Humboldt H-4195 Soil Penetrometer, Pocket Style - Manual (Page 3)

OSHA Soil Categories
OSHA categorizes soil and rock deposits into four types, A through D,
as follows:
Stable Rock: is natural solid mineral matter that can be excavated with
vertical sides and remain intact while exposed. It is usually identified by a rock
name such as granite or sandstone. Determining whether a deposit is of this
type may be difficult unless it is known whether cracks exist and whether or not
the cracks run into or away from the excavation.
Type A Soils: are cohesive soils with an unconfined compressive strength of 1.5
tons per square foot (tsf) (144 kPa) or greater. Examples of Type A cohesive soils
are often: clay, silty clay, sandy clay, clay loam and, in some cases, silty clay loam
and sandy clay loam. (No soil is Type A if it is fissured, is subject to vibration
of any type, has previously been disturbed, is part of a sloped, layered system
where the layers dip into the excavation on a slope of 4 horizontal to 1 vertical
(4H:1V) or greater, or has seeping water.
Type B Soils: are cohesive soils with an unconfined compressive strength greater
than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa). Examples of other Type B
soils are: angular gravel; silt; silt loam; previously disturbed soils unless other-
wise classified as Type C; soils that meet the unconfined compressive strength or
cementation requirements of Type A soils but are fissured or subject to vibration;
dry unstable rock; and layered systems sloping into the trench at a slope less
than 4H:1V (only if the material would be classified as a Type B soil).
Type C Soils: are cohesive soils with an unconfined compressive strength of 0.5
tsf (48 kPa) or less. Other Type C soils include granular soils such as gravel, sand
and loamy sand, submerged soil, soil from which water is freely seeping, and
submerged rock that is not stable. Also included in this classification is material
in a sloped, layered system where the layers dip into the excavation or have a
slope of four horizontal to one vertical (4H:1V) or greater.
Layered Geological Strata: Where soils are configured in layers, i.e., where a
layered geologic structure exists, the soil must be classified on the basis of the
soil classification of the weakest soil layer. Each layer may be classified individu-
ally if a more stable layer lies below a less stable layer, i.e., where a Type C soil
rests on top of stable rock.
Penetrometer Adapter Foot
The H-4195F Adapter foot is recommended when
testing extremely low strength cohesive soils.
1" (25mm) dia. foot, compared to the .25" (6.35mm)
penetrometer piston, increases the effective area
measured by 16 times. Divide by 16 to obtain correct
unconfined compressive strength when the reading in
tons per square foot or kilograms per square centimeter is on the low-load side.