Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 1 PLANNING AND SCOPE
1.7.2
Boring
Numerous methods are available for advancing
boreholes to
obtain samples or details of soil strata.
The particular methods used by any country will tend to be
restricted, based on their suitability for
local ground conditions. The principal methods used worldwide include:
• Light
percussion drilling;
• Power augering; and
• Washboring.
1.7.2.1
Light Percussion Drilling
Often called ‘shell and auger’ drilling, this method is more properly termed light percussion drilling
since the
barrel auger is now rarely used with this type of equipment. The drilling
rig (Fig. 1. 4)
consists of:
i. A collapsible ‘A’ frame, with a pulley at its top;
ii. A diesel engine; connected via
a hand-operated friction clutch (based on a brake
drum system)
to
iii. A winch drum which provides pulling power to the rig rope and can
be held stilll with a friction
brake
which is foot-operated.
In clays, progress is made by dropping a steel tube knownn as a ‘claycutter’ into the
soil (see Fig.
1.5). This is slowly pulled out of the borehole and is then generally found
to have soil wedged inside
it.
Figure 1. .4 Light Percussion Drilling
Rig (Courtesy of Pilcon Engineering Ltd)
1-18
March 2009