SNS College of Technology,Coimbatore-35 (Autonomous) B.E/B.Tech– Internal Assessment Examination II Academic Year 2019-2020(Odd) Third Semester 16AG201 ENGINEERING GEOLOGY AND SOIL MECHANICS B (Common to Agriculture Engineering) Time: 11/2 Hours Maximum Marks: 50 Answer Key PART - A (5 x 1 = 5 Marks) 1. The appropriate value of the estimated average life of a dam reservoir is a) 25 Years b) 50 Years c) 75 Years d) 100 Years 2. The useful storage in a dam reservoir is the volume of water stored between a) minimum and maximum reservoir levels b) minimum and normal reservoir levels c) normal and maximum reservoir levels d) none of the above 3. The water content of soil is defined as the ratio of a) volume of water to volume of given soil b) volume of water to volume of voids in soil c) weight of water to weight of air in voids d) weight of water to weight of solids of given mass of soil 4. The ratio of the volume of voids to the total volume of the given soil mass, is known as a) porosity b) specific gravity c) void ratio d) water content 5. Flow net is used for the determination of a) quantity of seepage b) hydrostatic pressure c) seepage pressure d) all the above Part B 1. What are the applications of Remote Sensing in water resources project? Irrigation management Reservoir capacity monitoring Hydrology & Watershed management Water Resources Project Planning Drainage of flooded area 1 2. List the types of dam. Based on materials Earthen dams Rock fill dams Gravity dams Based on use Storage dam Diversion dam Detention dam 3. The void ratios of soil in its loosest and densest state are 0.9 and 0.4. If the void ratio in the natural state is 0.5, calculate the relative density of the soil. Id = 80 % 4. State Darcy’s law of permeability of soil. Darcy’s law states that “for laminar flow conditions in a saturated soil, the rate of flow is proportional to the hydraulic gradient” q = kiA q = the rate of flow or the discharge per unit time k = Darcy’s coefficient of permeability i = hydraulic gradient A = total mcross sectional area of soil mass 5. Define seepage velocity Seepage velocity or Actual Velocity rate of discharge of percolating water per unit cross sectional area of voids also called as actual velocity or true velocity Part C 1. Write short notes on Parambikulam Aliyar Project. Parambikulam Dam Parambikulam Dam is an embankment dam on the Parambikulam River, Parambikulam located in the Palakkad district in the Western Ghats of Kerala, India, ranks number one in India as well as in the top ten embankment dams in the world in volume in the year 2000. This Dam was built at the time of Kamarajar. The dam is operated and maintained by Tamil Nadu but the ownership rests with Kerala Aliyar Reservoir Aliyar Reservoir is a 6.48 km2 (2.5 sq mi) reservoir located in Aliyar village near Pollachi town in Coimbatore District, Tamil Nadu, South India. The dam is located in the foothills of Valparai, in the Anaimalai Hills of the Western Ghats. It is about 65 kilometres from Coimbatore. The dam offers some ideal getaways including a park, garden, aquarium, play area and a mini Theme-Park maintained by Tamil Nadu Fisheries Corporation for visitors enjoyment. The scenery is beautiful, with mountains surrounding three quarters of the reservoir. Boating is also available. 2 Hydrography Aliyar lake receives water from Upper Aliyar Reservoir through the hydroelectric power station in Navamali and the Parambikulam reservoir through a contour canal. Aliyar dam, built as a part of Parambikulam aliyar project (PAP), retains a large reservoir.The dam is around 2 kilometres (1.2 mi) in length. The lowest level outlet of the reservoir is 930 feet (280 m) above Mean Sea Level (MSL) and the canal intake is 980 feet (300 m) above MSL. The spillway is 1,040 feet (320 m) above MSL and the FRL (Full Reservoir Level) is 1,050 feet (320 m) above MSL. The maximum surface area is 48 hectares (120 acres) (1,600 acres). The volume of water at FRL is 3.864 Tmcft (88,705 acre feet (109,416,000 m3)). The maximum depth is 41 metres (135 ft) and the mean depth 16.8 metres (55 ft). The volume development is 1.2 m. The highest inflow usually occurs during July and August. The shoreline is poorly indented, the shore development is poor and shallow and the Aquatic plants and limnology of the littoral zone is also very limited. Fisheries Ailyar reservoir was studied by the Central Inland Fisheries Research Institute (CFRI) for eleven years from 1982 to 1992. The rate of energy conversion at primary producer level and at the fish production level at Aliyar is considered higher than in any other Indian reservoir. The indigenous fish of the reservoir includes 40 species belonging to 13 families, plus seven stocked species. Hydel Power Project This project consists of a series of dams interconnected by tunnels and canals for harnessing the waters of the Parambikulam, Aliyar, Sholiyar, Thunakadavu, Thekkadi and Palar rivers, flowing at various elevations, for irrigation and power generation. The scheme is an outstanding example of engineering skill. At present, the discharges are being let down through three sets of sluices/ canals, viz., Pollachi Canal, Vettaikaranpudur Canal and the river sluices. Under this scheme, the irrigation discharges let down through river sluices of the Aliyar Dam utilized for power generation in a power house at the toe of the dam. Being a micro hydel scheme, this project is subsidized by the Ministry of Non-conventional Energy Sources, Government of India. 2. Explain the factors governing the selection of dam construction. 1) Topography 2) Geology and Foundation conditions 3) Availability of materials 4) Spillway size and location 5) Earthquake zone 6) Height of the dam 7) Other considerations 3. Explain the factors affecting permeability of soil. 1) Size of soil particle 2) Specific Surface Area of Soil Particle 3) Shape of soil particle 4) Void ratio 5) Soil structure 6) Degree of saturation 7) Water properties 8) Temperature 9) Adsorbed water 10) Organic Matter 3 1.Size of Soil Particle Permeability varies according to size of soil particle. If the soil is coarse grained, permeability is more and if it is fine grained, permeability is low. The relation between coefficient of permeability (k) and particle size (D) can be shown from equation (1) as follows. 2. Specific Surface Area of Particles Specific surface area of soil particles also effects the permeability. Higher the specific surface area lower will be the permeability. 3. Shape of Soil Particle Rounded Particles will have more permeability than angular shaped. It is due to specific surface area of angular particles is more compared to rounded particles. 4. Void Ratio In general, Permeability increases with void ratio. But it is not applicable to all types of soils. For example, Clay has high void ratio than any other types of soil but permeability for clays is very low. This is due to, the flow path through voids in case of clays is extremely small such that water cannot permit through this path easily. The relation between coefficient of permeability and void ratio can be expressed from equation (1) as For Clay Where, C = Shape of the flow path, e = Void ratio. For coarse grained soil, “C” can be neglected. Hence 5. Soil Structure Structure of any two similar soil masses at same void ratio need not be same. It varies according to the level of compaction applied. If a soil contains flocculated structure, the particles are in random orientation and permeability is more in this case. If the soil contains dispersed structure, the particles are in face to face orientation hence, permeability is very low. The permeability of stratified soil deposits also varies according to the flow direction. If the flow is parallel, permeability is more. If it is perpendicular, permeability is less. 4 6. Degree of Saturation Partially saturated soil contain air voids which are formed due to entrapped air or gas released from the percolating fluid or water. This air will block the flow path thereby reduces the permeability. Fully saturated soil is more permeable than partially saturated soil. 7. Water Properties Various properties of water or fluid such as unit weight and viscosity also effects the permeability. However, unit weight of water will not affect much since it does not change much with temperature. But when temperature is increased viscosity decreases rapidly. From equation (1), permeability increase when viscosity decreases. 8. Temperature Temperature also affects the permeability in soils. From equation (1), permeability is inversely proportional to the viscosity of the fluid. It is known that viscosity varies inversely to the temperature. Hence, Permeability is directly related to temperature. Greater the temperature, higher will be the permeability. That is the reason, seepage is more in summer seasons than in winter. 9. Adsorbed Water Adsorbed water is the water layer formed around the soil particle especially in the case of fine- grained soils. This reduces the size of the void space by about 10%. Hence, permeability reduces. 10. Organic matter Presence of organic matter decreases the permeability. This is due to blockage of voids by the organic matter. 4. The mass specific gravity of a fully saturated specimen of clay having a water content of 40% is 1.88. On oven drying the mass specific gravity drops to 1.74. Calculate the specific gravity of clay and its shrinkage limit.