control seepage thought earth dams

Control seepage through earth dam

AHMED MANSOR Control seepage through earth dams

Control Seepage Thought

Earth Dams

Ahmed Mansor

Supervision

Dr.Samar Mohamed

Eng.Ahmed Fathey


ACKNOWLEDGMENTS:

Thank Everyone add to me something positive in my life

Thank you :

Dr.Samar Mohamed

Eng. Ahmed Fathey

Ahmed Mansor

1


ABSTRACT:

This study was competent studied earth dams and species and its history

and the factors influencing them and the other part of a study of the most

important risks that affect earth dams (seepage through earth dams) and

how to calculate the leak and methods of their account and types the

seepage and forms of cost and what are the ways process is treated with

filters.

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TABLE OF CONTENTS

ACKNOWLEDGMENTS 1

ABSTRACT 2

NOMENCLATURE

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CHAPTER 1

1. INTRODUCTION TO SEEPAGE THROGH EARTH DAM 6

1.1What the earth dam?

6

1.2Type of earth dam 6

1.3 Choose depends on the type of dam 8

1.4 History 8

1.5 Requirements of Safety 10

CHAPTER 2

2.METHODS CALCULATION SEEPAGE THROGH EARTH

DAM

11

2.1 Calculation of seepage through an earth dam

resting on an impervious base 11

Dupuit`s Solutions 11

Shcafferank`s Solutions for α 30°

12

Gasagrande`s Solutions for α 30°

13

CHAPTER 3

3. ENTRANCE, DISCHARGE, AND TRANSFARE

CONDITIONSOF LINE OF SEEPAGE 15

3.1. Type of Discharge and Transfer 15

3.2. Drawi g etwork of da ’s dirt ru off 16

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CHAPTER 4

4.SIMULATE THE PRESSURE ON THE EARTH DAM USING SAP 2000 PROGRAM 17 18

4.1Design The Dam 18

4-2Analysis in two Cases 22

5.DESIGN FILTER TO CONTROLED THE SPAAGE IN EARTH DAM

5.1 Use filter 23

5.2 Terms of material selection, which makes them a Filter 23

5.3 Terms various specifications of the candidate 25

6.CONCLUSIONS AND DISCSSION 26

7.REFERENCES 27

4

CAHPTER 5


Nomenclature:

Quantity Units Name unit

q ( flow ) m\s Meter per second

Distances m Meter

F (force ) t Ton

Moment t.m Ton*meter

Grain size m.m Mile meter

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CHAPTER 1

INTRODUCTION TO SEEPAGE THROUGH EARTH DAMS

1.1 What the earth dams?

The earthworks to order water and store it or to protect the site during the

implementation of the foundations work. Earth dams made of earth and

therefore different levels of water in front of and behind the dam is causing

leakage of water from the dam through the dam.

1.2 Types of earth dams

Homogeneous dam with internal drainage on impervious foundations.

Central core dam on impervious foundations.

Inclined core dam on impervious foundations.

Homogeneous dam with internal drainage on pervious foundations.

Central core dam on pervious foundations.

Dam with upstream impervious zone on pervious foundations.

Other type dams :

1- Concrete.

2- Roller Compacted concrete.

3- Debris flows.

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Figure 1-1. Types of dam sections

Figure 1-2 Roller compacted concrete

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Figure 1-3 Debris flows dam

1-3 Choose depends on the type of dam

Materials available

The transfer of materials that are not available from the remote location

is too expensive in addition to the cost of materials.

Land quality and soil, which will be held by the dam

So as to protect the dam from landing and that the soil and ground

borne.

Study Zone

Are basic materials are available?

Are the rocks are available?

1-4 History

Levees or dikes have protected lands since primitive times and earth

dam have been used for the storage water for human need and

protection for more than 2000 years. In the year 500 B.C (1)

. An earth

dam containing nearly 20 million cu(2)

. Yd (3)

. Of earth was completed in

Ceylon (Now Sri lanka).

Early dams and levees were constructed simply by heaping earthen

materials across an area to be blocked, human traffic often producing all

the compacting effort. Many of the early efforts were washed out by

overtopping , under seepage , or other destructive forces , but eventually

standards of practice emerged that can be called " rules of thumb "

These practices often had no real basis , except that something had

worked at a number of locations ; hence it might work elsewhere.

Even into the twentieth century dams and levees were being designed

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largely by empirical methods. Wegmann (1922) states:

The design of such work (earth dam) should not be based upon

mathematical calculations of equilibrium and safe pressure. As in the

case of masonry dam, but upon results found experience. Most of earth

dams constructed within the last century have had a large margin of

safety in resisting the water pressure , both as regards overturning and

sliding , and yet frightful disasters , such as the rapture of the Dale Dyke

and the Johnstown dam . Have resulted from the faults in designing

some details or from neglect in the construction of the work.

From about 1930 to the present time 1988, analytical and experimental

methods have had an increasingly important part in the design and

construction of earthwork. They will continue to play an important role in

the design of dams, but experience will also have a dominant place. As the

weaknesses of modern practices come to light in occasional failures new

standard will emerge. These standards will continue to improve because

they will be based on fundamental principles and broad experience.

Figure 1-4 Dale Dyke and the Johnstown dam

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1-5 Requirements of Safety

Their slopes must be stable under all conditions.

Their foundations must not be overstressed.

Safe against internal erosion and water forces and pressure.

But 80% of the dams collapse because uncontrolled seepage.

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CHAPTER 2

METHODS TO CALCULATION SPEEPAGE TROUGHT

EARTH DAMS

2-1 Calculation of seepage through an earth dam resting on an impervious

base:

Dupuit`s Solutions

In figure (2-1) Earth dam in it a, b is phreatic surface or the uppermost

line, Amount of leakage through a unit of length is given Darc law:

(q = k i A), Hydraulic slop is i Expressed � = ∆ ℎ � . Hence;

q = k ∆ ℎ

(y) (1) = k ∆ ℎ

(y)

∫ � � = ∫ � ��

qL = � − �

q = � − � …….… (2- 1)

Equation 1 represents the equivalent cut phreatic surface.

The equation did not take into account the entrance and exit. Should also note

that if Hz = 0, pheaticline cut the surface layer impermeable.

Fig. 1-2: Dupuit`s Solutions for flow through earth dam

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Phreatic line

Where:

H or h1: high upstream water.

He or h2: high downstream water.

L: length the x- axis under phreatic line.

X: length the x- axis.

K: coefficient of permeability.

Shcafferank`s Solutions for α 30°

In this way is a Phreatic line and a father who goes back tilt at a distance

of 1 and leakage per unit length appointed by using the triangle D C B

As in figure (2-2):

Fig. (2-2): Shcafferank`s Solutions for flow through earth dam

Shcafferank`s Solutions ( a , q ) :

q = Kh ℎ

= K (a sin α) (tan α) (2-4)

Where:

q: flow rate.

K: coefficient of permeability.

a: downstream slope distance.

h : high upstream .

a = � ∝ - √ �22∝ − √ �2� 2∝ ( 2-5 )

(2-2) (2-3)

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where : a : downstream slope distance .

L : Horizontal distance on the X axis .

H : high upstream .

Gasagrande`s Solutions for α 30°

Explain that in practice the curve A B must start from the point A` As

in figure ( 2 -3 ) :

Fig (2-3) Gasagrande`s Solutions

Gasagrande`s Solutions ( a , q )

q = kh ℎ

= k a �� ∝ (2-6)

where:

q : flow rate .

k : Anisotropic .

h : high upstream .

a : downstream slope distance .

a = S0 - √Sₒ − H2sin2∝ (2-7)

where :

a : downstream slope distance .

H : high upstream .

S0 : is length the curve A`CB .

13


Fig (2-4) Gasagrande`s Solutions through earth dam .

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CHAPTER 3

ENTRANCE, DISCHARGE, AND TRANSFARE

CONDITIONS OF LINE OF SEEPAGE

3-1 Type of Discharge and Transfer:

When the leakage from the center of a free disposition (high

permeability coefficient) to the center of impermeability few labs called

this Entrance cond.

When the leakage from the center of a few permeability to the center of

great permeability are called this discharge cond.

When the leakage from the center of a few permeability to permeability

less is called transfer.

Fig (3-1) Entrance Cond

Fig (3-2) Discharge Cond

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Fig ( 3-3 ) Transfer Cond

(3-2) Drawing network of dam’s dirt runoff

Drawing the Phreatic line.

ED: Head line, BA: Flow line.

Head line at any point on the Flow line equal = 0.

Drawing the Head line to Dam and cross point between the Head line

and Flow line it’s the start the equipotential line.

∆h = ℎ� ℎ (3-1)

Drawing the network of dam .

Calculate The flow rate to the Dam ( q ) from equation :

q = k h � ℎ � ℎ (3-2)

But If they permeability coefficient between the X-axis and Y-axis flow

is calculated by the following law:

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q = h � ℎ � ℎ √� � (3-3)

Where:

∆h: high of pressure of flow channel.

h: total high of pressure of flow channel.

q: flow through earth dam.

Kx: permeability coefficient for X-axis.

Ky: permeability coefficient for Y-axis.

Fig (3-4) Steps the drawing the Net flow for Earth Dam

Fig (3-5) the Number of flow channels and Pressure channel

Fig (3-6) The constant of the permeability coefficient

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CHAPTER 4

SIMULATE THE PRESSURE ON THE EARTH DAM

USING SAP 2000 PROGRAM

(4-1) Design The Dam:

Fig(4-1) Elevation Dam Fig(4-2) Isometric Dam

The Dimensions on the Dam

Fig(4-3) Dimensions on the Elevation Dam

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\

Fig (4-4) Dimensions on the Isometric Dam

Simulate the force that affects the water from upstream the dam to one

ton per meter.

Fig (4-5) Simulate the force that affects the water from upstream the dam to

one ton per meter.

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Fig (4-6) The Bending Moment Diagram from Force one Ton on the Dam

Fig (4-7) The Shear Force Diagram from Force one Ton on the Dam

20


Simulate the force that affects the water from upstream the dam to one

ton per meter in (2\3) of length the Dam Body and from downstream one

ton per meter in (1\3) of length the Dam Body.

Fig (4-8) Simulate the force that affects the water from upstream the dam to one ton

per meter in (2\3) of length the Dam Body and from downstream one ton per meter in

(1\3) of length the Dam Body.

Fig (4-9) Bending Moment Diagram for the Case

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Fig (4-10) Shear Force Diagram for the Case

(4-2) Analysis in two Cases:

Max B.M.D and Max S.F.D in two Cases : in Table (4-1)

Case 1 Case 2

Max B.M.D Max S.F.D Max B.M.D Max S.F.D

17.62 8.08 17.28 7.77

Chart (4-1) Relationship between Case 1 and Case 2

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CHAPTER 5

DESIGN FILTER TO CONTROLED THE SPAAGE IN

EARTH DAM

(5-1) Use of Filter:

Filter uses a process to control the leakage through the earth dam. And

when the flow of water from the soil into the soil soft coarse, it causes

dangerous where the soil is soft soil is coarse. Over time, this process

hinders the blanks in coarse soils. In such a case you must use the filter to

prevent the soils.

(5-2) Terms of material selection, which makes them a Filter:

The size of the blanks of a material Filter must be small enough for the

survival of larger grains in place.

Material made by a Filter must be a high permeability to prevent the

formation of a large leak or hydrostatic pressure forces the Filter.

Depending on the mixing process Bertram substance research candidate

the following values:

� F�85 S ≤ 4 to 5 (to satisfy condition 1) (5-1)

� 5 F� 5 S ≥ 4 to 5 (to satisfy condition 2) (5-2)

Where:

D15 (F): diameter through which 15% of Filter materials will pass.

D15 (S): diameter through which 15% of soil to be protector will pass.

The equations (5-1) and (5-2) Select the size distribution of the soil used

as a Filter.

For example the dam in fig (5-1) Where the size distribution of the

granules is arranged a curve in fig (5-2) then determined the 5D85(s) ,

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5D15(s) And it is located on the curve in Fig (5-2) Be a gradation of

granules suitable filter if it occurred in the shaded area in Fig (5-2)

Fig (5-1) Use of filter on earth dam

Fig (5-2) Determination of grin size distribution of soil filter

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(5-3) Terms various specifications of the candidate:

To avoid movement grained soil to be protected:

� 5 F� 5 S 20 (5-3)

�5 F�5 S 25 (5-4)

� 5 F�85 S 5 (5-5)

To avoid the leak forces high from filter:

� 5 F� 5 S 4 (5-6)

Material of filter should not be the size of grains crystallized more

than 3 inches (76.2mm) , (This is to avoid segregation in materials

in the filter)

To avoid internal motion of the granules in the soft candidate must

not be more than passing sieve 200 for 5%.

When using water leakage pipe assembly, the filter must take these

pipes to protect the soft-grained shelf to the inside of the tubes. And

to avoid movement martial Filter to drainage pipes should be the

availability of the following conditions:

�85 F � ℎ 1.2 to 1.4 (5-7)

�85 Fℎ � 1.0 to 1.2 (5-7)

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CONCLUSION AND DISCUSSION

Discussion:

In light of this study, we know that the earth dams have a history of a very

old and it was used in ancient purposes as important as agriculture, flood

protection, but the spread of these dams has not prevented it was

dangerous often because they are made without considering's prior and

not geometric laws was so the reason for its collapse and cause major

disasters and was the most important reasons for the collapse of earth

dams is the leakage that which is happening due to the heterogeneity of

the soil components of the bridge and not to control the flow inside the

soil components of the dam but with the development of science, there has

become a standard on which to base the dam of this type of dams and also

provides tools to control the leakage that occurs within them.

Conclusion:

Through this study was reached important results, including the

simulation of the origin of earth dam program SAP 2000 in two cases,

when the first case when the acting force only come from upstream and

the second case when the forces acting on the body of the dam from the

upstream and Down Stream has resulted in the case two given strains over

the dam through moments and shear strength representation and expense

through the relationship diagrams to clarify the relationship and when you

design the filter to control seep through the dam became clear that the

design of the filter depends size granules from the experience of sieves to

determine the type of soil suitable for the manufacture of a filter and that

each candidate particular purpose depending on the properties, which is

designed for.

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References

R.F Craig (1974) , "Craig`s Soil Mechanics" , Formerly Department of

civil Engineering , University of Dundee UK .

Cedergren, H.R. (1989) Seepage, Drainage and Flow Nets, 3rd

end, John

Wiley & Sons, New York.

Harr, M.E. (1962 ) Groundwater and Seepage, McGraw-Hill, New York.

Bishop, A.W. , Alpan , I., Bilght, G.E. and Donald , I.B. (1960) Factors

Controlling the strength of partly saturated cohesive soils, in proceedings

of the ASCE conference on shear strength of cohesive soils, Boulder, CO,

USA, ASCE , New York , pp 503-32 .

Bishop, A.W Green, G.E., Garga, V.K., Andersen, A. and Brown J.D.

(1971) A new ring shear apparatus and its application to the measurement

of residual strength, Geotechnique, 21, 273-328

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