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Designation: D 3441 – 98 AMERICAN SOCIETY FOR TESTING AND MATERIALS 100 Barr Harbor Dr., West Conshohocken, PA 19428 Reprinted from the Annual Book of ASTM Standards. Copyright ASTM Standard Test Method for Mechanical Cone Penetration Tests of Soil1
  Designation: D 3441 – 98 Standard Test Method for Mechanical Cone Penetration Tests of Soil 1 This standard is issued under the fixed designation D 3441; the number immediately following the designation indicates the year of srcinal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon ( e ) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1. Scope 1.1 This test method covers the determination of end bear-ing and side friction, the components of penetration resistancethat are developed during the steady slow penetration of apointed rod into soil. This test method is sometimes referred toas the Dutch Cone Test or Cone Penetration Test and is oftenabbreviated as CPT.1.2 This test method includes the use of mechanical coneand friction-cone penetrometers. It does not include the use of electric and electronic cones or data interpretation.1.2.1 The use of electric and electronic cones is covered inTest Method D 5578.1.3 Mechanical penetrometers of the type described in thistest method operate incrementally, using a telescoping pen-etrometer tip, resulting in no movement of the push rods duringthe measurement of the resistance components. Design con-straints for mechanical penetrometers preclude a completeseparation of the end-bearing and side-friction components.1.4 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are providedfor information only.1.5  This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. 2. Referenced Documents 2.1  ASTM Standards: D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 5778 Test Method for Performing Electronic FrictionCone and Piezocone Penetration Testing of Soil2.2  Other Standards: USBR D 7020 Performing Cone Penetration Testing of Soils-Mechanical Method  Earth Manual , Part II, ThirdEdition, U.S. Department of the Interior, Bureau of Reclamation, U.S. Government Printing Office, 1990“International Reference Test Procedure for the ConePenetration Test (CPT),” Proceedings of the First Interna-tional Symposium for Penetration Testing, ISOPT-1DeRuiter, ed., Blakema, Rotterdam, ISBN 90 6191 8014,1988. 3. Terminology 3.1  Definitions: 3.1.1  cone ,  n —the cone-shaped point of the penetrometertip, upon which the end-bearing resistance develops.3.1.2  cone penetrometer  ,  n —an instrument in the form of acylindrical rod with a conical point designed for penetratingsoil and soft rock and for measuring the end-bearing compo-nent of penetration resistance.3.1.3  cone resistance,  or  end-bearing resistance q c ,  n —theresistance to penetration developed by the cone equal to thevertical force applied to the cone divided by its horizontallyprojected area.3.1.4  cone sounding ,  n —the entire series of penetration testsperformed at one location when using a cone penetrometer.3.1.5  friction-cone penetrometer  ,  n —a cone penetrometerwith the additional capability of measuring the local sidefriction component of penetration resistance.3.1.6  friction cone sounding ,  n —the entire series of penetra-tion tests performed at one location when using a friction conepenetrometer.3.1.7  friction ratio, R  f  ,  n —the ratio of friction resistance tocone resistance,  f  s  /q c , expressed in percent. N OTE  1—The friction ratio for mechanical penetrometers is not com-parable to the friction ratio measured by electronic or electrical penetrom-eter (Test Method D 5778). Users should verify that the application of empirical correlations such as those predicting soil type from  R  f   are for thecorrect penetrometer. 3.1.8  friction resistance, f  s ,  n —the resistance to penetrationdeveloped by the friction sleeve, equal to the vertical forceapplied to the sleeve divided by its surface area. This resistanceconsists of the sum of friction and adhesion.3.1.9  friction sleeve ,  n —a section of the penetrometer tipupon which the local side-friction resistance develops.3.1.10  inner rods ,  n —rods that slide inside the push rods toextend the tip of a mechanical penetrometer.3.1.11  mechanical penetrometer  ,  n —a penetrometer thatuses a set of inner rods to operate a telescoping penetrometertip and to transmit the component(s) of penetration resistanceto the surface for measurement. 1 This test method is under the jurisdiction of Committee D-18 on Soil and Rock and is the direct responsibility of Subcommittee D18.02 on Sampling and RelatedField Testing for Soil Investigations.Current edition approved May 10, 1998. Published January 1999. Originallypublished as D 3441 – 75 T. Last previous edition D 3441 – 94. 1 AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr., West Conshohocken, PA 19428Reprinted from the Annual Book of ASTM Standards. Copyright ASTM  3.1.12  penetrometer tip ,  n —the end section of the pen-etrometer, which comprises the active elements that sense thesoil resistance, the cone, and in the case of the friction-conepenetrometer, the friction sleeve.3.1.13  push rods ,  n —the thick-walled tubes, or other suit-able rods, used for advancing the penetrometer tip to therequired test depth. 4. Significance and Use 4.1 This test method supplies data on selected engineeringproperties of soil intended to help with design and constructionof earthworks and the foundations for structures.4.2 This test method tests the soil in place and does notobtain soil samples. The interpretation of the results from thistest method requires knowledge of the types of soil penetrated.Engineers usually obtain this soil information from parallelborings and soil sampling methods, but prior information orexperience may preclude the need for borings.4.3 Engineers often correlate the results of tests by this testmethod with laboratory or other types of field tests or directlywith performance. The accuracy of such correlations will varywith the type of soil involved. Engineers usually rely on localexperience to judge this accuracy. 5. Apparatus 5.1  General :5.1.1  Cone —The cone shall have 60°( 6 5°) point angle anda base diameter of 1.406 6  0.016 in. (35.7  6  0.4 mm), resultingin a projected area of 1.55 in. 2 (10 cm 2 ). The point of the coneshall have a radius less than  1  ⁄  8  in. (3 mm).5.1.2  Friction Sleeve —having the same outside diameter+0.024 to –0.000 in. (+0.5 to –0.0 mm) as the base diameter of the cone (see 5.1.1). No other part of the penetrometer tip shallproject outside the sleeve diameter. The surface area of thesleeve shall be 23.2 in. 2 (150 cm 2 )  6 2 %.5.1.3  Steel —The cone and friction sleeve shall be madefrom steel of a type and hardness suitable to resist wear due toabrasion by soil. The friction sleeve shall have and maintainwith use a roughness of 63 µin. (1.6 µm) AA,  6 50 %.5.1.4  Push Rods —Made of suitable steel, these rods musthave a section adequate to sustain without buckling, the thrustrequired to advance the penetrometer tip. They must have anoutside diameter not greater than the diameter of the base of thecone for a length of at least 1.3 ft (0.4m) above the base, or, inthe case of the friction-cone penetrometer, at least 1.0 ft (0.3 m)above the top of the friction sleeve. Each push rod must havethe same constant inside diameter. They must screw or attachtogether to bear against each other and form a rigid-jointedstring of rods with a continuous, straight axis.5.1.5  Inner Rods —Mechanical penetrometers require aseparate set of steel or other metal alloy inner rods within thesteel push rods. The inner rods must have a constant outsidediameter with a roughness less than 125 µin. (3.2 µm) AA.They must have the same length as the push rods ( 6  0.004 in.or  6  0.1 mm) and a cross section adequate to transmit the coneresistance without buckling or other damage. Clearance be-tween inner rods and push rods shall be between 0.020 and0.040 in. (0.5 and 1.0 mm) (see 7.8.1).5.1.6  Measurement Accuracy —Maintain the trust-measuring instrumentation to obtain trust measurements within 6 5 % of the correct values. Measurement equipment (see5.2.5) should be subjected to calibration at regularly scheduledintervals such as annually or after a specified amount of accumulated testing. Examples of mechanical cone testingcalibration can be found in USBR D 7020 and ISOPT-1. N OTE  2—Special, and preferably redundant, instrumentation may berequired in the offshore environment to ensure this accuracy and theproper operation of all the remote systems involved. 5.2  Mechanical Penetrometers :5.2.1 The sliding mechanism necessary in a mechanicalpenetrometer tip must allow a downward movement of thecone in relation to the push rods of at least 1.2 in. (30.5 mm). N OTE  3—At certain combinations of depth and tip resistance(s), theelastic compression of the inner rods may exceed the downward strokethat the trust machine can apply to the inner rods relative to the push rods.In this case, the tip will not extend and the trust readings will riseelastically to the end of the machine stroke and then jump abruptly whenthe trust machine makes contact with the push rods. 5.2.2 Mechanical penetrometer tip design shall includeprotection against soil entering the sliding mechanism andaffecting the resistance component(s) (see 5.2.3 and Note 3).5.2.3  Cone Penetrometer  —Fig. 1 shows the design andaction of one mechanical cone penetrometer tip. A mantle of reduced diameter is attached above the cone to minimizepossible soil contamination of the sliding mechanism. N OTE  4—An unknown amount of side friction may develop along thismantle and be included in the cone resistance. 5.2.4  Friction Cone Penetrometer  —Fig. 2 shows the designand action of one telescoping mechanical friction cone pen-etrometer tip. The lower part of the tip, including a mantle towhich the cone attaches, advances first until the flange engagesthe friction sleeve and then both advance. N OTE  5—The shoulder at the lower end of the friction sleeve encoun-ters end-bearing resistance. In sand, as much as two thirds of the sleeveresistance may consist of bearing on this shoulder. Ignore this effect in softto medium clays. FIG. 1 Example of a Mechanical Cone Penetrometer Tip (DutchMantle Cone) D 3441 2  5.2.5  Measuring Equipment  —Measure the penetration re-sistance(s) at the surface by a suitable device such as ahydraulic or electric load cell or proving ring.5.3  Thrust Machine —This machine shall provide a continu-ous stroke, preferably over a distance greater than one push rodlength. The machine must advance the penetrometer tip at aconstant rate while the magnitude of the thrust requiredfluctuates (see 6.1.2). N OTE  6—Deep penetration soundings usually require a thrust capacityof at least 5 tons (45kN). Most modern machines use hydraulic pistonswith 10 to 20-ton (90 to 180-kN) thrust capability. 5.4  Reaction Equipment  —The proper performance of thestatic-thrust machine requires a stable, static reaction. N OTE  7—The type of reaction provided may affect the penetrometerresistance(s) measured, particularly in the surface or near-surface layers. 6. Procedure 6.1  General :6.1.1 Set up the thrust machine for a thrust direction as nearvertical as practical.6.1.2  Rate of Penetration —Maintain a rate of depth pen-etration of 2 to 4 ft/min (10 to 20 mm/s) 6  25 %. N OTE  8—The rate 2 ft/min (10 mm/s) provides the time the operatorneeds to properly read the resistance values when using the mechanicalfriction-cone penetrometer. The rate of 4 ft/min (20 m/s) is suitable for thesingle resistance reading required when using the mechanical conepenetrometers. The European standard requires 4 ft/min (20 mm/s). 6.2  Mechanical Penetrometers :6.2.1  Cone Penetrometers —( 1 ) Advance penetrometer tipto the required test depth by applying sufficient thrust on thepush rods, and ( 2 ) Apply sufficient thrust on the inner rods toextend the penetrometer tip (see Fig. 1). Obtain the coneresistance at a specific point (see 6.2.3) during the downwardmovement of the inner rods relative to the stationary push rods.Repeat step ( 1 ). Apply sufficient thrust on the push rods tocollapse the extended tip and advance it to a new test depth. Bycontinually repeating this two-step cycle, obtain cone resis-tance data at increments of depth. This increment shall notordinarily exceed 8 in. (203 mm).6.2.2  Friction-Cone Penetrometer  —Use the procedure asdescribed in 6.2.1, but obtain two resistances during step ( 2 )extension of the tip (see Fig. 2). First obtain the cone resistanceduring the initial phase of the extension. When the lower partof the tip engages and pulls down the friction sleeve, obtain asecond measurement of the total resistance of the cone plus thesleeve. Subtraction gives the sleeve resistance. N OTE  9—Because of soil layering, the cone resistance may changeduring the additional downward movement of the tip required to obtain thefriction measurement.N OTE  10—The soil friction along the sleeve puts an additional over-burden load on the soil above the cone and may increase cone resistanceabove that measured during the initial phase of the tip extension by anunknown but probably small amount. Ignore this effect. 6.2.3  Recording Data —To obtain reproducible cone-resistance test data, or cone and friction-resistance test data,when using a friction-cone tip, record only those thrustreadings that occur at a well-defined point during the down-ward movement of the top of the inner rods in relation to thetop of the push rods. Because of the elastic compression of inner rods (see Note 2), this point ordinarily should be at notless than 1.0 in. (25 mm) apparent relative movement of theinner rods. When using the friction-cone penetrometer, thispoint shall be just before the cone engages the friction sleeve. N OTE  11—Fig. 3 shows one example of how the thrust in the hydraulicload cell can vary during the extension of the friction-cone tip. Note the jump in gage pressure when the cone engages the sleeve. Obtain the cone plus friction-resistance reading assoon as possible after the jump so as to minimize the errordescribed in Fig. 3. Unless using continuous recording as inFig. 3, the operator should not record a cone plus frictionresistance if he suspects the cone resistance is changingabruptly or erratically. 7. Special Techniques and Precautions 7.1  Reduction of Friction Along Push Rods —The purposeof this friction reduction is to increase the penetrometer depthcapability, and not to reduce any differences between resistancecomponents determined by mechanical tips as noted in 1.3. Toaccomplish the friction reduction, introduce a special rod withan enlarged diameter or special projections, called a “frictionreducer,” into the string of push rods or between the push rodsand the tip. Another allowable method to reduce friction is touse push rods with diameter less than that of the tip. Any suchprojections or changes in diameter must meet the restrictions of 5.1.4. N OTE  12—Non-mechanical techniques to reduce friction, such as the FIG. 2 Example of a Mechanical Friction-Cone Penetrometer Tip(Begemann Friction-Cone) D 3441 3  use of drilling mud above the tip, are also allowable. 7.2  Prevention of Rod Bending Above Surface —Use atubular rod guide, at the base of the thrust machine, of sufficient length to prevent significant bending of the push rodsbetween the machine and the ground surface. N OTE  13—Special situations, such as when working through water, willrequire a special system of casing support to adequately restrict thebuckling of the push rods. 7.3  Drift of Tip —For penetration depth exceeding about 40ft (12 m), the tip will probably drift away from a verticalalignment. Occasionally, serious drifting occurs, even at lessdepth. Reduce drifting by using push rods that are initiallystraight and by making sure that the initial cone penetrationinto soil does not involve unwanted initial lateral thrust.Passing through or alongside an obstruction such as boulders,soil concentrations, thin rock layers, or inclined dense layers,may deflect the tip and induce drifting. Note any indications of encountering such obstructions and be alert for possiblesubsequent improper tip operation as a sign of serious drifting.7.4  Wear of Tip —Penetration into abrasive soils eventuallywears down or scours the penetrometer tip. Discard tips, orparts thereof, whose wear changes their geometry or surfaceroughness. Permit minor scratches.7.5  Distance Between Cone and Friction Sleeve —The fric-tion resistance of the sleeve applies to the soil at some distanceabove the soil in which the cone resistance was obtained at thesame time. When comparing these resistances for the soil at aspecified depth, for example when computing friction ratios orwhen plotting these data on graphs, take proper account of thevertical distance between the base of the cone and themid-height of the friction sleeve.7.6  Interruptions —The engineer may have to interrupt thenormal advance of a static penetration test for purposes such asremoving the penetrometer and drilling through layers orobstructions too strong to penetrate statically. If the penetrom-eter is designed to be driven dynamically without damage to itssubsequent static performance (those illustrated in Figs. 1 and2 are not so designed), the engineer may drive past such layersor obstructions. Delays of over 10 min due to personnel orequipment problems shall be considered an interruption. Con-tinuing the static penetration test after an interruption ispermitted, provided this additional testing remains in conform-ance with this test method. Obtain further resistance compo-nent data only after the tip passes through the engineer’sestimate of the disturbed zone resulting from the nature anddepth of the interruption. As an alternative, readings may becontinued without first making the additional tip penetrationand the disturbed zone evaluated from these data. Thendisregard data within the disturbed zone.7.7  Below or Adjacent Borings —A cone or friction-conesounding shall not be performed any closer than 25 boringdiameters from an existing, unbackfilled, uncased boring hole.When a sounding is performed at the bottom of a boring, theengineer should estimate the depth below the boring of thedisturbed zone and disregard penetration test data in this zone.The depth may vary from one to five diameters. Where theengineer does not have sufficient experience with this variable,depth of at least three boring diameters should be used.7.8  Mechanical Penetrometers :7.8.1  Inner Rod Friction —Soil particles and corrosion canincrease the friction between inner rods and push rods, possiblyresulting in significant errors in the measurement of the N OTE  1—“O-A” represents the correct cone resistance reading just before the pressure jump associated with engaging the friction sleeve during thecontinuing downward extension of the tip. “A-B” is the correct friction resistance if the friction sleeve could be engaged instantaneously and the coneplus friction resistance read instantaneously. However, the operator cannot read a pressure gage dial until it steadies, such as at Point “C.” By this forcedwait, the operator has introduced a friction resistance error of “B-C.” The operator must read the gage as soon as possible after the jump to minimizethis error. Erratic or abrupt changes in cone resistance may make this error unacceptable. FIG. 3 Annotated Chart Record of the Pressure Changes in the Hydraulic Load Cell Measuring Thrust on Top of the Inner Rods Duringan Example Extension of the Mechanical Friction-Cone Penetrometer Tip D 3441 4
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