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Pertemuan 10Bangunan Air

Matakuliah : S0182/Studi Kasus Dalam Teknik Sipil

Tahun : Juli 2005

Versi : 01/01

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Learning Outcomes

Mahasiswa dapat membandingkan kasus-kasus yang terjadi dengan berbagai alternatif yang dipilih C4

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Outline Materi

• Analisa pemecahan masalah

• Beberapa alternatif pemecahan masalah

• Kasus kegagalan konstruksi yang mungkin terjadi

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DAM FAILURE

Teton Dam Failure• The Teton Dam, 44 miles northeast of Idaho Falls in southeastern Idaho,

failed abruptly on June 5, 1976. It released nearly 300,000 acre feet of water, then flooded farmland and towns downstream with the eventual loss of 14 lives, directly or indirectly, and with a cost estimated to be nearly $1 billion.

• The purpose of this web page is to present a series of slides that show the breakup of the dam from its incipient failure stage to when the dam was completely breached. The slides were taken by Mrs. Eunice Olson of St. Anthony, Idaho, who presented the set to the Department of Earth Sciences, University of Notre Dame, to sell and to subsidize, thereby, a scholarship for undergraduate students in Earth sciences. The department, now the Department of Engineering and Geological Sciences, no longer sells the set, and has unofficially agreed that it would be a good thing to place this unique collection on the web. Attempts to contact Mrs.Olson have been unsuccessful, but nevertheless, all credit for the break up sequence of slides belongs to her.

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DAM FAILURE

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• Over 100 years ago, a catastrophic dam failure caused thousands of deaths and wiped out a town. Before the failure:

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CASE STUDY DAM

• dam type: double curvature concrete arch buttress purpose: water supply and regulation

• height: 440 ft (134 m)

• width at foundation: 171.6 ft (52.3 m)

• length of crest: 1312 ft (400 m)

• storage capacity: 344,000 acre-ft.

El Atazar

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CASE STUDY DAM

• The dam may also have served the people by producing electric power, but the decision was made to confine its purpose to water supply.

location: near Madrid, Spain • river: Lozoya, very close to where it joins the Jarama River • foundation: Silurian shale • Three joint systems pass through this foundation.

construction start date: 1968 • construction end date: 1972 • first partial reservoir filling: 1970 • Maximum storage is 870 m above sea level. Filling began when the

diversion tunnel was closed. It filled to 824 m above sea level in 1971 and then to 860 m in 1972. Questionnable behavior began to occur during the filling between 1971 and 1972.

El Atazar

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CASE STUDY DAM

El Atazar

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CASE STUDY DAM

El Atazar

•Monitoring of the dam revealed movement, often normal in dams. But the left side was moving more than the right. This was because the left abutment was a hillside, more deformable than the right abutment. Also, a support had been built on the right side of the dam, making that side more stiff (and less moveable). •In 1977, a crack was noticed just left of the center of the dam about 98.4 ft (30 m) above the foundation on the upstream side of the dam. This is noted as one of the worst places for cracking to occur in an arch dam. Water was now leaking out through the crack into drains in the dam at a rate of 53 ft3/min. •In February of 1978, the leak increased to a rate of 318 ft3/min as a result of heavy rain.

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CASE STUDY DAM

El Atazar

•The crack grew almost 150 ft both to the left and to the right and could be seen from one of the dam's inspection galleries. •In 1979, the crack was repaired. •In 1980, maximum storage was reached. •In 1983, it was found that settling had occurred in the foundations and the movements of the dam caused fracturing in the rock. The permeability of the foundation had increased significantly. •Treatment of the foundation has decreased the movements and the foundation.

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CASE STUDY DAM

El Atazar

El Atazar Current Status•The analysis of three-dimensional structures such as concrete arch dams was demonstrated with the simulation of El Atazar dam and showed the applicability of fracture mechanics to such structures. •Arch dams are critically sensitive to their foundations, again proven by this case. The computer simulation demonstrates the increase in stress on the upstream face when one of the abutments is weak, resulting in cracking. •Researchers acknowledged the need improvements in three-dimensional crack growth analysis.