Constant & Falling Head Permeability Test

FACULTY OF CIVIL ANG ENVIRONMENTAL ENGINEERING DEPARTMENT OF INFRASTRUCTURE AND GEOMETIC LAB GEOTECHNIC

FULL REPORT Subject Code Code & Experiment Title Course Code Date Section / Group Name Members of Group

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BFC 31703 U4 - CONSTANT & FALLING HEAD PERMEABILITY TEST 2 BFF 26TH APRIL 2012 SECTION 9 / GROUP 7 MUHAMMAD IKHWAN BIN ZAINUDDIN (DF100018) 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) EN. MOHD FAIZAL BIN PAKIR 3RD MAY 2012

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.

Name

___________________________

___________________________

Student Signature

Student Signature

: MUHAMMAD IKHWAN BIN ZAINUDDIN

Name

: NUR EZRYNNA BINTI MOHD ZAINAL

Matric No. : DF100018

Matric No. : DF100118

Date

Date

Name

: 03/05/2012

: 03/05/2012

___________________________

___________________________

Student Signature

Student Signature

: NUR EEZRA ATHIRLIA BINTI GHAZALI

Name

: MUHAMMAD HUZAIR BIN ZULKIFLI

Matric No. : DF100147

Matric No. : DF100040

Date

Date

Name

: 03/05/2012

: 30/05/2011

_______________________

_______________________

Student Signature

Student Signature

: MUHAMMAD NUH BIN AHMAD ZAIRI

Name

: ZIRWATUL FAUZANA BINTI CHE JEMANI

Matric No. : DF100093

Matric No. : DF100027

Date

Date

: 03/05/2012

: 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.

Permeabili ty , k 

q m / s ………..Eqn (1) Ai

Where: q = rate of flow, A = area of sample, i = hydraulic gradient, =

h1  h2 m/s L

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 mm2

ii.

Approximate mass of soil required, to fill the permeameter cell, V = A H1/1000 cm3 Approximate mass of soil required, if placed at a density  Mg/m3,

iii.

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 (TC) 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 Operator: Soil description: Method of preparation: Sample diameter: 80.0 mm Sample area, A: 5026 mm2 Sample dry mass: 1925 g S.G. measured/assumed: 2.7 Heights above datum: inlet = 1910 mm Manometer a: 4.11mm Manometer b: Head difference a to c: 38 mm Flow upwards/downwards: downwards Temperature: -

Sample no: Date: 26 April 2012

Sample length: 232 mm Sample volume: 1166 cm3 Sample dry density: 16.19 kN/m3 Voids ratio: Heights above datum: outlet = 160 mm - mm Manometer c: 3.60 mm Distance difference: 90 mm Hydraulic gradients: 0.42

Reading: Time from start min. 0 9:45 AM 9:47 AM 9:49 AM 9:51 AM 9:53 AM 9:55 AM 9:59 AM 10:02 AM 10:05 AM 10:08 AM `10:11 AM 10:15 AM 10:20 AM

Time interval, t min. 0 1.00 1.00 1.00 1.00 1.00 2.00 2.00 2.00 2.00 2.00 3.00 3.00 5.00

Permeability, k =

q Ai

Measured flow, Q ml 0 390 390 390 390 390 770 770 770 770 770 1150 1150 1900

Rate of flow, q = Q/t ml/min 0 390.00 390.00 390.00 390.00 390.00 385.00 385.00 385.00 385.00 385.00 383.33 383.33 380.00

1 t 0 1.00 1.00 1.00 1.00 1.00 0.71 0.71 0.71 0.71 0.71 0.58 0.58 0.45

q Ai m/s 0 3.079 x 10-6 3.079 x 10-6 3.079 x 10-6 3.079 x 10-6 3.079 x 10-6 3.040 x 10-6 3.040 x 10-6 3.040 x 10-6 3.040 x 10-6 3.040 x 10-6 3.027 x 10-6 3.027 x 10-6 3.000 x 10-6

k=

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 formula k 

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

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. Soil Type Fine Gravel Medium and Coarse Sands Fine Sands Silty Sands Silt and Silty Sands Silty Sands, Silty Clays Clays

k (m/s) 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

Potential Very Good Drainage Very Good Drainage Very Good Drainage Good Drainage Good Drainage Poor Drainage Practically Impervious

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:

11.0

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.

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