RING DEFLECTION OF BURIED PIPE

RESEARCH WAS CONDUCTED TO DEVELOP A METHOD BASED ON RING DEFLECTION FOR STRUCTURAL DESIGN FOR CEMENT-MORTAR LINED (CML) AND CEMENT-MORTAR LINED AND CEMENT-MORTAR COATED (CML- CMC) STEEL PIPE. EXPERIENCE BY SUPPLIERS OF THESE PIPE INDICATED THAT THE PRIMARY CONCERN FOR STRUCTURAL FAILURE IS FLEXURAL CRACKING OF THE MORTAR COATING. THIS PROJECT IS BASED ON THE PREMISE THAT FAILURE OF CML AND CML-CMC PIPE IS SOME MAXIMUM ALLOWABLE RING DEFLECTION BEYOND WHICH MORTAR CRACKING IS EXCESSIVE. FIELD AND LABORATORY TEST WERE CONDUCTED FOR (1) THE DEVELOPMENT OF A RELATIONSHIP BY WHICH RING DEFLECTION CAN BE PREDICTED AS A FUNCTION OF DIMENSIONLESS PARAMETERS BASED ON SOIL PROPERTIES AND PIPE PROPERTIES, AND (2) THE RELATIONSHIP BETWEEN CRACKING OF THE MORTAR AND RING DEFLECTION FOR THE PARTICULAR PIPE TESTED. TEN-FT LONG SECTIONS OF CML AND CML-CMC PIPE AND BARE PIPES WERE BURIED UNDER CAREFULLY CONTROLLED SOIL CONDITIONS AND THE RING DEFLECTIONS IN CRACKING PATTERNS WERE OBSERVED FOR VARIOUS LOADS AND SOIL TYPES. AFTER THE PIPE DIAMETER AND WALL THICKNESS HAVE BEEN SELECTED, IT IS CONCLUDED THAT THE DESIGNER SHOULD PREDICT RING DEFLECTION FOR A TRIAL PIPE SECTION. SUCH PREDICTIONS DEPEND UPON KNOWING THE VERTICAL SOIL PRESSURE AND THE CORRESPONDING VERTICAL SOIL STRAIN FOR THE SPECIFIED SOIL DENSITY. THE PREDICTED RING DEFLECTION MUST BE LESS THAN FAILURE DEFLECTION BY SOME FACTOR OF SAFETY. A SAFETY FACTOR OF 1.5 USED IN THE DESIGN ON RIGID PIPE IS RECOMMENDED HERE. IN THE EVENT THAT HIGH FILLS CANNOT BE AVOIDED, A SIMPLE WAY TO PROTECT THE PIPE AGAINST HIGH SOIL PRESSURE IS TO LEAVE A LOOSE-SOIL BLANKET ABOUT THE PIPE BY KEEPING COMPACTORS A SPECIFIED DISTANCE AWAY. OUTSIDE OF THE LOOSE-SOIL BLANKET, HOWEVER, THE SOIL SHOULD BE COMPACTED ENOUGH TO PREVENT A SOIL STRAIN GREATER THAN TWICE THE ALLOWABLE RING DEFLECTION. IF THIS IS DONE THERE IS NO LIMIT TO THE HEIGHT OF FILL.

• Supplemental Notes:
  • Vol 59, No 3, PP 367-378, 7 FIG, 3 TAB, 5 REF, 1 APP
• Authors:
  • Watkins, R K
  • Smith, A B
• Publication Date: 1967-3

Media Info

• Serial:
  • Journal Awwa

Subject/Index Terms

• TRT Terms: Bedding; Cement mortars; Coatings; Deflection; Diameter; Earth pressure; Fills; Flexure; Fracture mechanics; Height; Properties of materials; Safety factors; Soil densification; Soils; Steel pipe; Structural design; Thickness
• Uncontrolled Terms: Soil properties
• Old TRIS Terms: Liners; Rings
• Subject Areas: Geotechnology; Highways; Materials; Safety and Human Factors;

Filing Info

• Accession Number: 00216294
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 12 1970 12:00AM