Transcript TETON DAM FAILURE PPP

TETON DAM FAILURE
Group 22
Jayson Ladd
Paddy Mac Cormack
Elaine Casey
Sadhbh Ni Hogain
INTRODUCTION
• On June 5th 1976 the TETON DAM failed
suddenly
• Located 44 miles northeast of Idaho Falls in
south-eastern Idaho
• It claimed the life of 14 people and caused
hundreds of millions of dollars in damage.
• Failure was due to a leak near the abutment of
the dam, about 130 feet below the crest
Flood waters advancing through Rexburg, Idaho
SITE HISTORY
• The first site investigation in the area took place in 1932 yet work
on the dam did not begin until early 1972
• The Teton Dam is located on the Snake River Plain, a broad
tectonic depression underlain by rhyolitic and basaltic volcanic
rocks
• The volcanic rock at the dam site consists of hard, welded,
rhyolitic ash-flow tuff dated at 1.9 million years.
• It has a hard ash-flow turf and sits upon think sedimentary rock
• This geological configuration causes a high level of permeability
in the surrounding area.
CONSTRUCTION
• The earth fill dam required 10 million cubic meters of materials, most
of which was dug from the river bed around the site
• The dam consisted of a centre zone made up of clay, silt, gravel and
cobbles mixture tightly compacted by tamping rollers
The Five zones of the Dam:
• Zone 1:
• Zone 2:
• Zone 3:
• Zone4\5:
Core - Moisture content 1.5% dry of optimum
permeability 0.3 m/yr
Compacted Sandy Gravel – Overlies Zone 1 and
extends downstream into the floodplain
Miscellaneous Fill – Properties similar to Zone 1
Rock Fill-Compacted on outer surface of dam
View northwest toward right abutment.
The hole in the dam face enlarges upward
View northwest toward right abutment.
Muddy water issues out of the hole about
two-thirds up the face of the dam and
begins to pond at the toe
The hole in the dam face continues to enlarge
upward near the crest of the dam, the rush
of water increases markedly, and erosion
cuts deep into bedrock of the abutment
COLLAPSE
• Failure occurred rapidly with out much advance warning
• June 3rd: small seepages become visible in the north abutment wall
• June 5th: the first major leak was noticed on the right abutment with
a flow of about 500 to 800 l/s which increased to 1,400 l/s. Seepage
was observed about 40 meters below the crest of the dam.
• At 11am a whirlpool was noticed 5m from the edge of the
embankment.
• At 11.30am bulldozers filling the hole on the embankment were lost
• The dam finally broke at 11.57am
• The 251,000 acres were emptied within 5 hours
CONCLUSIONS
•
The dam failed due to internal erosion of the core of the dam deep in
the foundation
•
Eroded particles found exits through the channels in and along the
interface of the dam, exits existed through cracks in the core
•
The design team did not believe that these cracks were sufficient to
cause failure but the build up of water pressure pushed the waster
through
•
Politics played a huge part in pushing on this project and as a result
design mistakes were made, which ultimately caused the failure of the
dam
•
A report in 1947 showed that none of the site investigations were
sufficient
•
“It was shown that the reservoir rim could transmit water in large
quantities and that seepage form the reservoir could occur.”