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REGISTRO ITALIANO DIGHE

Ufficio Periferico di Cagliari

versione italiana


 

El Cajón (or Francisco Morazán) Dam

 

 

Country

Honduras

River

Humuya

Dam type

Double curvature concrete arch

Construction period

1980-1985

Structural height

226 m

Gross storage capacity

5,700 Mm³

Active storage capacity

4,200 Mm³

Volume of the dam

1.480.000 m³

Maximum controllable water surface

295.00 m a.s.l.

Normal supply level

285.00 m a.s.l.

Crest elevation

301.00 m a.s.l.

Crest length

382 m

Maximum discharge capacity

Gated spillway (threshold at el. 251 m a.s.l.): 5,900 m³/s;

Free spillway (threshold at el. 295 m a.s.l.): about 1,500 m³/s;

3 bottom outlets at el. 170 m a.s.l.: about 2,400 m³/s;

Power plant: about 100 m³/s

Nameplate capacity of the powerplant

300 MW (4 units, each of 75 MW)

Notes

El Cajón (or Francisco Morazán) Dam is the highest dam in Central America and one of the world’s highest. It’s named after the Honduran hero General Francisco Morazán (1792-1842), who was the president of the United Provinces of Central America from 1830 to 1840.

At El Cajón Dam, an unusually extensive grout curtain of the bathtub type was established. The massive and moderately karstified limestone foundation was injected with 100,000 metric tons of cement, in one thick stable mix, using pressures up to 50 bar. The approximate surface area of the curtain is 530,000 m².

In the design of El Cajón Dam, the effect of possible cavitation was considered unlikely to seriously alter the overall response of the dam. On the contrary, as soon as the reservoir filled up in 1986, some problems became evident. The heavy water pressure caused cracks to form in the grout curtain. Water began seeping through and eroding the limestone under the dam. By 1993, water was pouring in at the rate of 1,600 liters per second.

Hundreds of holes, up to 250 meters deep, were drilled from the dam base into the limestone and many tons of different combinations of cement, sand and gravel grouting were injected. But most of it just ran through because of the pressure produced by the high head of water behind the dam. So, it was decided to inject larger objects (about 5 to 7 cm.) that would stick inside the fissures and karsts and prevent the grouting from passing through before hardening.

First, 8,650 plastic and wooden balls were injected, but while the balls remained in place, they didn’t hold back enough of the cement grout material injected to plug the cavities. Lastly, 25,000 rolled up polypropylene feed sacks were injected into the drill holes to create a mesh, by spreading out, inside the cavities, and in this way prevent the cement grout from passing through. This solution proved effective. Leaking was reduced from 1,600 to less than 100 liters per second.

 

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Pagina creata da Luigi Ghinami email

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Ultimo aggiornamento: 4 agosto 2005