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Soil Survey Manual - Table 3-19

Manner of failure classes

Classes Operation Test Description Characteristics
Brittle Gradually increasing compressive pressure applied to a 25-30mm specimen held between extended thumb and forefinger Specimen retains its size and shape (no deformation) until it ruptures abruptly into subunits or fragments.
Semideformable Same Deformation occurs prior to rupture. Cracks develop and specimen ruptures before compression to half its original thickness.
Deformable* Same Specimen can be compressed to half its original thick- ness without rupture. Radial cracks may appear and extend inward less than half the radius normal compression.
Nonfluid A handful of soil material is squeezed in the hand. None flows through the fingers after exerting full compression.
Slightly fluid* Same After exerting full compression, some flows through the fingers, but most remains in the palm of the hand.
Moderately fluid* Same After exerting full pressure, most flows through the fingers; a small residue remains in the palm of the hand.
Very fluid* Same Under very gentle pressure most flows through the fingers like a slightly viscous fluid; very little or no residue remains.
Non-smeary Gradually increasing pressure applied to a 25-30 mm specimen held between extended thumb and forefinger in such a manner that some shear force is exerted on the specimen. At failure, the specimen does not change suddenly to a fluid, the fingers do not skid, and no smearing occurs.
Weakly smeary Same At failure, the specimen changes suddenly to fluid, the fingers skid, and the soil smears. Afterward, little or no free water remains on the fingers.
Moderately smeary Same At failure, the specimen changes suddenly to fluid, the fingers skid, and the soil smears. Afterward, some free water can be seen on the fingers.
Strongly smeary Same At failure, the specimen suddenly changes to fluid, the fingers skid, and the soil smears and is very slippery. Afterward, free water is easily seen on the fingers.

* The approximate equivalent n-values, Pons and Zonneveld (1965), are as follows:
     Deformable < 0.7 n-value
     Slightly fluid 0.7-1
     Moderately fluid -- 1-2
     Very fluid- ³ 2