MEKANIKA TANAH I
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MEKANIKA TANAH I PERTEMUAN II PERMEABILITAS TANAH Oleh : Arwan Apriyono PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED TAHUN 2011
description
MEKANIKA TANAH I. PERTEMUAN II PERMEABILITAS TANAH. Oleh : Arwan Apriyono. PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED TAHUN 2011. I NTRODUCTION. What is permeability?. - PowerPoint PPT Presentation
Transcript of MEKANIKA TANAH I
MEKANIKA TANAH IPERTEMUAN II
PERMEABILITAS TANAH
Oleh :Arwan Apriyono
PROGRAM STUDI TEKNIK SIPIL JURUSAN TEKNIK FAKULTAS SAINS DAN TEKNIK UNSOED
TAHUN 2011
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WHAT IS PERMEABILITY?
A measure of how easily a fluid (e.g., water) can pass through a porous medium (e.g., soils)
Loose soil
- easy to flow
- high permeability
Dense soil
- difficult to flow
- low permeability
water
INTRODUCTION
INTRODUCTION
Hukum dalam Konsep Permebilitas
Hukum Darcy(Aliran Air pada Media
Porous)
Hukum Bernoulli (Aliran Gas dan
Fluida)
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BERNOULLI’S EQUATION
1. Kinetic energy
datum
z
fluid particle
The energy of a fluid particle is made of:
2. Strain energy
3. Potential energy
- due to velocity
- due to pressure
- due to elevation (z) with respect to a datum
BERNOULLI’S EQUATION
Total head =
Expressing energy in unit of length:
Velocity head +
Pressure head
+Elevation head
BERNOULLI’S EQUATION
Total head =
For flow through soils, velocity (and thus velocity head) is very small. Therefore,
Velocity head +
Pressure head
+Elevation head
0
Total head = Pressure head + Elevation head
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Pressure head = pore water pressure/w
Elevation head = height above the selected datum
At any point within the flow regime:
NOTES
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If flow is from A to B, total head is higher at A than at B.
water
AB
Energy is dissipated in overcoming the soil resistance and hence is the head loss.
NOTES
BA hhh
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Hydraulic gradient (i) between A and B is the total head loss per unit length.
water
AB
AB
BA
l
hhi
length AB, along the stream line
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DARCY’S LAW
Velocity (v) of flow is proportional to the hydraulic gradient (i) – Darcy (1856)
v = k i
Permeability
• or hydraulic conductivity
• unit of velocity (cm/s)
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PERMEABILITY VALUES (CM/S)
10-310-6 100
clays gravelssandssilts
CoarseFines
Bina Nusantara
CONSTANT HEAD (TINGGI KONSTAN) 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
INTRODUCTION
Bina Nusantara
EXAMPLE 1
Question :Find the permeability coefficient of sand in ft/min
q = 1 ft3/hr
TERIMA KASIH
