Effect of gradation of soil with depthy

[shankar20470402]

Somebody told me that with the increase in depth the gradation of soil will change. that is at the surface level generally the soil is poorly graded but when we go deeper the soil will be well graded... is it correct??? if so,then what may be the reason behind it??

 

[Ron]

The gradation of soil particles has little or nothing to do with depth alone. The gradation is defined by many factors including the type of soil deposition, the character of the parent material, environmental influence, age of deposition, etc.

As an example, in stratified coastal plains soils, it is common to see fine sands at the surface, fine grained soils below the surface (clays and silts), medium sands interspersed and various layers of each.

If you could predict soil gradation with depth, geotechnical engineering would be simplified greatly! Not so.

 

[BigH]

As an add-on to Ron, residual soils do change gradation with depth; they typically become more 'blocky' as the weathering process is more pronounced at the surface and less so as one goes deeper . . .

 

[mudman54]

i agree with ron; you better check the geology of the soil deposit before you go making assumptions about gradation with depth; for example, a deltaic deposit will tend to have coarsening upward gradations while a lacustrine deposity will have fining upward gradations.

 

[fattdad]

if you know you are in a transgressional sequence, the soil will become coarser with depth. If you know you are in a regressional sequence the opposite will be true. Now the trick is to know where the transgressinal sequence changes to a regressional sequence. Of coarse this relates to the Coastal Plane and those soils borne by marine activity.

Other fluvial deposits are not as "predictable." (consider deltaic deposits for example.)

f-d

¡papá gordo ain’t no madre flaca!