bs en iso 22476-3(spt)

BRITISH STANDARD BS EN ISO22476-3:2005

Geotechnical investigation and testing — Field testing —Part 3: Standard penetration test

ICS 93.020

+A1:2011IncorporatingcorrigendumFebruary 2007

National foreword

This British Standard is the UK implementation of EN ISO 22476-3:2005+A1:2011. It is identical to ISO 22476-3:2005, incorporating amendment 1:2011. It supersedes BS EN ISO 22476-3:2005, which is withdrawn.The start and finish of text introduced or altered by amendment is indicated in the text by tags. Tags indicating changes to ISO text carry the number of the ISO amendment. For example, text altered by ISO amendment 1 is indicated by !".The UK participation in its preparation was entrusted by Technical Committee B/526, Geotechnics, to Subcommittee B/526/3, Site investigation and ground testing.A list of organizations represented on this Subcommittee can be obtained on request to its secretary.The test in this standard is included in BS 1377-9:1990 (subclause 3.3) which is now withdrawn. Its use is covered in BS 5930:1999, clause 25.2, where there is reference to BS 1377-9:1990, clause 3.3. BS EN ISO 22476-3:2005+A1:2011 should now be used instead.It should be noted that the new test method requires a calibration of the equipment for energy ratio (ratio of the actual energy to the theoretical energy of the hammer).This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.

BS EN ISO 22476-3:2005+A1:2011

This British Standard waspublished under the authorityof the Standards Policy andStrategy Committeeon 30 January 2006

© The British StandardsInstitution 2012

Amendments/corrigenda issued since publication

Amd. No. Date Comments

16931Corrigendum No. 1

28 February 2007 Revision of National foreword

31 January 2012 Implementation of ISO amendment 1:2011 with CEN endorsement A1:2011

ISBN 978 0 580 74914 8

EUROPEAN STANDARD

NORME EUROPÉENNE

EUROPÄISCHE NORM

EN ISO 22476-3:2005+A1

ICS 93.020

English version

Geotechnical investigation and testing - Field testing - Part 3:Standard penetration test (ISO 22476-3:2005)

Reconnaissance et essais géotechniques - Essais en place- Partie 3 : Essais de pénétration au carottier (ISO 22476-

3:2005)

Geotechnische Erkundung und Untersuchung -Felduntersuchungen - Teil 3: Standard penetration test

(ISO 22476-3:2005)

This European Standard was approved by CEN on 4 November 2004.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.

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.

EUROPEAN COMMITTEE FOR STANDARDIZATIONC O M I T É E U R O P É E N D E N O R M A LI S A T I O NEUR OP ÄIS C HES KOM ITEE FÜR NOR M UNG

Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2005 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.

Ref. No. EN ISO 22476-3:2005: E

November 2011

Foreword

This document (EN ISO 22476-3:2005) has been prepared by Technical Committee CEN/TC 341 “Geotechnicalinvestigation and testing”, the secretariat of which is held by DIN, in collaboration with Technical CommitteeISO/TC 182 “Geotechnics”.

This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by July 2005, and conflicting national standards shall be withdrawn at the latest byJuly 2005.

EN ISO 22476 Geotechnical investigation and testing - Field testing has the following parts:

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

Part 10: Weight sounding test

Part 11: Flat dilatometer test

Part 12: Lefranc permeability test

Part 13: Water pressure tests in rock

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard : 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.

BS EN ISO 22476-3:2005+A1:2011 EN ISO 22476-3:2005+A1:2011 (E)

Foreword to amen A1

This document (EN ISO 22476-3:2005/A1:2011) has been prepared by Technical Committee CEN/TC 341 “Geotechnical Investigation and Testing", the secretariat of which is held by ELOT, in collaboration with Technical Committee ISO/TC 182 "Geotechnics".

This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2012, and conflicting national standards shall be withdrawn at the latest by May 2012.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.

mentd


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Reference numberISO 22476-3:2005(E)

INTERNATIONAL STANDARD

ISO22476-3

First edition2005-01-15

Geotechnical investigation and testing —Field testing —Part 3: Standard penetration test

Reconnaissance et essais géotechniques — Essais en place —

Partie 3: Essai de pénétration au carottier


ii


Contents

page

1 Scope ..............................................................................................................................................................1

2 Normative references ....................................................................................................................................1

3 Terms and definitions ...................................................................................................................................1

4 Equipment ...................................................................................................................................................... 2

5 Test Procedure...............................................................................................................................................4

6 Test results.....................................................................................................................................................5

7 Reporting ........................................................................................................................................................5

Annex A (informative) Correction factors ..............................................................................................................8A.1 Energy delivered to the drive rods...............................................................................................................8A.2 Energy losses due to the length of rods .....................................................................................................8A.3 Other correction factors................................................................................................................................8A.4 Effect of overburden pressure in sands......................................................................................................9A.5 Use of the correction factors........................................................................................................................9

Annex B (informative) Recommended method to measure the actual energy ................................................11B.1 Principle........................................................................................................................................................11B.2 Equipment .................................................................................................................................................... 11B.3 Measurements..............................................................................................................................................11B.4 Calculation.................................................................................................................................................... 12

Bibliography .............................................................................................................................................................. 14

iii

Foreword.................................................................................................................................................................... iv


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 beenestablished 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 Standardsadopted 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 22476-3 was prepared by the European Committee for Standardization (CEN) in collaboration withTechnical Committee ISO/TC 182, Geotechnics, Subcommittee SC 1, Geotechnical investigation and testing, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

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

— Part 10: Weight sounding test

— Part 11: Flat dilatometer test

— Part 12: Lefranc permeability test

— Part 13: Water pressure test in rock

— Part 14: Pumping tests

iv


1

1 Scope

The standard penetration test aims to determine the resistance of soils at the base of a borehole to the dynamicpenetration of a split barrel sampler and the recovering of disturbed samples for identification purposes (SPT). Ingravelly soils and in soft rocks a solid cone is also be used (SPT(C)).

The standard penetration test is used mainly to assess the strength and deformation parameters of cohesionless soils, but some valuable data may also be obtained in other soil types.

The basis of the test consists in driving a sampler by dropping a hammer of 63,5 kg mass on to an anvil or drivehead from a height of 760 mm. The number of blows (N) necessary to achieve a penetration of the sampler of300 mm (after its penetration under gravity and below a seating drive) is the penetration resistance.

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.

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1 anvil or drive headthat portion of the drive-weight assembly that the hammer strikes and through which the hammer energy passes intothe drive rods

3.2 hammerportion of the drive-weight assembly consisting of the 63,5 kg impact weight which is successively lifted and dropped to provide the energy that accomplishes the penetration and sampling

3.3 height of fall free fall of the hammer after being released

3.4 drive-weight assemblydevice consisting of the hammer, the hammer fall guide, the anvil and the drop system

3.5 drive rodsrods that connect the drive-weight assembly to the sampler

3.6 actual energyEmeasenergy delivered by the drive-weight assembly into the drive rod, immediately below the anvil, as measured


This part of ISO 22476 deals with the equipment requirements for, execution of and reporting on the penetration test to complement direct investigations (e.g. ISO 22475-1).

NOTE This part of ISO 22476 fulfils the requirements for standard penetration testing as part of geotechnical and testing in accordance with EN 1997-1 and EN 1997-2.

!

"

ISO 22475-1:2006, Geotechnical investigation and testing — Sampling methods and groundwater — Part 1: Technical principles for execution

!

"

standard

investigation

measurements

2

3.7 theoretical energyEtheorenergy as calculated for the drive weight assembly:

Etheor = m× g × h

where

m is the mass of the hammer;

g is the acceleration due to gravity;

h is the falling height of the hammer.

3.8 energy ratioErratio of the actual energy Emeas and the theoretical energy Etheor of the hammer expressed in percentage

3.9 N-valuenumber of blows required to drive the sampler for a test drive of 300 mm following the seating drive

4 Equipment

4.1 Drilling equipment

The drilling equipment shall be capable of providing a clean hole to ensure that the penetration test is performed onessentially undisturbed soil.

The area that is exposed in the base of the borehole prior to testing can influence the results and consequently the borehole diameter shall always be reported. A significant effect on the result can begin to occur when the diameteris 150 mm or more.

4.2 Sampler

The steel split barrel sampler shall have the dimensions indicated in Figure 1 and shall be provided with a non-return valve with sufficient clearance to permit the free flow of water or mud during driving.

The inner diameter of the sampler can be up to 3 mm larger than that of the shoe to allow for a liner. In gravellysand, a solid 60°cone instead of the standard shoe can be used. In this case the test shall be noted as SPT(C).


3

Key1 Drive shoe 2 Split barrel 3 Coupling 4 Non return valve (ball diameter: recommended 25 mm; ball seating: recommended 22 mm)5 Ball retaining pins6 Four vent holes (min diameter 12 mm) x Length of the drive shoe

Figure 1 — Longitudinal cross section of an SPT sampler without a provision for a liner (dimensions inmm)

4.3 Drive rods The drive rods shall have a stiffness that prevents buckling during driving.

Rods with a mass of more than 10,0 kg/m shall not be used.Only straight rods shall be used and periodic checks shall be made on site, including connections betweenconsecutive rods. When measured over the whole length of each rod the relative deflection shall not be greaterthan 1 in 1 200.


that of an AW rod for tests less than 20 m depth, and of a BW rod for greater depth. For definitions of AW and BW rods, see ISO 22475-1:2006, Table C.1.

The rod stiffness should be at least!

"

The straightness shall be checked by applying one of the following procedures.

Holding the rod vertically and rotating it. If the rod appears to wobble, the straightness is not acceptable.

Rolling the rod on a plane surface. If the rod appears to wobble, the straightness is not acceptable.

Sliding a straight hollow tube which is slightly longer than the rod over the rod. If the rod can pass tube without jamming, the straightness is acceptable.

!

"

At greater depth and/or with greater borehole diameters, the vertical alignment of the rod string should by installing appropriate stabilizers. Also, a stabilizer should be used at the collar at the and number of stabilizers shall be reported.

4.4 Drive weight assemblyThe drive weight assembly, of an overall mass not exceeding 115 kg, shall comprise: a steel hammer of 63,5 kg ± 0,5 kg conveniently guided to ensure minimal resistance during the drop; an automatic release mechanism which will ensure a constant free fall of (760 ± 10) mm, a negligible speed of

the hammer when released, and no induced parasitic movements in the drive rods; a steel drive head or anvil rigidly connected to the top of the drive rods. It may be an internal part of the

assembly, as with safety hammers.

4.5 Optional equipment4.5.1 Blow counterA device to measure mechanical or electric impulses can be placed on the system in order to count the number of the blows of hammer.

4.5.2 Penetration length measuring deviceThe penetration length is measured either by counting on a scale on the rods or by recording sensors. In this lattercase

, resolution shall be less than 1/100 of the measured length.

be ensuredtop of the borehole. Type

through the

4

5 Test Procedure 5.1 Equipment checks and calibration Prior to each test series, the sampler shall be checked to ensure that it is in proper condition (dimensions). The straightness of the rods shall be checked once on each new site and at least every 20 penetration tests at that site.

After each test, a visual check of the straightness of the rods shall be made.

At the test site, the height of fall, the friction free fall of the hammer, the proper condition of the anvil and themechanical release devices shall be checked for satisfactory operation which is to be ensured for the whole testseries. In addition, the proper functioning of the recording device shall be checked when automatic recordingequipment is used.

The precision of the measuring instruments – if applicable – shall be checked after any damage, overloading orrepair but at least once every six months, unless the manufacturer's manual requires shorter inspection intervals.Faulty parts shall be replaced. Calibration records shall be kept together with the equipment.

Energy losses occur e.g. due to friction at the hammer (velocity loss compared to the free fall) or due to energylosses during the hammer impact on the anvil. Therefore, the energy ratio Er of the equipment used has to beknown if the N-values are going to be used for the quantitative evaluation of foundations or for the comparisons ofresults. A certificate of calibration of the Er-value immediately below the driving head or anvil shall be available. NOTE A recommended method to determine the actual energy is given in Annex B.

5.2 Preparation of the borehole

The borehole shall be prepared for the specified test depth. The base of the borehole shall be clean and essentially undisturbed at the test elevation and without an upward water pressure gradient.

When drilling bits are used, they shall be provided with side discharge and not with

When testing below the groundwater table, particular care shall be taken to avoid any entry of water through thebottom of the borehole, as this will tend to loosen the soil or even lead to piping. For this purpose, the level of the water or drilling fluid in the borehole shall be maintained at a sufficient level above the groundwater level in the layer with the highest pressure (potential) at all times, even during withdrawal of the boring tools. Withdrawal shallbe performed slowly and with drilling tools providing enough clearance to prevent suction effects at the bottom.

When a casing is used, it shall not be driven below the level at which the test will start.

5.3 Test execution The sampler and the drive rods shall be lowered to the bottom of the borehole and then the hammer assemblyadded. The initial penetration shall be recorded. The sampler shall be penetrated over an initial or seating drive of150 mm applying the 63,5 kg hammer free falling 760 mm and the number of blows N0 shall be recorded. Then

The number of blows needed, shall be recorded during each of these increments (Nn). If a total of 50 blows for the testthe test may be finished (N = 50); in soft rocks it can be increased to 100 blows (N = 100).

In hard soils or in soft rocks where the penetration resistance is very high, the penetration for a certain number ofblows may be recorded.If the sampler advances below the bottom of the borehole under the static weight of the drive rods and hammerassembly on top, the corresponding penetration shall not be included, as seating drive and this information shouldbe reported. In no case shall any material reach the level of the non return valve.


The straightness shall be checked by applying one of the following procedures.

Holding the rod vertically and rotating it. If the rod appears to wobble, the straightness is not acceptable.

Rolling the rod on a plane surface. If the rod appears to wobble, the straightness is not acceptable.

Sliding a straight hollow tube which is slightly longer than the rod over the rod. If the rod can pass tube without jamming, the straightness is acceptable.

!

"

!The calibration check shall be made annually and after all changes, repairs and modifications to the driving equipment. "

!bottom discharge, from asafe distance above the test elevation. "

!

the sampler shall be driven in the same manner over a test drive of 300 mm. This shall be done increments (150 mm each). Alternat ively, four increments (75 mm each) may be used.

in at least two"

drive is reached,

!(N Nn Nn1 for 150 mm increments; N Nn Nn1 Nn2 Nn3 for 75 mm increments)."

The seating drive shall be 150 mm or 25 blows, whichever is reached first. If the seating drive is terminated at 25hall be recorded and the start of the test drive measured from that depth. "blows, the depth of penetration shall be

!

through the

of blows required for the 300 mm penetration after the seating drive is termed the penetration resistance of thatThe total number

soil layer.

5

5.4 Safety requirements

National safety regulations shall be followed; e.g. regulations for:

personal health and safety equipment;

clean air, if working in confined spaces;

ensuring the safety of the equipment.

6 Test results

The N-values can vary with test equipment and mode operation as well as geotechnical conditions (see Annex A). The corrections of Annex A shall be considered.

7 Reporting

7.1 Field report

7.1.1 General

At the project site, a field report shall be completed. This field report shall consists of the following, if applicable:

a) summary log according to ISO 22475-1 ;

b) record of measured values and test results.

All field investigations shall be reported such that third persons are able to check and understand the results.

7.1.2 Record of measured values and test results

At the project site, the following information shall be recorded for each test:

a) general information:

1) name of the client;

2) name of the contractor;

3) job or project number;

4) name and location of the project;

5) name and signature of test the equipment operator in charge;

b) information on the location of the test:

1) borehole number;

2) field sketch (to scale or not to scale);

3) ground elevation referred to a fixed point;

4) x, y, z-co-ordinates of the borehole;


The test results shall be reported and interpreted as the seating drive, N0, and the penetration blow resistance, N, or the test drive blow number, N. They shall be reported without any corrections or adjustments. adjustments. Corrections/adjustments may be considered for further interpretation.

!

"

! "

Samples recovered shall be recorded and handled in accordance with ISO 22475-1 . ! "

6

5) operation on land or water;

c) information on the used test equipment:

1) method of drilling and borehole diameter at the test level;

2) manufacturer, model and number of the test equipment;

3) type and size of drive rod;

4) type and size of hammer and release mechanism and weight of the drive head;

5) split-spoon sampler with or without liner;

6) solid cone (SPT(C)), if used;

7) the energy ratio Er and the calibration report;

d) information on the test procedure:

1) date and number of test;

2) documentation of the equipment check and calibration conducted in accordance with 5.1;

3) test record with:

the uncorrected N-value for each test, the corresponding depth interval;

the corresponding penetration, if the drive is terminated at 50 blows (or 100 in soft rocks);

penetration per blow in difficult ground conditions, if required;

penetration of the sampler under static weight;

4) record on recovered samples;

5) groundwater or artesian conditions, if known;

6) level of water or flushing medium during the preparation and execution of each test;

7) depth of test and casing;

8) weather conditions;

9) all unusual events or observations during the operation (e.g. low blow count, penetration without blows,temporary obstructions, malfunction of the equipment);

10) observations on the recovered sampler and/or rods;

11) all interruptions during the work, with time duration and change of rod;

12) reasons for early end of the test;

13) back-filling of penetration hole according to ISO 22475-1 , if required.


8) type and number of stabilizers, as applicable; ! "

— the number and size of test increments (two, 150 mm or four, 75 mm) !

"n, Nn1 for two incremements, or Nn, Nn1, N Nn2, Nn3 for four increments of penetration, if required;

"

!

— number of blows for the seating drive; ! "

— drive penetration if seating drive is terminated at 25 blows; ! "

! "

7

7.2 Test report

For checking the quality of the data, the test report shall include the following in addition to the information givenin 7.1:

a) field report (in original and/or computerised form);

b) graphical presentation of the test results;

c) corrections applied, if any, and the corrected N-value;

d) graphical representation with respect to depth of N and corrected N, if applicable;

e) any limitations of the data (e.g. irrelevant, insufficient, inaccurate or adverse test results);

f) name and signature of the field manager.

The test results shall be reported about in such a fashion that third persons are able to check and understand theresults.


8

Annex A(informative)

Correction factors

A.1 Energy delivered to the drive rods

Energy losses are induced by the hammer assembly due to frictional and other parasitic effects, which cause thehammer velocity at impact to be less than the free fall velocity. Further losses of energy are originated by theimpact on the anvil, depending on its mass and other characteristics. The type of machine, skill of the operator andother factors can also influence the energy delivered to the drive rods.

The value of the blow count, N, in sands is inversely proportional to the energy ratio Er so that:

Na × Er,a = Nb × Er,b (A.1)

For general design and comparison purposes in sands, the N-values should be adjusted to a reference energy ratioof 60 %, by the following equation:

NE

N60

r60 = (A.2)

where

N is the blow count;

Er is the energy ratio of the specific test equipment.

If a design method for sands has been elaborated for a value of Er different from 60 %, the corresponding correctedN-value should be determined based on equation A.1.

A.2 Energy losses due to the length of rods

If the length of rods is less than 10 m, the correction factors shown in Table A.1 may be applied to the blow countfor sands; for rod lengths greater than 10 m, no correction should be applied.

Table A.1 —Correction factors in sands due to rod length

Rod length below the anvil

m

Correction factorλ

>10

6 to 10

4 to 6

3 to 4

1,0

0,95

0,85

0,75

A.3 Other correction factors

If the inner diameter of the sampler is 3,0 mm larger than that of the shoe, as mentioned in 4.2 no correction isnecessary if a liner of appropriate thickness is used, such that the inside of the whole sampler is practically flush to


9

a uniform diameter of 35 mm. Nevertheless, attention should be paid to the eventual damage of the liner during driving and its influence on the corresponding blow count. If the liner is omitted, the additional clearance of theinside of the barrel with reference to the shoe leads to N-values between 10 % and 20 % lower in sands.

A.4 Effect of overburden pressure in sands

The effect of the overburden pressure in the N-value in sands may be taken into account, for example, by applyingto the measured N-value the correction factor CN given in Table A.2 with reference to the type of consolidation andthe density index ID.

Table A.2 — Correction factors CN for vertical stress σσσσv’ due to overburden of the soil in sands

Type of consolidation Density Index ID%

Correction factorCN

40 to 60 vσ'100

200

+Normallyconsolidated

60 to 80 v'200

300σ+

Overconsolidated v'70

170σ+

(σv' in kPa)

Another example of the correction for normally consolidated sand is the use CN given in the following equation:

'v

N98σ

=C (A.3)

Values of the correction factor CN larger than 2,0 and preferably 1,5 should not be applied.

The number of blows corrected to an energy ratio Er of 60 % and normalised for an effective vertical stressσv = 100 kPa is then:

60)( Nr601

CNEN

××= (A.4)

A.5 Use of the correction factors

Several correction factors have been mentioned in the previous paragraphs. As the existing design methods offoundations based on the SPT are of an empirical nature, only the corresponding correction factors should beused, unless duly justified.

If all the correction factors corresponding to this test procedure are applied for a design method based on anenergy ratio of 60 %, the following value for the final blow count would be obtained (without including the onementioned in A.3):

NCE

N ×××= Nr

60 60λ (A.5)

where


10

λ is the correction factor for energy losses due to the rod length in sand;

CN is the correction factor for vertical stress due to overburden of the soil in sand.


11

Annex B(informative)

Recommended method to measure the actual energy

B.1 Principle

The measurement of the energy transmitted to the drive rods can be made by means of an instrumented section ofrod positioned at a distance greater than 10 times the rod diameter below the point of hammer impact on the anvil(see Figure B.1).

For additional information see [1] to [6] of the bibliography.

Key1 Anvil 2 Part of instrumented rod 3 Drive Rod 4 Strain gauge (measuring transducer) 5 Accelerometer 6 Ground F Force dr Diameter of the rod

Figure B.1 — Instrumented rod (example)

B.2 Equipment

The measuring device consists of a removable instrumented rod fixed between the anvil and the head of rods. It includes:

system for measurement of vertical acceleration having a linear response up to 5 000 g;

system for measurement giving the axial deformation induced in the rod;

apparatus, with a resolution better than 1 × 10-5s, for viewing, recording and pre-treatment of the signals;

data processing system (data logger and computer).

When strain gauges are used for the measurement of the axial deformation, they should be uniformly distributedaround the instrumented rod.

B.3 Measurements

At each impact, check the correct operation of the measuring equipment and the sensors by displaying the resultsof measurements.

It should be verified that the signals from the accelerometers and of the gauges are null before and after theimpact.


12

For the measurement of the acceleration and deformation, the precision should be better than 2 % of the measured value.

B.4 Calculation

B.4.1 The force transmitted to the rods is calculated as follow:

( ) ( )tEAtF maa ε××= (B.1)

where

εm(t) is the measured axial strain of the instrumented rod at time t;

Aa is the cross-sectional area of the instrumented rod;

Ea is the Young’s modulus of the instrumented rod.

B.4.2 The particle velocity v(t) of the measurement section is calculated by the integration of the acceleration a(t)with respect to time t.

B.4.3 The basic equation for the energy E which passes into the drive rods is:

∫='

0

)()()'(t

dttvtFtE (B.2)

where

E(t’) is the driving energy which passes into the instrumented drive rod up to time t’ after the impact.

Various methods for developing the above equation and additional information can be found in the bibliography.

B.4.4 The hammer energy to take into account is the mean value obtained from at least five measurements:

∑=n

1meas

1 En

E (B.3)

B.4.5 The hammer energy ratio which characterises each dynamic penetrometer is given by:

1theor

measr ≤=

EE

E (B.4)

where

Etheor = m × g × h

h is the falling height of the hammer;

m is the mass of the hammer;

g is the acceleration due to gravity.


13

Hammer Energy Measurement Report

Type of dynamic probing SPT

Job number

Date of the test

Mass of the hammer m 63,5 kg

Falling height h 0,76 m

Etheor = m × g × h 473 J

Characteristics of the instrumented rod

Diameter dr

Length of the instrumented rod

Area A(Key see Figure B.1)

Modulus Ea

Force Particle velocity

Acceleration Axial deformation

Observations:

Emeas = Etheor =

Date

Name and signature of the equipment operator

Figure B.2 — Example of a hammer energy measurement report


14

Bibliography

[1] ASTM D 4633-86: Standard test method for stress wave energy measurements for dynamic penetrometertesting systems. American Society for Testing and Materials, Philadelphia 1986.

[2] Butler, J.J., Caliendo, J.A., Goble, G.G.: Comparison of SPT energy measurements methods. Proc. 1st Int.Conf. on Site Characterization, Atlanta 1998, Vol. 2, 901–905.

[3] Farrar, J.A.: Summary of Standard Penetration Test (SPT) energy measurements experience. Proc. 1st Int.Conf. on Site Characterization, Atlanta 1998, Vol. 2, 919–926.

[4] Gonin, H.: Du Pénétromètre dynamique au battage des pieux. - Revue Française de Géotéchnique No 76,1996.

[5] Gonin, H.: La formule des Hollandais ou le conformisme dans l'enseignement. Revue Française deGéotéchique No 87,1999.

[6] Matsumoto, T; Sekeguchi, H., Yoshida, H. & Kita, K.: Significance of two-point strain measurements in SPT.- Soils and Foundations, JSSMFE, Vol. 32, 1992, No 2, pp. 67-82.

[7] EN 1997-1, Eurocode 7: Geotechnical design — Part 1: General rules.

[8] EN 1997-2, Eurocode 7: Geotechnical design — Part 2: Ground investigation and testing.


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BS EN ISO22476-3:2005+A1:2011

bs en iso 22476-3(spt)

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