think lab values are absolutely necessary for shear, cohesion, etc? (ie: sensitive clays, nearness to water table, etc.) Your perspective is appreciated.

 

[fattdad]

I think laboratory testing is always necessary. Consider an earthwork spec. Why let the civil engineer go with, "SM or Better" when the on-site soils are ML with 30 percent sand (i.e., likely just fine)? Why base a heavy-duty pavement design on an "assumed CBR of 10", when the on-site soils have a CBR value of 6? A CBR requires a Proctor and a moisture profile can indicate whether the on-site soils are well over the optimum moisture content. Why let all this unfold during construction?

Then again, I'm likely preaching to the choir. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[escrowe]

I agree, recommendations without data are naked to the world.
Unfortunately, the lab budget is often the first to be slashed.

With regard to foundation issues, lab testing is fairly critical to ground improvement recommendations.
Most methods of GI are at least somewhat dependant on soil grain-size distribution and plasticity.

Likewise for consolidation estimates. Good lab data is fundamental.

In general, for a preliminary exploration, the lab scope might be reduced until a later time,
when the development and construction plans are somewhat further along.