Your Dam Your Responsibility (PDF~1.2MB)
Your Dam Your Responsibility (PDF~1.2MB) Your Dam Your Responsibility (PDF~1.2MB)
Appendix B 1. Seepage Problem Possible Causes and Potential Harm Seepage water exiting from a point on the embankment Large Seepage area producing flow Causes: 1. Water has created an open pathway, channel, (or “pipe”) through the dam. The water is eroding and carrying away embankment material. 2. Large amounts of water have accumulated in the downstream slope. Water and embankment materials are exiting at one point. 3. Rabbits, yabbies, rotting tree roots or poor construction have allowed water to create an open pathway or pipe through the embankment. Harm: 1. Continued flows can saturate portions of the embankment and lead to slides in the area. 2. Continued flows can further erode embankment materials. This can lead to failure of the dam. Cause: 1. A seepage path has developed directly through the embankment or via the abutment. Harm: 1. Increased flows could lead to erosion of embankment material and failure of the dam. 2. Saturation of the embankment can lead to local slides, which could cause failure of the dam. Action Required B Action: 1. Begin measuring outflow quantity and establishing whether water is getting muddier, staying the same, or clearing up, and whether the rate of flow is increasing or otherwise. 2. Check whether surface agitation may be causing the muddy water. 3. If quantity of flow is increasing, the water level in the dam should be lowered until the flow stabilises or stops. 4. Search for an opening on upstream side and plug it if possible with clay, but do not get into the water to do so! 5. Prevent rabbit activity. 6. A suitably qualified engineer should immediately inspect the condition and recommend further action to be taken. 1. Stake out the saturated area and monitor wet area for growth or shrinking. 2. Measure any outflows as accurately as possible. 3. Dam water level may need to be lowered if saturated areas increase in size at a fixed storage level or if flow increases. 4. A suitably qualified engineer should inspect the condition and recommend further actions to be taken. 59
60 B Appendix B Problem Possible Causes and Potential Harm Seepage exiting at abutment contact Wet area in a horizontal band in the embankment Cause: 1. Water flowing through pathways in the abutment. 2. Water flowing through the embankment and out via the abutment. 3. Water flowing along the contact surface between the embankment and its abutment. Harm: 1. Can lead to erosion of embankment materials and failure of the dam. Cause: 1. Layer of sandy material in original construction. Harm: 1. Wetting of areas below the area of excessive seepage can lead to localised instability of the embankment (slides). 2. Excessive flows can lead to accelerated erosion of embankment materials and failure of dam. Bulge in large wet area Cause: 1. Downstream embankment materials have begun to move. Harm: 1. Failure of the embankment due to massive sliding can follow these initial movements. Action Required Action: 1. Investigate leakage area to determine quantity of flow and extent of saturation. 2. Inspect daily for developing slides. 3. Water level in reservoir may need to be lowered to assure the safety of the embankment. 4. A suitably qualified engineer should inspect the conditions and recommend further actions to be taken. Action: 1. Determine as closely as possible the amount of flow being produced. 2. If flow increases, dam water level should be reduced until flow stabilises or stops. 3. Stake out the exact area involved. 4. Using hand tools, try to identify the material allowing the flow. A suitably qualified engineer should inspect the condition and recommend further actions to be taken. Action: 1. Compare the observed embankment cross-section with the end of construction condition to see if observed condition may reflect end of construction, or if it represents a subsequent movement. 2. Stake out affected area and accurately measure outflow. 3. A suitably qualified engineer should inspect the condition and recommend further actions to be taken.
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- Page 72 and 73: Appendix B 2. Cracking, Deformation
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- Page 76 and 77: Appendix B 3. Miscellaneous Problem
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- Page 80 and 81: Appendix C The depth of the core tr
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60<br />
B<br />
Appendix B<br />
Problem Possible Causes and<br />
Potential Harm<br />
Seepage exiting at<br />
abutment contact<br />
Wet area in a horizontal<br />
band in the embankment<br />
Cause:<br />
1. Water flowing through<br />
pathways in the abutment.<br />
2. Water flowing through the<br />
embankment and out via the<br />
abutment.<br />
3. Water flowing along the<br />
contact surface between<br />
the embankment and its<br />
abutment.<br />
Harm:<br />
1. Can lead to erosion of<br />
embankment materials and<br />
failure of the dam.<br />
Cause:<br />
1. Layer of sandy material in<br />
original construction.<br />
Harm:<br />
1. Wetting of areas below the<br />
area of excessive seepage can<br />
lead to localised instability of<br />
the embankment (slides).<br />
2. Excessive flows can lead<br />
to accelerated erosion of<br />
embankment materials and<br />
failure of dam.<br />
Bulge in large wet area Cause:<br />
1. Downstream embankment<br />
materials have begun to move.<br />
Harm:<br />
1. Failure of the embankment<br />
due to massive sliding can<br />
follow these initial movements.<br />
Action Required<br />
Action:<br />
1. Investigate leakage area to<br />
determine quantity of flow and<br />
extent of saturation.<br />
2. Inspect daily for developing<br />
slides.<br />
3. Water level in reservoir may<br />
need to be lowered to assure<br />
the safety of the embankment.<br />
4. A suitably qualified<br />
engineer should inspect the<br />
conditions and recommend<br />
further actions to be taken.<br />
Action:<br />
1. Determine as closely as<br />
possible the amount of flow<br />
being produced.<br />
2. If flow increases, dam water<br />
level should be reduced until<br />
flow stabilises or stops.<br />
3. Stake out the exact area<br />
involved.<br />
4. Using hand tools, try to identify<br />
the material allowing the flow.<br />
A suitably qualified<br />
engineer should inspect the<br />
condition and recommend<br />
further actions to be taken.<br />
Action:<br />
1. Compare the observed<br />
embankment cross-section<br />
with the end of construction<br />
condition to see if observed<br />
condition may reflect end of<br />
construction, or if it represents<br />
a subsequent movement.<br />
2. Stake out affected area and<br />
accurately measure outflow.<br />
3. A suitably qualified<br />
engineer should inspect the<br />
condition and recommend<br />
further actions to be taken.
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