1、Designation: D2774 12An American National StandardStandard Practice forUnderground Installation of Thermoplastic Pressure Piping1This standard is issued under the fixed designation D2774; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, 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.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONIn general, thermopl
3、astics pressure piping materials behave as ductile materials under load, meaningthat they can undergo considerable deformation without damage. Piping made from such materials hasthe ability to bend under a load without breaking and to deform in other ways, while offering continuedresistance. This fl
4、exibility allows ductile thermoplastic pipe to activate through pipe deformationlateral soil forces which create a pipe/soil system capable of safely supportingeven in pipes subjectto little or no internal pressurethe earth and superimposed loads which are encountered in most pipeinstallations. Howe
5、ver, proper installation techniques are required to ensure that the necessary supportat the bottom and passive soil pressures at the sides of the pipe are developed and maintained.Soils in which trenches are dug shall be examined and identified and the trenches prepared andbackfilled in accordance w
6、ith sound bedding procedures and this practice.1. Scope*1.1 This practice governs procedures and references ASTMspecifications for underground installation of thermoplasticpressure piping, 63-in. (1372-mm) nominal size and smaller. Itis beyond the scope of this practice to describe these proce-dures
7、 in detail since it is recognized that significant differencesexist in their implementation depending on kind and type ofpipe material, pipe size and wall thickness, soil conditions, andthe specific end use.1.1.1 This practice assumes that over the range of antici-pated operating conditions, includi
8、ng maximum external load-ing and minimum internal pressure, the soil/pipe system willoffer sufficient structural stability to resist possible excessivediametrical deformation, or even collapse. In cases, particu-larly with large diameter thinner-walled pipe, for which thevalidity of this assumption
9、may be in question, the selection ofpipe and recommended installation conditions shall be deter-mined by a qualified engineer.1.1.2 Specific pipe characteristics and end-use requirementsshall dictate addition to, or modification of the proceduresstated or referenced herein.1.2 The values stated in i
10、nch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
11、 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. Specific precau-tionary statements are given in Sections 10 and 11.2. Referenced Documents2.1 ASTM Standards:2D1600 Terminolo
12、gy for Abbreviated Terms Relating toPlasticsD2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)E11 Specification for Woven Wire Test Sieve Cloth and TestSievesF412 T
13、erminology Relating to Plastic Piping Systems1This practice is under the jurisdiction of ASTM Committee F17 on PlasticPiping Systems and is the direct responsibility of Subcommittee F17.61 on Water.Current edition approved Feb. 1, 2012. Published March 2012. Originallyapproved in 1969. Last previous
14、 edition approved in 2008 as D2774 08. DOI:10.1520/D2774-12.2For 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.1
15、*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.F1668 Guide for Construction Procedures for Buried PlasticPipe2.2 AWWA Standard:C 651 Standard for Disinfecting Water Ma
16、ins33. Terminology3.1 Definitions:3.1.1 Definitions are in accordance with Terminology F412,unless otherwise specified. Abbreviated terms are in accor-dance with Terminology D1600. Installation terminology usedin this practice is illustrated in Fig. 1.3.1.2 The term pipe refers to both pipe and tubi
17、ng, unlessspecifically stated otherwise.3.1.3 protective sleeve, na short section of pipe installedover system piping where there is a transition from relativelyrigid piping or structure to relatively flexible piping or structureto protect the transition region from excessive bending or shearstresse
18、s. For example, protective sleeves are installed atconnections between plastic or non-plastic mains and plasticlateral branch or service lines (such as service or branchconnections to tapping tees or saddles), where plastic pipeenters or exits a casing, or where plastic pipe penetrates abuilding or
19、vault wall.4. Significance and Use4.1 This practice may not apply to products which shall besubject to failure at relatively low strains. For low ductilitymaterials, the installed pipe/soil system shall be sufficientlyrigid to prevent pipe deformations which could strain thepiping material beyond it
20、s safe strain limit.5. Joining5.1 Plastic pipe shall be joined together or to other pipes ofdissimilar material using a number of different techniques.Commonly used procedures, joining materials, and fittings aredefined by various standards. (See Appendix X1.) The tech-nique used shall be suitable f
21、or the particular pipes beingjoined to one another. Manufacturers shall be consulted forspecific instructions not covered by existing specifications.When requesting information, the intended service applicationshall be made known.5.2 Skill and knowledge on the part of the installer arerequired using
22、 recommended techniques to obtain qualityjoints. Training of new installers shall be made under theguidance of skilled individuals. Detailed written proceduresand visual aids used to train personnel are available frompiping and joining equipment manufacturers.5.3 The use of fittings and joining proc
23、edures which are notcovered by a recognized standard is subject to the judgmentand discretion of the purchaser. Each fitting and joiningprocedure used shall be qualified by investigation, testing, andexperience to establish its suitability and safety for the intendedservice. Fittings and joints shal
24、l have long-term pressurecapabilities equal to or greater than the systems maximumanticipated sustained operating pressure.5.3.1 Thrust transmitting joints such as heat fused or solventcemented, shall be capable of restraining maximum anticipatedpipe pull-out forces generated by any unbalanced force
25、s frominternal pressure or pipe expansion/contraction, or both.5.3.2 Gasketed and other non-thrust transmitting joints shallbe restrained by means of properly engineered external re-straints (thrust blocks) or joint restraint devices (see 7.3).NOTE 1Where there are unbalanced momentum forces and thr
26、ust istransmitted through the joints, consideration shall be given to the designcapacity of each joint in the system to safely resist maximum anticipatedaxial thrust (see 7.3). Where a piping section having thrust transmittingjoints is connected to a piping section having non-thrust transmittingjoin
27、ts, measures shall be taken to anchor or restrain the end of the thrusttransmitting joint section against longitudinal movement so that contrac-tive forces shall not be transmitted and cause disjoining of non-thrusttransmitting joints.6. Trenching-Recommended Installation Procedure6.1 Trench Stabili
28、tyDuring trench excavation, ensure thatthe trench sides shall be stable under all working conditions.The trench walls shall be sloped or appropriate supportsprovided to comply with all applicable local, state, and federalrequirements for safety.6.2 Trench WidthThe width of the trench at any pointbel
29、ow the top of the pipe shall be sufficient to provide adequateroom for each of the following requirements: (1) joining thepipe in the trench if this is required; (2) snaking of small-diameter, heat fused or solvent cemented pipe from side-to-sidealong the bottom of the trench, when the effects of co
30、ntractionare not otherwise accommodated; (3) filling and compactingthe side fills; and (4) checking the elastomeric seal joints.Minimum trench widths shall be permitted to be utilized withmost solvent-cemented and heat-fused pressure pipe materialsby joining the pipe outside the trench and lowering
31、the pipeinto the trench after adequate joint strength has been attained(see 10.5). This practice shall be permitted to be used forgasket joint pipe, with manufacturers approval, providing careis taken to not disassemble the joints during lowering.3Available from American Water Works Association (AWW
32、A), 6666 W. QuincyAve., Denver, CO 80235, http:/www.awwa.org.FIG. 1 Installation TerminologyD2774 1226.3 Trench BottomThe trench bottom shall be preparedfor the direct replacement of the pipe and shall be continuous,relatively smooth, free of rocks, and provide uniform support.For bell-ended or coup
33、led pipe, suitable “bell-holes” shall beprovided at each joint to permit the joint to be assembled andthe pipe to be supported properly.6.3.1 Where ledge rock, hardpan, or boulders are encoun-tered, it shall be required to pad the trench bottom with abedding of at least 4-in. (100-mm) thickness of c
34、ompactedClass I or II material (see Table 1). In situations where rapidmovement of water takes place through this bedding, the ClassI or II material used shall have gradation that prevents loss bymigration of any pipe embedment material (see 9.8).6.4 Trench Depth and Pipe CoverExcavation for pipetre
35、nches shall be to the lines, grades, and dimensions shown onthe contract drawings. Sufficient cover shall be maintained toadequately reduce the traffic or other concentrated and impactloads.6.4.1 Reliability and safety of service shall assume majorimportance in determining minimum cover for any inte
36、ndedservice. Local, state, or federal codes shall also govern. Pipeintended for winter water service shall have a minimum coverequal to or greater than the maximum expected frost penetra-tion depth.6.4.2 Aminimum cover of 24 in. (610 mm) for pipe shall berequired when subjected to heavy overhead tra
37、ffic. In areas oflight overhead traffic a minimum cover of 12 to 18 in. (305 to457 mm) is required.6.5 “Trenchless InstallationSome types of thermoplas-tic pressure pipe shall be permitted to be installed usingmethods that do not require excavation.7. Pipe Placement7.1 Pipe Joint AssemblyPipe assemb
38、ly shall be conductedin accordance with the manufacturers published recommen-dations. Above ground joining of pipe joined by solventcementing, heat fusion or some other thrust transmittingconnection shall be permitted. After the joint is appropriately“cured” (see Section 10) the pipe is lowered into
39、 the trench.This practice shall be permitted to be used for gasket joint pipe,with manufacturers approval, providing care is taken to notdisassemble the joints during lowering.7.2 Pipe BendingAssembled thermoplastic pipe may bebent longitudinally if the bending radius is within limitsprescribed by t
40、he manufacturer. There shall be two limits, onefor pipe without joints and the other for pipe sections withjoints.7.3 Thrust RestraintWhen installing piping systems withjoints that cannot transmit the anticipated maximum longitu-dinal thrust, thrust restraint shall be required at changes indirection
41、, or terminal ends, to prevent joint disengagement.7.3.1 Where the piping system employs non-self restrainingjoints (for example, elastomeric seal bell and spigot type joints)at points where line shift or joint separation at system operatingpressure can be anticipated, that is, pump discharge, direc
42、tionalchanges, reducers and dead ends, thrust restraint shall berequired to prevent joint disengagement and ensure the properperformance of the pressure piping system.7.3.2 Where the piping system employs self-restrainingjoints (for example flanges, heat fusion, mechanical jointrestraint or solvent
43、cement joints) at these points in the system,thrust blocking shall not be required for thrust restraint.7.4 Thrust Restraint MethodsThrust restraint shall beachieved by use of mechanical thrust restraint devices or by useof concrete thrust blocking.7.4.1 Mechanical Thrust Restraint Devices:7.4.1.1 D
44、evices used for thrust restraint of PVC pipe shallconform to Standard F1674.7.4.1.2 Consult device manufacturer for design assistance.7.4.2 Cast In Place Concrete Thrust Block Construction:TABLE 1 Soil ClassesAClass I crushed rockB,C100% passing 1-12-in sieveD, # 15% passing #4 sieve,# 25% passing38
45、-in sieve, # 12% passing #200 sieveClass II clean, coarse grained soilsEGW, GP, SW, SPor any soil beginning with one of these symbols(can contain fines up to 12%)uniform fine sands (SP) with more than 50% passinga #100 sieve should be treated as Class III materialClass III coarse grained soils with
46、fines GM, GC, SM, SCor any soil beginning with one of these symbolssandy or gravelly fine grained soils ML, CLor any soil beginning with one of these symbolswith $ 30% retained on #200 sieveClass IV fine-grained soils or any soil beginning with one of these symbolswith # 30% retained on #200 sieveML
47、, CLClass V fine-grained soils, organic soils high compressibility silts and clays,organic soilMH, CH, OL, OH, PtASoil classification descriptions and symbols are in accordance with Practice D2487 and D2488.BFor Class I, all particle faces shall be fractured.CSee section 9.6 for additional restricti
48、ons on Class 1 material maximum particle size.DSieves and sieve cloths shall be in accordance with Specification E11.EMaterials such as broken coral, shells, slag, and recycled concrete (with less than 12% passing a No 200 sieve) should be treated as Class II soils.D2774 1237.4.2.1 The thrust block
49、shall be constructed of cast in placeconcrete having a compression strength of 2000 psi (14 MPa)or more. Precast concrete blocking, wood blocking, or stoneblocking with wood wedges, are not acceptable.7.4.2.2 The thrust block acts as an anchor between pipe orfitting and the solid trench wall. The size of the thrust blockshall be adequate to prevent pipe movement at the point ofthrust. Consult the system designer.7.4.2.3 The thrust block cavity shall be hand dug intoundisturbed soil and framed, with soil or wood to hold freshlypoured concrete. The earth bearing
