FACULTY OF CIVIL ANG ENVIRONMENTAL ENGINEERING

DEPARTMENT OF INFRASTRUCTURE AND GEOMETIC

LAB GEOTECHNIC

FULL REPORT

Subject Code BFC 31703

Code & Experiment Title U4 - CONSTANT & FALLING HEAD PERMEABILITY TEST

Course Code 2 BFF

Date 26TH

APRIL 2012

Section / Group SECTION 9 / GROUP 7

Name MUHAMMAD IKHWAN BIN ZAINUDDIN (DF100018)

Members of Group 1. NUR EZRYNNA BINTI MOHD ZAINAL (DF100118)

2. MUHAMMAD HUZAIR BIN ZULKIFLI (DF100040)

3. NUR EEZRA ATHIRLIA BINTI GHAZALI (DF100147)

4. MUHAMMAD NUH BIN AHMAD ZAIRI (DF100093)

5. ZIRWATUL FAUZANA BINTI CHE JEMANI (DF100027)

Lecturer/Instructor/Tutor EN. MOHD FAIZAL BIN PAKIR

Received Date 3RD

MAY 2012

Comment by examiner

Received

STUDENT CODE OF ETHIC

(SCE)

DEPARTMENT OF INFRASTRUCTURE AND GEOMETIC

FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING

UTHM

We, hereby confess that we have prepared this report on our effort. We also admit not to receive

or give any help during the preparation of this report and pledge that everything mentioned in the

report is true.

___________________________

Student Signature

Name : MUHAMMAD IKHWAN BIN ZAINUDDIN

Matric No. : DF100018

Date : 03/05/2012

_______________________

Student Signature

Name : MUHAMMAD NUH BIN AHMAD ZAIRI

Matric No. : DF100093

Date : 03/05/2012

___________________________

Student Signature

Name : NUR EEZRA ATHIRLIA BINTI GHAZALI

Matric No. : DF100147

Date : 03/05/2012

___________________________

Student Signature

Name : MUHAMMAD HUZAIR BIN ZULKIFLI

Matric No. : DF100040

Date : 30/05/2011

___________________________

Student Signature

Name : NUR EZRYNNA BINTI MOHD ZAINAL

Matric No. : DF100118

Date : 03/05/2012

_______________________

Student Signature

Name : ZIRWATUL FAUZANA BINTI CHE JEMANI

Matric No. : DF100027

Date : 03/05/2012

PART A: CONSTANT HEAD PERMEABILITY TEST

1.0 INTRODUCTION

In the design of engineering projects, one of the most important soil properties of interest

to the soils engineer is permeability. To some degree, permeability will play a role in the design

of almost any structure. For example, the durability of concrete is related to its permeability.

In designs that make use of earthen materials (soils and rock) the permeability of these material

swill usually be of great importance.

Soils are permeable (water may flow through them) because they consist not only of solid

particles, but a network of interconnected pores. The degree to which soils are permeable

depends upon a number of factors, such as soil type, grain size

distribution and soil history. This degree of permeability is characterizedby the coefficient of per

meability.

A number of different methods for determining the coefficient of permeability for soils

exist, for soils exist, including in-situ methods and laboratory methods. In the laboratory, two

common tests are generally used to determine this soil property. These two tests are the falling

head permeability test and the constant head permeability test. Which test is used depends upon

the type of soil to be tested. For soils of high permeability (sands and gravels) a constant head

test is used. For soils of intermediate to low permeability, a falling head test is used. As

we were testing sand we used a constant head permeability test.

By carrying out the constant head permeability test we can determine the coefficients of

permeability of given sand over range of unit weights. During the test we can observe the

phenomenon of piping.

2.0 OBJECTIVE

To determine permeability of sands and gravels containing little or no silt.

3.0 LEARNING OUTCOME

a. At the end of this experiment, students are able to:

b. Describe the procedure to determine the coefficient of permeability of sands and gravels

based on ASTM D2434.

c. Identify the relationship between permeability and pore size of the coarse grained soils.

d. Measure the coefficient of permeability of sands and gravels containing little or no slit.

4.0 THEORY

The most common permeability cell (permeameter) is 75mm in diameter and is intended

for sands containing particles up to about 5mm. A larger cell, 114mm, can be used for testing

sands containing particles up to about 10mm, i.e. medium gravel size. As a general rule the ratio

of the cell diameter to the diameter of the largest size of particle in significant quantity should be

at least 12. The constant head permeability cell is intended for testing disturbed granular soils

which are recompacted into the cell, either by using a specified compactive effort, or to achieve a

certain dry density, i.e. void ratio.

In the constant head test, water is made to flow through a column of soil under the

application of a pressure difference which remains constant, i.e. under a constant head. The

amount of water passing through the soil in a known time is measured, and the permeability of

the sample is calculated by using Equation (1).

If the connections to the cell are arranged so that water flows upwards through the sample,

the critical hydraulic gradient can be determined after measuring the steady state permeability,

and the effects of instability (boiling and piping) can be observed. It is important that use only

air-free water, and measures for preventing air bubbling out of solution during these tests is very

crucial.

smAi

qktyPermeabili /, ………..Eqn (1)

Where: q = rate of flow,

A = area of sample,

i = hydraulic gradient,

= smL

hh/21

h1 - h2 = head difference between 2 reference points

L = distance between 2 reference points

5.0 TEST EQUIPMENTS

1. Constant head permeability cells, fitted with loading piston, perforated plates, flow tube

connections, piezometer nipples and connections, air bleed valve, sealing rings. Figure 1

shows permeameter cells that commonly used in laboratory testing.

Figure 1: Permeameter cells for constant head test: (a) 75mm, (b) 114mm

(Courtesy of ELE International, 2007)

6.0 PROCEDURES

1. Prepare permeameter cell,

a. Remove the top plate assembly from the cell.

b. Measure the following dimensions:

i. Mean internal diameter (D mm),

ii. Distance between centres of each set of manometer connection points

along the axis of the cell (L mm),

iii. Overall approximate internal length of cell (H1 mm),

c. Calculate the following based on measured dimensions:

i. Area of cross-section of sample, A = D2/4 mm

2

ii. Approximate mass of soil required, to fill the permeameter cell,

V = A H1/1000 cm3

iii. Approximate mass of soil required, if placed at a density Mg/m3,

mass = A H1/1000 g

2. Select sample,

a. Air-dry the soil which the test sample is to be taken.

b. Sieve the soil sample and any particles larger than 5 mm need to be removed by

sieving.

c. The material needs to be reduced by the usual riffling process to produce several

batches of samples each about equal to the mass required to fill the permeameter

cell

3. Prepare sample,

a. The sample may be placed in the permeameter cell by one of three methods:

i. Compacting by rodding,

ii. Dry pouring,

iii. Pouring through water

4. Assemble cell

a. Place a second porous disc (if one has already been used) and the second wire

gauze disc on top of the soil, followed by about 40mm thickness of glass balls or

gravel filter material,

b. The level of the top surface of the filter should be within the limits required to

accommodate the top plate,

c. Slacken the piston locking collar on the cell top, pull the piston up as far as it will

go, and re-tighten the locking collar,

d. Fit the cell top on the cell and tighten it down into place by progressively

tightening the clamping screws,

e. Release the piston locking collar and push the piston down until the perforated

plate bears on the filter material,

f. Hold it down firmly while the locking collar is re-tightened

5. Connect up cell

a. Connect the nozzle at the base of the cell to the de-aired water supply, and close

the inlet cock,

b. Connect each piezometer point that is to be used to a manometer tube and close

with a pinchcock close to the cell,

c. Connect the top outlet of the cell to the vacuum, fitted with a water trap, using

rigid plastic or thick-walled rubber tubing

d. Close the air bleed screw on the cell top

6. Saturate and de-air sample

7. Connect up for test

8. Run test

a. Turn on the supply of de-aired water to the constant head device, which be at a

low level initially,

b. Open water supply valve that connect it to the cell, and the base outlet cock

c. Allow water to flow through the sample until the conditions appear to be steady

and the water levels in the manometer tubes remain stationary

d. Adjust valve on the supply line to the constant head device so that there is a

continuous small overflow; if this is excessive, the de-aired water will be wasted.

e. To start a test run, empty the measuring cylinder and start the timer at the instant

the measuring cylinder is placed under the outlet overflow.

f. Record the clock time at which the first run is started.

g. Read the levels of the water in the manometer tubus (h1, h2, etc) and measure the

water temperature (TC) in the outlet reservoir.

h. When the level in the cylinder reaches a predetermined mark (such as 50ml or

200ml) stop the clock, record the elapsed time to the nearest half second,

9. Repeat test

a. Emtpy the cylinder, and make four to six repeat runs at about 5 minutes intervals.

10. Dismantle cell

11. Calculate results

12. Report

Figure 2: General arrangement for constant head permeability test (downward flow)

(Courtesy of ELE International, 2007)

7.0 RESULTS

Constant Head Permeability Test

Location: Geotechnic laboratory Sample no: -

Operator: - Date: 26 April 2012

Soil description:

Method of preparation: -

Sample diameter: 80.0 mm Sample length: 232 mm

Sample area, A: 5026 mm2 Sample volume: 1166 cm

3

Sample dry mass: 1925 g Sample dry density: 16.19 kN/m3

S.G. measured/assumed: 2.7 Voids ratio:

Heights above datum: inlet = 1910 mm Heights above datum: outlet = 160 mm

Manometer a: 4.11mm Manometer b: - mm Manometer c: 3.60 mm

Head difference a to c: 38 mm Distance difference: 90 mm

Flow upwards/downwards: downwards Hydraulic gradients: 0.42

Temperature: -

Reading:

Time from

start

min.

Time

interval, t

min.

Measured flow,

Q

ml

Rate of flow,

q = Q/t

ml/min t

1 k =

Ai

q

m/s

0 0 0 0 0 0

9:45 AM 1.00 390 390.00 1.00 3.079 x 10-6

9:47 AM 1.00 390 390.00 1.00 3.079 x 10-6

9:49 AM 1.00 390 390.00 1.00 3.079 x 10-6

9:51 AM 1.00 390 390.00 1.00 3.079 x 10-6

9:53 AM 1.00 390 390.00 1.00 3.079 x 10-6

9:55 AM 2.00 770 385.00 0.71 3.040 x 10-6

9:59 AM 2.00 770 385.00 0.71 3.040 x 10-6

10:02 AM 2.00 770 385.00 0.71 3.040 x 10-6

10:05 AM 2.00 770 385.00 0.71 3.040 x 10-6

10:08 AM 2.00 770 385.00 0.71 3.040 x 10-6

`10:11 AM 3.00 1150 383.33 0.58 3.027 x 10-6

10:15 AM 3.00 1150 383.33 0.58 3.027 x 10-6

10:20 AM 5.00 1900 380.00 0.45 3.000 x 10-6

Permeability, k = Ai

q

8.0 DATA ANALYSIS

Sample area,

A = 5026 mm ……………..…… from lab sheet

Sample Volume,

V = 1166 cm3…………………....from lab sheet

Hydraulic gradient,

i = head difference (a to c)

Difference distance

= 38mm

90mm

= 0.42

Rate of flow,

q1 = 390 ml/min

= 390 ml/min x 1 lit/1000ml x 1 m3/1000 lit x 1 min/60sec

= 6.500 x 10-6

m3/s

Rate of flow,

q2 = 385 ml/min

= 385 ml/min x 1 lit/1000ml x 1 m3/1000 lit x 1 min/60sec

= 6.417 x 10-6

m3/s

Rate of flow,

q3 = 380.33 ml/min

= 383.33 ml/min x 1 lit/1000ml x 1 m3/1000 lit x 1 min/60sec

= 6.389 x 10-6

m3/s

Rate of flow,

q4 = 380 ml/min

= 380 ml/min x 1 lit/1000ml x 1 m3/1000 lit x 1 min/60sec

= 6.333 x 10-6

m3/s

Permeability,

k1 =

= 6.500 x 10-6

(5.026 x 0.42)

= 3.079 x 10-6

m/s

Permeability,

k2 =

= 6.417 x 10-6

(5.026 x 0.42)

= 3.040 x 10-6

m/s

Permeability,

k3 =

= 6.389 x 10-6

(5.026 x 0.42)

= 3.027 x 10-5

m/s

Permeability,

k3 =

= 6.333 x 10-6

(5.026 x 0.42)

= 3.000 x 10-5

m/s

1/√t

q=Q

/t

9.0 QUESTIONS

1. Determine the coefficient of permeability for the given sample of soil.

Permeability, k = (3.079 x 10-6

)(5) + (3.040 x 10-6

)(5) + (3.027 x 10-6

)(2) + 3.00 x 10-6

(1)

13

= 3.965 x 10-5

13

= 3.050 x 10-6

m/s

2. Give a conclusion for this test.

From the experiment, we can know that the objective of the experiment is to

determine the permeability of sands and gravels containing little or no silt. From the

experiment that have done, we can know that the objective for this experiment was

achieved. This is because the value of permeability of sands is k = 3.050 x 10-6

m/s.

From the table of value permeability (from discussion), our result’s test we located in

categorized as fine sands. It means that the soil are using through this experiment is

fine sands.

10.0 DISCUSSION

The value of the k (permeability) that we get is 3.050 x 10-6

m/s. This value we get by

using the formulaAi

qk . Before that, we find the value Ai first and after that we get the value of

q. So, the permeability of this sample is moderate. This is because the porosity of sand and gravel

is high or moderate where by water can flows through the soil with less resistance. It can drain

water easily but hardly can retain any water.

The greater pore size of soil is more permeability then the soil with smaller pore size.

From value of k, we can clasify the type of soil that we use is silty sands or silty clays and this

types of soil is not suitable for drainage system.

Table 1 shows the range of average values for k for various soil and also indicates

potential drainage.

The coefficient of permeability may be defined as the flow velocity produced by a

hydraulic gradient of unity. The value of k is use as a measure of the resistance to flow offered by

the soil, and it is affected by several factors:

a) The porosity of the soil.

b) The particle-size distribution.

c) The shape and orientation of soil particles.

d) The degree of saturation/presence of air.

e) The type of cation and thickness of adsorbed layers associated with clay mineral.

f) The viscosity of the soil water, which varies with temperature.

11.0 CONCLUSION

As a conclusion, we get the time is found to be constant at volume of water. The time we

get is faster. This is because the permeability of the gravel soil absorbs the water is low. This

gravel soil has a large molecular space. Therefore, the water diffusion rate is low. It appears to be

a function of three factors for a constant paste amount and character: effective air void content,

effective void size and drain down. From the coefficient of permeability for the given sample of

soil value, we can say that the rate of flow the sample has get the value higher.

12.0 REFERENCE

i. http://www.slideshare.net/xakikazmi/constant-head.

ii. http://www.essayclub.com/term-papers/Constant-Head-Permeability-Test/8024.html

Soil Type k (m/s) Potential

Fine Gravel

Medium and Coarse Sands

Fine Sands

Silty Sands

Silt and Silty Sands

Silty Sands, Silty Clays

Clays

100 – 1

1 – 10-1

10-1

– 10-2

10-2

– 10-3

10-3

– 10-5

10-5 – 10

-7

10-7

– 10-9

Very Good Drainage

Very Good Drainage

Very Good Drainage

Good Drainage

Good Drainage

Poor Drainage

Practically Impervious