USSD Rio Descoberto Dam - Sabino Freitas Correa-ENGL -

More documents

Recommendations

Info

INTRODUCTION - PROBLEM PRESENTATION General Dam Construction Data PROBLEM PRESENTATION The Rio Descoberto Dam is located at 50 Km west from Brasília City`s downtown, and can be accessed by the BR-070 state asphalted road. The dam is used as a reservoir for Brazil´s Capital (Brasília City) water supply. The spillway stet capacity is 102,900,000 cubic meters, and approximately 60% of the local population water consummation is supplied by the Descoberto reservoir, serving up to 1,200,000 people. The dam is concrete gravity mass type with 54,500 cubic meters total concrete body mass. The typical section is trapezoidal with a top elongation, 3 meter crest width, 33 meter maximum height and 265 meter length (see cross section at fig. 4b.). The Rio Descoberto Dam´s body can be divided in three main parts, the 125 meter length left abutment, 85 meter length right abutment and the 55 meter length central spillway (see pic. 01 below). The spillway is “Creager” type with a type II USBR stilling basin. The construction was performed by blocks, separated by contraction joints, between the years of 1971 and 1974. The blocks pouring sequence was intercalated. The contraction joints used were “O” type waterstop Fugenband. The dam is composed by 18 blocks, named “A” to “R”. All the blocks are 15 meter wide, with an exception of “A” (10 meter in width). The crest level is at 1,034 m and the spillway level is at 1,030 m. Figure 01 – Rio Descoberto Dam Plant (above) and upstream view
Opening Remarks The consequences of pyrite composed concrete aggregate was known by the Descoberto Dam designers by the time of construction, but the low experience at that time with those reactivity problems, allowed the use of a low level pyrite concrete aggregate in this construction work. Posterior happenings including the pathologies observed at this dam, and the Fonsagrada Dam collapse report from Spain, demonstrated however, that even very low pyrite levels on hydraulic structures concrete aggregate may cause serious problems. A few years after filling the reservoir, leakages started to be observed at the downstream block “I” face. In the end of the 70´s decade, some wide fissures started to be observed too. From that time, until the performance of this project in 2000, the water leakage increased strongly, becoming into long horizontal leaching surfaces across the dam section. Chronology From the first problems appearing until the full rehabilitation diaphragm works, started in 2000, three remedial interventions were performed, without remarkable success. Those interventions were based on epoxy and grout injections. The resume of this chronology is displayed at the figure 2, below: 1 st . Intervention Figure 2, intervention chronology Since the mid 70´s decade leakages were observed at “I” block’s downstream face. In 1981, as usual in leakage dam treatment method, the first intervention was performed. The solution was based in epoxy injections applied from the downstream face. 2 nd . Intervention Between 1989 October and 1990 July, the second intervention was performed. The works were guided by a preliminary diagnose report made in 1988, this report indicated concreting joints failures as the origin of the problem. Those works consisted in the combination of grout injection filling at the upstream face with
Page 1: RIO DESCOBERTO DAM - "IN THE WET" R
Page 5 and 6: Picture 1.a (left) and 1.b (right):
Page 7 and 8: First Evaluations Before the beginn
Page 9 and 10: Diaphragm Continuity The continuity

USSD Rio Descoberto Dam - Sabino Freitas Correa-ENGL -

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?