A cone penetrometer attached to the end of a series of rods is pushed
into the ground at a constant rate and continuous measurements are
made. The cone penetrometer consists of the cone tip, friction sleeve,
any other sensors and measuring systems, as well as the connections
to the push rods. The most commonly used measuring systems are:
- CPT Tip resistance + sleeve friction
- CPTU Tip resistance + sleeve friction + porewater pressure.
Increasingly, special cones (as described in Chapter 4) are used.
Probing with rods through weak ground to locate a firmer stratum has
been practised since about 1917. It was in the Netherlands in about
1932 that the CPT was introduced in a form recognisable today. In
earlier days the method was referred to as the static penetration test,
quasi-static penetration test and Dutch sounding test.
Existing CPT systems can be divided into three main groups:
- mechanical cone penetrometers (not used in the UK)
- electric cone penetrometers
- piezocone penetrometers.
A cone penetrometer with a 10 cm2 base area cone and an apex angle
of 60° is accepted as the reference and has been specified in the
international reference test procedure.
The CPT apparatus consists of a thrust machine and reaction system
(rig), and a penetrometer including measurement and recording
equipment. Machines generally have a thrust capacity in the range