1、Designation: D4729 08Standard Test Method forIn Situ Stress and Modulus of Deformation Using FlatjackMethod1This standard is issued under the fixed designation D4729; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The flatjack test measures stress at a rock surface. Themodulus of deformation and the long-term deformationalproperties
3、(creep) may also be evaluated.1.2 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.2.1 The method used to specifiy how data are collected,calculated, or recorded in this standard is not directly related tothe accurac
4、y to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.3 LimitationThe flatjack test measures the averagestress normal to the surface of the test chamber. Undisturbedstress levels must be determined by theoret
5、ical interpretationsof these data.1.4 Assumptions and Factors Influencing the Data:1.4.1 The stress relief is assumed to be an elastic, reversibleprocess. In nonhomogeneous or highly fractured materials, thismay not be completely true.1.4.2 The equations assume that the rock mass is isotropicand hom
6、ogeneous. Anisotropic effects may be estimated bytesting in different orientations.1.4.3 The flatjack is assumed to be 100 % efficient. Thedesign and size requirements of 7.1 were determined to satisfythis requirement to within a few percent.1.4.4 The jack is assumed to be aligned with the principal
7、stresses on the surface of the opening. Shear stresses are notcanceled by jack pressure. Orientating the tests in threedirections in each plane tested prevents the misalignment frombeing excessive for at least one of the tests.1.5 The values stated in inch-pound units are to be regardedas standard.
8、The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.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
9、 to establish appro-priate safety and health practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD2113 Practice for Rock Core Drilling and Sampling ofRock for Site Ex
10、plorationD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD5720 Practice for Static Calibration of ElectronicTransducer-Based Pressure Measurement Systems forGeotechnical PurposesD6026 Practice for
11、Using Significant Digits in GeotechnicalDataD6027 Practice for Calibrating Linear Displacement Trans-ducers for Geotechnical Purposes (Withdrawn 2013)33. Terminology3.1 For terminology used in this test method, refer toTerminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 cancell
12、ation pressurethe pressure in the flatjackrequired to return the rock to its initial position.3.2.2 skin stressthe tangential stress at the surface of anopening.3.2.3 undisturbed stressthe stress field existing in a rockmass prior to excavation of an opening.1This test method is under the jurisdicti
13、on ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 1987. Last previous edition approved in 2004 as D4729 04. DOI: 10.1520/D4729-08.2For referenced ASTM sta
14、ndards, 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.3The last approved version of this historical standard is referenced onwww.astm.org.*
15、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 StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www
16、.astm.org) for the latest information14. Summary of Test Method4.1 The in situ stress in the rock mass is relieved by cuttinga slot into the rock perpendicular to the surface of the test adit.The deformation caused by this stress relief is measured. Ahydraulic flatjack is placed into the slot and is
17、 pressurized untilthe above-measured displacement is canceled. This reappliedstress is approximately equal to the stress in the rock mass atthe test location in a direction perpendicular to the plane of thejack. The deformational characteristics of the rock mass areevaluated by incrementally loading
18、 the flatjack and measuringthe deformation.5. Significance and Use5.1 Tests in Orthogonal DirectionsThe flatjack most ac-curately determines the stress parallel to the long axis of theadit, because this stress is the least affected by the presence ofthe opening. (The other tangential stress is highl
19、y concen-trated.) In addition, if the adit is in a stress field where one ofthe stresses is significantly larger than the others (3 or 4 times),certain locations in the adit may be in very low compressive oreven tensile stress. Flatjack tests in these locations can giveanomalous and misleading resul
20、ts. Because of these factors, thetest adit should have at least two, and preferably three, long (atleast 4 to 5 times the diameter), straight sections at about 90to each other. Testing should be distributed evenly in all threesections to provide redundant data and, if results in one sectionare anoma
21、lous, to allow the program to produce sufficientusable data.NOTE 1Not withstanding the statements on precision and biascontained in this test method; the precision of this test method isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities use
22、d. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing. Users of this test method are cautioned thatcompliance with Practice D3740 does not in itself assure reliable testing.Reliable testing depends on many factors; Practice D3740 provi
23、des ameans of evaluating some of those factors.6. Interferences6.1 Personnel Prequalification:6.1.1 Test PersonnelAll personnel involved in performingthe test, including the technicians and test supervisor, shall beformally prequalified.6.1.2 Drilling and Sawcut PersonnelQuality drilling andsawcutti
24、ng is important to achievement of successful flatjacktests. The drilling and sawcut personnel should be capable ofperforming the precision necessary to successfully produce theslot and instrument holes.6.2 Equipment Performance VerificationThe complianceof all equipment and apparatus with performanc
25、e specificationsapparatus shall be verified. If no requirements are stated, themanufacturers specifications for the equipment shall be therequired level of performance. Performance verification isgenerally done by calibrating the equipment and measurementsystems. Calibration and documentation shall
26、be accomplishedaccording to standard procedures such as in Practices D5720and D6027.6.3 Local Geologic FeaturesLocal features, particularlyfaults, shear zones, etc., can influence the local stress field.Large inclusions in the rock can affect both the stress anddeformational properties. Test locatio
27、ns should be carefullyselected so that the effects of such features are minimized or, ifthey are the features of interest, accounted for fully.6.4 Influence of ExcavationsOther excavations intersect-ing the test adit will cause complex stress concentration effectsby superposition. Flatjack tests sho
28、uld be located at least threediameters of the intersecting feature away from that feature. Ifthe test adit is excavated by conventional methods, then thesurfaces for testing should be further excavated by nonblastingtechniques to remove loose material resulting from stress reliefor blasting.7. Appar
29、atus7.1 FlatjacksFlatjacks shall be designed to operate atpressures of several thousand pounds per square inch whenproperly installed. The jacks shall be constructed so that thetwo main plates move apart in essentially a parallel mannerover the range of the jack. The range shall be at least 0.25 in.
30、(6 mm). The jacks covered by this standard are square and thearea of the jack shall be no less than 2 ft (0.6 m) wide.NOTE 2Other flat jack shapes are available that may be better suitedfor specific applications. This standard only covers the basic square flatjack, however the basic principles discu
31、ssed here will still apply.7.2 Instrumentation:7.2.1 PressureElectronic transducers or hydraulic gaugesmay be used to monitor flatjack pressure. The pressure trans-ducer shall have an accuracy of at least 620 lbf/in.2(60.14MPa), including errors introduced by the readout system and asensitivity of a
32、t least 10 lbf/in.2(0.069 MPa).7.2.2 DeformationDeformation measurement devices in-cluding mechanical dial gauges, and electronic transducerssuch as LVDTs or linear potentiometers. The devices can beeither stationary, or portable depending on the site require-ments. The deformation device shall have
33、 an accuracy of atleast 60.0001 in. (60.0025 mm) and a sensitivity of at least0.00005 in. (0.0013 mm).7.2.3 Internal GaugesStrain gauges inside the flatjackshall be calibrated prior to installation in the jack. The effectsof the hydraulic oil and ambient pressure increase on thegauges shall be deter
34、mined prior to testing.7.3 MortarIf mortar is used to cement the flatjack into theslot, a high-early strength, non-shrink material shall be used.The mortar may include up to 50 % clean sand by weight, withgrain size between 20- and 60-mesh. Clean, potable water shallbe used for the mortar. The cured
35、 mortar shall have a strengthgreater than the stress applied by the flatjack. The modulus ofthe mortar may be required to be removed from some of thedeterminations of rock modulus.7.4 Sawing EquipmentEquipment used to saw a slot in therock should be of a type where large center or end holes are notr
36、equired. These large holes can cause serious changes in thestress field to be measured.8. Procedure8.1 Groups at Each Test StationAt least one group ofjacks should be tested in each adit section. Each group shouldhave three flatjacks installed horizontally inclined 45 andD4729 082vertically. The jac
37、ks in each group should all be placed in onepart of the adit within 20 ft (6.1 m) of each other along thelength of the adit.8.2 Surface Preparation:8.2.1 Rock QualityThe flatjack and deformation instru-mentation should not be installed in loose, broken, or drummymaterial. Loose, broken, or drummy ma
38、terial may be detectedby a dull, hollow sound when struck with a hammer; suchmaterial should be removed.8.2.2 DimensionsThe prepared surface shall extend atleast 1 ft (0.30 m) past either end of the flatjack slot and at least1 ft (0.30 m) past the furthest measuring points. The transduc-ers or flatj
39、ack shall be 1 ft (0.30 m) inside the prepared surfaceat any point (see Fig. 1).8.2.3 MethodDrilling to a uniform depth may be requiredto prepare the rock face. Residual rock between the drill holesmay be removed by moving the bit back and forth until asmooth surface is achieved. Alternatively, in h
40、ard, competentrock, controlled blasting with very small charges may be usedto remove the residual rock. In softer material, coarse grinding,chipping, or cutting devices may be required.8.2.4 SmoothnessIdeally, the prepared surface shall be aplane. The difference between the highest and lowest points
41、 onthe prepared surface shall be not greater than 2 in. (50 mm).8.3 Transducer and Measurement Points InstallationTransducers and measurement points shall be installed on thecenterline normal to the flatjack, either at the surface or atdepth as shown in Fig. 1. Transducers for stress determinationsh
42、all be installed within L/2 of the flatjack slot, where L is thewidth of the flatjack.8.4 Slot CuttingThe slot can be formed by sawing or bydrilling overlapping holes in weak or highly fractured material.Vibration should be minimized. The slot shall be no more than3 in. (74 mm) wide, and extend no m
43、ore than 3 in. (75 mm)past the edges of the flatjack. It shall be deep enough that theflatjack may be inserted 3 in. (75 mm) beyond the lowest pointon the rock fact adjacent to the slot. If drilled, care shall betaken that the holes are straight and parallel to keep the bottomof the slot open to rec
44、eive the jack. The slot shall be washedclean of all dirt and cuttings, using clean water.8.5 Relaxation MeasurementsDeformation shall be mea-sured immediately upon completion of slot cutting and againimmediately prior to testing. If the rock undergoes strain underconstant load over a period of time,
45、 several intermediatereadings shall be taken to evaluate this effect.8.6 Flatjack InstallationFlatjacks shall be centered in theslot and recessed 3 in. (75 mm) from the face of the excavationto minimize the possibility of rupture during pressurization.The mortar, if used, should surround the jack an
46、d shall be freefrom voids. The jack shall be installed to allow sufficient timefor the mortar to attain compressive strength greater thanmaximum anticipated jack stress.8.7 Flatjack TestingThe flatjack pressure shall be raised in100 lb/in.2(0.7 MPa) increments until cancellation of allmeasuring poin
47、ts has been achieved. Deformation shall be readafter each pressure increment. The peak pressure shall bemaintained for 15 min to check for time-dependent deforma-tion; deformation readings shall be taken every 5 min. Thepressure shall be reduced in 100 lb/in.2(0.7 MPa) decrementsto zero, with deform
48、ation read after every decrement. Zeropressure shall be maintained for 15 min to check for time-dependent deformation; deformation readings shall be takenevery 5 min. The cycle shall be repeated at least two moretimes using equal pressure increments and decrements. Thepeak jack stress of these cycle
49、s should be as high as possibleand be determined by the test engineer in the field dependingon the jack and rock strength and the cancellation pressure.8.8 Data Recording RequirementsExamples of test datasheets and the type of data to record are shown on Figs. 2 and3. However, the data requirements may be site specific andshall be developed using the minimum requirements specifiedin Section 10, Reports.FIG. 1 Recommended Flatjack Measurement Array, Surface Mea-surementsFIG. 2 Flat Jack Test Site Description Data SheetD4729 0839. Calcu
