Environmental Engineering Reference
In-Depth Information
Screws
Spring
Head
assembly
Buckets
(leather)
30-in. steel tube
Piston
assembly
Piston
rod lock
FIGURE 2.64
Stationary piston sampler. (Courtesy of Sprague and Henwood, Inc.)
(a)
(b)
(c)
Drill rod
Ball check
Sampler head
Piston
Air vent
Pressure
cylinder
Water under
pressure
Water return
circulation
Hollow
piston rod
Hole in
piston rod
Thin-walled
sampling tube
Fixed piston
Soil sample
FIGURE 2.65
Operation of the Osterberg piston sampler. (a) Sampler is set on cleaned bottom of borehole. (b) Hydraulic
pressure propels sampling tube into the soil. (c) Pressure is released to through hole in piston rod. (From ENR,
Engineering News Record,
1952. Reprinted with permission of McGraw-Hill.)
Denison Core Barrel
The Denison core barrel is used in materials such as hard clays and cemented sands. It
includes a rotating outer barrel and bit containing a fixed inner barrel with a liner, as
shown in
Figure 2.66.
The cutting shoe on the inner barrel can extend below the cutting
bit. Liners range from 28-gage galvanized steel to brass and other materials such as phe-
nolic-resin-impregnated paper with a 1/16 in. wall. Various bits are available for cutting
materials of varying hardness, to obtain samples ranging in diameter from 2 3/8 to 6 5/16
in. Sample tubes range from 2 to 5 ft in length. The extension of the cutting shoe below the
cutting bit is adjustable. The maximum extension is used in relatively soft or loose mate-
rials, whereas in hard materials the shoe is maintained flush with the bit.
During drilling, pressure is applied by the hydraulic feed mechanism on the drill rig to
the inner barrel, while the bit on the outer barrel cuts away the soil. The sampler is
