HM169E

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Equipment for Engineering Education

Experiment Instructions

G.U.N.T. Gertebau GmbH

PO. Box 1125

D-22881 Barsbttel Germany

Phone (040) 670854-0

Fax (040) 670854-42

HM 169 Drainage and

Seepage Tank

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Experiment Instructions

Publication-No.: 03/99

Please read and follow the instructions before the first installation!

917.000 00 A 169 12

03/99

HM 169 Drainage & Seepage Tank

AllrightsreservedG.U.N.T.

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Table of Contents

1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Description of the Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4.1 Filling with Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.4.2 Adjust Water Supply and Overflow . . . . . . . . . . . . . . . . . . . . 6

2.4.3 Filling and Injecting the Dye . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.4.4 Maintenance and Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.1 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2 Risk for Unit and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4 Theoretical Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.1.1 Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.1.2 Flow Field, Flow Lines, Equipotential Lines . . . . . . . . . . . . 10

4.1.3 Seepage Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.2 Experiments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.2.1 Streamlines of a Pile Retaining Wall. . . . . . . . . . . . . . . . . . 14

4.2.1.1 Preparing the Experiment . . . . . . . . . . . . . . . . . . . . . . 14

4.2.1.2 Performing the Experiment . . . . . . . . . . . . . . . . . . . . . 15

4.2.2 Determining a Flow Field . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.2.3 Pressure distribution with a retaining wall. . . . . . . . . . . . . . 16

4.2.4 Stream Lines through an Earth Bank . . . . . . . . . . . . . . . . . 16

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4.2.5 Pressure Distribution on a Foundation . . . . . . . . . . . . . . . . 16

4.2.6 Pressure on a Bulkhead . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.2.6.1 Preparing the Experiment . . . . . . . . . . . . . . . . . . . . . . 17

4.2.6.2 Performing the Experiment . . . . . . . . . . . . . . . . . . . . . 18

4.2.7 Flow lines of a Drainage Ditch . . . . . . . . . . . . . . . . . . . . . . 19

5 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.1 Symbols and Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5.2 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215.3 Technical Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

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1 Introduction

The HM 169 Drainage & Seepage Tankis used

to illustrate two-dimensional flow through perme-

able substances. Different models can be placed

in the transparent work area.

The unit is equipped with a pump and a tank and

can be operated independent of the water supply.

Connection to a power supply is required.

A contrast medium (dye) is injected into the (sand)

bed through fine injection nozzles. The transparent

front panel of the work area is ideal for viewing the

streamlines that are produced. The pressure dis-

tribution can also be determined via the 14 pres-

sure measuring points and manometer board.

The unit includes two adjustable overflow tubes, a

water tank and two filter plates, which are used to

keep the sections of the work area free from sand,

soil, etc.

A pile retaining wall is included as a model. It is

also possible to determine the pressure distribu-

tion at a model foundation and bulkhead.

The unit is designed for use by students in practicallaboratory experiments as well as for demonstra-

tion purposes.

Following subjects can be examined using this unit:

- Illustration of flow using permeable substances

- Streamlines under a pile retaining wall

- Streamlines through an earth bank

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- Drainage to an open ditch

- Determination of the pressure distribution at a

foundation

- Determination of the pressure distribution at a

bulkhead

- Determination of flow field in permeable media

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1 Introduction 2

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2 Description of the Unit

2.1 Design

7 11 10 9 14 8 11 2

6

16

12 5 4 15 13 3 1 6

Bottomof pan:Coverfor repla-cingsand

Fig. 2.1 Design

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The contrast medium flows from the supply tank

(9) through hoses and into the three injection lan-

ces (10). The flow can be controlled with the con-

trast medium valves (14).

The tank (2) can be emptied using the discharge

cock (12). A drainage valve (13) is also provided

for the pan.

The sand can be easily replaced by unscrewing

the cover on the bottom of the pan. Ensure that the

sand is collected in a suitable container.

2.3 Start-up

- Place unit on a flat, even, stable surface.

- Engage the roller brakes.

- Fill tank (3) with clean, clear freshwater (ca. 90

liter).

Before filling, ensure that the discharge cock

(12) is shut.Replace tank cover.

- Ensure that the drainage valve (13) is shut.

- Connect power supply to the pump (4).

(230 V DC / 50 Hz)

2.4 Operation

2.4.1 Filling with Sand

- Use the filter plates (11) to separate the areas

that are not to be filled with sand.

The unit is equipped with slides that can be

moved on tracks. The filter plates can be clam-

ped in place and can be positioned anywhere

within the work area.

- Fill pan with sand.

Use washed sand. The grain size should not

exceed 1 mm.

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2.4.2 Adjust Water Supply and Overflow

- Adjust overflow tubes (6).

The overflow tubes can be moved in their

tracks. If they become difficult or stiff to move,

turn while pulling.

- Set the pump (4) with the pump switch (5).

- Adjust flow rate with the inlet valve (15).

2.4.3 Filling and Injecting the Dye

For good results, dilute the dye (included) at a ratio

of 1:5.

- Shut contrast medium valves (14).

- Fill supply tank (9) 2/3 full with diluted dye.

- Insert injection lances (10) about 10 mm into

the sand bed.

The contrast medium should be injected into

the sand as close as possible to the transparent

glass plate.

The injection lances are held in riders and can

be fixed in place if required.

- Open the contrast medium valves (14) slightly

and wait until dye flows from the lances.

If no acceptable streamlines should form, adjust

valve openings (14). If required, it is also possible

to adjust the height of the supply tank (9).

Depending on the type of sand, the formation ofstreamlines can take a few minutes to several

hours.

149

10

Rider

Sand

Injectionlance

Glass plate

Fig. 2.2 Supply tank with injectionlances

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2.4.4 Maintenance and Care

- Thought the dye can be washed from textiles,

it adheres to aluminium, steel and plastics.

Remove dye from the unit as quickly as possi-

ble with water.

- Flush injection lances with clear water after use:

Remove dye from the supply tank and fill with

fresh water. Allow water to flow through the

lances until the liquid runs clear.

- After operation has ended, drain water from thepan (2).

Pull the overflow tubes (6) downwards until the

top of the tubes is approximately at the same

level as the base of the pan. Caution! Do not

remove overflow tubes completely from

their guides.

Connect hose to the drainage valve (13) and

open valve. Collect water in a suitable container.

- To avoid the formation of algae, replace water

in the tank (3) regularly.

The tank water can be drained via the discharge

cock (12).

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3 Safety Instructions

3.1 Safety

- DANGER! Protect pump and electrical lines

from spraying water!

Risk of electrical shock.

3.2 Risk for Unit and Function

- ATTENTION! Operate unit only with super-

vision!

Possible leaks can result in the risk of overflow.

- ATTENTION! Secure unit against rolling!

Engage roller brakes.

- ATTENTION! Never operate pump without

water!

Dry running can result in damage to the pump.

- ATTENTION! Fill tank with clean water only!

Ensure that no foreign matter can enter the

tank!

Foreign matter can enter the pump and cause

damage.

- ATTENTION! Do not use sand with grainsize less than 1 mm! Ensure that no sand

can enter the tank!

- ATTENTION! Store the water-filled test unit

in frost-free area!

- ATTENTION! Clean painted parts only with

solvent-free cleaning agents!

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The test unit is designed for operation in dry,

covered areas.

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4 Theoretical Principles

4.1 Definitions

4.1.1 Flow

The Flow of water through porous media is de-

pendent on the following influencing variables:

Cross-section of flow

Permeability coefficient

Slope

Length of the path of flow.

The Flow is expressed mathematically as follows:

Q=AKh

L(4.1)

Q: Flow in m3/h

A: Cross-section in m2

K: Permeability coefficient in m3/(m2h)

h: Slope in m

L: Length of path of flow in m

The permeability coefficient is dependent on the

type of sand used.

4.1.2 Flow Field, Flow Lines, Equipotential Lines

A flow field is the graphic illustration of a (water)flow through permeable media such as sand. It

provides information on the seepage of water

through dams and retaining walls, or about the

pressure affecting the dam bottom, etc.

The path taken by a water particle during seepage

through a porous medium is called a flow line.

DL

Dh

A

Supply

Discharge

Cross-section of flow

Piezo tubes

Sand-filled cylinder

Fig. 4.1 Flow through a permeablemedium

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The prerequisite for the flow from one location to

another is a slope between the two locations. The

higher water level obtains a potential energy that

is converted into kinetic energy by the flow of water

to the lower level. The sand hinders the flow of

water, which can be recorded as energy opposite

to the water flow (similar to friction, in mechanics).

According to Fig. 4.2, water seeps from Basin I to

Basin II beneath a pile retaining wall, with each

water particle taking a different path. Assuming

that the water level and the bottom of the basins

are horizontal, each water particle has the same

potential when entering at the bottom. This also

applies when reaching the bottom of Basin II.

Two flow lines, A and B, are shown in Fig. 4.2. The

lines that join two points with the same potential on

different flow lines are called equipotential lines.

The equipotential lines always run vertically to the

streamlines. According to Fig. 4.2 the points a1 and

h

I II

a1 b1 b2 a2

A

B

ax

bx

ay

by

Equipotential lines

Flow

lines

dmds

dF

dF

Fig. 4.2 Flow field under a retaining wall

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b1 have the same potentials. The same applies to

ax, bx and ay, by and a2, b2.

The graphic illustration of flow lines and equipoten-

tial lines is called the flow field.

The fact that the equipotential lines and the stre-

amlines intersect at a right angle is an important

aspect and can be explained visually as follows:

Just as the course of a river normally takes the

steepest route, water flows between equipotential

lines along the so-called maximum gradients. The

gradient is defined as the potential difference be-

tween two equipotential lines divided by the inter-

val between the two lines. In the case of two

parallel lines the maximum gradient would be on a

line that is vertical to the two equipotential lines,

that is, at the shortest distance. An infinite number

of adjacent but non-parallel equipotential lines

would result in flow lines as shown in Fig. 4.2.

4.1.3 Seepage Flow

A specific quantity of water which flow from one

location to another per time unit and length is

called seepage flow (mathematically designated

as Q, cf. Chap. 4.1.1). The quantity of water that

seeps through the area (limited by the streamlines

a1a2 and b1b2) also passes through the area dF

(which is limited by axay and bxby). The seepage

flow per length unit is designated here as dq. This

results in the following (cf. Fig. 4.2):

dq=Kdmdhds

(4.2)

The decrease in potential dh between two equipo-

tential lines is the only unknown value in this case.

If the equipotential lines are selected so that the

surface area dF approximates a square, the di-

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stance dm is approximately the same as ds. This

results in the following:

dq=Kdh (4.3)

The following applies to dF:

dq =Kdh (4.4)

The Flow through dF must be as great as through dF:

dq = dq (4.5)

As a consequence of (4.3) and (4.4) it is:

dh = dh (4.6)

The strips between two specific flow lines is divi-

ded into n number of "rectangles", where the cor-

ners form right angles and the sides are

approximately equal. The values for dh must all be

equal. Dividing h by n results in dh:

dh=h

n(4.7)

The division into squares is advantageous. It is

also possible to divide them into "normal" rectan-

gles if they all have the same dm/ds ratio. When

dm/ds = c this results in the following:

dq=Kcdh (4.8)

dq =Kcdh (4.9)

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4.2 Experiments

4.2.1 Streamlines of a Pile Retaining Wall

4.2.1.1 Preparing the Experiment

- Fill supply tank with contrast medium

- Position filter plates near the overflow tubes

(Fig. 4.3).

- Place the model of the retaining wall into the

center of the pan. This divides the pan into aleft and right basin.

The model is attached to the pan with a clam-

ping device, similar to the filter plates. There

should be an interval of about 120 mm between

the base of the pan and the bottom of the

retaining wall.

- Push overflow tubes upwards completely.

- Fill the pan with sand.Approximately 300 mm of sand should fill the

pan (measured from the base).

- Adjust the left overflow tube so that the top is

about 100 mm below the bottom of the pan.

- Adjust the right overflow tube so that the top is

about 20 mm above the surface of the sand.

- Fasten the inlet to the pan to the right of the

retaining wall.

InletRetaining wall

Overflow tube

Filter plate

Fig. 4.3 Set-up: retaining wall

Clamping

device

Retaining wall

Fig. 4.4 Attachment of model

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4.2.1.2 Performing the Experiment

- Start pump and let water flow slowly into the

right basin (control with inlet valve).

- When the right basin is full (water is running

into the overflow tube), fill the left basin.

- Adjust the incoming flow so that the water level

remains constant.

- Smooth any uneven areas on the base bed.

- Insert the injection lances about 10 mm into the

sand bed.

- Open the contrast medium valve.

If the forming streamlines are too wide, the

valves must be shut slightly. If too little or no

dye is released, the valves must be opened.

4.2.2 Determining a Flow Field

The flow lines from the experiment described abo-

ve are used to determine a flow field.

- Attach transparent paper to the glass.

- Use a pen to trace the outline of the sand bed

and the flow lines on the paper.

- Draw rectangles between the streamline pairs.

- From these rectangles, develop the equipoten-

tial lines over the entire flow field. The equipo-

tential lines must intersect the flow lines at right

angles.

- Interpolate additional flow lines between the

experimental flow lines so that a rectangular

network is created with the equipotential lines.

The seepage rate dq can be determined using the

equations from Chap. 4.1.3.

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4.2.3 Pressure distribution with a retaining wall

The pressure distribution can be illustrated using

the manometer board. The 14 pressure measuring

points are distributed and numbered evenly along

the length of the pan. The example of the retaining

wall shows clearly that the pressure decreases in

the direction of flow.

4.2.4 Stream Lines through an Earth Bank

An earth bank is set up in the pan according to Fig.

4.5. The injection lances are inserted in the side

facing the higher water level. The top injection

lance should be positioned as closely as possible

to the water level.

Flow lines similar to Fig. 4.6 will form. The topmost

flow line represents the water level in the dam.

Care must be taken to ensure that every flow line

is vertical with respect to the surface facing thehigh water (equipotential line).

4.2.5 Pressure Distribution on a Foundation

The preparation of the experiment is similar to that

described in Chap. 4.2.1. In addition, the model

"foundation pressure" is then also included in the

experiment set-up according to Fig. 4.6. The top

of the right overflow tube should be at the samelevel as the top of the foundation panel. The model

must lie horizontally on the sand bed and be placed

directly along the retaining wall. Any gaps between

the retaining wall and "foundation" must be sealed

with a thin rubber mat.

It is possible to illustrate the distribution of pressure

at the foundation using the model tubes. The retai-

ning wall is then set deeper, which shows that the

pressure on the foundation is decreasing.

Fig. 4.5 Streamlines through anearth bank

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Lengthening or shortening the streamlines has a

direct influence on the distribution of pressure.

This is often used to reduce pressure on the foun-

dation structures.

4.2.6 Pressure on a Bulkhead

4.2.6.1 Preparing the Experiment

The experiment is set up according to Fig. 4.7.

- Fasten the model "bulkhead" in the centre of

the pan.An interval of about 90 mm should be maintai-

ned between the base of the pan and the

bulkhead.

- Fill the space between the two filter plates with

sand according to Fig. 4.7.

The surface of the sand bed should be about

100 mm below the top of the pan.

Retaining wall position 1

Retaining wall position 2

Pressure distribution 1

Model:foundation pressure

Pressure distribution 2

Flow lines 1

Flow lines 2

Fig. 4.6 Foundation pressure with various streamlines

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- Adjust the left overflow tube.

The top of the overflow tube should be about

50 mm below the surface of the sand.

- Adjust the right overflow tube.

The top of the tube should be about 10 mm

above the base of the pan.

4.2.6.2 Performing the Experiment

- Slowly fill the left basin with water.

The distribution of pressure at the bulkhead is

illustrated via the water level in the tubes.

Pressurewithout drai-nage

Pressurewith drai-nage

Pressurewith drai-nage

Model: bulkhead

Filter plate

Sand bed

Filter plate

Fig. 4.7 Experiment set-up: bulkhead

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4.2.7 Flow lines of a Drainage Ditch

The experiment is set up according to Fig. 4.8.

Flow lines will form similar to Fig. 4.8.

Filter plates

Sand bed

Flow lines

Fig. 4.8 Flow lines in a drainage ditch03/99



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5 Appendix

5.1 Symbols and Units

A Flow cross-section m3

c Coefficient

dF, dF Surface area m2

dh, dh Potential decrease m

dm, ds Length m

dq, dq Seepage flowm

3

mh

h Height m

K Permeability coefficientm

3

m2h

Q Throughput m3/h

h Slope m

L Length of path of flow m

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5.2 Models

Bulkhead Pile retaining

Fundament

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5.3 Technical Data

Main dimensions (l x w x h):

1600 x 670 x 1875 mm

Tare weight: approx. 235 kg

Power supply: 230 V~ / 50 Hz

Alternatives optional, see type plate

Inner dimensions of pan (l x w x h):1480 x 100 x 616 mm

Tank volume:

96 Ltr.

Usable pan volume:

approx. 82 Ltr.

Centrifugal pump:

maximum flow rate: 34 Ltr./min

maximum pumping head: 34 m

Volume capacity of supply tank:

0.5 Ltr.

Designed for contrast medium:

dye

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