3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
average surface roughness
Ra
average deviation between the real surface of the cone penetrometer and a medium reference plane placed along the surface of the cone penetrometer
3.1.2
cone
conical shaped bottom part of the cone penetrometer and the cylindrical extension
NOTE 1 When pushing the penetrometer into the ground, the cone resistance is transferred through the cone to the load sensor.
NOTE 2 This part of ISO 22476 assumes that the cone is rigid, so when loaded its deformation is very small relative to the deformation of other parts of the cone penetrometer.
3.1.3
cone penetration test
CPT
pushing of a cone penetrometer at the end of a series of cylindrical push rods into the ground at a constant rate of penetration
3.1.4
cone penetrometer
assembly containing the cone, friction sleeve, any other sensors and measuring systems as well as the connection to the push rods
NOTE An example of a cone penetrometer is shown in Figure 1; for other filter locations, see Figure 2.
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a) Cone resistance and sleeve friction load cells in compression | b) Cone resistance load cell in compression and sleeve friction load cells intension | c) Subtraction type cone penetrometer |
Key
- 1 sleeve load cell
- 2 point load cell overload protection device
- 3 cone load cell
- 4 thread
- 5 soil seal
3.1.5
cone resistance
cone penetration resistance
3.1.6
corrected cone resistance
qt
measured cone resistance, qc, corrected for pore pressure effects
3.1.7
corrected friction ratio
Rft
ratio of the measured or corrected sleeve friction to the corrected cone resistance measured at the same depth
NOTE Usually the measured sleeve friction is used; however, if available, the corrected sleeve friction is used.
3.1.8
corrected sleeve friction
ft
measured sleeve friction, fs, corrected for pore pressure effects
3.1.9
dissipation test
measurement of the pore pressure change with time during a pause in pushing while holding the cone penetrometer stationary
3.1.10
electrical cone penetration test
cone penetration test where forces are measured electrically in the cone penetrometer
3.1.11
excess pore pressure
Δu1, Δu2, Δu3
pore pressure in excess of the ambient pore pressure at the level of the filter caused by the penetration of the
cone penetrometer into the ground:
3.1.12
filter element
porous element in the cone penetrometer that transmits the pore pressure to the pore pressure sensor, maintaining the geometry of the cone penetrometer
3.1.13
friction ratio
Rf
ratio of the measured sleeve friction to the measured cone resistance at the same depth
3.1.14
friction reducer
local and symmetrical enlargement of the diameter of a push rod to obtain a reduction of the friction along the push rods
3.1.15
friction sleeve
section of the cone penetrometer where friction between the soil and the sleeve is measured
3.1.16
in situ equilibrium pore pressure
u0
original in situ pore pressure at filter depth
3.1.17
inclination
angular deviation of the cone penetrometer from the vertical
3.1.18
initial pore pressure
ui
measured pore pressure at the start of the dissipation test
3.1.19
measured cone resistance
qc
division of the measured force on the cone, Qc,by the projected area of the cone Ac:
3.1.20
measured pore pressure
u1, u2, u3
pressure measured in filter element during penetration and dissipation testing
NOTE The pore pressure can be measured at several locations as follows {see Figure 2):
u1 on the face of the cone;
u2 on the cylindrical section of the cone {preferably in the gap between the cone and the sleeve;
u3 just behind the friction sleeve.

Key
- 1 friction sleeve
- 2 cone penetrometer
- 3 cone
3.1.21
measured sleeve friction
fs
division of the measured force acting on the friction sleeve, Fs, by the area of the sleeve, As:
3.1.22
measuring system
all sensors and auxiliary parts used to transfer and/or store the electrical signals generated during the cone penetration test
NOTE The measuring system normally includes components for measuring force (cone resistance, sleeve friction), pressure (pore pressure), inclination, clock time and penetration length.
3.1.23
net area ratio
a
ratio of the cross-sectional area of the load cell or shaft, Ast, of the cone penetrometer above the cone at the location of the gap where fluid pressure can act, to the nominal cross-sectional area of the base of the cone, Ac
NOTE See Figure 6.
3.1.24
net cone resistance
qn
measured cone resistance corrected for the total overburden soil pressure
3.1.25
net friction ratio
Rfn
ratio of the sleeve friction to the net cone resistance measured at the same depth
3.1.26
normalized excess pore pressure
U
excess pore pressure during a dissipation test compared to the initial excess pore pressure
NOTE See 7.4.
3.1.27
penetration depth
z
vertical depth of the base of the cone, relative to a fixed point NOTE See Figure 3.
3.1.28
penetration length
l
sum of the lengths of the push rods and the cone penetrometer, reduced by the height of the conical part, relative to a fixed horizontal plane
NOTE 1 See Figure 3.
NOTE 2 The fixed horizontal plane usually corresponds to the level of the ground surface (on shore or off shore). This can be different from the starting point of the test

Key
- a fixed horizontal plane
- b base of conical part of cone
- l penetration length
- z penetration depth
3.1.29
piezocone penetration test
CPTU
electrical cone penetration test with measurement of the pore pressures around the cone
3.1.30
pore pressure ratio
Bq
ratio of the excess pore pressure at the u2 filter position to the net cone resistance
3.1.31
push rod
part of a string of rods for the transfer of forces to the cone penetrometer
3.1.32
reference reading
reading of a sensor just before the penetrometer penetrates the ground or just after the penetrometer leaves the ground
NOTE 1 In offshore situations, it is the reading taken at the sea bed or at the bottom of a bore hole with water pressure acting.
NOTE 2 With tests starting on shore from the ground surface, the reference reading equals the zero reading.
3.1.33
thrust machine
equipment that pushes the cone penetrometer and rods into the ground at a constant rate of penetration
3.1.34
total overburden stress
σv0
stress due to the total weight of the soil layers at the depth of the base of the cone
3.1.35
zero drift
absolute difference between the zero readings (or reference readings) of a measuring system at the start and after completion of the cone penetration test
3.1.36
zero reading
stable output of a measuring system when there is zero load on the sensors, i.e. the parameter to be measured has a value of zero, while any auxiliary power supply required to operate the measuring system is switched on
3.2 Symbols
Symbol | Name | Unit |
Ac | cross-sectional projected area of the cone | mm2 |
An | cross-sectional area of load cell or shaft | mm2 |
As | surface area of friction sleeve | mm2 |
Asb | cross-sectional area of the bottom of the friction sleeve | mm2 |
Ast | cross-sectional area of the top of the friction sleeve | mm2 |
a | net area ratio | |
Bq | pore pressure ratio | |
Cinc | correction factor for the effect of the inclination of the cone penetrometer relative to the vertical axis | |
dcone | diameter of the cone at a specified height | mm |
dc | diameter of the cylindrical part of the cone | mm |
dfil | diameter of the filter | mm |
d2 | diameter of the friction sleeve | mm |
Δu1, 2, 3 | excess pore pressure at filter locations 1, 2 and 3 | MPa |
Fs | axially measured force on the friction sleeve | kN |
fs | measured sleeve friction | MPa |
ft | corrected sleeve friction | MPa |
hc | height of the conical section of the cone | mm |
he | length of the cylindrical extension of the cone | mm |
l | penetration length | m |
ls | length of the friction sleeve | m |
Qс | axially measured force on the cone | kN |
qс | measured cone resistance | MPa |
qn | net cone resistance | MPa |
qt | corrected cone resistance | MPa |
Ra | average surface roughness | urn |
Rf | friction ratio | % |
Rft | corrected friction ratio | % |
Rfn | net friction ratio | % |
t | time | s |
t50 | time needed for 50 % excess pore pressure dissipation | s |
U | normalized excess pore pressure | |
u | pore pressure | MPa |
ui | pore pressure at the start of the dissipation test | MPa |
ut | pore pressure at time t during a dissipation test | MPa |
u0 | in situ, initial pore pressure | MPa |
u1 | pore pressure measured at location 1 | MPa |
u2 | pore pressure measured at location 2 | MPa |
u3 | pore pressure measured at location 3 | MPa |
z | penetration depth | m |
α | measured total angle between the vertical axis and the axis of the cone penetrometer | ° |
β1 | measured angle between the vertical axis and the projection of the axis of the cone penetrometer on a fixed vertical plane | ° |
β2 | measured angle between the vertical axis and the projection of the axis of the cone penetrometer on a vertical plane that is perpendicular to the plane of angle β1 | ° |
σvo | total overburden stress | MPa |