1、Designation: D3080/D3080M 11Standard Test Method forDirect Shear Test of Soils Under Consolidated DrainedConditions1This standard is issued under the fixed designation D3080/D3080M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the con-solidated drained shear strength of one specimen of a
3、 soilmaterial under direct shear boundary conditions. The specimenis deformed at a controlled rate on or near a single shear planedetermined by the configuration of the apparatus.1.2 Shear stresses and displacements are nonuniformly dis-tributed within the specimen. An appropriate height cannot bede
4、fined for calculation of shear strains. Therefore, stress-strainrelationships or any associated quantity such as the shearmodulus, cannot be determined from this test.1.3 The determination of strength envelopes and the devel-opment of criteria to interpret and evaluate test results are leftto the en
5、gineer or office requesting the test.1.4 The results of the test may be affected by the presence ofcoarse-grained soil or rock particles, or both, (see Section 7).1.5 Test conditions, including normal stress and moistureenvironment, should be selected to represent the field condi-tions being investi
6、gated. The rate of shearing must be slowenough to ensure drained conditions.1.6 Generally, three or more tests are performed on speci-mens from one soil sample, each under a different normal load,to determine the effects upon shear resistance and displace-ment. Results from a test series are combine
7、d to determinestrength properties such as Mohr strength envelopes. Interpre-tation of multiple tests requires engineering judgment and isbeyond the scope of this test method. This test method pertainsto the requirements for a single test.1.7 There may be instances when the gap between the shearbox h
8、alves should be increased to accommodate sand sizedparticles greater than the specified gap. Presently there isinsufficient information available for specifying the gap dimen-sion based on particle size distribution.1.8 UnitsThe values stated in either inch-pound units orSI units given in brackets a
9、re to be regarded separately asstandard. The values stated in each system may not be exactequivalents; therefore, each system shall be used independentlyof the other. Combining values from the two systems mayresult in non-conformance with the standard.1.8.1 The gravitational system of inch-pound uni
10、ts is used.In this system, the pound (lbf) represents a unit of force(weight), while the unit for mass is slugs. The slug unit is notgiven, unless dynamic (F = ma) calculations are involved.1.9 All observed and calculated values shall conform to theguidelines for significant digits and rounding esta
11、blished inPractice D6026.1.9.1 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 design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its sco
12、pe.1.10 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 prior to use.2. Referenc
13、ed Documents2.1 ASTM Standards:2D422 Test Method for Particle-Size Analysis of SoilsD653 Terminology Relating to Soil, Rock, and ContainedFluidsD698 Test Methods for Laboratory Compaction Character-istics of Soil Using Standard Effort (12 400 ft-lbf/ft3(600kN-m/m3)D1557 Test Methods for Laboratory C
14、ompaction Charac-teristics of Soil Using Modified Effort (56,000 ft-lbf/ft3(2,700 kN-m/m3)D1587 Practice for Thin-Walled Tube Sampling of Soils forGeotechnical PurposesD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD2435 Test Methods for One-Dime
15、nsional ConsolidationProperties of Soils Using Incremental Loading1This 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. 1, 2011. Published January
16、2012. Originallyapproved in 1972. Last previous edition approved in 2004 as D308004. DOI:10.1520/D3080_D3080M-11.2For 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
17、 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.D2487 Practice for Classification of Soils for EngineeringPurposes
18、(Unified Soil Classification System)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4220 Practices for Preserving
19、 and Transporting SoilSamplesD4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD6026 Practice for Using Significant Digits in Geotec
20、hnicalDataD6027 Practice for Calibrating Linear Displacement Trans-ducers for Geotechnical Purposes3. Terminology3.1 DefinitionsFor definitions of common technical termsused in this test method, refer to Terminology D653.3.2 Description of Terms Specific to This Standard:3.2.1 FailureThe stress cond
21、ition at failure for a testspecimen. Failure is often taken as the maximum shear stressattained, or in the absence of a peak condition, the shear stressat 10 percent relative lateral displacement. Depending on soilbehavior and field application, other suitable criteria may bedefined at the direction
22、 of the requesting agency.3.2.2 Nominal Normal StressIn the direct shear test, theapplied normal (vertical) force divided by the area of the shearbox. The contact area of the specimen on the imposed shearplane decreases during shear and hence the true normal stressis unknown.3.2.3 Nominal Shear Stre
23、ssIn the direct shear test, theapplied shear force divided by the area of the shear box. Thecontact area of the specimen on the imposed shear planedecreases during shear and hence the true shear stress isunknown.3.2.4 Percent Relative Lateral DisplacementThe ratio, inpercent, of the relative lateral
24、 displacement to the diameter orlateral dimension of the specimen in the direction of shear.3.2.5 PreshearIn strength testing, the stage of a test afterthe specimen has stabilized under the consolidation loadingcondition and just prior to starting the shearing phase. It is usedas an adjective to mod
25、ify phase relations or stress conditions.3.2.6 Relative Lateral DisplacementThe displacement be-tween the top and bottom shear box halves.4. Summary of Test Method4.1 This test method consists of placing the test specimen inthe direct shear device, applying a predetermined normalstress, providing fo
26、r wetting or draining of the test specimen, orboth, consolidating the specimen under the normal stress,unlocking the shear box halves that hold the test specimen, andshearing the specimen by displacing one shear box halflaterally with respect to the other at a constant rate of shearingdeformation wh
27、ile measuring the shearing force, relative lat-eral displacement, and normal displacement (Fig. 1). Theshearing rate must be slow enough to allow nearly completedissipation of excess pore pressure.5. Significance and Use5.1 The direct shear test is suited to the relatively rapiddetermination of cons
28、olidated drained strength properties be-cause the drainage paths through the test specimen are short,allowing excess pore pressure to dissipate more rapidly thanother drained stress tests. The test can be made on any type ofsoil material. It is applicable for testing intact, remolded, orreconstitute
29、d specimens. There is however, a limitation on themaximum particle size (see 6.2).5.2 The test results are applicable to assessing strength in afield situation where complete consolidation has occurredunder the existing normal stresses. Failure is reached slowlyunder drained conditions so that exces
30、s pore pressures aredissipated. The shear rate must meet the requirements of 9.10.The results from several tests may be used to express therelationship between consolidation stress and drained shearstrength.NOTE 1The equipment specified in this standard method is notappropriate for performing undrai
31、ned shear tests. Using a fast displace-ment rate without proper control of the volume of the specimen will resultin partial drainage and incorrect measurements of shear parameters.5.3 During the direct shear test, there is rotation of principalstresses, which may or may not model field conditions.Mo
32、reover, failure may not occur on the weakest plane sincefailure is forced to occur on or near a plane through the middleof the specimen. The fixed location of the plane in the test canbe an advantage in determining the shear resistance alongrecognizable weak planes within the soil material and forte
33、sting interfaces between dissimilar materials.5.4 Shear stresses and displacements are nonuniformly dis-tributed within the specimen, and an appropriate height is notdefined for calculating shear strains or any associated engineer-ing quantity. The slow rate of displacement provides fordissipation o
34、f excess pore pressures, but it also permits plasticflow of soft cohesive soils.5.5 The number of tests in a series normal stress level, rateof shearing, and general test conditions should be selected toapproximate the specific soil conditions being investigated.5.6 The area of the shear surface dec
35、reases during the test.This area reduction creates uncertainty in the actual value ofthe shear and normal stress on the shear plane but should notaffect the ratio of these stresses.NOTE 2Notwithstanding the statement on precision and bias con-tained in this standard: The precision of this test metho
36、d is dependent onthe competence of the personnel performing the test and the suitability ofthe equipment and facilities used. Agencies which meet the criteria ofFIG. 1 Test Specimens in Single Shear ApparatusD3080/D3080M 112Practice D3740 are generally considered capable of competent andobjective te
37、sting. Users of this test method are cautioned that compliancewith Practice D3740 does not in itself assure reliable testing. Reliabletesting depends on several factors; Practice D3740 provides a means ofevaluating some of these factors.6. Apparatus6.1 Shear DeviceA device to hold the specimen secur
38、elybetween two porous inserts in such a way that torque is notapplied to the specimen. The shear device shall provide ameans of applying a normal stress to the faces of the specimen,for measuring change in thickness of the specimen, forpermitting drainage of water through the porous inserts at theto
39、p and bottom boundaries of the specimen, and for submerg-ing the specimen in water. The device shall be capable ofapplying a shear force to the specimen along a predeterminedshear plane (single shear) parallel to the faces of the specimen.The frames that hold the specimen shall be sufficiently rigid
40、 toprevent their distortion during shearing. The various parts ofthe shear device shall be made of material not subject tocorrosion by moisture or substances within the soil, forexample, stainless steel, bronze, or aluminum, etc. Dissimilarmetals, which may cause galvanic action, are not permitted.6
41、.2 Shear Box, a shear box, either circular or square, madeof stainless steel, bronze, or aluminum, with provisions fordrainage through the top and bottom. The box is divided by astraight plane into two halves of equal thickness which arefitted together with alignment screws. The shear box is alsofit
42、ted with gap screws, which create the space (gap) betweenthe top and bottom halves of the shear box prior to shear. Thetwo halves should provide a bearing surface for the specimenalong the shear plane during relative lateral displacement.6.2.1 The minimum specimen diameter for circular speci-mens, o
43、r width for square specimens, shall be 2.0 in. 50 mm,or not less than ten (10) times the maximum particle sizediameter, whichever is larger.6.2.2 The minimum initial specimen thickness shall be 0.5in. 13 mm, but not less than six (6) times the maximumparticle diameter.6.2.3 The minimum specimen diam
44、eter to thickness orwidth to thickness ratio shall be 2:1.NOTE 3Alight coating of grease applied to the inside of the shear boxmay be used to reduce friction between the specimen and shear box.TFE-fluorocarbon coating may also be used on these surfaces instead ofgrease to reduce friction.6.3 Porous
45、Inserts, Porous inserts function to allow drain-age from the soil specimen along the top and bottom bound-aries. They also function to transfer shear stress from the insertto the top and bottom boundaries of the specimen. Porousinserts shall consist of silicon carbide, aluminum oxide, ormetal which
46、is not subject to corrosion by soil substances orsoil moisture. The proper grade of insert depends on the soilbeing tested. The hydraulic conductivity of the insert should besubstantially greater than that of the soil, but should be texturedfine enough to prevent excessive intrusion of the soil into
47、 thepores of the insert. The diameter or width of the top porousinsert or plate shall be 0.01 to 0.02 in. (0.2 to 0.5 mm) less thanthat of the inside of the shear box. The insert functions totransfer the shear stress to the soil and must be sufficientlycoarse to develop interlock. Sandblasting or to
48、oling the insertmay help, but the surface of the insert should not be soirregular as to cause substantial stress concentrations in thesoil. Porous inserts should be checked for clogging on a regularbasis.NOTE 4Exact criteria for insert texture and hydraulic conductivityhave not been established. For
49、 normal soil testing, medium grade insertswith a hydraulic conductivity of about 0.5 to 1.0 3 103ft/yr 5.0 3 104to 1.0 3 103cm/s are appropriate for testing silts and clays, and coarsegrade inserts with a hydraulic conductivity of about 0.5 to 1.0 3 105ft/yr0.05 to 0.10 cm/s are appropriate for sands. It is important that thehydraulic conductivity of the porous insert is not reduced by the collectionof soil particles in the pores of the insert. Storing the porous inserts in awater filled container between uses will slow clogging. The inserts can becleaned b
