Evaluating permeability and groutability at the Karun 4 ... · Evaluating permeability and...

Evaluating permeability and groutability at the Karun

4 dam Iran using Lugeon values and grout Take

Mohammad Hosseiny Sohi1, Prof.Dr. Manfred Koch1, Dr. Javad Ashjari 2

1 Department of Geohydraulics and Engineering Hydrology, Kassel University, Kassel, Germany2 School of Geology, University of Tehran, Tehran, Iran

Contents

Introduction

Study area and dam specifications

Methodology and data

Results

Conclusions

References

Introduction

Water leakage through the foundation and abutments of a dam which is built on

limestone formations, is one of the most important challenges of the big dams’

construction and operation.

The water- soluble carbonate structure of such limestone may lead to the

development of fissures and fractures that may, eventually, expand to conduits

and even caverns and caves; a process which is known as karstification

(Milanović, 2004; Ford & Williams, 2007).

In the present study, the permeability as the most important parameter

determining water seepage of the Karun 4 dam, constructed on a limestone

formation with karst potential will be presented.

Study area and dam specifications

The Karun 4 Dam is located on the Karun River in the state of Chaharmahal and

Bakhtiari, at a distance of 180 km from the State Capital of Shahrekord, in

southwest Iran.

It is the highest dam of Iran (230 m from foundation) and has been impounded

since March 2010.

Karun 4 dam technical specifications

Location and details of the Karun 4 dam in Iran

Study area and dam specifications

Grout Curtain

To seal the dam foundation and abutments, a very large grout curtain was

designed and constructed.

The construction was done through the excavation of 5 series of galleries in

both left and right abutments at different elevations.

From inside these galleries the grouting boreholes are drilled and injected, to

have an integrated virtually wall or barrier, called grout curtain against water

leakage.

Based on the obtained results from the exploratory boreholes, the grout

curtain in two lines was designed and constructed, to sew/stitch the dam

structure to the Pabdeh impermeable formation in the upstream.

Selected Exploratory- , line 1 and line 2 check holes in the

grouting galleries

3D view of Karun 4 dam body and grouting galleries

Methodology

Water pressure test (WPT) or Lugeon test

Water pressure test, packer test or simply Lugeon test has been developed by

Professor Maurice Lugeon (1933).

A Lugeon unit is defined as one liter/minute of water absorption per meter of test

length of drill hole when the water in the borehole remains at a pressure of 10

bars or 1 MPa over a period of 10 minutes (Lugeon, 1933; Houlsby, 1990; Singh

and Goel, 1999).

Methodology

Take

The (grout) Take is defined as the rate of dry cement mass that is injected to

the test section, divided to the length of section (kg/m) (Deere 1982).

Methodology

Ewert Method

Ewert (1985) proposed a

qualitative method to

interpret the relationship

between permeability and

groutability in the dam

foundations. He classified

the obtained results from

different dam sites and

tests in to following

grouping:

Methodology

Ewert Method

Group A: large amount of Lugeon value and low grout Take indicates that water

can pass through the numerous fine fissures of the rock, but the corresponding

grout is not permitted.

Group B: Approximately proportionality between water and Take justifies well

the necessity of grouting.

Group C: The small water pass versus large Take cause to the hydraulic

fracture in the rock mass and shows that either the injection pressure is not

proper or at all unnecessary.

Group D: Low water and Take signs the sealing of area and no need no

treatment.

Results

Lugeon Permeability

Frequency distribution of Lugeon values in the different classes for

exploratory, line 1 and line 2 check holes for the left and right banks.

20 21

33

18

7

34

43

20

2 1

27

55

18

0 00

10

20

30

40

50

60

0 - 3 3 - 10 10 - 30 30 - 60 > 60

Fre

qu

en

cy %

Lugeon Values of Left Bank

Exploratory holes

Line 1 check holes

Line 2 check holes

34

41

24

16

7

56

34

9

10

48

38

10

5

00

10

20

30

40

50

60

0 - 3 3 - 10 10 - 30 30 - 60 > 60

Fre

qu

en

cy %

Lugeon Values of Right Bank

Exploratory holes

Line 1 check holes

Line 2 check holes

Results

Groutability

Frequency distribution of Take in the different classes for exploratory, line 1

and line 2 check holes for the left and right banks.

42

17

7 7 69

12

59

18

11

7

3 2 1

78

6

10

13

1 1

0

10

20

30

40

50

60

70

80

90

0 - 12.5 12.5 - 25 25 - 50 50 - 100 100 - 200 200 - 400 > 400

Fre

qu

en

cy %

Take Values of Left Bank

Exploratory holes

Line 1 check holes

Line 2 check holes48

14

57 7

108

56

1311 12

42 2

81

7

2 2 2 2 2

0

10

20

30

40

50

60

70

80

90

0 - 12.5 12.5 - 25 25 - 50 50 - 100 100 - 200 200 - 400 > 400

Fre

qu

en

cy %

Take Values of Right Bank

Exploratory holes

Line 1 check holes

Line 2 check holes

Results

Correlation of Lu- permeability and Take- groutability based on Ewert’s method

Lugeon versus Take with the four Ewert’s groupings for the exploratory holes

Results

Correlation of Lu- permeability and Take- groutability based on Ewert’s method

Lugeon versus Take with the four Ewert’s groupings for the line 1 check holes

Results

Correlation of Lu- permeability and Take- groutability based on Ewert’s method

Lugeon versus Take with the four Ewert’s groupings for the line 2 check holes

Results

Correlation of Lu- permeability and Take- groutability based on Ewert’s

method

Frequency distribution of Lu-Take pairs in the different groups for exploratory,

and line 1 and line 2 check holes for the left and right banks.

Conclusions

The grout curtain of Karun 4 dam is constructed on the dam foundation and

abutments to prevent, or minimize the water leakage from the dam reservoir

after impounding.

The measurements include Lugeon- and grout- Take values of exploratory-,

line 1 and line 2 check holes of the grout curtain.

Totally, data from 64 selected boreholes are used to study the relation

between Lugeon (Lu) permeability and groutability (Take) and, based on the

values of these two variables, classified into four groups, following Ewert’s

methodology.

The results indicate that the implemented grout curtains can seal leaking, as

Take is lower than 50 kg/m in more than 90% of the boreholes – the

requirement for efficient grout Take -, although there are still areas with

medium Lugeon values, i.e. data in Evert’s class A.

Conclusions

The Lu- values indicate that the permeabilities of the right bank are generally

lower than those of the left bank. This can be explained by the geological

characteristics underneath the dam of the Asmari formation (AS1) subunits.

Nevertheless there is still some scattering of Lu-Take pairs into Evert’s A-

group, which means that water leakage exists at these locations. The technical

solution would be to allow the extra water to seep through a drainage curtain.

Related and Ongoing studies

The seepage analysis through the drainage curtain is the topic of the presented

study of the authors as Poster in the Meeting:

Monitoring of the seepage controlling system of the Karun 4 dam in Iran

Furthermore, a numerical groundwater flow model is needed, to get a more

comprehensive and quantitative picture of the water flow seepage through the

dam foundation and abutments, which is the ongoing study of the authors

An example of the

groundwater flow

model results

Code:

CFP for Modflow 2005

GUI:

Molde Muse USGS

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Thanks for your attention!

S. Mohammad Hosseiny sohi

Ph.D. Candidate in Civil Engineering

mim.sohi@gmail.com

Department of Geo-hydraulics and Hydrology Engineering

Faculty of Civil- and Environmental Engineering

University of Kassel

Kurt-Wolters-Straße 3

34125 Kassel,

Germany

Contact