1.0 OBJECTIVE

Determine the in situ density of natural or compacted soils using sand pouring cylinders.

2.0 LEARNING OUTCOME

At the end of this experiment, students are able to:

Understand the relationship between compaction effort and the density of soil on site.

Obtain the in situ density of natural soil and compacted soil.

3.0 THEORY

Sometimes it is important to know the density of in-situ for design purpose. This can be done by mean of sand replacement method. Determining the in situ density of natural or compacted soils using sand pouring cylinders requires simple method of analysis. 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. This along with the Core Cutter is one of the older, more labor intensive methods of determining density. It is used on boulder clays and granular fills.

SAND CONE EQUIPMENTS

4.0 TEST EQUIPMENTS

1. Sand pouring cylinder of 3 litre/16.5 litre capacity, mounted above a pouring cone and separated by a shutter cover plate.

2. Tools for excavating holes; suitable tools such as scraper tool to make a level surface.

3. Cylindrical calibrating container with an internal diameter of 100 mm/200 mm and an internal depth of 150 mm/250 mm fitted with a flange 50 mm/75 mm wide and about 5 mm thick surrounding the open end.

4. Balance to weigh unto an accuracy of I g.

5. Metal containers to collect excavated soil.

6. Metal tray with 300 mm/450 mm square and 40 mm/50 mm deep with a 100 rnm/200 mm diameter hole in the centre.

7. Suitable non-corrodible airtight containers.

8. Thermostatically controlled oven with interior on non-corroding material to maintain the temperature between 105°C to llO°C.

9. Glass plate about 450 mm/600 mm square and 10mm thick.

10. MATERIAL : Clean, uniformly graded natural sand passing through 1.00 mm IS. Sieve and retained on the 600micron I.S.sieve. It shall be free from organic matter and shall have been oven dried and exposed to atmospheric humidity.

11. A dessicator with any desiccating agent other than sulphuric acid.

5.0 PROCEDURE

5.1 Calibration of the cylinder

1. The internal dimensions of the calibrating container are measured and its volume is determined.

2. The clean uniformly graded standard sand are filled in the sand pouring cylinder up to a height of 1 cm below the top with the shutter closed. Initial mass of the sand, M1 is

founded. The mass should be maintained constant throughout the test for which the calibration is used.

3. The sand of volume equal to that of the calibrating container is allowed to run out of the cylinder by opening the shutter. The stutter is closed.

4. The sand cone-pouring cylinder is placed on a paper placed on a horizontal table. The shutter is opened again and allows the sand to flow and fill the cone.

5. The shutter is closed. The mass of sand in cylinder after pouring, M3 is determined.

6. The mass of sand on paper, M2 is calculated too.

5.2 Determination of bulk density of sand

1. The internal dimensions of the calibrating container and volume, Vc is measured and

been converted to unit given.

2. The sand-pouring cylinder concentrically is placed on the top of the calibrating container with the shutter is closed making sure that constant mass, M1 is maintained.

3. The shutter of cylinder is opened and allows the sand to move into the container. When no further movement is seen, close the shutter and find the mass of sand left in the cylinder, M3.

Measure mass of calibrating containerInsert 15kg sand into container and

determine mass

Sand left in cylinder after pouringSand in cone

5.3 Determination of field density of soil

1. Surface of the soil in the open field is leveled where only soil part is taken to consideration.

2. The metal tray is placed on the surface haring a circular hole of 10 cm diameter at the centre. A hole of this diameter up to about 15 cm depth is dogged and all the excavated soil in a tray is collected to find the mass of excavated soil, Mw.

3. The tray is removed and placed the sand-pouring cylinder concentrically on the hole. The shutter is opened to allow the sand to run into hole till no further movement of sand is noticed. Then, close the shutter and mass of sand which is left in the cylinder, M5.is determined.

4. The representative sample is taken from the excavated soil for determination of water content.

Determine mass sand in cone

In fields

holes need to be in a match excavated soil to put in the tray

Sand in the arbitration

dig a hole

Insert 15kg sand into container Open the shutter and allow the sand to run into hole till

Sand run into hole tillsand in the filter

6.0 RESULT AND CALCULATION

Data Analysis

A) Determination of Mass of sand in the cone

Volume of calibrating container (Vc) Ml 17.67Mass of sand in cylinder before pouring ( Mo) g 15000Mean mass of sand in cone ( M1 ) g 1225

B) Determination of bulk density of sand

Mean mass of sand left in cylinder after pouring (M2) g 9355Mass of sand filling calibrating container, Mc=Mo-M1-M2

g 4420

Bulk density of sand Ps = Mc/Vc g/cm3 250x10-4

C) Bulk density and unit weight of soil

Mass of wet soil from hole, M g 5851Mass of sand in cylinder after pouring, M3 g 11107Mass of sand in the hole Ms =Mo-M1-M3 g 2668Bulk density of soil,P = M/Ms x Ps g/cm3 5.48x10-4

Dry density of soil, Pd = p/ 1+w g/cm3 3.17x10-5

D) Moisture content determination:

Can no. Unit 1Mass of can Kg 0.035Mass of can + wet sample Kg 0.071Mass of can + dry sample Kg 0.065Moisture content % 16.27

Calculation

From the data :

Height of cylinder, H : 20mm

Diameter of cylinder : 150mm

Hence the volume is :

V = πd 2

4

= π( 150) 2

4

= 17.67m3

1. Mass of sand filling calibrating container, Mc

Mc = Mo – Mi – M2

= 15000 g – 1225 g – 9335 g

= 4420 g

2. Bulk density of sand, Ps

Ps = Mc

Vc

= 4420 g

17.63 ml

= 4420 g

1.767 X 10 ^ 7 cm3

= 250 x 10 ^ -4 g/cm3

3. Mass of sand in the hole, Ms

Ms = Mo – Mi – M3

= 15000 g – 1225 g – 11107 g

= 2668 g

4. Bulk density of soil, P

P = M x Ps

Ms

= 5851 g x ( 250 x 10-4)

2668 g

= 5.48 x 10-4 g/cm3

5. Dry density of soil, Pd

Pd = p

1 + w

= 5.48 x 10 -4

1+ 16.27

= 3.17 x 10-5

7.0 QUESTIONS

1.Field engineers are often found talking of optimum moisture content (OMC) conditions while constructing of road sub-grade. Define and explain this term, bringing out clearly the importance it posses and the methods by which it is controlled.

Field engineers are often found talking of optimum moisture content (OMC) conditions while constructing of sub- grade. When the values of the dry density and moisture content are plotted the resulting curve has a peak value of dry density. The corresponding moisture content is known as the optimum moisture content (OMC). The reason for this is that at low w values the soil is stiff and difficult to compact, resulting in a low dry density with a high void ratio; as w is increased the water lubricates the soil, increasing the workability and producing high dry density and low void ratio, but beyond OMC pore water pressures begin to develop and the water tends to keep the soil particles apart resulting in low dry densities and high void ratios. With all soils an increase in the compactive effort results in an increase in the maximum dry density and a decrease in the optimum moisture content.

Once the ideal moisture content and bulk density are determined in the lab this information can then be used during field compaction of the fill material. Then, field moisture and density is determined. The engineer on site can use this information to determine when field density is 90% of the lab derived value. At this point field compaction may be considered sufficient.

Controlling the moisture content of road sub-grade during construction will reduce the risk of damage to the sub-grade. The stability of unbound pavement materials generally decreases with increasing moisture content or the Degree of Saturation (DOS). The DOS is a measure of the ratio of the volume of water to the combined volume of air voids and water within a material. A material with a DOS of 100% is fully saturated and has a very high pore pressure and high instability under load. As the DOS reduces, the reduction in pore water pressure also reduces with a corresponding increase in stability.

2.Discuss the method of compaction of (a) cohesion less soil (b) cohesive soils.

Soil compaction is defined as the method of mechanically increasing the density of soil. In construction, this is a significant part of the building process. If performed improperly, settlement of the soil could occur and result in unnecessary maintenance costs or structure failure. Almost all types of building sites and construction projects utilize mechanical compaction techniques.

There are five principle reasons to compact soil: Increases load-bearing capacity Prevents soil settlement and frost damage Provides stability Reduces water seepage, swelling and contraction Reduces settling of soil

There are four types of compaction effort on soil or asphalt: Vibration Impact Kneading Pressure

Type Appearance/feel Water movement When moist... When dry...

Granular soils, finesands and silts.

Coarse grains can be seen. Feels grittywhen rubbed between fingers.

When water and soil are shaken in palm of hand, they mix. When shaking is stopped, they separate.

Very little or noplasticity.

Little or no cohesive strength when dry. Soil sample willcrumble easily.

Cohesive soils, mixes and clays.

Grains cannot be seen by eye. Feels smooth and greasywhen rubbed between fingers.

When water and soil are shaken in palm of hand, they will not mix.

Plastic and sticky.Can be rolled.

Has high strengthwhen dry. Crumbles with difficulty. Slowsaturation in water.

The desired level of compaction is best achieved by matching the soil type with its

proper compaction method. Other factors must be considered as well, such as

compaction specs and job site conditions.

8.0 CONCLUSION

After conducting experiments sand fiber method, the data obtained is to determine the density of dry soil. The purpose of this experiment determine the density of natural soil or compacted with sand pouring cylinder. In the course of this experiment, the possibility of experimental error there is in progress. Of them is in terms of the amount of sand taken is less, the land taken as a sample is not enough, a hole dug with a slightly different depth and soil also contain impurities which may cause different densities.

Cohesive soils Granular soils

Clay is cohesive, its particles stick

together. Therefore, a machine with a

high impact force is required to ram the

soil and force the air out, arranging the

particles. A rammer is the best choice or

a pad-foot vibratory roller if higher

production is needed.

Since granular soils are not cohesive and

the particles require a shaking or

vibratory action to move them.

Vibratory plates (forward travel) are the

best choice.