Your Dam Your Responsibility (PDF~1.2MB)

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5 Construction of a <strong>Dam</strong> is inviting trouble! Remember that tracked plant has tracks in order to keep the contact pressure low (for example, to cross soft ground), whereas what is required for good compaction is a combination of much higher contact pressures and ability to penetrate layers and knead them to ensure good bonding and eliminate leakage paths. Proper compaction plant is designed to do these things. Remember bulldozers, scrapers and tractors may be large machines but they are not designed for soil compaction. In fact, they are designed to create minimum pressure. Good compaction is achieved using appropriate compaction rollers on soil at just the right amount of moisture content. 5.5 Outlet Pipes or Structures in Embankment Outlet pipes under the dam wall are used for the controlled release of water from the dam. If not properly installed, they can readily provide a path for leakage from the dam, resulting in failure of the embankment and uncontrolled release of water. 5 Proper installation requires the backfilling and compaction to be carried out with extreme care. Using cut-off ‘collars’ at intervals along pipes Refer Compensation Flow Section 4.5.2. passing under a bank can reduce the possibility of leakage. However, special care is required to ensure adequate compaction in these areas, and this may require (among other things) the use of special small equipment. Outlet pipes or other works should be placed in original ground rather than in the embankment. As far as possible, the location of such structures in the embankment itself should be avoided. It is likely that they will be damaged during construction of the embankment and/or when any settlement occurs, but such damage will be unseen. Because of difficulties with compacting backfill properly around an outlet pipe it is better to backfill with concrete. Appendix C outlines the procedure. Never use sand or other granular material as pipe backfill or bedding. Warning: Even if these suggested practices are used, great care is required, especially if such items are incorporated in embankments or foundations of dispersive clays. It is then highly likely that failure will result, unless special care, overseen by an expert, is applied. Ideally, steel pipe with cement mortar lining should be used and backfilled with concrete. Unlined steel pipe can corrode and perforate within 20 years and lead to internal erosion of the embankment or abutment and result in dam failure. The use of concrete cutoff collars and an upstream guard valve is considered to be highly desirable, but such features themselves create an additional need for special care and attention to detail in both design and implementation. 25
26 5 5.6 5 Construction Spillways of a <strong>Dam</strong> 5.6 Spillways When selecting a site for the construction of a spillway, care should be taken to choose an area where there has been no previous disturbance of the natural ground. The usual site is near one of the dam’s abutments. However, spillways should be confined to locations clear of the embankment so that no flow is likely to go onto and damage the dam wall.
Page 1 and 2: Irrigation and Commercial Farm Dams
Page 3 and 4: ii Published by the Victorian Gover
Page 5 and 6: iv Contents 6 Safety Surveillance .
Page 8 and 9: 1 Introduction It makes good busine
Page 10 and 11: 2 Risks Posed by Dams 2.1 Owner’s
Page 12 and 13: 2 Risks Posed by Dams The most comm
Page 14 and 15: 2 Risks Posed by Dams 2 Note: The r
Page 16 and 17: 3 Licensing Requirements for Farm D
Page 18 and 19: 3 Licensing Requirements for Farm D
Page 20 and 21: 4 Planning to Build a Dam It is imp
Page 22 and 23: 4 Planning to Build a Dam 4.3 Types
Page 24 and 25: 4 Planning to Build a Dam 4 2. Turk
Page 26 and 27: 4 Planning to Build a Dam becomes a
Page 28 and 29: 4 Planning to Build a Dam 4.6.2 Ext
Page 30 and 31: 5 Construction of a Dam Mixing tops
Page 34 and 35: 6 Safety Surveillance 6.1 Purpose o
Page 36 and 37: 6 Safety Surveillance QUICK VISUAL
Page 38 and 39: 6 Safety Surveillance 6 Warning: If
Page 40 and 41: 7 Operation and Maintenance of Dams
Page 48 and 49: 8 Dam Failure Emergency Section 8 i
Page 50 and 51: 8 Dam Failure Emergency Action 4. I
Page 52 and 53: 9 Decommissioning of Dams 9 The sit
Page 54 and 55: 10 Glossary of Terms Cut-off An imp
Page 56 and 57: 10 Glossary of Terms Monitoring Rec
Page 58 and 59: Publications directly relevant to f
Page 60 and 61: Appendix A A • probe - a ten-mill
Page 62 and 63: Appendix A Inspection Procedures Ge
Page 64 and 65: Appendix A A and the resistance to
Page 66 and 67: Appendix B 1. Seepage Problem Possi
Page 68 and 69: Appendix B Problem Possible Causes
Page 72 and 73: Appendix B 2. Cracking, Deformation
Page 76 and 77: Appendix B 3. Miscellaneous Problem
Page 78 and 79: Appendix B utlet Works and Concrete
Page 80 and 81: Appendix C The depth of the core tr
Page 82 and 83:
Appendix C will be needed. In stabl
Page 84 and 85:
Appendix C The width of the dischar
Page 86 and 87:
Appendix C Other Pipe Details At th
Page 88 and 89:
D Figure C-4: Design guide for a fa
Page 90:
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