1、Designation: D4555 10Standard Test Method forDetermining Deformability and Strength of Weak Rock by anIn Situ Uniaxial Compressive Test1This standard is issued under the fixed designation D4555; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f 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 measurement of the deform-ability and strength of large in situ s
3、pecimens of rock by auniaxial compressive test. The test results take into account theeffect of both intact material behavior and the behavior ofdiscontinuities contained within the specimen block.1.2 This test method does not cover which type of specimenshould be tested or whether anisotropic facto
4、rs should beconsidered. The specifics of the test program need to bedeveloped prior to testing and possibly even before sampling.Such specifics would be dependent on the intended use of thedata, as well as any budgetary constraints and other factors,which are outside the scope of this test method.1.
5、3 Theoretically there is no limit to the size of the testspecimen; however, size will be controlled by the strength ofthe test specimen relative to the capacity of any loadingapparatus and bearing capacity of the surface the apparatusmust react against. Furthermore, the orientation and strength ofdi
6、scontinuities relative to the specimen geometry will be afactor limiting specimen size too.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.5 The values stated in SI units are to be regarded as thestandard.1.6 Th
7、is 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 prior to use.2. Referenced Documen
8、ts2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD6026 Practice for Using Significant Digits in GeotechnicalDataD6032 Test Method for Determining Rock Quality Desig-n
9、ation (RQD) of Rock CoreD7012 Test Method for Compressive Strength and ElasticModuli of Intact Rock Core Specimens under VaryingStates of Stress and Temperatures3. Terminology3.1 For definitions of terms used in this test method refer toTerminology D653.3.2 Definitions of Terms Specific to This Stan
10、dard:3.2.1 rock quality designation, RQDa method for quanti-tatively describing the nature of a rock mass from core borings.RQD is obtained by measuring the total length of all unweath-ered pieces of core greater than or equal to 100 mm anddividing the total by the length of the particular core run.
11、 Thisquantity is expressed as a percent and is used to classify in siturock. See Test Method D6032.3.2.2 average joint fragment volumethe average size ofdiscrete rock blocks delineated by joints (discontinuities) in thetest specimen.3.2.2.1 DiscussionAverage joint fragment volume is simi-lar to othe
12、r rock mass rating factors such as block volume andother methods described by Palmstrom3that take into accountdiscontinuities breaking up an otherwise intact rock mass intodiscrete rock blocks of various sizes, and can estimate theaverage volume and statistical distribution of all the discreteblocks
13、 in a volume of rock. This is analogous to measuring orsieving all the discrete blocks in a rock mass and determininga distribution of block sizes, much the same as is used todescribe the particle sizes of a soil specimen. Such informationmay explain any differences between test results. This could
14、be1This test method is under the jurisdiction of Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved Jan. 15, 2010. Published March 2010. Originallyapproved in 1985. Last previous edition approved in 2005 as D4555 01 (2005)
15、.DOI: 10.1520/D4555-10.2For 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.3Palmstrom, A, “The volumetric joint c
16、ount a useful and simple measure of thedegree of rock jointing”, Proceedings of the 4th International Congress on RockMechanics, ISRM, Vol. 2, 1982, pp. 221-228.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
17、onshohocken, PA 19428-2959, United States.a one, two or three dimensional value depending on the way itwas measured and the requirements of the program for whichit is to be used.3.2.3 volumetric joint count (Jv)the total number of joints(discontinuities) per unit length for each joint (discontinuity
18、)set which is then added together to give the total number ofjoints per cubic meter.3.2.3.1 DiscussionThis could be a unidirectional mea-surement when done on drill core and therefore dependent onthe direction of the drill hole(s) relative to the orientation of thediscontinuity sets. Nonparallel (pr
19、eferably orthogonal) scanline fracture surveys as well as drill holes could be used as wellto take into account spatial orientations issues. Palmstromrelated volumetric joint count (Jv) to RQD with the followingformula: Jv= (115 RQD)/3.3, with RQD = 0 for Jv 35.3.2.3.2 DiscussionFrom a review of the
20、 literature, Dr.Hoek refers to volume joint count (Jv) as joints per meter,whereas Bieniawski refers to it as joints per cubic meter.Therefore, there may be some differences in how the definitionof volumetric joint count is interpreted or used.4. Significance and Use4.1 Since there is no reliable me
21、thod of predicting theoverall strength and deformation data of a rock mass from theresults of laboratory tests on small specimens, in situ tests onlarge specimens are necessary, especially if the specimen sizerequired for a given grain size would exceed the size that canbe obtained for or tested in
22、a laboratory as stated in TestMethod D7012. Such tests also have the advantage that therock specimen is tested under similar environmental conditionsas prevailing for the rock mass.4.2 Since the strength of rock is dependent on the size of thetest specimen and discontinuities, it is necessary to tes
23、t severalspecimens (laboratory or field, or both) of progressivelyincreasing size until an asymptotically constant strength valueis found. This value is taken to represent the strength of therock mass.4,5NOTE 1Notwithstanding the statements on precision and bias con-tained in this test method; the p
24、recision of this test method is dependenton the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of Practiceare generally considered capable of competent and objective testing. Usersof this test method are cautioned t
25、hat compliance with Practice does notin itself assure reliable testing. Reliable testing depends on many factors.Practice provides a means of evaluating some of those factors.4.3 The test method is shown only being conducted under-ground and vertical. However, this test method could be donein a quar
26、ry or on the surface if a reaction frame could be set upto behave as a reactive surface in place of a tunnel crown.5. Apparatus5.1 Preparation Equipment:5.1.1 Equipment for cutting specimen blocks from existingunderground exposed faces, for example, a road header ma-chine, drills for line drilling,
27、pneumatic chisel, or other rockexcavation or shaping tools.5.1.2 If needed, equipment to make test area safe forpreparation of specimen such as rock bolts, steel mesh, or otherground support hardware.5.1.3 No explosives are permitted.5.1.4 Cement and other associated equipment to mix, handleand cast
28、 loading cap and load bearing pad above and below theloading system.5.2 Loading System:5.2.1 Hydraulic Cylinder/Ram or Flat JacksThis equip-ment is required to apply a uniformly distributed load to thecomplete upper face of the specimen. The loading system shallbe of sufficient capacity and travel t
29、o load the specimen tofailure. Multiple hydraulic jacks fed by a common manifoldshould be avoided. Hydraulic cylinder/ram jacks are usuallypreferred because of the available higher load and displace-ment ranges than what can be obtained with flat jacks.5.2.2 Loading platenPlatens are used to transmi
30、t the axialload to the top of the specimen. The dimensional widths of thebearing surface of the platen shall be at least as great as thespecimen dimensional widths, but shall not exceed 1.10 timesany dimensional width of the specimen. The platen thicknessshall be at least one-half the specimen avera
31、ge width. Theplaten is ideally made of aluminum for ease of handling, butother materials may be used if strong enough.5.2.3 Steel cables, or other suitable method, attached be-tween the loading system components placed on the testspecimen and the overlying support for safety reasons as wellas preven
32、ting equipment damage due to falling to floor after thespecimen fails.5.2.4 Hydraulic Pumping SystemThis system needs tosupply oil at the required pressure to the jacks, the pressurebeing controlled to give a constant rate of displacement orstrain, rather than a constant rate of stress increase.NOTE
33、 2Experience has shown that deformation-controlled loading ispreferable to stress-controlled loading because it results in a more stable,and thus safer, test. This result is a consequence of the strain softeningnature of most rock or rock-like materials. A single stress level maycorrespond to differ
34、ent values of strain during any test, with the level ofstrain continuing to increase throughout a test. One way to achieveuniform deformation of the specimen is to use a separate pump for eachjack and to set the oil delivery rate of each pump to the same value.Standard diesel fuel injection pumps ha
35、ve been found suitable and arecapable of supplying pressures up to 100 MPa. The delivery rate of thesepumps can be set very accurately.5.3 Equipment to Measure Applied Load and Deformationin the Specimen:5.3.1 Load Measuring EquipmentThis equipment, forexample, electric, hydraulic, or mechanical loa
36、d cells, permitsthe applied load to be measured with an accuracy better than65 % of the maximum in the test.5.3.2 Deformation Measurement DevicesMechanical orelectrical, or similar displacement measuring devices, withrobust fittings to enable the instruments to be mounted so thatthe strain in the ce
37、ntral third of each specimen face can bedetermined with an accuracy better than 6 105. Deformationis to be measured in the direction of applied load and also in aperpendicular direction if Poissons ratio values are to be4Bieniawski, Z. T., and Van Heerdan, W. L., “The Significance of Large-Scale InS
38、itu Tests,” International Journal of Rock Mechanics Mining Sciences, Vol 1, 1975.5Heuze, F. E., “Scale Effects in the Determination of Rock Mass Strength andDeformability,” Rock Mechanics, Vol 12, 1980, pp 167192.D4555 102determined. Remote reading of any such devices is requireddue to the safety is
39、sues of taking readings up close while thespecimen is being loaded and during failure.5.4 Calibration EquipmentEquipment to calibrate theloading and displacement measuring systems, the accuracy ofcalibration to be better than the accuracies of test measurementspecified in 5.3.1 and 5.3.2. Calibrate
40、all measuring instru-ments both before and after each test series.6. Procedure6.1 Preparation of Specimens:6.1.1 Besides rock type, selection of test sites should in-clude planning the specimen location to minimize any knowngeologic factors from causing the final specimen or bearingareas to fail dur
41、ing preparation or the test. This may requiremapping the prospective test volume and then estimating thebest location within that volume for the specimen prior toexcavation rather randomly picking a site. Furthermore, asmentioned in Section 4.2, the strength of rock is dependent onthe size of the te
42、st specimen. Therefore, if such data isnecessary then several specimens (laboratory or field, or both)of progressively increasing size will need to be prepared.6.1.2 Label or name each test specimen or site according tosome logical sequence of alpha-numeric text.6.1.3 Cut specimens of the required d
43、imensions from theexposed rock faces (Fig. 1). The specimen shall have aheight-to-minimum-width dimension ratio of 2.0 to 2.5. Theratio of the maximum width of the specimen to the minimumwidth shall be as near to 1.0 as practicable.6.1.3.1 First, remove loose and damaged rock. Make verti-cal cuts as
44、 shown in Fig. 1 to form the vertical faces of thespecimen. Dimensional uniformity of each vertical face of thetest specimen should not deviate by more than 20 mm. If thereis such deviation, abandon the specimen. Make a horizontal cutto form the top face of the specimen. Remove loose rock andtrim th
45、e specimen to final size using hand tools.NOTE 3Specimen dimensions cannot be specified because they de-pend on the rock properties, for example, the thickness of strata, thespacing and orientation of discontinuities, and the ease with whichspecimens can be prepared. It is recommended that a number
46、of tests bedone with a specimen with a width of about 0.5 m and that the size ofsubsequent specimens should be increased until an asymptotically con-stant strength value is reached. It is probable that the largest test specimenwill have a minimum width which meets the average grain size recom-mended
47、 in Test Method D7012, of at least 10 times greater than, but maynot meet the recommended average dimension of the rock blocks definedby the discontinuities. For weak rock types, which behave more like soil(for example, weakly cemented sandstone), the minimum specimen widthshall be at least six time
48、s the maximum particle diameter.FIG. 1 Plan and Cross Sectional Views of a Hypothetical Underground Test Site Adjacent to a Tunnel or Adit Wall and Showing aSuggested Excavation Sequence for Specimen Preparation.D4555 1036.2 Pretesting Specimen Documentation:6.2.1 Clean and inspect the specimen.6.2.
49、2 Record in detail the geological structure of the blockand nature of the reaction faces of the block.6.2.3 Measure specimen geometry, including the geometryof defects in the block, with accuracy better than 5 mm so thatthe average specimen dimensions and each discontinuitiesvolumetric joint count can be determined.6.2.4 Prepare photographs and drawings to illustrate bothgeological and geometric characteristics.6.3 Preparation of Reaction Surfaces for Loading Appara-tus:6.3.1 Cast a concrete pad, suitably reinforced, to cover thetop face of the specimen (Fig. 2
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