ASTM D4436-2013 Standard Test Method for Rock Bolt Long-Term Load Retention Test《石栓长期负载保持力的标准试验方法》.pdf

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1、Designation: D4436 13Standard Test Method forRock Bolt Long-Term Load Retention Test1This standard is issued under the fixed designation D4436; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in

2、parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The objective of this test method is to determine thetime over which rock bolt tension decreases from the installedvalue to a designated minimum

3、 value.1.2 This test method is applicable to any anchor systemwhich is not fully encapsulated immediately upon installation,including mechanical, cement grout, resin (epoxy, polyester,and the like) or other similar systems.1.3 The values stated in inch-pound units are to be regardedas standard. The

4、values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard. Reporting of test results inunits other than inch-pounds shall not be regarded as noncon-formance with this test method.1.3.1 The gravitational system of inch-po

5、und units is usedwhen dealing with inch-pound units. In this system, the pound(lbf) represents a unit of force (weight), while the unit for massis slugs.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The pr

6、ocedures used to specify how data are collected/recorded or calculated, in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtainin

7、g the data, special purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analytic

8、almethods for engineering design.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 limitat

9、ions prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4435 Test Method for Rock B

10、olt Anchor Pull TestD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 DefinitionsFor definitions of common technical termsin this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 loadthe total axial force on the rock bolt.3.2

11、.2 design loadthe load specified for the rock boltduring the life of the project.3.2.3 installation loadthe load on the bolt immediatelyafter installation.3.2.4 stand timethe time required for the bolt load todecrease from the installation load to the design load.4. Summary of Test Method4.1 A rock

12、bolt is installed in the same manner and in thesame material as its intended support use. The load on the boltis monitored over a period of time, usually several weeks.5. Significance and Use5.1 Rock bolts are used for support in a variety of miningand civil engineering situations.3After a bolt is i

13、nstalled, theload generally decreases over time due to deterioration of theborehole wall, creep, and other factors. This process may be1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current ed

14、ition approved . Published December 2013. Originally approved in1984. Last previous edition approved in 2008 as D4436 08. DOI: 10.1520/D4436-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards v

15、olume information, refer to the standards Document Summary page onthe ASTM website.3For additional information see, “Suggested Method for Monitoring Rock BoltTension Using Load Cells,” Suggested Methods for Rock Bolt Testing, InternationalSociety for Rock Mechanics Commission on Standardization of L

16、aboratory andField Tests, 1974.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1arrested by fully encapsulating the bolt shortly after installa-tion. This is generally do

17、ne by pumping the bolt hole full ofcement grout, though synthetic resins may also be used. Thisencapsulation is generally done by pumping the bolt hole fullof cement grout, though synthetic resins may also be used. Therate of load loss determines the interval during which the boltmust be encapsulate

18、d during construction.5.2 The local characteristics of the rock, such as roughnessof the borehole and induced fractures, are significant factors inthe load loss characteristics of the bolt. To obtain realisticvalues, the test holes should be drilled using the same methodsas those used for the constr

19、uction boreholes.5.3 In establishing a testing program, the following factorsshould be considered:5.3.1 Load retention tests should be conducted in all rocktypes where construction bolts will be installed. If the rock isanisotropic, for example, bedded or schistose, the tests shouldbe conducted in t

20、he same orientations relative to the anisotropyas the construction bolts will be installed.5.3.2 In each rock type, at each orientation, and for eachanchor system, a sufficient number of tests should be con-ducted to determine the average and minimum long-termcapacities within a fixed uncertainty ba

21、nd at the 95 % confi-dence level. The allowable uncertainty band depends on theproject and involves such factors as rock quality, expectedproject lifetime, and importance of the areas to be bolted. Theuncertainty band determination will require considerable engi-neering judgment. As a rough guidelin

22、e, at least six long-termtests for a single set of variables have been found necessary tosatisfy the statistical requirements.5.3.3 The design load and installation load on the rock boltsystem should be predetermined. The installation load is lessthan the anchor capacity, as determined by Method D44

23、35. Thedesign load is less than the installation load; the amountdepends on rock properties and the minimum time required toencapsulate the bolts. Alternatively, this method can be run fora predetermined time interval based on constructionrequirements, and a realistic design load can be determinedfr

24、om the data.NOTE 1The quality of the result produced by this standard isdependent on the competence of personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing

25、/sampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Load CellA load cell shall be used

26、to measure thetension in the rock bolt. The cell may be of the mechanical,photoelastic, hydraulic, rubber compression pad, or electronictype. The electronic type is recommended. The cell shall havean accuracy of at least 6200 lbf (6890 N), including errorsintroduced by the excitation and read-out sy

27、stem, and aresolution of least 100 lbf (445 N).6.2 Anchor SystemsThe anchors used for testing shall befrom the manufacturers standard production stock. Mechani-cal anchors shall be inspected to make sure that no defectiveanchors are tested. Grout or resin shall be fresh (within theshelf life) and ob

28、tained from unopened containers. If groutedanchors are to be tested, make sure resin cartridge sizes arecompatible with hole diameter, rock bolt bar diameter andlength of anchorage required. For anchorages utilizing injectedgrout, make sure mixing and injection equipment and systemsare compatible wi

29、th manufacturers recommendations.6.3 Rock Bolt and AccessoriesThe rock bolt shall be ofsufficient diameter and strength so that its elastic range is notexceeded during the tests. Standard bearing plates, washers,and the like may be used as required to align the load cell. Aspherical bearing is desir

30、able on very uneven surfaces. Rockbolts used with grout or resin anchors shall have identicalungrouted bolt lengths.6.4 Drilling EquipmentThe same type of drilling equip-ment and drill bits that will be used for installing rock boltsduring the construction phase of the project shall be used asmuch a

31、s practical to drill the test holes.6.5 Torque WrenchIf expandable shell mechanical an-chors are used, a torque wrench shall be used to set them. Thetorque wrench shall also be used to load the bolts. It shall havea capacity at least 20 % greater than the manufacturersrecommended anchor-setting torq

32、ue. The torque wrench shallhave an accuracy of at least 62 % of the full-scale reading anda resolution of at least 1 % of the full-scale reading.6.6 Hydraulic Pulling SystemAs an alternative to thetorque wrench, a hydraulic ram and reaction frame may beused to tension the bolts.6.7 Borehole Diameter

33、 Measuring Gauge A gauge shallbe used to measure the diameter of the borehole at the anchorlocation. It shall have an accuracy of at least 60.02 in. (0.5mm) and resolution of at least 0.01 in. (0.25 mm).6.8 ThermometerA thermometer shall be used to measuretemperature in the borehole, within the anch

34、or zone if resin orcement grout anchorages are being tested. The temperature ofthe resin or grout shall also be measured at the time ofinjection. The thermometer should have an accuracy of at least60.5F (60.1C) and a resolution of at least 1F (0.5C). SeeNote 2.NOTE 2The accuracy and resolution for t

35、he thermometer are pre-sented in both Fahrenheit and Celsius units such that either type ofthermometer can be used as long as the accuracy and resolution require-ments as stated are met. The Celsius values are not direct conversionsfrom Fahrenheit.7. Procedure7.1 Do not locate the test area in a zon

36、e that will be affectedby future excavations, as rock response to stress changes canproduce load changes in the bolt.7.2 Drilling the Test Hole:7.2.1 Drill the test hole using the same procedure that willbe used during construction. Wash or blow the borehole cleanof all cuttings.7.2.2 The hole need

37、not be as deep as the proposed length ofthe construction rock bolts. It shall, however, be deep enoughD4436 132to set the anchor past the zone of disturbance caused by theexcavation and conform to the manufacturers specificationsfor optimum performance, considering also compatibility withactual fiel

38、d conditions. For mechanical shell anchors, drill thehole 1 ft (300 mm) past the end of the anchor. A holeapproximately 6 ft (1.8 m) in length has generally been foundto be adequate.7.2.3 Inspect the test hole visually using a flashlight, ormirror to reflect sunlight down the hole. If more than one-

39、halfof the bottom of the hole cannot be seen, the hole is notsufficiently straight for the test and shall not be used.7.2.4 Measure the test hole diameter in two perpendiculardirections at the top and bottom of the anchor location, usingthe borehole diameter measuring gauge, for a total of fourmeasu

40、rements.7.3 Preparation of AnchorsIf any anchor preparations,such as degreasing or rust removal, will be done duringconstruction, prepare the test anchors in the same way. If nospecial preparation is done during construction, do not preparethe anchors.7.4 Setting the Anchor:7.4.1 If mechanical ancho

41、rs are used, lightly lubricate thedownhole end of the rock bolt and screw on the anchor. Whenin position, torque the bolt to the manufacturers recommen-dations to set the anchor. A pair of jam-nuts on the upper endof the rod may be used to apply torque without producing axialload in the bolt. If the

42、 manufacturers torque cannot beachieved because of anchor slippage due to shear failure in therock, note the maximum torque reading and install subsequentanchors to 80 % of this value. Do not test anchors whererotation occurs between rock bore hole surface and anchor. Inall cases, record any slippin

43、g or other anomalous behavior asshown in Fig. 1.7.4.2 Install grout or resin anchors according to the manu-facturers recommendations.7.4.3 Read and record the temperature in the boreholewithin the anchor zone to the nearest 1F (0.5C); the tempera-ture of the resin or grout at the time of injection a

44、nd theambient air temperature. Ideally the test anchorages should beinstalled under the same temperature conditions as expectedduring construction. The time required for resin or groutanchorages to reach their design strengths is temperatureFIG. 1 Rock Bolt Long Term Load Retention Test Sample FormD

45、4436 133dependent and may vary significantly. Consult the resin orgrout manufacturers literature for recommended curing timesunder various temperature conditions. Curing times may bevaried between 1 to 5 days under similar temperature condi-tions to assess the effects of curing time on strength. Toe

46、valuate the influence of grouted bond length on anchorstrength, several anchorage lengths should be tested, ideallyunder similar temperature conditions and curing times.7.5 Loading the Bolt:7.5.1 The torque wrench is recommended for tensioning thebolt.Alternatively, the hydraulic pulling system may

47、be used toapply load. In this case, attach a pulling rod to the rock boltabove the nut. Apply the load hydraulically, then tighten thenut. As the nut is tightened, the hydraulic pressure decreasesbecause the load is transferred from the ram to the nut.7.5.2 Tension the bolt until the load cell indic

48、ates that theinstallation load has been achieved.7.5.3 Read and record the installation load to the nearest 100lbf (0.44 kN).7.6 Reading IntervalsRead and record the load to thenearest 100 lbf (0.44 kN ) on the bolt at least twice daily for aperiod of 2 weeks after installation, and once daily there

49、after.Bolts in rapidly yielding material may require more frequentreadings.8. Calculation8.1 For each test, plot the load on the rock bolt as a functionof time, as shown in Fig. 2. If either design load or stand timeis specified, the other may be determined from the graph.8.2 For each group of tests in a similar rock type, with thesame anchor type and orientation (if applicable), calculate themean and uncertainty of the loads at the 95 % confidencelevel.49. Report: Test Data Sheet(s)/Form(s)9.1 The methodology used to specify how data are recordedon