Permeability is a measure of the ease of passage of liquids or gases or specific chemicals through the material. Permeability is determined by applying a head and determining the depth of penetration or the amount of liquid or gas passing through the sample

1. Presentation
On
“Permeability
of Soil”
Shivani Negi (50321) Chetan Chauhan (50325)
Rachna Negi (50340) Dipesh Singh Chuphal (50599)
Under the guidance of : Dr. Ajit Kumar

2. Introduction
 Soil permeability is the property of the soil to transmit
water and air through the soil.
 It is usually expressed either as a permeability rate in
centimetres per hour (cm/h), millimetres per hour
(mm/h), or centimetres per day (cm/d), or as a coefficient
of permeability k in metres per second (m/s) or in
centimetres per second (cm/s).

3. Contents
1) Need to study permeability
2) Darcy’s law and coefficient of permeability
3) Permeability variation according to soil texture
4)Permeability variation according to soil structure
5)Methods of finding soil permeability

4. Need to study permeability:
• Settlement of foundation and buildings
• Seepage below the earth structures
• Seepage through the earth structures
• The Yield of the wells
• For designing filter in hydraulic structures in order to prevent
piping

5. Darcy’s Law and Coefficient of
Permeability:
• Darcy’s law studied the laminar flow of fluid in a
homogeneous soil profile and demonstrated that the velocity
of flow (v) is directly proportional to the hydraulic gradient
(i).
𝑣 = 𝑘𝑖
• Where k is a constant called coefficient of permeability.
• If the discharge velocity (v) is known, the discharge (q) can
be obtained as:
𝑞 = 𝑣𝐴 = 𝑘𝑖𝐴

6. Permeability variation according to
soil texture:
Usually, the finer the soil texture, the slower the permeability, as
shown below:
Soil Texture Permeability
Clayey soils Fine
From very slow to very
rapid
Loamy soils
Moderately fine
Moderately coarse
Sandy soils Coarse

7. Permeability variation according
to soil structure:
Structure may greatly modify the permeability rates shown
below, as follows:
Structure type Permeability
Platy
Greatly overlapping
From very slow to very rapid
Slightly overlapping
Blocky
Prismatic
Granular

8. Factors affecting Permeability of soil
K = (c𝐷10
2
)(
γ𝑤
µ
)(
𝑒3
1+𝑒
)(
1
𝑘𝑠𝑆𝑆𝐴2) (
1
𝑇2)A(
1
𝐵
)(
1
𝐶
)
Here,
 Allen Hazen’s equation: K = c𝐷10
2
 Loudon’s equation: log10(𝐾. 𝑆𝑆𝐴2
) = a+bη
 Kozeny Carman’s equation: K =(
γ𝑤
µ
)(
𝑒3
1+𝑒
)(
1
𝑘𝑠𝑆𝑆𝐴2) (
1
𝑇2)
 A: Degree of saturation
 B: Entrapped gases
 C: Impurities

9. Methods of finding coefficient of
permeability:
 Laboratory Methods
• Constant head permeability test
• Falling head permeability test
 Field Methods
• Pumping-out tests
• Pumping-in tests

10. Constant Head Permeability Test:
 Purpose Of Experiment:
 To determine the permeability of granular soils like sands
and gravels containing little or no silt.
 Equipment used:
 Permeability test apparatus with accessories.
 Stop watch.
 Measuring jar.

11. Constant head permeability test apparatus

12. Observation:
• k can be found from the expression
k =
q𝐿
Aℎ
or k =
Q𝐿
tAh
• Data and test results of constant head test
• Length of specimen (L) = 127 mm
• Area of specimen (A) = 7,854 mm2
• Volume of specimen (V) = 9,97,458 mm3
• Specific gravity of soil (G) = 2.65

13. Observation table:
S.no. Time, t
(s)
Head, h
(mm)
Hydrauli
c
gradient,
𝐡
𝐋
Quantity,
Q3
(mm3)
𝐪 =
𝐐
𝐭
(mm3/s)
kr
(mm/s)
1. 150 300 2.36 32,400 214.8 0.0116
2. 300 300 2.36 66,000 217.0 0.0117
3. 450 300 2.36 96,300 216.5 0.0117
Average: 0.0117

14. FALLING HEAD PERMEABILTY
TEST:
 Purpose of experiment:
• To determine the permeability of fine grained soils with
intermediate and low permeability such as silts and clays.
 Equipment used:
• Permeameter with its accessories:
• Standard soil specimen
• Deaired water
• Balance to weigh up to 1 g
• I.S sieves 4.75 mm and 2 mm

15. Falling head test apparatus

16. Formula Used:
k =
2.30aL
At
log10
h1
h2
• t = time
• L = Length of fine soil
• A = cross section area of soil
• a = cross section area of tube
• k = Coefficient of permeability

17. Observation Table:
Sl. no. Initial head, h1
(mm)
Final head, h2
(mm)
Time, t
(seconds) 𝐥𝐨𝐠𝟏𝟎
𝐡𝟏
𝐡𝟐
kT
(mm/s)
1. 1,200 550 122 0.339 0.0117
2. 1,200 400 173 0.477 0.0116
3. 1,200 250 244 0.681 0.0118
Average: 0.0117

18. Fields Methods:
 Pumping-out tests
 Unconfined aquifer
 Confined aquifer
 Pumping-in tests
 Open-end test
 Packer test

19. Pumping-Out Test:
• In the pumping-out test, a tubewell is drilled to penetrate
the entire thickness of the aquifer up to the underlying
impervious stratum.
• The tubewell is perforated in the aquifer portion so that the
water can enter the well .
• The perforated tube is surrounded by screens to check the
flow of soil particles into the well.

20. Unconfined Aquifer:
𝑘 =
𝑞
𝜋(𝑧2
2 − 𝑧1
2)
log𝑒
𝑟2
𝑟1

21. Confined Aquifer:
𝑘 =
𝑞
2𝜋𝑏(𝑧2 − 𝑧1)
log𝑒
𝑟2
𝑟1

22. Pumping-In Tests:
• Pumping-in tests are suitable for low permeability and thin
strata soil.
• The test gives the permeability of soil at the bottom of the
bore hole and is more economical than the pumping-out
test.

23. Open-End Test:
• In this test, a open end pipe is inserted into the soil stratum
and the soil in the pipe is removed.
• Clean water at a temperature slightly higher than that of
groundwater is added under some pressure.
• Head is kept constant.
• 𝑘 =
𝑞
5.5𝑟ℎ
• h = head difference.
• r = inner radius of casing
• q = constant rate of flow
Open-End test setup

24. Packer Test:
• In Packer test , the water flows out through , the sides of a
hole enclosed between packers.
• Packer tests are more commonly used for testing of rocks
than of soils.
• r = radius of hole
• L= length of perforated
pipe
Packer’s test above and below GWT
𝑘 =
𝑞
2π𝐿𝐻
log𝑒
𝐿
𝑟

25. THANK
YOU