consolidation test obe

Department of Civil Engineering University of Moratuwa

Module - CE 2132 Soil Mechanics and Geology-11Assignment Consolidation Test Marks 10%Learning Outcome

Ability to conduct a laboratory consolidation test Ability to evaluate coefficient of consolidation and coefficient of

volume compressibility of an undisturbed soil sample Ability to interpret the consolidation test data Ability to discuss the applications of the consolidation test in

geotechnical engineering Programme Outcomes

1. Application of knowledge of mathematics, science, and engineering 1

2. Effective communication 13. In-depth technical competence in at least one engineering

discipline 2

4. Ability to undertake problem identification, formulation and solution 2

5. Ability to utilize a systems approach to design and operational performance 2

6. Individual and team work 17. Understanding of the social, cultural, global and

environmental responsibilities of the professional engineer, and the need for sustainable development

0

8. Understanding of the principles of sustainable design and development 0

9. Understanding of professional and ethical responsibilities and commitment to them 1

10. Expectation of the need to undertake life-long learning and capacity to do so 0

0 – not covered under this 1– covered to some extent 2–covered to a greater extent 3– one of the main themes of the subject

Lecturer Dr. L. I. N. de SilvaStudent NameRegistration Number:Date of Assignment: Date Due:Initial Submission Date: Re Submission Date:

Assessed By:

Signature Date

Lecturers’ Remarks

B.Sc Engineering, Semester IV, CE 2132 – Soil Mechanics & Geology - 11 of 11


Important1. Please note that plagiarism is treated as a serious offence and therefore the work you

produce must be individual and original.2. All sources of information must be referenced using “Harvard Referencing” where

a reference list/Bibliography should be included at the end of the assignment. (You may refer the information given in http://libweb.anglia.ac.uk/referencing/harvard.htm)

3. Please note that the submission date given for the assignment (14 days after the date of performance for the laboratory session) is the final date that you can submit the assignment. If the given submission date is a public holiday, redefined submission deadline will be at 1300 hr of the immediate following working day. Late submissions will be graded lower.

4. Assignments returned to students for corrections must be re-submitted within 10 days

5. Failure to re-submit the previously marked assignment with the re-submitted assignment will mean that results cannot be released for the respective unit.

Plagiarism

Although research and discussion form an essential part of the assignment, deliberate copying of the work of others or unacknowledged copying from printed or electronic sources is NOT permitted. Disciplinary actions will be taken against those who are found guilty of plagiarism. Signing of this sheet is required to indicate your compliance with the above regulations.

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CONSOLIDATION TEST

SOIL MECHANICS


SOIL MECHANICS LABORATORYDEPARTMENT OF CIVIL ENGINEERINGUNIVERSITY OF MORATUWASRI LANKA


CONSOLIDATION TEST

Consolidation is defined as the reduction of the volume of a soil due to the expulsion of

water. This will be accompanied by the dissipation of pore water pressures.

A laboratory consolidation test is performed on an undisturbed sample of a cohesive soil to

determine its compressibility characteristics. The soil sample is assumed to be representing

a soil layer in the ground.

A conventional consolidation test is conducted over a number of load increments. The

number of load increments should cover the stress range from the initial stress state of the

soil to the final stress state the soil layer is expected to experience due to the proposed

construction.

Increments in a conventional consolidation test are generally of 24 hr duration and the load

is doubled in the successive increment.

In this practical class one load increment of a multi increment consolidation test is

conducted and the data will be analysed to obtain the compressibility characteristics of the

soil.

The compressibility characteristics of the soil are;

(a). Parameters needed to estimate the amount of consolidation settlement

(b). Parameters needed to estimate the rate of consolidation settlement in the field.

Using the data from a single load increment of the test, only the coefficient of volume

compressibility mv can be estimated. Data from all the load increments should be combined

to draw the e vs log σ graph and to obtain the compression index C c - the other parameter

used to estimate the consolidation settlement.

The rate of consolidation settlement is estimated using the Coefficient of consolidation Cv.

This parameter is determined for each load increment in the test. In this laboratory

assignment, the coefficient of consolidation should be estimated using two methods - the

root time method (Taylor's method) and the log (time) method - Casagrande's method.



Course work report - Important points to remember

1. Outline the objectives of the test

2. List the equipment used in the test

3. Draw a diagram of the apparatus

4. Describe the test procedure in your own words

5. Enter the observations in the sheets provided

6. Carry out the computations, draw the necessary graphs in the sheets provided and

estimate

(a). The coefficient of volume compressibility for the load increment

(b). The coefficient of consolidation for the increment by both the root time

method and the log (time) method.

7. Discuss the importance and relevance of the test, the parameters obtained,

shortcoming and possible ways of improvement.



Laboratory Consolidation Test and Analysis

Data obtained from one increment in a conventiional multi increment Consolidation

Test

Sample Diameter (mm) = 50.00

Initial Sample tickness (mm) = 20.00*

Dial gauge reading at the stat of the test (mm) = 0.000

Dial gauge reading at the stat of the = 3.744

current increment (mm)

Initial Moisture content of the sample % = 43.43

Specific gravity of the particles = 2.20

Current load increment is from 60 kN/m2 to 120 kN/m2

Date Time Time

Elapsed (min)

Root Time

(min 1/2 )

Dial Reading Dial Reading

(mm)

Settlement (mm) Major Minor

26/06/2009 2:00 PM 0.00 0.00 3.6 72 3.744 0.000

0.25 0.50 3.8 28 3.856 0.112

0.50 0.71 3.8 42 3.884. 0.140

1.00 1.00 3.8 62 3.924 0.180

2.00 1.41 3.8 94 3.988 0.244

4.00 2.00 4.0 38 4.076 0.332

8.00 2.83 4.0 94 4.188 0.444

15.00 3.87 4.2 44 4.288 0.544

30.00 5.48 4.2 84 4.368 0.624

60.00 7.75 4.4 6 4.412 0.668

120.00 10.95 4.4 21 4.442 0.698

1440.00 37.95 4.4 58 4.516 0.772

* Sample thickness is 20 mm at the start when the load is 0 kN/m2. At the beginning of the

load increment 60 – 120 kN/m2, sample has already settled 3.744 mm and the sample

thickness is 16.256 mm.




x 0.15x



x

x

δ0

δ100

δ50

t50


Specimen Calculations

Coefficient of Volume Compressibility(mv)

= 7.91 x 10-4 m2/kN

Coefficient of Consolidation (Cv)

a) By the Square Root Time (Taylor’s) Method

= 1.84 m2/year

b) By the Log (Time) – Casagrande’s Method

= 0.35 mm

= 1.46 m2/year

Marking Scheme:



Measurements 35%: Precision, ReliabilityCalculations & Results 25%: Accuracy, Methodology, PresentationDiscussion 25%: Content, Arrangement, PresentationCoursework Presentation 15%: Neatness, Clarity, Accordance to the format


consolidation test obe

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