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