Soil Exploration - Soil Properties: Testing, Measurement, and Evaluation - page 17

Figure 2-10
Fugro Electric Friction
Cone
Source: K. Terzaghi,
R. B. Peck, and G. Mesri,
Soil Mechanics in
Engineering Practice,
3rd ed., John Wiley &
Sons, Inc. New York, 1996,
fig. 11-13(b), p. 49. Copy-
right © 1996 by John
Wiley & Sons, Inc.
Reprinted by permission
of John Wiley & Sons, Inc.
Figure 2-11
Piezocone
Source: K. Terzaghi,
R. B. Peck, and G. Mesri,
Soil Mechanics in Engi-
neering Practice, 3rd ed.,
John Wiley & Sons, Inc.
New York, 1996,
fig. 11-13(c), p. 49. Copy-
right © 1996 by John
Wiley & Sons, Inc.
Reprinted by permission
of John Wiley & Sons, Inc.
In all cases, the penetrometer's resistance to being pushed through
the soil is measured and recorded as a function of depth of soil pene-
trated. The cone resistance ( q c ) is the total force acting on the pen-
etrometer divided by its projected area (i.e., the area of a
35.7-mm-diameter circle, or 10 cm 2 ). The friction resistance ( f s ) is the to-
tal friction force acting on the friction sleeve divided by its surface area
(i.e., the side area of a 35.7-mm-diameter, 133.7-mm-long cylinder, or
150 cm 2 ). The ratio of friction resistance to cone resistance is known as
the friction ratio and is denoted by F r (i.e., F r = f s / q c ). CPT data are ordi-
narily presented as plots of cone resistance, friction resistance, and fric-
tion ratio versus depth (see Figures 2-12 and 2-13). In general, the ratio