1、Designation: D4436 131Standard 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.1NOTEEditorial corrections were made throughout in February 2014.1. Scope*1.1 The objective of this test method is to determine thetime over which rock bolt
3、 tension decreases from the installedvalue to a designated minimum 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 UnitsTh
4、e values stated in inch-pound units are to beregarded as standard. The values given in parentheses aremathematical conversions to SI units that are provided forinformation only and are not considered standard. Reporting oftest results in units other than inch-pounds shall not beregarded as nonconfor
5、mance with this test method.1.3.1 The gravitational system of inch-pound 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 sign
6、ificant digits and rounding established inPractice D6026.1.4.1 The procedures 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 pro
7、ce-dures used do not consider material variation, purpose forobtaining 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
8、scopeof this standard to consider significant digits used in analyticalmethods 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 he
9、alth practices and determine the applica-bility of regulatory limitations 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 asUs
10、ed in Engineering Design and ConstructionD4435 Test Method for Rock Bolt 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
11、to This Standard:3.2.1 loadthe total axial force on the rock bolt.3.2.2 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 inst
12、allation load to the design load.4. Summary of Test Method4.1 A rock 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.1This test method is under the jurisdiction of ASTM Committee D
13、19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 1984. Last previous edition approved in 2008 as D4436 08. DOI:10.1520/D4436-13E01.2For referenced ASTM standards,
14、 visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM Internationa
15、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 Rock bolts are used for support in a variety of miningand civil engineering situations.3After a bolt is installed, theload generally decreases over time due to deterioration of theboreho
16、le wall, creep, and other factors. This process may bearrested by fully encapsulating the bolt shortly after installa-tion. This encapsulation is generally done by pumping the bolthole full of cement grout, though synthetic resins may also beused. The rate of load loss determines the interval during
17、 whichthe bolt must be encapsulated 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 m
18、ethodsas those used for the construction 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,
19、 the tests shouldbe conducted in the 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-termcapaci
20、ties within a fixed uncertainty band 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-nee
21、ring judgment. As a rough guideline, 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 cap
22、acity, as determined by Test MethodD4435. The design load is less than the installation load; theamount depends on rock properties and the minimum timerequired to encapsulate the bolts.Alternatively, this method canbe run for a predetermined time interval based on constructionrequirements, and a rea
23、listic design load can be determinedfrom 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 cap
24、able of competentand objective testing/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
25、.1 Load CellA load cell shall be used 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 errorsintrod
26、uced by the excitation and read-out system, 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
27、be fresh (within theshelf life) and obtained 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
28、equipment and systemsare compatible with 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
29、load cell. Aspherical bearing is desirable 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
30、 of the project shall be used asmuch as 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 manufa
31、cturersrecommended anchor-setting torque. 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 t
32、ension the bolts.6.7 Borehole Diameter 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 measuretemper
33、ature in the borehole, within the anchor 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.N
34、OTE 2The accuracy and resolution for the 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.
35、1 Do not locate the test area in a zone that will be affectedby future excavations, as rock response to stress changes canproduce load changes in the bolt.3For additional information see, “Suggested Method for Monitoring Rock BoltTension Using Load Cells,” Suggested Methods for Rock Bolt Testing, In
36、ternationalSociety for Rock Mechanics Commission on Standardization of Laboratory andField Tests, 1974.D4436 13127.2 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 not
37、be as deep as the proposed length ofthe construction rock bolts. It shall, however, be deep enoughto set the anchor past the zone of disturbance caused by theexcavation and conform to the manufacturers specificationsfor optimum performance, considering also compatibility withactual field conditions.
38、 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-halfof the bo
39、ttom 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 fourmeasurements.7.3 P
40、reparation 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 anchors are used,
41、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 manufacturer
42、s 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 surface and anchor. In all cases,record any slipping or other anomalous be
43、havior as shown inFig. 1.7.4.2 Install grout or resin anchors according to the manu-facturers recommendations.FIG. 1 Rock Bolt Long Term Load Retention Test Sample FormD4436 13137.4.3 Read and record the temperature in the boreholewithin the anchor zone, the temperature of the resin or grout atthe t
44、ime of injection, and the ambient air temperature to thenearest 1F (0.5C). 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 temperaturedependent and m
45、ay 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. Toevaluate the influence o
46、f 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 be used toapply load. I
47、n 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 indicates that theinstallati
48、on load has been achieved.7.5.3 Read and record the installation load to the nearest 100lbf (0.44 kN).7.6 Read and record the load to the nearest 100 lbf (0.44 kN)on the bolt at least twice daily for a period of 2 weeks afterinstallation, and once daily thereafter. Bolts in rapidly yieldingmaterial
49、may require more frequent readings.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 the test data sheet(s)/form(s) as
