A THEORY ON LOADS ON NEGATIVE PROJECTING CONDUITS
NEGATIVE PROJECTING CONDUITS ARE DEFINED AS THOSE WHICH ARE PLACED IN SHALLOW DITCHES OF SUCH DEPTH THAT THE TOP OF THE CONDUIT IS BELOW THE ADJACENT NATURAL GROUND SURFACE WHICH IS COVERED BY AN EMBANKMENT. THE THEORY IS PRESENTED FOR SUCH CONDUITS. IT FOLLOWS THE GENERAL PRINCIPLES DEVELOPED BY MARSTON IN THE THEORY OF LOADS ON POSITIVE PROJECTING CONDUITS, WHICH ARE THOSE IN WHICH THE CONDUIT IS PLACED IN SHALLOW BEDDING WITH THE TOP OF THE CONDUIT PROJECTING ABOVE THE NATURAL GROUND SURFACE, BUT UNDER AN EMBANKMENT. SINCE THE LOAD ON A NEGATIVE PROJECTING CONDUIT IS LESS THAN THAT ON A POSITIVE PROJECTING CONDUIT UNDER THE SAME FILL, THERE IS CONSIDERABLE ADVANTAGE IN THE NEGATIVE PROJECTION TYPE OF CONSTRUCTION. THIS THEORY MAY BE USED TO ESTIMATE LOADS ON CONDUITS INSTALLED BY THE IMPERFECT DITCH METHOD IN WHICH THE SOIL ON BOTH SIDES AND ABOVE THE CONDUIT FOR SOME DISTANCE ABOVE ITS TOP IS THOROUGHLY COMPACTED BY ROLLING AND TAMPING. THEN A DITCH IS DUG IN THIS COMPACTED FILL BY REMOVING THE PRISM OF MATERIAL DIRECTLY OVER THE CONDUIT. THE DITCH IS REFILLED WITH LOOSE COMPRESSIBLE MATERIAL, AFTER WHICH THE EMBANKMENT IS COMPLETED IN A NORMAL MANNER.
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Supplemental Notes:
- Vol 30, pp 153-161, 12 FIG, 4 REF. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
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Authors:
- Spangler, M G
- Publication Date: 1951
Media Info
- Media Type: Digital/other
- Monograph Title: Proceedings of the Thirtieth Annual Meeting of the Highway Research Board Held at Washington, D.C., January 9-12, 1951
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Serial:
- Highway Research Board Proceedings
- Volume: 30
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Conduits; Embankments; Estimates; Loads; Theory
- Old TRIS Terms: Imperfect trench method; Negative pressures; Projection
- Subject Areas: Highways; Hydraulics and Hydrology;
Filing Info
- Accession Number: 00204134
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Jan 23 1994 12:00AM