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Braja M Das, Principal of Geotechnical Engineering, fourth
edition, PWS Publishing Compan 1998 BostonCompany, 1998, Boston
Muni Budu, Soil Mechanics and Foundations, 2nd edition, John
Wiley & Sons, 2007, USA
R.F. Craig, Soil Mechanics, (English & terjemahanProf.Dr.Ir
Budi S Supandji)
Cernica, J.N., Soil Mechanics, John Wiley & Sons,
19951995
Holtz, R.D., Kovacs, W.D., An introduction to Geotechnical
Engineering, Prentice Hall, N.J., 1981
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hLhi
BA hhh
3
ikv v = discharge velocityk = hydraulic conductivityi =
hydraulic gradient
Avq
v = discharge velocityk = hydraulic conductivityi = hydraulic
gradient
q = flow rateA = cross sectional area
4
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Definisi dari flow net Equipotensial line berpotongan
tegak lurus dengan flow linetegak lurus dengan flow line Flow
elemen berbentuk bujur
sangkar atau persegi panjang
ab dan de adalah garis equipotensial ab dan de adalah garis
equipotensial Flow line yg memotong nya tegak lurus
boundary dr impervious layer fg adalah flow line line acd
Equipotensial line yg memotong acd dan fg berupa bujur sangkar
atau persegi panjang
1 Square
Dari Hk Darcy v=k i A maka
Potensial drop
dan dimana H= perbedaan head antara upstream dan down streamNd =
jumlah dr potensial drop
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2 Rectangular
atau
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The boundary conditions must be satisfied Flow lines must
intersect equipotential lines at right
anglesangles The area between flow lines and equipotential
lines
must be curvilinear squares. A curvilinear square has the
property that an inscribed circle can be drawn to touch each side
of the square
The quantity of flow through each flow channel is constant
The head loss between each consecutive i t ti l li i t
tequipotential line is constant
A flow line cannot intersect another flow line An equipotential
line cannot intersect another flow
line
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draw the system in scale
AB and CD are equipotentials because theequipotentials because
the total head is constant
from point B, water must flow down the upstream face BE, round
the tip E and up the downstream face EC.
FG and BEC are flow lines because water from point F must flow
along the impermeable surface FG
try to sketch the flow net
the intersection of flow lines form curvilinear squares
Nf : number of flow Nd : number of equipotential dropsd u be o
equ pote t a d ops h : head loss; H : total head loss q : flow
rate
Hh Akiq
dNh
d
f
NN
Hk
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In anisotropic condition, kx ky
thus, the coefficient of permeability of the transformed section
(k) :
k = (kx ky)
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Basic Parabola
Parabola is a locus of points that has a same distance from a
fixed point (focus), and a line (directrix)
Horizontal discharge faceP
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Drawing parabola1. GS = 0.3 HS2. F as the focus of basic
parabola3. GF = GI4. IE as directrix5. 0E = 0F = 0.5 EF6. FL =
LM
By coordinatesy2=2Px
Sloping discharge face
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Downstream correction to basic parabola
aa
AD
KM
basic parabola
filter
basic parabola
filter
a
a
KM
DA
30 60 90 120 150 180
a/a 0.36 0.32 0.26 0.18 0.10 0
The two layers can be considered as a single
H1 k1z
homogeneous anisotropic layer (H1+H2)with coeff. of permeability
kx and kz
H2 k2x
21
2211
HHkHkHk x
2
2
1
121 /)( k
HkHHHk y
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Titik P berjarak Zp dibawah datum, berarti tinggielevasinya
Zp.Ti i i l di i ik P Tinggi energi total di titik P:
hp = {nd/Nd} x h ; h = { h/ Nd }
Tekanan air pori pada titik P dapat dihitung dariteorema
Bernoulli:
nd : nomor titik garis ekipotensial
Up = x { hp (- Zp) }= x ( hp + Zp)
Nd : jumlah bidang ekipotensial total
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