1、Designation: D 4395 08Standard Test Method forDetermining In Situ Modulus of Deformation of Rock MassUsing Flexible Plate Loading Method1This standard is issued under the fixed designation D 4395; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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 preparation, equipment, testprocedure, and data reduction for d
3、etermining in situ modulusof deformation of a rock mass using the flexible 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
4、 parallel or per-pendicular to the anticipated axis of thrust, as dictated by thedesign load.1.4 Time-dependent tests not covered by this standard canbe performed but are to be reported in another standard.1.5 All observed and calculated values shall conform to theguidelines for significant digits a
5、nd rounding established inPractice D 6026.1.5.1 The method used to specifiy 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
6、 is beyond its scope.1.6 The values stated 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 furtherinfo
7、rmation on this test method.1.8 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 determine the applica-bility of regulatory limitations
8、prior to use. For specificprecaution statements, 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 3740 Practice for Minimum Requirements for Agencies
9、Engaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD 4394 Test Method for Determining the In Situ Modulusof Deformation of Rock Mass Using the Rigid PlateLoading MethodD 4403 Practice for Extensometers Used in RockD 4879 Guide for Geotechnical Mapping
10、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 for Using Significant Digits in Geotechni-cal DataD 6032 Test Method for Determining Rock Quality Desig-na
11、tion (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 plate, mortar pad, orrock in response to and in the same direction as the appliedload.3.2.2 flexible plateth
12、eoretically, a plate having no stiff-ness.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 July 2008. Originally approvedin 1984. Last previous e
13、dition approved in 2004 as D 4395 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 s
14、ection appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3 loadtotal force acting on the rock face.3.2.4 peak-to-peak modulus of deformationthe slope ofstress - strain curve line connecting the pe
15、aks of the curvesobtained from successive pressure cycles (see Fig. 1).3.2.5 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 calculationswhere unloading conditions exist. The difference bet
16、ween thetangent and recovery moduli indicates the materials capacityof hysteresis or energy dissipation capabilities (see Fig. 2).3.2.6 secant modulus of deformationthe slope of thestress - strain curve between zero stress and any specifiedstress. This modulus should be used for complete load stepsf
17、rom zero to the desired load (see Fig. 2).3.2.7 tangent modulus of deformationthe slope of thestress - strain curve obtained over the segment of the loadingcurve judged as the most representative of elastic response bythe investigator. It neglects the end effects of the curve and isbetter suited to
18、small stress changes. The ratio between thesecant modulus and the tangent modulus can be used as ameans of measuring the stress 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 hydraulic loading system
19、 consisting of flatjacks,reaction members, and associated hardware is constructedbetween the two faces and a mortar pad is placed on each face.4.3 If deflection is to be measured within the rock mass,install extensometer instruments in the rock in accordance withPractice D 4403.4.4 The two faces are
20、 loaded and unloaded incrementallyand the deformations of the rock mass at the surfaces and, ifdesired, within the rock, are measured after each increment.The modulus of deformation is then calculated.5. Significance and Use5.1 Results of this type of test method are used to predictdisplacements in
21、rock mass caused by loads from a structure orfrom underground construction. It is one of several tests thatshould be performed. The resulting in situ 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 uniforml
22、y distributed load (uniform stress) over a circulararea acting on a semi-infinite elastic medium.5.3 This test method is normally performed at ambienttemperature, but equipment can be modified or substituted foroperations at other temperatures.NOTE 1The quality of the result produced by this standar
23、d isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection, etc. Users of this standard arecautioned
24、that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 3740provides a means of evaluating some of those factors.6. Interferences6.1 The rock under the loaded area is generally not homo-geneous, as assumed in theory. Rock wi
25、ll respond to the loadaccording to its local deformational characteristics. 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 t
26、he rock mass. The use of the averageplate deflection will mitigate this problem.6.2 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.
27、First, the rockmass is tested at very low stress levels unless the measurementpoints are very close to the rock surface and because of this, thesame problems as with surface measurements occur. Tests atlow stress levels may give unrealistic modulus values becausemicrofractures, joints, and other dis
28、continuities in the rock areopen. Secondly, the disturbance caused by implanting thedeflection transducer in the rock mass is difficult to evaluate.The techniques in this test method are designed to produceFIG. 1 Rock Surface Deformation as a Function of BearingPressureFIG. 2 Relationship Between Ta
29、ngent, Secant, and RecoveryModuliD4395082minimal disturbance. Thirdly, in rocks with very high modulus,the accuracy of the instruments may be insufficient to providereliable results.6.3 Time-rate of loading has negligible influence on themodulus.6.4 Calculations neglect the stress history of the roc
30、k.6.5 This test method is insensitive to Poissons ratio, whichmust be assumed or obtained from laboratory 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 defor
31、mation,applying and restraining test loads, recording test data, andtransporting various components to the test site.7.2 Test Site Preparation Equipment This should includean assortment of excavation tools, such as drills and chippinghammers. Blasting should not be allowed during final prepa-ration
32、of the test site. The drill for the instrumentation holesshould, if possible, have the capability of retrieving cores fromdepths of at least 30 ft (10 m).7.3 Borehole Viewing DeviceSome type of device isdesirable for examination of the instrumentation holes tocompare and verify geologic features obs
33、erved in the core ifcore recovery is poor or if it is not feasible to retrieve orientedcores.7.4 Deformation Measuring Instruments Instruments formeasuring deformations should include a reliable multipleposition borehole extensometer (MPBX) for each instrumen-tation hole and a tunnel diameter gauge.
34、 For surface measure-ments, dial gages, or linear variable differential transformers(LVDTs) are generally used. An accuracy of at least6 0.0001in. (0.0025 mm), including the error of the readout equipment,and a sensitivity of at least 0.00005 in. (0.0013 mm) isrecommended. Errors in excess of 0.0004
35、 in. (0.01 mm) caninvalidate test results when the modulus of rock 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. Flatjacks at eac
36、h rock face should be used to apply theload and should have sufficient range to allow for deflection ofthe rock and maintain pressure to within 3 %. They should beconstructed so that the two main plates move apart in a parallelmanner over the usable portion of the range. A sphericalbearing of suitab
37、le capacity should be incorporated in thereaction members.7.6 Load Measuring InstrumentsA pressure gauge/transducer or load cell should be used to measure the pressurein the flatjacks. The pressure gauge or transducer should havean accuracy of at least 620 psi (0.14 MPa), including errorintroduced b
38、y readout equipment, and a sensitivity of at least10 psi (0.069 MPa). The load cell should have an accuracy ofat least 61000 lbf (4.4 kN) including errors introduced by thereadout system, and a sensitivity of at least 500 lbf (2.22 kN)is recommended.7.7 Bearing PadsThe bearing pad material shall hav
39、e amodulus no greater than the modulus of the rock being tested,as determined from an intact sample. Generally, a neat cementgrout is satisfactory if the curing time does not exceed severaldays. Fly ash or other suitable materials may be added toreduce the stiffness, if necessary.8. Safety Precautio
40、ns8.1 All personnel involved in performing the test should beformally pre-qualified in accordance with the quality assuranceprocedures of Annex A1.8.2 Verify the compliance of all equipment and apparatuswith the performance specifications in Section 7. If no require-ments are stated, the manufacture
41、rs specifications for theequipment may be appropriate as a guide, but care must betaken for sufficient performance. Performance verification isgenerally done by calibrating the equipment and measurementsystem. Accomplish calibration and documentation in accor-dance with Annex A1.8.3 Enforce safety b
42、y applicable safety standards. Pressurelines must 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 flatjack.9. In Situ ConditionsNOTE 2The g
43、uidelines presented in this section 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 massselecti
44、ng areas that are geologically representative of the mass.Test those portions of the rock mass with features such asfaults, fracture zones, cavities, inclusions, and the like toevaluate their affects. Design the testing program so that affectsof local geology can be clearly distinguished.9.2 The siz
45、e of the plate will be determined by 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. Optimum adit dimensions are approximatelysix times the plate diameter; recommended plate diameter iscommonly 112 t
46、o 314 ft (0.5 to 1 m). Other sizes are useddepending upon site specifics.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 parallelperpendicular to the long axes of columns in a b
47、asalt flow.9.4 Tests should 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 plate andthe applied load. Larger plates and higher loa
48、ds measure theresponse of rock further away from the test adit. Thus, if therock 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 adequ
49、ate. If theundisturbed in situ modulus is desired, larger diameter platesand higher loads may be used, although practical consider-ations often limit the size of the equipment. Alternatively,careful excavation procedures, such as presplitting or othertypes of smooth-wall blasting, may be employed in the testD4395083area to limit damage to the rock and the resulting need forlarger plates and loads.9.5 Cores, if any, should be logged and tested for rockquality designation (RQD), fracture spacing, strength, anddeformation in accordance with Guide D 5434 and TestMeth
