MARKING SCHEME:

Quality of assignment (20%)

Question 1: PSD (10%)

Question 2: Liquid limit (5%)

Question 3: Soil name and group symbol (15%)

Question 4: New PSD (5%)

Question 5: OMC and MDD (15%

Question 6: Saturation degree at optimum (10%)

Question 7: Amount of water (5%)

Question 8: Plot flow rate and hydraulic gradient (10%)

Question 9: Permeability (5%)

Some soil has been collected from a site where a commercial centre will be built, to determine

its basic geotechnical characteristics in the laboratory. The experimental data from the different

tests are given in the tables below. The soil specific gravity was measured at 2.62 and the plastic

limit at 18%.

Table 1: results of sieve analysis

Sieve aperture [mm]

100

75

63

37.5

26.5

19

13.2

9.5

6.7

4.75

2.36

1.18

0.600

0.425

0.300

0.212

0.200

0.075

<0.075 mm

Mass retained on sieve [g]

0

0

0

422.5

315.4

378.7

460.2

596.7

687.1

744.7

1346.7

333.2

363.6

114.0

Table 2: Data for measurement of liquid limit

Mass

Mass container +

container [g]

wet soil [g]

32.5

118.9

32.5

137

32.5

133.8

32.5

119.3

32.5

97.4

32.5

98.7

57.5

65.9

44.8

82.8

684.1

Mass container

+ dry soil [g]

86.4

100

99.5

92.5

78.7

81.6

# of blows

13

16

19

22

28

32/nTable 3: Compaction. Modified proctor compaction. Mould volume = 2.4 litres.

Bulk mass of soil [g]

Gravimetric moisture content [%]

3593

8.2

4224

9.6

4585

10.5

4659

12

4345

13.5

Table 4: Data for permeability tests (constant head). Specimen diameter: 100 mm, height

200mm. Head difference is measured via two piezometers inserted on the side of the

permeameter and separated by 100mm (see Figure 1). Specimen compacted at MDD and

OMC.

Test #

1

2

3

4

5

6

constant

head tank.

timer

A

Head difference

[cm]

3

6

8

12

15

18

piezometers

h₂

h₁

datum

Mass of water

collected [g]

77

157

190

260

340

390

Figure 1: constant head permeameter used to

measure the material's permeability.

L=100mm, h2-h1 = head difference.

Duration of water

collection [s]

62

67

58

60

70

75

1. Plot the particle size distribution of the material using a logarithmic scale for the sieve

aperture. Show an example calculation for the sieve size 19mm. Tabulate and plot the

rest of the results.

2. Find liquid limit of the soil using data of Table 2

3. Name the soil and find group symbol

For both compaction and permeability testing, all particles larger than 13.2 mm were

removed to fit within the mould and the permeameter.

4. Using the data of Table 1, plot the particle size distribution of the material once the

large (i.e., >13.2 mm) particles have been removed. Show an example calculation for

the sieve size 9.5mm. Tabulate and plot the rest of the results.

5. Process the data of Table 3 and find the MDD and OMC according to standard

AS1289.5.1.1:2017. Show one example calculation, tabulate the rest of the results.

6. Compute the saturation degree at the point optimum (OMC, MDD)

7. What amount of water needs to be added to the specimen compacted in the

permeameter to achieve saturation?

8. Process the data of table 4 to plot flow rate vs hydraulic gradient and conclude on

which tests should be used to compute the permeability. Provide all calculations for

test #1, tabulate the rest of the results.

9. Compute the permeability of the material.

END OF ASSIGNMENT