Determination of plastic limit of given sample

Determination of plastic limit of the soil

Aim:

To determine plastic limit of the soil. The plastic limit of fine-grained soil is the water content of the soil below which it ceases to be plastic. It begins to crumble when rolled into threads of 3mm dia. Specifications: This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5)-1985. Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for 24hrs.

Specification:

This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5)-1985. Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for 24hrs.

Equipments Required:

• Porcelain evaporating dish.
• Flat glass plate.
• Balance accurate to 0.01g.
• Drying oven, maintained at 110 ± 5°C (230 ± 9°F).
• Weighing dishes, non-absorbent, with lids.
• Flexible spatula, blade approximately 102 mm (4 in.) long x 19mm (0.75 in.) wide.

Theory:

The plastic limit is the moisture content that defines where the soil changes from a semi-solid to a plastic state. It may also be defined as that water content at which soil starts crumbling when rolled into threads of 3mm diameter. Use the paste from liquid limit test and begin drying. May add dry soil or spread on plate and air dry.

Consistency of fine-grained soils may be defined as the relative ease with which a soil can be remoulded. Consistency limits may be categorized into three limits called Atterberg limits. They are 1) Liquid limit 2) Plastic limit and 3) Shrinkage limit Liquid limit is the moisture content that defines where the soil changes from a plastic limit to a viscous fluid state.

Precautions:

• Soil used for plastic limit determination should not be oven dried prior to testing.
• After mixing the water to the soil sample, sufficient time should be given to permeate the water throughout out the soil mass.
• Wet soil taken in the container for moisture content determination should not be left open. The container with soil sample should either be placed in desiccators or immediately be weighed.

Procedure:

1. Select a representative sample of fine-grained soil of about 20 g or more passing through 420 micron IS sieve. Mix it with distilled water thoroughly on a glass plate such that the palm of the soil can be rolled into a thread of 3 mm diameter. Allow some time for the proper distribution mixed with water.
2. Take about 10 g of this wet sail and roll it into a thread on a glass plate with the palm of the hand. The rolling must be such that it forms a uniform thread of 3 mm diameter. If the thread cracks before attaining 3 mm diameter, and add little more water, knead it and roll again.
3. the rolling can be done to diameter less than 3mm, mix some dry soil, knead it to remove same extra moisture in the soil. This process has to continue till the sample crumbles just at about 3 mm diameter. Collect the crumbled soil (at least 6 g) and measure its water content.
4. Repeat the process to get at least three water content determination (after they have been in the oven at least 16 hours).
5. The average of water content so obtained is the plastic limit of the soil.

Table: water content of 3mm soil

Trials No.	Test No.1	Test No.2	Test No.3	Test No.4
Weight of container (W1), gm
Weight of container + wet soil (W2), gm
Weight of container + dry soil (W3), gm
Water content, ω=(W2-W3)/(W3-W1)
Average ω = (ω1+ω2+ω3+ω4)/4
Liquid limit, LL =

Result:

The Plastic limit of soil (average water content) is, PL_______________.

Plasticity index = LL - PL = ______________%

Verification/ Validation:

Determine the plasticity index Ip, which is the difference between liquid limit and plastic limit. Following table list the standard values:

Table:

Soil Type.	Wl	Wp	Ip
Sand	-	-	Non-plastic
Silt	30-40	20-25	10-15
Clay	40-150	25-50	15-100

Conclusion:

The plastic limit of the soil = ____

plasticity index = ____.

The type of soil is _____.

Viva Questions:

1. How is plastic limit computed in laboratory ?
2. What is the practical significance of determining plastic limit of the soil ?
3. What is plasticity index ?
4. What is toughness index ?
5. What is meant by unified soil classification ?
6. What is liquidity index and consistency index ?
7. What is A-line and U-line ?

Aim:

To determine plastic limit of the soil. The plastic limit of fine-grained soil is the water content of the soil below which it ceases to be plastic. It begins to crumble when rolled into threads of 3mm dia. Specifications: This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5)-1985. Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for 24hrs.

Specification:

This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5)-1985. Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Mix the soil with distilled water in an evaporating dish and leave the soil mass for 24hrs.

Equipments Required:

• Porcelain evaporating dish.
• Flat glass plate.
• Balance accurate to 0.01g.
• Drying oven, maintained at 110 ± 5°C (230 ± 9°F).
• Weighing dishes, non-absorbent, with lids.
• Flexible spatula, blade approximately 102 mm (4 in.) long x 19mm (0.75 in.) wide.

Theory:

The plastic limit is the moisture content that defines where the soil changes from a semi-solid to a plastic state. It may also be defined as that water content at which soil starts crumbling when rolled into threads of 3mm diameter. Use the paste from liquid limit test and begin drying. May add dry soil or spread on plate and air dry.

Consistency of fine-grained soils may be defined as the relative ease with which a soil can be remoulded. Consistency limits may be categorized into three limits called Atterberg limits. They are 1) Liquid limit 2) Plastic limit and 3) Shrinkage limit Liquid limit is the moisture content that defines where the soil changes from a plastic limit to a viscous fluid state.

Precautions:

• Soil used for plastic limit determination should not be oven dried prior to testing.
• After mixing the water to the soil sample, sufficient time should be given to permeate the water throughout out the soil mass.
• Wet soil taken in the container for moisture content determination should not be left open. The container with soil sample should either be placed in desiccators or immediately be weighed.

Procedure:

1. Select a representative sample of fine-grained soil of about 20 g or more passing through 420 micron IS sieve. Mix it with distilled water thoroughly on a glass plate such that the palm of the soil can be rolled into a thread of 3 mm diameter. Allow some time for the proper distribution mixed with water.
2. Take about 10 g of this wet sail and roll it into a thread on a glass plate with the palm of the hand. The rolling must be such that it forms a uniform thread of 3 mm diameter. If the thread cracks before attaining 3 mm diameter, and add little more water, knead it and roll again.
3. the rolling can be done to diameter less than 3mm, mix some dry soil, knead it to remove same extra moisture in the soil. This process has to continue till the sample crumbles just at about 3 mm diameter. Collect the crumbled soil (at least 6 g) and measure its water content.
4. Repeat the process to get at least three water content determination (after they have been in the oven at least 16 hours).
5. The average of water content so obtained is the plastic limit of the soil.

Table: water content of 3mm soil

Trials No.	Test No.1	Test No.2	Test No.3	Test No.4
Weight of container (W1), gm	7.78	7.83	15.16	7.83
Weight of container + wet soil (W2), gm	16.39	13.43	21.23	13.43
Weight of container + dry soil (W3), gm	15.28	12.69	20.43	12.69
Water content, ω=(W2-W3)/(W3-W1)
Average ω = (ω1+ω2+ω3+ω4)/4
Liquid limit, LL =	26

Result:

The Plastic limit of soil (average water content), PL is =

Plasticity index = LL - PL =%

Verification/ Validation:

Determine the plasticity index Ip, which is the difference between liquid limit and plastic limit. Following table list the standard values:

Table:

Soil Type.	Wl	Wp	Ip
Sand	-	-	Non-plastic
Silt	30-40	20-25	10-15
Clay	40-150	25-50	15-100

Conclusion:

The plastic limit of the soil =

plasticity index = .

The type of soil is = .

1. First video

2. Second video

3. Third video

Websites and blog

Click on the link below to study about standard proctor test.

1. First blog

2. Second blog

3. Third blog

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.

Determination of liquid limit of given sample

Determination of liquid limit.

Aim:

To determine the liquid limit of soil by using Casagrande Apparatus.

Specification:

This test is done to determine liquid limit of soil as per IS: 2720(Part 5)-1985. After receiving the soil sample it is dried in air or in oven (maintained at a temperature of 60^oC). If clods are there in soil sample then it is broken with the help of wooden mallet. The soil passing 425 micron sieve is used in this test.

Equipments Required:

• A mechanical liquid limit apparatus (casagrande type) with grooving tools.
• Evaporating dishes, wash bottle etc.
• Balance accurate to 0.01 g.
• Airtight container to determine water content.
• Oven to maintain temperature at 105^oC to 110^oC.
• Sieve (425 micron).
• Spatula
• Desiccator and other accessories.

Theory:

When water is added to dry soil, it changes its state of consistency from hard to soft. We can define liquid limit as the minimum water content at which the soil is still in the liquid state, but has a small shearing strength against flow. From test point of view we can define liquid limit as the minimum water content at which a pat of soil cut by a groove of standard dimension will flow together for a distance of 12 mm (1/2 inch) under an impact of 25 blows in the device.

Consistency of fine-grained soils may be defined as the relative ease with which a soil can be remoulded. Consistency limits may be categorized into three limits called Atterberg limits. They are 1) Liquid limit 2) Plastic limit and 3) Shrinkage limit Liquid limit is the moisture content that defines where the soil changes from a plastic to a viscous fluid state. Other limits will be discussed during corresponding experiments.

Precautions:

• Soil used for liquid limit determination should not be oven dried prior to testing.
• In LL test the groove should be closed by the flow of soil and not by slippage between the soil and the cup
• After mixing the water to the soil sample , sufficient time should be given to permeate the water throughout out the soil mass
• Wet soil taken in the container for moisture content determination should not be left open in the air, the container with soil sample should either be placed in desiccators or immediately be weighed.
• After performing each test the cup and grooving tool must be cleaned.
• The number of blows should be just enough to close the groove.
• The number of blows should be between 10 and 40.

Procedure:

1. A representative sample of mass of about 120 gm passing through 425 micron IS sieve is taken for the test. Mix the soil in an evaporating dish with distilled water to form a uniform paste.
2. Adjust the cup of the device so that the fall of the cup on to the hard rubber base is 10 mm.
3. Transfer the portion of the paste to the cup of liquid limit device. Allow some time for the soil to have uniform distribution of water.
4. Level the soil topsoil so that the maximum depth of soil is 12 mm. A channel of 11 mm wide at the top, 2 mm at the bottom and 8 mm deep is cut by the grooving tool. The grooving tool is held normal to the cup and the groove is cut through the sample along the symmetrical axis of the top.
5. The handle of the device is turned at a rate of about 2 revolutions per second and the number of blows necessary to close the groove along the bottom distance of 12 mm is counted. A sample of soil which closes the groove is collected.
6. Another soil sample of same weight has to be taken and above procedure is repeated by taking increaments of percentage of water(2% for gravels and sand, 4% for silt)
7. At least 4 tests should be conducted by adjusting the water contents of the soil in the cup in such a way that the number of blows required to close the groove may fall within the range of 5 to 40 blows. A plot of water content against the log of blows is made as shown in figure. The water content at 25 blows gives the liquid limit.

Table:

Trials No.	Test No.1	Test No.2	Test No.3	Test No.4
Moisture can and lid number
Weight of container (W1), gm
Weight of container + wet soil (W2), gm
Weight of container + dry soil (W3), gm
Water content, ω=(W2-W3)/(W3-W1)
No of blows (N)
Liquid limit, LL =

Verification/ Validation:

If the natural moisture content of soil is closer to liquid limit, the soil can be considered as soft if the moisture content is lesser than liquids limit, the soil is brittle and stiffer. Hence if the points on the graph are obtained scattered, we need to draw the linear curve at the mean.

Table:

Soil Type.	Liquid limit
Sand	-
Silt	30-40
Clay	40-150

Conclusion:

As per the procedure the experiment is carried out. Water content for 25 blows, w = _____%.

Viva Questions:

1. Define consistency of the soil. How is it measured ?
2. What is liquid limit of soil ?
3. What is the apparatus used to determine the liquid limit ?
4. When a soil sample is given, what is the procedure to determine the liquid limit of the sample ?
5. In a liquid limit test, the moisture content at 10 blows was 70% and that at 100 blows was 20%. The liquid limit of the soil, is ?
6. What is the purpose of computing liquid limit of the soil ?
7. With the organic matter in the soil, will the liquid limit increase or decrease ?

Aim:

To determine the liquid limit of fine soil by using Casagrande Apparatus.

Specification:

This test is done to determine liquid limit of soil as per IS: 2720(Part 5)-1985. After receiving the soil sample it is dried in air or in oven (maintained at a temperature of 60^oC). If clods are there in soil sample then it is broken with the help of wooden mallet. The soil passing 425 micron sieve is used in this test.

Equipments Required:

• A mechanical liquid limit apparatus (casagrande type) with grooving tools.
• Evaporating dishes, wash bottle etc.
• Balance accurate to 0.01 g.
• Airtight container to determine water content.
• Oven to maintain temperature at 105^oC to 110^oC.
• Sieve (425 micron).
• Spatula
• Desiccator and other accessories.

Theory:

When water is added to dry soil, it changes its state of consistency from hard to soft. We can define liquid limit as the minimum water content at which the soil is still in the liquid state, but has a small shearing strength against flow. From test point of view we can define liquid limit as the minimum water content at which a pat of soil cut by a groove of standard dimension will flow together for a distance of 12 mm (1/2 inch) under an impact of 25 blows in the device.

Consistency of fine-grained soils may be defined as the relative ease with which a soil can be remoulded. Consistency limits may be categorized into three limits called Atterberg limits. They are 1) Liquid limit 2) Plastic limit and 3) Shrinkage limit Liquid limit is the moisture content that defines where the soil changes from a plastic to a viscous fluid state. Other limits will be discussed during corresponding experiments.

Precautions:

• Soil used for liquid limit determination should not be oven dried prior to testing.
• In LL test the groove should be closed by the flow of soil and not by slippage between the soil and the cup
• After mixing the water to the soil sample , sufficient time should be given to permeate the water throughout out the soil mass
• Wet soil taken in the container for moisture content determination should not be left open in the air, the container with soil sample should either be placed in desiccators or immediately be weighed.
• After performing each test the cup and grooving tool must be cleaned.
• The number of blows should be just enough to close the groove.
• The number of blows should be between 10 and 40.

Procedure:

1. A representative sample of mass of about 120 gm passing through 425 micron IS sieve is taken for the test. Mix the soil in an evaporating dish with distilled water to form a uniform paste.
2. Adjust the cup of the device so that the fall of the cup on to the hard rubber base is 10 mm.
3. Transfer the portion of the paste to the cup of liquid limit device. Allow some time for the soil to have uniform distribution of water.
4. Level the soil topsoil so that the maximum depth of soil is 12 mm. A channel of 11 mm wide at the top, 2 mm at the bottom and 8 mm deep is cut by the grooving tool. The grooving tool is held normal to the cup and the groove is cut through the sample along the symmetrical axis of the top.
5. The handle of the device is turned at a rate of about 2 revolutions per second and the number of blows necessary to close the groove along the bottom distance of 12 mm is counted. A sample of soil which closes the groove is collected.
6. Another soil sample of same weight has to be taken and above procedure is repeated by taking increaments of percentage of water(2% for gravels and sand, 4% for silt)
7. At least 4 tests should be conducted by adjusting the water contents of the soil in the cup in such a way that the number of blows required to close the groove may fall within the range of 5 to 40 blows. A plot of water content against the log of blows is made as shown in figure. The water content at 25 blows gives the liquid limit.

Table:

Trials No.	Test No.1	Test No.2	Test No.3	Test No.4
Moisture can and lid number	1	4	2	6
Weight of container (W1), gm	22.23	23.31	21.87	22.58
Weight of container + wet soil (W2), gm	28.56	29.27	25.73	25.22
Weight of container + dry soil (W3), gm	27.40	28.10	24.90	24.60
Water content, ω=(W2-W3)/(W3-W1)
No of blows (N)	31	29	20	14
Liquid limit, LL =

Verification/ Validation:

If the natural moisture content of soil is closer to liquid limit, the soil can be considered as soft if the moisture content is lesser than liquids limit, the soil is brittle and stiffer. Hence if the points on the graph are obtained scattered, we need to draw the linear curve at the mean.

Table:

Soil Type.	Liquid limit
Sand	-
Silt	30-40
Clay	40-150

Conclusion:

As per the procedure the experiment is carried out. Water content for 25 blows, ω = %.

1. First video

2. Second video

3. Third video

Websites and blog

Click on the link below to study about standard proctor test.

1. First blog

2. Second blog

3. Third blog

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.

Determination of dry density and optimum moisture content by Standard proctor test

Standard proctor compaction method

Determination of maximum dry density and optimum moisture content.

Aim:

To determine the optimum content and maximum dry density of a soil sample by standard proctor test.

Specification:

The experiment is conducted as per IS 2720-7(1980).

Equipments Required:

• Proctor mould having a capacity of 1000cc with an internal diameter of 100mm and effective height of 127.3mm. The mould shall have a detachable collar assembly and detachable base plate.
• Rammer: A mechanical operated metal rammer of weight of 2.6Kg , drop of 310mm. The rammer shall be equipped with a suitable arrangement to control the height of drop to free fall.
• Sample extruder.
• Balance of 15Kg capacity.
• Sensitive balance.
• Straight edge.
• Graduate cylinder.
• Mixing tools such as mixing pan, spoon, trowel, and spatula.

Theory:

Compaction is the application of mechanical energy to a soil so as to rearrange its particles and reduce the void ratio. It is applied to improve the properties of an existing soil or in the process of placing fill such as in the construction of embankments, road bases, runways, earth dams, and reinforced earth walls. Compaction is also used to prepare a level surface during construction of buildings. There is usually no change in the water content and in the size of the individual soil particles.

The objectives of compaction are:

1. To increase soil shear strength and therefore its bearing capacity.
2. To reduce subsequent settlement under working loads.
3. To reduce soil permeability making it more difficult for water to flow through To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

Precautions:

• Thoroughly breakup the sample by running it through the screen before compacting it in the mould.
• Pound within a moisture range from optimum to 4 percent below optimum. The closer to optimum the moisture content is, the more accurate the test will be.
• Make sure the clamp on each mold section is tight.
• Make sure the wing nuts on the base plate are secured with equal tension.
• Place the mould on a solid block that is supported on firm soil or pavement.
• Hold the rammer vertically so that it will fall freely.
• Drop the 25 kg rammer weight freely
• Use exactly 25 blows on each layer.
• Place 3 equal layers in the mold

Procedure:

1. Take a representative oven-dried sample, approximately 3Kg in the given pan. Thoroughly mix sample with sufficient water to dampen it to approximately four to six percentage below optimum moisture content.
2. Weigh the proctor mould with base plate (W₁). Fix the collar and base plate. Place the soil in the proctor mould and compact it in three layers giving 25 blows per layer with the 2.6 Kg rammer falling through a height of 310mm.
3. Remove the collar, trim the compacted soil evenly with the top of the mould by means of straight edge and weigh.
4. Divide the weight of the compacted specimen and record the result as the wet weight (γ_wet )gms/ cm³ of the compacted soil.
5. Remove the sample from the mould and slice vertically through and obtain a small sample for moisture determination.
6. Thoroughly break up the remainder of the material and add water in sufficient amounts to increase the moisture content of the soil sample by one or two percentage. Finally, repeat the above procedure for each increment of water added.
7. Plot a graph between water content (w) and maximum dry density (γ_dry )gms/cm³ which exhibits optimum moisture content (OMC).
8. Continue this series of determination until there is either a decrease or no change in the wet unit weight of the compacted soil.

Observation:

Height of mould ( H ) = _____________.

Diameter mould ( d ) = _______________.

Volume of mould (V) =(πd²)/4 x H= ______________.

Table: Weight of Soil for varying water content

Serial No.	Details	Test No.1	Test No.2	Test No.3	Test No.4
1.	Weight of mould with base plate and collar (W1), kg
2.	Weight of mould + compacted soil (W2), kg
3.	Weight of compacted soil (W), gm
4.	Wet density (γ)=w/v, g/cm3
5.	Container
6.	Weight of container (W3), gm
7.	Weight of container + wet soil (W4), gm
8.	Weight of container + dry soil (W5), gm
9.	Water content (Wc)=(Ww)/(Wd)=(W4-W5)/(W5-W3)
10.	Average Water content, Wc=(Wc1+Wc2+Wc3+Wc4)/4
11.	Dry density, γdry = γ/(1+wc), g/cm3

Result:

Optimum moisture content (OMC) = ______________%

Maximum dry density (γ_max )gms/cm³ = ______________%.

Verification/ Validation:

The peak point of the compaction curve - The peak point of the compaction curve is the point with the maximum dry density dry density. Corresponding to the maximum dry density ρ_dmax is a water content known as the optimum water content.The optimum water content is the water content that results in the greatest density for a specified compactive effort. Compacting at water contents higher than the optimum. water content results in a relatively dispersed soil structure (parallel particle orientations) that is weaker , more ductile, less pervious, softer, more susceptible to shrinking, and less susceptible to swelling than soil compacted dry of optimum to the same density.

Zero air voids curve: The curve represents the fully saturated condition (S = 100 %). (It cannot be reached by compact ion)

Conclusion:

The maximum density of the soil is ______ with an OMC of _______. This indicates, after w%, any additional water addition, there is no gain in strength of soil.

Viva Questions:

1. What is the difference between standard proctor test and modified proctor test ?
2. What is relative density of soil ?
3. What is voids ratio? What is zero air voids line ?
4. What is the practical implication of conducting standard proctor test ?
5. How to determine OMC of soil? Explain.
6. How is compaction different from consolidation ?
7. Did you watch any civil engineering construction compaction is carried out? Explain.
8. Is there any other method other than standard proctor test to determine maximum density ?

Determination of maximum dry density and optimum moisture content.

Aim:

To determine the optimum content and maximum dry density of a soil sample by standard proctor test.

Specification:

The experiment is conducted as per IS 2720-7(1980).

Equipments Required:

• Proctor mould having a capacity of 1000cc with an internal diameter of 100mm and effective height of 127.3mm. The mould shall have a detachable collar assembly and detachable base plate.
• Rammer: A mechanical operated metal rammer of weight of 2.6Kg , drop of 310mm. The rammer shall be equipped with a suitable arrangement to control the height of drop to free fall.
• Sample extruder.
• Balance of 15Kg capacity.
• Sensitive balance.
• Straight edge.
• Graduate cylinder.
• Mixing tools such as mixing pan, spoon, trowel, and spatula.

Theory:

Compaction is the application of mechanical energy to a soil so as to rearrange its particles and reduce the void ratio. It is applied to improve the properties of an existing soil or in the process of placing fill such as in the construction of embankments, road bases, runways, earth dams, and reinforced earth walls. Compaction is also used to prepare a level surface during construction of buildings. There is usually no change in the water content and in the size of the individual soil particles.

The objectives of compaction are:

1. To increase soil shear strength and therefore its bearing capacity.
2. To reduce subsequent settlement under working loads.
3. To reduce soil permeability making it more difficult for water to flow through To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

Precautions:

• Thoroughly breakup the sample by running it through the screen before compacting it in the mould.
• Pound within a moisture range from optimum to 4 percent below optimum. The closer to optimum the moisture content is, the more accurate the test will be.
• Make sure the clamp on each mold section is tight.
• Make sure the wing nuts on the base plate are secured with equal tension.
• Place the mould on a solid block that is supported on firm soil or pavement.
• Hold the rammer vertically so that it will fall freely.
• Drop the 25 kg rammer weight freely
• Use exactly 25 blows on each layer.
• Place 3 equal layers in the mold

Procedure:

1. Take a representative oven-dried sample, approximately 3Kg in the given pan. Thoroughly mix sample with sufficient water to dampen it to approximately four to six percentage below optimum moisture content.
2. Weigh the proctor mould with base plate (W₁). Fix the collar and base plate. Place the soil in the proctor mould and compact it in three layers giving 25 blows per layer with the 2.6 Kg rammer falling through a height of 310mm.
3. Remove the collar, trim the compacted soil evenly with the top of the mould by means of straight edge and weigh.
4. Divide the weight of the compacted specimen and record the result as the wet weight (γ_wet )gms/ cm³ of the compacted soil.
5. Remove the sample from the mould and slice vertically through and obtain a small sample for moisture determination.
6. Thoroughly break up the remainder of the material and add water in sufficient amounts to increase the moisture content of the soil sample by one or two percentage. Finally, repeat the above procedure for each increment of water added.
7. Plot a graph between water content (w) and maximum dry density (γ_dry )gms/cm³ which exhibits optimum moisture content (OMC).
8. Continue this series of determination until there is either a decrease or no change in the wet unit weight of the compacted soil.

Observation:

Height of mould ( H ) = mm.

Diameter mould ( d ) = mm.

Volume of mould (V) =(πd²)/4 x H= cm³.

Table: Weight of Soil for varying water content

Serial No.	Details	Test No.1	Test No.2	Test No.3	Test No.4
1.	Weight of mould with base plate and collar (W1), kg	3.894	3.893	3.894	3.891
2.	Weight of mould + compacted soil (W2), kg	5.268	6.062	6.014	5.950
3.	Weight of compacted soil (W), gm
4.	Wet density (γ)=w/v, g/cm3
5.	Container	4	15	11	23
6.	Weight of container (W3), gm	26	18	18	26
7.	Weight of container + wet soil (W4), gm	46	34	38	46
8.	Weight of container + dry soil (W5), gm	44	32	36	44
9.	Water content (Wc)=(Ww)/(Wd)=(W4-W5)/(W5-W3)
10.	Average Water content, Wc=(Wc1+Wc2+Wc3+Wc4)/4
11.	Dry density, γdry = γ/(1+wc), g/cm3

Result:

Optimum moisture content (OMC) = % .

Maximum dry density (γ_max ) = gms/cm³ .

Verification/ Validation:

The peak point of the compaction curve - The peak point of the compaction curve is the point with the maximum dry density dry density. Corresponding to the maximum dry density ρ_dmax is a water content known as the optimum water content.The optimum water content is the water content that results in the greatest density for a specified compactive effort. Compacting at water contents higher than the optimum. water content results in a relatively dispersed soil structure (parallel particle orientations) that is weaker , more ductile, less pervious, softer, more susceptible to shrinking, and less susceptible to swelling than soil compacted dry of optimum to the same density.

Zero air voids curve: The curve represents the fully saturated condition (S = 100 %). (It cannot be reached by compact ion)

Conclusion:

The maximum density of the soil is with an OMC of . This indicates, after w%, any additional water addition, there is no gain in strength of soil.

1. First video

2. Second video

3. Third video

Websites and blog

Click on the link below to study about standard proctor test.

1. First blog

2. Second blog

3. Third blog

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.

Geotechnical engineering laboratory | JNTUA R20 civil engineering

Jawaharlal nehru technological university anantapur (Established by Govt. of A.P., ACT No.30 of 2008)

ANANTAPUR-515 002 (A.P) INDIA

Syllabus of Geotechnical engineering laboratory.

JNTUA subject code : 20A01502P

Credit : 1.5

Course Structure : R20

Civil engineering

Year : Third 3-1 (III-I)

List of Experiments :

Experiment 1 : Moisture content of soil.

Determination of moisture content of soil by oven drying method.

Experiment 2 : Specific gravity of soil.

Determination of specific gravity of soil by pycnometer method.

Experiment 3 : Atterberg's Limits : Liquid limit.

Determination of liquid limit of given soil sample.

Experiment 4 : Atterberg's Limits : Plastic limit.

Determination of plastic limit of given soil sample.

Experiment 5 : Field density by sand replacement method.

Determination of field density by sand replacement method

Experiment 6 : Field density by Core cutter method.

Determination of field density by Core cutter method.

Experiment 7 : Grain size analysis by sieving.

Experiment 8 : Standard proctor compaction test.

Experiment 9 : Modified proctor compaction test.

Experiment 10 : Vane Shear test.

List of textbooks:

1. Soil Mechanics and Foundation Engg by K. R. Arora, Standard Publishers and Distributors, Delhi 7th edition 2009.
2. Geotechnical Engineering by C. Venkataramiah, New age International Pvt . Ltd, (2002).

Reference Books :

1. Soil Mechanics and Foundation by B. C. Punmia, Ashok Kumar Jain and Arun Kumar Jain, Laxmi publications Pvt. Ltd., New Delhi 17th edition 2017.
2. Basic and Applied Soil Mechanics by Gopal Ranjan & A. S. R. Rao, New age International Pvt . Ltd, New Delhi 3rd edition 2016.
3. Principles of Geotechnical Engineering by Braja M. Das Cengage Learning.

Course objective :

1. The object of the course is to enable the students to know the various characteristics of soils.
2. To carry out laboratory tests and to identify soil as per IS codal procedures.
3. To perform laboratory tests to determine index properties of soil.
4. To perform tests to determine shear strength.
5. To perform consolidation test to determine the characteristics of soils.

Course outcome :

1. At the end of the course, the student must be able to: Identify various soils based on their characteristics.
2. Able to Evaluate permeability and seepage of soils.
3. Determine plasticity characteristics of various soils.
4. To perform tests to determine shear strength.
5. Understand the consolidation process and thereby predicting the settlement of soils.

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DETERMINATION OF IN-SITU DENSITY BY SAND REPLACEMENT METHOD

In-situ density by sand replacement method

Determination of in-situ density by sand replacement method

Aim:

To determine in-situ density of natural or compacted soil using Sand replacement method.

Specification:

This test is done to determine the in-situ dry density of soil by core cutter method as per IS-2720-Part-28 (1975). In order to conduct the test, select uniformly graded clean sand passing through 600µ and retained on 300µ IS sieve.

Equipments Required:

• Sand pouring cylinder of about 3 litre capacity (Small pouring cylinder as per IS 2720 Part 28).
• Cylindrical calibrating container 10 cm internal diameter and 15 cm depth
• Glass plate, trays, containers for determining water content.
• Tools for making of a hole of 10 cm diameter and 15 cm deep, knife and other accessories.
• Metal container to collect excavated soil.
• Metal tray, 300mm square and 40mm deep with a hole of 100mm in diameter at the centre.
• Weighing balance.
• Moisture content cans.
• Glass plate about 450 mm/600 mm square and 10mm thick.
• Oven.
• Dessicator.

Theory:

The in-situ density of natural soil is needed for the determination of bearing capacity of soils, for the purpose of stability analysis of slopes, for the determination of pressures on underlying strata for the calculation of settlement and the design of underground structures. Moreover, dry density values are relevant both of embankment design as well as pavement design.

By conducting this test, it is possible to determine the field density of the soil. The moisture content is likely to vary from time and hence the field density also. So it is required to report the test result in terms of dry density. In sand replacement method, a small cylindrical pit is excavated and the weight of the soil excavated from the pit is measured. Sand whose density is known is filled into the pit. By measuring the weight of sand required to fill the pit and knowing its density, the volume of pit is calculated. Knowing the weight of soil excavated from the pit and the volume of pit, the density of soil is calculated. Therefore, in this experiment there are two stages, namely

1. Calibration of sand density.
2. Measurement of soil density.

Field density is defined as weight per unit volume of soil mass in the field at in-situ conditions. Equations are:

\[\mathop \rho \nolimits_d = \frac{{\mathop \rho \nolimits_t }}{{1 + \omega }}\]

Where,

• γ_d = Dry unit weight in g/cm³.
• γ_t = Field moist unit weight in g/cm³.
• ω = Water content in ( Percentage % ).

The basic equations in determination of density using sand replacement method are:

\[\mathop V\nolimits_h = \frac{{\mathop W\nolimits_s }}{{G \times \mathop \rho \nolimits_w }}\]

\[\mathop \rho \nolimits_t = \frac{W}{{\mathop V\nolimits_h }}\]

Where,

• W_s = weight of the sand that fills the hole.
• W = moisture content of soil removed from the hole.
• ρ_t = moist soil in-situ density.
• G = specific gravity of the solids.
• ρ_w = density of the water.
• V_h = Volume of hole made in the field.

Precautions:

• If for any reason it is necessary to excavate the pit to a depth other than 12 cm, the standard calibrating can should be replaced by one with an internal height same as the depth of pit to be made in the ground.
• Care should be taken in excavating the pit, so that it is not enlarged by levering, as this will result in lower density being recorded.
• No loose material should be left in the pit.
• There should be no vibrations during this test.
• It should not be forgotten to remove the tray, before placing the SPC over the pit.

Procedure:

Calibration of apparatus

1. Soil sample must be taken as air dried sand which is passed through 1mm sieve and retained on 600µ sieve for filling sand pouring cylinder.
2. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is with in about 10mm from the top, find out the initial weight of the cylinder plus sand (W₁) and this weight should be maintained constant throughout the test for which the calibration is used.
3. Allow the sand of volume equal to that of the calibrating container to run out the cylinder on the glass plate and open the shutter to allow the sand to run out and close the cylinder shutter when there is no movement of sand and remove the cylinder carefully. Weigh the sand collected on the glass plate. Its weight (W₂) gives sand filling the cone portion of the sand pouring cylinder.

Determination of bulk density of soil

4. Determine the volume (V) of the container be filled it with water to the brim. Check this volume by calculating from the measured internal dimensions of the container.
5. Place the sand pouring cylinder centrally on the calibrating container making sure that constant weight (W₁) is maintained. Open the shutter and permit the sand to run into container. When no further movement of sand is seen close the shutter. Remove the pouring cylinder and find its mean weight (W₃).

Determination of dry density of soil in field

6. Clean and level the ground where field density is required.
7. Fill the pouring cylinder with dry sand within about 10mm of the top and weigh it.
8. Place the metal tray with the central hole over the soil to be tested.
9. Excavate approximately 10cm diameter and 15cm deep with bend spoon. The hole in the tray will guide the diameter of the hole to be made in the soil.
10. Collect the excavated soil in the metal tray and weigh it (W_w) to nearest gram.
11. Determine the moisture content of excavated soil.
12. Place the pouring cylinder over the hole so that base of the cylinder covers the hole concentrically.
13. Open the shutter and allow the sand to run into the hole, where there is no movement of the sand, close the shutter. Remove the cylinder and determine its mean weight (W₃).

Table: Caliberation of appratus and calculate bulk density

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Internal diameter of calibrating cylinder (cm)
2.	Internal height of calibrating cylinder (cm)
3.	Cross sectional area of calibrating cylinder (cm2)
4.	Volume of calibrating cylinder (Vc), cm3
5.	Weight of cylinder + sand (before pouring) (W1), gm
6.	Weight of cylinder + sand (after pouring) (W2), gm
7.	Mean weight of sand in cone (W3), gm
8.	Weight of sand to fill the calibrating cylinder (Wa), gm
9.	Bulk density of sand (γb),=Wa/Vc,(g/cm3)

Table: Determination of dry density

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Weight of wet sand from hole (Ww), gm
2.	Weight of cylinder + sand (before pouring) (W1), gm
3.	Weight of cylinder + sand (after pouring) (W4), gm
4.	Mean weight of sand in hole (Ws), gm
5.	Volume of calibrating cylinder (Vc), cm3
6.	Bulk density (γb),=Wa/Vc,(g/cm3)
8.	Average (γb) = (γb1+γb2+γb3)/3
7.	Dry density (γd)=γt/1+ω,(g/cm3)
8.	Average (γd) = (γd1+γd2+γd3)/3

Table: Measurement of water content

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Moisture content container No.
2.	Weight of empty container(W5), gm
3.	Weight of container + wet soil (W6), gm
4.	Weight of container + dry soil (W7), gm
5.	Water content ω=(W6-W7)/(W7-W5)
8.	Average (%W) = (%W1+%W2+%W3)/3

Result:

The Bulk density of soil is ___________.

The Water content of soil is ___________.

The Dry density of soil is ___________.

Verification/ Validation:

Sand replacement method is an indirect method of finding the density of soil. The basic principle is to measure the in-situ volume of hole from which the material was excavated from the weight of sand with known density filling in the hole. The in-situ density of material is given by the weight of the excavated material divided by the in-situ volume. The dry density of most soils varies within the range of 1.1-1.6 gm/cm³. In sandy soils, dry density can be as high as 1.6 gm/cm³. In clayey soils and aggregated loams, it can be as low as 1.1 gm/cm³.

Conclusion:

The value of dry density of the soil is ______________ g/cm³.Comparing with the in-situ density by core cutter method, more or less the same value is achieved. The type of soil is ____________ .

Viva Questions:

1. What is the objective of sand replacement method ?
2. What is the relationship that can be established between the dry density with known moisture content ?
3. What are the apparatus that are needed in this test ?
4. What is the significance of determining the in-situ density of the soil ?
5. Why Depth of hole is kept to 15 cm in the field ?
6. Why we need to determine the unit weight of sand to determine the unit weight of soil?
7. Which method is the accurate one, core cutter or sand replacement method as per you? And why?
8. How many samples are to be collected ?
9. What is the advantage of sand replacement method over core cutter method ?
10. What is the practical application of the test ?

Determination of in-situ density by sand replacement method

Aim:

To determine in-situ density of natural or compacted soil using Sand replacement method.

Specification:

This test is done to determine the in-situ dry density of soil by core cutter method as per IS-2720-Part-28 (1975). In order to conduct the test, select uniformly graded clean sand passing through 600µ and retained on 300µ IS sieve.

Equipments Required:

• Sand pouring cylinder of about 3 litre capacity (Small pouring cylinder as per IS 2720 Part 28).
• Cylindrical calibrating container 10 cm internal diameter and 15 cm depth
• Glass plate, trays, containers for determining water content.
• Tools for making of a hole of 10 cm diameter and 15 cm deep, knife and other accessories.
• Metal container to collect excavated soil.
• Metal tray, 300mm square and 40mm deep with a hole of 100mm in diameter at the centre.
• Weighing balance.
• Moisture content cans.
• Glass plate about 450 mm/600 mm square and 10mm thick.
• Oven.
• Dessicator.

Theory:

The in-situ density of natural soil is needed for the determination of bearing capacity of soils, for the purpose of stability analysis of slopes, for the determination of pressures on underlying strata for the calculation of settlement and the design of underground structures. Moreover, dry density values are relevant both of embankment design as well as pavement design.

By conducting this test, it is possible to determine the field density of the soil. The moisture content is likely to vary from time and hence the field density also. So it is required to report the test result in terms of dry density. In sand replacement method, a small cylindrical pit is excavated and the weight of the soil excavated from the pit is measured. Sand whose density is known is filled into the pit. By measuring the weight of sand required to fill the pit and knowing its density, the volume of pit is calculated. Knowing the weight of soil excavated from the pit and the volume of pit, the density of soil is calculated. Therefore, in this experiment there are two stages, namely

1. Calibration of sand density.
2. Measurement of soil density.

Field density is defined as weight per unit volume of soil mass in the field at in-situ conditions. Equations are:

\[\mathop \rho \nolimits_d = \frac{{\mathop \rho \nolimits_t }}{{1 + \omega }}\]

Where,

• γ_d = Dry unit weight in g/cm³.
• γ_t = Field moist unit weight in g/cm³.
• ω = Water content in ( Percentage % ).

The basic equations in determination of density using sand replacement method are:

\[\mathop V\nolimits_h = \frac{{\mathop W\nolimits_s }}{{G \times \mathop \rho \nolimits_w }}\]

\[\mathop \rho \nolimits_t = \frac{W}{{\mathop V\nolimits_h }}\]

Where,

• W_s = weight of the sand that fills the hole.
• W = moisture content of soil removed from the hole.
• ρ_t = moist soil in-situ density.
• G = specific gravity of the solids.
• ρ_w = density of the water.
• V_h = Volume of hole made in the field.

Precautions:

• If for any reason it is necessary to excavate the pit to a depth other than 12 cm, the standard calibrating can should be replaced by one with an internal height same as the depth of pit to be made in the ground.
• Care should be taken in excavating the pit, so that it is not enlarged by levering, as this will result in lower density being recorded.
• No loose material should be left in the pit.
• There should be no vibrations during this test.
• It should not be forgotten to remove the tray, before placing the SPC over the pit.

Procedure:

Calibration of apparatus

1. Soil sample must be taken as air dried sand which is passed through 1mm sieve and retained on 600µ sieve for filling sand pouring cylinder.
2. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is with in about 10mm from the top, find out the initial weight of the cylinder plus sand (W₁) and this weight should be maintained constant throughout the test for which the calibration is used.
3. Allow the sand of volume equal to that of the calibrating container to run out the cylinder on the glass plate and open the shutter to allow the sand to run out and close the cylinder shutter when there is no movement of sand and remove the cylinder carefully. Weigh the sand collected on the glass plate. Its weight (W₂) gives sand filling the cone portion of the sand pouring cylinder.

Determination of bulk density of soil

4. Determine the volume (V) of the container be filled it with water to the brim. Check this volume by calculating from the measured internal dimensions of the container.
5. Place the sand pouring cylinder centrally on the calibrating container making sure that constant weight (W₁) is maintained. Open the shutter and permit the sand to run into container. When no further movement of sand is seen close the shutter. Remove the pouring cylinder and find its mean weight (W₃).

Determination of dry density of soil in field

6. Clean and level the ground where field density is required.
7. Fill the pouring cylinder with dry sand within about 10mm of the top and weigh it.
8. Place the metal tray with the central hole over the soil to be tested.
9. Excavate approximately 10cm diameter and 15cm deep with bend spoon. The hole in the tray will guide the diameter of the hole to be made in the soil.
10. Collect the excavated soil in the metal tray and weigh it (W_w) to nearest gram.
11. Determine the moisture content of excavated soil.
12. Place the pouring cylinder over the hole so that base of the cylinder covers the hole concentrically.
13. Open the shutter and allow the sand to run into the hole, where there is no movement of the sand, close the shutter. Remove the cylinder and determine its mean weight (W₃).

Table: Caliberation of appratus and calculate bulk density

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Internal diameter of calibrating cylinder (cm)	10	10	10
2.	Internal height of calibrating cylinder (cm)	15	15	15
3.	Cross sectional area of calibrating cylinder (cm2)
4.	Volume of calibrating cylinder (Vc), cm3
5.	Weight of cylinder + sand (before pouring) (W1), gm	11040	11040	11040
6.	Weight of cylinder + sand (after pouring) (W2), gm	9120	9120	9120
7.	Mean weight of sand in cone (W3), gm	450	450	450
8.	Weight of sand to fill the calibrating cylinder (Wa), gm
9.	Bulk density of sand (γb),=Wa/Vc,(g/cm3)

Table: Determination of dry density

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Weight of wet sand from hole (Ww), gm	2310	2400	2280
2.	Weight of cylinder + sand (before pouring) (W1), gm	11040	11040	11040
3.	Weight of cylinder + sand (after pouring) (W4), gm	9120	9120	9120
4.	Mean weight of sand in hole (Ws), gm
5.	Volume of calibrating cylinder (Vc), cm3
6.	Bulk density (γb),=Wa/Vc,(g/cm3)
8.	Average (γb) = (γb1+γb2+γb3)/3
7.	Dry density (γd)=γt/1+ω,(g/cm3)
8.	Average (γd) = (γd1+γd2+γd3)/3

Table: Measurement of water content

Sl.No	Particulars	Test No.1	Test No.2	Test No.3
1.	Moisture content container No.	45	21	25
2.	Weight of empty container(W5), gm	18	18	18
3.	Weight of container + wet soil (W6), gm	74	74	74
4.	Weight of container + dry soil (W7), gm	64	64	64
5.	Water content ω=(W6-W7)/(W7-W5)
8.	Average (%W) = (%W1+%W2+%W3)/3

Result:

The Bulk density of soil is .

The Water content of soil is

The Dry density of soil is

Verification/ Validation:

Sand replacement method is an indirect method of finding the density of soil. The basic principle is to measure the in-situ volume of hole from which the material was excavated from the weight of sand with known density filling in the hole. The in-situ density of material is given by the weight of the excavated material divided by the in-situ volume. The dry density of most soils varies within the range of 1.1-1.6 gm/cm³. In sandy soils, dry density can be as high as 1.6 gm/cm³. In clayey soils and aggregated loams, it can be as low as 1.1 gm/cm³.

Conclusion:

The value of dry density of the soil is g/cm³.Comparing with the in-situ density by core cutter method, more or less the same value is achieved. The type of soil is .

1. First video

2. Second video

3. Third video

Blogs

1. First blog

2. Second blog

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.