241309538 Falling Head Permeability Test Lab Report

7/23/2019 241309538 Falling Head Permeability Test Lab Report

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TABLE OF CONTENTS

1.0 OBJECTIVES

2.0 THEORY BACKGROUND3.0 EQUIPMENTS4.0 PROCEDURES5.0 RESULTS.0 SAMPLE CALCULATIONS!.0 DISCUSSION".0 CONCLUSION


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1.0 OBJECTIVE

1. To determine permeability of soils of intermediate and low permeability

(less than 10-4m/s), i.e. silts and clays.

2. TO describe the eneral accepted practice to determine the coefficient of

permeability of silts and clays.

!. To identify the relationship between permeability and pore si"e of the fine

rained soils.

4. To meas#re the coefficient of permeability of silts and clays.


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2.0 THEORY BACKGROUND

$n the fallin head test a relati%ely short sample is connected to a standpipe

which pro%ides both the head of water and the means of meas#rin the antity

of water flowin thro#h the sample. 'e%eral standpipes of different diameters

are normally a%ailable from which can be selected the diameter most s#itable for

the type of material bein tested.

$n permeability tests on clays, m#ch hiher hydra#lic radients than are normally

#sed with sands can be applied, and are often necessary to ind#ce any

meas#rable flow. The cohesion of clays pro%ides resistance to fail#re by pipin at

radients of #p to se%eral h#ndred, e%en #nder ite low confinin or s#rchare

press#res. ispersi%e clays howe%er are %ery s#sceptible to erosion at m#ch

lower radient.

The fallin head principle can be applied to an #ndist#rbed sample in a samplin

t#be and to a sample in an oedometer consolidation cell. The eation #sed in

determine the permeability of fine rained soils is i%en in &n (1).

=2

1

12

log)(

,h

h

ttA

aLktyPermeabili e ###..E$% &1'

The time difference (t2-t1) can be e*pressed as the elapsed time, t (min#tes). The

heihts h1and h2and the lenth, + are e*pressed in millimetres, and the areas

and a in sare millimetres. &n (1) then becomes &n (2).

)/(log60

,2

1 smmh

h

tAx

aLktyPermeabili e

= ###..E$% &2'


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To con%ert nat#ral loarithms to ordinary (base 10) loarithms, m#ltiply by 2.!0!.

$f is ep*ressed in m/s, the abo%e eation becomes &n (!).

)/(log601000

303.2,

2

110 sm

h

h

txAx

aLktyPermeabili

= ###..E$% &3'

here a area of cross-section of standpipe

t#be,

area of cross section of sample

h1 heihts of water abo%e dat#m in

standpipe at time t1

h2 heihts of water abo%e dat#m instandpipe at time t2

+ heihts of sample

t elapsed time in min#tes


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3.0 EQUIPMENTS

1. ermeameter cell, comprisin

ell body, with c#ttin ede (core c#tter), 100 mm diameter and 1!0 mm

lon.

erforated base plate with strainin rods and win n#ts.

Top clampin plate.

onnectin t#be and fittins.

3i#re 1 ompaction permeameter

(o#rtesy of + $nternational, 200)


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4.0 PROCEDURES

1. ssemble apparat#s,

a. The apparat#s is set #p as shown in 3i#re 2. The %ol#me of water

passin thro#h a sample of low permeability is ite small and a

contin#o#s s#pply of de-aired water is not necessary, b#t the

reser%oir s#pplyin the de-airin tan sho#ld be filled with distilled

or de-ionised water

2. alibrate manometer t#bes,

a. The areas of cross-section of the three manometer t#bes sho#ld

be determined as follows for each t#be

i. The t#be is filled with water #p to a nown mar near the

top of the scale, obser%ed to the nearest mm.

ii. ater is r#noff from the t#be into a weihted beaer, #ntil

the le%el in the t#be has fallen by abo#t 500mm or more.

iii. The new water le%el is read on the scale, to the nearest

mm.

i%. The beaer containin water from the t#be (weihins

sho#ld be to the nearest 0.01) is weihted.%. The diameter of the manometer can be calc#lated as

follows

21

1000,

hh

madiameter w

= mm2

$f mw mass of water (),

h1 initial le%el in t#be (mm),

h2 final le%el in t#be (mm),

area of cross-section of t#be (mm2)

%i. The meas#rements is repeated two or three times for each

t#be, and a%erae the res#lts.%ii.

!. repare cell,


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a. The cell is dismantled.

b. The cell body is checed clean and dry, and weihted to the

nearest 0.1.

c. The mean internal diameter () and lenth (+) is meas#red to the

nearest 0.5mm.

4. repare sample,

a. 6ndist#rbed sample can be taen by means of core c#tter.

b. The sample is mae s#re that ha%e a tiht fit in the body and there

are no ca%ities aro#nd the perimeter thro#h which water co#ld

pass.

5. ssemble cell

7. onnect cell

. 'at#rate and de-air sample

8. 3ill manometer system

9. :#n test

a. 'crew clip at inlet is opened to allow water to flow down thro#h

the sample, and the water le%el is obser%ed in the standpipe.

b. s soon as it reaches the le%el h1, the timer cloc is started.

c. The time is obser%ed and recored when the le%el reaches h!, andwhen it reaches h2, then the cloc is stopped.

d. 'crew clip at inlet is closed.

10.:epeat test

11. alc#late permeability

12.:eport res#lt


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The time will be taen when the le%el reach at 900mm,800mm,00mm

The le%el of heiht abo%e dat#m are be taen #sin r#ler

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241309538 Falling Head Permeability Test Lab Report