SOIL MECHANICS LABORATORY MANUAL

VERSION 1.2 16/11/2014

CVNG 2008 – SOIL MECHANICS I

By: Dr. Derek Gay & Damian Alexander The University of the West Indies, St. Augustine. Trinidad and Tobago

TABLE OF CONTENTS

TABLE OF CONTENTS..................................................................................................................1

LAB REPORT OUTLINE – (FOR EACH LAB)........................................................................0

EXPERIMENTAL REPORT REQUIREMENTS......................................................................1

ATTERBERG ANALYSIS..........................................................................................................1

CALCULATIONS....................................................................................................................1

COMPACTION TEST..................................................................................................................3

CALCULATIONS....................................................................................................................3

DISCUSSION...........................................................................................................................4

UNCONFINED COMPRESSIVE STRENGTH TEST................................................................5

1

LAB REPORT OUTLINE – (FOR EACH LAB)

COVER PAGE – Includes

- Name of Experiment

- Name of Student

- ID #

- Group #

- Date experiment was performed

- Date for lab report submission

- Course Code

- Year/Semester

TITLE

TABLE OF CONTENT

AIM

OBJECTIVE

APPARARUS USED – (A labelled sketch or Picture of all equipment used)

INTRODUCTION (2-3 short paragraphs including equations)

PROCUDURE

RESULTS

ANALYSIS (CALCULATIONS)

DISCUSSION

CONCLUSION

REFERENCES – Chicago manual of style 16th edition (Author-Date)

APPENDIX – (This includes the data sheets or raw data obtained from the lab for each lab)

EXPERIMENTAL REPORT REQUIREMENTS

ATTERBERG ANALYSIS

(Refer to Krishna Reddy Exp. 7 Atterberg Limits)

CALCULATIONS

A- Liquid Limit, LL

1- Plot the relationship between the water content, w, and the corresponding number of

drops, N, of the cup on a semi-logarithmic graph with water content as the ordinates and

arithmetical scale, and the number of drops on the abscissas on a logarithmic scale. Draw

the best fit straight line through the 3 or more plotted points.

2- Take the water content corresponding to the intersection of the line with the 25 drop

abscissa as the liquid limit, LL, of the soil.

B- Plastic Limit, PL

1- Compute the average of the water contents obtained from the three plastic limit tests. The

plastic limit, PL, is the average of the three water contents.

C- Plasticity Index

1- Calculate the plasticity index as follows:

PI = LL - PL

where:

LL = Liquid Limit, and PL = Plastic Limit.

1

Figure 1: Plasticity Chart (Budhu, M., Soil Mechanics and Foundations, 3rd Edition. 2010: John Wiley & Sons,

2- Determine the soil classification of the sample used using Figure 1.

DISCUSSION

1- State the importance of finding the plasticity index in Civil Engineering. Explain the

significance of Liquid Limit and Plastic Limit of a soil.

2- Give 2 examples in which these values are used in the construction industry.

3- Give 3 sources of error and precautions that may be taken to avoid them.

4- State what can be done to improve the experiment as it may relate to its accuracy and

precision.

2

COMPACTION TEST

(Refer to Krishna Reddy Exp. 9 Moisture-Density Relation (Compaction) Test)

CALCULATIONS

(1) Calculate the moisture content of each compacted soil specimen by using the average of

the two water contents (If two samples were taken to determine the moisture contents

then find the average using those values).

(2) Compute the wet density in grams per cm3 of the compacted soil sample by dividing the

wet mass by the volume of the mould used.

(3) Compute the dry density using the wet density and the water content determined in step

1. Use the following formula:

where: 𝜔 = moisture content in percent divided by 100, and 𝜌 = wet density (Bulk Density) in

grams per cm3.

(4) Plot the dry density values on the y-axis and the moisture contents on the x-axis. Draw a

smooth curve connecting the plotted points.

(5) On the same graph draw a curve of complete saturation or “zero air voids curve”. The

values of dry density and corresponding moisture contents for plotting the curve can be

computed from the following equation

𝑜𝑟

3

where:

𝜌𝑑= dry density of soil grams per cm3

Gs = specific gravity of the soil being tested (assume 2.70)

𝜌𝑤 = density of water in grams per cm3 (approximately1 g/cm3)

𝜔𝑠𝑎𝑡= moisture content in percent for complete saturation.

(6) Identify and report the optimum moisture content and the maximum dry density.

Make sure that you have recorded the method of compaction used (e.g., Standard

Proctor, Method A) on data sheet.

DISCUSSION

1- State the importance of finding the optimum moisture content and the maximum

dry density in Civil Engineering.

2- Give 4 examples in which these values are used in the construction industry.

3- Give 3 sources of error and precautions that may be taken to avoid them.

4- State what can be done to improve the experiment as it may relate to its accuracy and

precision.

5- Question from Dr. Gay.

4

UNCONFINED COMPRESSIVE STRENGTH TEST

(Refer to Krishna Reddy Exp. 13 Unconfined Compression Test)

5