ASTM D4553-2002(2006) Standard Test Method for Determining In Situ Creep Characteristics of Rock《岩石蠕变特性现场测定的标准试验方法》.pdf

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1、Designation: D 4553 02 (Reapproved 2006)Standard Test Method forDetermining In Situ Creep Characteristics of Rock1This standard is issued under the fixed designation D 4553; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year

2、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 documentation for determining in situ

3、creep characteristics of a rock mass using a rigid platesubjected to controlled loading.1.2 This test method is designed to be conducted in anunderground opening; however, with suitable modifications,this test could be conducted at the surface.1.3 The test is usually conducted parallel or perpendicu

4、lar tothe anticipated axis of thrust, as dictated by the design load orother orientations, based upon the application.1.4 Flexible plate apparatus can be used if the anticipatedcreep displacement is within the tolerance of the travel of theflat jacks.1.5 The values stated in inch-pound units are to

5、be regardedas the standard.1.6 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 p

6、rior to use. For specificprecaution statements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering D

7、esign 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 Rock3. Terminology3.1 Definitions: See Terminology D 653 for general defini-tions.3.2 Definitions of Terms Specific to

8、This Standard:3.2.1 creepa time-dependent displacement of a platepushed into the surface of the rock by a constant normal load.It is not directly related with laboratory creep data because ofthe nonuniformity of stress within the rock mass underneaththe plate.3.2.2 displacementmovement of the rigid

9、plate, groutpad, or rock in response to and in the same direction as theapplied load.3.2.3 loadtotal force acting on the rock face.3.2.4 rigid plateplate with a deflection of less than 0.0005in. (0.0125 mm) from the center to the edge of the plate whenmaximum load is applied.4. Summary of Test Metho

10、d4.1 Areas on two opposing faces of a test opening areflattened, smoothed, and made parallel.4.2 A grout pad and rigid metal plate are installed againsteach face and a hydraulic loading system is placed between therigid plates.4.3 The two faces are rapidly loaded to the desired creepload, without sh

11、ock, the load maintained, and the displacementof the plate measured as a function of time.5. Significance and Use5.1 Results of this test method are used to predict time-dependent deformation characteristics of a rock mass resultingfrom loading. It is a test that may be required depending onrock typ

12、e or anticipated loads, or both.5.2 This test method may be useful in structural designanalysis where loading is applied over an extensive period.5.3 This test method is normally performed at ambienttemperature, but equipment can be modified or substituted foroperations at other temperatures.5.4 Res

13、ults of this test method may be useful in verifyinglaboratory creep data and structural mathematical modelinganalyses.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 Ma

14、y 1, 2006. Published June 2006. Originallyapproved in 1985. Last previous edition approved in 2002 as D 455302.2For 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 s

15、tandards 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5 Creep characteristics are determined under a nonuni-form state of

16、 stress.5.6 If during a field investigation, time-dependent charac-teristics are detected, then an in situ creep test shall beperformed.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 faci

17、lities 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 that compliance with Practice D 3740does not in itself assurereliable results. Reliable results depend on man

18、y factors; Practice D 3740provides a means of evaluating some of those factors.6. Interferences6.1 A completely inflexible plate used to load the rock faceis difficult to construct. However, if the plate is constructed asrigid as feasible, the rock face is smoothed, and a thin,high-modulus material

19、is used for the pad, the error in themeasured displacements will be minimal.6.2 The rock under the loaded area is generally not homo-geneous, as assumed in theory. The rock will respond to theload according to its local deformational characteristics andorientation of discontinuities. The use of the

20、average platedisplacement will mitigate this problem. If this creep test isperformed immediately after a plate loading test, the results ofthe creep test will be different than if it had been performed onvirgin rock.7. Apparatus7.1 Surface Preparation Equipment Test-site preparationequipment should

21、include an assortment of excavation tools,such as drills and chipping hammers. Blasting shall not beallowed during final preparation of the test site.7.2 Instrumentation:7.2.1 Displacement Measuring Equipment For displace-ment measurements, dial gages or linear variable differentialtransformers (LVD

22、Ts) are generally used. A sensitivity of atleast 60.0001 in. (0.0025 mm), including the error of thereadout equipment, and an accuracy of at least 0.0005 in.(0.0125 mm) are required. Errors in excess of 0.0004 in. (0.01mm) can invalidate test results when the modulus of rock massexceeds 5 3 106psi (

23、3.5 3 104MPa).7.2.2 Load CellA load cell is recommended to measurethe load on the bearing plate. An accuracy of 61000 lbf (4.4kN) or 65 % of maximum test load, including errors intro-duced by the readout system, and a sensitivity of at least 500lbf (2.2 kN) are reasonable. Long-term stability of the

24、 instru-mentation system shall be verified throughout the test.7.3 Loading Equipment:7.3.1 Hydraulic Ram or Flat JacksThis equipment, ca-pable of applying and maintaining desired pressures towithin6 3 %, is usually used to apply the load. A sphericalbearing of suitable capacity shall be coupled to o

25、ne of thebearing plates. If a hydraulic ram is used, the load shall becorrected to account for the effects of ram friction. If flat jacksare used, the jacks shall not be expanded beyond a thicknessequal to3%ofthediameter of a metal jack.7.3.2 The loading equipment includes a device for applyingthe l

26、oad and the reaction members, usually thick-walledaluminum or steel pipes, to transmit the load.7.3.3 Load Maintaining EquipmentEquipment such as aservo-control system or air over hydraulic oil is required.7.3.4 Bearing PadsThe bearing pads shall have a modu-lus of elasticity of at least 4 3 106psi

27、(3 3 104MPa) (30 GPa)and shall be capable of conforming to the rock surface andbearing plate. High early strength grout or molten sulfurbearing pads are recommended.7.3.5 Bearing PlatesThe bearing plates shall approximatea rigid die as closely as practical. A bearing plate that has beenfound satisfa

28、ctory is shown in Fig. 1.Although the exact designand materials may differ, the stiffness of the bearing plate shallbe at least the minimum stiffness necessary to produce nomeasurable deflection of the plate under maximum load.8. Precautions8.1 All equipment and apparatus shall comply with theperfor

29、mance specifications in Section 7 and apparatus shall beverified. If no requirements are stated in Section 7, themanufacturers specifications for the equipment may be appro-priate as a guide to assure acceptable performance. Perfor-mance verification is generally done by calibrating the equip-ment a

30、nd measurement system (see Fig. 2).8.2 Enforce safety by applicable safety standards. Pressurelines must be bled of air to preclude violent failure of thepressure system.9. In Situ Conditions9.1 Areas that are geologically representative of the massshall be selected. The plates shall be contained in

31、 the samegeologic member. The testing program shall be designed sothat effects of local geology can be clearly distinguished andthe impact of excavation minimized.9.2 The size of the bearing plate will be determined by thelocal geology, pressures to be applied, and the size of theopening in which th

32、e test is to be performed. These parametersshall be considered prior to excavation of the opening. Opti-mum opening dimensions are approximately six times the platediameter. Recommended plate diameter is commonly 1 1/2 to3 1/2 ft (0.5 to 1 m). Other plate sizes may be used dependingupon site specifi

33、cs.9.3 The effects of anisotropy shall be investigated byappropriately oriented tests; for example, parallel and perpen-dicular 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 opening.The zone of

34、rock that contributes to the measured displacementduring loading depends on the diameter of the plate and theapplied load. Larger plates and higher loads measure theresponse of rock farther away from the test opening. Thus, ifthe rock around the opening is damaged by the excavationprocess and the cr

35、eep properties of the damaged zone are theprimary objective of the test program, small-diameter platetests on typically excavated surfaces are adequate.9.5 Site conditions may dictate that site preparation and padconstruction be performed immediately after excavation.D 4553 02 (2006)210. Procedure10

36、.1 A schematic of an optimum test setup is shown in Fig.3. A properly located platform (not shown) allows for align-ment of all test components.10.2 Conduct the test across a “diameter” or chord of theopening with the two test surfaces nearly parallel and in planesoriented perpendicular to the thrus

37、t of the loading assembly.10.3 Surface Preparation:10.3.1 MethodPrepare the surface by a method thatcauses minimal damage to the finished rock surface. In theinitial preparation of the finished test surface, many short drillholes may be required to remove unsound rock. Any residualrock between the d

38、rill holes may be removed by burnishing ormoving the bit back and forth until a smooth face is achieved.Alternatively, in hard, competent rock, controlled blasting withvery small charges may be required to remove the unwantedmaterials. In weaker materials, coarse grinding or cuttingdevices may be us

39、ed.10.3.2 SizeThe prepared rock surface shall extend at leastone-half the diameter of the bearing plate beyond the edge ofthe plate.10.3.3 Rock QualityTo the extent possible, prepare thebearing surface in sound rock. Remove loose and broken rockfrom the excavation. Deeper breaks may be detected by a

40、 dullhollow sound when the rock surface is struck with a hammer;remove such material.10.3.4 SmoothnessThe prepared rock face shall be assmooth as practicable. In no case shall the deviation from aplane between the highest and lowest points exceed 1 in. (25mm).10.3.5 CleaningAfter the surface has bee

41、n prepared,scrub and rinse it with clean water to remove any looseparticles or dirt caused by the smoothing operation.10.4 Bearing Pad ConstructionConstruct the bearing pad,with the bearing plate in position, by pouring the pad materialbetween the rock surface and the plate. Contain the padmaterial

42、by suitable form work around the edges of the plate.The only exception to this method is for near vertical testswhere grout pads are used. In this case, the lower bearing platemay be placed directly upon the pad prior to curing. In allcases, exercise care to avoid air pockets or other cavities withi

43、nthe pad. The thickness of the pad shall be no more than 15 %of the plate diameter at any point. The dimensional require-ments are shown in Fig. 4.10.5 Displacement Measuring Points Measure the dis-placement of the bearing plate in at least three locations equallyFIG. 1 Rigid Bearing Plate for 12 in

44、. Diameter TestD 4553 02 (2006)3spaced around the plate. Support the displacement transducersso that only the displacement of the plate is measured.Generally, this means mounting the transducers from supportslocated outside the zone of influence of the test. In no case shallthe transducers be mounte

45、d on the loading apparatus. Crossopening measurement points and equipment such as describedin Practice D 4403 may be installed if desired.10.6 Pretest CheckAfter the loading and restraining com-ponents are installed, make a final check of all mechanical,hydraulic, and electronic components after the

46、 grout pads areplaced and again before the load is applied.10.7 Pressurization (Loading):10.7.1 Zero all measuring equipment.10.7.2 Rapidly raise the load without shock, to the requiredtest load. This is normally done within 1 min.10.7.3 Record the displacement transducer reading immedi-ately after

47、the required test load has been applied. Thereafter,record displacements at suitable time intervals. During thetransient creep period (Fig. 5), take displacement readingsevery few minutes to few hours until the displacement ratebecomes constant. Readings shall then be taken daily or at afrequency designated by the engineer.10.7.4 Record the load and ambient temperature at the timesof the readings, as a minimum.Project _ Test No. _Feature _ Rock type _Test location _ Plate diameter _Orientation _ Tested by _Sustain Load _EquipmentdescriptionSerialno.Date ofnext calibration_ _ _ _