1、Designation: D 4394 08Standard Test Method forDetermining In Situ Modulus of Deformation of Rock MassUsing Rigid Plate Loading Method1This standard is issued under the fixed designation D 4394; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 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 preparation, equipment, testprocedure, and data reduction for dete
3、rmining in situ modulusof deformation of a rock mass using the rigid plate loadingmethod.1.2 This test method is designed to be conducted in an aditor small underground chamber; however, with suitable modi-fications it could be conducted at the surface.1.3 This test method is usually conducted paral
4、lel or per-pendicular to the anticipated axis of thrust, as dictated by thedesign load.1.4 Time dependent tests can be performed but are to bereported in another standard.1.5 Observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 60
5、26.1.5.1 The method used to specify how data are collected,calculated, or 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.1.6 The values stat
6、ed in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.7 The references appended to this standard contain furtherinformation on this test method.1.8 This sta
7、ndard 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 determine the applica-bility of regulatory requirements prior to use. For specificprecaution st
8、atements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD2113 Practice for Rock Core Drilling and Sampling ofRock for Site InvestigationD 4395 Test Method for Determining In Situ Modulus ofDeformation of Rock Mass Using Flexible
9、 Plate LoadingMethodD 4403 Practice for Extensometers Used in RockD 4879 Guide for Geotechnical Mapping of Large Under-ground Openings in RockD 5079 Practices for Preserving and Transporting RockCore SamplesD 5434 Guide for Field Logging of Subsurface Explora-tions of Soil and RockD 6026 Practice fo
10、r Using Significant Digits in Geotechni-cal DataD 6032 Test Method for Determining Rock Quality Desig-nation (RQD) of Rock Core3. Terminology3.1 For terminology used in this test method, refer toTerminology, D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 deflectionmovement of the rig
11、id plate, mortar pad,or rock in response to and in the same direction as the appliedload.3.2.2 loadtotal force acting on the rock face.3.2.3 peak-to-peak modulus of deformationthe slope ofthe stress - strain curve line connecting the peaks of the curvesobtained from successive pressure cycles (see F
12、ig. 1).1This test method is under the jurisdiction 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 August 2008. Originallyapproved in 1984. Last previous edition approved in 2004 as D 4394
13、 04.2For referenced ASTM standards, 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.1*A Summary of Changes section appears at the end of this
14、 standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.4 recovery modulus of deformationthe tangent modu-lus of the unloading stress - strain curve. This modulus isusually higher than the other moduli and is used in calculation
15、swhere unloading conditions exist. The difference between thetangent and recovery moduli indicates that materials capacityof hysteresis or energy dissipation capabilities (see Fig. 2).3.2.5 rigid plateplate with deflection of less than 0.0001in. (0.0025 mm) from center to edge of plate, when maximum
16、load is applied.3.2.6 secant modulus of deformationthe slope of thestress-strain curve between zero stress and a specified stress.This modulus should be used for the load steps from zero to thedesired load (see Fig. 2).3.2.7 tangent modulus of deformationthe slope of thestress - strain curve obtaine
17、d over the segment of the loadingcurve judged by the investigator as the most representative ofelastic response. It neglects the end effects of the curve and isbetter suited to small stress changes. The ratio between thesecant modulus and the tangent modulus can be used as ameans of measuring the st
18、ress damage of the material (see Fig.2).4. Summary of Test Method4.1 Areas on two opposing parallel faces of a test adit areflattened and smoothed.4.2 A mortar pad and rigid metal plate are installed againsteach face and a hydraulic loading system is placed between therigid plates.4.3 If deflection
19、is to be measured within the rock mass,extensometer instruments shall be installed in the rock inaccordance with Practice D 4403.4.4 The two faces are loaded and unloaded incrementallyand the deformations of the rock mass at the surfaces and, ifdesired, within the rock, are measured after each incre
20、ment.The modulus of deformation is then calculated.5. Significance and Use5.1 Results of this type of test method are used to predictdisplacements in rock mass caused by loads from a structure orfrom underground construction. It is one of several tests thatshould be performed. The resulting in situ
21、modulus is com-monly less than the elastic modulus determined in the labora-tory.5.2 The modulus is determined using an elastic solution fora uniformly distributed load (uniform stress) over a circulararea acting on a semi-infinite elastic medium that produces aconstant normal displacement of the lo
22、aded surface area of themedium.5.3 This test method is normally performed at ambienttemperature, but equipment can be modified or substituted foroperations at other temperatures.6. Interferences6.1 An inflexible plate used to load the rock face is difficultto construct. However, if the plate is cons
23、tructed as rigid aspracticable, the rock face is smoothed, and a thin, high-modulus material is used for the pad, the error is minimal.6.2 The rock under the loaded area is generally not homo-geneous, as assumed in theory. Rock will respond to the loadaccording to its local deformational characteris
24、tics. Therefore,deflection measurements at discrete points on the rock surfacetend to be heavily influenced by the deformational character-istics of the rock mass at that location and may give results thatare unrepresentative of the rock mass. The use of the averageplate deflection will mitigate thi
25、s problem.6.3 Measurement of the deflection within the rock mass canutilize a finite gauge length to reflect the average rock massdeformation properties between the measuring points. Thisapproach entails three drawbacks, however. First, the rockmass is tested at very low stress levels unless the mea
26、surementpoints are very close to the rock surface, and because of this,the same problems as with surface measurements occur. Testsat low stress levels may give unrealistically low modulusvalues because microfractures, joints, and other discontinuitiesin the rock are open. Secondly, the disturbance c
27、aused byimplanting the deflection transducer in the rock mass is difficultto evaluate. The techniques in this test method are designed toproduce minimal disturbance. Thirdly, in rocks with very highmodulus, the accuracy of the instruments may be insufficient toprovide reliable results.FIG. 1 Rock Su
28、rface Deformation as a Function of BearingPressureFIG. 2 Relationship Between Tangent, Secant and RecoveryModuliD43940826.4 Time-rate of loading has negligible influence on themodulus.6.5 Calculations neglect the stress history of the rock.6.6 This test method is insensitive to Poissons ratio.6.7 Po
29、issons ratio should be assumed or obtained fromlaboratory testing.7. Apparatus7.1 Equipment necessary for accomplishing this test methodincludes items for: preparing the test site, drilling and loggingthe instrumentation holes, measuring the rock deformation,applying and restraining test loads, reco
30、rding test data, andtransporting various components to the test site.7.2 Test Site Preparation Equipment This shall include anassortment of excavation tools, such as drills and chippinghammers. Blasting shall not be allowed during a preparation ofthe test site. The drill for the instrumentation hole
31、s shall, ifpracticable, have the capability of retrieving cores from depthsof about 30 ft (10 m).7.3 Borehole Viewing DeviceSome type of device isdesirable for observation of the instrumentation holes tocompare and verify geologic features observed in the core ifcore recovery is poor or if it is not
32、 feasible to retrieve orientedcores.7.4 Deformation Measuring Instruments Instruments formeasuring deformations shall include a reliable multiple-position borehole extensometer (MPBX) for each instrumen-tation hole and a tunnel diameter gauge. For surface measure-ments, dial gages or linear variable
33、 differential transformers(LVDTs) are generally used. An accuracy of 60.0001 in.(0.0025 mm), including the error of the readout equipment, anda sensitivity of at least 0.00005 in. (0.0013 mm) is recom-mended. Errors in excess of 0.0004 in. (0.01 mm) caninvalidate test results when the modulus of roc
34、k mass exceeds5 3 106psi (3.5 3 104MPa).7.5 Loading EquipmentThe loading equipment includesthe device for applying the load and the reaction members(usually thick-walled aluminum or steel pipes) which transmitthe load. Hydraulic rams or flatjacks are usually used to applythe load hydraulically with
35、sufficient capability and volume toapply and maintain desired pressures to within 3 %. If flatjacksare used they should have sufficient range to allow fordeflection of the rock and should be constructed so that the twomain plates move apart in a parallel manner over the usableportion of the loading
36、range. A spherical bearing of suitablecapacity should be coupled to one of the bearing plates.7.6 Load Cells and TransducersA load cell is recom-mended to measure the load on the bearing plate. An accuracyof around 61000 lbf (64.4 kN), including errors introduced bythe readout system, and a sensitiv
37、ity of 500 lbf (2.2 kN) arerecommended. Alternatively, a pressure gauge or transducermay be used to monitor hydraulic pressure for calculation ofload, provided the device can measure the load to the samespecifications as the load cell. An accuracy of 620 psi (60.14MPa), including error introduced by
38、 readout equipment, and asensitivity of 10 psi (0.069 MPa). If a hydraulic ram is used,the effects of ram friction shall be determined. If flatjacks areused, care shall be taken that the jacks do not operate at theupper end of their range.7.7 Bearing PadsThe bearing pads shall have a modulusof elast
39、icity of around 4 3 106psi (3 3 104MPa) and shall becapable of conforming to the rock surface and bearing plate.High-early strength grout or molten sulfur bearing pads arerecommended.7.8 Bearing PlatesThe bearing plates shall approximate arigid die as closely as practical. A bearing plate that has b
40、eenfound satisfactory is shown on Fig. 3. Although the exactdesign and materials may differ, the stiffness of the bearingplate shall be the minimum stiffness necessary to not producemeasurable deflection of the plate under maximum load.8. Safety Hazards8.1 Personnel involved in performing the test s
41、hall beformally prequalified under the quality assurance procedureslisted in Annex A1.8.2 Verify the compliance of equipment and apparatus withthe performance specifications in Section 7. If requirements arenot stated, the manufacturers specifications for the equipmentmay be appropriate as a guide,
42、however, care should be takenfor sufficient performance. Performance verification is gener-ally done by calibrating the equipment and measurementsystem. Accomplish calibration and documentation in accor-dance with the quality assurance procedures.8.3 Enforce safety by applicable safety standards. Pr
43、essurelines should be bled of air to preclude violent failure of thepressure system. Total deformation should not exceed theexpansion capabilities of the flatjacks; normally this is approxi-mately 3 % of the diameter of a metal jack.9. In-Situ ConditionsNOTE 1The guidelines presented in this section
44、 are the domain of theagency or organization requesting the testing and are intended to facilitatedefinition of the scope and development of site-specific requirements forthe testing program as a whole.9.1 Test each structurally distinctive zone of rock massselecting areas that are geologically repr
45、esentative of the mass.Test those portions of the rock mass with features such asfaults, fracture zones, cavities, inclusions, and the like toevaluate their effects. Design the testing program so that effectsof local geology can be clearly distinguished.9.2 The size of the plate will be determined b
46、y localgeology, pressures to be applied, and the size of the adit to betested. These parameters should be considered prior to exca-vation of the adit. Acceptable adit dimensions are approxi-mately six times the plate diameter; recommended platediameter is commonly 112 to 314 ft (0.5 to 1 m). Other s
47、izes areused depending upon site specifics. A map of the adit and testsite shall be prepared in accordance with Guide D 4879.9.3 The effects of anisotropy should be investigated byappropriately oriented tests: for example, parallel and perpen-dicular to the bedding of a sedimentary sequence, or para
48、lleland perpendicular to the long axes of columns in a basalt flow.9.4 Tests shall be performed at a site not affected bystructural changes resulting from excavations of the adit. Thezone of rock that contributes to the measured deflection duringthe plate loading test depends on the diameter of the
49、plate andthe applied load. Larger plates and higher loads measure theresponse of rock further away from the test adit. Thus, if theD4394083rock around the adit is damaged by the excavation process, andthe deformational properties of the damaged zone are theprimary objective of the test program, small-diameter platetests on typically excavated surfaces are adequate. If the intactin-situ modulus is desired, larger diameter plates and higherloads may be used, although practical considerations oftenlimit the size of the equipment. Alternatively, careful excava-tion
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