Mini-span Bridges / technical guide - Armtec

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mini-span bridges_NOTE• Obtaining permits for diversionwork(s) and installation of themini-span are the responsibilityof the owner• For design of foundation/footing callArmtec for un-factored footing loads• Foundation should be investigated byqualified local geotechnical engineerINSTALLATION OF mini-span bridgeINSTALLATION1. Foundation PreparationA properly prepared foundation, to support the footing plates, is essential fora successful Mini-Span installation. The elevation, grade and alignment of thefooting plates are dependant on the foundation.Foundation material of poor or non-uniform bearing capacity must beremoved to prevent differential footing settlement. Replacement foundationsoils must provide a uniform and relatively yielding support.2. Footing DesignMini-Span structures are typically designed so that the footing plates beardirectly on the foundation or bedding. If required, a concrete footing should bedesigned by a local qualified structural engineer, using available soils data,un-factored footing loads provided by Armtec, and appropriate design methods.It’s the responsibility of the owner to determine the scour line of the creek, andposition the footings and detail rock armour accordingly.3. Assembly and InstallationMini-Span structures are preassembled and lifted into place on the preparedfoundation. The total assembled weight of the structure is noted on the Bill ofMaterial. Factory installed lifting lugs are provided. Slings must be of sufficientlength such that the lifting angle is no flatter than a 1 (horizontal): 2 (vertical)slope, to prevent overstressing the lifting lugs.If concrete footings are required, the Mini-Span is lowered onto the cast-inplaceor precast footings after they are installed to the correct grade andalignment. Holes shall be drilled into the top surface of the footings, matchingthe holes pre-drilled in the footing plate. The footing plate is then bolted to thefooting using 12.5mmø x 100lg anchor bolts.4. Backfill and Footing ProtectionTo protect the critical backfill, a geotextile should be placed on the outside ofthe structure, over the granular foundation and footing plate. To protect thefootings and foundation from scour, a layer of angular armour rock/rip rapshould be placed inside the structure, above the footing plates. The owner’sengineer shall make site specific recommendations for scour protection.mini-span bridge
300 LOOSE CUSHION ARCHmini-span bridgesINSTALLATION (CONTINUED)5. Backfilling & CompactingIVE LOAD AS PROVIDED BY ENGINEEROTINGAreas close to the sides of the structure shall be compacted using vibrating ortamping equipment running parallel with the length of structure at all times.Granular fill material shall be at optimum moisture content during compaction.Each fill layer shall be compacted to at least 95% standard proctor density.PLACE AND COMPACT GRANULAR BACKFILLIN 200MM LIFTS TO 95% STANDARD PROCTORDENSITY (MIN)When the backfill reaches 3/4 of the rise, spreading and compaction over thetop STREAM arc must BED be made in a direction perpendicular to the length of the300 LOOSE CUSHION ARCHstructure (parallel to corrugations) until the finished height of the criticalSTIFFENING RIBbackfill zone is reached.300 MINRIP RAPA minimum of 300mm of backfill must exist at all times between the spreadingequipment and the structure. This layer of backfill must be built up evenly fromboth sides. The equipment used shall not be heavier than a D-4 Caterpillardozer (7,250kg) for spreading material and not heavier than a Buffalo-BomagBW-755 for compaction.If the backfill is not to be placed immediately EQUIPMENT BUT to the NOT finished elevation, aLESS THAN 600 (TYP)wearing and traveling surface is to be built over the critical backfill zone inorder to maintain a minimum allowable cover.INSIDE SPAN2 X INSIDE SPANTypical Backfill EnvelopeSTREAM BED300 MINRIP RAPSTIFFENING RIBTO SUIT COMPACTION½ SPAN MINLIVE LOAD AS PROVIDED BY ENGINEERBACKFILLING PERPENDICULARTO LENGTH OF STRUCTURE¾ RISE BACKFILLINGPARALLEL TO LENGTHOF STRUCTUREBACKFILLING PERPENDICULARTO LENGTH OF STRUCTUREARMTEC 200NON-WOVENGEOTEXTILE¾ RISE BACKFILLINGPARALLEL TO LENGTHOF STRUCTURE_NOTEAll dimensions are in millimetresunless otherwise notedBackfill and compaction parallelto arch up to 3/4 rise above topof footingBackfill and compaction perpendicularto arch from 3/4 rise above top offooting to finished gradePLACE AND COMPACT GRANULAR BACKFILLIN 200MM LIFTS TO 95% STANDARD PROCTORDENSITY (MIN)TINGINSIDE RISE COVERINSIDE SPAN2 X INSIDE SPAN300TO SUIT COMPACTIONEQUIPMENT BUT NOTLESS THAN 600 (TYP)½ SPAN MINSTREAM BED300 MINRIP RAPARMTEC 200NON-WOVENGEOTEXTILE300 LOOSE CUSHION ARCHSTIFFENING RIBBACKFILLING PERPENDICULARTO LENGTH OF STRUCTURE¾ RISE BACKFILLINGPARALLEL TO LENGTHOF STRUCTUREANCHOR BOLTS(12.5mmø x 100mm LONG)AT 1m O/CCONCRETE FOOTING(BY OTHERS)TO SUIT COMPACTIONEQUIPMENT BUT NOTLESS THAN 600 (TYP)ARMTEC 200NON-WOVENGEOTEXTILE½ SPAN MININSIDE SPAN½ SPAN MIN2 X INSIDE SPAN
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Mini-span Bridges / technical guide - Armtec

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