Soil Exploration - Soil Properties: Testing, Measurement, and Evaluation - page 20

Figure 2-14
Vane tester.

T

h

d

is carried out by pushing the vane tester into the soil and then applying
a torque to the vertical shaft. The clay's cohesion can be computed by
using the following formula [1]. *

T

c (2-1)

d 2 h d 3

p 1 > 2 2 1 > 6 2

where c = cohesion of the clay, lb/ft 2 or N/m 2
T = torque required to shear the soil, ft-lb or m · N
d = diameter of vane tester, ft or m
h = height of vane tester, ft or m
It should be emphasized that the field vane test is suitable for use
only in soft or sensitive clays. Also, no soil sample is obtained for subse-
quent examination and testing when a field vane test is performed.

The subject of this chapter should be considered as one of the most im-
portant in this topic. Analysis of soil and design of associated structures
are of questionable value if the soil exploration data are not accurately
determined and reported. It is of utmost importance that complete and
accurate records be kept of all data collected. Boring, sampling, and test-
ing are often costly undertakings, and failure to keep good, accurate
records is not only senseless, but may also be dangerous.
The authors hope this chapter will give the reader an effective in-
troduction to actual soil exploration. However, learning to conduct soil
exploration well requires much practice and varied experience under
the guidance of experienced practitioners. Not only is it a complex sci-
ence, it is a difficult art.

SUMMARY

REFERENCE

[1] Skempton A. W. and A. W. Bishop, “The Measurement of the Shear

Strength of Soils,” Geotechnique , 2(2) (1950).

NOTE: Material in this chapter was adapted from Soils and Foundations ,7 th edition
by Liu and Evett (Prentice Hall, 2008).
* Numbers in brackets refer to references listed at the end of each chapter.