Long-term behaviour of dams that have experienced internal erosion (sinkholes)
|Timing of internal erosion incident:
||Generally during first filling or within first year. There are also rockfill dams where incidents occurred years into operation.
||Generally a few years into operation or after several years.
|Possible early-warning sign:
||Increase in leakage, Muddy leakage, Pore-pressure variations
|Possible warning-time between first sign and internal erosion incident:
||Account for the majority of dams with no warning, or up to days–weeks “warning-time”. However, there are also rockfill dams where there have been months or longer “warning-time”.
||Generally months or longer between first sign and the incident.
|Location of internal erosion incident:
||Higher incidence where dams: i) abut to concrete structures and/or sheet pile walls, and ii) are placed on irregular foundation.