1、Designation: D 4767 04Standard Test Method forConsolidated Undrained Triaxial Compression Test forCohesive Soils1This standard is issued under the fixed designation D 4767; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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 determination of strengthand stress-strain relationships of a cylindrical specimen ofe
3、ither an undisturbed or remolded saturated cohesive soil.Specimens are isotropically consolidated and sheared in com-pression without drainage at a constant rate of axial deforma-tion (strain controlled).1.2 This test method provides for the calculation of total andeffective stresses, and axial comp
4、ression by measurement ofaxial load, axial deformation, and pore-water pressure.1.3 This test method provides data useful in determiningstrength and deformation properties of cohesive soils such asMohr strength envelopes and Youngs modulus. Generally,three specimens are tested at different effective
5、 consolidationstresses to define a strength envelope.1.4 The determination of strength envelopes and the devel-opment of relationships to aid in interpreting and evaluatingtest results are beyond the scope of this test method and mustbe performed by a qualified, experienced professional.1.5 All obse
6、rved and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.5.1 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 desi
7、gn or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.6 The values stated in SI units shall be regarded as thestandard. The values stated in inch-pound units are approxi-mate.1.7 This standard does not purport to address all of thesafety concerns, if
8、 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 Documents2.1 ASTM Standards:2D 422 Method for Particle-Size Analysis of Soil
9、sD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 854 Test Method for Specific Gravity of SoilsD 1587 Practice for Thin-Walled Tube Sampling of SoilsD 2166 Test Method for Unconfined Compressive Strengthof Cohesive SoilD 2216 Method for Laboratory Determination of Water(Moisture) Conte
10、nt of Soil, Rock, and Soil-AggregateMixturesD 2435 Test Method for One-Dimensional ConsolidationProperties of SoilsD 2850 Test Method for Unconsolidated, Undrained Com-pressive Strength of Cohesive Soils in Triaxial Compres-sionD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Test
11、ing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4220 Practices for Preserving and Transporting SoilSamplesD 4318 Test Method for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD 4753 Specification for Evaluating, Selecting, and Speci-fying Balances and
12、 Scales for Use in Soil and RockTestingD 6026 Practice for Using Significant Digits in Geotechni-cal Data3. Terminology3.1 DefinitionsThe definitions of terms used in this testmethod shall be in accordance with Terminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 back pressurea
13、 pressure applied to the specimenpore-water to cause air in the pore space to compress and to1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.05 on Strength andCompressibility of Soils.Current edition approved Nov.
14、1, 2004. Published December 2004. Originallyapproved in 1988. Last previou edition approved in 2002 as D 4767 02.2For 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
15、 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.pass into solution in the pore-water thereby increasing thepercent
16、saturation of the specimen.3.2.2 effective consolidation stressthe difference betweenthe cell pressure and the pore-water pressure prior to shearingthe specimen.3.2.3 failurethe stress condition at failure for a testspecimen. Failure is often taken to correspond to the maximumprincipal stress differ
17、ence (maximum deviator stress) attainedor the principal stress difference (deviator stress) at 15 % axialstrain, whichever is obtained first during the performance of atest. Depending on soil behavior and field application, othersuitable failure criteria may be defined, such as maximumeffective stre
18、ss obliquity, s81/s83, or the principal stressdifference (deviator stress) at a selected axial strain other than15 %.4. Significance and Use4.1 The shear strength of a saturated soil in triaxial com-pression depends on the stresses applied, time of consolidation,strain rate, and the stress history e
19、xperienced by the soil.4.2 In this test method, the shear characteristics are mea-sured under undrained conditions and is applicable to fieldconditions where soils that have been fully consolidated underone set of stresses are subjected to a change in stress withouttime for further consolidation to
20、take place (undrained condi-tion), and the field stress conditions are similar to those in thetest method.NOTE 1If the strength is required for the case where the soil is notconsolidated during testing prior to shear, refer to Test Method D 2850 orTest Method D 2166.4.3 Using the pore-water pressure
21、 measured during the test,the shear strength determined from this test method can beexpressed in terms of effective stress. This shear strength maybe applied to field conditions where full drainage can occur(drained conditions) or where pore pressures induced byloading can be estimated, and the fiel
22、d stress conditions aresimilar to those in the test method.4.4 The shear strength determined from the test expressed interms of total stresses (undrained conditions) or effectivestresses (drained conditions) is commonly used in embankmentstability analyses, earth pressure calculations, and foundatio
23、ndesign.NOTE 2Notwithstanding the statements on precision and bias con-tained in this test method. The precision of this test method is dependenton the competence of the personnel performing it and the suitability of theequipment and facilities used.Agencies which meet the criteria of PracticeD 3740
24、 are generally considered capable of competent testing. Users ofthis test method are cautioned that compliance with Practice D 3740 doesnot ensure reliable testing. Reliable testing depends on several factors;Practice D 3740 provides a means of evaluating some of those factors.5. Apparatus5.1 The re
25、quirements for equipment needed to performsatisfactory tests are given in the following sections. See Fig.1 and Fig. 25.2 Axial Loading DeviceThe axial loading device shallbe a screw jack driven by an electric motor through a gearedtransmission, a hydraulic loading device, or any other com-pression
26、device with sufficient capacity and control to providethe rate of axial strain (loading) prescribed in 8.4.2. The rate ofadvance of the loading device shall not deviate by more than61 % from the selected value. Vibration due to the operationof the loading device shall be sufficiently small to not ca
27、usedimensional changes in the specimen or to produce changes inpore-water pressure when the drainage valves are closed.FIG. 1 Schematic Diagram of a Typical Consolidated UndrainedTriaxial ApparatusD4767042NOTE 3A loading device may be judged to produce sufficiently smallvibrations if there are no vi
28、sible ripples in a glass of water placed on theloading platform when the device is operating at the speed at which thetest is performed.5.3 Axial Load-Measuring DeviceThe axial load-measuring device shall be a load ring, electronic load cell,hydraulic load cell, or any other load-measuring device ca
29、pableof the accuracy prescribed in this paragraph and may be a partof the axial loading device. The axial load-measuring deviceshall be capable of measuring the axial load to an accuracy ofwithin 1 % of the axial load at failure. If the load-measuringdevice is located inside the triaxial compression
30、 chamber, itshall be insensitive to horizontal forces and to the magnitude ofthe chamber pressure.5.4 Triaxial Compression ChamberThe triaxial chambershall have a working chamber pressure equal to the sum of theeffective consolidation stress and the back pressure. It shallconsist of a top plate and
31、a base plate separated by a cylinder.The cylinder may be constructed of any material capable ofwithstanding the applied pressures. It is desirable to use atransparent material or have a cylinder provided with viewingports so the behavior of the specimen may be observed.The topplate shall have a vent
32、 valve such that air can be forced out ofthe chamber as it is filled. The baseplate shall have an inletthrough which the pressure liquid is supplied to the chamber,and inlets leading to the specimen base to the cap to allowsaturation and drainage of the specimen when required. Thechamber shall provi
33、de a connection to the cap.5.5 Axial Load PistonThe piston passing through the topof the chamber and its seal must be designed so the variationin axial load due to friction does not exceed 0.1 % of the axialFIG. 2 Filter Strip CageD4767043load at failure and so there is negligible lateral bending of
34、 thepiston during loading.NOTE 4The use of two linear ball bushings to guide the piston isrecommended to minimize friction and maintain alignment.NOTE 5A minimum piston diameter of16 the specimen diameter hasbeen used successfully in many laboratories to minimize lateral bending.5.6 Pressure and Vac
35、uum-Control DevicesThe chamberpressure and back pressure control devices shall be capable ofapplying and controlling pressures to within 62 kPa (0.25lb/in.2) for effective consolidation pressures less than 200 kPa(28 lb/in.2) and to within 61 % for effective consolidationpressures greater than 200 k
36、Pa. The vacuum-control deviceshall be capable of applying and controlling partial vacuums towithin 62 kPa. The devices shall consist of pressure/volumecontrollers, self-compensating mercury pots, pneumatic pres-sure regulators, combination pneumatic pressure and vacuumregulators, or any other device
37、 capable of applying andcontrolling pressures or partial vacuums to the required toler-ances. These tests can require a test duration of several day.Therefore, an air/water interface is not recommended for eitherthe chamber pressure or back pressure systems, unless isolatedfrom the specimen and cham
38、ber (e.g. by long tubing).5.7 Pressure- and Vacuum-Measurement DevicesThechamber pressure-, back pressure-, and vacuum-measuringdevices shall be capable of measuring pressures or partialvacuums to the tolerances given in 5.6. They may consist ofBourdon gages, pressure manometers, electronic pressure
39、transducers, or any other device capable of measuring pres-sures, or partial vacuums to the stated tolerances. If separatedevices are used to measure the chamber pressure and backpressure, the devices must be calibrated simultaneously andagainst the same pressure source. Since the chamber and backpr
40、essure are the pressures taken at the mid-height of thespecimen, it may be necessary to adjust the calibration of thedevices to reflect the hydraulic head of fluids in the chamberand back pressure control systems.5.8 Pore-Water Pressure-Measurement DeviceThe speci-men pore-water pressure shall also
41、be measured to the toler-ances given in 5.6. During undrained shear, the pore-waterpressure shall be measured in such a manner that as little wateras possible is allowed to go into or out of the specimen. Toachieve this requirement, a very stiff electronic pressuretransducer or null-indicating devic
42、e must be used. With anelectronic pressure transducer the pore-water pressure is readdirectly. With a null-indicating device a pressure control iscontinuously adjusted to maintain a constant level of thewater/mercury interface in the capillary bore of the device. Thepressure required to prevent move
43、ment of the water is equal tothe pore-water pressure. Both measuring devices shall have acompliance of all the assembled parts of the pore-waterpressure-measurement system relative to the total volume ofthe specimen, satisfying the following requirement:DV/V!/Du 5 m) tube that is impermeable toair b
44、etween the air-water interface and test specimen, by separating theback-pressure water from the air by a material or fluid that is relativelyimpermeable to air, by periodically replacing the back-pressure water withdeaired water, or by other means.NOTE 16Although the pore pressure Parameter B is use
45、d to determineadequate saturation, the B-value is also a function of soil stiffness. If thesaturation of the sample is 100 %, the B-value measurement will increasewith decreasing soil stiffness. Therefore, when testing soft soil samples, aB-value of 95 % may indicate a saturation less than 100 %.NOT
46、E 17The back pressure required to saturate a compacted speci-men may be higher for the wet mounting method than for the drymounting method and may be as high as 1400 kPa (200 lb/in.2).NOTE 18Many laboratories use differential pressure regulators andtransducers to achieve the requirements for small d
47、ifferences betweenchamber and back pressure.8.2.4 Measurement of the Pore Pressure ParameterBDetermine the value of the pore pressure Parameter B inaccordance with 8.2.4.1 through 8.2.4.4. The pore pressureParameter B is defined by the following equation:B 5Du/Ds3(2)where:Du = change in the specimen
48、 pore pressure that occurs asa result of a change in the chamber pressure whenthe specimen drainage valves are closed, andDs3= change in the chamber pressure.8.2.4.1 Close the specimen drainage valves, record the porepressure, to the nearest 0.7 kPa (0.1 psi), and increase thechamber pressure by 70
49、kPa (10 lb/in.2).8.2.4.2 After approximately 2 min, determine and record themaximum value of the induced pore pressure to the nearest 0.7kPa (0.1 psi),. For many specimens, the pore pressure maydecrease after the immediate response and then increaseslightly with time. If this occurs, values of Du should be plottedwith time and the asymptotic pore pressure used as the changein pore pressure. A large increase in Du with time or values ofDu greater than Ds3indicate a leak of chamber fluid into thespecimen. Decreasing values of Du with time may indicate aleak in th
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