Soil exploration

1. Department of Civil Engineering
Methods of Boring
Presented By- Rakesh Ahirwar
S.N. 202111105
Branch- Geotechnical Engineering

2. INDEX
 Boring
 Types of Boring
 Auger boring
 Shell and auger boring
 Wash boring
 Percussion boring
 Rotary drilling
 Reference

3. Boring
 Making or drilling bore holes into the ground with a view
to obtained soil or rock samples from specified or known
depth is called ‘boring’
 The object of site investigation is to obtain reliable, specific
and detailed information about the soil/rock and
groundwater conditions at a site for enabling engineers in
the safe and economic design and execution of engineering
works.
 The member and spacing of borings/test pits depends on
the type and size of foundations and extent of variation in
soil conditions. IS 1892 gives the detail of depth of boring.

4. Types of Boring
 The types of boring methods commonly adopted
for soil exploration are as under :-
 Auger boring
 Shell and Auger boring
 Wash boring
 Percussion boring
 Rotary boring

5. Auger boring:
 Soil auger’ is a device that is useful for advancing a bore
hole into the ground. Augers may be hand-operated or
power-driven; the former are used for relatively small
depths (less than 3 to 5 m), while the latter are used for
greater depths. The soil auger is advanced by rotating it
while pressing it into the soil at the same time. It is used
primarily in soils in which the bore hole can be kept dry
and unsupported. As soon as the auger gets filled with soil,
it is taken out and the soil sample collected.
 Hand Operated Augers
 Power Driven Augers

6. Hand Operated Augers

7. Power Driven Augers

8. Shell and auger boring:
 In this method different type of tools have to be adopted for
boring. In case of soft to stiff clay, cylindrical auger
consisting of a hollow tube of 75 to 200mm in diameter with
a cutting edge at its bottom is used. In case of various stiff
and hard clay, shells with cutting edge or teeth at lower end
are to be adopted while in case of sandy soil, shells or sand,
pumps are used for boring. By this method it is possible to
make vertical boring up to 200 mm in diameter and 25 m in
depth by use of a hand rig. By use of mechanical rig it is
possible to extend the depth of the bore hole up to 50 m.
The samples of the soil are recovered at regular intervals (or
whenever there is a change in strata) for conducting tests in
laboratory for identification of soils and establishing
properties of the sub-soil strata at various depths.

9. Shell and auger boring:

10. Wash boring:
 For test boring over 3 meter in depth, this method can be
conveniently used. In this method a hollow steel pipe known
as casing pipe or drive pipe is driven into the ground for a
certain depth. Then a pipe usually known as water jet pipe or
wash pipe, which is shorter in diameter, is lowered into the
casing pipe. At its upper end, the wash pipe is connected to
water supply system while the lower end of the pipe is
contracted so as to produce jet action. Water under
considerable pressure is forced down the wash pipe. The
hydraulic pressure displaces the material immediately below
the pipe and the slurry thus formed is forced up through the
annular space between the two pipes. The slurry is collected
and samples of material encountered are obtained by
settlement.

11. Wash boring:
 In this process the particles of finer material like clay,
loam etc. do not settle easily and the larger and heavy
particles of the soil may not be brought up at all.
Moreover, the exact position of a material in the
formation cannot be easily be located. However the
change of stratification can be guessed from the rate of
progress of driving the casing pipe as well as the color of
slurry flowing out. Yet the results obtained by wash
boring process give fairly good information about the
nature of the sub-soil strata. This method can be
adopted in soft to stiff cohesive soils and fine sand.

12. Wash boring:

13. Percussion boring:
 This method consists of
breaking up of the sub-
strata by repeated blows
from a bit or chisel. The
material thus pulverized is
converted into slurry by
pouring water in the bore.
At intervals the slurry is
bailed out of the hole and
dried for examination. This
method can be adopted in
rocks and soils having
boulders. However this
method is not
recommended for loose
sand or clayey soils.

14. Rotary drilling:
 When rocks or hard pans are to be penetrated for
examination, core drilling is done to get undisturbed
samples of the formation. In this process a hole is made
by rotating a hollow steel tube having a cutting bit at its
base. The cutting bit makes an annular cut in the strata
and leaves a cylindrical core of the material in the hollow
tube. Two types of cutting bits are generally used,
namely, diamond bit and shot bit. Diamond bit consists
of industrial diamonds set in the face of the bit and in
shot bit, chilled shot is used as an abrasive to cut the
hard pan. When core samples of small diameter are
needed, diamond bit is preferred.

15. Rotary drilling:

16. Reference
 NPTL,
https://nptel.ac.in/content/storage2/courses/105108069/mod01/lec01.pdf
 Google for images.

17. THANK
YOU