oSIST prEN ISO 22476-1:2005

SLOVENSKI oSIST prEN ISO 22476-1:2005

PREDSTANDARD
marec 2005
Geotechnical investigation and testing - Field testing - Part 1: Electrical cone and
piezocone penetration tests (ISO/DIS 22476-1:2005)
ICS 93.020 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD
DRAFT
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2005
ICS
English version
Geotechnical investigation and testing - Field testing - Part 1:
Electrical cone and piezocone penetration tests (ISO/DIS
22476-1:2005)
Reconnaissance et essais géotechniques - Essais en place
- Partie 1: Essais électriques de pénétration au cône et au
piézocone (ISO/DIS 22476-1:2005)
This draft European Standard is submitted to CEN members for parallel enquiry. It has been drawn up by the Technical Committee
CEN/TC 341.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other language
made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN ISO 22476-1:2005: E
worldwide for CEN national Members.

Foreword
This document (prEN ISO 22476-1:2005) has been prepared by Technical Committee
CEN/TC 341 "Geotechnical Investigation and Testing", the secretariat of which is held by DIN,
in collaboration with Technical Committee ISO/TC 182 "Geotechnics".

This document is currently submitted to the parallel Enquiry.

DRAFT INTERNATIONAL STANDARD ISO/DIS 22476-1
ISO/TC 182/SC 1 Secretariat: DIN
Voting begins on: Voting terminates on:
2005-01-27 2005-06-27
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION
Geotechnical investigation and testing — Field testing —
Part 1:
Electrical cone and piezocone penetration tests
Reconnaissance et essais géotechniques — Essais en place —
Partie 1: Essais électriques de pénétration au cône et au piézocone
ICS 93.020
ISO/CEN PARALLEL ENQUIRY
This draft International Standard is a draft standard developed within the European Committee for
Standardization (CEN) and processed under the CEN-lead mode of collaboration as defined in the
Vienna Agreement. The document has been transmitted by CEN to ISO for circulation for ISO member
body voting in parallel with CEN enquiry. Comments received from ISO member bodies, including those
from non-CEN members, will be considered by the appropriate CEN technical body. Should this DIS be
accepted, a final draft, established on the basis of comments received, will be submitted to a parallel two-
month FDIS vote in ISO and formal vote in CEN.
In accordance with the provisions of Council Resolution 15/1993 this document is circulated in
the English language only.
Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est distribué
en version anglaise seulement.
To expedite distribution, this document is circulated as received from the committee secretariat.
ISO Central Secretariat work of editing and text composition will be undertaken at publication
stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.
THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
© International Organization for Standardization, 2005

ISO/DIS 22476-1
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ii ISO 2005 – All rights reserved

ISO/DIS 22476-1
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 2
4 Symbols and abbreviations . 8
5 Equipment . 9
5.1 Geometry of the cone penetrometer. 9
5.2 Cone . 10
5.3 Friction sleeve. 11
5.4 Filter element. 12
5.4.1 General filter location. 12
5.4.2 Pore pressure u . 13
5.4.3 Pore pressure u . 13
5.4.4 Pore pressure u . 13
5.5 Gaps and soil seals . 14
5.6 Push rods . 14
5.7 Measuring system. 14
5.7.1 Accuracy. 14
5.7.2 Sensors for cone resistance and sleeve friction. 14
5.7.3 Sensor for pore pressure. 14
5.7.4 Sensor for inclination. 15
5.7.5 Measuring system for penetration length . 15
5.8 Thrust machine . 15
6 Test procedures . 15
6.1 Selection of cone penetrometer . 15
6.2 Selection of equipment and procedures according to required Application Class. 15
6.3 Position and level of thrust machine. 17
6.4 Preparation of the cone penetrometer. 18
6.5 Pushing of the cone penetrometer . 18
6.6 Use of friction reducer. 18
6.7 Frequency of logging parameters. 19
6.8 Registration of penetration length. 19
6.9 Dissipation test . 19
6.10 Test completion . 20
6.11 Equipment checks and calibrations . 20
7 Test results. 20
7.1 Measured parameters. 20
7.2 Correction of measurements. 20
8 Reporting . 22
8.1 General. 22
8.2 General reporting of test results . 23
8.2.1 General information. 23
8.2.2 Location of the test. 23
8.2.3 Test equipment . 23
8.2.4 Test procedure . 23
8.2.5 Measured parameters. 23
8.3 Choice of axis scaling . 24
DRAFT 2005
ISO/DIS 22476-1
8.4 Presentation of test results. 24
Annex A (normative) Maintenance, checks and calibration . 26
A.1 Maintenance and checks. 26
A.1.1 Linearity of push rods . 26
A.1.2 Wear of the cone . 26
A.1.3 Gaps and seals. 26
A.1.4 Pore pressure measuring system . 26
A.1.5 Maintenance procedures . 27
A.2 Calibration. 27
A.2.1 General procedures . 27
A.2.2 Calibration of cone resistance and sleeve friction. 28
A.2.3 Calibration of pore pressure and net area ratio. 28
A.2.4 Calibration of ambient temperature effects. 29
A.2.5 Calibration of penetration length sensor. 29
A.2.6 Calibration of the inclinometer . 29
Annex B (normative) Calculation of penetration depth. 30
Annex C (informative) Correction of sleeve friction for water pressure. 31
Annex D (informative) Preparation of the piezocone. 32
D.1 Saturation. 32
D.2 Slot filter. 32
Annex E (informative) Uncertainties in cone penetrometer testing . 33
Bibliography . 35
Figures
Figure 1 — Cross section of an example of a cone penetrometer.3
Figure 2 — Locations of measured pore pressures.5
Figure 3 — Penetration length and penetration depth.7
Figure 4 — Tolerance requirements for use of cone penetrometer (in mm).11
Figure 5 — Geometry and tolerances of friction sleeve (in mm) .12
Figure 6 — Correction of cone resistance and sleeve friction due to the unequal end area effect .22
Figure A.1 — Pressure chamber for determination of the end area ratios a and b .29
Tables
Table 1 — Types of cone penetration tests.15
Table 2 — Application Classes .17
Table A.1 — Control scheme for maintenance routines .27
iv © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 22476-1 was prepared by Technical Committee ISO/TC 182, Geotechnics, Subcommittee SC 1,
Geotechnical investigation and testing.
ISO 22476 consists of the following parts, under the general title Geotechnical investigation and testing —
Field testing:
 Part 1: Electrical cone and piezocone penetration tests
 Part 2: Dynamic probing
 Part 3: Standard penetration test
 Part 4: Menard pressuremeter test
 Part 5: Flexible dilatometer test
 Part 6: Self-boring pressuremeter test
 Part 7: Borehole jack test
 Part 8: Full displacement pressuremeter test
 Part 9: Field vane test
1)
 Part 10: Weight sounding test (TS)
1)
 Part 11: Flat dilatometer test (TS)
 Part 12: Mechanical cone penetration test
 Part 13: Plate loading test.

1)
TS Technical Specification.
DRAFT 2005
ISO/DIS 22476-1
Introduction
The electrical cone penetration test (CPT/CPTU) consists of pushing a cone penetrometer using a series of
push rods into the soil at a constant rate of penetration. During penetration, measurements of cone resistance
and sleeve friction can be recorded. The piezocone penetration test (CPTU) also includes the measurement of
pore pressures at or close to the cone. The test results may be used for interpretation of stratification,
classification of soil type and evaluation of engineering soil parameters. This standard is split in two parts:
Part 1 describes CPT and CPTU practice using electronic transducers. EN ISO 22476-13 describes CPT
practice using mechanical measuring systems.
vi © ISO 2004 – All rights reserved
DRAFT 2005
DRAFT INTERNATIONAL STANDARD ISO/DIS 22476-1
Geotechnical investigation and testing — Field testing — Part 1:
Electrical cone and piezocone penetration tests
1 Scope
This document deals with equipment requirements, the execution of and reporting on electrical cone and
piezocone penetration tests as part of geotechnical investigation and testing according to EN 1997-1 and
EN 1997-2.
The results from a cone penetration test are used to evaluate:
 stratification;
 soil type;
 soil density and in situ stress conditions;
 mechanical soil properties:
 shear strength parameters;
 deformation and consolidation characteristics.
Within the electrical cone and piezocone penetration test, two subcategories of the cone penetration test are
considered:
 The electrical cone penetration test (CPT) that includes measurement of cone resistance and sleeve
friction;
 The piezocone test (CPTU) that is a cone penetration test with the additional measurement of pore
pressure.
The CPTU is performed like a CPT with the measurement of the pore pressure at one or several locations on
the penetrometer surface.
NOTE CPT or CPTU are also used without measurement of sleeve friction.
This document specifies the following features:
a) the type of cone penetration test, according to Table 1;
b) the Application Class, according to Table 2;
c) the achievable penetration length or penetration depth;
d) the elevation of the ground surface or the underwater ground surface at the location of the cone
penetration test with reference to a datum;
e) the location of the cone penetration test relative to a reproducible fixed location reference point;
DRAFT 2005
ISO/DIS 22476-1
f) if applicable, the method of back filling of the hole in the soil resulting from the cone penetration test;
g) if applicable, the depths and duration of the pore pressure dissipation tests.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 8503, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-clean steel substrates.
ISO 10012-1, Quality Assurance Requirements for Measuring Equipment — Part 1: Metrological confirmation
system for measuring equipment.
EN ISO 14688-2, Geotechnical investigation and testing — Identification and classification of soil — Part 2:
Principles of a soil classification.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
average surface roughness
R
a
average deviation between the real surface of the probe and a medium reference plane placed along the
surface of the probe
3.2
cone
conical shaped bottom part of the cone penetrometer. When pushing the penetrometer into the ground, the
cone resistance is transferred through the cone to the load sensor
NOTE This document 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.
3.3
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
3.4
electrical cone penetration test
CPT where forces are measured electrically in the cone penetrometer
3.5
piezocone penetration test
CPTU
electrical CPT with measurement of the pore pressures at or close to the cone
2 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
Key
1 shaft 13 friction sleeve
2 gap between friction sleeve and shaft 14 friction sleeve sensor
3 friction sleeve 15 amplifier unit
4 gap between friction sleeve and cone 16 core sensor
5 cylindrical extension above base of cone 17 inclinometer
6 base of cone 18 water seal
7 face of cone 19 pressure sensor
8 apex of cone 20 soil seal
9 push rod connector 21 filter
10 soil seal 22 cone
11 electrical cable for signal transmission 23 penetrometer tip
12 water seal
Figure 1 — Cross section of an example of a cone penetrometer
3.6
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.
DRAFT 2005
ISO/DIS 22476-1
3.7
corrected cone resistance
q
t
measured cone resistance q corrected for pore pressure effects
c
3.8
corrected friction ratio
R
ft
ratio of the sleeve friction to the corrected cone resistance measured at the same depth
3.9
corrected sleeve friction
f
t
measured sleeve friction f corrected for pore pressure effects
c
3.10
dissipation test
measure of the pore pressure change recording the values of the pore pressure in time during a pause in
pushing while holding the cone penetrometer stationary
3.11
excess pore pressure
∆∆∆∆u , ∆∆∆∆u , ∆∆∆∆u
1 2 3
additional pore pressure at the at the level of the filter caused by the penetration of the cone penetrometer into
the ground:
∆ u = u − u (1)
1 1 0
∆ u = u − u (2)
2 2 0
∆ u = u − u (3)
3 3 0
3.12
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
3.13
friction ratio
R
f
ratio of the measured sleeve friction to the measured cone resistance at the same depth
3.14
friction reducer
local and symmetrical enlargement of the diameter of a push rod to obtain a reduction of the friction along the
push rods
3.15
friction sleeve
section of the cone penetrometer where sleeve friction is measured
3.16
in situ equilibrium pore pressure
u
original in situ pore pressure at filter depth
4 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
3.17
inclination
deviation of the cone penetrometer from the vertical
3.18
initial pore pressure
u
i
measured pore pressure at the start of the dissipation test
3.19
measured cone resistance
q
c
division of the measured force on the cone Q by the projected area of the cone A :
c c
q = Q / A (4)
c c c
3.20
measured pore pressure
u , u , u
1 2 3
fluid pressure measured during penetration and dissipation testing. The pore pressure can be measured at
several locations as follows (see Figure 2):
u on the cone face
u at the cylindrical extension of the cone
u directly behind the friction sleeve
Key
1 pore pressure filter location
2 friction sleeve
3 cone penetrometer
4 cone
Figure 2 — Locations of measured pore pressures
DRAFT 2005
ISO/DIS 22476-1
3.21
measured sleeve friction
f
s
division of the measured force acting on the friction sleeve F by the area of the sleeve A :
s s
f = F / A (5)
s s s
3.22
measuring system
all sensors and ancillary 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.
3.23
net area ratio
a
ratio of the cross-sectional area of the load cell or shaft of the cone penetrometer above the cone at the
location of the gap or groove where pore pressure can act, to the nominal cross-sectional area of the base of
the cone
3.24
net cone resistance
q
n
measured cone resistance corrected for the total overburden soil pressure
3.25
net friction ratio
R
fn
ratio of the sleeve friction to the net cone resistance measured at the same depth
3.26
normalised excess pore pressure
U
excess pore pressure during a dissipation test compared to the initial excess pore pressure
3.27
penetration depth
depth of the base of the cone, relative to a fixed horizontal plane (Figure 3)
3.28
penetration length
Sum of the length of the push rods and the cone penetrometer, reduced by the height of the conical part,
relative to a fixed horizontal plane (Figure 3)
NOTE The fixed horizontal plane usually corresponds to the level of the ground surface (on shore or off shore). This
may be different from the starting point of the test.
6 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
Key
1 fixed horizontal plane
2 penetration depth
3 penetration length
4 base of conical part of cone
Figure 3 — Penetration length and penetration depth
3.29
pore pressure at time t during dissipation test
u
t
pore pressure at time t during dissipation test
3.30
pore pressure ratio
B
q
ratio of the excess pore pressure at the u filter position to the net cone resistance
3.31
push rods
string of rods for the transfer of forces to the cone penetrometer
3.32
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 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.
3.33
thrust machine
equipment that pushes the cone penetrometer and rods into the ground along a vertical axis at a constant rate
of penetration
DRAFT 2005
ISO/DIS 22476-1
3.34
total overburden stress
σσσσ
vo
stress due to the total weight of the soil layers at the depth of the base of the cone
3.35
zero drift
absolute difference of the zero readings or reference readings of a measuring system at the start and
completion of the cone penetration test
3.36
zero reading
stable output of a measuring system if 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
4 Symbols and abbreviations
Symbol Name Unit
projected area of the cone mm²
A
c
area of load cell or shaft mm²
A
n
A area of friction sleeve mm²
s
cross sectional area of the bottom of the friction sleeve mm²
A
sb
cross sectional area of the top of the friction sleeve mm²
A
st
a net area ratio
pore pressure ratio
B
q
C correction factor for the effect of the inclination of the cone penetrometer relative to the
inc
vertical axis
diameter of the cone at a specified height mm
d
cone
d diameter of the cylindrical part of the cone mm
c
diameter of the filter mm
d
fil
diameter of the friction sleeve mm
d
excess pore pressure at filter locations 1, 2 and 3 MPa
∆u
1, 2, 3
measured force on the friction sleeve kN
F
s
f measured sleeve friction MPa
s
corrected sleeve friction MPa
f
t
height of the conical section of the cone mm
h
c
h length of the cylindrical extension of the cone mm
e
penetration length m
l
length of the friction sleeve m
l
s
measured force on the cone kN
Q
c
measured cone resistance MPa
q
c
q net cone resistance MPa
n
8 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
Symbol Name Unit
q corrected cone resistance MPa
t
average surface roughness
R µm
a
R friction ratio %
f
corrected friction ratio %
R
ft
net friction ratio %
R
fn
t time s
time needed for 50 % pore pressure dissipation s
t
normalised excess pore pressure MPa
U
pore pressure MPa
u
pore pressure at the start of the dissipation test MPa
u
i
u pore pressure at time t in a dissipation test MPa
t
in situ, initial pore pressure MPa
u
o
u pore pressure in the face of the cone MPa
pore pressure in the gap between the cone and the sleeve MPa
u
pore pressure measured above the friction sleeve MPa
u
z penetration depth m
measured total angle between the vertical axis and the axis of the cone penetrometer °
α
angle between the vertical axis and the axis and the projection of the cone penetrometer on °
α
x, y
a fixed vertical plane
angle between the vertical axis and the axis and the projection of the cone penetrometer on °
β
a vertical plane that is perpendicular to the plane of angle α
total overburden stress MPa
σ
vo
5 Equipment
5.1 Geometry of the cone penetrometer
The cone penetrometer has internal load sensors for the measurement of force on the cone (cone resistance),
side friction on the friction sleeve (sleeve friction) and if applicable pore pressure at one or several locations
on the surface of the cone penetrometer. An internal inclinometer is included for measurement of the
inclination of the penetrometer to meet the requirements of the Application Classes 1, 2 and 3 as given in
Table 2.
NOTE Other sensors can be included in the cone penetrometer.
The axis of all parts of the cone penetrometer shall be coincident.
Cone penetrometer design should aim for a high net area ratio and the end area of the top end of the friction
sleeve should preferably be equal or slightly greater than the cross sectional area of the lower end.
The dimensional tolerances mentioned in this section are operational tolerances. Manufacturing tolerances
should be stricter. The tolerance on surface roughness is a manufacturing tolerance.
DRAFT 2005
ISO/DIS 22476-1
The surface roughness as mentioned in 5.2 and 5.3 refers to average roughness R determined by a surface
a
profile comparator according to ISO 8503, or equivalent. The intention of the surface roughness requirement
is to prevent the use of an "unusually smooth" and "unusually rough" friction sleeve. Steel, including hardened
steel, is subject to wear in soil (in particular sands) and the friction sleeve develops its own roughness with
use. It is therefore important that the roughness at manufacture approaches the roughness acquired upon
use. It is believed that the surface roughness requirement will usually be met in practice for common types of
steel used for penetrometer manufacture and for common ground conditions (sand and clay). The effort
required for metrological confirmation may thus be limited in practice.
5.2 Cone
The cone consists of a conical part and a cylindrical extension. The cone shall have a nominal apex angle of
60°. The cross-sectional area of the cone shall be 1 000 mm , which corresponds to a diameter of 35,7 mm.
Depending on ground conditions, cones with a diameter between 25 mm (A = 500 mm ) and 50 mm
c
(A = 2 000 mm ) may be used for special purposes, without the application of correction factors. The
c
geometry and tolerances shall be adjusted proportionately to the diameter.
The diameter of the cylindrical part shall be within the tolerance requirement as shown in Figure 4:
35,3 mm ≤ d ≤ 36,0 mm
c
The length of the cylindrical extension shall be within the tolerance requirement:
7,0 mm ≤ h ≤ 10,0 mm
e
The height of the conical section shall be within the following tolerance requirement:
24,0 mm ≤ h ≤ 31,2 mm
c
If a filter is put at position u the diameter of the filter element itself may be larger than the required
dimensions (see also 5.3 and 5.4).
The surface of the cone shall be smooth.
The cone should be manufactured to a surface roughness R less than 5 µm.
a
The cone shall not be used if a visual check indicates that it is asymmetrically worn, even if it otherwise fulfils
the tolerance requirements.
10 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
Key
1 Minimum shape of the cone after wear
2 Maximum shape of the cone
Figure 4 — Tolerance requirements for use of cone penetrometer (in mm)
5.3 Friction sleeve
The friction sleeve shall be placed just above the cone. The distance due to gaps and soil seals shall not be
more than 5,0 mm.
The nominal surface area shall be 15 000 mm . Tolerance requirements are shown in Figure 5.
Friction sleeves with an external diameter between 25 mm and 50 mm may be used for special purposes if
used with cones of the corresponding diameter without the application of correction factors. The ratio of the
length and the diameter should preferably be 3,75. Ratios of 3 to 5 are allowable.
Conical wear affects the measurement of sleeve friction. It should be taken into account for accuracy of the
sleeve friction measurements.
The diameter of the friction sleeve shall be equal to the maximum diameter of the cone, with a tolerance of
0 mm to + 0,35 mm.
DRAFT 2005
ISO/DIS 22476-1
A = 15 000 mm
s
d ≥ d
2 c
d < d + 0,35
2 c
d < 36,1
Figure 5 — Geometry and tolerances of friction sleeve (in mm)
The geometry and tolerances of the friction sleeve shall be within the tolerance requirement as shown in
Figure 5:
d ≤ d < d + 0,35 mm
c 2 c
and
d < 36,1 mm
The length of the cylindrical part shall be within the tolerance requirement:
132,5 mm < l ≤ 135,0 mm
s
The friction sleeve shall be manufactured to a surface roughness of 0,4 µm ± 0,25 µm, measured in the
longitudinal direction.
5.4 Filter element
5.4.1 General filter location
A filter position in or just behind the cylindrical extension of the cone is recommended like in Figure 2. Other
filter locations can be accepted.
NOTE 1 Measurements at different filter locations in addition to the recommended ones can give valuable information
about the soil conditions.
12 © ISO 2004 – All rights reserved
DRAFT 2005
ISO/DIS 22476-1
NOTE 2 The measured pore pressure is influenced by soil type, in situ pore pressure and filter location on the surface
of the cone penetrometer. The pore pressure consists of two components, the original in situ pore pressure and the
additional or excess pore pressure caused by the penetration of the cone penetrometer into the ground.
The filter should not influence the measured cone resistance or sleeve friction.
Tolerances on filter dimensions are tolerances at the start of a test.
The pore pressure measuring system shall be saturated at the start of the test.
The filter should remain saturated, even when the cone penetrometer is penetrating an unsaturated layer.
-
Porous filters should have a pore size between 2 µm and 20 µm, matching a permeability between 10 4 m/s
–5
and 10 m/s. Filter materials that get clogged by fine particles should be avoided.
NOTE 3 The following types of material have been used with good experience in soft normally consolidated clay:
sintered stainless steel or bronze, carborundum, ceramics, porous PVC and HDPE.
The cone penetrometer shall be designed in such a way that it is easy to replace the filter and that the liquid
chamber is easy to saturate (see 6.4).
NOTE 4 With regard to the choice of saturating liquid, saturation of pore pressure measurement system, and use of
slot filters, see Annex D.
Filters should be replaced before each test.
5.4.2 Pore pressure u
The surface of the filter shall fit the shape of the cone: it shall not protrude more than 0,5 mm and shall not
recess.
The deviation of the surface of the filter to the surface of the cone should be assessed visually.
The filter element should be positioned in the middle third of the conical part.
5.4.3 Pore pressure u
The filter element shall be placed in or just behind the cylindrical part of the cone. The diameter of the filter at
the start of test shall correspond to the diameter of the cylindrical part of the cone and the friction sleeve, with
a tolerance limit 0,0 mm to + 0,2 mm. The filter can be larger, but shall never be smaller than the diameter of
the cylindrical part of the cone. The filter shall not have a larger diameter than the friction sleeve:
d – 0,2 mm ≤ d ≤ d
2 fil 2
d ≤ d ≤ d + 0,2 mm
c fil c
NOTE Filter position u gives more consistent results for classification and interpretation purposes.
To correct for pore pressure effects on cone resistance the filter element should be located in the groove
between the cone and the friction sleeve. Since this is not possible in practice, the filter should be located in
the cylindrical part of the cone.
5.4.4 Pore pressure u
The diameter of the filter shall correspond to the diameter of the friction sleeve with a tolerance limit of 0,0 mm
to 0,2 mm, i.e. the diameter of the filter shall not be not smaller than the diameter of the friction sleeve:
d ≤ d ≤ d + 0,2 mm
2 fil 2
DRAFT 2005
ISO/DIS 22476-1
The filter element should be placed immediately above the groove between the friction sleeve and the shaft of
the cone penetrometer.
5.5 Gaps and soil seals
Gaps between the different parts of the cone penetrometer shall not exceed 5 mm. A soil seal shall protect the
gap to prevent soil particles affecting the measurement.
The soil seal shall deform easily relative to the load cell and other elements in the penetrometer, to prevent
the transfer of significant forces through the gap.
5.6 Push rods
The push rods shall have the same diameter as the cone for at least 400 mm measured from the base of the
cone for cones with base area of 1 000 mm . For other size cones, this distance shall be scaled linearly in
proportion to the diameter.
For Application Class 4 CPT the straightness of the push rods, as specified in A.1, shall be determined at
regular intervals. Prior to each use, the straightness shall be checked visually.
Friction along the push rods can be reduced by a local increase in the rod diameter (friction reducer). The
friction can also be reduced by lubrication of the push rods, for instance by mud injection during the test. The
injection point should be at least 400 mm above the base of the cone for cones with base area of 1 000 mm .
For other size cones, this distance shall be scaled linearly in proportion to the diameter of the cone.
Above the ground level the push rods should be guided by rollers, a casing or similar device to reduce the risk
of buckling. The push rods may also be guided by a casing in water or soft strata to avoid buckling.
The push rods should be chosen with respect to the data signal transmission system chosen.
NOTE The push rods can also be used to support and/or protect parts of the measuring system. With acoustic
transfer of sounding results the rods are also used for transmission of data.
5.7 Measuring system
5.7.1 Accuracy
The resolution of the measuring system shall be better than one-third of the accura
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