1、Designation: D7401 08Standard Test Methods forLaboratory Determination of Rock Anchor Capacities by Pulland Drop Tests1This standard is issued under the fixed designation D7401; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the quantitative determinationof the working and ultimate static or dynamic capacities
3、 of fullscale rock anchors. Dynamic capacities are determined tosimulate rockburst and blasting conditions (1).2The rockanchors are installed in steel pipe to simulate standard bore-holes sizes. Rock anchor capacities are determined as afunction of resin to steel bolt bond strength and steel bolt yi
4、eldstrength. These tests are not intended to determine rock anchorto borehole rock surface shear strength.1.2 These test methods are applicable to mechanical, resin,or other similar anchor systems.1.3 Two methods are provided to determine the capacities ofrock anchors, as follows:1.3.1 Method AUsing
5、 a horizontal hydraulically loadedpull test system.1.3.2 Method BUsing a vertical dynamically loaded droptest system.1.4 The values stated in SI units are to be regarded as thestandard. No other units of measurement are included in thisstandard.1.5 All observed and calculated values shall conform to
6、 theguidelines for significant digits and rounding established inPractice D6026.1.6 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 det
7、ermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D653 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 Desi
8、gn and ConstructionD4435 Test Method for Rock Bolt Anchor Pull TestD4436 Test Method for Rock Bolt Long-Term Load Reten-tion TestD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 DefinitionsRefer to Terminology D653 for specificdefinitions.3.2 Definitions of Terms Spec
9、ific to This Standard:3.2.1 linescan cameraa camera with high optical linearresolution that captures two-dimensional images by moving theobject perpendicularly to the scan line.3.2.2 maximum loadrepresents the highest load valuerecorded during the test.3.2.3 rock anchorusually constructed of steel,
10、which isinserted into pre-drilled holes in rock and secured with a fixingagent for the purpose of ground control.3.2.4 RPMacronym for revolutions per minute.3.2.5 transverse stiffnessthe ability of the borehole or steeltube wall to deform radially.3.2.6 yield loadcorresponds to the onset of plastic
11、defor-mation.4. Summary of Test Methods4.1 A rock anchor is installed in a steel pipe instead of aborehole the same manner and in the same material as its1These test methods are under the jurisdiction of ASTM Committee D18 on Soiland Rock and are the direct responsibility of Subcommittee D18.12 on R
12、ockMechanics.Current edition approved Jan. 1, 2008. Published February 2008. DOI: 10.1520/D7401-08.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at se
13、rviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and re
14、placed by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest information1intended use (2). In the Pull test, the rock anchor is hydrauli-cally pulled horizontally and the displacement of the bolt headis measured concurrently. The bolt is pulled until the anchorsystem
15、 fails (or to the ultimate stroke of the ram). The ultimateand working capacity of the rock anchor is calculated from theplot of load versus displacement. In the Drop test, a knownmass is released vertically impacting on a plate at a presetdistance that is in turn affixed to the end of a rock anchor
16、. Themaximum energy is expressed in kJ.5. Significance and Use5.1 For a support system to be fully effective, the supportsystem must be able to contain the movement of rock materialdue to excavation stress release, slabbing, etc. Data from theload tests are used by engineers to design the appropriat
17、esupport system to improve safety and stability of undergroundsupport systems. Test Methods D4435 and D4436 are used forin-situ load tests.5.2 The local characteristics of the rock, such as roughnessand induced fractures, are significant factors in the anchorstrength. The material used to simulate t
18、he borehole surfaceshould be sufficiently roughened so that failure occurs in therock anchor and not at the simulated anchor-rock surface. Inthe case of steel pipe, internal threading using different spacingand depth is accomplished using a machinists lathe to simulateroughness.NOTE 1The quality of
19、the result produced by this standard isdependent on the competence of the 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/sampling/inspection/etc. Use
20、rs 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 these factors.6. Apparatus6.1 Components Common to Both Test Methods:6.1.1 The manufacturer pr
21、ovides the rock anchors, plates,nuts, domes, washers, bottom plate, resins, and steel tubes forthe tests. The manufacturer specifies the borehole size, type ofresin, penetration rate and rotation rate for the installation ofthe rock anchor and any other installation information.6.1.2 Upon receipt, t
22、he rock anchor measurements includelength, rod diameter, length and diameter of the threaded part,length and diameter of the mixing element and any specificcharacteristics.6.1.3 Boreholes are simulated by 12 mm-thick cold rolledsteel tubes of the required internal diameter. The steel tubepreparation
23、 includes a slight roughening of the inside surfaceover approximately the last meter. This roughened section isreferred to as the top of the tube. Two sets of 25.4 mm holes aredrilled near the top of the tube. The top set supports the tube inthe drop test apparatus and the lower holes allow access t
24、o theend of the rock anchor after installation. For each rock anchor,two holes are drilled through the top end of the rock anchor toallow the clevis to be attached during testing.6.2 Method APull Test System (Static):6.2.1 A double acting hollow hydraulic ram, with a mini-mum load capacity of 325 kN
25、 and displacement of 150 mm isrecommended for this test. Displacement positioning of theram is accomplished using a hand operated pump. A handpump is used during the controlled loading. Once the rockanchor or the resin starts to fail, an electric pump (Px) can beused until the specimen fails or the
26、ram reaches its strokecapacity. Fig. 1 displays a typical pull test set-up.6.2.2 The ram hydraulic pressure is monitored using anelectronic pressure transducer. Two 25.4 mm stroke potenti-ometers with a resolution of 0.6 mm are recommended fordisplacement measurements. The potentiometers measure the
27、plate and the end displacements during the test.All instrumentsare connected to a data acquisition system.6.3 Method BDrop Test System (Dynamic):6.3.1 The drop or dynamic test system (Fig. 2) shallaccommodate a height of drop of the mass of at least 2.0 mbelow the coupler pin. The mass capacity of 1
28、 ton, (1T) shallnot be less than 325 kN. As the energy input is controlled bythe drop height and the mass, the maximum energy availableand the maximum impact velocity that each drop can reach are62 kJoules and 6.5 m/s, respectively.6.3.2 Instrumentation used to measure the loads and thedisplacements
29、 are measured at the plate and at the end of therock anchor. Displacements in some systems are measuredusing linescan cameras. The cameras are sampled at 10 000lines per second to match the sampling of the analog signals.The lines are amalgamated to form an image of distance versustime. The location
30、 of black and white targets attached to theplate nut or to the bolt end, is detected within the image. Thissystem measures loads using arrays of four piezoelectric forcesensors, sandwiched between two platen rings.FIG. 1 Schematic of Pull Test SystemD7401 0826.3.3 All instruments are connected to a
31、data acquisitionsystem. The impact duration is typically 60 ms, but data arerecorded for about 1.5 s before and up to 5 s after the impactto ensure that all instruments have stabilized.7. Procedure7.1 Encapsulated Resin Anchor Bolt Specimen Installation:7.1.1 Insert into the tube (see Fig. 3), a plu
32、g, which extendsfrom the top of the specimen tube to below the second set of25.4 mm holes. This prevents the end of the rock anchor andthe resin from being installed past this point.7.1.2 Insert additional plugs into the bottom set of holes toprevent resin from escaping during installation.7.1.3 Pla
33、ce the specimen tube in a jig to align it with thedrill.7.1.4 Prior to installation, slide the rock anchor specimencompletely into the tube.7.1.5 Mark the collar position and orientation of the mixingelement on the rock anchor specimen. These lines are usedduring installation to ensure that the rock
34、 anchor is fullyinserted and to identify the paddle orientation.7.1.6 Thread the two nuts completely onto the rock anchorand tighten them in order to seat the drill chuck.7.1.7 Remove the rock anchor and slide the resin cartridgesare into the end of the tube.7.1.8 Insert the rock anchor into the chu
35、ck, which isattached to a drill mounted on a sliding rail with an indepen-dent advance drive system.7.1.9 Spin the rock anchor into the tube at a steadyadvancement and constant RPM rate.FIG. 2 Schematic of Drop Test SystemFIG. 3 Schematic of Installation SystemD7401 0837.1.10 Once the rock anchor re
36、aches the plug, stop theadvance and rotate the rock anchor for an additional 5 seconds.7.1.11 Remove the drill and rotate the lines, indicating themixing element orientation, to the horizontal.7.1.12 Remove the tube from the jig, and remove all theplugs.7.1.13 Remove any resin beyond the end through
37、 the holesin the tube.7.1.14 Clean the mixing element and the end of the rockanchor, including its two small holes.7.1.15 An electric motor (1 hp), capable of generating 150to 400 RPM, is used to simulate the mechanized (that is, bolter)installation. The installation set-ups are tightly controlled i
38、norder to improve the mixing and to minimize the differences inmixing quality between specimens. The set-ups can be readilyadjusted to provide the penetration rate and rotational speedrequired.7.2 Method APull Test:7.2.1 Attacha1mlong high yield strength wire (pianowire) to the end of the rock ancho
39、r, and feed the wire out thetop of the tube.7.2.2 Reinstall the tube in the installation jig and connect thepiano wire to a potentiometer.7.2.3 Install the 300 mm diameter12 mm thick steel plate,150 mm stroke 325 kN hollow ram and the heavy washer overthe end of the rock anchor up against the tube.
40、Thread on thenut on and tighten the entire assembly.7.2.4 Attach the second potentiometer to the nut.7.2.5 Use the potentiometers to measure the plate and theend displacements during the test.7.2.6 Use both a hand pump and an electric pump to powerthe hollow ram. Use the hand pump during the test pr
41、ior to rockanchor failure.7.2.7 Once the rock anchor or the resin starts to fail, use theelectric pump until the specimen fails or the ram reaches itsstroke capacity.7.3 Method BDrop Test:7.3.1 Set-up the predetermined mass to be dropped.7.3.2 Install the clevis on the end of a thin-walled tube that
42、runs up through the center of the support assembly for thespecimen tube. The clevis connects the thin-walled tube to theend of the rock anchor.7.3.3 Measure the end displacement with a linescan camera,which monitors a target on the thin-walled tube.7.3.4 Insert the rock anchor through the center of
43、the magnetand the mass.7.3.5 Insert the top of the specimen tube into the receiverend of the drop test support assembly.A25.4 mm bolt suspendsthe tube in place. The 25.4 mm bolt has a small hole throughits middle to allow for the passage of the clevis to the end ofthe rock anchor.7.3.6 Lower the cle
44、vis onto the end of the rock anchor.7.3.7 Use two machine screws to attach the clevis to thecone.7.3.8 Lower the magnet on to the mass.7.3.9 Lift the mass with the overhead crane hoists.7.3.10 Install the 12 mm-thick impact plate, the rock anchorplate, the dome washer and the threaded nut on the thr
45、eadedend of the cone bolt.7.3.11 Install the target under the threaded nut, for the lowerlinescan camera.7.3.12 Calibrate the lights and the two linescan cameras(lower and upper).7.3.13 Lower the mass onto the impact plate.7.3.14 Move the crane hoists from the mass to the magnet.7.3.15 Start the dat
46、a acquisition system.7.3.16 Lift the mass magnetized to the electromagnet to thedesired height. The electromagnet is lifted with the pair ofsynchronized cranes mounted on the top of the machine.7.3.17 Cut the power to the magnet, to free fall the massonto the specimen.7.3.18 Acquire data from the pl
47、ate and end displacementmonitors.7.3.19 Acquire data from the load cells attached to the frameabove the specimen and below the plate. Use a suitable frameload cell such as an array of four piezoelectric force sensorssandwiched between two platen rings. Locate sensors on top ofthe frame crossbeams. L
48、ocate another set of piezoelectricsensors on the threaded part of the bolt just below the plate.7.3.20 Use linescan cameras to acquire displacements at10 000 lines per second to match the sampling of the analogsignals. The location of a black and white target, attached to theplate nut or to the end,
49、 is detected within the image. Linescancamera lines are amalgamated to form an image of distanceversus time.7.3.21 Drops could be repeated until the rock anchor fails oruntil the appropriate cumulative amount of energy desired isreached.7.4 Post Test Inspection:7.4.1 Mechanically cut specimens open lengthwise aftertesting is completed.7.4.2 Compare the actual end displacement to the testresults.7.4.3 Inspect visually and record the quality of the resinmixing visually based on color, relative hardness, or both.TABLE 1 Geometric Description of the Rock A
