Installation Manual for
Contents
1. Although asphalt coated corrugated pipe is laid and jointed in the same man ner as galvanized pipe special attention should be given to attaching the con necting bands Contacting surfaces of the bands and pipe may need to be lubricated This allows the band to easily slip around the pipe so it can be drawn more firmly into place Lubrication is especially needed when sur faces are cold In addition tapping the bands with a mallet during tightening will help to assure proper joints Paved Invert Pipe Pipe with an invert pavement must be stored and installed with the smooth thick pavement in the bottom Otherwise installation of paved invert pipe is the same as for galvanized corrugated steel pipe If damage to the coating exposes the galvanizing such areas must be patched with asphalt or bitumen before the structure is backfilled Hoist Pavement Figure 5 Handling a section of large diameter pipe with sling 18 National Corrugated Steel Pipe Association Full Lined Pipe 100 paved pipe is basically an extension of the paving in paved invert pipe to include the entire periphery Since the paving covers all interior corruga tions the pipe should not be subjected to rough handling Smooth steel lined pipe is fabricated with smooth steel liner suitably coated When installations are to be made in hot weather pipe lengths can be ordered with an additional white coating on the pipe exterior to reduce the tempera tu2. the use of a slope reinforcing pavement See Figure 9 The maximum angle permissible for unreinforced skew cut ends is depend ent on the pipe s span or for multiple runs their combined span as well as the fill slope Greater spans or steeper fill slopes limit the degree of skew that can be used without reinforcement When the permissible skew angle is exceeded the cut ends must be reinforced with masonry concrete headwalls or ring beams CSP Installation Manual 23 Figure 9 Embankment erosion protection using bags filled with sand cement mixture For larger span structures or multiple runs this limit needs to be viewed in regard to maintaining a reasonable balance of soil pressures from side to side perpendicular to the structure s centerline For single or multiple structures the design engineer must provide the proper reinforcement and end protec tion in the plans and specifications Long bevels for slopes greater than 2 1 with or without skews should be avoided The long cut ends require extra care in design erection and backfill It is preferable to use a steep bevel without a skew and then warp the fill slope to fit the structure Cut ends of corrugated steel structures where the bevel exceeds 2 1 and or the skew is greater than 15 degrees should have the ends reinforced with masonry or concrete headwalls and anchored in accor dance with specifications More in depth information on design limits is pro vided in the
3. to the side of a trench or to the natural ground line One problem in backfilling is the frequent inclination of installing crews to have the backfill material dumped in piles around the pipe Such piles of material are seldom spread so that there is a maximum depth of a 6 to 8 inch es 15 to 20 meters of compacted layer If the filling crew works too fast the compaction crew never has a chance to adequately compact the first material before more is placed in the trench If backfill material is properly selected well placed and then adequately compacted there is little danger of anything going wrong with the installation See Figure 11 Backfill must be placed and fully compacted to the minimum cover level over the structure before the pipe is subjected to highway or light construc tion loads When construction equipment that exceeds legal highway loads will cross the pipe an extra thickness of compacted fill beyond that required for minimum or planned cover is required See Construction Loads page 37 CSP Installation Manual 27 Trench Pipe as required on the Existing Diameter plan sheets Side Fill see Note c Bedding Blanket see Note b Existing Ground F see Note a KREE d Rough Excavation J i for Bedding Blanket NEGATIVE POSITIVE PROJECTION PROJECTION CONDITION i CONDITION A Pipe Installation and Bedding NOTES a For structural plate pipe the length of bedding ar
4. AISI Handbook of Steel Drainage and Highway Construction Products Cut off Walls Cut off walls protect the structure from hydraulic uplift pressures below its invert and from dynamic flow forces While cut off walls are often unneces sary in small diameter applications equalizer pipes etc larger structures 24 National Corrugated Steel Pipe Association pipes with a large bottom radius such as pipe arches or other pipes in appli cations where currents are swift or water levels rise or fall quickly are more susceptible to hydraulic damage These latter conditions should be investi gated by the design engineer End Sections End Sections provide a practical and economical method of finishing cul verts Sections are attached to the pipe or pipe arch ends by simple connec tors similar to coupling bands used in joining pipe sections and can be completely salvaged if lengthening or relocating the culvert is necessary Other End Finishes While corrugated steel structures do not usually require headwalls practical ly any type can be used Where embankments must be confined full or half high steel sheeting headwalls are both efficient and economical If required for appearance concrete or masonry headwalls or half headwalls can also be used on all types of corrugated steel drainage structures However as is the case with rigid pipe the headwalls must be supported by an adequate foun dation Stream Diversion If the str
5. Additionally during the various phases of assembly backfill and construc tion the structure typically is more vulnerable to loadings and hydraulic forces because its backfill end treatment etc are not complete The corru gated steel structure must be properly protected CSP Installation Manual 37 Construction Loads Frequently it is necessary for heavy construction equipment to travel over installed corrugated steel structures during completion of grading paving or other site work Heavy construction equipment can impose concentrated loads far in excess of those the structure is designed to carry Adequate protection of the corrugated steel structure may require more than finished design fill The amount of additional fill needed depends on the equipment axle loads as well as the frequency of use Figures 17 and 18 provide the minimum cover for typical structure sizes axle loads and construction use While providing extra cover is a simple way to protect the structure it must be maintained so that rutting surface grading etc does not reduce its effect A minimum crossing width of 24 feet 7 3 meters is recommended for typical equipment Minimum Cover ft for Indicated Axle Loads thousands of pounds Pipe Span ne 18 50 50 75 75 110 110 150 12 42 48 72 78 120 126 144 2 0 3 0 3 0 3 5 2 5 3 0 3 5 4 0 3 0 3 5 4 0 4 5 3 0 4 0 4 0 4 5 Minimum cover may vary depend
6. L3 65 4 1 46 66 86 ft 20 3m use 68 ft 20 5m L2 Figure 26 Computation of culvert length skewed to the roadway embankment CSP Installation Manual 47 Skew Number In order to obtain the correct skew cut on a pipe use Figure 27 to determine the proper skew number to give the manufacturer Figure 27 48 National Corrugated Steel Pipe Association NOTES NATIONAL CORRUGATED STEEL PIPE ASSOCIATION 1255 Twenty Third Street NW Suite 200 Washington DC 20037 1174 Phone 202 452 1700 Fax 202 833 3636 E mail csp ncspa org e Web www ncspa org
7. SEGE ERGE ES GR EE EER 21 End Treatment sis esse cits os se ee sie Des ee EG veka hee vee Ee 21 Ut BI EER ERG AE EA 22 National Corrugated Steel Pipe Association 2 ASSEMBLY continued Cut Off LERE EE EE ER ENE 23 End Sections i is Ese ee See EE EA 24 Other End mees 24 Str aim DIivers1Of iris eed ee ed sess eh Mest eg dE ee ee 24 OM doe BIER EE N OOR 25 Backfill ESE EE EE OE EE NE 25 Placinsth Back iese en ee EE GE EE ER ee 25 Pipe Arches RES eet e Ae Bee DE EG EE GE gee 30 PATCHES RA KEER EE 30 Large Diameter Structures 20 000 sesse see se ee ee ee Se ee ee ee ee ee 32 Proper Material Placement 32 Even Placement of Backfill eee se ee ee ee Ge ee ee ee 33 Shape Control es ek RE Ee Eg oes de Ge Rg ee ESE ce Dee eg 33 Multiple Installations eee se se Se Se ee Ge ee ee ee ee ee 34 Long Span Structuttes ees ER EE N GE GR ee ies 35 Final Backfilling i nenn nre see ee se ea GR Ge ee Ge ee ee ee ee ee 35 COMPACTION FOUIDMENT esse sesse sees esse see eke ee esse ee Gee se eek 35 H nd deed dele OR EN 35 Mechanical Compactors iese sees ses se se ee ee Se ee Se ee ee ee ee ee 36 Roller Compactors morenie nen See Eg eee cane ted 36 Vibrating COMPpactoLs 0 cee se se Ge Ge ee Ge ee Ge ee ee ee ee ee 36 Hydraulic Compaction iese see sees se se se ee Se ee Ge ee ee ee ee ee 36 Structure Protection 0 see see see se ee ee se ee ee ee ee ee Ge Ge 36 Construction Loads anenee ER RE N GE ea eo Ee 37 Hydraulic Protec
8. be fol lowed as the fill covers the pipe For the initial layers over the pipe light hand or walk behind compaction equipment is necessary After backfilling 2 ft 6 m over the top or to a depth of 1 8th the span whichever is greater and the soil steel structure is locked into place then further filling to grade may continue using procedures applicable to embank ment construction For construction loads see page 36 The bedding and backfill operation should be entirely conducted in the dry if at all possible but with enough moisture to meet compaction standards There are cases where large CSP are preassembled and rolled or lifted into the stream bed in and wet where is it not possible to build a cofferdam and divert the stream Such conditions make it very difficult to ensure good base preparation and proper backfill Strength consideration must be made by the designer in these cases and expert advice obtained on backfill procedures Shape Control Shape control refers to controlling the symmetry of the structure during backfill by control of the backfill technique Two movements may occur dur ing backfilling peaking caused by the pressure of the compaction of the sidefill and sidewall distortion caused by generating compaction forces on one side of the structure relative to the other Shape changes are limited by using proper backfill compaction procedures and equipment as well as backfill material quality gr
9. bolting together fabricated corrugated steel plates at the installation site Trucks usually deliver the stacks of curved plates to the site and equipment is required to lift such stacks intact Individual plates may be removed and positioned with light equipment CSP Installation Manual 19 Preparation of the base and backfilling are the same as those described for corrugated steel pipe Tools Required Proper tools will speed the erection of structural plate They include struc tural and socket wrenches lining bars drift pins and handling hooks If power wrenches are used check bolt tightness very carefully as it is easy for these wrenches to get out of adjustment The proper use of a long handled structural socket wrench or torque wrench will insure that bolts are properly tightened Erection Every structural plate structure is shipped complete with all necessary plates bolts and nuts for erection Inside one of the containers of bolts clearly marked are detailed erection instructions showing the position of each plate and order of assembly Longitudinal Circumferential Loose Bolts Assemble and connect each plate to adjacent plates with loose bolts near centers of plates in longitudinal and circumferential seams After assembly of all plates insert bolts working toward corners of plates Keep bolts loose Insert corner bolts after all other bolts are in and tightened Figure 6 Method of placing structura
10. or bevels on the pipe end in many cases When desired for hydraulic considerations flared end sections can be furnished for shop fabricated pipe Such end sections can be bolted directly to the pipe When specified ends of corrugated steel structures can be cut beveled or skewed to match the embankment slope However cutting the ends destroys the ability of the end portion of the structure to resist ring compression and uplift forces Thus ends with severe cuts must be reinforced particularly on larger structures For complete details see the AISI Handbook of Steel Drainage amp Highway Construction Products 22 National Corrugated Steel Pipe Association Figure 8 End Treatment End treatment must be constructed as shown in the plans and specifications End treatment should be completed as guickly as possible to avoid problems and structure damage if a storm or other circumstance should arise Cut Ends By cutting the ends of corrugated steel structures the need for additional end finish can often be eliminated The cut ends supplied to specified embank ment slopes are furnished by the fabricator Corrugated steel structures can be supplied with a step bevel bevel or a combination of skew and bevel It is recommended the embankment slope around the bevel or skew cut ends of a structure be protected against erosion and piping by riprapping around the structure end with stone bags filled with dry sand cement mixture or by
11. should be positioned at the lower quarter points as shown in Figure 21 Placing holes in this position lowers the water table efficiently while reducing the tendency of filter material or silt to flow into the pipe Connecting bands for helically corrugated perforated pipe usually supplied 42 National Corrugated Steel Pipe Association ZA IRR N X y SS b gt N Locate perforations at lower quarter points VV WA VA SA oy Figure 21 Correct placement of perforated steel underdrains for small diameter drains may be in two pieces with matching corrugations to fit this helically corrugated steel pipe or sleeve bands Proper Placement of Underdrain Subdrain material must permit ready flow of water while acting as a filter to keep fine soil from entering and clogging the subdrain system Proper grad ing will help prevent backfill from being carried into the pipe Many bank run sands and concrete sand will make a satisfactory backfill for perforated steel underdrains Also material having not more than 10 of its weight in particles larger than 3 8 inch 9 5 millimeter will also make a sat isfactory backfill This backfill material should be placed for a width of at least 6 inches 150 millimeters on each side of the pipe and for the depth over the pipe neces sary to intercept all possible water bearing strata Above this area the trench could be capped with other normal types of backfill material To contr
12. the heavier backfill placed beside it 10 National Corrugated Steel Pipe Association Swampy Foundations Corrugated steel pipe must not be placed in direct contact with pipe bents or concrete cradles that are installed to help provide a foundation Such sup ports if used should be built with a flat top and covered with an earth cush ion In this way the flexible structure can develop side support without con centrating the load at any point Improved Foundations soft uneven unstable or swampy Whenever a foundation is stabilized by using a coarse granular material con sideration of the bedding and backfill material becomes even more impor tant Fine materials can migrate into coarser materials and geotextile separa tors are often required to prevent this migration Settlement Under High Fill Loads camber for embankment installations Cambering the center part of the foundation will compensate for unequal set tlement under the weight of heavy embankments This assures proper grade after settlement and prevents the structure from sagging in the middle as the foundation consolidates Generally sufficient camber can be obtained by installing the upstream half of the pipe on a flat grade and the downstream half on steeper than normal grade as shown in Figure 3 If camber is consid ered necessary based on foundation soil conditions the amount of camber Cambered Pipe Camber Final grade after settlement Figure 3
13. Correct method of cambering pipe to compensate for unequal settle ment under high fills Should be in accordance with procedure given in the AISI Handbook of Steel Drainage and Highway Construction Products CSP Installation Manual 11 must be determined by a gualified soils engineer If the pipe is setting on cushioned rock or other adequate strength foundation no camber is neces sary as settlement will be minor Be careful not to raise the center of the pipe above the inlet as this will pock et water in the pipe Rock Foundations Rock encountered in the foundation must be removed to provide more than the minimum bedding thickness underneath the bottom of the structure Excavate wide enough to avoid any possibility of the pipe resting on rock and provide access to adequately haunch the pipe as shown in Figure 4 The exca vated area is then backfilled with compacted granular soil to cushion the pipe Loose Sand or Lightly Compacted Soil Figure 4 Method of handling rock foundations t 1 2 inch 13 millimeters per foot 30 meter of fill over pipe with 24 inches 60 meter the maximum Arch Foundations Arches differ from other structural plate structures in that they are generally erected on concrete foundations The key way or unbalanced channel in which the arch rests must be accurately built to the proper line grade and spacing for easy assembly of the plates The unbalanced channels must be carefully located t
14. E LU EE SE Installation Manual for Corrugated Steel Pipe Pipe Arches Structural Plate NATIONAL CORRUGATED STEEL PIPE ASSOCIATION 08 InstallMan00 INSTALLATION MANUAL NCSPA The NCSPA Installation Manual is not a copyrighted publication If excerpted or copied credit to the source would be appreciated The information contained in this Installation Manual is the product of industry experience and practice The methods used to install corrugated steel pipe can affect both its effectiveness and useful life The situations described in this publication and the suggested technigues for installation are general sugges tions and guidelines intended to alert installers to the need for careful review of on site conditions Each installation will reguire its own individual evaluation The statements or descriptions provided herein are for general information only The National Corrugated Steel Pipe Association assumes no responsibility for their use EN SS NATIONAL CORRUGATED STEEL PIPE ASSOCIATION 1255 Twenty Third Street NW Suite 200 Washington DC 20037 1174 Phone 202 452 1700 Fax 202 833 3636 E mail csp ncspa org e Web www ncspa org 08 InstallMan00 CSP Installation Manual 1 TABLE OF CONTENTS FOREWORD Eie be Gee EE EEN 3 BASIC PRINCIPLES FOR PROPER CONSTRUCTION AND INSTALLATION AAA 4 LOCATION Seege EE 5 EXCAVATION 5554 heii DE EE ge ee EE 5 Embankment Condton sesse ese ese ee ee e
15. adation and moisture content Special attention should be paid to maintaining the structure s rise dimensions concentricity and smooth uniform curvature The plumb bob method of deflection control is most convenient and effec tive for large structures Suspend plumb bobs from the shoulder 2 and 10 o clock positions so that the points are a specific vertical distance from a marked point on the invert at start of backfill 34 National Corrugated Steel Pipe Association Peaking or deflection action can be detected when the points of the bobs move vertically Corrective action is usually to keep heavy equipment further away from the structure Placing and compacting backfill in thinner lifts and or bringing the backfill to the proper moisture content will reduce the necessary compactive effort and help to control peaking Rolling action can be detected when the plumb bobs move laterally It is cor rected by filling or compacting on the side towards which the plumb bob has moved For example a roll to the right will be corrected by higher fill on the right Careful observance of the deflection control plumb bobs and prompt reme dial steps prevents peaking or rolling action from distorting the structure Multiple Structure Installations Backfill must be balanced across all the structures at all times Placement may require a hoe stonebucket conveyor or other device to assure that even pressure is felt on both sides of all the st
16. and Backfill Details continued CSP Installation Manual 29 Compacted structure backfill see Note c Loose granular fill roughly shaped to fit bottom of pipe and then compacted at haunches and sides of pipe Densely compacted granular fill under haunches a EET CR Existing see Note d soft ground D Foundation Stabilization for Large Diameter Structures Figure 11 Bedding and Backfill Details continued Maintain equal elevation both sides of pipe arches Na A See N bh We MAY KKK Stable but relatively yielding Compacted to maximum density under haunches Figure 12 Recommended backfilling practice for larger pipe arch using a vee shaped bed 30 National Corrugated Steel Pipe Association Pipe Arches Special attention must be given to compaction of the backfill under the haunches of the pipe arch A softer or yielding foundation under the bottom as compared to the corners is essential See Figure 12 A vee shaped bed for larger pipe arches is recommended Arches Care must be taken in backfilling arches especially half circle arches because they have a tendency to shift sideways or to peak under backfilling loads The ideal way is to cover an arch in layers each layer conforming to the shape of the arch If one side is backfilled more than the other the arch will move away from the larger load If both sides are backfilled equally and tamped thoroughly the top of the arch may
17. c need not exceed width of bottom plate b Bedding blanket of loose granular fill roughly shaped to fit bottom of pipe Minimum thickness before placing pipe shall be as fol lows 1 inch 25mm for 1 2 inch 13mm deep corrugation 2 inches 50mm for 1 inch 25mm deep corrugation 3 inches 75mm for 2 inches 560mm deep corrugation c Side fill to be compacted in 6 to 8 inches 15 to 20 meters of compacted layers to density specified for adjacent embankment but not less than 90 Standard Proctor Density AASHTO T99 d Bedding width may be 1 diameter except for pipe arches where it is limited to a maximum of 2 3 the span Figure 11 Bedding and Backfill Details 28 National Corrugated Steel Pipe Association Side Fill see Note c Loose granular fill roughly shaped to fit bottom of pipe and then compacted at haunches and sides of pipe o KE O Zz o 03 wn B Pipe Installed Over Rock Loose granular fill Thickness to be 1 2 per ft 13 mm per 3 m of fill over pipe with a 12 min and 24 max 30 mm min and 60 mm max To be lightly and uniformly com pacted Side Fill see Note c Loose granular fill roughly shaped to fit bottom of pipe and then compacted at haunches and sides of pipe see Note a og Compacted granu ER EE EERS dd TERDEE Compressible soil or as planned C Foundation Stabilization for Small Diameter Structures Figure 11 Bedding
18. e Re ee ee Re 5 Trench Conditions se EE EE Es Kea foc deed Sunda Ed ees EE ee 5 Trench Width and Shape eee see se ee SR GR Se Re Ge Ge ee ee ee 6 PREPARING FOUNDATIONS AAA H Handling Poor Foundations esse sesse esse ee es se ee ee Re ee ee RA ee 7 Uneven Foundations ees ses se ee ee Re ee Ge Re ee AR ee A 8 Soft Fondations es EERS Ee dree cee Bee GE ee Be Re Es 9 Pockets of Unstable Sol 9 Swampy Foundations 2 0 0 0 eee se ee se se ee ee ee ee ee Ge Ge 10 Improved Foundations 0 0 0 0 se se se se ee Se ee Ge ee Ge ee ee ee 10 Settlement Under High Fill Loads wo esse ese esse see se se ee 10 Rock Foundations EES GENEES SR ee dee ai EE DEER 11 Arch Foundations Ese tisk es key Ee Ke dE ER ske eb Ee ese N seges Eed 11 ASSEMBLY SMEER EE HE EEN 12 Unloading and Handi 12 Connecting Bands ek se Bees eg Ee e EENS SeSe 12 Installing Connecting Bands AA 12 Typical Connecting Bands AA 14 Lake AE ER EE EE EE Ee 16 ER EO OE OE deed 17 Asphalt Coated Pipes issie gie Ee ser tir LESER KORES ED SR GR eke ee Gee Ke ge ee 17 Paved Invert di OE EE EE EE EE dee 17 Full Lined Pipe siterer Kees REEN ED ese Ee eg Ge ER VR NEE ee WEE SEE GEED 18 Polymer Coated Dpe A 18 Pipe GE EO ER EE EE 18 Field Coated Structural Plate Structures 18 Structural Plate Structures 18 Tools Required ARE EE EEN 19 Erection ene RE OR OE EN 19 Long Span Structures iese see se se ienris Se ee Ge ee Ge ee ee ee ee ee 21 LiftingAssIstanGe ii ESE ENEE eseu ER GE
19. eam is temporarily diverted during construction the diversion ditch or temporary drainage pipe must be adequate to carry the storm flow Short construction times of course are helpful in limiting this exposure The pipe installation must be protected from storm flows by a temporary dike coffer dam etc If the structure must carry the flow during the construction stage the upstream end must be protected with the proper end treatment etc to ensure that the flow is not diverted around or beside the pipe thereby scouring out backfill as it is placed or floating the pipe In phased construction it is desir able to construct and backfill the upstream end first See Hydraulic Protection page 38 CSP Installation Manual 25 BACKFILLING The load carrying capacity of any type of pipe is largely dependent upon proper backfilling Corrugated steel pipes build up side support as they deflect under load Therefore to obtain maximum strength and prevent washing out and settle ment it is necessary that the backfill be made of good material properly placed carefully compacted and protected SOIL LOAD is SIDE SUPPORT gt Figure 10 Pipe side support is developed by slight pipe deflection under load Backfill Material Selected drainable materials achieve the best results However many local fill materials may do the job if carefully placed and compacted Consult the design engineer or a soils engineer for
20. f corrugat ed steel pipe pipe arch and structural plate Too much emphasis cannot be placed on the necessity of adequate compaction of backfill Faulty compaction has led to more trouble with pipe installations flexible and rigid than all other factors combined OSHA safety regulations and guidelines must be observed during all phases of construction including foundation preparation excavation pipe handling assembly and backfilling Additional information is available in the AISI Handbook of Steel Drainage and Highway Construction Products and ASTM Specifications A 798 and A 807 This manual uses dual units of measure with Imperial units shown first fol lowed by metric units in parentheses Complex drawings or tables may be duplicated in metric 4 National Corrugated Steel Pipe Association BASIC PRINCIPLES FOR PROPER CONSTRUCTION amp INSTALLATION Project plans and specifications provide the basic reguirements for construc tion and installation However site conditions often vary from those antici pated during design The contractor and construction engineer must recog nize these variations Often alternate or additional construction considera tions are necessary The following guidelines provide specific considerations and details for various conditions in a step by step construction sequence The following summary will appear again near the end of the manual However review it now as a basic outline of the steps requ
21. g should be scheduled in close sequence with each other An open trench is dangerous and vulnera ble to accidents An open excavation can result in damage to the project under construction The two main hazards that must always be considered in trenching work are Stability of trench walls and gt Water that may accumulate in the trench resulting from seepage and surface runoff National Corrugated Steel Pipe Association To minimize accidents and losses resulting from trenching operations the fol lowing procedures should be followed gt gt gt gt Begin excavation only when installation of pipe can immediately follow Protect trench walls to insure their stability throughout the con struction period Follow procedures that will keep the trench free of seepage and sur face waters Excavate the trench at the same rate as pipe installation with a min imum distance as dictated by safety separating the two operations Backfill the trench as soon as practicable after pipe installation Trench Width and Shape The width and shape of the trench should be as shown on the plans Any change should be approved by the Engineer Generally the trench width will be specified as 12 to 48 inches 300 to 1200 millimeters wider than the pipe However it must be wide enough to allow the critical lower quadrants of the pipe to be properly backfilled haunched Figure 16 provides guidelines about minimum spacin
22. g between multiple structures These same guidelines can be used to provide the necessary width between the pipe and trench wall to adequately place typical backfill Lesser spacing may be used with slurries and other backfill materials that do not require mechanical compaction CSP Installation Manual 7 PREPARING FOUNDATIONS Foundation reguirements should be detailed on the plan sheets However field conditions often vary reguiring special attention and alterations that are discovered only during excavation Any alterations should first be approved by the Engineer Although corrugated steel drainage structures can experience some uneven settlement without disjointing or breaking they should be placed on a firm uniform foundation for best performance and long service life All storm sewers and culverts must be installed with the area under the haunches well compacted and all voids filled For corrugated steel pipe the most popular method of preparing the founda tion is by excavating to a flat surface and then carefully tamping the fill under the haunches of the pipe Proper backfill density can be achieved by com pacting the soil with a wooden pole 2 x 4 or the smaller sizes of pneumatic tampers to eliminate all voids under the structure See Figure 1 for typical methods of bedding corrugated steel structures and the 2 x 4 description This flat foundation technique works well except for larger pipe arches and horizontal e
23. gen eral structural plate assembly requirements apply However because of their size the plates need to be tightly bolted as they are placed Because much of the strength of these structures is derived from their shape the rise and span of the assembled shape must be within 2 percent of the design dimensions prior to backfilling With any long span structure the manufacturer should cover specific requirements in a pre construction conference Lifting Assistance Generally speaking if the diameter or rise of the structural plate structure is beyond the extended arms of the average construction worker he should be provided some type of lifting equipment or scaffolding If powered lifting equipment is not feasible or readily available here are other ways of simpli fying assembly 1 An A frame utilizing man powered block and tackle 2 A lifting hoist built into the bed of a flat bed truck 3 Bed of a flat bed truck if size of structure permits the truck to be driven inside 4 A combination of scaffolding built inside the structure and ladders outside Or a flat bed truck plus scaffolding End Treatment In many cases the ends of corrugated steel pipe that project through the embankment can be simply specified as square ends that is not beveled or skewed The square end is lowest in cost and readily adaptable to road widen ing projects For larger structures the slope can be warped around the ends to avoid severe skews
24. hem togeth er Advantage of these devices is that they permit faster hand tightening of the bolts so that a wrench is needed only for final tightening On large diameter pipe and asphalt coated pipe merely tightening bolts will not assure a tight joint due to the friction between the band and the pipe ends In such installation tap the band with a mallet to take up the slack as the band is tightened The wrench used to tighten coupling bands may be a deep socket or ratchet wrench for greater speed Figure 4A Typical connecting band is wrapped around the joint and drawn together 14 National Corrugated Steel Pipe Association Standard Couplers Unless a dimple fills each corrugation valley a suitable gasket or geotextile wrap is required Universal Gasketed Couplers Sleeve Gasket Mastic or Gasket A Semi Corrugated Hugger Figure 4B Standard and Gasketed couplers for corrugated steel pipe CSP Installation Manual 15 Standard CSP Band Connectors Band Angle Connector Clip or Lug Angle Connector Bar and Strap Connector Figure 4C These typical band connectors are used with CSP coupling systems 16 National Corrugated Steel Pipe Association When reguired connecting bands can be furnished with gaskets or mastic as follows Gaskets Closed cell rubber butyl rubber neoprene or closed cell rubber sponge gas kets are the basic types of materials
25. ing on local conditions The contractor must provide the additional cover required to avoid damage to the pipe Mini mum cover is measured from the top of the pipe to the top of the maintained construction roadway surface In unpaved situation the surface must be maintained Pipe Span mm Figure 17 Minimum Cover Minimum Cover m for Indicated Axle Loads metric tons 8 23 23 34 34 50 50 68 305 1067 1219 1829 1981 3048 3200 3658 6 9 9 1 0 8 9 1 0 1 2 9 1 0 1 2 1 4 D 1 2 1 2 1 4 Minimum cover may vary depending on local conditions The contractor must provide the additional cover required to avoid damage to the pipe Mini mum cover is measured from the top of the pipe to the top of the maintained construction roadway surface In unpaved situation the surface must be maintained Figure 18 Metric equivalent of Figure 18 38 National Corrugated Steel Pipe Association Figure 19 Compacted side fill should be completed on both sides of structure before fill is carried over for construction traffic Temporary dead loads resulting from storage piles crane placements etc must be evaluated as to structure capacity loading balance backfill support adequate foundation strength and other factors that may be applicable to the conditions Hydraulic Protection During installation prior to the completion of backfilling permanent end treatment slope pro
26. ired for a proper installation 1 Check alignment in relation to the plans as well as the actual site conditions 2 Make certain the pipe length s necessary appurtenances etc are correct 3 Excavate to the correct width line and grade 4 Provide a uniform stable foundation correct site condi tions as necessary 5 Unload handle and store the pipe correctly 6 Assemble the pipe properly check alignment follow spe cial procedures for the connecting bands gaskets and other hardware used For structural plate structures achieve properly aligned plate laps bolt torque and assembled dimensions 7 Use a suitable granular backfill material as required in the plans and specifications 8 Maintain proper backfill width 9 Haunch the pipe properly 10 Place and compact the backfill in 6 to 8 inches 150 to 200 millimeters of thickness of compacted lifts 11 Install the necessary end treatment quickly to protect the pipe and your efforts 12 Protect the structure from heavy construction equipment loads other heavy loads and hydraulic forces CSP Installation Manual 5 LOCATION Before installing any drainage structure it is best to first recheck the planned alignment and grade position and percent of slope of the pipe in relation to the topography of the site Even when complete construction plans are sup plied a careful examination of the site should be made EXCAVATION Embankment Cond
27. ition The only excavation typically required for an embankment condition is to remove the topsoil muck and organic matter and prepare a stable foundation at the proper elevation and grade Trench Condition Most storm sewers are installed in trenches Although pipes can be easily installed in a trench there are some general guidelines that should be followed All trench excavation should proceed only after OSHA and other safety requirements are met Trench excavation normally proceeds in the upgrade direction Most trenching equipment is more efficiently operated in this man ner and pipe sections are also more easily joined when progressing in this direction If excavated spoil is to be used as backfill it should be stockpiled at a safe distance from the edge of the trench As a general rule when trench walls are unsupported the distance from the trench edge to the toe of the stockpiled material should not be less than one half the depth of the trench When trench walls are protected by some form of sheeting or shoring a safe minimum distance between the trench edge and stockpiled material must still be maintained but will vary with soil and bracing types Care should always be exercised in the operation of equipment in the vicin ity of an open trench Operated too close to the trench equipment weight and vibration may collapse the trench walls The three phases of construction in a trench excavation pipe installation and backfillin
28. l bands and their method of installation are illustrated in Figures 4A to 4E Specially fabricated bolted welded or riveted connectors can be sup plied for use in jacking and for special or unusual conditions If the pipe ends have been match marked by the fabricator then they must be installed in the proper sequence Installing Connecting Bands During the construction of a corrugated steel pipe system care must be given to the assembly of joints to control both infiltration and exfiltration Both processes will have an effect upon backfill materials since soil particle migration can occur This is particularly true when fine rained soils fine sands and silts are present in the backfill material When necessary a gas ket a geotextile wrap or both can also be used to control infiltration of fines CSP Installation Manual 13 Bands are put into position at the end of one section of pipe with the band open to receive the next section The next section is brought against or to within inch 25 millimeters of the first section After checking to see that connecting parts of both band and pipe sections match that the interior of bands and exterior of pipe are free of dirt stones etc bolts are inserted and tightened To speed the coupling operation especially for large diameter structures a cinching device will help draw the band up tight Special coupling devices can be used to fit over the connecting bands and quickly draw t
29. l plate bolts 20 National Corrugated Steel Pipe Association Structural plate structures should be assembled with as few bolts as possible until all plates are in place Three or four finger tight bolts placed near the center of each plate along the longitudinal and circumferential seams are suf ficient See Figure 6 After several rings a ring is a circumferential series of plates required to make one continuous circle have been assembled the remaining bolts can be installed but not torqued tight always working from the center of a seam toward the corner of the plates Do not insert corner bolts until all others are in place and tightened Aligning bolt holes with a bar is done more easily when the bolts are loose Drifting with a drift pin is best done when the adjacent bolts are tight Tighten nuts progressively and uniformly starting at one end of the structure after all plates have been assembled Then repeat the operation to be sure bolts are tight From 100 to 300 foot pounds 140 to 400 newton meters of torque should be applied Do not over torque A good plate fit is far more important than high bolt torque Some structures require alternate procedures refer to the manufacturer s assembly instructions Figure 7 Modern erection techniques are used in assembling structural plate CSP Installation Manual 21 Long Span Structures Long span structures are large structural plate pipes or arches to which
30. llipses The vee shaped bedding technique for these struc tures is shown in Figure 12 All pipe must be placed on stable earth or fine granular foundation Never install them on sod frozen earth or on a bed that contains large boulders or rock When poor foundations with low bearing strength are encountered investigate the possibility of a change in pipe location Otherwise it may be necessary to stabilize the poor foundation by a method described in the next section Care must be taken to prevent water leaking through the fill or along the pipe When granular materials have been added for bedding the ends of the fill should be sealed against infiltration This can be done by bedding the ends in well compacted clay or by adding some type of end treatment such as an end section or a cut off wall Handling Poor Foundations If poor or non uniform foundations are encountered they must be treated correctly to assure satisfactory results The critical factor is to achieve uni formity along the pipe with a tendency for the foundation to yield under the pipe in relation to alongside the pipe 8 National Corrugated Steel Pipe Association Uneven Foundations When the excavated grade line reveals both soft and hard spots the founda tion must be changed to make it as uniform as possible Sometimes hard spots can be excavated below grade and replaced with softer material Alternatively it may be more economical to excavate the entire founda
31. materials Because of their size the manufacturer will supply a shape control inspector to aid in the critical portion of the backfilling process Specific backfill and placement requirements will be reviewed in the pre construction conference Final Backfilling Once the envelope of backfill material is placed around and over the pipe and properly compacted the remainder of the fill the final backfill should be placed and compacted to prevent settlement at the surface The backfill mate rial and compaction level specified has been selected to prevent surface sub sidence protect the pavement etc When thick sheeting such as wood has been used to support the trench walls be sure to fill and compact the voids left when it is withdrawn or cut it off above the crown of the pipe Final backfill is compacted by conventional methods The use of water flood ing or jetting should be limited to compacting soils which are sufficiently permeable to dispose of the excess water and should not be used with cohe sive soils However final backfill can be compacted with fewer restrictions on materials and layer thickness than the backfill in the envelope around and immediately above the pipe 36 National Corrugated Steel Pipe Association COMPACTION EOUIPMENT Hand Compaction For compacting the small areas under the haunches of a structure a pole or 2 x 4 see note under Figure 1 is generally needed Hand tampers for hori Zontal layers sho
32. most effective drainage However if the strata is too deep to permit draining to a natural outlet the pipe can be placed within the water bearing material if this would permit natural drainage or a sump pump may be used This does not provide complete drainage but will lower the natural water table to a desirable level Outlets should be free and not subject to flooding or restriction by freezing or debris and protected against damage by maintenance equipment Where possible it is desirable to use a 0 2 percent minimum slope for all subdrainage lines Preparing the Foundation Underdrain pipe should be laid on a stable foundation If the bottom of the trench can be set below the water bearing strata and the pipe placed in an impervious layer the foundation will generally be stable But if the pipe must be located in water bearing strata it may be necessary to stabilize the bottom of the trench by placing granular material under the pipe However corru gated steel underdrains will hold alignment on soft foundations much better than rigid or plastic pipes Steel pipe is supplied in much longer lengths and thus diminishes the hazards of disjointing settlement and loss of alignment Assembly of Underdrain Pipe Assembly or installation of a subdrainage system is usually started at the downstream or outlet end to allow ground water to drain out of the trench keeping it reasonably dry during construction If not specified pipe perforations
33. o insure that the holes correctly align with those in the plates to permit bolting They must be properly oriented angled to receive the plate 12 National Corrugated Steel Pipe Association ASSEMBLY Unloading and handling Pipe must never be dumped directly from a truck bed while unloading Although corrugated steel drainage structures withstand normal handling they should be handled with reasonable care Dragging the pipe at any time may damage the coatings Also avoid striking rocks or hard objects when lowering pipe into trenches Since corrugated steel pipes are relatively light weight they can be handled with light equipment Use of slings is recommended to properly handle the pipe Connecting Bands The usual method of joining two or more lengths of pipe or pipe arch is by steel connecting bands The bands engage the ends of each pipe section They are placed to overlap each pipe section equally The corrugations on the band must fit into the corrugations of each pipe Tightening of bolts draws the band tightly around the adjacent ends of pipe lengths providing an integral and continuous structure One piece bands are used for most installations of smaller sizes of pipe Two piece bands are used on larger diameter pipe and when installation conditions are difficult Rods and Lugs are used on levees aerial sewers and similar installations where bands that provide tighter and stronger joints are essential Typica
34. ol settlement subdrain backfill should be placed in layers and well compacted A geotextile may be used to prevent infiltration of fines particu larly at the joint CSP Installation Manual 43 W ny VAAN IMPERVIOUS ORIGINAL E MATERIA N SINS FINAL de V p IMPERVIOUS KE MATERIAL VAN A Only one filter gradation needed Filter material is used to prevent migration of soil particles from trench wall which would cause silting of underdrain and settlement of surface Figure 22 Corrugated steel pipe underdrain 44 National Corrugated Steel Pipe Association APPENDIX Culvert Grades and Outfall Treatment Reduced Waterway Anticipating XI Sedimentation Stream other open spillway mi Drop inlet Cantitever Figure 23 Methods of obtaining correct culvert grade Length of Culverts Length of a culvert depends upon roadway width from shoulder to shoulder height of fill above flow line side slope of the embankment as well as align ment and grade Where culverts are to be installed at right angles to the road their length can be computed by the method presented in Figures 24 and 25 Note that when culverts are on steep grades their centers are offset with respect to roadway centerline In calculating length of skewed culverts those at less than 90 degree angle to roadway centerline length must be increased according to skew angle See page 46 Lengths of corrugated steel pipe and
35. peak unless enough fill has been placed over it to resist the upward thrust These precautions apply also to other corrugated steel structures but to a lesser degree When backfilling arches before headwalls are placed the first material should be placed midway between the ends of the arch forming as narrow a ramp as possible until the top of the arch is reached The ramp should be built evenly from both sides and the backfill material should be thoroughly com pacted as it is placed After the two ramps have been built to the depth spec ified to the top of the arch the remainder of the backfill should be placed and compacted by extending the ramp both ways from the center to the ends and as evenly as practicable on both sides of the arch If the headwalls are built before the arch is backfilled the backfill material should first be placed adjacent to each headwall placing and compacting material uniformly on both sides of the structure until the top of the arch is reached Then backfill should proceed toward the center by extending the ramp with care being taken to place and compact the material evenly on both sides of the arch Top loading will help control peaking CSP Installation Manual 31 SE N Filling on only one side causes arch to shift If fili is not placed on top as backfilling proceeds arch may raise thereby flattening side radius COMMON MISTAKES IN BACKFILLING ARCHES above Place fill on arch by distributing ma
36. proper backfill selection Well graded granular material containing a small amount of silt or clay is ideal because is makes a dense stable fill Fill material must be free from rocks and hard earth clods larger than 3 inches 75 millimeters in size It must not contain any frozen material sod cinders or earth containing organic matter Placing the Backfill Too much emphasis cannot be placed on the necessity of adequate compaction of backfill Faulty compaction has led to more trouble with pipe installations flexible and rigid than all other factors combined 26 National Corrugated Steel Pipe Association For trench installations backfill must follow as closely behind the excavation and assembly stages as possible Embankment installations typically are backfilled after the entire structure or a major portion of it is assembled Unless the embankment and backfill materials are placed simultaneously one must be benched so the other can be compacted against it The backfill should be carefully compacted under the haunches lower part of structure exterior below widest part special care should be taken in doing this for pipe arches Continue placing the backfill egually on both sides of the pipe in 6 to 8 inch es 15 to 20 meters of compacted layers thoroughly compacting each layer to a 90 Standard Proctor density AASHTO T99 Such compacted layers must extend to the limits shown on the plans on each side of the structure or
37. re of the pipe if it is to be exposed to the bright summer sun for long peri ods Prolonged storage of fully lined pipe should be avoided in any season Polymer Coated Pipe Polymer coated pipe shall be installed in the same manner as asphalt coated pipe Lubrication is not required unless gaskets are used Pipe Arch Corrugated steel pipe arch structures are installed in the same manner as round pipe Recommendations regarding placement and connecting of vari ous types of pipe also apply to pipe arch However because of its shape par ticular care should be taken in installing pipe arch structures See page 30 Because of their multiple radius shape pipe arches are not intended for restrictive leakage or high cover applications Field Coated Structural Plate Structures Field coated asphalt mastic coatings shall be applied per the manufacturer s application instructions and material safety data sheet MSDS The coating shall be applied to a clean surface free of dirt oil grease or other foreign matter when the atmospheric temperature is above 40 F 4 C and the humidity is low enough that the surface of the metal can be kept dry Coating may be applied by spray brush or trowel as required by the manu facturer to attain a uniform dry thickness of 0 05 inch 1 3 millimeters Structural Plate Structures The primary difference between structural plate and factory fabricated pipe is that structural plate is assembled by
38. rience The following items should be checked to insure proper installation 1 Check alignment in relation to the plans as well as the actual site conditions 2 Make certain the pipe length s necessary appur tenances etc are correct 3 Excavate to the correct width line and grade 4 Provide a uniform stable foundation correct site conditions as necessary 5 Unload handle and store the pipe correctly 6 Assemble the pipe properly check alignment fol low special procedures for the connecting bands gaskets and other hardware used For structural plate structures achieve properly aligned plate laps bolt torque and assembled dimensions 7 Use a suitable granular backfill material as required in the plans and specifications 8 Maintain proper backfill width 9 Haunch the pipe properly 10 Place and compact the backfill in 6 to 8 inches 150 to 200 millimeters of thickness of compact ed lifts 11 Install the necessary end treatment quickly to protect the pipe and your efforts 12 Protect the structure from heavy construction equipment loads other heavy loads and hydraulic forces CSP Installation Manual 41 SUBDRAINAGE Underdrain Pipe Underdrains to remove ground water must be properly installed to give long satisfactory service With perforated steel underdrain pipe correct installation is fast and easy Flow Line The flow line should be placed below water bearing strata for
39. ructures The design should have provided adequate room between the structures to operate the equipment required for proper compaction of the backfill Flowable fills that require no compaction effort can be used with minimal spacing between the pipes Geng O SPAN SPACE X Y Up to 36 915 mm 36 915 mm to 108 2743 mm 1 3 Arch Span 108 2743 mm to 189 4800 mm 36 800 mm DIAMETER SPACE Y PIPE ARCHES Up to 24 610 mm 12 300 mm EE p 24 610 mm to 72 1830 mm 1 2 Pipe Diameter 72 1830 mm and over 36 915 mm 6 m 24 in ARCHES Figure 16 Minimum Spacing CSP Installation Manual 35 Recommended minimum spacings for pipe pipe arch and arches are shown in Figure 16 The spacings are for the use of all standard backfill materials and allow room for compacting the backfill The minimum spacing shown also provides adequate room between the pipe and the trench wall for adequate material placement and compaction Whether the structure is large or small keep in mind that the requirements of economical equipment should also be considered in determining spacing between the structures For example with structural plate structures it may be desirable to utilize mobile equipment for compaction between the struc tures The space between pipes should allow efficient operation and selection of compaction equipment Long Span Structures Long span structures use only the best non plastic granular
40. structural plate pipe are normally sup plied in even increments of 2 ft 6 meter In order to obtain the correct skew cut on a pipe use Figure 27 to determine the proper skew number to give the manufacturer CSP Installation Manual 45 Length A 2B Example Roadway 24 ft Slope 114 1 Depth of Fill 4Oft Then B Side Slope x C tec and Length 24 3x 10 54 ft Figure 24 Computation of culvert length flow line on flat grade Length A Bi B2 Example Roadway 24 ft Slope 114 1 Depth of Fill Upstream 10ft Downstream 15 ft Then B 11 2 x C and B 11 2 x C and Length 24 112x710 112x 15 61 5 ft Use 62 ft Figure 25 Computation of culvert length flow line on steep grade Note Superior numbers 1 to 6 in figures 24 and 25 are to be ignored in working the examples They are to convert the examples to metric values in meters as follows lis 7 3m 2is3m 3 is 16 3 mm 4 is 4 6m 5 is 18 7 m 6 is 19m 46 National Corrugated Steel Pipe Association ROADWAY 18 7 m From fig 25 PLAN VIEW Use example in Figure 25 but the pipe is skewed 20 to the roadway i e cross 20 off the perpendicular The pipe is 4 ft 1220 mm in dia LI actual culvert length for no skew 61 5 ft 18 7m from Figure 25 L1 61 5 cos skewZ cos 20 69 4 SE L3 pipe span x tan skewZ 4x Tan 20 4 x 0 364 1 46 ft 45m Length L2
41. tection flow controls etc the structure is vulnerable to storm and flow conditions less than the final design levels Hydraulic flow forces on unprotected ends unbalanced backfill loads loss of backfill and support due to erosion and uplift forces are examples of factors to be con sidered While guidance is offered in some of the above sections temporary protection may need to be constructed Hydraulic forces can float in complete structures without protection or buck le inverts large radius inverts are especially vulnerable to buckling if the foundation bedding or backfill becomes saturated Proper channeling of flow through active structures placing end treatment and slope protection as early as possible are advised Protecting cofferdamned structures and trench installations from ponding CSP Installation Manual 39 Construction Eduipment Traffic Construction a Cover Finished Grade Temporary Cover for Construction Loads Figure 20 Minimum cover for construction leads Adequate uniform compaction is the secret to building soil and steel structures 40 National Corrugated Steel Pipe Association SUMMARY Proper installation of any drainage structure will result in longer and more efficient service This installation manual is intended to call attention to both good practice and to warn against possible pitfalls The principles apply to most conditions It is not a specification but an aid to your own expe
42. terial around and over the structure in uniform layers tamping thoroughly SIDE VIEW With Headwalls Figure 13 Recommended backfilling practice for structural plate arches 32 National Corrugated Steel Pipe Association Large Diameter Structures Embankment Installations Large diameter structures are not to be confused with Long Span Structures see page 35 Proper Material Placement The areas immediately next to the pipe must be compacted by hand operat ed methods although heavy compaction equipment may be brought quite close within 2 ft 6 m in most embankment installations Changes in dimension or plumb of the structure warn that heavy machines must work further away Spread backfill material with equipment running parallel to not at right angles to the structure Figure 14 Hand compaction and heavy equipment procedure Figure 15 Proper material placement CSP Installation Manual 33 Even Placement of Backfill Compact the backfill by working parallel to not against the structure Place fill evenly on both sides Peaking or rolling of the structure must be avoided Note discussion of shape control page 33 For multiple installations sufficient space between the pipes must be allowed for compaction equipment to operate properly see Figure 16 When the fill on both sides approaches the crown of the pipe the same tech niques of spreading shallow layers and compacting thoroughly must
43. tion slightly below grade line and replace it with suitable uniform material In any event any abrupt changes from hard to soft foundation must be avoided Shaped Foundation Tamped Fill Figure 1 Methods for attaining proper compaction under haunches of CSP and pipe arch Note When tamping with a 2 x 4 the designation of 2 x 4 will remain in usage as a descriptive expression without conversion to metric It represents an approximate lumber cross section of 40 by 90 millime ters CSP Installation Manual 9 Treatment for Soft Foundations GEOTEXTILE SEPARATOR if required GRANULAR MATERIAL k D Direction of desired relative movement shown by arrows Figure 2 Soft Foundations When soft unstable material is encountered at the foundation level it must be excavated below the flow line grade and backfilled to grade with sand gravel crushed stone or other suitable material The zone of select material must be adequate to support the pipe and backfill When unexpected materi als are encountered consult the Engineer Pockets of Unstable Soil If unstable foundation material is in small pockets it is best to excavate all of the poor foundation and replace it with suitable backfill material Frequently a relatively thin mat of granular material will provide satisfacto ry support but it may be necessary to replace very soft foundations to a depth great enough to support not only the pipe but also
44. tion 0 0 tees se se se ee ee Se ee Ge ee ee ee ee ee 38 SUMMARY ena Ge SE EE se Ee ED Ge Ee Ge ge e E ee ese tian 40 SUBDRAINAGE EE OE OE OE OE N 41 Underdrain Pipe e eese peee resepe eege enen N o TEP gah Ee oE Se SR se 41 die Ab ER a EE alana 41 Preparing the Foundation esse sesse es se ee ee ee ee Re ee ee ee 41 Assembly of Underdrain De 41 Proper Placement of Underdrain Drpe cece see se ee ee ee 42 APPENDIX wih pe hatte ae Aland Meh ott bed or eee 44 Culvert Grades and Outfall Treatment sesse se ee se ee se tees 44 Lensth of Culverts ss Es es ee ed 44 Skew Number EE RE EE Roch cedes EE EG Ee aves ee ee ee Ee 47 CSP Installation Manual 3 FOREWORD This manual is intended for both the contractor and the engineer It provides practical information for the installation of corrugated steel pipe as storm sewers or culverts It also provides the necessary considerations for proper design to achieve long term performance of the culvert or storm sewer Corrugated steel pipe with its high load carrying capacity strong joints and exceptional beam strength is installed more easily than other types of con duit However the correct installation procedures must be followed to insure full investment value in the structure It is the intent of this manual to suggest ways and means of improving installation practices It is not intended to be used as a direct specifica tion but rather as a practical field guide for the installation o
45. to provide 1 O ring gaskets which are recessed in a corrugation and then con fined by the band after the joint is completed 2 flat gaskets placed on each end of the pipe forming a joint and con fined by the connecting band 3 a flat sheet gasket placed over the ends of both pipes 4 a gasket that is normally placed in the channel of the flanged band connector For all field installed gaskets a smooth round rod should be inserted under the gasket and run around the circumference two or three times to equalize the stretch in the gasket On asphalt coated pipe it may be necessary to clean the gasket groove to properly seat the gasket The alignment and assembly of the pipe sections is extremely important when gaskets are used A lubricant must be applied to the gasket for proper installation as recommended by the manufacturer When a tightness test is required for final acceptance the con tractor should conduct his own test after a few joints are assembled as a check of his assembly methods O Ring Gasket Sleeve Gasket Strip Gasket or Geotextile Wrap Figure 4D Typical gaskets for use with connecting bands where required CSP Installation Manual 17 Mastic Mastic may be applied to the connecting band or pipe prior to placing and ten sioning the connecting band A sufficient amount of mastic should be used to fill the joint space between the corrugation and band with some squeeze out Asphalt Coated Pipe
46. uld weigh not less than 20 pounds 9 kilograms and have a tamping face not larger than 6 by 6 inches 150 x 150 millimeters Mechanical Compactors Most types of power tampers are satisfactory in all except the most confined areas However they must be used carefully and completely over the entire area of each layer to obtain the desired compaction Avoid striking the struc ture with power tamping tools Roller Compactors Where space permits sheepsfoot recommended for clays and silts only rubber tired and other types of rollers with the exception of smooth rollers can be used to compact backfill But the fill adjacent to the structure should be tamped with hand or hand held power equipment Vibrating Compactors Vibrating compactors can be used effectively on all types of backfill except heavy clays or other plastic soils Small walk behind equipment is especial ly suited to trench installations Hydraulic Compaction The use of water flooding and or jetting for compacting backfill around the pipe is limited to compacting clean granular soils To be effective the foun dation below the pipe must be sufficiently permeable to carry the water down and away quickly Backfill around and immediately above the pipe must be placed and compacted in individual lifts of 6 to 8 inches 150 to 200 mil limeters of compacted thickness Structure Protection Often construction loads exceed the finished design loads for the structure
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