CONCRETE DAM LECTURE 1

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Drainage galleries Shafts Overflow section Non-overflow section Power house Energy dissipation works Outlets Joints A gallery is a small passage in a dam for providing an access to the interior of the dam. The gallery is usually rectangular in shape with its top and bottom either flat or semi circular. For a gallery with its top and bottom flat, it is necessary that all the corners should be rounded. The width of gallery generally varies from 1.5 to 1.8 m. The height of the gallery in between 2.2 to 2.4 m, so that a person can easily walk inside it. A Foundation gallery b. Drainage gallery c. Inspection gallery d. Grouting gallery e. Gate gallery 1. To provide drainage of the dam section. 2. To provide space for equipment required for drilling holes and grouting the hole to form a grout curtain in the foundation. 3. To provide space for header and return pipes for post cooling of concrete. 1. To provide drainage of the dam section. 2. To provide space for equipment required for drilling holes and grouting the hole to form a grout curtain in the foundation. 3. To provide space for header and return pipes for post cooling of R

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CONCRETE DAM ENGINEERING:

CONCRETE DAM ENGINEERING Components of a Gravity Dam and their Functions 1/28/2014 1 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET

Components of a Gravity Dam and their Functions:

Components of a Gravity Dam and their Functions Drainage galleries Shafts Overflow section Non-overflow section Power house Energy dissipation works Outlets Joints 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 2

Drainage galleries ::

Drainage galleries : A gallery is a small passage in a dam for providing an access to the interior of the dam. The gallery is usually rectangular in shape with its top and bottom either flat or semi circular. For a gallery with its top and bottom flat, it is necessary that all the corners should be rounded. The width of gallery generally varies from 1.5 to 1.8 m. The height of the gallery in between 2.2 to 2.4 m, so that a person can easily walk inside it. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 3

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1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 4

Types of gallery based on uses ::

Types of gallery based on uses : A Foundation gallery b. Drainage gallery c. Inspection gallery d. Grouting gallery e. Gate gallery 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 5

Functions of a gallery ::

Functions of a gallery : 1. To provide drainage of the dam section. 2. To provide space for equipment required for drilling holes and grouting the hole to form a grout curtain in the foundation. 3. To provide space for header and return pipes for post cooling of concrete. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 6

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4. A gallery provide an access to the interior of the dam for inspection ard maintenance. 5. A Gallery also provides space for installing various instruments in the dam to study its structural behaviour. 6. A gallery can provide space for the mechanical and electrical equipment required for the operation of gates for spillways and outlets. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 7

2. Shafts ::

2. Shafts : A shaft is a vertical opening provided in a dam. Shafts are required for locating headers of the post cooling system and for locating measuring devices. Shafts are also required for the movement of elevators and the hoisting equipment. Sometimes shafts are constructed inclined to connect two galleries or the same gallery at two different elevations by a staircase or a lift arrangement. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 8

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A plumb line shaft is constructed at the maximum section of the dam to make observations of the deflection of the dam under loads. A plumb bob is suspended by a wire fixed at the top of the shaft. As the dam deflects relative to the base, the plumb bob also moves by the same amount. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 9

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A stilling well shaft is a special shaft used to record fluctuations of the water level in the reservoir. The shaft is connected to the reservoir at a point below the minimum reservoir level. There is a floating mechanism in the stilling well shaft which records fluctuations in the water level. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 10

3. overflow Section ::

3. overflow Section : The spillway in a gravity dam is called overflow section. Spillway is provided to dispose of surpluswater from the reservoir to the downstream. Spillways are provided for all dams as a safety measure against overtopping and the consequent damages, and failure. spillway may be located either in the middle of the dam or at the end of the dam near abutment. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 11

Requirements of Spillway ::

Requirements of Spillway : It must have adequate discharge capacity. It must be hydraulically and structurally safe. The surface of the spillway must be erosion resistant. It should be provided with some device for the dissipation of excess energy. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 12

Non-overflow section ::

Non-overflow section : The portion of the gravity dam other than the spillway is a non-overflow section, a road is located on the non-overflow section of the dam. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 13

Power house ::

Power house : At the one end of a gravity dam a power house is located. Water from the reservoir passes tnrough penstock and rotates the turbine provided at power elevations to produce electricity. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 14

Energy dissipation works ::

Energy dissipation works : Water flowing over a spillway has a very high kinetic energy because of the conversion of the entire potential energy to the kinetic energy. If the water flowing with such a high velocity is discharged directly into the channel down stream, serious scour of the channel may be occur. If the scour is not properly controlled it may extend backward and may damage the spillway and the dam. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 15

The energy dissipation devices can be broadly classified into two types. :

The energy dissipation devices can be broadly classified into two types. Devices using a hydraulic jump Devices using a bucket Following constructions are provided for energy dissipation : 11 Deflector bucket 1) Sharply upturned bucket 5 End sill with baffles - Stilling basin, 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 16

7. Outlets ::

7. Outlets : A major portion of the storage volume in the reservoir on the upstream of a dam is below the spillway crest level. Dam outlets are provided in the body of the dam or its abutments below the crest level of the spillways so that the water can be withdrawn from the reservoir. Sluiceways are the special type of outlets provides in the body of a concrete gravity dam 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 17

Classification of outlets based on purpose ::

Classification of outlets based on purpose : River outlet - discharge water into the river Canal outlet - discharge water into the canal. Pipe outlet - delivers water into a closed pipe. Classification of outlet based on gates : • Gated outlets • Ungated outlets 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 18

8. Joints ::

8. Joints : 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 19

(a) Construction Joints:

(a) Construction Joints Construction joints are providedfor ease in construction of the dam. They also permits systematic, convenient and economical construction of the dam. It is usual practice to place the concrete in a gravity dam in lifts so as to avoid excessive heat of hydration of cement. These are the horizontal joints. The thickness of each layer of concrete should not be more than 1.5 m. The thickness of the first layer of concrete above rock foundation should not be more than 0.75 m. 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 20

(b) Contraction joints ::

(b) Contraction joints : Contraction joints are provided to avoid cracks caused due to shrinkage of concrete due to temperature changes. Contraction joints are of two types : ( i ) Transverse joints (ii) Longitudinal joints 1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 21

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1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 22

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1/28/2014 PREPARED BY V.H.KHOKHANI, ASSISTANT PROFESSOR, DIET 23

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