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HDPEDOUBLE-WALL CORRUGATED PIPE ENGINEERINGTECHNIQUEMANUAL

LESSO

ABOUT LESSO GROUP

Establishedin986,LESSO(StockCode:28K)isagobaladerinomefuishingsandbildingmaterials.eGroup’sbsine portfoliospanspstcningatlsdefungotalprotectirgplicea andothers.Itersidngeofproductsschseotoolasmbndiaryaretegraliatlsa doorsandwdfokadartsodsaterpurifiesaterroingmateralsdaantsfirefihtint valvesablsoai LESSO’s sales revenue reached over USD 4.38 billion.

Sinceimplementingastrategofglobaizationndexpandingitsgoalpresence,LESSOsevoledintasphisticatedmutiatialIt boastsmoretadaedroductiosdidodengisusralndstostorsiarthcao AmericaEuroricasbiditoctdfosdi its continuously improved strategic layout in a timely and efficient way.

LESSOhasfoddits&teritrea0tiearstilidteiseetdt post-doctoralworkstatiostospportitsinovatioandtechicaldevelomentTeGroupastakenaladingolentherevisioofoer internationalndnesedustradadsEserpatentsmeoftrepding)ndprideserti ofproducts,aingiteoftostcomprehensivemanfacturersinteipingindustryItsproductsareutlidbalyidiea includinghooaticivistructiociaaterlyegagetrlydeecoatio gas supply,fire-fighting,environmental protection,agriculture,oceanic aquaculture,etc.

Truetoitsideaof“EvisioingteBettr，BuilingtheFuture”,ESSOremainscommittedtoceatingabeterlivingenvirontand advocatinltsif insustaining healthyand beautiful space so that global residentscould enjoya comfortable life.

CohesionandDrivers for Progress

JOINHANDS,FORGEAHEAD

ChinaLessoGroupHoldingsLimited(StockName:ChinaLesso,StockCode:0128.HK)isalargeindusrialgroupofhomefuisings andbuildingmaterialsinChina.ChinaLesso’sbusinessportfoiospansplasticpipingbuildingmaterialsandhomefurishings, environmental protection,new energy,supply-chain service platforms and others.

Contents

HDPEDOUBLE-WALL CORRUGATED PIPE TECHNICALSPECIFICATIONS

Foreword 01

I.Product Introduction 01
1.Product Features. 01
2. Applications 01
3.Product Specifications and
Performance Indicator.. \*·1 02-03
4.Pipe Connection 04

II. HDPE Double-wall Corrugated Pipe 05 for Underground Drainage
1.Performance Feature.. 05
2. Piping System Design.. 06-10
3. Piping Construction.. " 11-14
Repairof Damaged HDPEDouble-wall
Corrugated Pipe.. 15
Comparison of HDPE Double-wall
Corrugated Pipe and Concrete Pipe 16

LESSO

Foreword

HDPEdoublalgadipresivesedcsoctoinvelodntrartirlinnidad JapanandEreodiiadat ventlationaloidiasctsodd stiffness requirements,a double-wall corrugated structure achieves material savings of 30 % to 50 % ,Additionally, HDPE double-wall corrugated pipes outperfordspd ideal alternatives to traditional piping materials.

ManufacturedfrogesitlyetetoughetrusiooingurHublallougadipemplitttioaadd GBT19472.essusoao andofsaeldosada since they incorporateaspecialized hollow ringstructure.

Timaalidietdddo ourroductssrdableddltd standards,specifications,or regulatory requirements.

I. Product Introduction

Product Features

1Higigtfs:cfdgdtfil excellent flexibility,strong compression
2.Lowflowresistance:Smoothinnerwalsofthepipeminimizefluidfictionalresistance,enablinghigherwatercayingcapacity.
3.Goodsealingperformance:Elasticgasketpush-onconnectionensureseasyinstalationandreliablehermeticsealingintegrity.
4.Ecelenistosal outperform concrete pipes in corrosion resistance.
5.Easyonltsppmtaabift foundations,making the construction convenient and simple.
6.Longservice life:Excellentwearresistanceand high impactresistancecontribute toprolonged operationalifespan.
7.Lowmaterial waste and comprehensivecost: The constructioncost of HDPE double-wallcorrugated pipes is 30 % to 40 % lower than that of concretepipes with socket-and-spigot joints,ensuring shorterconstruction periodsand significanteconomic benefits.

Applications

1.Underground buried rainwaterand sewage discharge systems in municipal engineering projects and residential quarters;
2.Irrigation water conveyance and stagnant water drainage systems in farmlands;
3.Drainage systems in wastewater treatment plants and waste treatment facilities;
4.Chemical ventilation pipes and fluid transport in the chemical processing and mining operations;
5.Asprotective casings for communication cables,etc.

LESSO

Product Specifications and Performance Indicators

Product Specifications:

HDPE Double-wall Corrugated Pipe Fittings (Manually Fabricated Welded Fittings)

LESSO

Structural Diagram of HDPE Double-wallCorrugatedPipe

LESSO

Pipe Connection

1.Rubber Gasket Connection for Socket End Pipes

InstallationPrecautions:

The rubber gasket should be placed in the first corrugated groove of the pipe’s spigot end.

The pipe should be installed with the socket end facing upstream and the spigot end facing downstream.Proceed the installation from downstream to upstream.

For pipes with a diameter of DN400mm or less,a transversebaffleplateshouldbeinstalledatthecenterof the pipe end,and usea crowbaragainst the baffle plate for gradual insertion to designated position. For pipes with a diameterabove DN4oomm,useamanual lever hoist or other equivalent tools for gradual socket insertion.When closing the joint,maintain simultaneous operation of the hoist on both sides of the pipe during joint closure to ensure that the rubber gasket is properly positioned without distortion or detachment.

To prevent the pipe axis from shifting during joint closure, pipe stabilization measures should be implemented. Sandfilled woven bags can be placed on top of the installed pipes to secure them in place.After installing the pipe joints,post-installation verification of pipe elevationand alignment shall be conducted to meet the design requirements.

Installation Steps:

2.Straight Pipe and Coupling Connection Installation Steps:

LESSO

II. HDPE Double-wall Corrugated Pipe for Underground Drainage

Performance Features

·Advanced material,well-designed structure，high strength， strong pressureresistance，and excellent crackresistance

·Rubber gasket socket-and-spigot connectionfacilitatesreliableinstallation.

·Corrosion resistance toacids,alkalis, andvariouschemicalmedia

Smooth inner wall,highflow capacity，and reduced diameter requirementsforequivalentflowrates ·Lightweight for easy transportation and installation

Competitive overall project costs comparable to thatof the cement pipe

Pipe laying typicallyrequiresno concretebedding，enablingfaster construction.

·Resistance to leakage,and environmentally friendlywithan internal working pressure of 0.05MPa

·Flexible joints with strong resistance tounevensettlement

·Extended service life exceeding 50 years

·Scale-resistant pipe interior ensures near-zero cleaning or dredging.

LESSO

Management System Design

1、Design

1.1 General Design

1.1.1Theptdafsidedmpictssld waterlevel,dodrgodtdkdi

1.1.2Plasticdrainaeppesoudbeidinstraghtligmentseagdoruredlgmentseeqiedundespeciacicmstanste maximumallowabledefletionangleofthepipejointandtheminimumalowablebendingradiusofthepipeshouldcomplywiththeelevant national standards.

1.1.3The design service life of plastic drainage pipes should be at least 50 years.

1.1.4Thestructuraldesignofplasticdrainagepipesshouldbecalculatedandverifiedaccordingtothefolowing twolimitstates: aForulimateliiatetaoddttrgthrctutclisabit' anti-floating stability. b.For serviceability limit state,the pipe’s ring section deformation should be checked.

1.1.5Plastiaodsifressregravityfdteiructuraaatiossoddcted flexible pipe design theory.

1.1.6 The calculated central angle (2α) for arc shaped soil/sand bedding of the pipe shallbe reduced by 3 0 ^ { \circ } from the designed central angle.The designed central angle forarc shaped soil/sandbeddingshould notbe less than 1 2 0 ^ { \circ }

1.1.7Thebeddingforidpipessalloteedfolasticanagepips.igidpilssoudeverdirectlysupportplasticdragipes.

1.1.8Fplatgslodoeeprotetisigtructureoceepotectiructureoudeaas Continuous and full-length pipe encasement from one manhole to the next is required.

1.2 Pipe Layout

1.2.1Thepostioningofplasticdrainagepipesinelationtotherundergroundpipelines,buildings,andstructuressouldmtthe following requirements: a.The installation and maintenance of the pipes should not cause interference to other systems. b.Damagetoplasticdrainagepiesshouldnotaffctthefoundationsofarbyuildingsorstructures,orcontaminatedriningate c.Plastic drainage pipes should notoverlapother engineering pipes in vertical direction for direct laying. d.Plastic drainage pipes should not cross beneath the foundations of buildings or large structures.

1.2.2Plasticdrainagepipessouldbelaidelowthesoilfrezingline.Tesoicoverthicknessabovethepipesouldeatleasteters beneath pedestrian walkways,and at least O.7 meters beneath roadways.

1.2.3Theminimumpipediameterandthecorrespondingminimumdesinslopeformunicipalplasticdrainagepipesoutsideresidential areasshouldcomplywiththespecificationsinTable1.2.3-1.Likewise,theminimumpipediameterandthecorrespondingminimum designlopeforplasticdrainagepipes insideresidentialareas should complywith thespecifications inTable1.2.3-2.

1.2.4The plasticdrainagepipesystemshould include manholes.Manholesshouldbeinstaledatpipejunctions,changesinpipe directioneraisinmetedotndtrtaitelsorhtictisicing between manholes along straight pipe sections should comply with the specifications in Table 1.2.4.

LESSO

1.3Hydraulic Calculation

1.3.1Theflowvelocityand the discharge in plastic drainage pipes can be calculated usingthe following formula:

Where:Q- Discharge(m/S); n--Pipe wall roughness coefficient; A--Wet cross-sectional R -Hydraulic radius （m）; area(m)； I --Hydraulic slope. U -Flow velocity(m/s);

1.3.2Theelectiooftppewallrougsfict(forplasticdranagepessoldeteridtougompresialyis ofexperimentaldatawithvaluesrangingfromOo9to.011.Ifnoexperimentaldataisvailable,avalueofO.011shouldbesed.

1.3.3The maximum design flow velocity for plastic drainage pipes should not exceed 5 . 0 { m / s } The minimum design flow velocity for sewage pipes should not be less than 0 . 6 \mathsf { m / s } under design depth ratio.For rainwater and combined drainage pipes,the minimum design flow velocity should be at least 0 . 7 5 { m / s } under full flow conditions.

1.4、Load Calculation

1.4.1Thestandardverticalsoilpressureonthetopoftheplasticdrainagepipecanbecalculatedusingthefollowingformula:

Where: q _ { s \nu , k } Standard vertical soil pressure on pipe top per unit area ( k N / \mathsf { m } ^ { 2 } ) （204号 γ _ { s } —Gravity density of backfill soil can be taken as 1 8 \mathsf { k N / m } ^ { 2 } γ ^ { \prime } —Gravity density of soil cover within underground water range can be taken as \uparrow 0 \mathsf { k N } / \mathsf { m } ^ { 3 } （204号 \boldsymbol { γ } _ { \boldsymbol { w } } 一 -Gravity density of underground water can be taken as \uparrow 0 1 x N / \mathsf { m } ^ { 3 } 5 Hs—Depthof soil cover on pipe top (m); Hw—Depth of underground water above pipe top (m).

1.4.2Variableaction loadsonplasticdrainagepipesshould includegroundvehicle loadsand heaped loadsactingonthepipes. Vehicleloadsandheapedloadsshouldnotbeconsideredsimultaneouslyandtheloadwithgreaterefectshouldbeselected. The vehicle load level should be determined based onactual traffic conditions.

.4.3Thestandardverticalpressuretransferrdtothetopoftheplasticdrainagepipefromthegroundvehicleoadcanbedetermined as follows (the quasi-permanent value coefficient can be taken as \Psi _ { \mathfrak { q } } = 0 . 5 \} =

1.4.3.1Thestandardverticalpressuretransferredtothepiptopfromasingletireload(refertoFigure.43.1)canbecaculatedusing the following formula:

Figure1.4.3.1 DistributionofPressureTransferred froma Single VehicleTire

1.4.3.2Fortwoormoresingeotirelads,thecombinedeffectransferedtipetopanbecaculatedasfollos(gur432)：

Figure1.4.3.2DistrbutionofCombinedEffectofTwoorMoreSingle-rowTireLoadsTransferedfromGround Vehicles

(a)Pressure Distribution Along Tire Contact Width Direction

(b)Pressure Distribution Along Tire Contact Length Direction

Where: q _ { \nu k } 一 Standard vertical pressure per unit area transferred from ground vehicle load to the pipe top ( k N / \mathsf { m } ^ { 2 } ) （204号 \mu _ { d } Dynamic coefficient of vehicle load can be determined according to specified values in Table 1.4.3.2-1 of this manual; Q _ { \nu k } 1 一Standard single-tire load of the vehicle (kN); a 一 Single tirecontact length;

b Single tire contact width (m); （204号 n Number of tire loads; d _ { j } Net distance betweenadjacent tre loads ( \mathsf { m } )

1.4.4Thestandard ground heaped load qvk can be takenas style 1 0 \ k N / \mathsf { m } ^ { 2 } ,withaquasi-permanentvaluecoefficient \Psi _ { { q } } = 0 . 5

1.5、UltimateLimitStateCalculation

1.5.1Whencalculatingtheingsectionstrengthofplasticdrainagepipesundertheultimatelimitstate,thebasicloadcombination should be used, with all loads adopting design values.

1.5.2Uderexternalpressreloads,themaximumringsection(tensile)compresivestressdesignvalueof theplasticdrainage pipe should not exceed the design value of the (tensile) compressive strength. The calculation of the pipe’s ring section strength should folow the limit state expression below:

Where:

\sigma 一 Maximum ring (tensile) compressive stress design value (MPa) of the pipe; \boldsymbol { γ } _ { 0 } ——Importancecoeficientof pipes,1.0forsewage pipes including combined drainage pipes); O.9 for rainwater pipes; f （204号 Ring bending (tensile) compressive strength design value ( \mathsf { M P a } ) of the pipe.

1.5.3Themaximumringbending stressdesignvalueforplasticdrainagepipescanbecalculatedusing thefolowing formulas:

(1.5.3-1-1)

(1.5.3-1-2)

Where: D _ { { f } } —— Form coefficient shall be determined according to the specified values in Table 1.5.3 of this manual;

（204号 K _ { { d } } Pipedeformationcoefient shallbedeterminedinaccordance withthe provisions specified in Table 1.6.2 of this manual based on the calculated central angle 2α of the arc shaped soil bedding;
D _ { \circ } — Pipe calculation diameter ( m ) ;
D—Outside diameter of the pipe (mm);
（20 S _ { \mathfrak { p } } ——Pp ring stifnes ( k N / \mathsf { m } ^ { 2 } ) ；
（20 { { y } } _ { { o } } —Distancefromthepipewallneutralaxisttepipeouteral ( \mathsf {mm } )
E _ { { p } } — Pipe elastic modulus ( \mathsf { k N / \mathsf { m } } ^ { 2 } )
（204号 I _ { \mathfrak { p } } 一Moment of inertia of the pipe wallper meter of te longitudinal section of the pipe ( \mathsf {mm } ^ { 4 } )
（204号 E _ { { d } } — Combined deformation modulus of the soil around the pipe ( \mathsf { k N } / \mathsf { m } ^ { 2 } ) shall be determined by testing or based on relevant standards if without testing (
γ _ { G } # Partial coefficient of soil cover load on pipe top shall be taken as 1.27;
γ _ { \varrho } -Partial coefficient of ground load on pipe top shal be taken as 1.40;
qsvk Standard vertical soil pressure on pipe top per unit area ( \mathsf { k N / } \mathsf { m } ^ { 2 } ) shall be calculated by the formula (refer to 1.4.1-1);
\boldsymbol { q } _ { \nu , k } -Standard vertical pressure from ground vehicle or heaped loads transmitted to pipe top per unit area ( { \mathsf { k N } } / { \mathsf { m } } ^ { 2 } ) shall be adopted as defined in Section 4.3 and Section 4.4 of this manual;
\sigma _ { c r } Maximum ring bending tensile stress design value for pipe wall ( \mathsf { k N / \mathsf { m } } ^ { 2 } )

1.5.4Thebucklingstabityofplasticdrainagepipesectionsshouldbecalculatedbasedntheadversecombinationsofvariousctions. All actionsshalladopt standard values,and thering stabilityresistancecoeficientKS shouldbeatleast 2.0. 1.5.5Underexteralpressure,theringstabilitycalculationforthepipewallsectionsshould meetthefolowingrequirement:

Where: F _ { c r , k } Standardcicalpressurefortepipewall instability ( { \mathsf { k N / } } { \mathsf { m } } ^ { 2 } ) can be calculated by the formula (refer to 1.5.7) of thismanual; （20 F _ { \nu , k } Standardverticpresuretheipfo various actions ( { \mathsf { k N / } } { \mathsf { m } } ^ { 2 } ) can be calculated by the formula (refer to 1.5.6) of this manual; K—Ring stability resistance coeficient of the pipe.

1.5.6Thestandardvalueoftheadversecombinationofverticalactiononthetopoftheplasticdrainagepipecanbecalculated accordingtothefollowingformula:

1.5.7The standard critical pressure of the pipe wallinstability for the plastic drainage pipe can be calculated using the following formula:

Where: （20 F _ { c r , k } Standardcrtialpressue forpipe wall instability ( { \mathsf { K N } } / { \mathsf { m } } ^ { 2 } ) ：5 Vp— Poisson’s ratio for the pipe can be taken as 0.4 for thermoplastic pipes; （20 \xi —Instabity calculation coefficient for the pipe wall can be taken as 5.66; （204号 S _ { \mathfrak { p } } （20号 Pipe ring stiffness ( 1 < N / \mathsf { m } ^ { 2 } ) （204号 E _ { { d } } 一 Combined deformationmodulus of the soil around the pipe ( { \mathsf { k N } } / { \mathsf { m } } ^ { 2 } )

1.5.8Forplasticdrainagepipesburiedbelowthegroundwaterlevelorundergroundwaterlvel,theantifloatingstabiltofthe pipe structure should be calculated based on design conditions,with allactions adopting standard values.

1.5.9The anti-floating stability of the plastic drainage pipe should meet the following requirements:

(1.5.9-1)

Where:

FGkStandardvaueofpermanentanti-floatingactions (kN);
∑Fsw—Sumofstandardself-weightofthesoillayersabove the underground water level (kN);
￡ \boldsymbol { F ^ { * } } _ { s w , k } 1 1 Sum of standard vertical action from below underground water level to the pipe top (kN); Gp—Standard self weight of the pipe (kN); F _ { f w , k } — Standard buoyancy force shal be equal to the product of the pipe’s actual displaced volume and the density of the underground water (kN); K _ { f } ——The anti-floating stability resistance coefficient for the pipe can be taken as 1.10.

LESSO

1.6ServiceabilityLimitStateCalculation

1.6.1Theloadcombination fortheingsectiondeformationcheckoftheplasticdrainagepipeshouldbecalculatedaccording to the quasi-permanent combination.

1.6.2Under external pressure,the vertical deformation of the plastic drainage pipe canbecalculated using the following formula:

Where : w _ { d , \operatorname* { m a x } } Maximumverticaldeformationofthepipeunderthecombinedeffect ( \mathsf {mm } ) （204号 K _ { d } —Pipe deformationcoeficient shallbedeterminedbasedon thecalculatedcentralangle 2αofthepipe beddingconditions, as specified in Table1.6.2 of thismanual; （204号 q _ { s \nu , k } —Standard vertical soil pressure on the pipe top per unit area ( \mathsf { k N / m } ^ { 2 } ) shall be calculated according to the formula (refer to 1.4.1-1); （204号 q _ { \nu k } —Standard vertical pressure from ground vehicle or heaped loads transferred to pipe top perunit area ( { \mathsf { k N } } / { \mathsf { m } } ^ { 2 } ) shall be adoptedas defined in Sections1.4.3andSection1.4.4 of thismanual; DDeforatioeectfteaket5sdpactfthpip haunching backfill; （204号 \Psi _ { q } Quasi-permanent value coeficient for variable loadscan be taken as 0.5; （204号 S _ { p } ——Pipe ring stiffness ( { \mathsf { k N } } / { \mathsf { m } } ^ { 2 } ) E _ { d } Combined deformation modulus of the soil around the pipe ( { \mathsf { k N / } } { \mathsf { m } } ^ { 2 } ) shall be determined by testing or based on relevant standards if without testing data; （204号 D _ { 1 } Outside diameter of the pipe (mm).

1.6.3Underexternalpressureloads,theverticaldiameterdeformationrateoftheplasticdrainagepipeshouldnotexceedthe allowable deformation rate of the pipe, [ \boldsymbol { \rho } ] = 0 . 0 5 .The requirement should satisfy the formula below:

Where: \rho Vertical diameter deformation rate of the pipe; []—Allowable vertical diameter deformation rate of the pipe; Wd Long-term vertical deflection of the pipe under external pressure (mm) can be calculated according to the formula (refer to 1.6.2-1); （204号 D _ { \circ } （204号 Calculated diameter of the pipe (mm).

1.7 Backfill Design

1.7.1The bedding ofthe plastic drainage pipe should be constructed with medium-coarsesand orfine crushed stone.The dimensionsof thearc shaped soilbeddingabove the pipe botom should be determined bythe pipe structurecalculation. Thethicknessof theartificialarcshapedsoil bedding belowthepipebottomcanbecalculated using thefollowing formula, andshouldnotexceed 0.3meters:

Where: h _ { d } ——Thickness of the artificial arc shaped soil bedding below the pipe bottom ( \mathsf { m } ) DNNominal diameter of the pipe ( \mathsf { m } )

1.7.2Thetrenchdesignwidthatthehaunchingcenteroftheplasticdrainagepipeshouldbedeterminedbasedoncomprehensive considerationincudingthepipeingstifess,urroundingsolpropertiesdjacentpipeconditions,backfillsoiltysd constructionconditions.Additionally,thecompactiondegreeofthebackfilsoilshallcomplywithrelevantspecifications.

LESSO

2. Piping Construction

2.1General Regulations

2.1.1Thepipesshouldbelaidontheoriginalsoilfoundationorthecompactedbackfilfoundationatertrenching.Whenthepipearelaid beneath the roadways,the soil cover thickness above the pipes should be at least 0.7 meters.
2.1.2Duringconstructiontemaxiumalowablesooverabovetepipetopsouldbecheckedaccordingtothepiperingstite trenchconditions,andthesuroundingundisturbedsoil.Ifthedesignrequirementsarenotsatisfied,thedesignmayneedtobe modified,or appropriate technical measures should be implemented to ensure the pipe bearing capacity.
2.1.3Whentoottideffetetlstatesdd inside diameter of the casing should be at least 3 0 0 \mathsf {mm } larger than the outside diameter of the pipe.For pipes buried beneath the railways,thecasingdesignshouldcomplywiththerelevantrilwayregulations.Double-walcorrugatedpipesshouldotpasbeeath the foundations of buildings or any structures.
2.1.4Inareaswhereteudergroundaterlvelisigherthanteelevatiooftheexcavationtrenchotom,teundergroundwaterlevel shouldeloweredtoalevelbelowthelowestpointofthetrenchbottm.Throughouteentirepipelayingandbackfilingprocesses thetrenchbotomshouldremain freeofwateraccumulationandfreezing.Lowering theundergroundwaterlevelshouldonlybe discontinuedoncetheprojectisotafectedbygroundwaterthebeddingachievestheeqiredstrengthandthepipesatisiesthe anti-floating requirements.
2.1.5Thetecaliementsforiinostructiongasurementewateriteitrechupportndi processing,shouldcomplywiththecurrentnationalstandards Codefor ConstructionandAcceptanceofWaterandSewerage Pipelines (GB5o268) as well as the technical regulations for drainage pipes in the region.

2.2Trench

2.2.1The net width of the trench botom can be determined based on the local conditions,considering factors such as pipe diameter,soil properties,laying depth,and construction technology.When the pipediameter isno greater than 4 5 0 \mathsf {mm } ,the netwidth on each side of the pipe should be at least 3 0 0 \mathsf {mm } ：whenthepipediameterexceeds 4 5 0 \mathsf {mm } ,the net width on each side should not be less than 5 0 0 \mathsf {mm }

2.2.2When excavating the trench,the bottom elevation should be strictly controled to avoid disturbing theundisturbed soil layer.The undisturbed soil within 0 . 2 { - } 0 . 3 { m } above thedesign bottom elevation shall be manualy cleared to the design elevation before laying the pipe.If over-excavation or soil disturbance occurs,the affected area may be backfilled with 10-15mm natural sand-gravel mixture or crushed stone with maximum grain size < 4 0 \mathsf {mm } .The backfillmaterial shouldbe leveled and compacted to meet the density requirements of the bedding.The use of miscelaneous stones for backfiling is strictly prohibited.Any sharp or hard objects present at the trench bottom must be removedand treatedwithsand-gravelbackfillmaterial.

2.2.3 Dewatering measures should be implemented during trench excavation to prevent the trench bottom from being submerged.

2.3 Bedding

2.3.1Thearcshapedsoilbeddingshouldbeadoptedforpipes.Forgeneralsoilonditions,aomm-thickmedium-coarsesandbeding shouldbelaidontheundisturbedsoilfoundationbeneaththepipebottomoronabackfil-compactedfoundation.Forpoorsoil conditions,a { >=slant } 2 0 0 { \mathsf {mm } } sand-gravel bedding can be used,ora two-layer system maybe adopted:the lower layer of crushed stone with a grain size of 5 - 3 2 \mathsf {mm } and a thickness of 1 0 0 { - } 1 5 0 {mm } ,and the upper layer of medium-coarse sand with a thickness of not less than 5 0 {mm } .The bedding compaction should meet the requirements specified in this manual.Forsoftsoil foundationswhere the bearingcapacityislessthanthedesignrequirementsorwheretheundisturbedsoilisafectedbydewateringorotherfactors,the foundation should bereinforcedtoachieve specified bearing capacitybefore layingthe medium-coarse sandbedding.
2.3.2ThegroeatthsocketandspigotjintssouldbeoncurrntlyexcavatedduringpipelingThelengthwidthanddthofte grooveshouldbedeterminedaccordingtothejoint’sdimensions.Oncetejintingisompleted,thegrooveshouldbebackfiled with medium-coarse sand,and compacted thoroughly.

LESSO

2.3.3Withinthearcshapedsoilbeddinganglesofthepipedesignthehaunchesunderpipemustbbackfiledandcompactedithmedium coarse sand or sand gravel.The backfillrange should not be less than the angle 2α plus 3 0 ^ { \circ } ,and the backfill density should meet the requirements specified in this manual.
2.3.4lnreasreftaliialmntcuetdsrctostudd be reinforced before laying the pipe.

2.4Pipe Installation

2.4.1Beforeloweringteipachsectioftepipemustbvisualispectedinccordaneitproductstandards.ipsatalt meetstandards are strictly prohibited from being laid.
2.4.2Themethodusedtoowerthepipe(manualormechanical)shouldedeterminedbasedothepipedametertrenchtypendalble construction equipment.
2.4.3Rliablelitingequipmentshouldbeusedwhenloweringthepipetoensuresmothplacementintothetenchandtopreventanyharsh contactwithttrenhwalltooiftingpintssuldedndtelitiftee’ollointeosrictlye
2.4.4Forsocketanspiotjintstheocketedsouldfaceupstreamiletespgotendsoudfacedownstreamduringisalio
2.4.5Duringrainyseasoconstructionmeasuresshouldbetakentopreventhepipefromfloating.Ifthepipeisexposedtowateringress afterpipeinstaltionbutbeforecoveringwithsoil,thepipecenterandbottomelevationsshouldberecheckedalongwithavisual inspection.Any displacement, floating,or misalignment should be corrected promptly.

3.Pipe and Manhole Connection

3.1HDPE double-wall corrugated pipes can be directly connected to concrete or brick-built manholes by directly laying them into the brick-built or cast-in-place concrete manhole walls.The corrugated outer surface of the pipe serves asa waterbarrier.

3.2Rubber rings can also be used as a water stop ring to prevent water ingress.

LESSO

4．Backfilling

4.1General Regulations

4.1.1Backfinldfodmeaeltsldorefogststjnresd andthebackfilheightonbothsidesofthepipeandabovethepipetopshouldbeatleast0.5metersTheremainingsectionshouldbe backfilled promptly after satisfactory completion of tightness test.
4.1.2Trenchbackfilingsouldbeperformedsymmetricalyonbothsidesofthepipeandinspectionchambertopreventanylateral movementofthepipesandstructures.Temporarypostion limiting measuresshouldbetakenif necessarytopreventfloating.
4.1.3ManualbackfilingisreqiedfromthebeddingareaoftepipebottmtoO.5metersabovethepipetop.Mechanicalbackfilingwith bulldozers or similar equipment is strictly prohibited.
4.1.4ForbackfilingbeyondO.5metersabovethepipetop,mechanicaleqipmentcanbeusedtosimultaneouslyandevenlybackflland compact from both sides of the pipe axis.
4.1.5Tetredtecflncflegddua frozensoilarenotpermittedforuseinbackfiling.Thebackfilsoilshouldnotcontainstones,bricks,orotherharddebris.
4.16Whenthesteesetpileisusedfortrenchsupport,itanonlyberemovedoncethebackfilnghasreachedtherequiredeightAfter thepileisremoved,thepileoleshouldbepromptlyackfiledandcompacted.Ifsandisusedasthebackfilmateraitcanbe compacted using water.In certain cases,grouting may also be applied during pile removal.
4.1.7Verticaldeformatiooftheipesoudbestrictlyontrollduringtrenchbackfiling.Forlargerdiameterpipesandteodionf highersoilcoverabove thepipe,temporarysupportsinpipeorpre-deformationmeasuresshouldbeconsidered.Thevertical deformationcausedbyverticalloadcanbecompensatedforbytheverticalreversedeformationthatoccursduringbackfilingand compactionof thepipe haunchingareas;however,itmustbekept within thedesignlimits forverticaldeformation.

4.2Backfill Materialsand Requirements

4.2.1ThetrenchbackfilmaterialsandcompactionrequirementsfromthebedingofthepipebottomuptoO.5metersabovethepipetop should conform to the provisions outlined in the diagram below.
4.2.2The bedding of the pipebotommustbe laidonasoilfoundation thatmeets the bearingcapacity requirements.
4.2.3 The haunches under pipe bottom within the arc shaped soil bedding’s central angle 2α plus 3 0 ^ { \circ } should be filled with medium or coarse sand,andalsoompactedfimlytoensuretigtontactwiththepipewallSoilortherfinerainedmaterialssouldotbeused for filling.
4.2.4Thetrenchsouldackiledmmerialyinersitchlyeompacted.bacfllhtofchlyeshoudteed 0.2 meters.Mechanicalcompactionshouldnotbeusedwhencompacting occurs intherangeof0.5metersabovethepipetop.
4.2.5Thecompactiondegreeof thebackfllsoilshouldmeetthedesignrequirements.Whentherearenodesignrequirements,the compaction degree should meet the specifications shown in the diagram and the table below.

Ground Layered backfill, and Undisturbed soil compaction degree backfill based on ground or road requirements Mandiumusaed, soarese 90% 85% Layerticnmsmof sand-gravel mixture with （204号 { < } 4 0 \mathsf {mm } orsuthgi 95% D E comp1009 aftercompaction Medium sand,and 2α+30° Arc shaped soil bedding central angle 95% (2α plus 30°) at the haunches of the coarse sand pipebottom Mediumand coarse sand shall General layer thickness be used in compliance with ≥100mm,and soft soil Section2.3.1of thismanual for 85%-90% foundation ≥200mm soft foundation. (bedding of the pipe bottom) 一 一 Undisturbed soil of the 二 trench bottom orcompacted Illustration of Trench Backfill Soil soil layer after processing

5.Pipe Tightness Test

5.1After successful completionof pipe laying and inspection,a tightness test of the pipe shallbe conducted.
5.2ThetightnesstestcaneconductedunderthetrenchbackfillcondionsspeciedinSection4.1.nsuringthatthejintreas remain exposed for observation.
5.3Thetightnesstestshouldbeconductedinsectionsbasedonmanholespacing,witheachtestsectionnotexceeding1kminlength and the test should be performed with the manhole in place.
5.4Thetightnesstestmaybeperformedusingthewater-tigtnesstestmethod.Theproceduresmaybecariedoutinaccordance with the provisions of Appendix D of these specifications.
5.5Duringthtightnsstest,vsualinspectionshaleperformed,andtheresouldbnolakage.Thepipeeakagerateould meetthefollowingrequirement:

Where： Q _ { s } ——Water leakage per 1km of pipe over 24 hours ( \mathsf { m } ^ { 3 } ) d _ { j } -Inside diameter of the pipe (mm).

LESSO

6.Transportation and Storage of Pipes

6.1Pipesandfitingsshouldbehandledgentlyduring loading,unloading,transportation,andstacking.Behaviorslikethrowing, dragging,rolling,and impact between items are strictly prohibited.
6.2Whentransportingpipesinbatces,thesocketsandspigotsshouldbearrngedinstaggeredlayers,boundtogetherwithropes, and securely fastened.Soft materials should be used to protect the rope fastening points and pipe ends.
6.3Ifpipesandfitingsneedtobestoredforalongperiod,theyshouldbekeptinawarehouse.Ifstoredoutdoors,theymustbe covered to protect them from sunlight.Thestorage location mustbefarfrom heatsourcesand equipped with waterproof and fireproof measures.
6.4Pipes and fitings should notbe stored for more than 18 months from the date of production.
6.5Pipes and fittings should be kept clean during transportation and storage.
6.6Thestoragegroundforpipesshouldbeflatandthestackingshouldbeorganized.Woodenwedgesandplanksshouldbeplaced on both sidesofthe stacking pipes to preventsliding,andthetype,specification,andquantityshouldbeclearlymarked.
6.7Pipesshouldnotbestackedtoo high.Stackinglayersshouldcomplywiththepipemanufacturer'sstandards fordiferent pipe diameters.
6.8PipesofdiferentdiametersandwallticknessesshouldbestoredseparatelyRubbergasketssupliedwiththeppessouldnot be stored separately.

Repair of Damaged HDPE Double-wall Corrugated Pipe

WhentheouterwallftheHDPEdouble-wallcorugatedpipehaslocalizedcracksorminorperforations,thegoodweldabilityof HDPEpipescanbeusedforrepair.ThedamagedareashouldbecleanedandapliedwithcyclohexanonewithinaO.05-meter range.Then,amatchingsimilar-sizedplate,cutfromanunusedpipe,shouldbeweldedontotheouterwaloftheHDPEdoublewallcorugatedpipeusingaplastichot-airweldinggun.If thepipe’souterwallhasribs,theribswithinO.O5metersof the damagedareashouldberemoved,and leveltheribtracessmoothlybeforeperforming therepairasdescribedabove.

Comparison of HDPE Double-wall Corrugated Pipe and Concrete Pipe

1.HDPE double-wall corrugated pipe isa flexible pipe,while concrete pipe is rigid.Their mechanisms for bearing external loads are different under buried conditions.Flexible pipes permit deformation to a certain extent without damage,while concrete pipes occur cracks with minimal deformation.

2.The roughness coefficient of HDPE double-wall corrugated pipes is 0.010,while that of concrete pipes is O.014.Therefore,under the same operating conditions,the flow capacity of the double-wall corrugated pipe can be improved byabout 40 % .The double-wall corrugated pipe,which achieve equivalent design flow rate,can be designed witha lowerslope orasmallerdiameter.

3.HDPE double-wall corrugated pipesare much lighter inweightand easierto install thanconcrete pipes.Theweight comparison between HDPE double-wall corrugated pipes and concrete pipes is shown in theadjacenttable:

4.The performance comparison between HDPE double-wall corrugated pipes and concrete pipes is shown below:

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5.Comparison of Construction Procedures Between HDPE Double-wall Corrugated Pipes and Concrete Pipes:
a) Construction procedures for HDPE double-wall corrugated pipes: Trenching $$ Pipe placement $$ Connection Manhole backfilling
b) Construction procedures for concrete pipes:Trenching $$ Set continuous bedding formwork $$ Place concrete bedding $$ Curing $$ Pipeplacement $$ Pipealignmentand stabilization $$ Set slanted wall formwork $$ Pourconcrete for slanted wall $$ Joint sealing $$ Curing $$ Construct manhole $$ Conduct water-tightness test $$ Backfilling
c) Based on the comparison above,the construction process of HDPE double-wall corrugated pipe is significantly simpler, which could effectively reduce construction costs and enhance construction efficiency.

In conclusion, HDPE double-wall corrugated pipes offer superior cost-effectiveness compared toconcrete pipes,making theman ideal replacement for traditional concrete pipe systems.

LESSO

LESSO GROUP

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