Objective: Assessment of Permeability of Soil by Constant Head Permeameter.
Theory:
The coefficient of permeability is equivalent to the degree of flow of water from a unit cross segment area underneath a unit hydraulic gradient. In the unimould head permeameter, the head inducing flow from the sample becomes constant during the experimentation. The coefficient of permeability (k) is acquired from the relation
Where,
q= discharge,
Q=total volume of water,
t=time period,
h=head causing flow,
L= length of specimen,
A= cross-sectional area.
Tool and Equipment
- Detachable collar, 100mm diameter, 60mm height
- Dummy plate, 108 mm diameter, 12mm thick,
- Drainage base, having porous disc
- Drainage cap having porous disc with a spring attached to the top
- Permeameter mould, internal diameter = 100mm, effective height =127.3 mm, capacity = 1000ml.
- Compaction equipment like the Proctor’s rammer or a static compaction equipment
- Stop watch
- Large funnel
- Thermometer
- Weighing balance accuracy 0.1g
- Filter paper.
- Constant head water supply reservoir
- Vacuum pump
- Constant head collecting chamber
Process
1. Expel the collar of the mould. Take the measurement of the inward measurements of the mould. Measure the mould with sham plate to the closest gram.
2. Apply a little oil within to the mould. Fasten the mould between the base plate and the expansion collar, and place the assembly on a strong base.
3. Take around 2.5kg of the soil specimen, from a completely blended wet soil, in the mould. Now compress the soil at the mandatory dry thickness utilizing a reasonable compacting equipment.
4. Expel the collar and base plate. Trim the unnecessary soil level with the highest point of the mould.
5. Clean the exterior of the mould and the of the dummy plate. Compute the weight of the dirt in the mould.
6. Take a little specimen of the soil in a compartment for the water content determination.
7. Immerse the permeable disc (stones).
8. Put a permeable disc on the drainage base and keep a channel paper on the permeable plate.
9. Evacuate the dummy plate and place the mould with soil on the drainage base subsequent to embedding a washer in the middle.
10. Clean the edges of the mould. Apply oil in the furrows around them.
11. Put a proper filter paper, a permeable disc and settle the drainage top utilizing washers.
12. Join the water reservoir to the outlet at the base, and permit the water to stream upwards, till it has immersed the specimen. Give the free water a chance to gather for a profundity of around 100mm on the highest point of the specimen.
[Alternatively the soil of low porousness can be soaked by exposing the example to a bit by bit expanding vacuum with base outlet shut in order to expel the air from the voids. Increment the vacuum step by step to 700mm of mercury and keep up it for at least 15minutes, contingent on the kind of the soil. Take after the evacuation by a procedure of moderate immersion of the specimen from the base upward under full vacuum. At the point when the example is immersed, close both the top and base outlets.]
13. Fill the unfilled segment of the mould with coveted water without aggravating the soil.
14. Separate the source from the outlet at the base.
15. Connect the constant head reservoir with the drainage cap inlet.
16. Open the stop clock and permit the water to stream through so that all the air is evacuated.
17. Close the stop-clock, and permit the water to move through the dirt till a stable state is achieved.
18. Begin the stop watch and gather the water streaming out of the base in a measuring cup for some expedient time interim.
19. Rehash this procedure thrice keeping a similar interim. Watch that the amount of water gathered is roughly the same each time.
20. Measure the distinction of head (h) in levels between the consistent head repository and the outlet in the base.
21. Rehash the test for minimum two more varied interims.
DATA SHEET FOR CONSTANT HEAD PERMEAMETER
Diameter = 100mm, length =____, volume=______ ml, G=____, Area=_____ 
| Sl. No. | Observations and Calculations | Determination No. | ||
| 1 | 2 | 3 | ||
| Observation | ||||
| 1 | Mass of empty mould with base plate | |||
| 2 | Mass of mould, soil and base plate | |||
| 3 | Hydraulic head (h) | |||
| 4 | Time interval (t) | |||
| 5 | Quantity of flow (Q) | |||
| (a) First time in period t | ||||
| (b) Second time in period t | ||||
| (c) Third time in period t | ||||
| Average Q | ||||
Calculations |
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| 6 | Mass of soil = (2) – (1) | |||
| 7 | Bulk Density  |
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| 8 | Water content w | |||
| 9 | Dry density  |
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| 10 | Void ratio  |
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| 11 |  |
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Result:
Coefficient of permeability of the given soil =_______ mm/sec.