Plastic Limit Test - 004

FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING

DEPT.OF GEOTECHNICAL AND TRANSPORTATION ENGINEERING

GEOTECHNICAL ENGINEERING LABORATORY

REPORT

SUBJECT CODE

TEST CODE & TITLE

COURSE CODETESTING DATESTUDENT NAMEGROUP

GROUP MEMBER NAMES

1.

2.

3.

4.

5.

LECTURER/ INSTRUCTOR/ TUTOR NAME

REPORT RECEIVED DATE

MARKSATTENDANCE/ DISCIPLINE & INVOLVEMENT /15%

DATA ANALYSIS /20%

RESULT /20%

DISCUSSION /25%

CONCLUSION /20%

TOTAL /100%EXAMINER COMMENT RECEIVED STAMP

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STUDENT CODE OF ETHIC(SCE)

DEPT. OF GEOTECHNICAL AND TRANSPOTATION ENGINEERING

FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING

I, hereby confess that I have prepared this report on my own effort. I 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 : …………………………………………

Matric No. : …………………………………………

Date : …………………………………………

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FACULTY: CIVIL & ENVIRONMENTAL ENG. PAGE NO.: 1/7DEPARTMENT: GEOTECHNICAL AND TRANSPORTATION ENGINEERING

EDITION:

REVIEW NO.:

TEST TITLE: PLASTIC LIMIT TEST EFFECTIVE DATE: 5/12/07

AMENDMENT DATE: 5/12/07

1.0 OBJECTIVE: To Determine the Lowest Moisture Content at Which the Soil Behaves Plastically.

2.0 LEARNING OUTCOMEAt the end of this experiment, students are able to:

Conduct the plastic limit experiment. Identify the plastic limit value for soil.

Identify the importance and application of plastic limit test.

3.0 THEORY

Plastic limit ( P w ) of soil is defined as the water content at which a soil will just begin to crumble when rolled into a thread of approximately 3 mm in diameter. It is water content at the boundary between the plastic and semi-solid states of consistency of the soil. Plasticity index (PI or IP) is the numerical difference of the liquid and plastic limit, and indicates the range of water content through which the soil remains plastic.

PI = LL – PL

For fine grained soils, determining the natural water content (the water content of a soil in an undisturbed condition in the ground) and relating it to the plastic and liquid limits can provide an indication of the soil’s consistency and/or sensitivity potential. One such relationship is the liquidity index.

Consistency index is defined as the ratio of the liquid limit minus the natural watercontent to the plasticity index of a soil.

Table 2.1 : Classification of soil according to plasticity.

Plasticity Index (IP or PI) Degree of Plasticity Type of Soil0 Non-Plastic Sand

< 7 Low-Plastic Silt7-17 Medium Plastic Silty clay or clayey silt> 17 Highly Plastic Clay

Table 2.2 : Classification of soil according to liquidity indices.

Liquidity Index (IL or LI) Consistency< 0.0 Desiccated (dry) hard soil

0.0-0.25 Stiff0.25-0.50 Medium to soft0.50-0.75 Soft0.75-1.00 Very soft

>1.00 Liquid s


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4.0 APPARATUS:

1. The most important piece of apparatus for this test is the hand of operator, which should be clean and free from grease.

2. Evaporating dish.3. A separate glass plate reserved for rolling of threads. This should be smooth and free from scratches, and about 300 mm square and 10mm thick. The surface condition of the plate can affect the behaviour of rolled threads, and the use of unscratched glass reduces the likelihood of discrepancies. An alternative is to reserve one side of the mixing plate for thread rolling, and avoid mixing the soil on this area. 4. Two palette knives or spatulas.5. A short length (say 100 mm) of 3mm diameter metal rod.6. Standard moisture content apparatus (container, balance and oven)

Figure 2.1 : Apparatus for plastic limit test

5.0 PROCEDURES

i) Selection and preparation of sample(a) Take about 20 g of the prepared soil paste and spread it on the glass mixing plate. (b) Mix occasionally to avoid local drying out. (c) It is convenient to set aside this sample just before carrying out the liquid limit test.

Figure 2.2 : Prepared soil paste.


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ii) Rolling Into a Ball(a) When the soil is plastic enough, it is well kneaded and then shaped into a ball. (b) When slight cracks begin to appear on the surface, divide the ball into two portions each of

about 10 g. (c) Further divide each into four equal parts, but keep each set of four parts together.

Figure 2.3 : Rolling into ball and four equal part of soil after divide.

iii) Rolling Into a Threads(a) Using a steady pressure, roll this mass into a thread between the fingers of one hand and

the surface of the glass plate. (b) The pressure should reduce the diameter of the thread from 6 mm to about 3 mm after

between five and ten back-and-forth movements of the hand. (c) It is important to maintain a uniform rolling pressure throughout; do not reduce pressure as

the thread approaches 3 mm diameter. (d) Dry the soil further by moulding between the fingers again, not by continued rolling which

gives a dried crust.(e) Form it into a thread and roll out again as before.(f) Repeat this procedure until the thread crumbles when it has been rolled to 3 mm diameter.(g) The metal rod serves as a reference for gauging this diameter. (h) The first crumbling point is the plastic limit

Figure 2.4 : The soil specimen is rolled under the fingers into a thread 3 mm diameter.


EDITION:

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iv) Moisture content measurementThis is placed in a numbered moisture content container, which is weighed, oven dried and weighed as in the standard moisture content procedure according to BS 1377: Part 2: 1990.

(a) Weight the empty moisture content container(b) Take a moisture content sample of about 10 g from the area penetrated by the cone, using the

tip of a small spatula. (c) Weight the wet sample (d) Dry in the oven for about 24 hours (overnight)(e) Weight the dry sample

(a) (b)

(c)

(d) (e)

Figure 1.10: Process to take a moisture content.


EDITION:

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6.0 CALCULATION EXAMPLE

i) Results Calculation (a) Calculate the moisture content of the soil in each of the two containers. Take the average of

the two results. (b) If they differ by more than 0.5% moisture content, the test should be repeated.

Table 1: Example of Data Sheet.Location : RECESS Loc. No. : 00123Soil description: Silty CLAY Sample No. : 6 Sample type : Undisturbed Depth of Sample : 1.5 mOperator: A . Z. S Date Started :

Test Number Units 1 2 3 4Can Number 11 21 32 41Mass of can + moist soil (Mcws) gram 46.76 57.20 63.60 71.72Mass of can + dry soil (Mcs) gram 32.51 38.31 41.64 45.78Mass of can (Mc) gram 8.31 8.35 8.26 8.29Mass of dry soil (Ms) gram 24.20 29.96 33.38 37.49Mass of water (Mw) gram 14.25 18.89 21.96 25.94Water content % 58.88 63.05 65.79 69.19Plastic limit % 64.27

Calculation of moisture content;

6.0 RESULT AND CALCULATIONS

DATA SHEETLocation : Loc. No. : Soil description: Sample No. : Sample type : Depth of Sample : Operator: Date Started :

Test Number Units 1 2 3 4Can NumberMass of can + moist soil (Mcws) gramMass of can + dry soil (Mcs) gramMass of can (Mc) gramMass of dry soil (Ms) gramMass of water (Mw) gramWater content %Plastic limit %

Plastic limit = %

Liquid limit = %

Plasticity index = Liquid Limit – Plastic Limit = %


EDITION:

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8.0 CALCULATIONS

9.0 DISCUSSIONS

10.0 CONCLUSION


EDITION:

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11.0 QUESTIONS 1

(a) What is the definition of plastic limit?

(b) A sample of wet clay and its container weigh 102 g.After oven drying the sample and the container weigh 60 g. What is the water content and plastic limit for the soil?

QUESTIONS 2

(a) What is the different between liquid limit and plastic limit?

(b) A sample of wet clay weighs 176 g. After oven drying the sample weigh 60 g and its container is 7.32 g. What is the water content and plastic limit for the soil?

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Plastic Limit Test - 004