Load Series for Consolidation Test

[Storm-water]

Hi all - I have a shelby sample that I'm sending to a lab for consolidation testing. They are asking me what loading schedule/series I want performed. What does this depend on and how do I determine it?

Thanks

 

[BigH]

See ASTM D2435 Section 11.4.1 (double loading starting at 12.5 kPa to 200 kPa - standard loading) - of course this might have to be modified if very soft clay or peat - or very hard clay . . . you will be needing to look for the "break" in the plotted curve. There is also the need for cycling the load as well. What I find strange is that the lab should be helping you on this - they have the experience (perhaps you don't - no offense) . . . and as I said a lot depends on the nature of the material you are testing.

 

[GeoEnvGuy]

Review how you want to determine your pre consolidation pressure and the over/normally consolidated curves. Consider including a rebound loop at the tail end which can mirror the over consolidated curve.

 

[EireChch]

Good advice above from two gentlemen. A very good rule of thumb is to try have at least 2 data points (loads) before you existing overburden stress.

Tell me your sample depth and groundwater level and I will happily provide. Also, if you have any other info like SPT, Shear vane, CPT etc provide that. This will help identify any pre-consolidation pressure, which ideally you want to load above this pressure (if possible)

 

[morecoffeeplz]

It is never up to the lab to decide specific parameters for geotechnical tests.

From ASTM D2435:
1.3 It shall be the responsibility of the agency requesting
this test to specify the magnitude and sequence of each load increment, including the location of a
rebound cycle, if required, and, for Test Method A, the load increments for which time-deformation
readings are desired. The required maximum stress level depends on the purpose of the test and must
be agreed on with the requesting agency. In the absence of specific instructions, Section 11
provides the default load increment and load duration schedule for a standard test.

 

[EireChch]

I think the majority of us know that ultimate responsibility is with the assigning engineer, however I have met lab technicians that know a hell of a lot more than me reg lab testing and have used their opinion to inform my decisions many times.

I think that is the sign of a good lab, the get paid from the top of their head down, not just their shoulders down.....

 

[morecoffeeplz]

No doubt. A good lab tech is worth her mass in gold.