Calculator for water content of soil by pycnometer

Pycnometer method

Determination of Water content of soil solids by pycnometer method

Aim:

To determine the water content of soil solids by pycnometer bottle Method. To determine water content by this method, the value of G should have been determined prior.

Specification:

This test is done as per IS: 2720 (Part II)-1973. This method is suitable for coarse grained soils from which the entrapped air can be easily removed.

Equipments Required:

• Pycnometer of 1000 ml capacity with a brass conical cap.
• Balance accurate to 1 gm.
• Glass rod other accessories.

Theory:

A Pycnometer is a glass jar of about 1 liter capacity, fitted with a brass conical cap by means of a screw type cover. The cap has a small hole of about 6mm diameter at its apex. For many soils, the water content may be an extremely important index used for establishing the relationship between the way a soil behaves and its properties. The consistency of a fine-grained soil largely depends on its water content. The water content is also used in expressing the phase relationships of air, water, and solids in a given volume of soil.Water content, ω of a soil mass is defined as the ratio of mass of water in the voids to the mass of solids. Equation for specific gravity, ω is

\[\omega = \left[ {\left[ {\frac{{\left( {\mathop W\nolimits_2 - \mathop W\nolimits_1 } \right)}}{{\left( {\mathop W\nolimits_3 - \mathop W\nolimits_4 } \right)}} \times \left( {\frac{{G - 1}}{G}} \right)} \right] - 1} \right] \times 100\% \]

Where,

• W₁ = Weight of empty pycnometer in grams.
• W₂ = Weight of pycnometer + wet soil in grams.
• W₃ = Weight of pycnometer + dry soil in grams.
• W₄ = Weight of pycnometer + water in grams.

Procedure:

1. Clean and dry the pycnometer and weigh it (W₁ in gm).
2. Select a mass of wet soil of about 300 gm and place the same in pycnometer and weigh it (W₂ in gm).
3. Fill the pycnometer with distilled water up-to half its height and stir the mix with a glass rod. Keep on adding more water till the mix is flush with the hole in the conical cap. Dry the pycnometer outside and find the mass (W₃ in gm).
4. Remove the contents of PM and clean it. Fill with clean water up-to the top level of the hole in the cap weigh it (W₄ in gm).
5. Now use the above equation for determining water content, where, G value is taken from Experiment " determination of specific gravity by pycnometer method " for the given soil.

Table:

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Weight of empty pycnometer (W1), gm
2.	Weight of pycnometer + wet soil (W2), gm
3.	Weight of pycnometer + soil + water (W3), gm
4.	Weight of pycnometer + water (W4), gm
5.	Specific gravity, G
6.	Water content, ω ( % )
7.	Average ω ( % ) = (ω1+ω2+ω3)/3

Result:

Average, ω=

Verification/ Validation:

Soil mass is generally a three phase system. It consists of solid particles, liquid and gas. The phase system may be expressed in SI units either in terms of massvolume or weight volume relationships. Water content value is 0% for dry soil and its magnitude can exceed 100%.

Conclusion:

Pycnometer method is a simple method to determine the water content of a soil. Experiment is carried out using the soil specimen collected from the college itself. All foreign matters are removed, clods broken and water content we got for the soil specimen is ________. Comparing with the oven drying method, the value is _________.

Viva Questions:

1. A pycnometer is used to determine ?
2. Other than pycnometer, is there any other method to determine water Content ?
3. Which method is more accurate to determine water content, oven drying method or pycnometer method ?
4. If there are lots of clods in the soil, what would happen to the result ?
5. Is it advisable to have lots of organic matter in the soil ?
6. Explain the procedure to determine the water content using pycnometer ?
7. Draw the schematic diagram of the three phase system based on the result.
8. Is there a possibility of error by this method ? In that case, what need to be done ?
9. Which method gives the water content value rapidly, pycnometer method or oven drying method ?

Determination of Water content of soil solids by pycnometer method

Aim:

To determine the water content of soil solids by pycnometer bottle Method. To determine water content by this method, the value of G should have been determined prior.

Specification:

This test is done as per IS: 2720 (Part II)-1973. This method is suitable for coarse grained soils from which the entrapped air can be easily removed.

Equipments Required:

• Pycnometer of 1000 ml capacity with a brass conical cap.
• Balance accurate to 1 gm.
• Glass rod other accessories.

Theory:

A Pycnometer is a glass jar of about 1 liter capacity, fitted with a brass conical cap by means of a screw type cover. The cap has a small hole of about 6mm diameter at its apex. For many soils, the water content may be an extremely important index used for establishing the relationship between the way a soil behaves and its properties. The consistency of a fine-grained soil largely depends on its water content. The water content is also used in expressing the phase relationships of air, water, and solids in a given volume of soil.Water content, ω of a soil mass is defined as the ratio of mass of water in the voids to the mass of solids. Equation for specific gravity, ω is

\[\omega = \left[ {\left[ {\frac{{\left( {\mathop W\nolimits_2 - \mathop W\nolimits_1 } \right)}}{{\left( {\mathop W\nolimits_3 - \mathop W\nolimits_4 } \right)}} \times \left( {\frac{{G - 1}}{G}} \right)} \right] - 1} \right] \times 100\% \]

Where,

• W₁ = Weight of empty pycnometer in grams.
• W₂ = Weight of pycnometer + wet soil in grams.
• W₃ = Weight of pycnometer + dry soil in grams.
• W₄ = Weight of pycnometer + water in grams.

Procedure:

1. Clean and dry the pycnometer and weigh it (W₁ in gm).
2. Select a mass of wet soil of about 300 gm and place the same in pycnometer and weigh it (W₂ in gm).
3. Fill the pycnometer with distilled water up-to half its height and stir the mix with a glass rod. Keep on adding more water till the mix is flush with the hole in the conical cap. Dry the pycnometer outside and find the mass (W₃ in gm).
4. Remove the contents of PM and clean it. Fill with clean water up-to the top level of the hole in the cap weigh it (W₄ in gm).
5. Now use the above equation for determining water content, where, G value is taken from Experiment " determination of specific gravity by pycnometer method " for the given soil.

Table:

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Weight of empty pycnometer (W1), gm	230	240	250
2.	Weight of pycnometer + wet soil (W2), gm	600	615	620
3.	Weight of pycnometer + soil + water (W3), gm	2148	2145	2144
4.	Weight of pycnometer + water (W4), gm	1932	1948	1957
5.	Specific gravity, G	2.65
6.	Water content, ω ( % )
7.	Average ω ( % ) = (ω1+ω2+ω3)/3

Result:

Average, ω=%.

Verification/ Validation:

Soil mass is generally a three phase system. It consists of solid particles, liquid and gas. The phase system may be expressed in SI units either in terms of massvolume or weight volume relationships. Water content value is 0% for dry soil and its magnitude can exceed 100%.

Conclusion:

Pycnometer method is a simple method to determine the water content of a soil. Experiment is carried out using the soil specimen collected from the college itself. All foreign matters are removed, clods broken and water content we got for the soil specimen is%. Comparing with the oven drying method, the value is %.

1. First video

2. Second video

3. Third video

Refrence

1. Venkataramaiah, C. (2018). Geotechnical Engineering (6th ed.). New Age International Publishers Pvt Ltd.

2. Punmia, B.C( 2017)Soil mechanics and foundations(17th ed.).Laxmi publications Pvt Ltd.

3. Gopal R, Rao, A, S, R( 2016)Basic and applied Soil mechanics(3rd ed.).New Age International Publishers Pvt Ltd.