Historically, all types of dams have experienced failures due to one or more types of event/loading. However, by far the majority of dam failures that have occurred have been earthen dams, caused by some level of flood. The types of dams that are commonly built and found in the field are:
- Earthen embankment/rockfill
- Concrete arch and multi arch
- Concrete gravity
- Buttress (combination of concrete gravity and arch dam)
- Steel, timber, and composite materials
There are many mechanisms that can be the driving force of a dam failure. The following is a list of mechanisms that can cause dam failures:
- Flood event
- Piping/seepage (internal and underneath the dam)
- Land slide
- Earthquake
- Foundation failure
- Equipment failure/malfunction (gates, etc…)
- Structural failure
- Upstream dam failure
- Rapid drawdown of pool
- Sabotage
- Planned removal
Given the different mechanisms that cause dam failures, there can be several possible ways a dam may fail for a given driving force/mechanism. Table 14-1 shows a list of dam types versus possible modes of failure (Costa, 1985, and Atallah, 2002).
Table 13-1. Possible failure modes for various dam types.
Failure Mode | Earthen/
Embankment | Concrete
Gravity | Concrete
Arch | Concrete
Buttress | Concrete
Multi-Arch |
|---|
Overtopping | X | X | X | X | X |
Piping/Seepage | X | X | X | X | X |
Foundation Defects | X | X | X | X | X |
Sliding | X | X |
| X |
|
Overturning |
| X | X |
|
|
Cracking | X | X | X | X | X |
Equipment failure | X | X | X | X | X |
Costa (1985) reports that of all dam failures as of 1985, 34% were caused by overtopping, 30% due to foundation defects, 28% from piping and seepage, and 8% from other modes of failure. Costa (1985) also reports that for earth/embankment dams only, 35% have failed due to overtopping, 38% from piping and seepage, 21% from foundation defects; and 6% from other failure modes.