Marine Clay

[Zambo]

Would it be reasonable, as a rule of thumb, to define the presence of marine clay as a clay soil where the SPT value N = 0. The reason for this question is to determine the likelihood of Negative skin friction. We have consolidated soils but it is difficult to show that further consolidation and negative skin friction are not expected.

 

[fattdad]

that would not be a universal claim. Along the Coastal Plain of Virginia we have several marine clays that are quite stiff, and quite sensitive too. These marine clays are suited for drilled shafts and embankment loads rarely exceed preconsolidation pressures, so earth settlements are not the typical concern.

We also have normally-consolidated clays, organic silts and peat. These may be more "fluvial" in depositional environment; however, there is no doubt their stress history is completly different.

If you have low strength clay (or silt), do a 1-d consolidation test and determine the preconsolidation pressure, compression index, re-compression index and Cv values for varying levels of applied load. Then you'll have all the data to know the time rate and extent of settlement. You'll also have the data to determine secondary compression, which can be the long term item of concern with respect to downdrag.

f-d

¡papá gordo ain’t no madre flaca!

 

[tsek]

There would only be negative skin friction if loading (i.e. an embankment) was placed in the surrounding soils.