seepage through earthen dam

Irrigation Practical on visulation of flow lines

1. Experiment:07 Seepage through Earth Dam K16CE-58 G.L K16CE-48 A.G.L K16CE-08 K16CE-09 K16CE-34 K16CE-46

2. Object: Visualize the position and shape of the flow line in an Earth Dam Seepage: It is movement of water in soils. Seepage depends on several factors , including permeability of soil and the pressure gradient.

3. Types of Failure due to Seepage: Failure by undermining

4. 2. Failure by direct uplift

5. Earth Dam : Dams built up by compacting successive layers of earth, using the most impervious materials to form a core and placing more permeable substances on the upstream and downstream .

6. Seepage Failure of Earthen Dam 1. Piping through Foundation

7. 2.Piping through Earthen body

8. 3. Sloughing of Down Stream Toe

9. Apparatus : Permeability Tank Description : The apparatus is a transparent-sided tank, mounted on a steel-framed bench with worktop. The tank is clear so students can see the flow patterns. The sides are plate glass to resist abrasion from the permeable medium Learning outcomes • Determination of seepage beneath a structure • Construction of flow nets and determination of coefficient of permeability • Flow under a sheet pile and determination of critical seepage force at which ‘piping’ occurs •Flow through an earth dam with and without a toe drain

10. • Drawdown in horizontal flow (simulation of ground water flow into a river or well) •Determination of uplift pressures on structures such as building foundations • General studies of seepage and drainage • Flow through a porous medium (Darcy’s law) Essential Services Water supply: Clean, cold water and drain Space needed: 2.5 m x 1.5 m of solid, level floor

11. Operating Conditions Operating Environment: Laboratory Storage Temprature Range: –25°C to +55°C (when packed for transport) Operating temperature range: +5°C to +40°C

12. Operating Relative Humidity Range: 80% at temperatures < 31°C decreasing linearly to 50% at 40°C Specifications Nett dimensions and weight: 2450 mm x 700 mm x 1500 mm and 230 kg Nominal Internal Tank Dimensions: 1800 mm or 1500 mm between mesh screens x 600 mm high x 180 mm width

13. Permeability Tank

14. Procedure: A segment of a dam of trapezoidal cross section is formed from sand in the tank so that the base of the dam is about 6 inches above the bottom of tank. The upstream slope can generally be steeper than the dls one and its toe should be approximately at the over flow outlet. For current laboratory sands, a stable dam cross section will have an upstream slope of approximately 1:3 to 2:3 and a dls slope of about 1:5 to 1 :4. The height of the dam should be 10 inches, the crest width approximately 3 inches. The upstream water level should be stabilized one inch below the dam crest; the dls level about 4 inches above the bottom.  

15. After the dam segment has been formed, water is first poured into the dls pool. Only after it is full should the upstream pool be fitted. The rate of fitting should be slow. Otherwise the dam segment can easily collapse. When the upstream water level is stabilized, needles with dye are inserted along the upstream slope (next to the transparent side of the tank), the first being fixed immediately at the water surface .

16. VIDEO

17. Hydrus Standard Software Results