MEKANIKA TANAH 1

PERTEMUAN IIIDetermination of Permeabilty

Coefficient

Oleh :Arwan Apriyono

PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED

TAHUN 2010

Introduction

LABORATORYCONSTANT HEAD (TINGGI KONSTAN)FALLING HEAD (TINGGI JATUH)

FIELDUNCONFINED AQUIFER (AKIFER BEBAS)CONFINED AQUIFER (AKIFER TERKEKANG )INCONSTANT WATER HEIGHT (TINGGI AIR

TIDAK TETAP)

Bina Nusantara

SUITABLE FOR SANDY SOIL, SAND OR GRAVEL WHICH HAVE BIG VOID RATIO VALUE

BASIC EQUATION :

A.h.t

Q.Lk

.tL

hk. A. A.(k.i).t A.v.t Q

Lab Test

CONSTANT HEAD (TINGGI KONSTAN)

Bina Nusantara

Lab Test

FALLING HEAD (TINGGI JATUH)

MORE ECONOMICAL FOR LONG TERM TEST Suitable For Clayed Soil that have low k BASIC EQUATION :

L

hkA

dt

dha

qqL

hkAikAq

dt

dhaq

keluarmasuk

keluar

masuk

..-

....

-

dt

dh-v

Field Test

UNCONFINED AQUIFER (AKIFER BEBAS)

Field Test

2122

1

2

1

2

21

22

.

ln.

ln

.....2..

hh

rr

Q

k

rrhhk

hrdr

dhkQ

UNCONFINED AQUIFER (AKIFER BEBAS)

Field Test

CONFINED AQUIFER (AKIFER TERKEKANG )

Field Test

CONFINED AQUIFER (AKIFER TERKEKANG )

21o

2

1

hh.h..2

rr

log.Q.3,2

k

Layered Soil

Layered Soil

Example

A pumping test was performed in a well penetrating a confined aquifer to evaluate the coefficient of permeability of the soil in the aquifer.

When equilibrium flow was reached, the following data were obtained: Equilibrium discharge of water from the well = 200

gal/min. Water levels (h1 and h2) = 15 and 19 ft at distances

from the well (r1 and r2) of 60 and 180 ft, respectively. Thickness of aquifer = 20 ft

Coefficient of permeability of the soil in the aquifer?

A nonhomogeneous soil consisting of layers of soil with different permeabilities.

Average coefficient of permeability in the horizontal direction and vertical direction

1.5 m

2.0 m

2.5 m

Kx = 1.2 x 10-3 cm/sKy = 2.4 x 10-4 cm/s

Kx = 2.8 x 10-4 cm/sKy = 3.1 x 10-5 cm/s

Kx = 5.5 x 10-5 cm/sKy = 4.7 x 10-6 cm/s

Example

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