1、Designation: D 4971 08Standard Test Method forDetermining In Situ Modulus of Deformation of Rock UsingDiametrically Loaded 76-mm (3-in.) Borehole Jack1This standard is issued under the fixed designation D 4971; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year 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. Scope*1.1 This test method covers the estimation of in situmodulus of a rock mass at va
3、rious depths and orientations.Information on time-dependent deformation may also be ob-tained.1.2 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.2.1 The method used to specify how data are collected,calculated, or
4、 recorded in this standard is not directly related tothe accuracy 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 The values stated in SI units are to be regarded as thestandard. The values given in par
5、entheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 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
6、 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Ins
7、pection of Soil and Rock asUsed in Engineering Design and ConstructionD 6026 Practice for Using Significant Digits in Geotechni-cal DataD 6032 Test Method for Determining Rock Quality Desig-nation (RQD) of Rock Core3. Terminology3.1 See Terminology D 653 for general definitions.3.2 Definitions of Te
8、rms Specific to This Standard:3.2.1 deformationchange in shape or size, (see Terminol-ogy D 653). In this test method deformation is the change inthe diameter of the borehole.3.2.2 modulus of deformationratio of stress to strain for amaterial under given loading conditions; numerically equal tothe s
9、lope of the tangent or the secant of the stress-strain curve.The use of the term modulus of elasticity is recommended formaterials that deform in accordance with Hookes law, and theterm modulus of deformation is recommended for materialsthat deform otherwise, (see Terminology D 653). In this testmet
10、hod, the modulus of deformation is calculated from theapplied fluid pressure, the relative change in hole diameter, afunction of Poissons ratio, and a constant.3.2.3 jack effciencyratio of the jack plate pressure to theapplied hydraulic pressure.4. Summary of Test Method4.1 The 76 mm (3.0 in.) jacks
11、, (see Fig. 1 and Fig. 2), induceundirectional pressure to the walls of a borehole by means oftwo opposed curved steel platens each covering a 90 sector,over a length of 20.3 cm (8 in.).4.2 Raw data from a test consist of hydraulic-line pressure,Qh, versus readout from linear variable differential t
12、ransform-ers (LVDTs) measuring platen movement. Knowing the dis-placement calibration of the LVDTs, the raw data can betransformed to a test record of hydraulic pressure versus holediameter, D. For each increment of pressure, DQh, and holedeformation, DD, theoretical data analysis (1),3assuming rigi
13、djack plates and full 90 contact, give the theoretical rock massmodulus, E (Etheoretical) as a function E=f (D QhDD T*),where T* is a coefficient dependent upon Poissons ratio. If Eis measured on a linear segment of the loading curve, common1This test method is under the jurisdiction ofASTM Committe
14、e 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 1989. Last previous edition approved in 2006 as D 4971 02 (2006).2For referenced ASTM standards, visit the ASTM website, w
15、ww.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 boldface numbers in parentheses refer to a list of references at the end ofthe standard.1*A Summary of Changes se
16、ction appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.terminology is modulus of deformation. If E is measured on anunloading linear segment, it is referred to as the recoverymodulus.5. Significance
17、and Use5.1 Results of this test method are used to predict displace-ments in rock mass caused by loads from a structure or fromunderground construction. It is one of several tests that shouldbe performed.5.2 Because the jack can apply directed loads, this testmethod can be performed to provide an es
18、timate of anisotropy.5.3 In theory, the analysis of test data is straight forward; themodulus estimate requires a record of applied hydraulicpressure versus borehole diameter change, and a knowledge ofthe rocks Poissons ratio. In practice, the above procedure,using the original theoretical formula,
19、frequently has resultedin computing a material modulus that was demonstrably toolow.5.4 For analyzing the test data it is assumed that the rockmass is linearly elastic, isotropic, and homogeneous. Withinthese assumptions, this test method can provide useful data forrock masses for which equivalent c
20、ontinuous properties can notbe found or estimated.NOTE 1Notwithstanding the statements on precision and bias con-tained in this test method; the precision of this test method is dependenton the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agenci
21、es that meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Users of this test method are cautioned that compliance withPractice D 3740 does not in itself assure reliable testing. Reliable testingdepends on many factors; Practice D 3740 provides a
22、means of evaluatingsome of those factors.6. Interferences6.1 It is assumed that the tensile and compressive moduli ofthe rock are equal and there is no tensile cracking induced inthe rock mass because of jack loading. If tensile cracks arecreated at 90 to the loading direction, it has been shown (1)
23、that the calculated modulus values can decrease by up to 29 %.Therefore, tensile cracking would result in a decrease in theslope of the loading curve and test data in the region ofdecreased slope should not be used.6.2 The volume of rock mass involved in the 76 mm (3.0in.) diameter jack test has bee
24、n estimated (2) to be about 0.15m3(5 ft3). This volume may not include enough discontinuitiesto be representative of the rock mass on a larger scale.6.3 Two aspects of jack behavior, discussed in 6.3.1 and6.3.2, require careful consideration in the analysis of test dataand can be compensated for by
25、the procedure outlined in thistest method and detailed by Heuze and Amadei (3).6.3.1 The platen/rock contact may not cover 90 of theborehole circumference, as assumed, because of radius mis-match between the jack and the hole (4, 5).6.3.2 In rock with modulus of deformation greater thanabout 7 GPa (
26、106psi), there is a longitudinal concave outwardbending of the jack platens that requires correction. Thiscorrection is necessary because the bending gives higherdisplacements at the ends than at the center of the loadingplatens and LVDT displacement gauges are located near theends of the platens.FI
27、G. 1 The 76-mm (3-in.) Borehole JackFIG. 2 Schematic of Loading of the Borehole JackD49710827. Apparatus7.1 Borehole JackThe borehole jack for which equationsand corrections are presented in Section 12 is the so-called“hard rock” jack, that is currently manufactured under patent.The manufacturers sp
28、ecifications are: range of travel is 13 mm(0.5 in.) from closed at 70 mm (2.75 in.) to fully open at 83 mm(3.25 in.), maximum pressure on borehole wall is 64 MPa(9300 psi), and deformation resolution is 0.025 mm (0.001 in.).The maximum jack pressure is achieved with a hydraulicsystem pressure of 69
29、MPa (10 000 psi). Deformation ismeasured by an LVDT at each end of the loading platens.These are referred to as the near and far LVDT respectively.7.2 Pressure GaugeAhydraulic gauge or electronic trans-ducer may be used to measure the hydraulic system pressure.The gauge shall have an accuracy of at
30、least 280 kPa (40 psi),including errors introduced by the readout equipment, and aresolution of at least 140 kPa (20 psi).7.3 Casing Alignment SystemThe borehole jack is at-tached to 73 mm (2.875 in.) BX drill casing and placed intoposition in the borehole. To determine the orientation of thejack, a
31、n orientation mark is transferred to successive sectionsof casing as they are added. To avoid introducing a systematicand progressive error into orientation, an alignment deviceshall be used to transfer the mark from one casing section toanother. In vertical boreholes, a plumb line may be sufficient
32、.In inclined or horizontal boreholes, a marking guide such as theone shown on Fig. 3 has been found satisfactory (6).8. Sampling, Test Specimens, and Test Units8.1 Number and Orientation of BoreholesThe number,spacing, and orientation of boreholes depend on the geometryof the project and the geology
33、 of the site.8.2 Rock Sampling:8.2.1 Each type of rock should be tested. In addition, areasof low modulus of deformation, such as fracture or alterationzones within a rock mass, are of particular interest and shouldbe tested.8.2.2 Tests should be conducted at different orientations tosample the anis
34、tropy of the rock mass, for example, paralleland perpendicular to the long axes of the columns in a basaltflow. Boreholes should generally be orthogonal to each otherand either parallel or perpendicular to the structure of the rockformation. At least ten tests in each rock material are recom-mended.
35、8.3 Boreholes ReamedIt is recommended that a reamingshell with a nominal outside diameter of 76 mm (3 in.) be used.It is further recommended that a bit fabricated to reaming shellgauge 76 mm (3 in.) also be used. This will minimize the radiusmismatch between the borehole and the jack. Accurate mea-s
36、urement of the diameter of the borehole is important.8.4 Boreholes CoredThe boreholes shall be drilled usingdiamond core techniques; continuous core should be obtained.Oriented cores are desirable but not mandatory.8.5 Core LoggedThe recovered core should be com-pletely logged, with emphasis on frac
37、tures and other mechani-cal inhomogeneties and water pressure. Rock quality designa-tion (RQD) should be calculated for each 1.5 m (5 ft) of holecored or core run, in accordance with Test Method D 6032.8.6 Test LocationWithin each borehole, locations for eachtest should be selected based on the core
38、 logs. In some casesobservation of the borehole with a borescope or boreholecamera (film or television) may be useful.9. Personnel and Equipment Requirements9.1 PersonnelAll personnel involved in performing thetest, including technicians and test supervisors, should be underthe guidance of someone t
39、horoughly familiar with the use ofthe jack. Sometimes the personnel may be required to beformally pre-qualified under a quality assurance (QA) proce-dures established as part of the overall testing program.9.2 Equipment Performance Verification The complianceof all equipment and apparatus with perfo
40、rmance specificationsof this procedure shall be verified. Performance verification isgenerally done by calibrating the equipment and measurementsystems according to established procedures.10. Calibration10.1 The borehole jack shall be calibrated before and at thecompletion of the program according t
41、o manufacturers orequivalent directions (7). In addition, the jack shall be cali-brated during the test program if the program consists of manytests or if the deformation readings become suspect. This isparticularly likely if the difference in the readings of near andfar LVDTs exceeds the manufactur
42、ers recommendation of 0.5mm (0.02 in.), indicating excessive misalignment of theplatens.10.2 Calibration of the boreholes jack must be documented.Personnel calibrating the equipment must be qualified inadvance.11. Procedure11.1 Test each distinctive rock material in a borehole.11.2 Testing Discontin
43、uitiesLocate tests in both intactzones and fractured zones to evaluate the effects of disconti-nuities. If the two LVDTs give significantly different displace-ment ($0.5 mm or 0.02 in.), discard the data and relocate thejack.11.3 BoreholesBoreholes shall be free from dirt and drillcuttings. Wash the
44、 borehole with clean water if necessary.11.4 Initial Seating PressureWhen the jack is at the testlocation and in the desired orientation, raise the hydraulicpressure to 350 kPa (50 psi) to seat the platens against theFIG. 3 Marking Guide on Section of CasingD4971083borehole wall. Use this pressure a
45、s the “zero” pressurethroughout the remainder of the test.11.5 Pressure LevelTest the rock to a pressure in excessof that required for full platen contact, but not exceeding thepressure or displacement capacity of the jack. Failure of therock may be recognized by an increase in the rate of deforma-t
46、ion without corresponding increase in the rate of pressure.11.6 Pressure CyclesIn at least 25 % of the tests in eachrock material, conduct multiple-pressure cycling to progres-sively higher loads to evaluate permanent deformation and theeffects of cycling on modulus. The peak pressure shall beapprox
47、imately 30, 60, and 100 % of the maximum. Duringeach cycle, vary the pressure in at least five equal incrementsand five decrements. At the end of each cycle, return thepressure to the initial seating pressure.11.7 Test at Various OrientationsIf tests are desired indifferent orientations, it is prefe
48、rable to move the jack at least30.5 cm (12 in.) below or above the previous test location so asto provide an undisturbed site for testing. It is suggested thatsuccessive orientations be perpendicular to each other. It isrecommended that the first test be conducted at the deepestlocation, and the fol
49、lowing tests be at successively shallowerdepths to prevent possible borehole damage in a given testfrom interfering with subsequent testing.11.8 Indications of Time-Dependent EffectsDeterminetime dependent deformation characteristics during the test bymaintaining the maximum test pressure for 15 min andrecording deformation at 5 min intervals. When the pressure isreduced to the initial seating pressure, take deformation read-ings again at 5 min intervals for 15 min. If at least three suchdeterminations are made in a given rock material, and th
