Recording drilling pararI~etersin ground engineeringby PAUL PFISTER"

GeneralSEVERAL SOIL improvement methodsrequire the drilling of a large number ofholes; this is the case for soil or rockgrouting, as well as ground freezing.Uncored holes are usually drilled inconnection with these methods. Over thepast years, the contractor's concern hasalways been to optimise drilling methods inorder to increase the drill's output, tominimise drilling hazards, and to reducecosts. This concern has led to an extremelylarge variety of drilling techniques, tools andtypes of drilling machines.

However, at the same time, the need for abetter knowledge of the soil or rock mediumhas not decreased and the precise monitor-ing of a soil improvement process is stilldependent mainly on the accuracy of the pre-liminary investigations. There are very fewmeans available, in the hands of theengineer, to qualify the work done, except bytesting the treated medium when the work isfully, or at least partly, completed. In fact it isdifficult to take the art out of foundationgrouting and not to rely on the contractor'sassumed skill. It is just as difficult for thecontractor himself to demonstrate itscompetence and to defend the suggestionshe may have to formulate in the course of theworks.

The design of large projects such as dams,metro lines, railways, tunnels, pipelines, etc.requires a large number of holes to be drilledin order to come to a good, though usuallysomewhat simplified, image of thefoundation soil. The holes are mainly coredones, but the soil investigations also requirethe drilling of holes for all kinds of in-situtests (SPT, pressuremeter, cone penetrationtesting, cross-hole seismic measurements,etc.). The trend is for the designers toincrease the variety, the sophistication andthe number of the investigation techniques,and of the investigation points. It is counter-balanced by a need to control the costs andto prevent excessive amounts of moneybeing spent at the earliest stages of theproject.

The two preceding observations were atthe origin of the development of the drillingparameters recorder which started in theearly seventies. The idea was:(ij to make use of all the holes which had to

be drilled in connection with soilimprovement techniques in order todetect and to record the main soilfeatures, and

fiick to reduce the cost of soil studies for largeprojects by using a quick extrapolationmeans which could be calibrated on alimited number of cored boreholes and

Engineering Director, Soletanche Entreprise, Nanterre,France,

Fig. 1. Four-channel analogue recorder

which would give a continuous image ofthe ground whatever the type of soil orrock and the investigated depth.

While the oil people were used to watchingthe main drilling parameters constantly, andto monitoring them for mastering the safetyand efficiency of the drilling operations, thiswas not the current practice in civilengineering. In fact, when recorders (whichwere purely graphical plotters, and veryinaccurate ones at civil engineering level)were used in the oil industry, the purpose ofthe recording was not related to thedescription of the ground but was intendedto help in future rig operations. Soilengineers —and even more civil engineeringdrillers —were, on their side, very aware ofthe value of the information the drill itself wasable to give on the soil nature, heterogeneity,and state by mere observation of the way it

was reacting. The first drilling parametersrecorders attempted to translate the driller'sfeeling into printed evidence.

Analogue drillingparameters recorders

Several authors have described the A.D.P.(Analogue Drilling Parameters) recorders.There are several types which allow thegraphical recording on paper of one to fiveparameters measured on a drill carrying outfast destructive drilling. Fig. 1 is a picture of afour channel recorder which can be used onrotary drills. Others are designed forpercussive or rotary-percussive drills. All ofthem are relatively easily adapted to the drilland do not significantly reduce drill output.

The recorded parameters are:—drilling penetration rate (a special device is

used to neutralise movements not actuallyrelated to actual drilling),

—thrust applied to the drilling bit (what isactually measured is the oil pressure in therams),

—drilling fluid outflow pressure (usuallymeasured at ground level),

—rotation torque applied to the string ofrods by the head (the oil pressure in thehead is measured), and

—reflected percussion wave for rotary-percussive drilling (an accelerometer isplaced on the head).With the A.D.P. recorder connected to the

drill (Fig. 2), and the bit sited at ground level,the first operation is to select the scales forthe plotting; these include the depth scale(for instance 1cm or 2cm per metre depth),and the maximum expected value for theparameters to be recorded (for instance400m/hour or 1 200m/hour for thepenetration rate depending on the soilstrength or on the possibility of encounteringcavities, etc...).The selection requires someexperience and it is not recommended tochange scales during the drilling or to usevarious scales on comparable holes on thesame site, as the interpretation of the graphsis much easier when direct comparisons canbe made between the graphs. Once the scaleselection has been made, drilling can thenproceed and it is carried out as usual, exceptthat it is recommended that the driller workat constant thrust as much as possible. It isalso good practice for him to take a note of alldrilling incidents such as fluid losses,changes in colour of cuttings, breakdowns orstops.

When the hole is drilled, a continuous plotis available, such as the one in Fig. 3, which isan extract of the plot of a 76m hole drilled onan Algerian dam site. Stiff mudstones extend

Fig. 2. Analogue recorder on hydraulic rotarydrill

16 Ground Engineering

up to a depth of approximately 64.6m andthey are overlying a sandstone bedrock.

Interpretation of A.D.P. plotsA.D.P. records are normally taken in

connection with destructive, continuousholes, drilled using a destructive tool such asa tricone or drag bit. When the toolencounters a different layer of soil or rock,the intensity of one or several parameterschanges. The interpretation of the plots isbased on the careful study of the

parameters'ariations

with depth.One learns from experience that in a given

type of soil or rock, the variations of one ofthe recorded parameters are predominant.However, though this is of great help in theinterpretation, it may happen that twodifferent soils in fact have the same dominantparameter; this is the case for clay andmudstone, for instance. It is thereforeessential to base the interpretation on asound knowledge of the site geology. Therecommended method is to calibrate alimited number of A.D.P. records on coredboreholes drilled within a short horizontaldistance of the destructive holes. It is theneasy to extrapolate the interpretation to awhole site on the sole basis of A.D.P. records.The interpretation will be completed by thestudy of the variations of the otherparameters which depend on stiffness, grainsize changes, and other factors. Underparticularly favourable conditions, it ispossible to come to a satisfactory soildescription with a precision of less than0.10m on the depth or thickness of a layer.

Fig. 4 is a demonstration of the typicalfeatures of the recorded shapes of curves fora given site ICruas nuclear power plant site in

France). On that site, a preliminary siteinvestigation, mainly based on gravimetricmethods, had shown the existence of weakspots in the limestone stratum, underlyingthe recent sand and gravel alluvial deposits.Four nuclear reactors were to be founded inthe limestone. A total of 3 580m of A.D.P.destructive holes were drilled up to a depth of15-25m. They detected empty cavities,fissured or fractured masses and the clayeyfilling in them, and massive plain limestone inother areas. It is interesting to note that:(iJ the A.D.P. survey gave evidence of

anomalies in the limestone stratum thatcould not be shown by cored holes and

(iij confirmed in a much more accuratefashion the results of the gravimetricstudies.

Generally speaking, the use of A.D.P.recordings has proved to be very effective inthe characterisation of:—rock as opposed to soil, state of rock,

localisation of cavities and filling materialin them,

—cohesive soils such as clays, claystonesand mudstones,

—non-cohesive soils as opposed to cohesiveones, and qualification of the grain-size:sands, sand and gravels, cobbles,

—boulders in heterogeneous soils such asscree, moraine or torrential alluvium, and

—groutable layers from non-groutable ones,which allows considerable time, cost andeffort to be saved.

Computerised drillingparameters recorders

Graphical analogue print-outs have someshortcomings which create limitations to theuse of the method:

Penetrationrate

Thrust

0

F

200m/h 0 125 bars

Torque

0 125bars

41I~ IRF

:~ E~ s%is4 I I 8'

I:

J

I

i~wE

Mudpressure

0 20 bars.5$Pb

IR

~.~ kp as

~ I.ssm

i

I

)CI

)

70m

r

II

)I 75m

only one print-out is available per record,with consequent difficulties in makinggood copies, changing the scales for thesake of comparison with other types oflogs, report presentation, ease of use.site scale selection can be inadequate,which may either lead to a loss ofinformation in some zones which later on

Fig. 3. Typical 4-channel analogue drillingparameters recorder print-out

Mud pressure

I0 nb 0

Torque Thrust on bit

I I1255 0 125b 0

e

Penetrationrate

I400m/h

Mud pressure Torque

I0 10b 0

I

)

)

Thrust on bit iPenetration

I rateI I I

125b 0 250b 0 800m/h

)

I

10 0

SILTY SURFACE DEPOSITS

125 0 125 0 400

CLAY LAYERS

1250 10 0

c

~

I

I

250 0 800

ALLUVIUM ISAND, GRAVEL, COBBLES) EMPTY CAVITY

250 0 800 0 10 0 125 0 250 0 800

UNFILLED FRACTURE PLAIN MASSIVE LIMESTONE

125 800

FRACTURED ZONE FILLED WITH CLAY

Fig. 4. Typicalinterpretation of AOP print-outs for the Cruas site

April 1985 17

Fig. 5 (upperj. Front view of Enpasol recorderwith cassette slot and control panel.(lowerj. Back view ofEnpasol recorder with 4-channel graph plotter

prove to be essential for the particularproblem under study, or, when the scaleshave been modified by the driller duringthe drilling operations, difficulty incorrelating the results with other ones.

—reading difficulties when the print-out isdamaged on site due to difficult weatherconditions,

—difficulty in accurately calibrating theresults as a function of other, moreclassical soil parameters, such aspressuremeter results or shearparameters,

—impossibility of combining recordedparameters values into combineddimensionless parameters or others.In fact, these limitations restrict the use of

A.D.P. print-outs to specialists and toqualitative interpretations and conclusions.

Soletanche therefore set out to design adigital computerised recorder which wouldimprove on existing analogue devices andrecord up to eight separate parameters onmagnetic tape cassettes, very accurately —infact with a resolution of 0.5cm (Figs. 5 and6).

Supplementary computer software wasthen developed, based on experiencegathered from the analogue recorders andfrom the first extensive use of the digitalrecorder on a few sites. The software iscontinually improved and currently allowsone to read, process and interpret the datarecorded in digital (numerical) form and tocorrelate this with:—the type of soil and rock,—the properties of the medium (fissuration,

grain size, permeability, othergeotechnical parameters),

—the modifications produced by grouting orany other soil improvement techniquesuch as dynamic compaction or freezing.Micro-computers with a minimum

250Kbytes and a built-in thermal printer arecurrently employed to analyse and to plot theinterpreted results of the processed data(Fig. 7). They are very convenient for use onsite as well as in the office but other typescould be employed, subject to an adequaterewriting of the programmes in the propercomputer language.

The Enpasol computerised recorder deviceis composed of three main parts housed in asingle box attached to the drilling rig:—a graphical plotter which plots the

variations of the four parameters selectedby the operator (from the eight available tohim from the Enpasol), while the drillingproceeds,

—a micro-computer which monitors thedata from the eight parameters and storesthem on a cassette,

—an electronic control box which convertsthe analogue signals into numerical dataand transfers them to the micro-computer.The Enpasol can also be used without

cassettes as a standard analogue four-channel recorder.

The eight parameters that can be recordedsimultaneously are the same as those listedin the previous section on analogue devices,plus three others which have proved to bevery important for the interpretation of theresults:—rotation speed of the drilling rods and bit

(measured on the rotation head),—retention force (counter pressure of the

hydraulic pull-down rams) which has to bededucted from the thrust applied to cometo an actual evaluation of the weight on thebit. The weight of the rods and bit can alsobe taken into account when interpretingthe results, if it is significant, and

—time interval between consecutive datarecords, i.e. time required for drilling eachSmm (0.2in) penetration interval.The soil-reflected percussion wave is

detected (when the drilling is carried outusing vibro-percussive methods) and it isquantified by recording the parameterVibrasol(patented process).

The parameters are recorded, with highestprecision, without any interpolation oraveraging, at a rate of 12 000 measurementsper second on eight channels. One cassette

Fig. 7. Microcomputer processing of Enpasoldatacan be used for a total drilled length of 100m(330ft) or more if the choice has been madeto record less than the maximum number ofparameters.

First level of interpretationof Enpasol data

The first step in interpreting the results (aswell as the immediate information obtainedduring the drilling by the print-out of the fourselected parameters) consists, after a simplegraph of the variations in the recordedparameters with depth has been drawn andprinted out by the computer, in making achoice of the best image of the soil that canbe obtained relative to the problem in

question. Actually, the simple fact of workingon numerical data opens up a large numberof possibilities:—adjusting the scales (depth, and amplitude

of variations of all the parameters),—selecting one or a few parameters instead

of the whole set for the print-out,—combining the parameters in order to draw

other parameters of greater significance orsimply more contrasted (referred tobelow),

—smoothing the curves by averaging thevalues,

—calculating means or making all sorts ofstatistical analyses.

Fig. 6. Enpasol recorder mounted on (leftj vi bropercussi ve drill and (ri ghtj rotary hydraulic drill

18 Ground Engineering

As for the A.D.P. results, the simplestinterpretations are made on the basis of thevisual study of the shape and variations of thegraphs. In simple cases, the automaticdrawing of a geological log is alreadypossible from a decision table specificallyestablished for the case under study (see thefirst example of interpretation, Fig. 8).

This first level of interpretation allows onein many cases to complement very quicklyand economically a large soil investigationbased on a small number of cored holes (adam site for instance).

As previously mentioned, datadigitalisation is very convenient for combinedparameters calculations. The combinationsused up to now are either purely empirical ormay have a physical meaning. Those we areusing mainly are described hereafter.

PIV

5 Qo

RLLIJC Ecll6

I.IC tt Crttc 6

RLLUC I t lc

Rtatr I Et ltt66

RLLU" Z: ttc

RIJC ECRIICC

Energy used for drillingThe energy parameter is calculated from

the formula:

W=Cxu/Vor W=CxuxDtin which C is the value of the rotation torque

s> is the rotation speedV is the instantaneous penetration

rate, andD,is the time needed to drill a soil

layer of Smm thicknessThe "energy" parameter has proved very

useful in the analysis of hard soils and of rockmedia.

:RL:RXREEIE 6 t, CIJEt,

tcERL:*EttE

EtC Ce-::u«t,

RL rfRK

DE 6+-.IJEt

Alteration indexThe alteration index is calculated by:

A = 1 + P/P, —V/V,

in which P is the weight on the bit (thrust—retention force + weight of rodsand bit)

P, is the theoretical maximum valueof P

V is the instantaneous penetrationrate (with maximum value V,).

The "alteration index" varies from 0 in thesofter soils to 2 in the harder ones on a givensite. It is very sensitive in medium to lowstrength soils. Pig. 8. Automatic printing of geological strata

7'J

denominations by the computer

:RL:RERE

EIE 66 —CIJEt

6RPLE 6 5%

CCRU II Rt.tr

Somerton IndexThe Sd index was drawn from a laboratory

study of rock breakage by rotary drillingreported by Somerton.

Sd = R/u/V

P, u, and Vhave the same meaning as above.Research is being done on the correlations

which could be found between thepreceeding "combined" parameters and theusual soil parameters. However, suchparameters already allow the method to beused for quantifying the results in a mannersimilar to other in-situ tests such as SPTs,cone penetration tests, etc. Moreover, thepossibility of statistically analysing thecombined parameters produces anadditional element.

1st example of interpretation:automatic geological logging

This deals with a site, in the Paris area,where the geological strata are well knownand relatively easy to identify. The Enpasolwas used, on a grouting test plot to arrive atan accurate assessment of the soil volume,i.e. of the thickness and depth changes of themain strata. Six parameters were recorded:mud pressure, torque, thrust, retention force,drilling rate, rotation speed.

After some trials, the final representationof the results which is illustrated in Fig. 8 was

selected. Two "combined" parameters areused: the first one (left hand side column) isequal to the square of the mud pressure; thesecond is P/V, i.e.the ratio of the thrust on thebit to the drilling rate. They are alsorepresented in a simplified form in columns 3and 4 in order to increase the legibility of thegraphs.

The first layer is characterised by low P'sand almost null P/Vvalues: it corresponds tovery soft clayey sands (recent alluvium, or"Alluvions Modernes" in French). The secondlayer is very pervious: P'alues are almostequal to zero, but the strength and P/Vincrease. It is composed of ancient sand andgravel alluvium. Then comes the Calcaires deSt-Ouen formation, which is composed ofsuccessive beds of limestone and marls.

The contrast on the curves was so goodthat it was possible to have the computerdirectly write the geological log in clear onthe right-hand side column of the print-out.Simple tables of decisions were fed into theprogram of interpretation of the data to makethis automatic logging possible.

2nd example of interpretation: claylayer in a sandy mass

Fig. 9 illustrates the evidence of clay stratain sandy soils. The abrupt increase in mudpressure, decrease in torque value andincrease in drilling rate necessitates no

additional data processing to illustrate thepresence of a clay layer and to locate it veryprecisely.

It is interesting to note the excellentcorrelation which was found with a staticcone penetrometer diagram correspondingto a very close point of investigation.

3rd example: destructive checks ofpiers concrete

Large piers of short depth used for a bridgefoundation were checked by drilling a fewholes with a down-the-hole hammer into theconcrete. Fig. 10 is an example of asatisfactory pier and of a discontinuous onewhich is also resting on remoulded soil. The"concrete" parameter is obtained by anextreme smoothing of a parameter definedas:

C= (P R)~Dc

where (P~J is the weight on the bit,D, is the time interval.

4th example: use of a recorder on adrain placing machine

Fig. 11 is a sample of the results obtainedfrom a plastic drain placing machine onwhich an Enpasol recorder was placed. Thelocation of the sand seams in the soft clayinto which the drains were being pushedcould be pointed out with an excellent

April 1985 19

PressureDer

5

Enpaeol

TorqueDer

10

CPT

Prtotton AetioDna rate

in/5 rrqe in 55

,. sr

C. c'

~ tar

1I

Fig. 9. Clay layerin a sandy mass. Comparisonbetween Enpasol record and CPT diagram

precision. Thrust, penetration rate, and time,were recorded. The interpretation was madeon the basis of the "alteration" combinedparameter which is labelled as (P—Vj on theprint-out.

From the diagrams, a complete descriptionof the drained volume was made and preciseevaluations of consolidation times could bederived.

5th example: use of Vibrasol on an air-powered drill

Fig. 12 relates to a hole drilled in rock witha vibro-percussive air-powered drill.

The variations of the IVibrasoln parameterare directly related to the strength andsoundness of the rock (very sound rockbetween 4.50m and 6m).

I05

D II at

ia0 02

Tn I

II

I05

D il

I ma0 02

Fig. 10 (upper/. Continuous satisfactoryconcrete pier.(Lower/. Discontinuous concrete shaft andremoulded base

Second level ofinterpretation of Enpasol data

The Enpasol data can be used not only toidentify the soil strata or nature but can bethe basic element for the design, guidanceand control of a soil treatment, especiallywhen the technique used involves the drillingof a large number of destructive holes.

This may be illustrated citing the exampleof the grouting at the nuclear power plant ofCivaux.

A grouting test section was executed forElectricitti de France (National FrenchElectricity Board) from July 1982 to January1983, on the site selected for the proposedCivaux nuclear power plant. The test was runto select a grouting method and to find aquality control method for the grouting. Onthe Civaux site, the ground is composed of aJurassic limestone, overlain by a few metresof alluvial deposits which would be exca-vated prior to the erection of the plant. Thebedrock has been affected, in geologicaltimes, by karstic erosion and, most probably,by seismic events which were responsible forlarge faults. The limestone rock is completelybroken up into variable size pieces as a con-sequence of the earthquakes having affectedzones which were previously subjected tointense weathering and karstic erosion.

It soon appeared on the site at the time ofthe first soil investigation that it was verydifficult to characterise the limestonemedium due to the extreme variationsobserved in the in-situ tests results, theimpossibility of running representativelaboratory results, the difficulties in coringand classifying the broken limestone, and theabsence of any satisfactory method for thefuture quality control of the grouting. Thepressuremeter tests, for instance, were

Thrust Drill rate Time

bar m/s sec50 0.05 0.05

P-V P—V

0.5 0.5

10

15

20

25

353

Fig. 1 1. Interpretation of Enpasol datameasured on a drain-placing machine (sandlayerin soft clay)

Thrust

bar2.5

Drill rate

m/s0.025

Vibrasol

Fig. 12. Vibrasol parameter in rock (vibro-percussive drillingj

indicating moduli between 1.5MN/m'nd1 OOOMN/m', and limit pressures weresometimes as low as 0.75MN/m'n thevirgin medium.

The Enpasol proved to be the tool whichcould help to solve the whole problem at avery reduced additional cost, and its use wasextensive in the grouting test plotprogramme.

The holes for the grouting were bored withdrills equipped with an Enpasol recorder. Thedata were interpreted in terms of parametersW = Cto/V and A, as defined previously. Itsoon appeared on the basis of a close cali-bration on two large diameter, very carefullycored holes, that a classification could beestablished on the basis of the values of Wand of the mud pressure into six categories,labelled CO to CS as shown on Table I.

Fig. 13 is a sample of the plots which weredrawn on site by the micro-computer: theright-hand side column of the graph is theresult of the detailed automatic analysis ofthe state of the rock, at the hole location,which was automatically printed. Later on,the distinction between CO and C1 on the onehand, and C2 and C3, on the other hand, wasabandoned, and only four types of rock, CO,C2, C4, C5, were taken into consideration.

The purpose of the grouting was to reduceto a minimum the presence of unconsoli-dated spots and to improve the overallstrength of the rock mass. After the firstphase grouting operations through theprimary holes (4m apart) were completed,secondary holes were drilled in between theprimary ones. The Enpasol was used againand it showed a very significant improvementof the W values as compared to the virginstate. After completion of secondarygrouting, some holes were again drilled forthe sole purpose of quality control.

The computer could analyse all the datafrom the three series of holes and Table II is asummary of the results obtained. The values

20 Ground Engineering

p-v cIuv Alteration HardnessI 10 200 400 20 25 200 400

CI

CI

CI

ZZCc

CI'I

01 02 03

40

Q4-cc

CI

I

I

I

CI

c.

CI

CI

00

IF-:

RCO

I

I

Fig. 13. Typical plot of combined parametersand mck classification at Civaux

TABLE I

Type

CO

C1C2C3C4C5

TABLE II

Description

Totally unconsolidated rockSame as C1, filled with clayLimestone broken into small fragmentsSame as C1, voids filled with soft materialLimestone broken into large chunksMassive limestone

Parameter W

less than 10

10 to 100

100 to 250larger than 250

Mud Pressure

lowhighlowhigh

Depths

9-14m

State of mck CO

VirginPrimary groutingSecond. grouting

2.1%00

Type of limestone detected l()6jC2 C4 C5

55.3%37.31 5.1

42.60/o

62.781.9

0%0

3.0

14-20m

20-36m

36-42m

VirginPrimary groutingSecond. grouting

VirginPrimary groutingSecond. grouting

VirginPnmary groutingSecond. grouting

1.7%00

8.1%00.7

14.3%3.74.0

30.0%46.81 9.4

53.00/o33.925.5

39.8%41.21 5.2

68.3%51.372.3

37.6%53.459.2

38.3%45.158.5

0%1.98.3

1.3%1 2.714.6

7.6%10.022.3

appearing in the CO to CS columns arearithmetic means of the values drawn fromthree series of holes (primary, secondary andcontrol holes) located in the test plot. Theyshow and quantify the degree of improve-ment of the rock by the two stages ofgrouting which were run successively.

Because of the random distribution and ofthe geological hazards in the limestone, theonly valid checks had to be statistical ones. In

view of arriving at a criterion for satisfactorygrouting for the future extensive groutingprogramme, the distribution laws of W forspecified depth intervals were automaticallycomputed and drawn in the form shown onFig. 14. From a compilation of such curves acriterion was proposed, which is representedon Fig. 15; all distribution curves would haveto be in the A area to be considered assatisfactory, while those falling into the 0area would be considered as unsatisfactoryand result in a regrouting of the correspond-ing depth interval.

An interesting point from such a criterion isthat it would also allow a check of the virginstate of the rock. In some areas, the virgincurves would probably show a satisfactoryshape even before any grouting. The conse-quence would be an economy on the grout-ing, since it would be meaningless to groutthose volumes where good conditions werenaturally prevailing.

The Enpasol data was also used on theCivaux site to monitor the grouting process.On the basis of the takes observed in the firstholes, and of the correlations made with the

i. @Xiii IPPliii

0 10 50 100 180 200 300

Fig. 15.Proposedcriteribn forsatisfactory rockgrouting at Civaux

rock classification previously described, thegrouting programmes were then automatic-ally printed for each hole of the test plot ondetailed forms which included the amount ofgrout to inject per sleeve determined exactlyfrom the Enpasol data.

Conclusion andfuture developments

The use of drilling parameters recordersstarted a new way of investigating soilproperties as well as of monitoring andchecking the success of soil improvementtechniques. The introduction of digitalrecorders has widened the possibilities of themethod to a stage where design itself shouldbe influenced by the availability of suchpowerful tools. Wide developments of therecorders as well as of similar devices and ofrelated design methods can be expected totake place in the coming years.

References and bibliographySomerton, W.H. (1 959):"A laboratory study of rockbreakage by rotary drilling." Journal of PetroleumTechnology, Vol. 216, May

Gardes, P. (1977): "Reconnaissance des terrainsgrace 0( I'enregistrement continu des paramatresde forage." Annales I.T.B.T.P., serie Sols etFondations No. 146Mouxau2c J. (1978):"Boring device for recordingsoil data." International Tunnel Symposium,Tokyo —Tunnelling under difficult conditionsPfister, P. (1980): Interpretation desenregistrements de paramstres de forage" Bulletinof the International Association of EngineeringGeology No. 21Hamelin, JP., Levallois, J. & Pfister, P. (1983):"Enregistrement des paramstres de forage:Nouveaux developpements" Bulletin of theInternational Association of Engineering GeologyNo. 26-26, Paris

Jendoubi, F., Girard, H. Er Morlier, P. (1984):"Contr()le de'injection par diagraphiesinstantant(es" Proceedings of Ninth InternationalFormation Evaluation Symposium, Paris, Oct. (inpress).

100%

'l

Ol!O

c4Iu4Ia 50%Ol

!O

E

O

Hole 33Virgin soil20 to 36m

100% '(CI

Ol0(Ol

cOlu

a 50%IO

!0

EC2

Hole 51After first phase

of grouting20 to 36m

OlOlIO

0Ol

a 50/oOl

E

100%'C

2

'%CC~

Hole 211After second phase

of grout(ng20 to 36m

C(»l V CIIll V

10 50 100 10 100 250 10CO C2 CO C2 c4 CO

Fig. 14. Distribution laws of C02/((/on adjacent holes before and after rock grouting

100C2 c4

April 1985 21