JNTU
JNTU B.Tech III EARTH AND ROCK FILL DAMS AND SLOPE STABILITY Previous Question Paper (March-2024 - R16)
Note: i) Question paper consists of Part A, Part B.
ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions.
iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What is the importance of pore water pressure in earthen dams?
Answer
Pore water pressure is critical in earthen dams because it directly influences the effective stress within the soil mass, which governs the shear strength of the dam material. According to the principle of effective stress, an increase in pore water pressure reduces the inter-granular contact forces, thereby decreasing the internal frictional resistance and increasing the risk of slope instability or shear failure. Additionally, high pore water pressures can lead to internal erosion, piping, and hydraulic fracturing, which are significant threats to the structural integrity and safety of the dam.
What are earthen dams and under what circumstances are they preferred?
Answer
An earthen dam is a structure constructed primarily of compacted soil, sand, gravel, or rock fill, designed to impound water. It relies on its own weight and the shear strength of the materials to resist the pressure of the reservoir.
Earthen dams are preferred under the following circumstances:
- Foundation conditions: They are ideal when the foundation material is relatively weak or compressible, as the dam's flexibility allows it to adjust to minor settlements without cracking.
- Availability of materials: They are the most economical choice when large quantities of suitable natural soil, sand, or rock are available locally at the dam site, reducing transportation costs.
- Topography: They are well-suited for wide valleys where the construction of a concrete gravity dam would be prohibitively expensive or structurally difficult.
What is the purpose of core wall in earthen dam?
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Enumerate different drainage systems used in earthen dam.
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What do you know about Infinite slope?
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What are the factors leading to the failure of slopes?
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What are the different methods used for analysis of finite slope?
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List out the factor of safety used in stability Analysis of slopes.
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Explain the purpose of rock fill dam.
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What are the classification of earth fill and rockfill dams?
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Part B
Explain the method of checking the stability of earth dam foundation against shear failure.
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Explain with the help of a sketch the components of a zoned embankment dam, with their functions.
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An embankment has a slope of 2 (horizontal) to 1 (vertical) with a height of 10 m. It is made of a soil having a cohesion of 30 kN/m2, an angle of internal friction of 50 and a unit weight of 20 kN/m3. Consider any slip circle passing through the toe. Use the friction circle method to find the factor of safety with respect to cohesion.
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Discuss the method for checking the stability of an infinite slope in a cohesive soil. What is critical height and state its importance.
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Explain how the Seepage is Controlled Through Embankments.
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A flow net is plotted for a homogeneous earthen dam of height 22 m and freeboard 2.0 m. The results obtained are i) Number of potential drops = 10; ii) Number of flow channels = 4. The dam has a horizontal filter of 30 m length at the downstream end and the coefficient of permeability of the dam material is 5 × 10-4 cm/sec. Calculate the discharge per m run of the dam.
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Find the factor of safety of a slope of infinite extend having c' = 30 kN/m2, φ = 200, e = 0.65, G = 2.7 under the following conditions: (a) When soil is dry. (b) When the slope is submerged. The angle of slope α = 250.
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How many methods of testing could be made for the stability analysis of earth dam?
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Explain in detail the stability of upstream and downstream slopes immediately after construction.
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A soil is having following properties: - Cohesion (C) = 9 kN/m2, Angle of Internal friction (φ) = 200, Unit weight (γ) = 18 kN/m3, Calculate the critical depth of vertical excavation that can be made in the soil without any lateral support. The ground carries a surcharge load of 3 kN/m2.
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Explain different types of slope failures in earthen dam and method of improving stability of slopes.
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Explain the relation for the factor of safety of an infinite slope made of cohesionless soil subjected to seepage parallel to the slope.
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Explain the structural requirements factor for compacted rock fill dam and how can increase the shear strength between compacted rock fill layers.
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How can differentiate the rock fill dam with respect to gravity and earthen dams?
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What are the functions of earth core in rock fill dam and discuss of earth core importance in view of functional aspects.
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Discuss the upstream and downstream slopes provision of rock fill dam and compare them with earthen dams.
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