NUMERICAL MODELING OF SEEPAGE IN KOYUNBABA DAM

A Thesis

Present to

The Graduate Faculty of The University of Akron

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

Selim Emre Ozbek

December 2017 NUMERICAL MODELING OF SEEPAGE IN KOYUNBABA DAM

Selim Emre Ozbek

Thesis

Approved: Accepted:

Advisor Department Chair Dr. Zhe Luo Dr. Wieslaw K. Binienda

Committee Member Dean of College Dr. Junliang Tao Dr. Donald P. Visco

Committee Member Interim Dean of the Graduate School Dr. Ernian Pan Dr. Chad Midha

Date

ii ABSTRACT

Dams are very critical structures that are used mainly for energy production, agricultural irrigation, water storage. Seepage problems are seen in dams may require long-term and costly remediation programs by reducing the benefits of projects built for purposes such as drinking, irrigation, and energy. A widespread and potentially dangerous phenomenon related to flooding is seepage under dams, and the formation of sand boils.

In this study, Koyunbaba dam located within the boundaries of Ankara/Kalecik county is examined. The study aims to calculate the amount of leakage of the alluvium lateral on the dam foundation and to calculate the optimum location, thickness, depth, and permeability of the slurry trench that can be built under the dam foundation.

Groundwater Modeling System SEEP2D software which uses finite element method for calculations is used. The seepage results showed that the slurry trench significantly reduces the seepage. The thickness, depth, and permeability of the slurry trench have also been found to be essential factors in reducing leakage. It has been found that the slurry trench minimizes the leakage by up to 99%. Also, the factor of safety against piping which may occur in the downstream toe of the dam is examined. The coefficient of safety results showed that the base slurry trench should be extended to an impermeable layer or keyed the impermeable layer.

Keywords: slurry trench, Koyunbaba dam, concrete face rockfill dam, seepage.

iii ACKNOWLEDGEMENTS

I would like to express my most profound gratitude and thanks to my academic advisor, Dr. Zhe Luo for his unconditional support and valuable contributions during my graduate studies. I have gained the experience and knowledge while I was studying under his guidance, and I am grateful for his patience, inspiration and continuous support at all the time in my research. Also, I am grateful my previous advisor Dr.

Robert Liang for his valuable contributions

I am also very thankful to my committee members Dr. Junliang Tao and Dr.

Ernian Pan for their valuable suggestions and contributions.

I am very grateful to General Directorate of State Hydraulic Works (Turkey) for their financial and moral support during my graduate studies.

Special thanks to my colleagues; Dima A. Husein, Yixiang Li, Aashis Karki, and Ariful Hasan for their help and contributions. Also, I am thankful to my roommate

Erhan Kirencigil and my friend Oguzhan Kilic for their motivation support.

I want to extend my gratitude to my family for their endless support throughout my life.

iv TABLE OF CONTENTS

Page

LIST OF TABLES ...... ix

LIST OF FIGURES ...... x

CHAPTER

I. INTRODUCTION ...... 1

1.1 Definition Cutoff Wall and Types ...... 1

1.1.1 Soil-Bentonite Cutoff Walls (SB ...... 2

1.1.2 Soil-Cement-Bentonite Cutoff Walls (SCB ...... 2

1.1.3 Concrete-Bentonite Cutoff Walls (CB ...... 2

1.1.4 Geomembrane Cutoff Walls ...... 3

1.1.5 Deep Soil Mixing (DSM) Cutoff Walls ...... 3

1.2 Failure of Earth-fill Dams ...... 3

1.2.1 Hydraulic Failure ...... 3

1.2.2 Seepage Failure ...... 5

1.2.3 Structural Failure ...... 6

1.2.4 Earthquake Effect...... 7

II. LITERATURE REVIEW ...... 8

2.1 Introduction ...... 8

2.2 Historical Studies of Slurry Cutoff Wall ...... 8

2.3 Current Studies of Slurry Cutoff Wall ...... 10

v 2.4 Demolish Dam Due to Seepage and Piping Failure ...... 12

2.5 Concrete Face Rock-Fill Dam ...... 15

III. CASE STUDY ...... 19

3.1 Introduction ...... 19

3.2 Location ...... 19

3.3 General View of Koyunbaba Dam ...... 21

3.4 General Geology ...... 22

3.5 Hydrogeology ...... 23

3.6 Permeability of Dam Site ...... 23

3.7 Construction Reasons of Slurry Trench Wall ...... 24

3.8 Why Slurry Trench Wall Was Chosen...... 25

3.9 Cost of Slurry Trench Construction ...... 26

3.10 Model Development...... 27

3.11 2D Mesh Module ...... 28

3.12 SEEP2D Module ...... 28

3.12.1 Finite Element Method ...... 30

3.12.2 Van Genuchten Parameters ...... 31

3.13 Mesh Convergence...... 32

3.14 Model Building ...... 33

3.15 Slurry Wall Construction Features...... 44

3.16 Materials and Quantities Used in the Manufacture of Slurry Trench Wall ..47

3.17 Control Tests of Slurry Trench Cutoff Wall ...... 48

3.18 Materials Permeability Properties ...... 49

3.19 Plane Stress and Plane Strain ...... 49

3.19.1 Plane Stress ...... 50

vi 3.19.2 Plane Strain ...... 50

3.20 Results ...... 51

3.21 Measured Seepage Rate with Different Conditions ...... 51

3.21.1 Koyunbaba Dam Geometry and Features with/without Place of Slurry Trench Wall Condition ...... 52

3.21.1.1 Without Slurry Trench Condition ...... 52

3.21.1.2 Slurry Trench Under the Upstream of Embankment Condition ...... 53

3.21.1.3 Slurry Trench Under the Middle of Embankment Condition ...... 54

3.21.1.4 Slurry Trench Under the Downstream of Embankment Condition ...... 55

3.21.1.5 Profile of Slurry Trench with Guide Walls ...... 56

3.21.2 Seepage Rate Results for Different Places of Slurry Trench ...... 57

3.21.3 Seepage Rate Results for Lateral Distance from Embankment ...... 58

3.21.4 Seepage Rate Results for Different Thickness of Slurry Trench ...... 60

3.21.5 Seepage Rate Results for Different Keyed Depth of Slurry Trench ....60

3.21.6 Seepage Rate Results for Different Slurry Trench Permeability Rate ...... 62

3.22 In the Case of Two Slurry Trenches ...... 62

3.22.1 Seepage Rate Results for Upstream of Embankment and Middle of Embankment Condition...... 63

3.22.2 Seepage Rate Results for Upstream of Embankment and Downstream of Embankment Condition...... 64

3.23 Factor of Safety for Vertical Piping ...... 65

3.23.1 Factor of Safety for Different Places of Slurry Trench ...... 67

3.23.2 Factor of Safety for Lateral Distance from Embankment ...... 67

3.23.3 Factor of Safety for Different Thickness of Slurry Trench ...... 69

3.23.4 Factor of Safety for Different Keyed Depth of Slurry Trench ...... 70

vii 3.23.5 Factor of Safety for Different Slurry Trench Permeability Rate ...... 71

3.24 In Case of Two Slurry Trenches ...... 72

3.24.1 Factor of Safety for Upstream of Embankment and Middle of Embankment Condition...... 72

3.24.2 Factor of Safety for Upstream of Embankment and Downstream of Embankment Condition ...... 73

IV. CONCLUSIONS...... 75

4.1 Conclusion ...... 75

4.2 Recommendations ...... 76

REFERENCES ...... 77

APPENDIX ...... 81

viii LIST OF TABLES

Table Page

2.1 Some dam failure examples due to seepage and piping………………………….15

2.2 Some of concrete face rockfill dam leakage rates………………………………..17

3.1 Comparison between alluvium injection and slurry trench application on Aslantas Dam…………………………………………………………26

3.2 Costs of slurry trench wall construction at Koyunbaba Dam…………………….27

3.3 Use of van Genuchten values in other numerical programs……………………...31

3.4 van Genuchten parameters α and n………………………………………………32

3.5 Construction values of slurry trench……………………………………………..44

3.6 Slurry trench mixture ratios………………………………………………………47

3.7 Slurry trench laboratory test results……………………………………..………..48

3.8 Hydraulic conductivity values assigned to layer soils, Koyunbaba Dam………..49

ix LIST OF FIGURES

Figure Page

1.1 Dam failure by overtopping…………………………………………………….…4

1.2 Failure of the dam due to piping through dam body………………………………5

1.3 Failure of the dam foundation due to piping through dam foundation……………6

2.1 Failure rates for cement dam type………………………………………………..13

2.2 Failure rates for earth-fill dam type………………………………………………13

2.3 Failure rate for all types of dam………………………………………………….14

2.4 Typical rockfill dam section……………………………………………………...16

3.1 Koyunbaba Dam’s location………………………………………………………20

3.2 Koyunbaba Dam’s seen from the upstream of embankment…………………….21

3.3 Koyunbaba Dam’s seen from the downstream of embankment………………….21

3.4 Koyunbaba Dam’s seen from overview………………………………………….22

3.5 2D projection mesh sample…………………………………………………….. .28

3.6 Relationship between seepage rate and interval of mesh………………………...33

3.7 Project wizard…………………………………………………………………....34

3.8 Opening view of the software……………………………………………………35

3.9 Display of units…………………………………………………………………..35

3.10 Defining coordinates and model design………………………………………...36

3.11 Creating corner points with attribute table……………………………………...37

3.12 Creating arcs with use nodes…………………………………………………....37

3.13 Background colored a gray after build polygons………………………………..38

x 3.14 Defining material properties……………………………………………………38

3.15 Determining the different material assignments………………………………..39

3.16 Defining boundary conditions part of left-side of dam…………………………40

3.17 Defining boundary conditions part of right-side of dam………………………..40

3.18 Building density of mesh size…………………………………………………...41

3.19 Equally-interspace vertices……………………………………………………...41

3.20 Creating 2D mesh……………………………………………………………….42

3.21 SEEP2D boundary conditions…………………………………………………..42

3.22 Analysis option wizard………………………………………………………….43

3.23 Starting finite element method calculation……………………………………...43

3.24 Koyunbaba dam section view without slurry trench condition…………………52

3.25 Koyunbaba dam section view with slurry trench under the

upstream of embankment condition……………………………………………..53

3.26 Koyunbaba dam section view with slurry trench under the

middle of embankment condition……………………………………………….54

3.27 Koyunbaba dam section view with slurry trench under the

downstream of embankment condition………………………………………….55

3.28 Slurry trench profile applied in Koyunbaba dam………………………………..56

3.29 Relationship between seepage rate and different place of slurry trench………...57

3.30 Relationship between seepage rate and 90 meters lateral distance from upstream of embankment…………………………………………………...58

3.31 Relationship between seepage rate and 120 meters lateral distance from upstream of embankment………………………………………………...... 59

3.32 Relationship between seepage rate and 150 meters lateral distance from upstream of embankment…………………………………………………...59

3.33 Relationship between seepage rate and thickness of slurry trench……………...60

xi 3.34 Relationship between seepage rate and keyed depth of slurry trench…………..61

3.35 Relationship between seepage rates and keyed depth of slurry trench………….61

3.36 Relationship between seepage rates and slurry trench permeability……………62

3.37 Two slurry trenches in the alluvium foundation. Place of upstream of embankment and middle of embankment……………………………………..63

3.38 Relationship between seepage rates and slurry trench thickness with two slurry trench condition………………………………………………..63

3.39 Two slurry trenches in the alluvium foundation. Place of upstream of embankment and downstream of embankment…………………………………..64

3.40 Relationship between seepage rates and slurry trench thickness with two slurry trench condition………………………………………………..64

3.41 Reference area for calculation of the factor of safety…………………………...66

3.42 Relationship between factor of safety and different place of slurry trench……………………………………………………………………..67

3.43 Relationship between factor of safety and 90 meters lateral distance from upstream of embankment………………………………………...68

3.44 Relationship between factor of safety and 120 meters lateral distance from upstream of embankment………………………………………...68

3.45 Relationship between factor of safety and 150 meters lateral distance from upstream of embankment………………………………………...69

3.46 Relationship between factor of safety and thickness of slurry trench……………………………………………………………………..70

3.47 Relationship between seepage rate and keyed depth of slurry trench……………………………………………………………………..71

3.48 Relationship between factor of safety and permeability of slurry trench……………………………………………………………………..72

3.49 Relationship between factor of safety and thickness of slurry trench with two slurry trench condition……………………………………...... 73

3.50 Relationship between factor of safety and slurry trench thickness with two slurry trench condition…………………………………………………74

A.1 Relationship between water flow lines with non-slurry trench………………….81

xii A.2 Relationship between water flow lines with slurry trench under the downstream of the embankment…….………………………………………82

A.3 Relationship between water flow lines with slurry trench under the middle of the embankment……………………………………………….….83

A.4 Relationship between water flow lines with slurry trench under the upstream of the embankment……...... 84

A.5 Relationship between water flow lines with slurry trench. The base of slurry trench is at 3 meters above the boundary of the impermeable layer with alluvium layer…………………………………………………….….85

A.6 Relationship between water flow lines with slurry trench. The base of the slurry trench is at the boundary of the impermeable layer with alluvium layer.…………………………………………………………………..86

A.7 Relationship between water flow lines with slurry trench. The slurry trench is keyed 3 meters depth of the impermeable layer...... 87

A.8 Relationship between water flow lines with slurry trench under the upstream of the embankment and middle of the embankment. The slurry trench is keyed 3 meters depth of the impermeable layer…………………….....88

A.9 Relationship between water flow lines with slurry trench under the upstream of the embankment and downstream of the embankment. The slurry trench is keyed 3 meters depth of the impermeable layer………………..89

xiii CHAPTER I INTRODUCTION

1.1 Definition of Cutoff Wall and Types

The slurry cutoff wall is an efficient way for seepage controlling through a dam foundation. The slurry wall is structural foundation instrument constructed underground for controlling slurry fluid, including bentonite, pulverized clays and concrete mixed with water, for supporting the field walls of an excavation and later backfilled which may be increase enhanced with a steel cage, precast panel or steel beams. Each side of the wall alignment to supply horizontal and vertical alignment control for the excavation and reinforced elements to be inserted in the excavated unit.

The slurry trench is constructed in the separate unit, the name ‘panels’ that are attended at their ends formed by keyed joints from an extracted end stop shape. Steel beams are usually used as connectors or fittings between panels. Panel dimensions typically range between 60 cm and 150 cm in width and between 210 cm and 75 m length [1].

There are many kinds of cutoff walls used for preventing seepage under embankment dams, ponds, or levees. These types were chosen based on client or designer will or settlement conditions. According to material types and construction types, there are five specific categories and one general category [2]:

A. Soil-bentonite cutoff walls (SB)

1 B. Soil-cement-bentonite cutoff walls (SCB)

C. Concrete-bentonite cutoff walls (CB)

D. Geomembrane cutoff walls

E. Deep soil mixing (DSM) cutoff walls

F. Others: Includes secant pile, jet grouted, and sheet pile cutoff walls

1.1.1 Soil-Bentonite Cutoff Walls (SB)

This type cutoff wall also called an earth-backfilled cutoff wall. ICOLD (1985) indicated that slurry trench thickness should be between 150 cm to 300 cm [3]. Along with the development of technology, cutoff wall construction excavated typically 30cm to 150cm width [2]. The excavation is accepted through the materials requiring a cutoff to a comparatively impervious underlying layer and keyed into that layer a minimum of 90cm to 150cm if a specific cutoff wall is needed [2].

1.1.2 Soil-Cement-Bentonite Cutoff Walls (SCB)

In recent years, these type cutoff walls have been used in with increasing frequency, and soil cement-bentonite wall is the unique variety of both the cement- bentonite and soil-bentonite cutoff walls.

Soil cement-bentonite cutoff wall is designed and controlled by the amount of soil, bentonite and cement content. This mixture content creates different properties than standard cement-bentonite and soil-bentonite cutoff wall. The permeability of soil cement-bentonite material will be slightly higher than soil-bentonite backfill because of using Portland cement and Portland cement preventative effect [2].

1.1.3 Concrete Bentonite Cutoff Walls (CB)

The cement-bentonite cutoff wall is applied typically 60cm to 90cm wide [2].

Unlike the soil-bentonite cutoff wall, after excavation to create a relative erosion-

2 resistant and impermeable barrier when solidified, the stabilizing fluid used throughout excavation is a cement bentonite-water mixture which remains in place. Separate operation and necessary space do not require for this methodology [2].

1.1.4 Geomembrane Cutoff Walls

This method is not commonly used in embankments but used as a seepage cutoff wall for contaminated groundwater collection. Due to installation difficulties and joints, geomembrane cutoff walls may not provide as much assurance in the uniformity and efficiency of the constructed [2]. On the other hand, appropriate geomembrane wall type, carefully planning, and construction methodology can significantly mitigate [4].

1.1.5 Deep Soil Mixing (DSM) Cutoff Walls

Deep soil mixing is a soil treatment methodology that soil is blended and mixed with cementitious or/and other factors to treat soils in situ to compose seepage barrier wall or foundation component, or improve strength and reduce compressibility [2].

1.2 Failure of Earth-Fill Dam

Faulty design, improper construction, poor maintenance practices, and poor-quality materials using may cause fail for engineering structures like earth dams. This failure can be gathered under the three main headings. These are the hydraulic failure, seepage failure, structural failure, and an earthquake [5].

1.2.1 Hydraulic Failure

The erosion activity of water on the embankment slopes because of hydraulic failures from the uncontrolled flow of water over and next to the dam. Dams are not designed to be overtopped, and for this reason, they are especially sensitive to erosion

[5].

3

Figure 1.1: Dam failure by overtopping (Source: theconstructer.org).

i) By overtopping: The flood water will pass over the dam and wash it downstream when the capacity of spillway or freeboard of the dam is inadequate [5].

ii) Downstream toe erosion: Heavy cross-current from spillway buckets or tailwater because of the barrier at the downstream side may be eroded. It will lead to failure of the dam when the toe of downstream is eroded. To provide a downstream slope pitching or a riprap up to a high above the tailwater depth is preventing this condition. Also, the side wall of spillway should have adequate length and height to avoid the probability of cross-flow towards the earth dam [5].

iii) Upstream surface erosion: Because of the winds, the waves improved near the top water surface may cut into the soil of upstream dam face that may cause the slip of the upstream surface leading to failure. For preventing failure, the upstream face should be protected with stone pitching or riprap [5].

iv) Downstream face erosion by gully formation: During heavy precipitation, runoff on the downstream surface can damage the surface, which can create flood deposits that can cause failure. For preventing these shortcomings, the dam surface should be appropriately maintained; all cuts filled with time and surface well grassed.

Suitable heights and surface well drained can be provided by berms [5].

4

1.2.2 Seepage Failure

Seepage usually occurs in the dams. It may not affect the stability of the dam if the magnitude is within design limits. But, it will cause the failure of the dam if seepage is uncontrolled or concentrated beyond limits. Various type of seepage is below [5].

i)Piping through dam body: Small channels are formed that transport material downstream when leakage starts during poor soils in the shape of the dam. As more materials are carried downstream, the channel glow more significant and more significant that can cause the barrier to be washed [5].

Figure 1.2: Failure of the dam due to piping through dam body (Source:

theconstructer.org).

ii) Piping through foundation: It may cause massive seepage when fissures or coarse sand or cavities or strata of gravel are present in the dam foundation. The concentrated leakage at the high ratio will erode soil that causes increased soil and flow of water. Consequently, the dam will sink or settle leading to failure [5].

5

Figure 1.3: Failure of the dam foundation due to piping through dam foundation

(Source: theconstructer.org). iii) Sloughing of the downstream side of dam: When the downstream toe of the dam becomes saturated and starts receiving eroded, the procedure of failure due to sloughing starts, causing a slide or small slump of the barrier. The little slide leaves a relatively vertical face, that also becomes saturated because of forms and seepage and slumps more unstable surface. If the process of saturation and slumping continues, cause failure of the dam [5].

1.2.3 Structural Failure

Due to shear failure causing slide along the slopes is mainly the structural failure.

i) Slide in embankment: The embankment may slide causing failure when the slopes of the dam are too perpendicular. This condition may be happening when there is a sudden drawdown, that is critical for the upstream side due to the development of extremely high pore pressures, that decreases the shearing strength of the soil [5].

6

ii) Foundation slide: The whole dam may slide because of water thrust when the foundation of an earth-fill barrier is composed of clay, fine silt, or similar type of soil.

The side thrust of the water stress may shear the whole dam and cause its failure if seams of fissured rock like soft clay, or shale exist below the foundation [5].

iii) Poor maintenance and faulty construction: If the compaction of the embankment is not adequately done during installation, it may cause failure [5].

1.2.4 Earthquake Effect

Cracks may happen on the core wall, and these cause leakages and piping failure. Slow waves due to the earthquake, shaking the reservoir water may cause overtopping. Sliding natural hills may cause damage to the dam. Foundation layer may liquefy [5].

7

CHAPTER II

LITERATURE REVIEW

2.1 Introduction

Slurry-supported trenches that construction of subsurface structures is used groundwater cutoff walls and diaphragm walls. Exhaustive reviews of wall geometry, construction methodology, slurry design, performance, permanence, and other proper topics can be found in Nash (1974), D’Appolonia (1980), Hajnal et al. (1984), Paul et al. (1992), Evans (1993), and Xanthakos (1994) [6,7,8,9,10,11]. The use of slurry cutoff walls has become important in recent years. Mainly, prevention of leakage in dam’s foundation is used to prevent dam destruction and to prevent pollution from shifting to clean water sources.

2.2 Historical Studies of Slurry Cutoff Wall

Slurry trench construction comes from over 60 years ago in Italy and the United

States. Almost 30 years after, this technique is used throughout the world to provide kinds of engineering needs [4].

After the use of slurries and muds in oil well drilling operations, slurry trench construction was developed. The first use of slurry trenches the early 1900’s for clay mud suspension in the drilling wells [12]. Thixotropy and experimentation with additives to control the viscosity of drilling muds are related researchers of slurry features after next 20 to 30 years [13]. Bentonite clays were used firstly in 1929 for

8 used in drilling operations to make stabilization deep wells in unconsolidated materials and to bring cutting to the surface [12].

The concept of a continuous diaphragm wall constructed in a slurry-supported trench was developed in the late 1930’s, Veder, Italy [4]. Already in use, two combination system that is the mud-filled borehole, and the continuous bored-pile wall were evolved for this concept [13].

In the late 1940’s, the U.S. Corps and Engineers were used slurry trench construction. They constructed a slurry trench backfilled with plastic material to prevent saltwater intrusion into a freshwater zone at Terminal Island in California [12].

Furthermore, they built slurry trench cutoff wall for control of under seepage and piping under Mississippi River levees [4].

In 1950’s, slurry trench technique marked a period continual improved and developed. These activities were accompanied by laboratory investigations of bentonite support properties during excavations [13]. At dams in Italy, concrete diaphragm walls were installed for controlling vertical support loads and seepage flow at the beginning of 1950’s [4]. In the U.S., a soil backfilled cutoff wall was constructed under the

Wanapum Dam in 1959, and this technique was symbolized the first use in the U.S. for controlling seepage at a significant dam [14,15].

In 1960’s, as an alternative to traditional foundation technique, slurry trench cutoff walls had become a founded method for use in earth dam structure. The development of a self-hardening slurry was occurred by a significant improvement in the construction of slurry trench cutoff wall. This slurry consists of water, bentonite, and cement [4].

9

2.3 Current Studies of Slurry Cutoff Wall

Along with the progress of the technology, the evaluation of the cutoff wall was started by various software. These improvements not only save time but also play an essential role in the assessment of cutoff wall. Some researchers investigated how cutoff wall effect to reduce seepage rate such as Shahbazian Ahari et al. (2000), Freeze (1971),

Ijam (1994), Garg et al. (2002), Moharrami et al. (2015), Novak et al. (2007)

[16,17,18,19,20]. Also, some researchers such as Ijam (1994), Al-Musawi (2006), Al-

Senousi and Mohammed (2008), Garg et al. (2002), and Al-Saadi et al. (2011) were studied how inclined cutoff wall effect to seepage rate [21,22,23,24,25].

Branch and Hossain (2007) studied how slurry trench keyed depth effect to the seepage rate and how related factor of safety with keyed depth [26]. For this purpose, they used SEEP/W software and determined seepage analyses of soil-bentonite cutoff wall that part of the Dallas Floodway Extension project.

Zoorasna et al. (2008) were studied Karkheh storage dam in Iran [27]. They investigated how seepage and stress-strain were affected different connection systems on the maximum gradient condition and stress concentration condition in connecting zone. They researched six different connection systems and evaluated maximum hydraulic gradients effects for each system.

The most seepage modeling of embankment dams assesses two dimensions, especially the highest section dams. Soleimanbeigi and Jafarzadeh (2005) were researched differences between 2D and 3D numerical analysis [28]. The steady-state results are compared with two-dimensional analysis and three-dimensional modeling of embankment dams with SEEP3D software version 1 from the Geo-Slope. The three-

10 dimensional hydraulic gradient indicates more considerable amount compared to the gradient acquired from the traditional two-dimensional analysis.

Mansuri and Salmasi (2013) were investigated the effectiveness of using horizontal drain and cutoff wall in reducing seepage flow on heterogeneous earth dam

[29]. For this purpose, they researched various horizontal drain lengths and cutoff wall depth under the earth dam in the different location of the foundation. Seep/w software was used numerical simulation for computing seepage analysis, hydraulic gradient, and uplift pressure. Optimum position is middle of dam foundation for reducing seepage rate and piping. Also, seepage rate is decreased while increasing cutoff wall depth.

Different cutoff wall location has little effect for exit hydraulic gradient.

Zakanyi and Szucs (2013) were studied hydrodynamic modeling of flood control dams [30]. For solving different case study problems, the SEEP2D module was used successfully. The analysis aimed to establish the quantity of seepage through flood control dams with different characters. The results of the study showed that SEEP2D could provide useful assistance significantly differ from the Casagrande and the

Casagrande-Kozeny methods. GMS-6 software calculates very close the reality with the Pavlovszkij method of the calculation in the case of the Lazberc reservoir. Besides,

GMS 6.0 provide most useful data because the software is the help to variation in the internal structure of dams can be characterized.

Miroslaw-Swiates et al. (2013) researched the effectiveness of cutoff wall with two-dimensional numerical model [31]. In the steady-state condition, water flow through the body and the base of the levee was assessed by numerical calculations. Cut of walls constructed in DSM (deep-mixed soil columns) and WIPS (vibration-grouting slit diaphragms) technology and numerical model used for filtration through a levee.

11

Using different techniques for settle cutoff wall in the same location, giving similar results for the position of the groundwater table and reducing the hydraulic gradient and the outflow on the downstream side. The cutoff walls located in the center of the levee are less efficient than the ones located near situated upstream and interacting with impermeable geomembrane proved to be.

Hassan (2015) was researched optimal value of inclination angle and cutoff location for a hydraulic structure [32]. SEEP2D modeling was used for more than 3500 different cases for analyzing and modeling. The results showed that excellent location of the cutoff wall is at upstream with an inclination angle from 59o to 68o for equal depth or more than 0.4.

2.4 Demolish Dam Due to Seepage and Piping Failure

Dams may fail due to some criteria such as piping, overtopping, and seepage the foundation under the barrier, etc. In this part, seepage failure and piping are discussed. Piping and leakage may cause to fail in natural dams because they may have high porosities and they have not undergone systematic compaction [33]. These failures are variable according to dam type. For instance, failure rates vary between cement dams and earth-fill dams. According to dam failure results, seepage effect to piping and they caused dam failure. Graphs show that seepage and piping failure mostly happened earth-fill type dams.

12 Overtopping

Foundation

Failure Piping and Seepage

Concrete Dam Type Type Dam Concrete Others

0 5 10152025303540455055 Percentage (%)

Figure 2.1: Failure rates for cement dam type (Source: Department of Conservation

and Recreation) [34].

Overtopping

Foundation

Failure Piping and Seepage

Earthfill Dam Type Type Dam Earthfill Others

0 5 10 15 20 25 30 35 40 Percentage (%)

Figure 2.2: Failure rates for earth-fill dam type (Source: Department of Conservation

and Recreation) [34].

13 Overtopping

Foundation

Piping and Seepage

Others All Dam Type Failure Type DamAll

0 5 10 15 20 25 30 35 Percentage (%)

Figure 2.3: Failure rate for all types of dam (Source: Department of Conservation and

Recreation) [34].

14

Table 2.1: Some dam failure examples due to seepage and piping (Source: Dr. Charles

L. Bartholomew, www.damsafety.org) [35].

Name of Dam Location Year of Failure Cause of Failure Puentes (masonry) Spain 1802 Seepage under dam Ashley Dam USA 1909 Piping during first filling Bayless Dam USA 1911 Seepage under dam City Reservoir USA 1912 Seepage West Brook USA 1916 Seepage-Shallow Reservoir Cutoff Lake Toxaway USA 1916 Piping Failure Eigiau UK 1925 Seepage Under Dam Alla Sella Zerbino Italy 1935 Foundation Seepage, Sliding and Overtopping Baldwin Hills USA 1963 Piping Failure Fontonella Dam USA 1965 Seepage and Piping Sid White Dam USA 1971 Seepage through animal burrows Lake O’Hills USA 1972 Piping Failure Teton Dam USA 1976 Seepage and Piping Myron Isabel Dam USA 1978 Piping-tree roots, animal burrows

2.5 Concrete Face Rockfill Dam

Concrete face rockfill dams have been built increasingly around fifty years.

Concrete faced rock-fill dams, CFRD, is the term used to describe a type of barrier that has a dam body of rock-fill or gravel materials that is compacted and an anti-seepage system using a concrete face slab on upstream [36]. The concrete slab works like an impervious layer when the rock-fill body includes granular material which has a high permeability and supports the concrete face slab by giving the dam stability [37]. It is shown typical sections of a rockfill dam in below.

15

Figure 2.4: Typical rockfill dam section (Source: Department of the Interior Bureau of

Reclamation, Design Standard No:13, Chapter 2) [38].

One of the significant specifications with the CFRD is that the dam type lets us use local material from the riverbed and the obligatory excavations in the rock-fill dam body, in contrary to using expensive material from quarries which may have to be transported far from the construction area. On the other hand, there are some quality requirements on the aggregates must be met to be used in the dam body. Here are some concrete face rockfill dam examples from some countries (Table 2.2).

16 Table 2.2: Some of concrete face rockfill dam leakage rates (Source: G Hunter 2003)

[39, 40, 41].

Modern CRFD Applications Name of Dam Height Water First Filling During Operation (m) Depth Max Water Max Water Long at Max Leakage Depth Leakage Depth Term Water Rate (m) Rate (m) Rate Level (l/sec) (l/sec) (l/s) (m) Aguamilpa 185.5 182.5 260 169.5 150-200 165- 50- 175 100 Alto Anchicaya 140 135 >1800 125 450 135 130 Bastyan 75 70 10 70 10-25 70 5 Brogo 43 28.5 42.5 28.5 5-10 30 4-5 Cethana 110 101 60-70 Appr 20-80 96 5-10 x 80 Chengbing 74.6 69.5 75 unkn 60 63.5 20 own Crotty 83 75 45-50 67 50-70 70-75 30- 35 Foz Do Areia 160 155 236 150.5 unknow unkn 60 n own Golillas 125 122.5 1080 115 600-700 115 270- 500 Guanmenshan 58.5 57 10 57 unknow unkn 5-6 n own Ita 125 119.5 unknow unkn 1700 unkn 380 n own own Kangaroo Creek 60 48 unknow unkn 11 unkn 2.5 n own own Kotmale 90 85.6 10-40 40-80 30-50 85 10- 20 Little Para 53 50.5 16 43 18 50.5 3-5 Mackintosh 75 73 25 62 20-25 68 8-10 Mangrove Creek 80 74 unknow unkn 5.6 67.5 2.5 n own Muchison 94 85 5-10 70 10 73 2 Salvajina 148 141 unknow unkn 74 130 Unk n own now n Scotts Peak 43 39.5 100 37 6-10 39 2-3 Segredo 145 141 390 141 unknow unkn 45 n own Shiroro 125 112.5 1600 105 unknow unkn 100 n own Tianshengqiao-1 178 167 132 154.5 N/A N/A N/A

17 Tullabardine 25 23 unknow unkn 3-6 22-23 1-2 n own White Spur 43 41 7 38 12 30 2 Winneke 85 82 60 81 25-30 unkn 15 own Xingo 140 137 160 133 200 137 140 Early CRFD (1029’s-1960’s) Applications Cogswell 85.5 unknow 3510 63.5 unknow unkn Unk n n own now n Courtright 96.5 94 unknow unkn 1275 94 Unk n own now n Dix River 84 76 unknow unkn 2700 unkn 2000 n own own Lower Bear 75 71.5 110 71.5 85 71.5 25- No.1 40 Salt Springs 100 97.5 850 unkn 425-565 97.5 Unk own now n Strawberry 43.5 unknow unknow unkn 285 unkn 170 n n own own Wishon 90 89 3120 89 unknow unkn 850 n own

18 CHAPTER III CASE STUDY

3.1 Introduction

It is not possible to carry out agricultural irrigation using underground water in the project area. For this reason, a dam was built for agricultural irrigation in the region.

The length of the dam is KM0+434.26 meters, and width of the barrier is 271 meters

[42]. Koyunbaba dam construction was started on December 3rd, 2011 and planned to completion on 2019 (16). Slurry trench construction was launched on April 1st, 2016 and was finished on June 29th, 2016. In this study, the soil-cement-bentonite slurry trench was applied. The slurry trench was constructed as 1-meter thickness, 4*10-9 m/s permeability rate, and 3 meters keyed depth [42].

3.2 Location

The Koyunbaba dam and the lake area are located on the Terme river, within the boundaries of Ankara/Kalecik county. As the crow flies, 60 km north-east of

Ankara, 27 km north of Kalecik and 25 km north-east of Cubuk [42]. Project site location map is given below (Figure 3.1).

19 Figure 3.1: Koyunbaba Dam’s location (Source: DSI).

20 3.3 General View of Koyunbaba Dam

Figure 3.2: Koyunbaba Dam’s seen from upstream of the embankment (Source from

DSI).

Figure 3.3: Koyunbaba Dam’s seen from downstream of the embankment (Source

from DSI).

21

Figure 3.4: Koyunbaba Dam’s seen from overview (Source from DSI).

3.4 General Geology

In the project area located between the North Anatolian fault and Kirsehir massif, there are autochthons of Cretaceous and Tertiary sediments and magmatic rock units and covering materials such as old alluvion, alluvium, accumulation cone and slope rubble formed up to the present day from Quaternary [42].

The oldest form of the project area is the Eldivan Ophiolite complex of

Cretaceous-aged tectonically. Complex, Eldivan ophiolite complex is not separated, defined as Gabbro-Diabase, Split-Basalt-Diabase, Radiolarite member and Limestone block. Respectively on Ophiolites; The Kilic Group consisting of the Upper Cretaceous volcanic granular conglomerate, sandstone, mudstone, limestone and lava alternations with unconformity is composed of Kizilcukur Formation, Paleocene aged conglomerate and sandstone, Eocene-Lower Miocene aged Incik Formation, Oligocene-Middle

Miocene aged Eldivan Ophiolite Complex; The Kumartas Formation, consisting of conglomerate and sandstone, unconformably overlying the Hisarkoy Formation, Upper

22

Miocene aged Kumartas Formation and gradual transition of clayey limestone, marl, claystone, conglomerate, sandstone and tuffite alternations form Karakocas Formation,

Upper Miocene Hanicili Formation, and gradual transition gypsum, mudstone, sandstone, tuffite alternation formed Bozkir Formation, all the units which came as a

Golbasi Formation consisting of conglomerate, sandstone, and siltstone, which are unconformably overlain on the older formations of Pliocene age, are called ‘Gypsifer

Facies’ and ‘Terrestrial Separated Formations’ in previous studies [42].

3.5 Hydrogeology

The project area does not have the potential of underground water in the economical amount that can be irrigated by using underground water. Most of the formations exposed on the project site do not have groundwater carrying capability.

Kizilcukur Formation (Tki) consisting of Paleocene aged conglomerate and sandstone consists of Oligocene-Middle Miocene Golsel Limestone (Tit), Upper Miocene clayey limestone, Hanici Formation (Th) consisting of marl, claystone, conglomerate, sandstone and tuffite alternations and Pliocene aged, unconformably overlying older formations and the Golbasi Formation (Tg) consisting of loose conglomerates, sandstones and mudstones are partly water-bearing formation. These structures have few and very tiny water springs that vacated from the conglomerate and sandstone levels. Most of these sources are dry in the arid season. Also, the old and new alluvium are in the form of water-bearing formation [42].

3.6 Permeability of Dam Site

The dam body seated in the ophiolite complex. This complex forms the dominant group of serpentinites. The serpentinites are dissociated to a moderate degree, somewhat dissociated, fragile-very fragile, cracks filled with calcite and weak-very

23 weak according to the definition of drilling made for geotechnical purposes. The project area does not have the potential to be irrigated by using underground water [42].

According to the results of the test where the pressure water test in drilling wells, lugeon permeability values in the ophiolite complex forming the main rock were calculated at the planning stage, and it was determined that 70% of the bedrock was impermeable-less permeable and 30% permeable-very permeable property [42].

The drillings at the dam site and the underground water levels observed in these drills have been investigated, and it is thought that the underground water feeds the valley [42].

In the drilling works carried out on the axis of the dam, permeability value of the alluvium varies between K=10-1 m/s and K=10-5 m/s, and the average permeability

-2 is calculated as K=10 m/s (Ky/Kx=0.25) by evaluating the drilling data [42]. According to this evaluation, alluvium is semi-permeable and permeable, but it is noteworthy that the ratio of gravel-sand in drilling logs and soil assessments is high. For this reason, alluvium is described as porous.

3.7 Construction Reason of Slurry Trench Wall

Koyunbaba dam was built for irrigation purpose for farm place [42]. According to the information given in 3.3.1 and 3.3.2, water in the region is an important issue, and the loss of water in the dam is an important issue. With the project realized, it will be possible to irrigate the agricultural lands up to the Kizilirmak river on the right and left the coast of Acicay and Terme river. In line with this information, keeping water at reservoir field is essential for long-term use. For preventing seepage under the dam, slurry trench construction was made between reservoir cofferdam and impermeable basalt base.

24

In this study, the effect of the slurry trench modeling is evaluated by SEEP2D finite element program. Seepage assessed with slurry trench modeling, without slurry trench modeling, and different place of the slurry trench to find an optimum benefit of the slurry trench.

3.8 Why Slurry Trench Wall Was Chosen?

In the past, State Hydraulic Works (DSI), tried to remove alluvium layer under the dam area or applied alluvium injection construction because of preventing the leaks.

This method primarily removed whole alluvium layer is very expensive. Besides, alluvium injection application also expensive than slurry trench application. Also, alluvium injection takes more time than slurry trench application.

Regarding comparison, the Aslantas dam (in Osmaniye/Turkey) is a great example. Alluvial excavations for the dry foundation, this method is started by using alluvium injection and then by using the slurry-trench equipment. The injection was made under the axis of the cofferdam, and then the slurry trench was crossed, and the two systems were compared [43]. Below the table show that comparing alluvium injection and slurry trench application.

25 Table 3.1: Comparison between alluvium injection and slurry trench application on

Aslantas Dam (Karaogullarindan, T.,1983). [43]

Factors Alluvium Injection Slurry Trench Duration 80 days (7/4/1976- 55 days (9/10/1978- 9/22/1976) 11/3/1978 Length of 50.00 137.20 Injection/Wall (m) Area of Injection/Wall 450 2149.56 (m2) Deepest Place (m) 16.80 (Alluvium) 18.50 (Alluvium)

Average Depth (m) 13.00 15.00 Total Mixture Used 650 3665 (m3) Used Materials (for 1 m2) Cement (kg/m2) 590 460 Bentonite (kg/m2) 90 95 Mixture (m3/m2) 1.44 1.71 (Slurry) Granulated Sugar 0.70 (kg/m2) Progress Speed 5.62 39.09 (Including assembly (m2/day) and preparation) Obtained K=10-4 K=10-6 Impermeability (cm/s) Cost (1977) (TL/m2) 4,600 2509 (Approximately)

3.9 Cost of Slurry Trench Construction

The cost analysis of the slurry trench was estimated at project stage and was built later. Thus, the costs mentioned here are close to the actual slurry trench cost.

Prices based on three criteria. These are material transportations fee, materials fee, and guide walls fee of slurry trench [42]. These construction prices have been converted into US dollars from Turkish liras and currency converted rate come from Central Bank of Republic of Turkey (01/28/2008).

26

Table 3.2: Costs of slurry trench wall construction at Koyunbaba Dam (Source: DSI).

Cost Transportation Fees Cement (4108 ton) 90,622.48 TL Bentonite (642 ton) 12,128.25 TL Sand-Gravel (10599 ton) 32,750.91 TL Slurry Trench Guide Wall Iron 680.43 TL Materials Cement (4108 ton) 642,409.04 TL Bentonite (642 ton) 186,180 TL Iron for Slurry Trench Guide Wall 31,910.28 TL Others (Labor cost, electricity cost, 5,405,847.06 excavating cost, etc.) Total (Turkish Liras) 6,402,528.45 Total (US Dollars) 5,371,699.35

3.10 Model Development

Groundwater Modeling System was developed by the Brigham Young

University Environmental Modeling Research Laboratory in collaboration with the

Waterways Experiment Station. The interface of the software is developed by Aquaveo company, LLC in Provo, Utah. Groundwater Modeling System (GMS) was used for measuring seepage rate beneath the dam with the slurry trench [44]. The GMS is a whole graphical user situation for performing groundwater simulations. The entire

GMS system involves a graphical user interface (the GMS program) and the number of analysis codes (MODFLOW, MT3DMS, etc.).

GMS was designed as an exhaustive modeling situation. GMS has few types of models are supported, and facilities are ensured to share information between different models and data types [44]. Program tools are provided for location definition, geostatistics, model conceptualization, post-processing, and mesh and grid generation.

27

3.11 2D Mesh Modul

In this study, the SEEP2D module was used with 2D mesh module. The 2D

Mesh module in software is used to build two-dimensional finite element meshes.

SEEP2D model based on 2D meshes structure. The figure under show an example of a SEEP2D model is created using the 2D Mesh Module. GMS has provided three ways to create 2D Meshes. Automatic meshing technique, manually creating a 2D mesh and creating a 2D mesh from GMS data.

Figure 3.5: 2D projection mesh sample (Source: GMS 10.2 Tutorial)

3.12 SEEP2D Module

A SEEP2D module was developed by Fred Tracy of the United States Army

Engineer Waterways Experiment Situation to model a variety of problems involving seepage. SEEP2D model is a two-dimensional steady-state finite element groundwater

28 model type. Saturated flow type and unsaturated flow type can be simulated. SEEP2D is planned to be used on profile models (XZ models) such as cross-sections of levees or earth dams [44].

Different types of options are ensured in GMS for showing SEEP2D results. In the software, flow vectors and contours of the total head can be plotted. Computing flow potential values at the nodes can be optionally available. For plot lines, these values can be used. The equipotential lines and the flow lines can be used to plot a flow net. The phreatic surface can be showed [44].

SEEP2D can be modeled with these following conditions [45]:

a. Isotropic type of soil and anisotropic type of soil properties.

b. Confined type of flow and unconfined type of flow for profile models.

c. Axisymmetric type of models such as flow from a well.

d. Confined type of flow for plan models.

e. Saturated type of flow and/or unsaturated type of flow for unconfined

profile models.

f. Heterogeneous type of soil conditions.

g. Drains measurement.

h. Flow simulation in the saturated type of zones and unsaturated type of

zones.

SEEP2D cannot be modeled with these following conditions:

a. Transient type of problems or time varying type of problems.

b. Type of unconfined plan models.

29

3.12.1 Finite Element Method

The SEEP2D numerical modeling system was used in the flow calculation through a cross-section of the dams and levees. The software was improved to model a diversity of problems involving steady-state of seepage. The SEEP2D model is based on the following by governing Richards’ equation [45]:

∂ ∂h ∂h ∂ ∂h ∂h (Kxx + Kxy ) + (Kyy + Kyx ) = 0 (1) ∂x ∂x ∂y ∂y ∂y ∂x where, h = total head (elevation head plus pressure head),

K = hydraulic conductivity.

Finite element method (FEM) is used for solving the governing equation with the model and the study field being modeled is represented by a finite element mesh.

After a mesh has been constructed, boundary conditions are performed to the mesh.

The software has five types of boundary conditions which are no flow, constant head, exit face, flow rate, and flux boundary conditions [45]. In this study, three types boundary conditions are determined which are the constant head, flow rate, and exit face boundary conditions. Constant head boundary conditions represent boundaries where the head is known. Flow rate condition defines zero for downstream part of the dam because in this study focus on slurry trench flow rate, not slurry trench and dam flow rate. Exit face boundary conditions are used while modeling unconfined flows and should be placed along the face where the free surface is probably to exit the model.

In the model, under the problem type title, type of flow should be noted. There are two types of flow for calculation such as plane flow or axisymmetric flow [46]. If the model includes single well, axisymmetric flow should be choosing, but for this

30 model, plane flow was selected. Next, the model type should be selected. There are two types of the model under this title such as saturated/unsaturated with linear front, and

Van Genuchten saturated/unsaturated model. Van Genuchten model was selected for the model type [47].

3.12.2 Van Genuchten Parameter

For computing relative hydraulic conductivity, Van Genuchten (1980) developed a model with using a term of effective saturation [45]. Since the Van

Genuchten parameters are acceptable, they are used in other software. The equation is below [48]:

n −m S̅ = [1 + (αhp) ] (2)

S̅ = the effective saturation α = the inverse of the air entry pressure n = the slope of soil water characteristic curve at its inflection point m = the asymmetry of the soil water characteristic curve about its inflection point h = the pressure head

1 m = 1 − (3) n

After above calculation, the relative hydraulic conductivity, kr, can be defined by the equation below:

1 1 m 2 kr = S̅2[1 − (1 − S̅m) ] (4)

Table 3.3: Use of Van Genuchten values in other numerical programs (Source: US

Army Corps of Engineers) [49].

Method SEEP2D SEEP/W SLIDE Gardner (1958) ✓ Brooks and Corey (1964) ✓ Fredlung and Xing (1964) ✓ ✓ Van Genuchten (1990) ✓ ✓ ✓

31

Table 3.4: Van Genuchten Parameters α and n (Source: SEEP2D Primer).

α and n parameters Soil Type α (cm-1) n Clay** 0.008 1.09 Clay Loam 0.019 1.31 Loam 0.036 1.56 Loam Sand 0.124 2.28 Silt 0.106 1.37 Silt Loam 0.020 1.41 Silty Clay 0.005 1.09 Silty Clay Loam 0.010 1.23 Sand 0.145 2.68 Sandy Clay 0.027 1.23 Sandy Clay Loam 0.059 1.48 Sandy Loam 0.075 1.89 **Agricultural soil, less than 60% clay.

3.13 Mesh Convergence

For determining correct results from the software, the mesh convergence must be selected correctly. Different mesh sizes have been tested to determine true mesh convergence. The software has given the error when selecting the interval of mesh below 0.90 m. So, the range of mesh should be over 0.90 m. The mesh intervals of 0.90 m, 1 m, 2 m, 3 m, 4 m, and 5 m were chosen to test the mesh convergence. The results are shown below.

32

3.00E-05

2.50E-05

/s)/(m) 3 2.00E-05

1.50E-05

1.00E-05 SeepageRate(m

5.00E-06 0 1 2 3 4 5 6 Interval of Mesh (m)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.6: Relationship between seepage rate and interval of mesh (Thickness of

slurry trench=100 cm, keyed depth of slurry trench=3 m, permeability of slurry

trench=4*10-9 m/s)

According to the results, 0.90 m and 1 m mesh sizes gave the same seepage results. The mesh size above 1 m has increased leakage values. Since the mesh size of 0.90 m has taken time to calculate and given the same result as the mesh size of 1 m, mesh size 1 m was selected in all calculations.

3.14 Model Building

When started the software, “Create a new project,” “SEEP2D”, “Profile lines” was chosen in the new project wizard.

33

Figure 3.7: Project wizard

After the select new project tool, program model will be GMS 2D. The user can change program mode Edit/Preferences wizard. Selecting the program mode tool, the user can see four types mode, but GMS 2D should be chosen for ease of use.

34

Figure 3.8: Opening view of the software

Select “Edit/Units” to open the Units dialog. The units table is shown below. Click the length (three-point) to open display projection wizard for horizontal and vertical units.

Figure 3.9: Display of units

Before setting up the conceptual model features, first, define a coordinate system on the dam. To determine coordinate systems, right-click the profile lines and select the attribute table to enter points than click OK to exit the dialog (Figure 3.8).

35

Figure 3.10: Defining coordinates a model design

After creating the points, using the build arc tool to connect series of arcs around of perimeter of the dam. After this technic, the points are changed to nodes (Figure 3.10 and Figure 3.11).

36

Figure 3.11: Creating corner points with attribute table

Figure 3.12: Creating arcs with use nodes

Next process is creating the polygons. Click “Build Polygons” below the “Feature

Objects” tool (Figure 3.12).

37

Figure 3.13: Background colored a gray after build polygons

After this process, materials should be defined so click “Materials” to bring up the dialog to write each polygon and should be set (Figure 3.13). Permeability rates are meter/second.

Figure 3.14: Defining material properties (Material data obtained from DSI)

After these process, click “Select Polygons” tool and select each zone and defined. For instance, double-click inside the alluvium polygon to bring up the “Attribute Table”

38 then select “Alluvium” from the drop-down in the “Material” column of the spreadsheet and click OK. This process applied to other polygons (Figure 3.14).

Figure 3.15: Determining the different material assignments

After the determining material assignments, select “Select Arcs” tool and double-click the left-side (blue line) and right-side (red line) arcs to bring up the “Attribute Table” to define boundary conditions (Figure 3.15 and Figure 3.16). For each water level conditions, left-side boundary condition value is changed. For instance, for minimum water level condition (19.5 m) head was chosen 810 m, for normal water level condition

(48.3 m) was selected 838.8 m, and for maximum water level condition (50.85 m) was determined 841.35 m.

39

Figure 3.16: Defining boundary conditions part of left-side of dam

Figure 3.17: Defining boundary conditions part of right-side of dam

Next step is building finite element mesh. In the conceptual model, the mesh is constructed automatically from polygons and arcs. Select “Select Arcs” tool and select all of the arcs. Then select “Feature Objects” and chose “Redistribute Vertices” dialog.

To determine mesh density, select “Specified spacing” from the “Specify” drop-down and enter “1” for “Average” spacing and click OK (Figure 3.17). Then select “Select

Vertices” tool to see mesh spaced (Figure 3.18).

40

Figure 3.18: Building density of mesh size

Figure 3.19: Equally-interspace vertices

After these process, click the “Map→2D Mesh” to create a 2D mesh and conceptual model converted to the SEEP2D numerical model (Figure 3.19).

41

Figure 3.20: Creating 2D mesh

Then click “Map→SEEP2D” tool and node-based boundary conditions assigned

(Figure 3.20). The boundary conditions have been assigned to the set of red and blue symbols appeared.

Figure 3.21: SEEP2D boundary conditions

Before running the model, the model should save. Then select “SEEP2D” and chose

“Analysis Options” to bring up “SEEP2D Analysis Option” dialog (Figure 3.21). Unit

42 weight of water was determined 9810 (N/m3), problem type was chosen “Plane flow,” the model type was chosen “Van Genuchten saturated/unsaturated model,” and

“Compute flow lines” was clicked. Next, save the model.

Figure 3.22: Analysis option wizard

For the running solution, click the “Run SEEP2D” to bring up the SEEP2D model wrapper dialog (Figure 3.22).

Figure 3.23: Starting finite element method calculation

43

3.15 Slurry Wall Construction Features

Slurry trench construction started at 01.04.2016 and finished 06.29.2016. For providing impermeability of alluvium foundation, the slurry trench was assembled with the most profound point of 7.10 m and the shallowest point 46.80 m and 1 m thickness point so that the upstream part was connected to the concrete through the western region. Construction values are below.

Table 3.5: Construction values of slurry trench (Source DSI)

Panel Crest of Dam Base of Dam Deep Area Amount of No (m) (m) (m) (m2) Concrete (m3) P1 800.25 774.95 25.3 79.189 77 P5 800.25 767.25 33 103.29 122 P2 800.25 772.45 27.8 87.014 88 P7 800.25 861.15 39.1 122.383 136 P4 800.25 767.55 32.7 102.351 120 P9 800.25 757.65 42.6 133.338 152 P6 800.25 762.65 37.6 117.688 120 P3 800.25 768.65 31.6 98.908 104 S1 800.25 775.25 25 58.25 88 P8 800.25 760.15 40.1 125.513 136 S5 800.25 765.75 34.5 80.385 112 S2 800.25 773.15 27.1 63.143 96 S7 800.25 761.65 38.6 89.938 128 S4 800.25 767.85 32.4 75.492 112 S8 800.25 759.8 40.25 94.2485 144 S3 800.25 769.25 31 72.23 96 S6 800.25 761.85 38.4 89.472 128 S9 800.25 758.65 41.6 96.928 144 P32 800.25 761.65 38.6 120.818 128 P30 800.25 758.25 42 131.46 152 P31 800.25 760.25 40 125.2 152 P29 800.25 758.75 41.5 129.895 186 S33 800.25 761.25 39 90.87 128 S31 800.25 759.75 40.5 94.365 122.5 P28 800.25 750.25 43 134.59 164 S30 800.25 750.65 42.6 99.258 144 A14 800.25 775.05 25.2 78.876 96 A12 800.25 775.05 25.2 78.876 88 A10 800.25 774.45 25.8 80.754 84

44

Panel Crest of Dam Base of Dam Deep Area Amount of No (m) (m) (m) (m2) Concrete (m3) A8 800.25 774.45 25.8 80.754 88 S29 800.25 757.05 43.2 100.656 150 S32 800.25 761.65 38.6 89.938 128 A13 800.25 775.25 25 78.25 90 P27 800.25 755.55 49.7 139.911 184 A11 800.25 774.65 25.6 80.128 80 P25 800.25 755.85 44.4 138.972 184 P23 800.25 755.05 45.2 141.476 176 P21 800.25 753.45 46.8 146.484 168 P19 800.25 754.05 46.2 144.606 192 K14 800.25 775.25 25 58.25 80 P17 800.25 755.85 44.4 138.972 160 K12 800.25 775.25 25 58.25 88 K13 800.25 775.05 25.2 58.716 84 K11 800.25 775.25 25 58.25 80 P13 800.25 753.85 46.4 145.232 161 P11 800.25 754.45 45.8 143.354 160 A9 800.25 774.75 25.5 79.815 84 A7 800.25 774.25 26 81.38 89 A5 800.25 782.05 18.2 56.966 64 K10 800.25 775.25 25 58.25 96 A6 800.25 781.45 18.8 58.844 64 A4 800.25 787.65 12.6 39.438 40 A3 800.25 794.55 5.7 17.841 24 K8 800.25 774.25 26 60.58 88 K6 800.25 783.65 16.6 38.678 48 K9 800.25 773.95 26.3 61.279 76 K7 800.25 779.95 20.3 47.299 64 K5 800.25 786.25 14 32.62 40 P15 800.25 753.75 46.5 145.545 168 P26 800.25 758.75 41.5 129.895 168 P22 800.25 754.45 45.8 143.354 184 P20 800.25 754.75 45.5 142.415 113.93 P24 800.25 755.45 44.8 140.224 184 P18 800.25 754.25 46 143.98 150 P16 800.25 753.9 46.35 145.0755 160 P14 800.25 754.1 46.15 144.4495 160 P12 800.25 753.45 46.8 146.484 152 P10 800.25 755.15 45.1 141.163 152 S28 800.25 756.05 44.2 102.986 136 S26 800.25 755.45 44.8 104.384 128 S24 800.25 754.95 45.3 105.549 138 S22 800.25 754.65 45.6 406.248 144

45

Panel Crest of Dam Base of Dam Deep Area Amount of No (m) (m) (m) (m2) Concrete (m3) S18 800.25 754.55 45.7 106.481 144 S16 800.25 753.95 46.3 107.879 132 S14 800.25 753.85 46.4 108.112 140 S12 800.25 754.25 46 107.18 132 S10 800.25 757.65 42.6 99.258 132 S27 800.25 756.25 44 102.52 144 S25 800.25 755.45 44.8 104.384 138 S23 800.25 754.8 45.45 105.8985 132 S21 800.25 755.25 45 104.85 158 S19 800.25 754.15 46.1 107.413 144 S17 800.25 754.15 46.1 107.413 136 S15 800.25 754.05 46.2 107.646 136 S13 800.25 753.95 46.3 107.879 140 S11 800.25 754.95 45.3 105.549 132 S20 800.25 750.95 46.3 107.879 138 A15 800.25 763.05 37.2 116.436 120 K4 800.25 793.15 7.1 16.543 24 A17 800.25 764.25 36 112.68 112 A19 800.25 766.65 33.6 105.168 124 A21 800.25 767.31 32.94 103.1022 112 A23 800.25 773.75 26.5 82.945 80 A16 800.25 764.05 36.2 113.306 112 A18 800.25 765.25 35 109.55 119 A20 800.25 766.25 34 106.42 113 A31 800.25 777.4 22.85 71.5205 76 A22 800.25 770.75 29.5 92.335 98 K15 800.25 763.45 36.8 85.744 120 K17 800.25 765.05 35.2 82.016 107 K19 800.25 766.85 33.4 77.822 96 K21 800.25 767.75 32.5 75.725 104 K16 800.25 764.15 36.1 84.113 96 K18 800.25 765.65 34.6 80.618 94 K20 800.25 767.25 33 76.89 96 K22 800.25 769.65 30.6 71.298 92 A25 800.25 771.45 28.8 90.144 80 A27 800.25 772.9 27.35 85.6055 82 A29 800.25 773.8 26.45 82.7885 80 A24 800.25 770.25 30 93.9 96 A26 800.25 771.55 28.7 89.831 90 A28 800.25 773.05 27.2 85.136 88 A30 800.25 774.85 25.4 79.502 84 K23 800.25 768.35 31.9 74.327 105 K25 800.25 770.85 29.4 68.502 96

46

Panel Crest of Dam Base of Dam Deep Area Amount of No (m) (m) (m) (m2) Concrete (m3) K27 800.25 772.05 28.2 65.706 92 K29 800.25 774.35 25.9 60.347 84 K24 800.25 770.25 30 69.9 88 K26 800.25 772.45 27.8 64.774 88 K28 800.25 772.85 27.4 63.842 80 K30 800.25 774.95 25.3 58.949 88 A33 800.25 774.95 25.3 79.189 80 A35 800.25 775.25 25 78.25 87 A37 800.25 775.3 24.95 78.0935 80 A39 800.25 783.45 16.8 52.584 57 A32 800.25 775.65 24.6 76.998 80 A34 800.25 774.7 25.55 79.9715 80 A36 800.25 775.3 24.95 78.0935 84 A38 800.25 779.25 21 65.73 64 K31 800.25 775.25 25 58.25 88 K33 800.25 774.95 25.3 58.949 70 K35 800.25 775.25 25 58.25 81 K37 800.25 775.95 24.3 56.619 80 K32 800.25 775.15 25.1 58.483 80 K34 800.25 776 24.25 56.5025 76 K36 800.25 775.3 24.95 58.1335 76 K38 800.25 779.85 20.4 47.532 76 K39 800.25 792.75 7.5 17.475 24 TOTAL 12878.5942 15272.43

3.16 Materials and Quantities Used in The Manufacture of Plastic Concrete Wall

For slurry trench construction, 12.878,59 m2 guide wall was constructed.

15.272,43 m3 plastic concrete was made. 4108-ton cement, 642-ton bentonite, and

10.599-ton 0-3 mm soil were used [42].

Table 3.6: Slurry trench mixture ratios (Source DSI).

Material Amount (kg) Percentage (%) Water 673 40.1 Soil 694 41.4 Cement 269 16 Bentonite 42 2.5

47

3.17 Control Tests of Slurry Trench Cutoff Wall

It has been tested in the laboratory to control the permeability and compressive strength of concrete used in slurry trench manufacturing [42].

Table 3.7: Slurry trench laboratory test results (Source DSI).

SAMPLE DEEP CURING UNCONFINED PERMEABILITY (m) DAY COMPRESSION TEST, TEST, k, (m/s) ** qu, (kPa) A-12 5 28* - 2.79E -09 17 28* 78 A-16 12 28* - 3.26E -09 27 28* 135 A-25 8 28* - 2.797E -09 22 28* 68 A-34 9 28* - 2.95E -09 18 28* 72 K-8 7 28* - 1.87E -09 20 28* 79 K-20 5 28* - 1.71E -09 17 28* 68 K-29 5 28* - 9.01E -09 20 28* 264 K-38 10 28* - 7.76E -09 15 28* 275 P-7 10 28* - 7.77E -09 35 28* 70 P-16 10 28* - 2.72E -09 30 28* 98 P-25 20 28* - 3.42E -09 35 28* 150 S-12 15 28* - 4.04E -09 40 28* 143 S-21 5 28* - 4.27E -09 40 28* 75 S-30 7 28* - 2.41E -09 32 28* 114 *=period days **= used 200kPa cell pressure and 100 kPa back pressure

48

3.18 Materials Permeability Properties

Dam structure is composed of some impermeable, and semi-impermeable materials. Because of the concrete face rockfill dam, embankment material permeability rate does not have to be high. Concrete face permeability and after two filters are provided an impermeable condition. Also, slurry trench wall is decreased seepage rate under the dam structure, especially alluvium foundation. Furthermore, the slurry trench and the concrete face are joined together to prevent dam construction and possible leakage.

Table 3.8: Hydraulic conductivity values assigned to layer soils, Koyunbaba Dam.

Materials Permeability Values (m/s) Van Genuchten Paremeters

kh kv α (1/m) n

Embankment 1*10-5 2.5*10-5 12.4 2.28 Alluvium 1*10-4 2.5*10-4 14.5 2.68 Basalt 1*10-6 1*10-7 14.5 2.68 Concrete 1*10-10 1*10-10 14.5 2.68 Riprap 1 1 14.5 2.68 Filter_1 2.5*10-8 2.5*10-9 1.6 1.37

Filter_2 5*10-6 5*10-7 1 1.23 Filter_3 1*10-5 1*10-6 5.9 1.48 Filter_4 1*10-2 1*10-2 1 1.23 Slurry_Trench 4*10-9 4*10-9 0.8 1.09

3.19 Plane Stress and Plane Strain

Two-dimensional elastic problems were the first sufficient samples of the application of the finite element method [50,51]. There are two common kinds of issues included in this plane analysis, plane strain and plane stress.

49

3.19.1 Plane Stress

Plane stress is determined to be a state stress in which the normal stress, σz, and the shear stress σxz and σyz focused vertical to the x-y plane are assumed to be zero.

The body geometry is fundamentally that of a plate with one dimension much lesser than the others. The loads are applied uniformly over the thickness of the plate and move in the plate plane. The plane stress status is the basic form of behavior for continuum structures and indicates situations regularly encountered in the application

[52].

Characteristic loading and boundary conditions for plate stress problems in two- dimensional elasticity.

a) Loadings might be point forces or spread forces applied over the thickness of

the plate.

b) Supports might be solid points or constant edges or roller supports.

3.19.2 Plane Strain

The plane strain is defined to be a state of strain in which the strain normal to the x-y plane, Ɛz, and the shear strain Ɣzx and Ɣyz, are assumed to be zero [52].

In-plane strain, one deals with a condition in which the structure dimension in one direction, say the z-coordinate direction, is very large in comparison with the structure dimensions in the other two directions (x-and y-coordinate axes), the body geometry is substantially that of a prismatic cylinder with one dimension much bigger than the others [52].

The applied forces move in the x-y plane and do not change in the z-direction, i.e., the loads are uniformly spread concerning the large dimension and move vertically

50 to it. Some essential convenient applications of this representation occur in the analysis of dams, tunnels, and other geotechnical works [52].

3.20 Results

Seepage rates for some different condition were evaluated. These are the various place of the slurry trench under the dam, different lateral distance from upstream of embankment condition, different slurry trench thickness, different keyed depth of slurry trench, different slurry trench permeability rate, and two slurry trench condition.

3.21 Measured Seepage Rate with Different Conditions

In this part, seepage rate measured with different places, different lateral distances from upstream, different thicknesses, different permeabilities, different keyed depths were examined.

51

3.21.1 Koyunbaba Dam Geometry and Features With/Without Place of Slurry Trench Wall Condition

3.21.1.1 Without Slurry Trench Condition

8 m Parapet Wall Maximum Water Level Normal Water Level

1.70 1

1.70 1 Minimum Water Level

Embankment 51.35 m 51.35 Riprap Filter

Concrete Face

50.85m

48.3 m 48.3 19.5 m 19.5

Alluvium Layer Filter

Embankment Alluvium Layer

Impervious Layer Impervious Layer Impervious Layer Impervious Layer

30 m 30 m 90 m 195 m 72 m

Figure 3.24: Koyunbaba Dam section view without slurry trench condition (Source DSI).

52

3.21.1.2 Slurry Trench Under the Upstream of Embankment Condition

8 m Parapet Wall Maximum Water Level Normal Water Level

1.70 1

1.70 1 Minimum Water Level

Embankment 51.35 m 51.35 Riprap Filter

Concrete Face

50.85m

48.3 m 48.3 19.5 m 19.5

Alluvium Layer Filter Alluvium Layer Embankment Slurry Wall 30 m Impervious Layer Impervious Layer Impervious Layer Impervious Layer

30 m 30 m 90 m 195 m 72 m

Figure 3.25: Koyunbaba Dam section view with slurry trench under the upstream of embankment condition (Source DSI).

53

3.21.1.3 Slurry Trench Under the Middle of Embankment Condition

8 m Parapet Wall Maximum Water Level Normal Water Level

1.70 1

1.70 1 Minimum Water Level

Embankment 51.35 m 51.35 Riprap Filter

Concrete Face

50.85 m 50.85

48.3 m 48.3 19.5 m 19.5

Alluvium Layer Filter Slurry Alluvium Layer Embankment Wall 30 m

Impervious Layer Impervious Layer Impervious Layer Impervious Layer

30 m 30 m 90 m 195 m 72 m

Figure 3.26: Koyunbaba Dam section view with slurry trench under the middle of embankment condition (Source DSI).

54

3.21.1.4 Slurry Trench Under the Downstream of Embankment Condition

8 m Parapet Wall Maximum Water Level Normal Water Level

1.70 1

1.70 1 Minimum Water Level

Embankment 51.35 m 51.35 Riprap Filter

Concrete Face

50.85m

48.3 m 48.3 19.5 m 19.5

Alluvium Layer Filter Slurry Embankment Wall Alluvium Layer 30 m

Impervious Layer Impervious Layer Impervious Layer Impervious Layer

30 m 30 m 90 m 195 m 72 m

Figure 3.27: Koyunbaba Dam section view with slurry trench under the downstream of embankment condition (Source DSI).

55

3.21.1.5 Profile of Slurry Trench with Guide Walls

Stabilizing Material Bentonite Guide Walls Itwill be removed after Slurry Trench Construction 8.55 m 8.55 m

Stabilizing Material 787.00 m 787.00 m 0.7 m 1 m 0.7 m 786.75 m 0.25 m 0.25 m

785.80 m

m Filter_2 1.20 m

0.95 m 785.30 m 1 1.70 0.30 m 1.45 m 1 Embankment 0.30 m 1.7 Material 1.5

Embankment 8.35 m Material 2.40 m 782.90 m 1 1.7

2 m 1 m 8 m

SLURRY TRENCH Thickness= 1 m

Figure 3.28: Slurry Trench profile applied in Koyunbaba Dam (Source DSI).

56

3.21.2 Seepage Rate Results for Different Places of Slurry Trench

Firstly, the influence of the slurry trench on the infiltration of different places under the dam has been examined. According to the results, the upstream of embankment place was found to be the best place to prevent seepage.

1.60E-03

1.40E-03

1.20E-03 /s)/(m) 3 1.00E-03

8.00E-04

6.00E-04

Seepage Rate (m RateSeepage 4.00E-04

2.00E-04

0.00E+00 Upstream of Embankment Under the Embankment Downstream of Embankment Without Slurry Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.29: Relationship between seepage rate and different place of slurry trench

(Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s, keyed

depth of slurry trench= 3m)

For all water level condition, upstream of embankment condition almost 60 times prevent the leakage than other places of the slurry trench. So, the location of the slurry trench under the upstream of the dam is the best choice.

57

3.21.3 Seepage Rate Results for Lateral Distance from Embankment

Regarding this subject, the influence of the lateral distance of the models was examined. These ranges are 90 meters, 120 meters and 150 meters from upstream of the embankment to the lake. According to the results, increasing the model lateral distance from the upstream of the embankment does not affect the amount of seepage.

Model lateral distances effect can be neglected. See below the graphs.

1.60E-03

1.40E-03

1.20E-03 /s)/(m) 3 1.00E-03

8.00E-04

6.00E-04

Seepage Rate (m RateSeepage 4.00E-04

2.00E-04

0.00E+00 Upstream of Embankment Under the Embankment Downstream of Embankment Without Slurry Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.30: Relationship between seepage rate and 90 meters lateral distance from upstream of embankment to the lake (Thickness of slurry trench= 1m, permeability of

slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3m)

58

1.60E-03 1.40E-03

1.20E-03 /s)/(m) 3 1.00E-03 8.00E-04 6.00E-04

4.00E-04 Seepage Rate (m RateSeepage 2.00E-04 0.00E+00 Upstream of Embankment Under the Embankment Downstream of Embankment Without Slurry Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.31: Relationship between seepage rate and 120 meters lateral distance from

upstream of embankment to the lake (Thickness of slurry trench= 1, permeability of

slurry trench= 4*109 m/s, keyed depth of slurry trench= 3m)

1.60E-03 1.40E-03

1.20E-03 /s)/(m) 3 1.00E-03 8.00E-04 6.00E-04 4.00E-04 Seepage Rate (m RateSeepage 2.00E-04 0.00E+00 Upstream of Embankment Under the Embankment Downstream of Embankment Without Slurry Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.32: Relationship between seepage rate and 150 meters lateral distance from upstream of embankment to the lake (Thickness of slurry trench= 1m, permeability of

slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3m)

59

3.21.4 Seepage Rate Results for Different Thickness of Slurry Trench

According to the results, seepage rate is affected by the thickness of slurry trench. For the permeable foundation, as the thickness of slurry trench increases, the seepage value decreases. ICOLD (1985) indicated that the trench should be between

150 cm and 300 cm thickness but this condition just valid for bentonite slurry trench

[3]. In this study, involved recent development which means soil-cement-bentonite slurry trench methodology and for this technique slurry trench thicknesses were selected between 60 cm to 150 cm. Slurry trench under the upstream of embankment condition is evaluated.

3.00E-05

2.50E-05

/s)/(m) 3 2.00E-05

1.50E-05

1.00E-05 SeepageRate(m

5.00E-06 50 60 70 80 90 100 110 120 130 140 150 160 Thickness of Slurry Trench (cm)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.33: Relationship between seepage rate and thickness of slurry trench (Keyed

depth of slurry trench=3 m, permeability of slurry trench= 4*10-9)

3.21.5 Seepage Rate Results for Different Keyed Depth of Slurry Trench

If the permeable layer is at a cost-acceptable depth, the slurry trench can be extended to an impermeable layer or can be keyed to impermeable layer. In this study evaluated non-keyed and keyed conditions. Slurry trench under the upstream of embankment condition is evaluated. See below graphs.

60

1.20E-03 1.00E-03

/s)/(m) 8.00E-04 3 6.00E-04 4.00E-04 2.00E-04

SeepageRate(m 0.00E+00 -2.00E-04 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 Keyed Depth of Slurry Trench (m)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.34: Relationship between seepage rate and keyed depth of slurry trench

(Negative keyed depth values mean, base of slurry trench over the base of alluvium)

(Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

6.10E-05

5.10E-05

/s)/(m) 3 4.10E-05 3.10E-05 2.10E-05

SeepageRate(m 1.10E-05 1.00E-06 -1 0 1 2 3 4 5 6 Keyed Depth of Slurry Trench (m)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.35: Relationship between seepage rate and keyed depth of slurry trench

(Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

The graphs show that keyed depth of the slurry trench and effecting seepage rate. 0 meter mean border of alluvium layer and impermeable layer. Negative values indicated that the distance from slurry trench base to the alluvium base. The first graphic showed

61 that over the 5m from the bottom of alluvium to 5m below the alluvium-impermeable layer border. The second graphic showed that 5m below the alluvium-impermeable layer border.

3.21.6 Seepage Rate Results for Different Slurry Trench Permeability Rate

According to ICOLD (1985), slurry trench permeability rate range between 10-

8 m/s to 10-10 m/s [3]. In this research, three permeability rates were selected to evaluate seepage rate effected by permeability rate. Slurry trench under the upstream of the embankment is evaluated.

3.50E-05

3.00E-05 /s)/(m)

3 2.50E-05

2.00E-05

1.50E-05

1.00E-05 SeepageRate(m 5.00E-06 1.0E-11 1.0E-10 1.0E-09 1.0E-08 1.0E-07 Coefficient of Permeability of Slurry Trench (m/s) Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.36: Relationship between seepage rates and permeability of slurry trench

(Thickness of slurry trench= 1m, keyed depth of slurry trench= 3m)

3.22 In the Case of Two Slurry Trenches

In this part, if the second slurry is added to the trench how it will affect the seepage has been studied. Two different conditions have been investigated for this purpose. According to previous results, the first slurry trench should be under the upstream of the embankment. The second slurry trench has added the middle of embankment and the downstream of embankment, respectively.

62

3.22.1 Seepage Rate Results for Upstream of Embankment and Middle of

Embankment Condition

The effect of the second slurry trench on the seepage rate was studied graphically. The permeability of slurry trenches was taken as 4*10-9 m/s, and keyed depth of slurry trenches was taken at 3 meters. See the condition and results.

Figure 3.37: Two slurry trench in the alluvium foundation. Places of upstream of

embankment and middle of embankment.

3.00E-05

2.50E-05

/s)/(m) 3 2.00E-05

1.50E-05

1.00E-05

SeepageRate (m 5.00E-06 50 60 70 80 90 100 110 Thickness of Slurry Trench (cm) Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.38: Relationship between seepage rates and slurry trench thickness with two

slurry trench condition (Keyed depth of slurry trenches= 3m, permeability rate of

slurry trenches= 4*10-9 m/s)

63

3.22.2 Seepage Rate Results for Upstream of Embankment and Downstream of

Embankment Condition

In this study, first slurry trench under the upstream of embankment and second slurry trench under the downstream of embankment. The permeability of slurry trenches was taken as 4*10-9 m/s, and keyed depth of slurry trenches was taken at 3 meters. See the condition and results.

Figure 3.39: Two slurry trench in the alluvium foundation. Places of upstream of

embankment and downstream of embankment.

3.00E-05

2.50E-05

/s)/(m) 3 2.00E-05

1.50E-05

1.00E-05

SeepageRate (m 5.00E-06 50 60 70 80 90 100 110 Thickness of Slurry Trench (cm) Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.40: Relationship between seepage rates and slurry trench thickness with two

slurry trench condition (Keyed depth of slurry trenches= 3m, permeability rate of

slurry trenches= 4*10-9 m/s)

64

3.23 Factor of Safety for Vertical Piping

Dams are constructed with high construction costs and will be used for many years at the same time. For this reason, the structure and foundation of the barrier must be examined and evaluated. The downstream toe of the embankment is one of the critical areas because piping, blowouts, and excessive seepage can occur. Seepage analyses are frequently related to assessing such areas for potential piping. There are no clear principles when evaluating a location of along the toe.

SEEP2D does not calculate the factor of safety against piping but the software does provide hydraulic gradients at nodes within the finite element mesh, so it can be used for calculating the factor of safety against piping. The factor of safety can be calculated for each nodal point individually, but the average hydraulic gradient over the entire surface was evaluated.

Vertical Seepage Exit

Firstly, should be determined which part of foundation hydraulic gradient to use for calculating the factor of safety. In this study, evaluation area up to 11 meters distance from the toe of downstream and up to 2.5-meter-deep from the surface. The equation for the factor of safety against piping is below.

W′ FS = (5) U

FS = Factor of Safety

W′= Submerged weight of soil

U = Uplifting force caused by seepage

65

W′ = (0.5)D2Ɣ′ (7)

2 U = (0.5)D iavƔw (8)

Ɣ′ FS = (9) iavƔw

Where D is the depth, Ɣw is the unit weight of water, iav is the average hydraulic gradient, and Ɣ′ is the saturated unit weight of soil. iav values were obtained from GMS software. Ɣ′ value was obtained from Koyunbaba dam of DSI.

Harr (1962, 1977) has proposed a factor of safety of 4-5 [53]. Following the above information, the reliability of the slurry trench in various cases was evaluated by the factor of safety.

Figure 3.41: Reference area for calculation of the factor of safety

66 3.23.1 Factor of Safety for Different Place of Slurry Trench

For the different place of slurry trench condition and without slurry trench condition, the factor of safety was calculated. The vertical piping safety factor of the slurry trench is higher than that of the non-slurry trench, and these coefficients indicate that the construction is on the safe side.

6

5

4

3

2 FactorofSafety 1

0 Downstream of Under the Upstream of Without Slurry Embankment Embankment Embankment Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.42: Relationship between factor of safety and different place of slurry trench

(Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s, keyed

depth of slurry trench= 3m)

3.23.2 Factor of Safety for Lateral Distance from Embankment

Three lateral distance from embankment conditions has been evaluated. These terms are 90 meters, 120 meters, 150 meters lateral distance from embankments. In these three situations, just without slurry trench conditions were failed and other states have an acceptable factor of safety rates.

67

6

5

4

3

2 FactorofSafety 1

0 Downstream of Under the Upstream of Without Slurry Embankment Embankment Embankment Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.43: Relationship between factor of safety and 90 meters lateral distance from

upstream of embankment (Thickness of slurry trench= 1m, permeability of slurry

trench= 4*10-9 m/s, keyed depth of slurry trench= 3m)

6

5

4

3

2 FactorofSafety 1

0 Downstream of Under the Upstream of Without Slurry Embankment Embankment Embankment Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.44: Relationship between factor of safety and 120 meters lateral distance from upstream of embankment (Thickness of slurry trench= 1, permeability of slurry

trench= 4*109 m/s, keyed depth of slurry trench= 3m)

68

6

5

4

3

2 FactorofSafety 1

0 Downstream of Under the Upstream of Without Slurry Embankment Embankment Embankment Trench Place of Slurry Trench

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.45: Relationship between factor of safety and 150 meters lateral distance

from upstream of embankment (Thickness of slurry trench= 1m, permeability of

slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3m)

3.23.3 Seepage Rate Results for Different Thickness of Slurry Trench

The effect of varying slurry trench thicknesses on the safety factor was studied.

It has been observed that in all thickness conditions the safety factor rates are acceptable coefficients. Over 100 cm thickness of slurry trench safety coefficient for three water level conditions is increased.

69

4.5

4.45

4.4

4.35

4.3

FactorofSafety 4.25

4.2

4.15 50 60 70 80 90 100 110 120 130 140 150 160 Thickness of Slurry Trench (cm)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.46: Relationship between factor of safety and thickness of slurry trench

(Keyed depth of slurry trench=3 m, permeability of slurry trench= 4*10-9)

3.23.4 Seepage Rate Results for Different Keyed Depth of Slurry Trench

In this study showed that how the factor of safety rate was affected by the keyed depth of the slurry trench. At the minimum water level condition, the safety factor coefficient is found to be over the acceptable safe level but other water level conditions, safety coefficients are below 4. These results showed that the extension of the slurry trench base to the boundary of the alluvial layer with the impermeable layer or should be keyed to impermeable layer.

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4.4 4.3 4.2 4.1 4 3.9

FactorofSafety 3.8 3.7 3.6 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 Keyed Depth of Slurry Trench (m)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.47: Relationship between seepage rate and keyed depth of slurry trench

(Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

3.23.5 Factor of Safety for Different Slurry Trench Permeability Rate

In this section, the relation to the safety factor of the different permeability coefficients is evaluated. According to the results, the recommended permeability values for the slurry trench are in the acceptable safety factor zone.

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4.32 4.3 4.28 4.26 4.24 4.22

FactorofSafety 4.2 4.18 4.16 1.0E-07 1.0E-08 1.0E-09 1.0E-10 1.0E-11 Coefficient of Permeability of Slurry Trenches (m/s) Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.48: Relationship between factor of safety and permeability of slurry trench

(Thickness of slurry trench= 1m, keyed depth of slurry trench= 3m)

3.24 In Case of Two Slurry Trenches

In this part, second slurry trench effect has been evaluated to the factor of safety.

The second slurry trench added the middle of embankment and downstream of the embankment, respectively.

3.24.1 Factor of Safety for Upstream of Embankment and Middle of Embankment

Condition

It has been determined that the second slurry trench placed under the middle of embankment does not increase the safety coefficient. The thickness of slurry trench has been selected between 60 cm to 100 cm because if chosen over 100 cm, it was not an economical solution.

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4.5

4.4

4.3

4.2 FactorofSafety 4.1

4 50 60 70 80 90 100 110 Thickness of Slurry Trench (cm)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.49: Relationship between factor of safety and thickness of slurry trench with two slurry trench condition (Keyed depth of slurry trench= 3m, permeability of slurry

trench= 4*10-9 m/s)

3.24.2 Factor of Safety for Upstream of Embankment and Downstream of

Embankment Condition

It has been determined that the second slurry trench placed under the middle of embankment does increase the safety coefficient. With second slurry trench in place of downstream of embankment condition, safety coefficients are increased.

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5.3

5.2

5.1

5

FactorofSafety 4.9

4.8 50 60 70 80 90 100 110 Thickness of Slurry Trench (cm)

Minimum Water Level Normal Water Level Maximum Water Level

Figure 3.50: Relationship between factor of safety and slurry trench thickness with two slurry trench condition (Keyed depth of slurry trenches= 3m, permeability rate of

slurry trenches= 4*10-9 m/s)

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CHAPTER IV

CONCLUSIONS

4.1 Conclusion

In chapter 3, seepage results and safety factors are shown in the graphs.

According to these results, firstly the safety coefficient of slurry trench construction should be of the accepted value. After the agreed safety factor, the seepage value that can be selected according to the conditions (e.g., cost, amount of water source).

The factor of safety results showed that different slurry thicknesses and permeabilities are in the safe zone, but the keyed depth of the slurry trench is critical.

Safety coefficients for the slurry trench depths from over the boundary of the alluvium- impermeable layer to the surface are below the accepted safety factor coefficient value.

Therefore, the slurry trench should be connected to the impermeable layer or extended to the impervious area.

Seepage rate results showed that the best place of the slurry trench should be constructed under the upstream of the embankment. Location of the slurry trench under the middle of the embankment or the downstream of embankment condition seepage rates are almost same as without slurry trench condition. Slurry trench thicknesses from

60 cm to 150 cm, the amount of seepage is reduced by 98-98.5%. As the distance of the slurry trench base from the alluvium-impermeable layer border to the surface increases, the seepage amount has been increased. For instance, 5 meters away from the alluvium- impermeable layer border, the amount of seepage is reduced 25%, but 1 meter away

75 from the alluvium-impermeable layer border, the amount of leakage is reduced 45%.

On the other hand, slurry trench base to the alluvium-impermeable layer border, the amount of seepage is reduced 96%. Also, if slurry trench keyed to the impermeable layer from 1 meter to 5 meters, the amount of seepage is diminished 98-98.5 %. For different slurry trench permeabilities, the amount of seepage is reduced 97.6-98.7%.

4.2 Recommendations

In this study showed that slurry trench is very useful for reducing seepage rate for the permeable layer. The new developments in the slurry trench have cut the cost of extensive excavation and prevented the seepage under the dam and increased the durability of the barriers. Thickness, keyed depth, and permeability are important criteria for planning slurry trench construction. The model is not entirely validated. All conclusions in this thesis can be only suitable for this case study.

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APPENDIX

90-meter lateral distance from upstream of embankment

A.1: Relationship between water flow lines with non-slurry trench condition

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A.2: Relationship between water flow lines with slurry trench under the downstream of the embankment (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3 m)

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A.3: Relationship between water flow lines with slurry trench under the middle of the embankment (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3 m)

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A.4: Relationship between water flow lines with slurry trench under the upstream of the embankment (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s, keyed depth of slurry trench= 3 m)

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Different Keyed Depth of Slurry Trench

A.5: Relationship between water flow lines with slurry trench. The base of slurry trench is at 3 meters above the boundary of the impermeable layer with alluvium layer (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

85

A.6: Relationship between water flow lines with slurry trench. The base of the slurry trench is at the boundary of the impermeable layer with alluvium layer. (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

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A.7: Relationship between water flow lines with slurry trench. The slurry trench is keyed 3 meters depth of the impermeable layer (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

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With the Second Slurry Trench Condition

A.8: Relationship between water flow lines with slurry trench under the upstream of the embankment and middle of the embankment. The slurry trench is keyed 3 meters depth of the impermeable layer (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10- 9 m/s)

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A.9: Relationship between water flow lines with slurry trench under the upstream of the embankment and downstream of the embankment. The slurry trench is keyed 3 meters depth of the impermeable layer (Thickness of slurry trench= 1m, permeability of slurry trench= 4*10-9 m/s)

89