ASTM_D_7181_-_20.pdf

Designation:D718120Standard Test Method forConsolidated Drained Triaxial Compression Test for Soils1This standard is issued under the fixed designation D7181;the number immediately following the designation indicates the year oforiginal adoption or,in the case of 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.Scope1.1 This test method covers the determination of strengthand stress-strain relationships of a cylindrical specimen ofeither intact or reconstituted soil.Specimens are consolidatedand sheared in compression with drainage at a constant rate ofaxial deformation(strain controlled).1.2 This test method provides for the calculation of princi-pal stresses and axial compression by measurement of axialload,axial deformation,and volumetric changes.1.3 This test method provides data useful in determiningstrength and deformation properties such as Mohr strengthenvelopes.Generally,three specimens are tested at differenteffective consolidation stresses to define a strength envelope.The stresses should be specified by the engineer requesting thetest.A test on a new specimen is required for each consolida-tion stress.1.4 If this test method is used on cohesive soil,a test maytake weeks to complete.1.5 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.1.6 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.6.1 The procedures used to specify how data are collected,calculated,or recorded in this standard are regarded as theindustry standard.In addition,they are representative of thesignificant digits that generally should be retained.The proce-dures used do not consider material variations,purpose forobtaining the data,special purpose studies or any considerationfor the users objectives;and it is common practice to increaseor reduce the significant digits of the reported data to becommensurate with these considerations.It is beyond the scopeof this test standard to consider significant digits used inanalysis methods for engineering design.1.7 UnitsThe values stated in SI units are to be regardedas standard.The inch-pound units given in parentheses aremathematical conversions,which are provided for informationpurposes only and are not considered standard.Reporting oftest results in units other than SI shall not be regarded asnon-conformance with this test method.1.7.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units.In this system,the pound(lbf)represents a unit of force(weight),while the unit for massis slugs.The slug unit is not given,unless dynamic(F=ma)calculations are involved.1.7.2 It is common practice in the engineering/constructionprofession to concurrently use pounds to represent both a unitof mass(lbm)and of force(lbf).This implicitly combines twoseparate systems of units:that is,the absolute system and thegravitational system.It is scientifically undesirable to combinethe use of two separate sets of inch-pound units within a singlestandard.As stated,this standard includes the gravitationalsystem of inch-pound units and does not use/present the slugunit for mass.However,the use of balances or scales recordingpounds of mass(lbm)or recording density in lbm/ft3shall notbe regarded as non-conformance with this standard.1.7.3 The terms density and unit weight are often usedinterchangeably.Density is mass per unit volume whereas unitweight is force per unit volume.In this standard density isgiven only in SI units.After the density has been determined,the unit weight is calculated in SI or inch-pound units,or both.1.8 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety,health,and environmental prac-tices and determine the applicability of regulatory limitationsprior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.1This 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 Jan.1,2020.Published February 2020.Originallyapproved in 2011.Last previous edition approved in 2011 as D7181-11.DOI:10.1520/D7181-20.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West