END SILLS AND THE FORCE HYDRAULIC JUMP IN CIRCULAR CULVERTS OPERATING AT LOW DISCHARGE FACTORS

THE PERFORMANCE WAS STUDIED OF A RECTANGULAR END SILL IN STABILIZING A HYDRAULIC JUMP A PRESCRIBED DISTANCE INSIDE A BROKEN-BACK CULVERT AND IN DISTRIBUTING THE FLOW AT THE CULVERT OUTLET ACROSS THE DOWNSTREAM CHANNEL WIDTH. WITH A SILL OF PROPER HEIGHT LOCATED BETWEEN THE FLARED WING WALLS AT THE CULVERT OUTLET, THE SUPERCRITICAL FLOW USUALLY PRESENT IN A BROKEN-BACK CULVERT CAN BE CHANGED TO SUBCRITICAL THROUGH FORCED HYDRAULIC JUMP WITHIN THE PIPE. EXPERIMENTS WITH THE MODEL BROKEN-BACK CULVERTS WERE RUN TO DETERMINE THE SILL HEIGHT TO CULVERTS GEOMETRY RELATIONSHIP, THE MOST DESIRABLE SILL LOCATION WITHIN THE WING WALLS, AND THE EFFECTIVENESS OF THE RECTANGULAR SILL IN DISTRIBUTING THE CULVERT FLOW. THE DISCHARGE FACTOR, CULVERT GEOMETRY, AND SILL LOCATION WERE ALL VARIED SYSTEMATICALLY SO THAT EACH OF THEIR AFFECTS ON THE SILL HEIGHT TO HYDRAULIC JUMP RELATIONSHIP COULD BE DETERMINED. VELOCITY AND DEPTH MEASUREMENTS ACROSS VARIOUS SECTIONS IN THE CHANNEL DOWNSTREAM OF THE SILLS WERE USEFUL IN DETERMINING THE MOST DESIRABLE SILL LOCATION WITHIN THE FLARED WING WALLS AND IN ESTIMATING THE EFFECTIVENESS OF THE SILLS IN DISTRIBUTING THIS FLOW. A CONSISTENT RELATIONSHIP APPEARS TO EXIST BETWEEN SILL HEIGHT AND CULVERT GEOMETRY FOR A GIVEN DISCHARGE FACTOR IN A GIVEN SILL LOCATION. CONSIDERING SILL LOCATIONS, THE SILL AT THE CULVERT OUTLET IS PROBABLY THE LEAST DESIRABLE BECAUSE OF MAINTENANCE PROBLEMS POSED WHEN DEBRIS & ERODED MATERIAL ARE DEPOSITED BY FLOOD WATERS IN THE CULVERT. THE SILL AT THE MID-POINT OF THE FLARED WING WALLS APPEARS TO BE MOST DESIRABLE SINCE LESS ADDITIONAL CHANNEL PROTECTION IMMEDIATELY DOWNSTREAM OF SUCH A SILL IS REQUIRED. SLIGHTLY LESS SILL HEIGHT IS REQUIRED BY SILL AT THE MID-POINT OF THE WING WALLS THAN ONE AT THE END OF THE WING WALLS, HOWEVER, THE SILL AT THE END OF THE WSNG WALL IS MORE EFFECTIVE IN SPREADING THE FLOW ACROSS THE DOWNSTREAM CHANNEL WITHIN A SHORTER DISTANCE. WITH THE SILL LOCATED AT EITHER OF THE MID-POINT OR END OF THE WING WALLS, AN AVERAGE OF 80 PERCENT ENERGY REDUCTION WAS MEASURED BETWEEN THE END OF THE SLOPED PORTION OF THE BROKEN-BACK CULVERT IN A SECTION DOWNSTREAM OF THE SILLS.

  • Supplemental Notes:
    • Rpt 92-4, 91 PP, 49 FIG, 3 TAB, 2 REF
  • Corporate Authors:

    University of Texas, Austin

    Center for Highway Research, 200 West 21st Street
    Austin, TX  USA  78712
  • Authors:
    • Brandes, R J
    • Rao, M V
    • Masch, F D
  • Publication Date: 1969-1

Subject/Index Terms

Filing Info

  • Accession Number: 00204284
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 3 1970 12:00AM