Analysis Crest Cutoff Wall at Ostrovul Mic - YRC 2013 Presentation

8/13/2019 Analysis Crest Cutoff Wall at Ostrovul Mic - YRC 2013 Presentation

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Presentation Content

I. Brief description of the site and of the encountered phenomena

II. Aim of the analysis

III. Mathematical models used to analyze the efficiency of the cutoff wall

IV. Calibration of the mathematical model

V. 2D vertical and horizontal analysis

VI. Conclusions


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Site description

Ostrovul Mic hydropower development, first of the Rul Mare Aval scheme, is

situated at about 20 km from Haegtown.

The development is composed of a weir dam, a hydroelectric power plant and the

perimeter dams.

The main purposes of the development are: the production of electrical energy, the

regulation of the Raul Mare River and irrigation.

NRL: 465.00 maSL

Crest elevation: 468.00 maSL

Water volume : 5.80 mil mc

Installed flow : 90 mc/s

Dikes length : 3.80 km


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The encountered phenomena

Seepage problems since commission (1986)

Concentrated springs

Large wet areas

Piping phenomena

Seepage flow : 140 l/s


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Aim of the study

To analyze the efficiency of the proposed solution regarding the seepage flow, the

spring level, the critical gradient and the influence of the proposed length of thecutoff wall.


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Mathematical model 2D vertical and horizontal analysis

Distante (X)

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625

Distante(Y)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

4579 finite elements

4549 modes

12580 finite elements

Boundary conditions (for both models):

Upstream: lake water level equal to the normal retention level (465.00 maSL)

Downstream: 1 m water level in the downstream channel (449.00 maSL)

potential spring area on the downstream slope.


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Model calibration emergence elevation of the seepage curve

Main causes the deteriorated slabs on the lower part of the concrete face

the damaged joint between the concrete face and the cutoff wall

flexible and

nondestructive in

situ measurements

infrared photography


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2D vertical analysis of the crest cutoff wall

4504

52

454

4 5 6

458

460

462

46

4

Cota lac: 465.00 mdM

Cota coronament : 466.80 mdM

Distante orizontale

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Co

te

425

430

435

440

445

450

455

460

465

470

475

480



Distante orizontale

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Cote

425

430

435

440

445

450

455

460

465

470

475

480

450

452

454

4 5 6 4

58

4 6 04

62

464



Distante orizontale

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

Cote

425

430

435

440

445

450

455

460

465

470

475

480

1. Perfect execution

2. Lack of embedding (0,50 m)

3. Presence of a window (0,50 m)

flow: 0,037 l/s m spring el.in the channel

i < icritical

flow: 0,419 l/s m

spring el. in the channel

i < icritical

flow: 0,494 l/s m

spring el. 0.50 m above the berm

i < icritical


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2D horizontal analysis of the crest cutoff wall

Distante (X)

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625

Dista

nte(Y)

0

10

20

30

40

50

60

7080

90

100

110

120

130

140

150

160

170

Distante (X)

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625

Distante(Y)

0

10

20

30

40

50

60

70

80

90

100

110

120130

140

150

160

170

Distante (X)

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 575 600 625

Distante(Y)

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

170

1. Perfect execution

2. Presence of a window

3. Reduced length (150 m)


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Conclusions

The seepage phenomenon through the dikes of the Ostrovul Mic Lake is a continuous and

intensity increasing process followed by the fine material picking up. This is the cause ofthe restricted water level operating mode since the commissioning of the development.

The seepage analysis was based on two 2D finite elements models using Geostudio

software. The calibration was realized using the emergence rate of the downstream

parameter depression curve. To determine its value in situ, infrared image technique was

used. The proposed solution for the sealing of the left side dike crest cutoff wall was

analyzed in both the situation when the execution was perfect and the situation in which

some defects may appear in its body. As a result of the mathematical modeling, this

solution offers a complete seepage control, even if the execution of the cutoff wall is not

perfect.


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Thank you for your attention !

Documents

Analysis Crest Cutoff Wall at Ostrovul Mic - YRC 2013 Presentation