1、Designation: D 4395 04Standard Test Method forDetermining the In Situ Modulus of Deformation of RockMass Using the 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
2、the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the preparation, equipment, testprocedure, and data reduct
3、ion for determining 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
4、conducted 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
5、 digits and 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 thi
6、sstandard is beyond its scope.1.6 The values stated in inch-pound units are to be regardedas the standard.1.7 The references appended to this standard contain furtherinformation on this test method.1.8 This standard does not purport to address all of thesafety concerns, if any, associated with its u
7、se. 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 prior to use. For specificprecaution statements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relati
8、ng to Soil, Rock and ContainedFluidsD 2113 Practice for Diamond Core Drilling for Site Inves-tigationD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4394 Test Method for Determining In Situ
9、Modulus ofDeformation of Rock Mass Using the Rigid 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 SampleD 5434 Guide for Field Logging of Subsurface
10、 Explora-tions of Soil and RockD 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 For terminology used in this test method, refer toTerminology D 653.3.2 Definitions of Terms Specific to T
11、his 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 platetheoretically, a plate having no stiff-ness.3.2.3 loadtotal force acting on the rock face.1This test method is under the jurisdiction of ASTM Committ
12、ee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved Jan. 1, 2004. Published February 2004. Originallyapproved in 1984. Last previous edition approved in 1998 as D 4395 84 (1998).2For referenced ASTM standards, visit the ASTM websi
13、te, 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 standard.Copyright ASTM International, 100 Barr Harbor
14、Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.4 peak-to-peak modulus of deformationthe slope ofstress - strain curve line connecting the peaks of the curvesobtained from successive pressure cycles (see Fig. 1).3.2.5 recovery modulus of deformationthe tangent modu-lus of the
15、 unloading stress - strain curve. This modulus isusually higher than the other moduli and is used in calculationswhere unloading conditions exist. The difference between thetangent and recovery moduli indicates the materials capacityof hysteresis or energy dissipation capabilities (see Fig. 2).3.2.6
16、 secant modulus of deformationthe slope of thestress - strain curve between zero stress and any specifiedstress. This modulus should be used for complete load stepsfrom zero to the desired load (see Fig. 2).3.2.7 tangent modulus of deformationthe slope of thestress - strain curve obtained over the s
17、egment 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 small stress changes. The ratio between thesecant modulus and the tangent modulus can be used as ameans of measuring the stress damage
18、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 consisting of flatjacks,reaction members, and associated hardware is constructedbetween the two faces and a mortar pad is placed on ea
19、ch 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 loaded and unloaded incrementallyand the deformations of the rock mass at the surfaces and, ifdesired, within the rock, are measured a
20、fter 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 rock mass caused by loads from a structure orfrom underground construction. It is one of several tests thatshould be performed. The res
21、ulting 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 uniformly distributed load (uniform stress) over a circulararea acting on a semi-infinite elastic medium.5.3 This test method is normally perfo
22、rmed at ambienttemperature, but equipment can be modified or substituted foroperations at other temperatures.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that
23、meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection, etc. Users of this standard arecautioned that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 374
24、0provides 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 will respond to the loadaccording to its local deformational characteristics. Therefore,deflection measurements at discrete points on the
25、 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 this problem.6.2 Measurement of the deflection within the rock mass
26、canutilize a finite gage 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 measurementpoints are very close to the rock surface and because of t
27、his, thesame problems as with surface measurements occur. Tests atlow stress levels may give unrealistical modulus values be-cause microfractures, joints, and other discontinuities in therock are open. Secondly, the disturbance caused by implantingthe deflection transducer in the rock mass is diffic
28、ult toevaluate. 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 Surface Deformation as a Function of BearingPressureFIG. 2 Relationship B
29、etween Tangent, Secant, and RecoveryModuliD43950426.3 Time-rate of loading has negligible influence on themodulus.6.4 Calculations neglect the stress history of the rock.6.5 This test method is insensitive to Poissons ratio, whichmust be assumed or obtained from laboratory testing.7. Apparatus7.1 Eq
30、uipment 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, recording test data, andtransporting various components to the test site.7.2 Test Site P
31、reparation Equipment This should includean assortment of excavation tools, such as drills and chippinghammers. Blasting should not be allowed during final prepa-ration of the test site. The drill for the instrumentation holesshould, if possible, have the capability of retrieving cores fromdepths of
32、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 observed in the core ifcore recovery is poor or if it is not feasible to retrieve orientedcores.7.4 Deformation Measuring Instruments I
33、nstruments formeasuring deformations should include a reliable multipleposition borehole extensometer (MPBX) for each instrumen-tation hole and a tunnel diameter gage. For surface measure-ments, dial gages, or linear variable differential transformers(LVDTs) are generally used. An accuracy of at lea
34、st6 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 in. (0.01 mm) caninvalidate test results when the modulus of rock mass exceeds5 3 106psi (3.5 3 104MPa).7.5 Loading EquipmentThe loa
35、ding equipment includesthe device for applying the load and the reaction members(usually thick-walled aluminum or steel pipes) which transmitthe load. Flatjacks at each rock face should be used to apply theload and should have sufficient range to allow for deflection ofthe rock and maintain pressure
36、 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 suitable capacity should be incorporated in thereaction members.7.6 Load Measuring InstrumentsA pressure gage/transducer or load cell shoul
37、d be used to measure the pressurein the flatjacks. The pressure gage or transducer should have anaccuracy of at least 620 psi (0.14 MPa), including errorintroduced by 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 k
38、N) 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 have amodulus no greater than the modulus of the rock being tested,as determined from an intact sample. Generally, a neat cementgrout is s
39、atisfactory if the curing time does not exceed severaldays. Fly ash or other suitable materials may be added toreduce the stiffness, if necessary.8. Safety Precautions8.1 All personnel involved in performing the test should beformally pre-qualified in accordance with the quality assuranceprocedures
40、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 manufacturers specifications for theequipment may be appropriate as a guide, but care must betaken for sufficient performance. Performance verific
41、ation isgenerally done by calibrating the equipment and measurementsystem. Accomplish calibration and documentation in accor-dance with Annex A1.8.3 Enforce safety by applicable safety standards. Pressurelines must be bled of air to preclude violent failure of thepressure system. Total deformation s
42、hould 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 guidelines presented in this section are the domain of theagency or organization requesting the testing and are intended to facilitatede
43、finition 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 representative of the mass.Test those portions of the rock mass with features such asfaults, fracture zo
44、nes, cavities, inclusions, and the like toevaluate their affects. Design the testing program so that affectsof local geology can be clearly distinguished.9.2 The size of the plate will be determined by localgeology, pressures to be applied, and the size of the adit to betested. These parameters shou
45、ld be considered prior to exca-vation of the adit. Optimum adit dimensions are approximatelysix times the plate diameter; recommended plate diameter iscommonly 112 to 314 ft (0.5 to 1 m). Other sizes are useddepending upon site specifics.9.3 The affects of anistropy should be investigated byappropri
46、ately 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 basalt flow.9.4 Tests should be performed at a site not affected bystructural changes resulting from excavations of the adit. Thezone of
47、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 loads measure theresponse of rock further away from the test adit. Thus, if therock around the adit is damaged by the excavation process, a
48、ndthe deformational properties of the damaged zone are theprimary objective of the test program, small-diameter platetests on typically excavated surfaces are adequate. If theundisturbed in situ modulus is desired, larger diameter platesand higher loads may be used, although practical consider-ation
49、s 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 testarea to limit damage to the rock and the resulting need forlarger plates and loads.D43950439.5 Cores, if any, should be logged and tested for rockquality designation (RQD), fracture spacing, strength, anddeformation in accordance with Guide D 5434 and TestMethod D 6032.9.6 Site conditions may dictate that site preparation and padconstruction be performed immediately after excavation.10. Procedu
