1、Designation: D4971 08D4971 16Standard 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 D4971; the number immediately following the designation indicates the year oforiginal adop
2、tion or, 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 situ modulus of a rock mas
3、s at various depths and orientations. Informationon time-dependent deformation may also be obtained.1.2 This test method covers testing in an N size drill hole and is more relevant to a borehole jack device designed for “hard rock”than for soft rock.1.3 All observed and calculated values shall confo
4、rm to the guidelines for significant digits and rounding established in PracticeD6026.1.3.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to theaccuracy to which the data can be applied in design or other uses, or both. How one ap
5、plies the results obtained using this standardis beyond its scope.1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for information only and are not considered standard.1.5 This stan
6、dard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 AST
7、M Standards:2D653 Terminology Relating to Soil, Rock, and Contained FluidsD3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD6026 Practice for Using Significant Digits in Geotechnical DataD6032 Test
8、 Method for Determining Rock Quality Designation (RQD) of Rock Core3. Terminology3.1 See Terminology D653 for general definitions.3.1 Definitions:3.1.1 For definitions of common technical terms in this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 defor
9、mationdeformation, nchange in shape or size, (see Terminology D653). In this test method deformation is thechange in the diameter of the borehole.3.2.2 modulus of deformationdeformation, nratio of stress to strain for a material under given loading conditions;numerically equal to the slope of the ta
10、ngent or the secant of the stress-strain curve. The use of the term modulus of elasticity isrecommended for materials that deform in accordance with Hookes law, and the term modulus of deformation is recommendedfor materials that deform otherwise, (see Terminology D653). In this test method, the mod
11、ulus of deformation is calculated fromthe applied fluid pressure, the relative change in hole diameter, a function of Poissons ratio, and a constant.1 This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.12 on Rock Mec
12、hanics.Current edition approved July 1, 2008Dec. 1, 2016. Published July 2008January 2017. Originally approved in 1989. Last previous edition approved in 20062008 asD4971 02D4971 08. (2006). DOI: 10.1520/D4971-08.10.1520/D4971-16.2 For referencedASTM standards, visit theASTM website, www.astm.org, o
13、r contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes ha
14、ve been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official do
15、cument.*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 States13.2.2.1 DiscussionThe use of the term modulus of elasticity is recommended for materials that deform in accordance
16、 with Hookes law, and the termmodulus of deformation is recommended for materials that deform otherwise, (see Terminology D653). In this test method, themodulus of deformation is calculated from the applied fluid pressure, the relative change in hole diameter, a function of Poissonsratio, and a cons
17、tant.3.2.3 jack effciencyeffciency, nratio of the jack plate pressure to the applied hydraulic pressure.3.2.4 hard rock borehole jack, nthis refers to a specific borehole jack by the manufacture that has platens designed for harderrocks, goes to higher pressures than a soft rock borehole jack and wh
18、ose displacement range is not exceeded at the maximumallowable pressure for the borehole jack.4. Summary of Test Method4.1 The drill logs for a drill hole hole to be tested are examined. Specific depths and orientations in the drill hole are selectedbased upon the objectives of the test program.4.2
19、The 76 mm (3.0borehole jack in the fully retracted position is positioned at each location selected in the drill hole for thetest program. The 76 mm (3 in.) jacks, (see Fig. 1 and Fig. 2), induce undirectionalunidirectional pressure to the walls of a boreholeby means of two opposed curved steel plat
20、ens each covering a 90 sector, over a length of 20.3 cm (8 in.).20 cm (8 in.) and pressureFIG. 1 The 76-mm (3-in.) Borehole JackJack: Assemble (a) and Disassembled (b)D4971 162versus deformation data is collected. Testing is usually done from the deepest test zone in the drill hole and then tested a
21、tsubsequent shallower test intervals to minimize risks to the borehole jack.4.3 Raw data from a test consist of hydraulic-line pressure, Qh, versus readout from linear variable differential transformers(LVDTs) measuring platen movement. Knowing the displacement calibration of the LVDTs, the raw data
22、 can be transformed toa test record of hydraulic pressure versus hole diameter, D. For each increment of pressure, Qh, and hole deformation, D,theoretical data analysis (1),3 assuming rigid jack plates and full 90 contact, give the theoretical rock mass modulus, E (Etheoretical)as a function E = f (
23、 QhD T*), where T* is a coefficient dependent upon Poissons ratio. If E is measured on a linear segmentof the loading curve, common terminology is modulus of deformation. If E is measured on an unloading linear segment, it isreferred to as the recovery modulus.5. Significance and Use5.1 Results of t
24、his test method are used to predict displacements in rock mass caused by loads from a structure or fromunderground construction. construction for the load range that the device can apply. It is one of several tests that should beperformed.5.2 Because the jack can apply directed loads, this test meth
25、od can be performed to provide an estimate of anisotropy.5.3 In theory, the analysis of test data is straight forward; the modulus estimate requires a record of applied hydraulic pressureversus borehole diameter change, and a knowledge of the rocks Poissons ratio. In practice, the above procedure, u
26、sing the originaltheoretical formula, frequently has resulted in computing a material modulus that was demonstrably too low.5.4 For analyzing the test data it is assumed that the rock mass is linearly elastic, isotropic, and homogeneous. Within theseassumptions, this test method can provide useful d
27、ata for rock masses for which equivalent continuous properties can not cannotbe found or estimated.NOTE 1Notwithstanding the statements on precision and bias contained in this test method; the precision of this test method is dependent on thecompetence of the personnel performing it, and the suitabi
28、lity of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 aregenerally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D3740 does notin itself assure reliable testing. Reliable testing dep
29、ends on many factors; Practice D3740 provides a means of evaluating some of those factors.6. Interferences6.1 It is assumed that the tensile and compressive moduli of the rock are equal and there is no tensile cracking induced in therock mass because of jack loading. If tensile cracks are created at
30、 90 to the loading direction, it has been shown (1) that thecalculated modulus values can decrease by up to 29 %. Therefore, tensile cracking would result in a decrease in the slope of theloading curve and test data in the region of decreased slope should not be used.6.2 The volume of rock mass invo
31、lved in the 76 mm (3.0 in.) diameter jack test has been estimated (2) to be about 0.15 m3 (5ft3). This volume may not include enough discontinuities to be representative of the rock mass on a larger scale.6.3 Two aspects of jack behavior, discussed in 6.3.1 and 6.3.2, require careful consideration i
32、n the analysis of test data and canbe compensated for by the procedure outlined in this test method and detailed by Heuze and Amadei (3).6.3.1 The platen/rock contact may not cover 90 of the borehole circumference, as assumed, because of radius mismatchbetween the jack platens and the interior wall
33、of the drill hole (4, 5).3 The boldface numbers in parentheses refer to a list of references at the end of the standard.FIG. 2 Schematic of Diametrical Loading of the Borehole JackWall by the Borehole Jack PlatensD4971 1636.3.2 In rock with modulus of deformation greater than about 7 GPa (106 psi),
34、there is a longitudinal concave outward bendingof the jack platens that requires correction. This correction is necessary because the bending gives higher displacements at the endsthan at the center of the loading platens and LVDTthe displacement gauges are located near the ends of the platens.6.4 A
35、ny effects on the data from the in situ stress field around the borehole wall may need to be considered.7. Apparatus7.1 Borehole JackThe borehole jack (Fig. 1) for which equations and corrections are presented in Section 12 is the so-called“hard rock” jack, that is currently manufactured under paten
36、t. a patent. A hydraulic hose and electrical cable extending from theborehole jack up the borehole to the surface and is connected to a readout unit or units for reading displacement and to hydraulicpressure system that is used to apply and measure the hydraulic pressure applied to the jack. The man
37、ufacturers specifications are:range of travel is 1310 mm (0.5 in.) from closed at 70 mm (2.75 in.) to fully open at 8380 mm (3.25 in.), maximum pressure onborehole wall is 64 MPa (9300 psi), and deformation resolution is 0.025 mm (0.001 in.). The maximum jack pressure is achievedwith a hydraulic sys
38、tem pressure of 69 MPa (10 000 psi). Deformation is measured by an LVDT at each end of the loading platens.These are referred to as the near and far LVDT respectively.7.2 Pressure GaugeA hydraulic gauge or electronic transducer may be used to measure the hydraulic system pressure.pressure to the pla
39、tens. The gauge or transducer shall have an accuracy of at least 280 kPa (40 psi), including errors introducedby the readout equipment, and a resolution of at least 140 kPa (20 psi) and a range of at least 69 MPa (10 000 psi).7.3 Displacement RecorderAn electronic readout box is used to record the d
40、isplacement measured by each LVDT associatedwith the platens. The readout boxes used shall have an accuracy of at least 0.025 mm (0.001 in.) and able to read a range of travelof 10 mm (0.5 in.) from closed at 70 mm (2.75 in.) to full open at 80 mm (3.25 in.).NOTE 2A more sophisticated data acquisiti
41、on system may be used than what is discussed in 7.2 and 7.3. The data acquisition equipment mentionedis sufficient and is usually more robust in the field; especially in more hostile and remote field conditions than it high be for a more sophisticated system.7.4 Casing Alignment SystemThe borehole j
42、ack is attached to 73 mm (2.875 in.) BX drill casing and placed into position inthe borehole. To determine the orientation of the jack, an orientation mark is transferred to successive sections of casing as theyare added. To avoid introducing a systematic and progressive error into orientation, an a
43、lignment device shall be used to transferthe mark from one casing section to another. In vertical boreholes, a plumb line may be sufficient. In inclined or horizontalboreholes, a marking guide such as the one shown on Fig. 3 has been found satisfactory (6).8. Sampling, Test Specimens, and Test Units
44、8.1 Number and Orientation of BoreholesThe number, spacing, and orientation of boreholes depend on the geometry of theproject and the geology of the site.8.2 Rock Sampling:8.2.1 Each type of rock should be tested. In addition, areas of low modulus of deformation, such as fracture or alteration zones
45、within a rock mass, are of particular interest and should be tested.8.2.2 Tests should be conducted at different orientations to sample the anistropy of the rock mass, for example, parallel andperpendicular to the long axes of the columns in a basalt flow. Boreholes should generally be orthogonal to
46、 each other and eitherparallel or perpendicular to the structure of the rock formation. At least ten tests in each rock material are recommended.8.3 Boreholes ReamedIt is recommended that a reaming shell with a nominal outside diameter of 76 mm (3 in.) be used. Itis further recommended that a bit fa
47、bricated to reaming shell gauge 76 mm (3 in.) also be used. This will minimize the radiusmismatch between the borehole and the jack. Accurate measurement of the diameter of the borehole is important.FIG. 3 Marking Guide on Section of CasingD4971 1648.4 Boreholes CoredThe boreholes shall be drilled u
48、sing diamond core techniques; continuous core should be obtained.Oriented cores are desirable but not mandatory.8.5 Core LoggedThe recovered core should be completely logged, with emphasis on fractures and other mechanicalinhomogeneties and water pressure. Rock quality designation (RQD) should be ca
49、lculated for each 1.5 m (5 ft) of hole cored orcore run, in accordance with Test Method D6032.8.6 Test LocationWithin each borehole, locations for each test should be selected based on the core logs. In some casesobservation of the borehole with a borescope or borehole camera (film or television) may be useful.9. Personnel and Equipment Requirements9.1 PersonnelAll personnel involved in performing the test, including technicians and test supervisors, should be under theguidance of someone thoroughly familiar with the use of the jack.
