What is soil investigation ?

This method was developed to obtain very quickly a useful pattern
of the nature of the ground with depth. The basic procedure
is as follows : A cone: with a base area of 10 cm2 and a slope
of 600, fitted on to the lower end of a steel rod placed in
a tube, and whose length can be extended as required, is driven
at a uniform speed vertically into the soil surface underneath,
usually to a depth of 20 cm. Next, the pressure rod ex tending
above the tube, is pressed slowly and steadily down another
5 cm via  load cell.

The force required to overcome the resistance encountered by
the sounding cone commonly called the ‘cone resistance’, is
read on the pressure gauge of the measuring unit and recorded
by the operator.This operation of driving first the tube, followed
by the cone a alone, is then repeated regularly for every
200 mm depth increment.

The results are plotted in the form of a sounding graph, the
depth being represented by the Y-axis and the ‘cone resistance’
by the X-axis. Tha local friction value for the soil can also
be measured concurrently with the cone  penetration value by the
substitution of the jacket cone with a friction jacket cone.
friction jacket cone  combines the 10 cm2 cone with the 150
cm2 friction cleeve located above the cone.

The prime advantage of this method lies in its ability to provide
an accurately controlled measurement of the ground conditions
insitu without the disturbance inherent when boring or drilling
operations are used.

In addition, it is much quicker than the normal exploratory
boring and sampling when conditions are appropriate to both
methods .While the numerical form of the measurement, helps
to minimize errors due to human human factors on which boring operati-
ons place a heavy responsibility.