No. of Printed Pages: 4 IBICEE-019I
B.Tech. CIVIL ENGINEERING (BTCLEVI)
Term-End Examination
June, 2016

001.26
BICEE-019 EARTH AND ROCK FILL DAM ENGINEERING
Time hours Maximum Marks: 70
Note: Answer any seven questions. All questions carry equal marks. Assume the suitable missing data, if any. Use of scientific calculator is allowed.

1. What are the relative advantages and disadvantages of rock-fill dams over earth dams? 5

According to the method of construction, what are the different types of earth dams? Discuss their relative advantages and disadvantages. 5

2. Explain, in brief, the classification of earth dam foundation. 5

What are the criteria for safe design of earth dams? Discuss in brief. 5

3. Draw the typical cross-section of earth dams when only pervious material is available, only impervious material is available, and both pervious and impervious materials are available. 6

Describe the analytical method to draw a Phreatic line for a homogeneous earth dam with a horizontal drainage blanket. 4

4. A homogeneous earth dam is 25 m high and has a crest width of 7 m. The u/s and dis slopes are 1 and 3 1 respectively. Check the stability of u/s slope by the approximate method. Assume a free board of 3 m and the height of the Phreatic line above the base at the u/s shoulder as 19 m. Take saturated weight of soil 22 kN/m3 submerged weight of soil 12 kN/m3 specific weight of water 10 kN/m3 O C 50 kN/ m2 . 10

5. An earth dam made of homogeneous material has the following data

Level of the top of the dam 200.00 m

Level of deepest river bed =178.0 m

H.F.L of reservoir 197.5 m

Width of the top of the dam 4.5 m

Upstream slope 3

Downstream slope 1 2

Length of the horizontal filter from dis toe, inwards =25 m

Cohesion of soil of the dam 24 kN/m2

Cohesion of soil of the foundation =54 kN/m2

Angle of internal friction of soil in the dam

Angle of internal friction of soil in the foundation 12°

Dry unit weight of the soil in the dam =18 kN/m3

Submerged unit weight of the soil in the dam 12 kN/m3

Dry unit weight of the foundation soil =18.3 kN/m3

Coefficient of permeability of soil in the dam x m/sec

The foundation of soil consists of 8 m thick layer of clay, having negligible coefficient of permeability. Check the stability of the dam.

6. Describe in brief the various measures to control seepage through pervious foundations. 6

Discuss the uses of flow nets. 4

7. Describe the construction details of hydraulic fill earth dams. 5

What is the difference between an earth dam and a rock-fill dam In what conditions is a rock-fill dam more suitable than an earth dam 5

8. Describe in brief the design considerations for earth dams in seismic regions. 6

Discuss the stability of upstream slope of an earth dam during sudden drawdown condition. 4

9. What do you understand by critical gradient What will happen if the critical gradient is exceeded? What is Khosla's safe exit gradient? 4

Find out the pore pressure in a layer of soil due to continuous loading which results in decrease of volume by 4%. Assume initial porosity as 0.35 and saturation ratio as 0.85. Henry's coefficient may be taken as 0.02 and initial pressures in soil pores as atmospheric. 6

10. Discuss with a sketch, surface protection of downstream slope of an earth dam. 5

Explain in brief the various undesirable effects of water seepage through the body of earth dam and its foundation. 5