lab infiltration test

LAB – 3 Date -18-Jan-2011

Objective: To determine infiltration rate by double ring infiltrometer.

Apparatus required: The apparatus required to perform this test are:

1) Double ring infiltrometer,

2) Driving plate,

3) Impact-absorbing hammer,

4) Measuring bridges and measuring rods.

Theory: The double ring infiltrometer is a simple instrument that is used to determine the rate of infiltration of water into the soil. The rate of infiltration is determined as the amount of water per surface area and time unit that penetrates the soil. It consists of an inner and outer ring inserted into the ground. Each ring is supplied with a constant head of water either manually or from mariotte bottles.

Double ring infiltrometer works by directing water onto a known surface area due to the parameters of the inner ring. The rate of infiltration is determined by the amount of water that infiltrates into the soils per surface area, per unit of time. Infiltration can be measured by either a single or double ring infiltrometer, with preference usually lying with the double ring because the outer ring helps in reducing the error that may result from lateral flow in the soil.

Procedures: The procedures involved for lysimeter calibration test are:

1) Place two rings with the cutting edge facing down on the ground. Remove small obstacles such as stones or twigs. When measuring below the ground surface, a profiled pit should be made.

2) Put the driving plate on top of the rings. Depending on its diameter the ring will fit over, between or within the pins located on the bottom side of the driving plate.

3) Use the impact-absorbing hammer to insert the infiltration ring about 10 cm vertically into the soil. Make sure to disturb the soil as little as possible. In stiff soils have someone stand on the driving plate while another person drives it in and remove the driving plate from the inserted infiltration ring.

4) Fill the outer ring with water, then the inner ring, to approximately 5 - 10 cm. Start measuring immediately to determine the infiltration curve. To protect the ground surface when pouring the water, use plastic foil, a jute cloth, sponge or a 1-2 cm layer of sand or gravel. It is also possible to pour the water via your hand on the ground.

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5) Start the measuring by noting the time and the water level in the inner ring (reference level) as indicated on the measuring rod.

6) Determine the drop in the water level in the inner ring during a certain interval. Note the time and the water level.

7) Poured the fixed volume of water into the inner ring when the water level goes down to a certain level and note the time.

8) Keep the water in the inner and outer ring at a similar level. A higher water level in the outer ring will lead to a decreasing infiltration rate in the inner ring. A lower water level in the inner ring will cause the buffering against lateral spreading to decrease.

9) Stop the measuring only when the time differences are same for consecutively 4 to 5 times. After that remove the infiltrometer.

Observations: The observations are: Table 1. Observations for Site 1

Volume of water poured into the inner ring (lit)

Cumulative time(sec)

1 54

1 105

1 183

0.5 224

0.5 270

0.5 350

0.5 367

0.5 418

0.5 475

0.5 532

0.5 595

0.5 659

0.5 725

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0.25 7580.25 7880.25 8240.25 8610.25 8960.25 9260.25 9620.25 9950.25 10300.25 10630.25 10990.25 11350.25 1172



0.25 12080.25 12470.25 12830.25 13220.25 13600.25 13950.25 14330.25 14730.25 15120.25 15500.25 15900.25 16310.25 16700.25 17140.25 17530.25 17930.25 18340.25 18830.25 19300.25 19550.25 19960.25 20340.25 20780.25 21210.25 21700.25 22300.25 22770.25 23260.25 23800.25 24350.25 24880.25 25460.25 2602

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0.25 26550.25 27120.25 27700.25 28250.25 28850.25 29400.25 30000.25 30600.25 31200.25 31800.25 3240

Table 2. Observations for Site 2


Cumulative time (sec)

0.51 430.51 1290.51 2300.3 3020.3 3750.3 4590.3 5370.3 6140.3 6970.3 7780.3 8600.3 9420.3 10300.3 11160.3 12120.3 13090.3 14040.3 15020.3 16080.3 17190.3 18310.3 19470.3 20660.3 21840.3 23050.3 24260.3 25520.3 2678

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0.3 28040.3 2930

Calculation:

The diameter of the inner ring is = 0.27 m.

So, the cross-sectional area = = = 0.0573 m2.

Table 3. Calculation for site 1


Elapsed time(min)

Volume of water(lit)

Depth of water(cm)

Infiltration rate

(cm/hr)

Accumulated infiltration

(cm)

54 0.9 1 1.745201 116.3467132 1.745201

105 0.85 1 1.745201 123.1906375 3.490401

183 1.3 1 1.745201 80.54772453 5.235602224 0.683333 0.5 0.8726 76.61856723 6.108202270 0.766667 0.5 0.8726 68.2904621 6.980803350 1.333333 0.5 0.8726 39.26701571 7.853403367 0.283333 0.5 0.8726 184.7859563 8.726003418 0.85 0.5 0.8726 61.59531876 9.598604475 0.95 0.5 0.8726 55.11160099 10.4712532 0.95 0.5 0.8726 55.11160099 11.3438595 1.05 0.5 0.8726 49.86287709 12.2164659 1.066667 0.5 0.8726 49.08376963 13.08901725 1.1 0.5 0.8726 47.59638267 13.96161758 0.55 0.25 0.4363 47.59638267 14.39791788 0.5 0.25 0.4363 52.35602094 14.83421824 0.6 0.25 0.4363 43.63001745 15.27051861 0.616667 0.25 0.4363 42.45082779 15.70681896 0.583333 0.25 0.4363 44.87658938 16.14311926 0.5 0.25 0.4363 52.35602094 16.57941962 0.6 0.25 0.4363 43.63001745 17.01571995 0.55 0.25 0.4363 47.59638267 17.452011030 0.583333 0.25 0.4363 44.87658938 17.888311063 0.55 0.25 0.4363 47.59638267 18.324611099 0.6 0.25 0.4363 43.63001745 18.760911135 0.6 0.25 0.4363 43.63001745 19.197211172 0.616667 0.25 0.4363 42.45082779 19.633511208 0.6 0.25 0.4363 43.63001745 20.06981

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1247 0.65 0.25 0.4363 40.27386226 20.506111283 0.6 0.25 0.4363 43.63001745 20.942411322 0.65 0.25 0.4363 40.27386226 21.378711360 0.633333 0.25 0.4363 41.33370074 21.815011395 0.583333 0.25 0.4363 44.87658938 22.251311433 0.633333 0.25 0.4363 41.33370074 22.687611473 0.666667 0.25 0.4363 39.26701571 23.123911512 0.65 0.25 0.4363 40.27386226 23.560211550 0.633333 0.25 0.4363 41.33370074 23.996511590 0.666667 0.25 0.4363 39.26701571 24.432811631 0.683333 0.25 0.4363 38.30928362 24.869111670 0.65 0.25 0.4363 40.27386226 25.305411714 0.733333 0.25 0.4363 35.69728701 25.741711753 0.65 0.25 0.4363 40.27386226 26.178011793 0.666667 0.25 0.4363 39.26701571 26.61431


Elapsed time(min)


Depth of water(cm)

Infiltration rate

(cm/hr)


(cm)

1834 0.683333 0.25 0.4363 38.30928362 27.050611883 0.816667 0.25 0.4363 32.0547067 27.486911930 0.783333 0.25 0.4363 33.41873677 27.923211955 0.416667 0.25 0.4363 62.82722513 28.359511996 0.683333 0.25 0.4363 38.30928362 28.795812034 0.633333 0.25 0.4363 41.33370074 29.232112078 0.733333 0.25 0.4363 35.69728701 29.668412121 0.716667 0.25 0.4363 36.52745647 30.104712170 0.816667 0.25 0.4363 32.0547067 30.541012230 1 0.25 0.4363 26.17801047 30.977312277 0.783333 0.25 0.4363 33.41873677 31.413612326 0.816667 0.25 0.4363 32.0547067 31.849912380 0.9 0.25 0.4363 29.0866783 32.286212435 0.916667 0.25 0.4363 28.5578296 32.722512488 0.883333 0.25 0.4363 29.63548355 33.158812546 0.966667 0.25 0.4363 27.08070049 33.595112602 0.933333 0.25 0.4363 28.04786836 34.031412655 0.883333 0.25 0.4363 29.63548355 34.467712712 0.95 0.25 0.4363 27.5558005 34.904012770 0.966667 0.25 0.4363 27.08070049 35.340312825 0.916667 0.25 0.4363 28.5578296 35.776612885 1 0.25 0.4363 26.17801047 36.212912940 0.916667 0.25 0.4363 28.5578296 36.649213000 1 0.25 0.4363 26.17801047 37.085513060 1 0.25 0.4363 26.17801047 37.521823120 1 0.25 0.4363 26.17801047 37.958123180 1 0.25 0.4363 26.17801047 38.394423240 1 0.25 0.4363 26.17801047 38.83072

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Table 4. Calculation for site 2


Elapsed time(min)


Depth of water(cm)

Infiltration rate

(cm/hr)


(cm)

43 0.71666667 0.51 0.890052 74.5160112 0.890052356129 1.43333333 0.51 0.890052 37.2580056 1.780104712230 1.68333333 0.51 0.890052 31.72463843 2.670157068302 1.2 0.3 0.52356 26.17801047 3.193717277375 1.21666667 0.3 0.52356 25.81940759 3.717277487459 1.4 0.3 0.52356 22.43829469 4.240837696537 1.3 0.3 0.52356 24.16431736 4.764397906614 1.28333333 0.3 0.52356 24.47813966 5.287958115697 1.38333333 0.3 0.52356 22.70863559 5.811518325778 1.35 0.3 0.52356 23.26934264 6.335078534


Elapsed time(min)


Depth of water(cm)

Infiltration rate

(cm/hr)


(cm)

860 1.36666667 0.3 0.52356 22.98557017 6.858638743942 1.36666667 0.3 0.52356 22.98557017 7.3821989531030 1.46666667 0.3 0.52356 21.4183722 7.9057591621116 1.43333333 0.3 0.52356 21.91647388 8.4293193721212 1.6 0.3 0.52356 19.63350785 8.9528795811309 1.61666667 0.3 0.52356 19.43110056 9.4764397911404 1.58333333 0.3 0.52356 19.84017636 101502 1.63333333 0.3 0.52356 19.23282402 10.523560211608 1.76666667 0.3 0.52356 17.78129013 11.047120421719 1.85 0.3 0.52356 16.98033112 11.570680631831 1.86666667 0.3 0.52356 16.82872102 12.094240841947 1.93333333 0.3 0.52356 16.24842029 12.617801052066 1.98333333 0.3 0.52356 15.83879625 13.141361262184 1.96666667 0.3 0.52356 15.97302334 13.664921472305 2.01666667 0.3 0.52356 15.57699797 14.188481682426 2.01666667 0.3 0.52356 15.57699797 14.712041882552 2.1 0.3 0.52356 14.95886313 15.235602092678 2.1 0.3 0.52356 14.95886313 15.75916232804 2.1 0.3 0.52356 14.95886313 16.282722512930 2.1 0.3 0.52356 14.95886313 16.80628272

Results:

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Fig.1. Plots of accumulated infiltration and average infiltration rate against elapsed time for site 1.

Fig.2. Plot of log of accumulated infiltration against log of elapsed time for site 1.

For site 1:

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Now from the figure 2. we get, .

This is same as straight line equation .

So, here m = 0.7199 and c = 0.3599.

The equation is .

So, log k = c =0.3599.

k = 2.29.

a = 0.7199 = 0.72.

The Kostiakov equation is

Fig.3. Plots of accumulated infiltration and average infiltration rate against elapsed time for site 2.

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Fig.4. Plot of log of accumulated infiltration against log of elapsed time for site 2.

For site 2:

Now from the figure 4. we get, .

This is same as straight line equation .

So, here m = 0.7158 and c = 0.0141.

The equation is .

So, log k = c =0.0141.

k = 1.033.

a = 0.7158 = 0.72.

The Kostiakov equation is

Conclusions:

From the above experiment we can conclude:

1)

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lab infiltration test

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