Construction is passion

Construction of a structure either it is house or public property, it gives complete satisfaction once if we start the work and complete in time as per our plan.

Our Thoughts can be modified into reality only through Construction.

Whatever the design appear in our thought, it is possible to implement to create the same with only few basic fundamentals.

Dream, Dream, Dream.

At last Create your reality show which appeared in your dream.

Cement, Wood, Steel, Aluminium or any material can be used as you think, i.e. as you design to create your dream world.

Possible.  Everything is possible.

Be Positive.

Thank You

DETAILS OF PLASTICITY INDEX, LIQUID LIMIT AND PLASTIC LIMIT OF SOIL

Plasticity Index

The plasticity index (PI) is a measure of the plasticity of a soil. The plasticity index is the size of the range of water contents where the soil exhibits plastic properties. The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL). Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 (non-plastic) tend to have little or no silt or clay.

PI and their meanings

·         (0-3)- Non plastic

·         (3-15) - Slightly plastic

·         (15-30) - Medium plastic

·         >30 - Highly plastic.

Plasticity Index

To Calculate the plasticity index as follows: PI = LL ‑ PL where:

LL = liquid limit, and PL = plastic limit.

Liquid limit

The liquid limit (LL) is conceptually defined as the water content at which the behavior of a clayey soil changes from plastic to liquid. However, the transition from plastic to liquid behavior is gradual over a range of water contents, and the shear strength of the soil is not actually zero at the liquid limit. The precise definition of the liquid limit is based on standard test procedures described below.

The original liquid limit test of Atterberg's involved mixing a pat of clay in a round-bottomed porcelain bowl of 10–12 cm diameter. A groove was cut through the pat of clay with a spatula, and the bowl was then struck many times against the palm of one hand. Casagrande subsequently standardized the apparatus and the procedures to make the measurement more repeatable. Soil is placed into the metal cup portion of the device and a groove is made down its center with a standardized tool of 13.5 millimetres (0.53 in) width. The cup is repeatedly dropped 10 mm onto a hard rubber base at a rate of 120 blows per minute, during which the groove closes up gradually as a result of the impact. The number of blows for the groove to close is recorded. The moisture content at which it takes 25 drops of the cup to cause the groove to close over a distance of 13.5 millimetres (0.53 in) is defined as the liquid limit. The test is normally run at several moisture contents, and the moisture content which requires 25 blows to close the groove is interpolated from the test results. The Liquid Limit test is defined by ASTM standard test method D 4318.^[3] The test method also allows running the test at one moisture content where 20 to 30 blows are required to close the groove; then a correction factor is applied to obtain the liquid limit from the moisture content.^[4]

Another method for measuring the liquid limit is the fall cone test, also called the cone penetrometer test. It is based on the measurement of penetration into the soil of a standardized cone of specific mass. Although the Casagrande test is widely used across North America, the fall cone test is much more prevalent in Europe due to being less dependent on the operator in determining the Liquid Limit.

Plastic limit

The plastic limit (PL) is determined by rolling out a thread of the fine portion of a soil on a flat, non-porous surface. The procedure is defined in ASTM Standard D 4318. If the soil is at a moisture content where its behavior is plastic, this thread will retain its shape down to a very narrow diameter. The sample can then be remoulded and the test repeated. As the moisture content falls due to evaporation, the thread will begin to break apart at larger diameters. The plastic limit is defined as the moisture content where the thread breaks apart at a diameter of 3.2 mm (about 1/8 inch). A soil is considered non-plastic if a thread cannot be rolled out down to 3.2 mm at any moisture.

Thank You

PLASTICITY INDEX, LIQUID LIMIT AND PLASTIC LIMIT OF SOIL

Plasticity Index

The plasticity index (PI) is a measure of the plasticity of a soil. The plasticity index is the size of the range of water contents where the soil exhibits plastic properties. The PI is the difference between the liquid limit and the plastic limit (PI = LL-PL). Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 (non-plastic) tend to have little or no silt or clay.

PI and their meanings

·         (0-3)- Non plastic

·         (3-15) - Slightly plastic

·         (15-30) - Medium plastic

·         >30 - Highly plastic.

Plasticity Index

To Calculate the plasticity index as follows: PI = LL ‑ PL where:

LL = liquid limit, and PL = plastic limit.

Liquid limit

The liquid limit (LL) is conceptually defined as the water content at which the behavior of a clayey soil changes from plastic to liquid. However, the transition from plastic to liquid behavior is gradual over a range of water contents, and the shear strength of the soil is not actually zero at the liquid limit. The precise definition of the liquid limit is based on standard test procedures described below.

The original liquid limit test of Atterberg's involved mixing a pat of clay in a round-bottomed porcelain bowl of 10–12 cm diameter. A groove was cut through the pat of clay with a spatula, and the bowl was then struck many times against the palm of one hand. Casagrande subsequently standardized the apparatus and the procedures to make the measurement more repeatable. Soil is placed into the metal cup portion of the device and a groove is made down its center with a standardized tool of 13.5 millimetres (0.53 in) width. The cup is repeatedly dropped 10 mm onto a hard rubber base at a rate of 120 blows per minute, during which the groove closes up gradually as a result of the impact. The number of blows for the groove to close is recorded. The moisture content at which it takes 25 drops of the cup to cause the groove to close over a distance of 13.5 millimetres (0.53 in) is defined as the liquid limit. The test is normally run at several moisture contents, and the moisture content which requires 25 blows to close the groove is interpolated from the test results. The Liquid Limit test is defined by ASTM standard test method D 4318.^[3] The test method also allows running the test at one moisture content where 20 to 30 blows are required to close the groove; then a correction factor is applied to obtain the liquid limit from the moisture content.^[4]

Another method for measuring the liquid limit is the fall cone test, also called the cone penetrometer test. It is based on the measurement of penetration into the soil of a standardized cone of specific mass. Although the Casagrande test is widely used across North America, the fall cone test is much more prevalent in Europe due to being less dependent on the operator in determining the Liquid Limit.

Plastic limit

The plastic limit (PL) is determined by rolling out a thread of the fine portion of a soil on a flat, non-porous surface. The procedure is defined in ASTM Standard D 4318. If the soil is at a moisture content where its behavior is plastic, this thread will retain its shape down to a very narrow diameter. The sample can then be remoulded and the test repeated. As the moisture content falls due to evaporation, the thread will begin to break apart at larger diameters. The plastic limit is defined as the moisture content where the thread breaks apart at a diameter of 3.2 mm (about 1/8 inch). A soil is considered non-plastic if a thread cannot be rolled out down to 3.2 mm at any moisture.

Thank You

Few soil Tests in Civil Works

PERMEABILITY TEST

A. CONSTANT HEAD

OBJECTIVE

To determine the coefficient of permeability of a soil using constant head method.

need and Scope

The knowledge of this property is much useful in solving problems involving yield of water bearing strata, seepage through earthen dams, stability of earthen dams, and embankments of canal bank affected by seepage, settlement etc.

 Planning and organization

1.      Preparation of the soil sample for the test

2.      Finding the discharge through the specimen under a particular head of water.     

Definition of coefficient of permeability

The rate of flow under laminar flow conditions through a unit cross sectional are of porous medium under unit hydraulic gradient is defined as coefficient of permeability. 

Equipment

1.Permeameter mould of non-corrodible material having a capacity of 1000 ml, with an internal diameter of 100 0.1 mm and internal effective height of 127.3,  0.1 mm.

2.The mould shall be fitted with a detachable base plate and removable extension counter.

3.Compacting equipment: 50 mm diameter circular face, weight 2.76 kg and height of fall 310 mm as specified in I.S 2720 part VII 1965.

4.Drainage bade: A bade with a porous disc, 12 mm thick which has the permeability 10 times the expected permeability of soil.

5.Drainage cap: A porous disc of 12 mm thick having a fitting for connection to water inlet or outlet.

6.Constant head tank: A suitable water reservoir capable of supplying water to the permeameter under constant head.

7. Graduated glass cylinder to receive the discharge.

8. Stop watch to note the time.

9.A meter scale to measure the head differences and length of specimen.

 Preparation of Specimen for testing

A. Undisturbed Soil Sample

1.Note down the sample number, bore hole number and its depth at which the sample was taken.

2.Remove the protective cover (paraffin wax) from the sampling tube.

3.Place the sampling tube in the sample extraction frame, and push the plunger to get a cylindrical form sample not longer than 35 mm in diameter and having height equal to that of mould.

4.The specimen shall be placed centrally over the porous disc to the drainage base.

5.The angular space shall be filled with an impervious material such as cement slurry or wax, to provide sealing between the soil specimen and the mould against leakage from the sides.

6.The drainage cap shall then be fixed over the top of the mould.

7.Now the specimen is ready for the test. 

Disturbed Soil Sample

1.A 2.5 kg sample shall be taken from a thoroughly mixed air dried or oven dried material.

2.The initial moisture content of the 2.5 kg sample shall be determined. Then the soil shall be placed in the air tight container.

3.Add required quantity of water to get the desired moisture content.

4.Mix the soil thoroughly.

5.Weigh the empty permeameter mould.

6.After greasing the inside slightly, clamp it between the compaction base plate and extension collar.

7.Place the assembly on a solid base and fill it with sample and compact it.

8.After completion of a compaction the collar and excess soil are removed.

9.Find the weight of mould with sample.

10.Place the mould with sample in the permeameter, with drainage base and cap having discs that are properly saturated.

 Test Procedure

1.For the constant head arrangement, the specimen shall be connected through the top inlet to the constant head reservoir.

2.Open the bottom outlet.

3.Establish steady flow of water.

4.The quantity of flow for a convenient time interval may be collected.

5.Repeat three times for the same interval.

 Observation and Recording

The flow is very low at the beginning, gradually increases and then stands constant. Constant head permeability test is suitable for cohesionless soils. For cohesive soils falling head method is suitable.

 Computation

Coefficient of permeability for a constant head test is given by

Presentation of data

The coefficient of permeability is reported in cm/sec at 27^o C. The dry density, the void ratio and the degree of saturation shall be reported.The test results should be tabulated as below:

 Permeability Test Record

Project:
Tested By: 

Location:
Boring No. : 

Depth: 

 Details of sample

Diameter of specimen                               ..cm

Length of specimen(L)                              ..cm

Area of specimen (A)                             ..cm²

Specific gravity of soil G_s                          ..

Volume of specimen (V)                         ..cm³

Weight of dry specimen (W_s)                  .gm

Moisture content                                     .%

Experiment No.		1	2	3
Length of specimen	L(cm)
Area of specimen	A(cm2)
Time t	(sec)
Discharge	q(cm3)
Height of water	h(cm)
Temperature	(o C)

Interpretation and Reporting

b.� Falling Head Method

Objective

To determine the coefficient of permeability of the given soil sample, using falling head method.

 Need and scope

The test results of the permeability experiments are used:

1.To estimate ground water flow.

2.To calculate seepage through dams.

3.To find out the rate of consolidation and settlement of structures.

4.To plan the method of lowering the ground water table.

5.To calculate the uplift pressure and piping.

6.To design the grouting.

7.And also for soil freezing tests.

8.To design pits for recharging.

�Thus the study of seepage of water through soil is very important, with wide field applications.

�The falling head method of determining permeability is used for soil with low discharge, where as the constant head permeability test is used for coarse-grained soils with a reasonable discharge in a given time. For very fine-grained soil, capillarity permeability test is recommended.

 Principle of the Experiment

� The passage of water through porous material is called seepage. A material with continuous voids is called a permeable material. Hence permeability is a property of a porous material which permits passage of fluids through inter connecting conditions.

� Hence permeability is defined as the rate of flow of water under laminar conditions through a unit cross-sectional area perpendicular to the direction of flow through a porous medium under unit hydraulic gradient and under standard temperature conditions.

�The principle behind the test is Darcy�s law for laminar flow. The rate of discharge is proportional to (i x A)

q= kiA

where q= Discharge per unit time.

� A=Total area of c/s of soil perpendicular to the direction of flow.

� i=hydraulic gradient.

 k=Darcys coefficient of permeability =The mean velocity of flow that will occur through the cross-sectional area under unit hydraulic gradient.

 Planning and Organization

The tools and accessories needed for the test are:

1.Permeameter with its accessories.

2.Standrd soil specimen.

3.Deaires water.

4.Balance to weigh up to 1 gm.

5.I.S sieves 4.75 mm and 2 mm.

6.Mixing pan.

7.Stop watch.

8.Measuring jar.

9.Meter scale.

10.Thermometer.

11.Container for water.

12. Trimming knife etc.

 Knowledge of Equipment

(a)    The permeameter is made of non-corrodible material with a capacity of 1000 ml, with an internal diameter of 100,  0.1 mm and effective height of 127.3 ,  0.1 mm.

(b)   The mould has a detachable base plate and a removable exterior collar.

(c)    The compacting equipment has a circular face with 50 mm diameter and a length of 310 mm with a weight of 2.6 kg.

(d)   The drainage base is a porous disc, 12 mm thick with a permeability 10 times that of soil.

(e)    The drainage cap is also a porous disc of 12 mm thickness with an inlet/outlet fitting.

(f)     The container tank has an overflow valve. There is also a graduated jar to collect discharge.

(g)    The stand pipe arrangements are done on a board with 2 or 3 glass pipes of different diameters.

Preparation of the Specimen

The preparation of the specimen for this test is important. There are two types of specimen, the undisturbed soil sample and the disturbed or made up soil sample.

 A. Undisturbed soil specimen

It is prepared as follows:

1. Note down-sample no., borehole no., depth at which sample is taken.

2.Remove the protective cover (wax) from the sampling tube.

3.Place the sampling tube in the sample extract or and push the plunger to get a cylindrical shaped specimen not larger than 85 mm diameter and height equal to that of the mould.

4.This specimen is placed centrally over the drainage disc of base plate.

5.The annular space in between the mould and specimen is filled with an impervious material like cement slurry to block the side leakage of the specimen.

6.Protect the porous disc when cement slurry is poured.

7.Compact the slurry with a small tamper.

8.The drainage cap is also fixed over the top of the mould.

9.The specimen is now ready for test.

B. Disturbed Specimen

The disturbed specimen can be prepared by static compaction or by dynamic compaction.

 (a)Preparation of statically Compacted (disturbed) specimen.

1.Take 800 to 1000 gms of representative soil and mix with water to O.M.C determined by I.S Light Compaction test. Then leave the mix for 24 hours in an airtight container.

2.Find weight �W� of soil mix for the given volume of the mould and hence find the dry

3.Now, assemble the permeameter for static compaction. Attach the 3 cm collar to the bottom end of 0.3 liters mould and the 2 cm collar to the top end. Support the mould assembly over 2.5 cm end plug, with 2.5 cm collar resting on the split collar kept around the 2.5 cm- end plug. The inside of the 0.3 lit. Mould is lightly greased.

4.Put the weighed soil into the mould. Insert the top 3 cm �end plug into the top collar, tamping the soil with hand.

5.Keep, now the entire assembly on a compressive machine and remove the split collar. Apply the compressive force till the flange of both end plugs touch the corresponding collars. Maintain this load for 1 mt and then release it.

6.Then remove the top 3 cm plug and collar place a filter paper on fine wire mesh on the top of the specimen and fix the perforated base plate.

7.Turn the mould assembly upside down and remove the 2.5 cm end plug and collar. Place the top perforated plate on the top of the soil specimen and fix the top cap on it, after inserting the seating gasket.

8.Now the specimen is ready for test. 

(b) Preparation of Dynamically Compacted Disturbed sample:

1.Take 800 to 1000 gms of representative soil and mix it with water to get O.M.C, if necessary. Have the mix in airtight container for 24 hours.

2.Assemble the permeameter for dynamic compaction. Grease the inside of the mould and place it upside down on the dynamic compaction base. Weigh the assembly correct to a gram (w). Put the 3 cm collar to the other end.

3.Now, compact the wet soil in 2 layers with 15 blows to each layer with a 2.5 kg dynamic tool. Remove the collar and then trim off the excess. Weigh the mould assembly with the soil (W₂).

4.Place the filter paper or fine wore mesh on the top of the soil specimen and fix the perforated base plate on it.

5.Turn the assembly upside down and remove the compaction plate. Insert the sealing gasket and place the top perforated plate on the top of soil specimen. And fix the top cap.

6.Now, the specimen is ready for test.

 Experimental Procedure

1.Prepare the soil specimen as specified.

2.sturate it. Deaired water is preferred.

3.assemble the permeameter in the bottom tank and fill the tank with water.

4.Inlet nozzle of the mould is connected to the stand pipe. Allow some water to flow until steady flow is obtained.

5.Note down the time interval �t� for a fall of head in the stand pipe �h�.

6.Repeat step 5 three times to determine �t� for the same head.

7.Find �a� by collecting �q� for the stand pipe. weigh it correct to 1 gm and find �a� from q/h=a.

Therefore the coefficient of permeability

Observation and Recording:

	1st set	2nd set
1.Area of stand pipe (dia. 5 cm)�a 2.Cross sectional area of soil specimen� A 3.Length of soil specimen L 4.Initial reading of stand pipe h1 5.Final reading of stand pipe h2 6.Time:   t 7.Test temperature:  T 8.Coefficient of permeability at T 9.Coefficient of permeability at 27o C27

                                    

General Remarks:

1.      During test there should be no volume change in the soil, there should be no compressible air present in the voids of soil i.e. soil should be completely saturated. The flow should be laminar and in a steady state condition.

      2.  Coefficient of permeability is used to assess drainage characteristics of soil, to predict rate of settlement founded on soil bed.

Thank You

Relative density of given coarse grained material

OBJECTIVE

To determine the relative density of given coarse grained material.

 PLANNING AND ORGANISATION

Cushioned steel vibrating deck 75�75 cm size, R.P.M : 3600 ; under a 115 kg load, 440V, 3 phase supply.

Two cylindrical metallic moulds, 3000 cc and 15000 cc.

10 mm thick surcharge base plate with handle separately for each mould. Surcharge weights, one for each size having a weight equal to 140 gms / sq.cm.

Dial gauge holder, which can be slipped into the eyelets on the moulds sides.

Guide sleeves with clamps for each mould separately.

Calibration bar 75�300�3 mm.

DEFINITIONS

Relative density or density index is the ratio of the difference between the void ratios of a cohesionless soil in its loosest state and existing natural state to the difference between its void ratio in the loosest and densest states.

Where,

e_max = void ratio of coarse grained soil ( cohesionless) in its loosest state.

e_min = void ratio of coarse grained soil ( cohesionless) in its densest state.

e =� void ratio of coarse grained soil ( cohesionless) in its natural existing state  in the field.

THEORY

Porosity of a soil depends on the shape of grain, uniformity of grain size and condition of sedimentation. Hence porosity itself does not indicate whether a soil is in loose or dense state. This information can only be obtained by comparing the porosity or void ratio of the given soil with that of the same soil in its loosest and densest possible state and hence the term, relative density is introduced.

Relative density is an arbitrary character of sandy deposit. In real sense, relative density expresses the ratio of actual decrease in volume of voids in a sandy soil to the maximum possible decrease in the volume of voids i.e how far the sand under investigation can be capable to the further densification beyond its natural state. Determination of relative density is helpful in compaction of coarse grained soils and in evaluating safe bearing capacity in case of sandy soils.

For very dense gravelly sand, it is possible to obtain relative density greater the one. This means that such natural dense packing could not be obtained in the laboratory.

 PROCEDURE

�Calibration of mould :

1. Measure inside diameter of mould at different depths using a bore gauge and take the����

average.

2. Keep the mould on a flat surface or flat plate. Measure the height at different positions and take the average (accuracy = 0.025 mm).

3. Calculate the volume.

4. Fill the mould with distilled water till over flowing takes place.

5. Slid thick glass plate over the top surface of mould.

6. Weigh the water filling the mould.

7. Note the temperature of water.

8. Obtain density of water for the above temperature from physical tables.

9. Calculate the volume of the mould which is weight of water filling the mould /density of water.

Preparation of the Sample:

1. Dry the soil sample in a thermostatically controlled electric oven.

2. Cool in the sample in a desicator.

3. Segregate soil lumps with out breaking individual particles

4. Sieve it through the required sieve size.

 Minimum Density:

The mould is weighed accurately (W). Pour the dry pulverized soil into the mould through a funnel in a steady stream. The spout is adjusted so that the free fall of soil particle is always 25 mm. While pouring soil the spout must have a spiral motion from the rim to the centre. The process is continued to fill up the mould with soil upto about 25mm above the top. It is then leveled, with the soil and weight is recorded (W₁).

      ����������������������������������

Maximum Density:

Weigh the empty mould (W). Put the collar on top of� the mould and clamp it. Fill the mould with the oven dried soil sample till 1 / 2� or 2 / 3� of the collar is filled. Place the mould on the vibrating deck and fix it with nuts and bolts. Then place the surcharge weight on it. The vibrator is allowed to run for 8 minutes. Then mould is weighed with the soil and weight is recorded (W₂).

Natural Density:

Weigh the mould with dry soil. Knowing the volume of the mould and weight of dry soil natural density, g_d, can be calculated.

Thank You

SIEVE ANALYSIS

GRAIN SIZE DISTRIBUTION

I.SIEVE ANALYSIS

OBJECTIVE

(a). Select sieves as per I.S specifications and perform sieving.
(b). Obtain percentage of soil retained on each sieve.
(c). Draw graph between log grain size of soil and % finer.

NEED AND SCOPE OF EXPERIMEN
The grain size analysis is widely used in classification of soils. The data obtained from grain size distribution curves is used in the design of filters for earth dams and to determine suitability of soil for road construction, air field etc. Information obtained from grain size analysis can be used to predict soil water movement although permeability tests are more generally used.

 PLANNING AND ORGANISATION

Apparatus

1.Balance

2.I.S sieves

����������� 3.Rubber pestle and mortar.

����������� 4.mechanical Sieve Shaker

����������� �The grain size analysis is an attempt to determine the relative proportions of different grain sizes which make up a given soil mass.

KNOWLEDGE OF EQUIPMENT

1.The balance to be used must be sensitive to the extent of 0.1% of total weight of sample taken.

2.I.S 460-1962 are to used. The sieves for soil tests: 4.75 mm to 75 microns.

 PROCEDURE

1.For soil samples of soil retained on 75 micron I.S sieve

(a)    The proportion of soil sample retained on 75 micron I.S sieve is weighed and recorded weight of soil sample is as per I.S 2720.

(b)   I.S sieves are selected and arranged in the order as shown in the table.

(c)    The soil sample is separated into various fractions by sieving through above sieves placed in the above mentioned order.

(d)   The weight of soil retained on each sieve is recorded.

(e)    The moisture content of soil if above 5% it is to be measured and recorded.

2.No particle of soil sample shall be pushed through the sieves.

OBSERVATIONS AND RECORDING

 Weight of soil sample:

Moisture content:

I.S sieve number or size in mm	Wt. Retained in each sieve (gm)	Percentage on each sieve	Cumulative %age retained on each sieve	% finer	Remarks
4.75
4.00
3.36
2.40
1.46
1.20
0.60
0.30
0.15
0.075

GRAPH

Draw graph between log sieve size vs % finer. The graph is known as grading curve. Corresponding to 10%, 30% and 60% finer, obtain diameters from graph are designated as D_10, D_30, D_60.

 CALCULATION

1. The percentage of soil retained on each sieve shall be calculated on the basis of total weight of soil sample taken.
2. Cumulative percentage of soil retained on successive sieve is found.

II.HYDROMETER ANALYSIS

OBJECTIVE

Grain size analysis of soils by hydrometer analysis test. 

SPECIFIC OBJECTIVE

1. To determine the grain size distribution of soil sample containing appreciable amount of fines.

2. To draw a grain size distribution curve.

 NEED AND SCOPE OF THE EXPERIMENT

For determining the grain size distribution of soil sample, usually mechanical analysis (sieve analysis) is carried out in which the finer sieve used is 63 micron or the nearer opening. If a soil contains appreciable quantities of fine fractions in (less than 63 micron) wet analysis is done. One form of the analysis is hydrometer analysis. It is very much helpful to classify the soil as per ISI classification. The properties of the soil are very much influenced by the amount of clay and other fractions.

 APPARATUS

1. Hydrometer

2. Glass measuring cylinder-Two of 1000 ml capacity with ground glass or rubber stoppers������ about 7 cm diameter and 33 cm high marked at 1000 ml volume.

3. Thermometer- To cover the range 0 to 50^o C with an accuracy of�� 0.5 ^o C .
4. Water bath.
5. Stirring apparatus.
6. I.S sieves apparatus.
7. Balance-accurate to 0.01 gm.
8. Oven-105 to 110.
9. Stop watch.
10. Desiccators
11. Centimeter scale.
12. Porcelain evaporating dish.
13. Wide mouth conical flask or conical beaker of 1000 ml capacity.
14. Thick funnel-about 10 cm in diameter.
15. Filter flask-to take the funnel.
16. Measuring cylinder-100 ml capacity.
17. Wash bottle-containing distilled water.
18. Filter papers.
19. Glass rod-about 15 to 20 cm long and 4 to 5 mm in diameter.
20. Hydrogen peroxide-20 volume solution.
21. Hydrochloric acid N solution-89 ml of concentrated hydrochloric acid.(specific gravity 1.18) diluted with distilled water one litre of solution.
22. Sodium hexametaphosphate solution-dissolve 33 g of sodium hexametaphosphate and 7 gms of sodium carbonate in distilled water to make one litre of solution.

 CALIBRATION OF HYDROMETER

Volume

(a) Volume of water displaced: Approximately 800 ml of water shall be poured in the 1000 ml measuring cylinder. The reading of the water level shall be observed and recorded.

The hydrometer shall be immersed in the water and the level shall again be observed and recorded as the volume of the hydrometer bulb in ml plus volume of that part of the stem that is submerged. For practical purposes the error to the inclusion of this stem volume may be neglected.

(b) From the weight of the hydrometer: The hydrometer shall be weighed to the nearest 0.1 gm.

The weight in gm shall be recorded as the volume of the bulb plus the volume of the stem below the 1000 ml graduation mark. For practical purposes the error due to the inclusion of this stem may be neglected.

Calibration

(a ) The sectional area of the 1000 ml measuring cylinder in which the hydrometer is to used shall be determined by measuring the distance between the graduations. The sectional area is equal to the volume include between the two graduations divided by the measured distance between them.

�Place the hydrometer on the paper and sketch it. On the sketch note the lowest and highest readings which are on the hydrometer and also mark the neck of the bulb. Mark the center of the bulb which is half of the distance between neck of the bulb and tip of the bulb.

(b) The distance from the lowest reading to the center of the bulb is (R_h) shall be recorded

(R_h �=H_L + L/2).

(c) The distance from the highest hydrometer reading to the center of the bulb shall be measured and recorded.

(d) Draw a graph hydrometer readings vs H_H and R_H. A straight line is obtained. This calibration curve is used to calibrate the hydrometer readings which are taken with in 2 minutes.

(e) From 4 minutes onwards the readings are to be taken by immersing the hydrometer each time. This makes the soil solution to rise, there by rising distance of free fall of the particle. So correction is applied to the hydrometer readings.

(f) Correction applied to the R_h and H_H

V_h= Volume of hydrometer bulb in ml.

A� =Area of measuring cylinder in cm².

From these two corrected readings draw graph (straight line)

Grain Size Distribution in Soil-Data and Calculation Chart

Date:

Sample No:

Total weight of dry soil taken, W =

Specific Gravity of soil, G =

Hydrometer No.��_____________            � Wt. Of soil gone into solution ,W_s =

Meniscus correction, C_n =������������������������� Dispersion agent correction =

Reading in water RW���� =

Temperature correction�� =

% finer for wt. Of soil W_s gone into solution���� N=[(100G)/{W_s x (G �1)}] x R

Date	Time	Elapsed Time in Sec	Hydrometer reading upper Meniscus Rh � 1000	Corrected hydrometer Reading (1- lower meniscus Cm)	Zr or Zlr	Velocity Cms/sec V=Z�r/K or Zlr / t	Equivalent dia. Of Particle D�mm	R	N(% finer Than for soil)	REMARKS

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HOW TO CALCULATE CBR

CALIFORNIA BEARING RATIO TEST 

OBJECTIVE

To determine the California bearing ratio by conducting a load penetration test in the laboratory. 

NEED AND SCOPE

The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement.

This instruction sheet covers the laboratory method for the determination of C.B.R. of undisturbed and remoulded /compacted soil specimens, both in soaked as well as unsoaked state. 

PLANNING AND ORGANIZATION

Equipments and tool required.

1. Cylindrical mould with inside dia 150 mm and height 175 mm, provided with a detachable extension collar 50 mm height and a detachable perforated base plate 10 mm thick. 

2. Spacer disc 148 mm in dia and 47.7 mm in height along with handle. 

3. Metal rammers. Weight 2.6 kg with a drop of 310 mm (or) weight 4.89 kg a drop 450 mm. 

4. Weights. One annular metal weight and several slotted weights weighing 2.5 kg each, 147 mm in dia, with a central hole 53 mm in diameter. 

5. Loading machine. With a capacity of atleast 5000 kg and equipped with a movable head or base that travels at an uniform rate of 1.25 mm/min. Complete with load indicating device. 

6. Metal penetration piston 50 mm dia and minimum of 100 mm in length. 

7. Two dial gauges reading to 0.01 mm. 

8. Sieves. 4.75 mm and 20 mm I.S. Sieves.

9. Miscellaneous apparatus, such as a mixing bowl, straight edge, scales soaking tank or pan, drying oven, filter paper and containers. 

DEFINITION OF C.B.R.

It is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at the rate of 1.25 mm/min. to that required for the corresponding penetration of a standard material.

C.B.R. = Test load/Standard load � 100

The following table gives the standard loads adopted for different penetrations for the standard material with a C.B.R. value of 100%

Penetration of plunger    (mm)	Standard load    (kg)
2.5 5.0 7.5 10.0 12.5	1370 2055 2630 3180 3600

          The test may be performed on undisturbed specimens and on remoulded specimens which may be compacted either statically or dynamically. 

PREPARATION OF TEST SPECIMEN

Undisturbed specimen

Attach the cutting edge to the mould and push it gently into the ground. Remove the soil from the outside of the mould which is pushed in . When the mould is full of soil, remove it from weighing the soil with the mould or by any field method near the spot.

Determine the density

Remoulded specimen

Prepare the remoulded specimen at Proctor�s maximum dry density or any other density at which C.B.R> is required. Maintain the specimen at optimum moisture content or the field moisture as required. The material used should pass 20 mm I.S. sieve but it should be retained on 4.75 mm I.S. sieve. Prepare the specimen either by dynamic compaction or by static compaction. 

Dynamic Compaction

Take about 4.5 to 5.5 kg of soil and mix thoroughly with the required water.

Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base (See Fig.38). Place the filter paper on the top of the spacer disc.

   Compact the mix soil in the mould using either light compaction or heavy compaction. For light compaction, compact the soil in 3 equal layers, each layer being given 55 blows by the 2.6 kg rammer. For heavy compaction compact the soil in 5 layers, 56 blows to each layer by the 4.89 kg rammer.

Remove the collar and trim off soil.

Turn the mould upside down and remove the base plate and the displacer disc.

Weigh the mould with compacted soil and determine the bulk density and dry density.

Put filter paper on the top of the compacted soil (collar side) and clamp the perforated base plate on to it. 

Static compaction

Calculate the weight of the wet soil at the required water content to give the desired density when occupying the standard specimen volume in the mould from the expression.

                                       W =desired dry density * (1+w) V

Where W = Weight of the wet soil

            w = desired water content

           V = volume of the specimen in the mould = 2250 cm³ (as per the mould available in laboratory)

Take the weight W (calculated as above) of the mix soil and place it in the mould.

Place a filter paper and the displacer disc on the top of soil.

Keep the mould assembly in static loading frame and compact by pressing the displacer disc till the level of disc reaches the top of the mould.

Keep the load for some time and then release the load. Remove the displacer disc.

The test may be conducted for both soaked as well as unsoaked conditions.

If the sample is to be soaked, in both cases of compaction, put a filter paper on the top of the soil and place the adjustable stem and perforated plate on the top of filter paper.

Put annular weights to produce a surcharge equal to weight of base material and pavement expected in actual construction. Each 2.5 kg weight is equivalent to 7 cm construction. A minimum of two weights should be put.

Immerse the mould assembly and weights in a tank of water and soak it for 96 hours. Remove the mould from tank.

Note the consolidation of the specimen. 

Procedure for Penetration Test

Place the mould assembly with the surcharge weights on the penetration test machine. (Fig.39).

Seat the penetration piston at the center of the specimen with the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established.

Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min.

Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm.

Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content. 

Observation and Recording

For Dynamic Compaction

Optimum water content (%)                                                                      

Weight of mould + compacted specimen g                                               

Weight of empty mould g                                                                          

Weight of compacted specimen g                                                              

Volume of specimen cm³                                                                            

Bulk density g/cc                                                                                       

Dry density g/cc                                                                                         

For static compaction

Dry density g/cc

Moulding water content %

Wet weight of the compacted soil, (W)g

Period of soaking 96 hrs. (4days). 

For penetration Test

Calibration factor of the proving ring                                                1 Div. = 1.176 kg

Surcharge weight used (kg)                                                                2.0 kg  per 6 cm construction

Water content after penetration test %

Least count of penetration dial                                                             1 Div. = 0.01 mm 

If the initial portion of the curve is concave upwards, apply correction by drawing a tangent to the curve at the point of greatest slope and shift the origin (Fig. 40). Find and record the correct load reading corresponding to each penetration.

                                         C.B.R. = P_T�/P_S � 100

where P_T = Corrected test load corresponding to the chosen penetration from the load penetration curve.

          P_S = Standard load for the same penetration taken from the table I. 

Penetration Dial	Load Dial	Corrected Load
Readings Penetration (mm)	proving ring reading Load (kg)

Interpretation and recording

C.B.R. of specimen at 2.5 mm penetration                              

C.B.R. of specimen at 5.0 mm penetration           

  C.B.R. of specimen at 2.5 mm penetration      

The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the C.B.R. value at 2.5 mm will be greater that at 5 mm and in such a case/the former shall be taken as C.B.R. for design purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test should be repeated. If identical results follow, the C.B.R. corresponding to 5 mm penetration should be taken for design.

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