ISO en 22476 15 MeasuringWhilstDrilling

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Latest date for receipt of comments: 20 June 2014 Project No. 2013/03055

Responsible committee: B/526/3 Site investigation and ground testing

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Date: 20 February 2014Origin: European

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Title: Draft BS EN ISO 22476-15 Geotechnical investigation and testing - Field testing

Part 15: Measuring while drilling

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© ISO 2014

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Geotechnical investigation and testing — Field testing —

Part 15: Measuring while drilling

Reconnaissance et essais — Essais de sol —

Partie 15: Enregistrement des paramètre de forages

Reference numberISO/DIS 22476-15:2014(E)

DRAFT INTERNATIONAL STANDARD

ISO/DIS 22476-15

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Voting begins on: Voting terminates on:2014-02-20 2014-07-20

ICS: 93.020



ISO/DIS 22476-15:2014(E)

ii © ISO 2014 – All rights reserved

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ISO/WD 22476-X

Contents Page

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

2 Normat ive references ............................................................................................................................ 2

3 Terms and def in it ions ........................................................................................................................... 2

4 Symbols and abbreviated terms .......................................................................................................... 4

5 Equipment .............................................................................................................................................. 6

5.1 Dri ll ing equ ipment ................................................................................................................................. 6

5.2 Measuring system ................................................................................................................................. 7

5.2.1 Sensors for hydraul ic p ressures ......................................................................................................... 7

5.2.2 Measur ing sys tem for penetration length ........................................................................................... 7

5.2.3 Measur ing system for flushing medium flow ..................................................................................... 8

5.2.4 Measur ing sys tem for rotat ional speed .............................................................................................. 8

5.2.1 Measur ing o f hammering energy ......................................................................................................... 8

5.2.5 Reflected vibrations .............................................................................................................................. 8

5.2.2 Time ........................................................................................................................................................ 8

6 Specifi c requi rements for MWD measurements ................................................................................ 9

6.1 Select ion of measured parameters ...................................................................................................... 9

6.2 Select ion of equipment and procedures ........................................................................................... 10

6.2.1 MWD Class 1 ........................................................................................................................................ 11

6.2.2 MWD Class 2 ........................................................................................................................................ 11

6.2.3 MWD Class 3 ........................................................................................................................................ 11

6.3 Factors influencing MWD resu lts ...................................................................................................... 12

6.3.1 Too l in fluence ...................................................................................................................................... 12 6.3.2 Dri ll ing rig in fluence ............................................................................................................................ 13

6.3.3 Operator in fluence ............................................................................................................................... 13

7 Test procedures ................................................................................................................................... 13

7.1 General ................................................................................................................................................. 13

7.2 Posi tion and level of dril ling machine ............................................................................................... 13

7.3 Preparation of the measurement ....................................................................................................... 13

7.4 Dri ll ing procedure ................................................................................................................................ 14

7.5 Frequency of logging parameters ..................................................................................................... 14

7.6 Registration of penetration leng th ..................................................................................................... 15

7.7 Test complet ion ................................................................................................................................... 15

7.8 Equipment checks and calibrations .................................................................................................. 16

7 Test resul ts .......................................................................................................................................... 16

7.9 General ................................................................................................................................................. 16

7.10 Calculated parameters ........................................................................................................................ 16

7.10.1 Penetrat ion rate ................................................................................................................................... 16

7.10.2 Down-thurst pressure ......................................................................................................................... 16

7.10.3 Net down-thrust pressure ................................................................................................................... 16

7.10.4 Flushing medium pressure................................................................................................................. 17

7.10.5 Dri ll head rotat ional to rque................................................................................................................. 17

8 Report ing .............................................................................................................................................. 17

8.1 General ................................................................................................................................................. 17

8.2 General report ing of test results ........................................................................................................ 18

8.2.1 General in formation ............................................................................................................................ 18

8.2.2 Locat ion of the test ............................................................................................................................. 18

8.2.3 Test equipment .................................................................................................................................... 18

8.2.4 Test procedure ..................................................................................................................................... 19

© ISO 2010 – All rights reserved iii



ISO/WD 22476-X

8.2.5 Measu red parameters ......................................................................................................................... 19

Annex A (normative) Calib rations and field check ....................................................................................... 20

A.1 Calibration ........................................................................................................................................... 20

A.1.1 Sensor calibrations............................................................................................................................. 20

A.1.2 Funct ional ver if ication ....................................................................................................................... 20

A.2 Field check .......................................................................................................................................... 21

Annex B (informative) Posit ioning of sensors .............................................................................................. 22

B.1 General ................................................................................................................................................. 22

B.2 Down-thrust and torque pressu res ................................................................................................... 22

B.3 Holdback pressure.............................................................................................................................. 22

B.4 Flushing medium pressure ................................................................................................................ 23

B.5 Flushing medium ci rculation rate ..................................................................................................... 23

B.6 Penet rat ion length .............................................................................................................................. 23

B.7 Dri ll head rotat ional speed ................................................................................................................. 24

B.8 Reflected vibrations ........................................................................................................................... 24

Annex C (informative) Appl ication of dr il ling parameters ............................................................................ 27

C.1 The dril ling parameters in terp retat ion .............................................................................................. 27

C.1.1 Penet rat ion rate ................................................................................................................................... 27

C.1.2 Net down-thrust .................................................................................................................................. 27

C.1.3 Flushing medium pressure ................................................................................................................ 27

C.1.4 Torque .................................................................................................................................................. 28

C.1.5 Conclus ion .......................................................................................................................................... 28

C.2 Compound parameters ...................................................................................................................... 29

C.2.1 Penet rat ion res is tance ....................................................................................................................... 29

C.2.2 Al teration index ................................................................................................................................... 30

C.2.3 Somerton Index ................................................................................................................................... 30

C.2.4 Energy .................................................................................................................................................. 31

C.2.5 Computerized interp retation .............................................................................................................. 33

Annex D (informative) Graphical presentation of drilling parameter .......................................................... 35

D.1 Choice of axis scaling ........................................................................................................................ 35 D.2 Presentat ion of test resul ts ............................................................................................................... 35

iv © ISO 2010 – All rights reserved



ISO/WD 22476-X

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 ISOtechnical 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 andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with theInternational 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 patentrights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 22476-X was prepared by the European Committee for Standardization (CEN) Technical CommitteeCEN/TC 341, Geotechnical investigation and testing, in collaboration with Technical Committee ISO/TC 182,Geotechnics, Subcommittee SC 01, Geotechnical testing, in accordance with the Agreement on technicalcooperation 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 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

Part 9: Field vane test

Part 10: Weight sounding test

Part 11: Flat dilatometer test

Part 12: Mechanical cone penetration test

Part 13: Plate loading test

Part X: Measuring while drilling

© ISO 2010 – All rights reserved v



ISO/WD 22476-X

Introduction

ISO 22476-X specifies the technical principles for measuring equipment requirements, the execution andreporting on the parameters of investigation drilling process for geotechnical purposes.

The measuring while drilling (MWD) method deals with the recording of the machine parameters during thedrilling process. This can be done manually or with the use of computerized systems which monitor a series ofsensors installed on rotary and/or percussive drilling equipment. These sensors continuously andautomatically collect data on all aspects of drilling, in real time, without interfering with the drilling progress.The data are displayed in realtime and are also recorded for further analysis. Examples for interpretation ofthe results are presented in an annex.

The method shall be used for its own purpose and the borehole can be used for other application such as

installation of monitoring equipments or realisation of expansion test. The interpretation of the MWD resultscan be done in relation with the information provided by sampling.

It should be noted that measured and calculated drilling parameters are relative and dependant of the testconditions, procedures and equipment.

The recording of the drilling parameters during soil grouting, drilling of nails, anchors or piles are out of thescope of this standard.

vi © ISO 2010 – All rights reserved



WORKING DRAFT ISO/WD 22476-X

Geotechnical investigation and testing — Field testing — Part X:Measuring while dril ling

1 Scope

This document deals with technical principles for measuring equipment requirements, the execution of and reportingon the parameters of measuring while drilling method as part of geotechnical investigation and testing according toEN 1997-1 and EN 1997-2 (for the drilling process, see figure 1).

The measured, calculated and derived drilling parameters (e.g. depth, advancement rate, pull down pressure, torque,rotation rate, mud pressure, mud flow, vibration, penetration resistance, soil-rock resistance) can produce useful dataabout the lithology of the layers for a reliable geotechnical model, their density or weathering, the localisation of voidsor faults in the ground, the depth to rock and other properties like permeability.

The present document describes the procedure for the logging (measuring versus depth) of drilling parameters andhow to report them for subsurface characterization. It applies in natural soils, treated or untreated fills and in soft andhard rocks, either on land or off-shore.

After the MWD test, the borehole can be used for other purpose such as installation of monitoring equipments.

Key

1 drill rig 4 drill rods

2 borehole 5 flushing medium circulation system

3 drilling tool

Figure 1 — Princip le of a drilling process

© ISO 2010 – All rights reserved 1



ISO/WD 22476-X

2 Normative references

The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenced document

(including any amendments) applies.

EN 791 : Drill rigs — Safety.

ISO 710 Graphical symbols for use on detailed maps, plans and geological cross-sections - Part 1: Generalrules of representation

ISO 710-2 Graphical symbols for use on detailed maps, plans and geological cross-sections -- Part 2:Representation of sedimentary rocks

ISO 710-3 Graphical symbols for use on detailed maps, plans and geological cross-sections -- Part 3:Representation of magmatic rocks

ISO 1219-1 Fluid power systems and components - Graphic symbols and circuit diagrams - Part 1: Graphicsymbols for conventional use and data-processing applications

EN 1997-1, Eurocode 7: Ground investigation and testing – Part 1: General rules.

EN 1997-2, Eurocode 7: Ground investigation and testing – Part 2: Design assisted by laboratory and fieldtesting.

EN ISO 10012, Measurement management systems – Requirements for measurement processes andmeasuring equipment.

ENV 13005:1999, Guide to the expression of uncertainty in measurement.

ISO 14688-1, Geotechnical investigation and testing – identification and classification of soil – Part 1:identification and description.

ISO 14689-1, Geotechnical investigation and testing – identification and classification of rock – Part 1:identification and description.

EN ISO 22475-1, Geotechnical investigation and testing – Sampling by drilling and excavation and groundwater measurements – Part 1: Technical principles for execution.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN ISO 22475-1 and the followings apply.

3.1borehole

hole of any predetermined diameter and length formed in any geological formation or man made material byrotary or percussive drilling tools or a combination of them

NOTE Investigations carried out in such a hole may be to recover rock, soil or water samples from a specified depth or tocarry out in situ tests and measurements

3.2drilling

process by which a borehole is produced in any geological formation by rotary, rotary percussive, percussive orthrust methods and in any predetermined direction in relation to the drill rig

2 © ISO 2010 – All rights reserved



ISO/WD 22476-X

NOTE Cuttings produced by the process are continuously removed by the flushing medium.

3.3drilling method

technique employed to produce and stabilise the borehole, and at the same time, remove cuttings from the drill bit

3.4drilling tool

device, which is attached to or an integral part of the drill string, used for penetrating the geological formation as acutting tool

3.5drill rigmachine of the appropriate power which, when used in conjunction with the correctly selected in-hole equipment willcarry out the drilling function

3.6flushing medium

fluid medium (air, water or water-air-mixture) continuously supplied to the drilling tool to facilitate the removal ofcuttings to the surface, stabilise the borehole, support the preservation of geological information, lubricate and cool thedrilling tool

3.7flushing additive

additive, which when added to the flushing medium will affect or change its physical condition

NOTE Bentonite and polymers are flushing additives for example.

3.8cuttings

particles of geological formations formed in the borehole by the cutting action of the drilling tool and carried to the

surface by the flushing medium.

3.9drill rig parameters

functional parameters of the drill rig recorded during drilling (mainly hydraulic pressures, penetration rate, rotationspeed, fluid pressure and flow, etc.).

3.10drilling parameters

parameters derived from drill rig parameters characteristics of drilling tool action on the material of the geologicalformation.

3.11

penetration lengthlength measured in the axis of the borehole between ground level and the drilling tool.

3.12penetration raterate of penetration of drilling tool in the ground.

3.13down thrust (feed) pressure

thrust pressure applied on drilling tool.

3.14holdback (retain) pressure

retain pressure limiting penetration rate due to safety requirements.




ISO/WD 22476-X

3.15flushing medium pressure

flushing medium pressure at the level of the drilling tool.

3.16

torquedrill head rotational torque

3.17rotation speed

drill head rotational speed

3.18flushing medium circulation rate

flushing medium circulation rate output of drilling tool down the hole

3.19flushing medium recovery rate

flushing medium circulation rate output of borehole

3.20reflected vibration

acceleration due to elastic rebound of rods compressed by hammer impact

3.21time

time

3.22operator

qualified person who carries out the test.

4 Symbols and abbreviated terms

Symbol Name Unit

A measured penetration length m

α efficiency coefficient of down-thrust work -

β efficiency coefficient of torque work -

γ efficiency coefficient of hammering work -

CR measured drill head rotational torque kN.m

CR max maximum measured drill head rotational torque kN.m

Do external diameter of drill bit m

E calculated drilling energy J

ES calculated specific energy J




ISO/WD 22476-X

ER measured reflected vibrations J

f hammer frequency Hz

Fmax maximum down thrust force kN

Hmax maximum hold back force kN

I A calculated alteration index -

N measured rods number -

P measured hydraulic pressure in feed motor or cylinder MPa

pCR measured hydraulic pressure in torque motor MPa

pCR max maximum measured hydraulic pressure in torque motor MPa

pH measured hold back pressure MPa

PI calculated flushing medium pressure at output of the drilling tool MPa

PE calculated net down-thrust (or feed thrust) applied on drilling tool MPa

PF measured flushing medium pressure at output of the pump MPa

pM measured hammering pressure MPa

pmax maximum measured down-thrust pressure MPa

PO calculated raw down-thrust (or feed thrust) applied on drilling tool MPa

PH calculated holdback pressure MPa

pH max maximum measured holdback pressure MPa

PR penetration resistance s/0,2 m

QI measured borehole drilling fluid inflow l/h

QO measured borehole drilling fluid outflow l/h

RSR calculated soil-rock resistance MPa/m/s

Sd calculated Somerton index -

SO measured area removed by drill bit (=/= drilling tool surface) m2

t measured time S

V A penetration rate m/h

VR measured drill head rotational speed Rpm

WH weight of rotary head MN




ISO/WD 22476-X

WR weight of drill rod MN

z measured depth m

zw measured ground water table depth m

5 Equipment

In general, drilling parameters are classified in three categories:

parameters imposed by the method (type of drilling tool and diameter, nature of the fluid medium, limits ofmachine performance and injection system) and scalable parameters unmanaged (tools wear, changes in thecomposition of the fluid).

parameters set by the operator (PO down-thrust, VR drill head rotational speed, QI flushing medium circulationrate)

parameters depending on the response of the ground (V A penetration rate, CR torque, PI injection pressure)

The drilling parameters are calculated from the drill rig measurements either directly or using calibration relations.

5.1 Drilli ng equipment

Drilling machines with appropriate stability, power and equipment such as drilling rods and bits shall be selected inorder to achieve the required depth and stability of the borehole. The drilling equipment shall be of the appropriatesize and type in order to produce the required quality of MWD test. The drilling rig and equipment shall allow all drilling

functions to be adjusted accurately.

NOTE The drill rig shall be chosen based on the project objectives with sufficient capacity to penetrate the various geologiclayers and equipped with the appropriate drilling tools.

Drill head and feed mechanism shall be hydraulically operated to allow drilling parameter monitoring.

Only top hammer drilling shall be used. Both air-driven and hydraulic powered hammers can be selected and thesystem shall allow hammer pressure regulation.

The equipment shall be loaded or anchored to limit movements of the drilling machine relative to ground level whilethe penetration occurs.

The drilling flow pump shall comply with the following characteristics:

- provide a constant flow under constant pressure, pumps creating pulsation shall be avoided (e.g. single pistonpump);

- achieve a minimum of 30 bars (unless otherwise noted);

- have a sensitive and calibrated pressure gauge mounted directly on the pump outflow;

- allow a 0.8 to 1 m per second cutting return (depending on fluid viscosity).

NOTE When water from domestic water supply network is used a minimum difference of pressure should compensate thepressure loss thus it can be only used for shallow drilling.

The drill string shall be free of leaks and the diameter should remain constant throughout the project.




ISO/WD 22476-X

Prior to each use, the straightness of rods shall be checked visually. The deviation of the linearity of the rods shall notexceed 5 mm from the centreline for 3 m long rod. The straightness of the push rods, shall be determined at regularintervals.

The drilling tool used for MWD method shall be drill bit type acting in rotary or rotary percussion drilling. The use for

other drilling technique shall be avoided.

NOTE According to EN ISO 22475-1, the Measuring While Drilling method provides only cuttings and is therefore in samplingcategories C.

NOTE Measuring while coring can be performed but care shall be taken during the interpretation of the data.

5.2 Measuring system

The automatic measurement system includes (see figure 2):

a data recorder used to monitor, record and analyze process and equipment behaviour,

a data acquisition system including a signal converter (sometime part of data recorder),

transducers setted on the machine. To limit the influence of the positioning of sensors on the recordedmeasurements, it is necessary to follow the suggested instructions for positioning all sensors (see annex B).

The manual measurement includes:

depth according to time or time for a penetration of 0.2 m,

parameters read by the operator on gauges.

The measuring system shall give a real time display of the readings to allow adjustments to the drilling processaccording to the observed progress of the test.

5.2.1 Sensors for hydrauli c pressures

The following pressures are usually measured:

a) Down-thrust pressure p and torque pressure pCR;

b) Holdback pressure pH. Complementary to the down-thrust, this pressure pH shall be measured to calculate the netdown-thrust applied on the bit. Holdback pressure is the hydraulic pressure prevailing in return line;

NOTE Differential pressure transducer can be used to measure the net down thrust directly.

NOTE Down-thrust force can be directly measured by load sensor.

NOTE The braking action preventing the equipment falling into the hole when a cavity is encountered, is the main cause of theerroneous interpretation of drilling parameters.

c) Flushing medium pressure PF.

Measurement of these pressures shall be carried out in the manual procedure on pressure gauges and in theautomatic procedure using transducers placed on hydraulic circuit.

5.2.2 Measuring system for penetration length

Measurement of drilling tool penetration length shall be carried out between the top of the mast and the drill rod.




ISO/WD 22476-X

The penetration depth shall be determined, for example:

in the manual procedure using a tape,

in the automatic procedure, using a rotary encoder fitted to a winch drum assembly.

NOTE Some systems have a device to eliminate ascending movements of tool (due to addition of rods, borehole sweeping orcleaning, rebounds, etc.).

5.2.3 Measuring system for flushing medium flow

Flow shall be measured using mechanical flow meters such as turbine flow meter that translates the mechanicalaction of the turbine rotating in the liquid flow around an axis into a user-readable rate of flow and accept liquid of highviscosity such as mud.

NOTE The measurement of drilling fluid return flow (outflow) QO at the exit of the borehole can provide an estimation of thevolume of fluid exchanged (absorbed or provided from confined aquifer) with ground.

5.2.4 Measuring system for rotational speed

Rotational speed measurement shall be done:

in the manual procedure using a tachometer,

in the automatic procedure with a rotation or proximity sensor that counts the passage of a metallic element.

5.2.1 Measuring of hammering energy

Hammering energy shall be measured using a pressure transducer to measure the pressure p M used to activate thehammer and the blow frequency f (alternatively determined by a flow meter).

5.2.5 Reflected vibrations

Vibration due to percussive reflected waves generated when the hammer hits the anvil which descends and ascentafter reflection in end of rods may be measured with an accelerometer. This signal is disturbed by stray reflections toeach new stem, natural attenuation of the signal, and so on.

5.2.2 Time

Measuring the time t is carried out

in the manual procedure, by a stop watch,

in the automatic procedure by the internal clock of the data acquisition system and corresponds to a detectiontime of a new depth step.




ISO/WD 22476-X

Key:

1 : junction box 2 : recorder

Figure 2 —Example of positioning transducers on the drilling rig

6 Specific requirements for MWD measurements

6.1 Select ion of measured parameters

Depending on the number of parameters measured while drilling, three categories of MWD measurements are defined(Table 1):

MWD A more than four parameters are measured,

MWD B where two up to four parameters are measured,

MWD C at least two parameters are measured.

The following drill rig parameters may be measured:

A: penetration length;

p: hydraulic pressure in feed motor or cylinder;

pH: hold-back pressure;

pCR: hydraulic pressure in torque motor;

PF: flushing medium pressure;

VR: drill head rotational speed;




ISO/WD 22476-X

QI: flushing medium circulation rate;

NOTE The fluid flow as well as the total drilling fluid volume for each boring should be recorded.

NOTE In case of rotary percussion, reflected vibrations ER may be measured.

NOTE Instead of penetration length A, the operator can use penetration rate V A given by the measuring system to control themachine (see 7.1).

Table 1 —Types of drill ing parameter recording system

Category Recording Examples of measured drill rigparameters

Allowable minimumaccuracy

MWD C Automaticor manual

penetration length ( A),

penetration resistance (PR)

0.2 m or 2 % of MR

1 s/0.2m

MWD B Automatic penetration length ( A),

down-thrust pressure (p),

holdback pressure (pH),

flushing medium pressure (PF)

torque pressure (pCR)

1 % of MR

2 % of MR

2 % of MR

2 l/mn

2 % of MR

MWD A automatic penetration length (A),

down-thrust pressure (p),

holdback pressure (pH),

flushing medium pressure (PF),

Drill head rotational speed (VR),

flushing medium circulation rate (QI),

torque pressure (pCR)

5 mm or 0.1 % of MR

1 % of MR

1 % of MR

1 % of MR

1 % of MR

1 l/mn

1 % of MR

6.2 Selection of equipment and procedures

The required accuracy is meant to be a function of what the results are to be used for. MWD classes have beendeveloped to give guidance on selecting type of MWD, required accuracy and logging frequency. For given soilprofiles and use of MWD results, the MWD class specifies the needed minimum accuracy and the maximum lengthbetween measurements, with an associated degree of uncertainty. The use of MWD results is stated in terms ofprofiling, material identification and definition of soil parameters.

Previous site investigation results or relevant geological and hydrogeological information shall be used if available tobe used as a reference.

MWD Classes are defined as follows:




ISO/WD 22476-X

6.2.1 MWD Class 1

MWD Class 1 is intended for precise evaluation of mixed bedded soil or rock profiles with soft to dense layers, interms of profiling and material identification. Indicative interpretation in terms of compound parameters properties ispossible, with restriction to indicative use for the soft layers.

NOTE Mixed bedded soil profiles refer to soil conditions containing typically dense and compact soils, but possibly alsoincluding soft layers.

Metrological confirmation applicable to MWD measurements shall be according to ISO 10012. Examples of calibrationprocedure are given in Annex A.

6.2.2 MWD Class 2

MWD Class 2 is intended for evaluation of hard soils and rock formation profiles in terms of profiling and materialidentification. Characterization of cavities using individual parameter is possible.

6.2.3 MWD Class 3

MWD Class 3 is intended to detect depth to boulder or rock corresponding to the level of a sharp contrast ofpenetrating resistance.

Equipment and procedures shall be selected according to the required MWD Class given in Table 2.




ISO/WD 22476-X

Table 2 —MWD Classes

MWD

Category

Maximum length

betweenmeasurements

recording

Recommended drilling tool

(see annex C of EN 22475-1) Use

type size

(mm)

Soil and rock typea

MWD classes

C200 mm

Cross bit - A to E

3

button bit - E and F

B50 mm Rock bit, Cross or

button bit> 50

C to F 2 to 3

A 25 mm

Cross or button bit 50< Do<80B

1 to 3

Rock bit, Cross orbutton bit

50< Do<80 C

Rock bit, Cross orbutton bit

50< Do<80 D

Diamond bit,

Tungsten carbide tomilledtoothed rock

bit

50< Do<80 E

Diamond bit,Tungsten carbide to

milledtoothed rockbit

50< Do<80 F

a According to EN ISO 14688-2 and EN 1997-2:

A Homogeneously bedded soils with very soft to stiff clays and silts

B Mixed bedded soils with soft to stiff clays and medium dense sands

C Mixed bedded soils with stiff clays and very dense sands

D Very stiff to hard clays and very dense coarse soils

E Weathered to soft rock

F Hard rock

6.3 Factors influencing MWD results

6.3.1 Tool inf luence

The type of tool determines the effectiveness of the chosen drilling method for the geological conditions at site.




ISO/WD 22476-X

For this reason, the type of tool shall be recorded. The same type tool shall be kept during the drilling in order tointerpret the recording.

NOTE Sampling or borehole testing may require a change of drilling tools due to the geological conditions. In this case theinterpretation of the MWD recording may be difficult. If the drilling tool is kept, the sample or test quality may suffer.

Tool wear or change shall be documented in the field report before and after MWD (see clause 8).

6.3.2 Drilling rig influence

The characteristics of the drilling rig such as its capability and its hydraulic design has an influence on the MWDresults. Care shall be taken comparing MWD results obtained by different drill rigs at the same site. Therefore thecharacteristics of the drill rig shall be reported (see clause 8).

6.3.3 Operator inf luence

The operator should be qualified according to CEN/TS ISO 22475-2 and should be familiar with MWD. A change of

operator should not affect the MWD recording. Therefore the change of driller should be avoided if a series of tests willbe interpreted together. In any other cases, the following operator shall be clearly and completely instructed. Anychange of operator shall be reported.

7 Test procedures

7.1 General

Before using a new drilling equipment or when changes of the drilling equipment have been done, a calibration drillingshould always be carried out. That calibration drilling should be performed before the start of each major project.Before performing the calibration drilling, calibration of equipment should be carried out as described in Annex A.

7.2 Posit ion and level of drilli ng machine

The distance between the test location and the location of previous investigation points should be sufficient to preventinteraction effects.

Between measuring while drilling tests, a distance of 2 m is normally sufficient. A distance from a previous borehole ofat least 20 times the borehole diameter is usually sufficient. Some borehole techniques, such as air drilling, mayrequire larger distances. Nearby excavations should be avoided.

The drilling machine shall push the drilling rods so that the axis of the pushing force is as close to vertical as possible.The deviation from the intended axis should be less than 2° or 35 mm per m. The axis of the drilling tool shallcorrespond to the loading axis at the start of the penetration.

7.3 Preparation of the measurement

The drilling machine shall be checked for suitable performance (Annex B).

Selection and preparation of an adapted flushing medium shall be made using information provided from previous siteinvestigation or relevant geological or hydrogeological data. The operator shall check that flushing channels of drillingbit and rods are open.

In a first step manual adjustment of machine parameters such as flushing pressure maximum, thrust pressure,minimum penetration rate shall be made at preset values proposed by the responsible expert or the user.

Then calibration drilling shall be carried out in homogeneous rock or soil mass with warmed-up machine in order to setthe thrust pressure, rotational speed and other drilling parameters so that the chosen leading parameter becomes a




ISO/WD 22476-X

constant value. The settings of drilling parameters from the calibration drilling shall then be kept at any subsequentsoundings.

Selecting values that are too high will negatively affect the quality of the measurements. It is important to operate thedrill rig and the associated tools well below their maximum capacity to help in conducting a successful investigation.

In addition these calibration drilling should include several ramming of the selected tool in the borehole to measure thefriction of the tool and the drill string on the borehole wall (see 9.1.5). These values of pCR0 will be used to correct thetorque.

7.4 Drilli ng procedure

To validate a drilling procedure, the drilling program planning should include a few borings for calibrating the results.During this reference drilling test, the "selected driving parameter(s)" shall fall within certain limits defined jointly by theresponsible expert and the user of the test results. This is achieved by adjusting the machine parameters and the typeand the size of the drill bit (see table 2). The holdback pressure should be set such that it can detect variationsbetween two geologic zones of different consistency.

At a minimum the results of the first drilling should be used to check the selected driving parameters.

The same drill rig, drilling tools and fluid shall be kept for the duration of each project.

In MWD Class 1, the test is started with rotation and flushing. Hammering is started when hard layer is reach andlead to too slow penetration rate. Use of air as flushing medium shall be excluded.

In MWD Class 2, the test is started with rotation and flushing. Hammering is started when hard layer is reachedand lead to too slow penetration rate. Use of liquid as flushing medium is recommended.

In MWD Class 3, hammering is always on.

If changes shall occur or tools are repaired or replaced, such information should be noted in the field report andaccounted in the interpretation of the recorded parameters. In addition the same driller should be used for the projectas each operator can greatly influence the results.

The drilling shall be terminated when one of the following events occur.

The required penetration length or penetration depth has been reached. For example a minimum of 3 m ofpenetration in solid layer is usually required;

The agreed maximum down-thrust or maximum capacity of the drill rig or measuring systems is reached;

Possible damage to the equipment can be a valid reason to end the test.

During the MWD test, particulars or deviations from this standard should be recorded, which can affect the results ofthe measurements and the corresponding penetration length.

7.5 Frequency of logging parameters

Recording shall be done based on penetration depth. The maximum step extent shall be in accordance with Table 2.Logging shall include (clock)time for MWD Classes 1 and 2 of Table 2.

The methodology for determining values recorded from the measured values shall be indicated in the operatingmanual accompanying the recorder.

The logging interval for the various measured values can also be chosen depending on the detail required in the

profile, e.g. detection of thin layers. Usually the same reading interval is used for registration of all parameters.




ISO/WD 22476-X

If the values are measured more frequently than the required reporting intervals, according to Table 2, then theaverage value calculated can be reported. Other methods however may also be applicable. The method used shall bereported.

7.6 Registration of penetration length

The level of the drilling tool shall be determined according to the requirements in Annex B, relative to the ground levelor another fixed reference system (not the thrust machine). The penetration length shall also be checked and recordedat least every 5 m for tests according to MWD Class 1 of Table 2. For other MWD Classes the penetration length shallbe checked and recorded at the end of the test. Penetration length shall be checked without using the depth sensor.

7.7 Test completion

At completion of the test, rods shall be counted when retrieved and the result compared to penetration lengthachieved.

After completion of the test and cleaning of the equipment and tools the drilling tool shall be inspected and if clogging

and any excessive wear or damage has occurred during MWD test, it shall be noted.

The reference readings of the measured parameters shall be recorded after extraction of the drill rods from the soiland, if necessary, after cleaning of the drill rig. If the zero drift of the measured parameters is larger than the allowableminimum accuracy according to the required MWD Class of Table 2, then the results should be neglected, or the testcan be put into a lower class.

NOTE The zero drift determined from zero load output before test and after cleaning is a measure of the correct functioning ofthe equipment and is used to evaluate if the requirements of table 1 can be fulfilled. The zero load outputs from the uncleaned drillrig are important for the interpretation of test results.

To identify the influence of tool wear on measured drilling parameters, it is necessary to check the status of the initialand final wear of the tool on the report (such as presented in Annex D). For this purpose, the height of the cutting

teeth, button or chisel at the beginning and end of drilling should be measured and a percentage of wear shall becalculated (Figure 3).

In case that a used drill bit is used and the wear compare to nominal dimension is higher than 50%, the tool shall bechanged or sharpened.

1 New wear = 0% 3 bit wear self-sharpening

2 weared = 100% 4 bit wear flat edge

Figure 3 — Example of bit wear for a roll ing bit




ISO/WD 22476-X

7.8 Equipment checks and calibrations

See Annex A.

7 Test results

7.9 General

The raw data shall be saved without any signal treatment: smoothing or filtering. The data output format shall be in ASCII format, often referred to as text format.

NOTE Binary format can be used in addition to vouch for the completion of drilling.

7.10 Calculated parameters

The measured raw data shall be converted to drilling parameters in MWD Classes 1 and 2.

7.10.1 Penetration rate

The penetration rate V A is obtained from the measurement of the penetration length A and the time interval dt betweenmeasures.

dt

A A tdtt −=

+

AV

V A represents an average value of the speed over the depth range considered, instant speed can be much higher andespecially in rotary percussion. The maximum speed which can be attained by the machine is Vmax.

NOTE In some automatic systems penetration rate is allowed to be considered as raw data.

7.10.2 Down-thurst pressure

Measurement of down-thrust pressure PO corresponds to the hydraulic pressure measured close to the cylinder pistonor hydraulic motor p. This measure is scaled with maximum down-thrust force Fmax evaluated during calibration withhead at lower mechanical stop and adding the rotary head weight W H and the number of rod n of unit weight WR.Reeving system shall be taken into account if added to hydraulic cylinder.

RH WnWFp

p.max

max

++=OO

.PS

NOTE For deep boreholes buoyancy applied on drill rods can be taken into account.

NOTE In some systems the down-thrust is directly measured as raw data and has the dimension of a force.

7.10.3 Net down-thrust pressure

Net down-thurst PE is a function of down-thrust and holdback, weight of drill rods and rotation head weight.

HOE PPP −=

PH is evaluated from calibration by loading the head to Hmax until movement show that holdback pressure is

overpassed.




ISO/WD 22476-X

max

max

H p

p

H

H =HO .PS

NOTE In some systems pressure differential or force transducer is used allowing direct measurement of net down thrust

pressure.

7.10.4 Flushing medium pressure

In case of aquifer, measured value PF shall be corrected with height of drilling fluid medium (density γM) present indrilling rods reduced by the height of the water table measured from the bit.The fluid pressure P I at the output ofdrilling bit (see the definition of zw in figure 2) is then calculated using:

Mwz γ .+=

FI PP

When injection rate and its pressure are measured to the water head and not on the pump or compressor (mobile andinterchangeable...) the altitude of the water head shall be taken into account.

Head losses especially affect the drilling fluid injection pressure because of the various hoses and valves. For aconventional system it may account for about 1 bar. Head losses in the drill string can be neglected.

7.10.5 Drill head rotational torque

Torque CR applied on drilling tool is proportional to the hydraulic pressure pCR the motor receives and maximum torqueCmax evaluated during the calibration process.

max

max

0R

CR

CRCR Cp

pp −=

RC

It may be useful in the case of fine measurement to measure the unladen engine rotation pressure pCRo as describedin 6.3.

For accurate measurement, measures of flow and pressure at hydraulic motor output would be needed.

NOTE In some systems differential pressure transducer are used.

In addition, manual distributors are often used to vary cylinder capacity of the engine and/or the pump thus the torqueis varied without possibility of recording. The use of such a device shall be recorded in the test report.

Hydrostatic unit with variable cylinder capacity shall not be used for drilling parameter recording test.

8 Reporting

8.1 General

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

a) summary log according to EN ISO 22475-1;

b) record of measured values and test results;

c) the information according to 8.2.

The test report shall include the following:

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




ISO/WD 22476-X

b) graphical presentation of the test results

c) the information according to 8.2.

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

In the presentation of test results the information shall be in a digital standard archive format .

8.2 General reporting of test results

8.2.1 General information Fieldreport

Testreport

Everyplot

1.a. Reference to this standard x x

1.b. Company executing the test x x

1.c. Name and signature of equipment operator executing the test x

1.d. Name and signature of field manager executing the test x

1.e. Depth to the groundwater table (if recorded) and date and time of recording x x x

1.f. Depth of predrilling or trenching depth x x x

1.g. if possible also the presence of stones or boulders, fractures or voids, noisefrom the drilling rods, the type of cuttings (colours, texture) encountered

x

1.h. Depth and possible causes of any stops in the penetration x x

1.i. Stop criteria applied, i.e. target depth, maximum down-thrust force, inclination,etc.

x x

1.j. Observations done in the test, for example, incidents, buckled rods, abnormalwear

x x

NOTE The supplied value is a parameter that depends on the signal treatment (i.e. smoothing) used by the manufacturer(unlike a numeric parameter such as pressure). It should be noted that in the case of void (e.g. karst) this value is null or maximumaccording to the system

8.2.2 Location of the test Fieldreport

Testreport

Everyplot

2.a. Identification of the test x x x

2.b. Elevation of the MWD test x x x2.c. Local or general coordinates x x

2.d. Reference system and tolerances x

2.e. Reference elevation to a known datum x x

8.2.3 Test equipment Fieldreport

Testreport

Everyplot

3.a. Drilling tool type x x x

3.b. Geometry and dimensions drilling tool, drilling rods x x x

3.c. Type of drilling machine used, thrust capacity, feed stroke x x

3.d. Manufacturer of drilling machine (recommended) x




ISO/WD 22476-X

3.e. Type of MWD data acquisition system used x

3.f. Manufacturer of MWD data acquisition system (recommended) x

3.g. Serial number of the MWD data acquisition system x

3.h. Measuring ranges of the transducers (recommended) x

3.i. Date of last calibration of sensors x

8.2.4 Test procedure Fieldreport

Testreport

Everyplot

4.a. MWD Class (Table 2) x x

4.b. Date of the test x x x

4.c. Starting time of the test (if relevant) x x

4.d. Depth of the start of penetration x x

4.e. Type of drilling fluid x x

4.f. Use of the hammer x x

4.g. Tool wear before test x

4.h. Tool wear after test x

8.2.5 Measured parameters Fieldreport

Testreport

Everyplot

5.a. Zero and / or reference readings of drilling parameters before and after the testand zero drift (in engineering units).

x x

5.b. Drilling parameters readings according to MWD Class x x

5.c. Clock time during the test x

5.d. Corrections applied during data processing x

The test reports shall include a copy of the signed MWD log, as shown in Annex E.

The graphical presentation of test results shall be uniform for a specific project and follow the recommendation of Annex D.

Further processing of the measured data can be carried out. Derivation of compound parameters from these datashall be according to Annex C, national regulations, standards or common practices.

Preliminary identification and description of the soil and rock based on the visual examination of cuttings collectedduring drilling, shall be done according to ISO 14688-1 and ISO 14689-1. This information shall be reported (withoutcorrection deduced from MWD) on a summary log using the nomenclature of ISO 710 and shall be attached to thefield report.

An example of drilling parameter report sheet is given in Annex D.




ISO/WD 22476-X

Annex A (normative)

Calibrations and field check

A.1 Calibration

A.1.1 Sensor cal ibrat ions

All the control and the measuring devices shall be periodically checked and calibrated according to the relevantstandards to show that they provide reliable and accurate measurements. If any part of the system is repaired orexchanged, calibration shall be verified.

Calibration of all sensors shall be performed at the following interval:

yearly if certifications are made by third party control (for instance manufacturer) at regular interval or

At least every six months by internal control.

Metrological confirmation and uncertainty presentation applicable to a drilling parameter recording test should beaccording to ISO 10012-1 and ENV 13005. The maximum acceptable accuracy values for each parameter are listed inTable 1. A calibration report should be generated as well as a copy of the report should be kept with the maintenancelog. A copy of the latest calibration test report shall be available at the job site.

A.1.2 Funct ional verif ication

This operation is aimed at verifying that all sensors are operating without drift and are within their calibration values.

The maximum values for the drill machine (pmax, pCRmax, CR max, , Fmax, Hmax, Qmax, Vmax,) are also determined duringthis phase.

Sensors for measuring the parameters shall be calibrated on the drilling machine used for MWD measurements.Calibration procedures are listed below for all appropriate transducers [1].

At larger deviations than the specified tolerances between the measured and registered values, the sensors constantsshould be changed in the recording device. If this cannot be performed directly, the measured values can be adjustedin connection with reporting of test results.

A.1.2.1 Penetrat ion length

A distance of 1.00 m is measured on the drill rig guide. Feeding is carried out along this distance and the time for thisis registered. This procedure is repeated with 4 different velocities, about 0.2, 0.4, 0.6 and 1.0 m/min. At the sametime the reading is noted on the recording device display.

A.1.2.2 Rotational rate

The rotation unit is set at three different velocities, for example about 5, 50 and 100 rpm. The number of revolutions isread through a tachometer. Alternatively, the number of turns during a certain time can be counted.




ISO/WD 22476-X

A.1.2.3 Down-thrust and hold back pressures

The drill head bridle is applied to a force transducer with display unit in increments of 1 kN.

If the hydraulic system of the drilling machine allows modifying the hold-back pressure, the test is started with hold

back pressure and down-thrust pressure set to zero. The hold back pressure is increased until the weight of the drillhead is counterbalanced. Then the down-thrust pressure is increased between the weight of the drill head bridle andthe weight of the drill head bridle plus 40% of the weight of the machine.

Otherwise the down-thrust pressure is increased between the weight of the drill head bridle and the weight of the drillhead bridle plus 40% of the weight of the machine.

The reading at the recording device is read at 1 kN interval and noted. One series of measurements is performed atloading and one at unloading.

A.1.2.4 Rotation hammer pressures

Calibration of the rotation pressure and hammer pressure is carried out so that the pressure transducer in thehydraulic system calibrated against a reference sensor. The reference sensor response is compared with the readingat the recording device.

A.1.2.5 Flush ing medium pressure

Calibration of flushing medium pressure transducer is performed against a reference sensor. The reference sensorresponse is compared with the reading at the recording device.

Cavity where the measurement is made has to be cleaned before calibration and flushing medium used shall be water.If a separator is used to protect the transducer from the flushing medium, it shall be de-aired (Figure B.2).

A.1.2.6 Flushing medium rate

A constant flow of water is allowed to flow through the flow meter. The outflow of fluid volume and time is measuredusing for example a reference sensor or a tank of known volume. Five different flow rates are recorded.

A.2 Field check

At the beginning and at the end of every project, the operator shall verify that all sensors are working properly. Forexample, comparison can be made between the values displayed on the recorder against the values shown on thepressure gauges, a tape measure can check the advance, a graduated reservoir can be used for the flow-meter and aspeedometer can be used for the rotation speed. The field check covers only the drilling parameters that are relevantfor the selected category.

Any malfunction or deviation from expected values should be noted on the field report.




ISO/WD 22476-X

Annex B (informative)

Positioning of sensors

B.1 General

Most often pressure transducers and flow meters should be located near the pressure or flow sources rather than atthe point where those actions are applied in part due to limited access to those locations (figure B.1). The use of quickconnectors to attach sensors to the hydraulic circuit can potentially influence the measurements if those connectorsare not fully saturated. If those connectors are used they should be positioned so as to foster the purge of air from thesensors.

B.2 Down-thrust and torque pressures

The hydraulic or pneumatic pressures sent to feed and rotation motors should be measured with a pressuretransducer placed at the input of the motor or cylinder.

B.3 Holdback pressure

Holdback pressure measurements should be made on the outflow side of the motor or cylinder rather than at the tankto avoid the inclusion of head losses in the measurements.

Key

a pressure loss created by a flow control valve

b hold back pressure created by an hydraulic pump

c hold back pressure created by a relief valve

1 pump 4 flow control valve

2 motor 5 tank

3 pressure relief valve 6 location of recommended pressure measurement

Figure B.1 — Different types of circuit used to impose the hold back pressure




ISO/WD 22476-X

NOTE According to the type of circuit used to impose the hold back pressure, the pressure measurement is more or less

accurate (Figure B.1).

B.4 Flushing medium pressure

The drilling fluid pressure PF should be measured by a pressure transducer placed close to the swivel connecting therods. Element modifying the pressure should not be placed between transducer and the swivel.

Key

1: pressure transducer

2: cavity where pressure is measured

3: membrane

4: hydraulic fluid

Figure B.2 — Example of f lushing medium pressure measure arrangement

NOTE Figure B.2 shows three examples of flushing medium pressure measurement systems with direct insertion oftransducer in the tubing or connected to a fluid filled cavity.

B.5 Flushing medium circulation rate

The inflow of drilling fluid QI should be measured close to the swivel. The element modifying the flow should not beplaced between flow meter and the swivel.

B.6 Penetration length

The penetration length should be measured by a transducer placed close to the drill rods. If a MWD Class 1 test isrequired, game between rod and transducer should be avoided.




ISO/WD 22476-X

Key

a: rotation head

b:rotary percussion head

c: rotary double head

1 recommended position

2: position subjected to game

3: game

Figure B.3 — Position o f penetration depth measurement according to head type

NOTE There are various techniques allowing this measurement: encoder mounted on feed motor axis, on chain fixed on mastcable attached to swivel, etc.

B.7 Drill head rotational speed

For the rotation speed, a sensor uses a pattern (for example bolt, teeth, paint, etc.) on the rotating head to determinethe number of revolution per minute.

NOTE A periodic repositioning of the sensor may be carried out to compensate for wear of mechanical parts.

B.8 Reflected vibrations

The accelerometer should be placed at the top of the drill rods or in the ground close to the machine.

NOTE This technique is not widely used.




ISO/WD 22476-X

6

5

4

2

7

x2 x4

3

1pHp

pCR

p

a

bc

d

e

f

g

h

i

jk

l8 9

PF

m

QI

a

b

c

d

e

f

g

h

i

j

k

l

m




ISO/WD 22476-X

Key

1 mast cylinder 4 hammer 7 hydraulic power pack

2 rotating motor 5 fluid medium pump 8 crawler

3 feed motor 6 clamps 9 stabilizer

Hydraulic symbols according to ISO 1219-1: a: motor, b: pump, c: double-acting single rod cylinder, d: tank, e: cooler,f: three ways valve, g: quick action coupling with two non-return valves, h: non-return valve, i: directly controlledpressure relief valve, j: flow control valve, adjustable, with reverse free flow, k: lever controlled 4/3 directional controlvalve, l: pressure-measuring unit (pressure gauge), m: flow meter

Figure B.4 — Example of hydrauli c schema of the drilling rig and localisation of transducers




ISO/WD 22476-X

Annex C (informative)

Application of dr ill ing parameters

C.1 The dri lling parameters interpretation

The recorded drilling parameters can be interpreted to identify transitions between soil and rock layers to improve thegeotechnical model in combination with classical site investigation and sampling.

MWD are relative parameters which seldom can be used as design parameters.

In what follows, we give interpretations usually assigned to each of these key parameters [2].

C.1.1 Penetration rate

The penetration rate V A is related to the mechanical strength of drilled formation.

Penetration rate will be even faster with the strength of the drilled formation is reduced. Study of the penetration ratemay be done through scanning in parallel torque and net down-thrust to identify effective change in the characteristicsof the ground and to dissociate of the settings of the drilling machine.

If the down-thrust is kept constant for a drilling, instant feed rate is higher in compact or dense materials and lowest inlittle compact or loose materials. This rate is linked to the equipment used (for example: drilling tool or hammercharacteristic), the hardness of the formation and its susceptibility to shocks and jetting.

C.1.2 Net down-thrust

Net down-thrust parameter gives important information on the drilling machine behaviour. They are also influenced bythe nature of geological formation drilled:

transition between hard layer to soft layer and vice versa,

penetration into rock voids and cavities,

ground material too hard or too soft for the tool.

C.1.3 Flushing medium pressure

Flushing medium pressure PI measurement gives indication on the conditions of the fluid medium circulation in theborehole. It is affected by fine particles content of the ground, that possibly make the tool gets clogged. It is anindication of the silt content of the formation and for weathered rock of the presence of fractures. The pumpestablishes in drilling a roughly stable hydraulic system and most of pressure loss occurs within the tool. When thetool passes through a plastic layer clogging tends to occur.

In the sand and clay, flushing medium pressure can be an important parameter. This pressure is essentially correlatedto hydraulic conductivity of the layer: very high in clays, it is lower in sands.




ISO/WD 22476-X

C.1.4 Torque

The torque on the tool does not have a large range of variation, low with a roller bit, larger with a drag bit; it tendsslightly to increase in clay by clogging the tool or sands with depth by increasing friction and wobble in heterogeneousground.

C.1.5 Conclusion

The quality and the definition of parameters developments will be even better if the drilling equipment has beenchosen with care and test procedure will have been established in the optimal functioning ranges of drilling equipment,drilling parameter recording system and the ground response expected.

Drilling parameters vary in soils with the texture: their particle size, their clay content, their compactness and theirmoisture content. Contrasts are also more marked for hard soils. In general, hard soils and soft or fissured rocks tendto become more resistant and fragile (in contrary a ductile clay) with the cementing and density, to a lesser extent withcohesion. Under the action of the drilling tool, a hard or coarse soil behave as a fragile material and form chips thatwill become lumps, while a cemented soil or a dense rock is dwindling.

To most geological formation a MWD parameter can be correlated to strength, but this parameter can be the same fortwo different configurations (Tables C.1 and C.2).

Table C.1 — Variation range of drilling parameters in diff erent soil s without hammering

Parameters

Soil type

penetration rate (V A) down-thrust (PE)fluid medium pressure

(PI)torque (CR)

Observations

l o w

m e a n

h i g h

l o w

m e a n

h i g h

l o w

m e a n

h i g h

l o w

m e a n

h i g h

Sludge and

soft clay,

soft clayey

soil

+++ ++ o ++ + +

linear profile

limited variation of CR

clay, stiff

clay

marl

o ++ + ++ ++ o +++ ++

Variation of V A and PE with

compacity

high values of CR and PI

indicating plugging

sandy soils

gravels,o + ++ ++ ++ o ++ + + + o


compacity and of PR with fine

content


cobbles + + + ++ + +very irregular profiles of V A, PO

et CR

weathered

and solid

rocks

+++ +++ + +

increase of V A et decrease of

PE in weathered and fractured

zone, except if very clayey


Key: +++: very significant, ++: most significant, +: significant, o: possible




ISO/WD 22476-X

Table C.2 — Variation range of drilling parameters in different soils wi th hammering

Parameters

Soil type

penetration rate (V A) down-thrust (PE)fluid medium pressure

(PI)torque (CR)

Observations

l o w

m e a n

h i g h

l o w

m e a n

h i g h

l o w

m e a n

h i g h

l o w

m e a n

h i g h

clay, stiff

clay

marl

o ++ +++ +++ ++ o +++ ++


compacity

high values of CR and PI

indicating plugging

sandy soils o + +++ +++ ++ o ++ + + + o



content


gravels, o + ++ ++ ++ o ++ + + + o



content


cobbles +++ + + ++ ++ +very irregular profiles of V A, PO

et CR

weathered

and soft

rocks

++ +++ + +

increase of V A and decrease of

PE in weathered and fractured

zone, except if very clayey


hard and

solid rocks+++ +++ + +


Key: +++: very significant, ++: most significant, +: significant, o: possible

The drilling parameters are the response of ground to the action of a drilling process. When interpreting a critical lookshould help to discern the influence of the drilling machine (drilling tool, drill rods and rotation head and operator) thatcan be differentiated.

The analysis of these parameters allows an initial interpretation, but it is not sufficient to interpret the signal-log.Complementary methods are proposed below.

C.2 Compound parameters

Compound parameters combine individual parameters into expressions of energy or empirical indices reflecting theresistance of the geological material to drilling. They have been introduced as a means to partially take into accountthe effect of drilling method as well as take into consideration the inherent variability.

C.2.1 Penetration resistance

The penetration resistance is the time measured in seconds for 0,2 m of penetration [1].

mzR tP 2,0)(=

= (C.1)

The purpose of the penetration resistance parameter is to clarify the depth to the rock, the relative firmness of the rockand fracturing.




ISO/WD 22476-X

A similar relationship is used for another compound parameter called soil-rock resistance:

A

ESR

V

PR = (C.2)

The use of this parameter is recommended when down-thrust is measured. The use of hammering should be reportedas proposed in Annex D.

C.2.2 Alteration index

Correlations based on advance rate, down-thrust on the drilling tool and the relative density of unconsolidatedmaterials or alteration index I A in rocks can be used as follows.

−+=

max

1

max

0 ..1

V

V k

P

Pk I

A E

A (C.3)

where

Pmax is the maximum weight on the bit measured in the field,

Vmax is maximum theoretical penetration rate measured in the field as a means to contrast with the actualpenetration rate,

ko and k1 are empirical parameter fit on calibration test drilling results.

This relationship is well suited for rocky soils and used to qualify rippability of the formation tested.

C.2.3 Somerton Index

Somerton index Sd depicts the resistance to drilling in rock. This relationship has been developed based onexperimental results obtained in the laboratory [3]:

2

2.

..5,1

=

DS

P DV V

d

E R A (C.4)

For a given site and for each geologic formation, it is possible to calibrate specific relationships with geotechnicalparameters such as the SPT blow count and Menard limit pressure p l using the relation (C.5):

21

.

≈

A

R E d

V V PS (C.5)

For geotechnical drilling rigs, although the rotation speed is not often recorded, the driller has a tendency to keep itconstant during the advance. Consequently, the Somerton index can be simplified to:

A

E

d

V

PS ≈ (C.6)

An example of results is compared with the Menard limit pressure on Figure C.1.Note that it is only valid for a specificsite and soil.




ISO/WD 22476-X

Y

X

Po Pi

Cr VA

Y

X

1 2 3

Sandy clay with

gravels

gravel with clayey

matrix

=

Clay slightly

sandy

Key

1 Menard limit pressure

2 Somerton index Sd

3 Soil-rock resistance RSR

X calculated drilling parameter or compound parameter

Y depth

Figure D.1 — Comparison of Somerton index, soil-rock resistance profiles versus st ratigraphy

C.2.4 Energy

Estimation of energy used to drill a hole for a specific tool can be obtained using the equation (C.7) [4]:

A

MRR AE

V

f pVCVPE

....2.... γ π β α ++

= (C.7)

where

α, β, γ is the efficiency coefficient of drilling which need to be estimated.




ISO/WD 22476-X

For shallow boreholes a specific energy compound parameter simplification of drilling energy can be used whichcombines energy and drilling depth [5,6]:

A

RRES

V

VCPE ..+≈ (C.8)

The term PE is often neglected which reduces to using work produced by the rotation torque CR. The torque energy,per unit of penetration results in:

A

RR

RV

VCE

.= (C.9)

The torque energy is useful in differentiating variations in ground hardness, however, only the alteration index allows agreater classification of softer materials in spite of the variation being only from 0 to 2.

Y

X

Po Pi

Cr VA

Sandy clay with

gravel

Rounded gravel

with clayey matrix

Clay slightly

sandy grains




ISO/WD 22476-X

Y

X

1 2

Key

1 Specific energy ES

2 Alteration index I A

X calculated drilling parameter or compound parameter

Y depth

Figure C2 — Example of specific energy and alteration index profi les

These parameters when used in non-cemented materials allow the identification of layers of varying consistencies

(Figure C.2)

C.2.5 Computerized interpretation

The statistical study applied to drilling parameters has for objective to determine characteristics defining ahomogeneous zone for the purpose of computerized interpretation of profiles. It has to be considered that drilling is asystem dependent on various control variables which are not always measured (wear, speed of rotation, etc.).

The applied techniques are either based on simple variables (mean, median, standard deviation, asymmetry,flattening, etc.) or developed for specific variables: index of homogeneity or on the variogram or the autocorrelationanalysis.

These techniques require significant local experience to assess their relevance in the application. These are not

covered by this standard.




ISO/WD 22476-X




ISO/WD 22476-X

Annex D (informative)

Graphical presentation of drilling parameter

An example of drilling parameter report with the information needed for presenting the results is given in Figure D.1.

D.1 Choice of axis scaling

The graphical presentation of test results shall use the same axis scale.

A different scaling may be used in addition for detailed study.

NOTE A common presentation format is to use linear scales.

D.2 Presentation of test results

The test results shall be presented as continuous profiles as a function of the penetration depth and penetration length.The test results that have to be presented are:

according to the MWD Class 1

Penetration rate –depth/length V A (m/h) – z (m)

Net down-thrust –depth/length PE (MPa) – z (m)




Flushing Medium pressure –depth/length PI (MPa) – z (m)

Flushing Medium flow –depth/length QI (l/mn) – z (m)

Drill head rotational speed –depth/length VR (r/mn) – z (m)

Drill head rotational torque–depth/length CR (N.m) – z (m)




Flushing Medium pressure –depth/length PI ( MPa) – z (m)

Units in kPa can be used depending on scale of measured parameters.




ISO/WD 22476-X

Presentation of the results of MWD tests according to MWD Classes 1 and 2 shall, if required, include at least tabulardata according to 8.1.




ISO/WD 22476-X

Drilling Parameter Recording

according to EN/ISO 22476-X

Project N° :_______

Date :___/___/___

Name of the client: ___________

Project:____________

Location: _____________

Identification of the borehole: _____

Machine

Marque: _______

Model: _______

Serial N°: ______

tool : ____________

wear before drilling :

0-20-40-60-80-100 %

wear after drilling:

0-20-40-60-80-100 %

rods :_______

diameter :____

weight :_______

length : _______

Flushing medium

air

mud :_____

foam

Position (precision)

X :________(___) m

Y:________ (___) m

Z:________m NGF

depth / time

from :_____ / ___h____

to :_____ / ____h____

Inclination :

Drilling method :

rotation

rotarypercussion

Recorder

Manufacturer:

Model:

Serial N°:

a l t . ( m )

d e p t h ( m )

Information on

the ground strata

d r i l l i n g

VA PO PH PI CR

Desc.

C l a s s . unit unit unit unit unit

101-

100-

99-

98-

97-

96-

95-

94-

0-

1-

2-

3-

4-

5-

6-

7-

r o c k b i t

Sa

Cl

Calc.

h a m m e r i n g

Cl

Name of datafile: ________________________

Acquisition frequency: _________________ or measuring step: _________________

Date of last calibration of sensors: ___/___/___ Date of last checking of sensors : ___/___/___R

Remarks (interruptions, obstructions, difficulties, etc.):

Reason for drilling termination: ________________________

Name of the compagny Address Tel : Fax : Name of the qualified

Operator : _____________

Supervisor : ____________

signature :

Figure D1 —Example of field repor t of Drilling Parameter Recording




ISO/WD 22476-X




ISO/WD 22476-X

Bibliography

[1] Svenska Geotekniska Föreningen (1999): Metodbeskrivning för jord-bergsondering, SGF Rapport 2.99, 30 p.

[2] Laboratoire Central des Ponts et Chaussées (2010): Paramètres de forages en géotechnique, Méthoded'essais des laboratoires des Ponts et Chaussées N°79, 54 p.

[3] Somerton,W.H. (1959): A Laboratory Study of Rock Breakage by Rotary Drilling. Journal of PetroleumTechnology.Vol. 216: 92–97.

[4] Nishi, K., Suzuki, Y. & Sasao, H. (1998): Estimation of soil resistance using rotary percussion drill. Internationalconference on site characterization, Proceedings ICS98, Atlanta, vol.1: 393-398.

[5] Pfister, P. (1985): Recording Drilling Parameters in Ground Engineering. Journal of Ground Engineering. Vol.18 (No. 3): 16–21.

[6] Teale, R. (1964): The Concept of Specific Energy in Rock Drilling. International Journal of Rock Mechanics,Mining Science. Vol. 2: 57–73.

ISO en 22476 15 MeasuringWhilstDrilling

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