VTU Civil Engineering (Semester 5)
Geotechnical Engineering 1
December 2016
Total marks: --
Total time: --
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1(a) Define the following with the help of three phase diagram. Indicate the uints: i) degree of saturation
ii) Water content
iii) specific gravity iv) air content.
8 M
1(b) Prove that S×e = w×G.
6 M
1(c) How many cubic meter of soil can be formed with a void ratio of 0.5 from 100 cubic meters of soil shaving void ratio of 0.7.
6 M

2(a) With the help of particle size distribution curve explain: i) Well graded soil
ii) Unifomly graded soil
iii) Gap graded soil.
6 M
2(b) A soil sample, consisting of particles size ranging from 0.5 mm to 0.01 mm, is put on the surface of still water tank 5 meters deep. Calculate the time of settlement of the coarsest and finest particles of the sample to the bottom of the tank. Assume average sp. Gravity of soil particles as 2.66 and viscosity of water as 0.01 poise.
6 M
2(c) The results of a liquid limit test are given below:
No. of blows 48 38 29 20 14
Water  content (%) 32.1 35.9 40.9 46.1 52.8
The plastic limit of the soil is 23%. Plot the flow curve and determine:
i) Liquid limit
ii) Plasticity index
iii) Flow index and iv) Toughness index.
8 M

3(a) Explain plasticity chart with a neat sketch and its use in classification of fine grained soil.
8 M
3(b) Explain any two clay minerals with the help of neat sketches.
8 M
3(c) Explain how to distinguish silt and clay in the field.
4 M

4(a) Derive an expression to obtain coefficient of permeability under falling head condition.
6 M
4(b) Define permeability. List and explain factors affecting permeability of soil.
6 M
4(c) Calculate the co-efficient of permeability of a soil sample, 6 cm in height and 50 cm2 in cross-sectional area. If a quantity of water equal to 430 ml passed down in 10 minutes, under an effective constant head of 40 cm. On even drying the test specimen has mass of 498 gms. Taking the speicific gravity of soil soilds as 2.65, calculate the seepage velocity of water during the test.
8 M

5(a) Explain the types of shear test based on different darinage conditions.
6 M
5(b) What are the advantages and limitations of direct shear test?
6 M
5(c) A consolidated undrained test was conducted on clay sample and the following results are obtained:
Cell  pressure (kN/m)2 200 400 600
Deviator stress at failure (kN/m)2 118 240 352
 Pore water  pressure at failure (kN/m)2 110 220 320
Determine the shear strength parameter with respect i) total stresses ii) effective stresses.
8 M

6(a) List and explain factors affecting compaction.
5 M
6(b) List the differences between standard and modified proctor compaction test.
5 M
6(c) The following are the result of a compaction test
Mass of mould + wet soil (gm) 2925 3095 3150 3125 3070
Water content (%) 10.0 12.0 14.3 16.1 18.2
Volume of mould = 1000 ml
Mass of mould = 1000 gms
i) Find the compcation curve showing the optimum moisture content (OMC) and maximum dry density
ii) Plot the zero air void line
iii) Determine the degree of saturation.
10 M

7(a) Explain spring analogy theory of consolidation of soil.
7 M
7(b) What is pre comsolidation pressure? How it is determined by Casagrande's graphical method?
7 M
7(c) Explain pre consolidated, normally consolidated and under consolidated soil.
6 M

8(a) Explain square root time fitting method for determination of consolidation.
8 M
8(b) Explain vane shear test with near sketch.
4 M
8(c) An undistributed smaple of clay, 24 mm thick, consolidated 50% in 20minutes, when tested in laboratory with drainage allowed at top and bottom. The clay layer, from which the sample was obtained, is 4m thick in the filed. How much time will it take to consolidated 50% with double drainage? If the clay stratum has only single drianage, calculate the time to consolidate 50%. Assume uniform distribution of consolidation pressure.
8 M

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