Humboldt H-4202A Dynamic Cone Penetrometer Set - Manual (Page 3)

BACKGROUND:
The Standard Penetration Test (SPT) has its roots in the empirical observation of
blows per unit measure of driving casing. The SPT method requires mechanized
equipment to raise and drop a 140lb mass 30 in.. Numerous methods have been
developed to miniaturize the SPT such that hand operated tools could be used
at shallow depths where confined spaces or the need for expedience excludes
the use of a mechanized SPT device.
The late Prof. George Sowers developed one of the more popular devices in
1959 for field exploration and the evaluation of lightly loaded shallow spread
footings during the construction phase. For underlying theory the reader is
encouraged to consult the following reference: George F. Sowers and Charles S.
Hedges. Dynamic Cone for Shallow In-Situ Penetration Testing, Vane Shear and
Cone Penetrations Resistance Testing of In-Situ Soils, ASTM STP 399, American
Society Testing and Materials, 1966, pg. 29. Copies can be purchased from
Humboldt.
The Dynamic Cone Penetrometer (DCP) illustrated in Figure 1a, uses a 15 lb
steel mass falling 20 in. to strike an anvil to penetrate a 1.5 in. diameter 45
degree cone that has been seated in the bottom of a hand augered hole. The
device has been used extensively in the Southeastern region of the USA and
calibrated with standard SPT results. The original correlations by Sowers are
shown in Figure 1b. Of course, similar correlation could be developed for soils
of other regions and of differing geologic derivation.
OPERATING INSTRUCTIONS:
1. The penetration test is performed in the bottom of a hand augered
hole generally 3 to 6 in. diameter.
2. Auger to the desired test depth taking care to remove as much of the bottom
cuttings as practical. Use the auger cuttings to identify and visually classify
the soil.
WARNING: Handle the Dynamic Cone Penetrometer with care. Do not grasp
the E-rod between the pull out anvil and the driving anvil as the 15 lb. sliding
weight moves easily along this part of the rod.
3. Gently lower the sliding drive hammer, extension rods and drive point to
the bottom of the borehole.
4. Making sure the assembly is plumb set the cone 2 in. into the undisturbed
bottom of the hole such that the cone is completely embedded.
NOTE: Laying a flat straight edge such as a survey stake across the borehole
and marking a beginning reference point will expedite measurements.