civil engineering level 2, soil density practical assignment (Geotechnical engineering)

CE2004 SOIL DENSITY PRACTICAL

Aims
?  To build fundamental understanding of how engineering soils respond to changes in stress
and water content
?  To develop skills in collecting, recording and presenting laboratory data
?  To develop an appreciation for accuracy and precision, and how to deal with it

Introduction
Understanding the response of soils to changes such as load and water content is an essential part of
site evaluation, design, construction and monitoring.  There are many ways of assessing these
responses.  This practical focuses on two key measures of change: minimum density and maximum
density.  Details of what should be submitted are given at the end of the practical description.

Health & Safety note
The following procedures involve potentially hazardous masses.  Particular hazards are posed by the
steel rammer and the Proctor mould (especially when full of compacted soil).  For Part 1, below,
protective gloves and safety boots should be worn and the heavy items handled with care.  Wear a
lab coat at all times.

Task

Part I: Density Changes
a

1.  In groups, select a dry sandy soil and, if necessary, sieve to remove particles >2mm (i.e.
gravel or coarser).
2.  Describe the soil.

3.  Take a known mass of the soil, M (e.g. 900g ? 10g), and place in a graduated 1 litre
measuring cylinder.  Tap the side of the cylinder gently to allow for a small amount of
settlement and to level the surface of the soil.
4.  Record the volume of the soil in ml.
5.  Calculate the dry bulk density
b
:
?
d
= M/V

6.  Shake the cylinder and invert it a few times to loosen the soil.
7.  Turn the cylinder upside down, pause until the sand has ceased moving, then quickly, in a
single movement, turn the cylinder the right way up and stand it on a flat surface (be careful
not to knock or jar the cylinder at this stage.
8.  Record the new volume V in mL to the nearest 10mL
9.  Record if the soil exhibits any sorting of particles
10. Repeat steps 5-8 for a total of ten times
11. Calculate the “minimum” dry density of the soil (?
dmin) in Mg/m
3
using the equation:
?
dmin
= M/V

where V is the greatest of the volume readings.  Express the results to the nearest 0.01
Mg/m
3

12. Take a sample of the pre-wetted soil (this has a moisture content, w = M
w/M
s
).  You will need
around 2.5-3.0 kg.
13. Weigh the Proctor (density assessment) mould to 10g precision (m1
)
14. Measure its internal diameter to 1mm precision and determine its volume, Vm
c
.
15. Attach extension to the mould and place on a solid surface (e.g. concrete floor)
16. Fill the mould (not mould plus extension) with a layer of soil just over 1/3
rd
of its depth

a
The density change experiments are slightly modified versions of those given in BS 1377:4
b
In this case, the density = dry bulk density as the sample is oven dry
c
Vm
= ?r
2
x height of mould
17. Apply 27 (twenty seven) blows to the soil using the 2.5kg rammer, with a fall of exactly 30cm
– to do this, pull the handle to its full extent.
a.  Ensure blows are spread evenly across the surface
b.  Make sure inside of rammer is not clogged by soil before each blow
c.  ! THE RAMMER IS HEAVY. WEAR PROTECTIVE GLOVES AND ENSURE YOUR HANDS ARE KEPT
CLEAR DURING OPERATION.
18. Repeat stages 15 and 16 until, after ramming, the soil fills the mould and the lower part of the
extension
19. Remove the extension and level the soil across the top of the mould
20. Weigh the Proctor mould and compacted soil to 10g precision (m2
)
21. Remove the soil and clean out the mould
22. Calculate bulk density:
a.  ? = (m2
-m1
) / Vm

23. Calculate “maximum” dry density in Mg/m
3
:
a.  ?
dmax
= 100? / (100+w)
d

24. Check your working area and clean up any spilt soil

Remember, if you make a mistake, start again!

Work to submit (10% of module mark) Due: 4pm, Thursday 6
th
November 2014

?  Your raw data for both density tests on one soil
?  Full calculations and results
?  Use the particle size data for your soil available on Blackboard to plot a cumulative graph of
the percentage passing each sieve (annotate as appropriate)
?  A table of summary statistical values for the particle size data
?  A concise discussion of potential sources of error (200 words maximum)
?  A concise discussion of the accuracy, precision, strengths and limitations of the methods (250
words)

Marks will be awarded for:
?  Following the coursework specification
?  Correct presentation of data
?  Correct calculations and presentation of results
?  Consideration of errors
?  Consideration of accuracy, precision, strengths and limitations of the methods
?  Presentation, including neatness, spelling and grammar

d
w = moisture – see stage 2 – should be around 10% for the CE1002 practical