UK3 LAB Report compaction test PDF

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Compaction Lab Report...

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Department of Civil & Structural Engineering Faculty of Engineering and Built Environment UNVERSITI KEBANGSAAN MALAYSIA LABORATORY REPORT SEMESTER 1, SESSION 2018/19 KH2113 GEOLOGY AND SOIL MECHANICS UK3 SOIL COMPACTION

Group

: GROUP 6

Date

: 2nd OF OCTOBER 2018

Date of submission

: 23th OF OCTOBER 2018

Demonstrator

:

Lecturer

: Dr AIZAT BIN MOHD TAIB@TAIB TEAM MEMBERS

NO 1 2 3 4 5

NAME AZMIR NURHAQIM BIN JEFRIN ROZILEY MUHAMMAD FAISAL BIN YAHAYA LEE JIA HOE NURFAZREEN ASYIQIN BINTI ZAMRI NUR ZURAIRAH BINTI MOHD AR FAHIMAN

MATRICS NO. A165451 A165421 A165247 A165269 A165248

DISTRIBUTION OF MARKS ITEM (S) INTRODUCTION CALCULATION AND RESULTS DISCUSSION AND SUGGESTION CONCLUSION NEAT AND ORDERLY TOTAL

TOTAL (%) 10 40 30 15 5 100

MARKS (%)

UK 3 SOIL COMPACTION 3.1

INTRODUCTION As described in Geotechnical Engineering, soil being a particulate medium

contain pore spaces, which may or may not be filled with water. When the soil which has high void ratio, subject to external forces, the soil particles will be pushed to fill the voids spaces, as a results the soil will be subjected to large deformations. Therefore, it is required to reduce the void spaces of partially saturated loose soil deposits to improve strength, reduce compressibility and conductivity. In the construction of highway embankments, earth dams, and many other engineering structures, loose soils must be compacted to increase their unit weights. Compaction increases the strength characteristics of soils, which increase the bearing capacity of foundations constructed over them. Compaction also decreases the amount of undesirable settlement of structures and increases the stability of slopes of embankments. Smooth- wheel rollers, sheepsfoot rollers, rubber-tired rollers, and vibratory rollers are generally used in the field for soil compaction. Vibratory rollers are used mostly for the densification of granular soils. Vibroflot devices are also used for compacting granular soil deposits to a considerable depth. Standard proctor compaction test is to establish a relationship between dry density and moisture content for a soil under controlled conditions. R.R. Proctor (1933) was the first to develop a method of assessing compacted fill that has since become a universal standard and the test is known as standard proctor test. Standard proctor test is also known as light compaction test as per BIS. AASHO developed a modified test to give a higher standard of compaction and is known as modified proctor test. The same is also known as heavy compaction test as per BIS. In the proctor compaction test, a soil sample is compacted into a standard mold shown in figure 1. The total volume of the mold is 1000cm^3. Compaction of the soil is carried out using the standard hammer shown in figure 1. The hammer has a 2.5kg ram, which can be lifted 300mm and dropped.

In phase relationships, the soil in the soil mechanics term is composed of three phases that are solid, water and air (figure A). Compaction is a process where the air voids are compacted mechanically. the purpose of compaction are :

to control changes in moisture content from further occurrence. to add ground shear strength. to increase the weight of the dry unit or the dry density of the soil. to reduce the permeability of the soil. to reduce the sedimentation of the land especially when the land is dynamically burdensome, the traffic load. In earthworks, machinery such as smooth-wheel rollers, pneumatic rubber-tires rollers, sheepsfoot rollers and vibratory rollers are used for earthworks. the compaction works are carried out on projects such as the preparation of construction sites, land dams, fortifications, retaining walls, roads, railways and airplanes.

The purpose of the laboratory compaction test is to obtain determinations in the compaction work on the site. The soil consolidation process can be described as follows. When water is added to a soil with low moisture content, this water will act as a 'lubricant' between the soil particles. This will cause increased soil loads and the value of dry soil density will decrease. Therefore for each type of soil and for the quantity and type of compaction given, there is an optimum moisture content that will produce the state of the soil particles present once with the maximum dry density.

Air

Va

Water

Vw

Solid Vs

Figure A : Soil Phase Model Va = Volume of air Vw = Volume of water Vs = Volume of solid V = Total volume = Va + Vw + Vs

a = percentage of water void a/100 = Va/V

or;

next;

Va = a.V/100

V = a.V + Vw Vs

(3.1)

100 or;

V (1-A/100) = Vw + (3.2) Vs W = V w pw

= (3.3)

Vw/Gs.Vs Vs.Gs.pw

substitute Vw = w.Gs.Vs in equation (3.2) V (1-a/100) = w.Gs.Vs + Vs = Vs (1 + w.Gs)

so;

V = Vs (1 + w.Gs)

(3.4)

1 - (a/100) the dry density of the soil according to the definition is; pd = Vs.Gs.Pw = Vs.Gs.Pw (1 - a/100) V

Vs (1 + w.G s)

(3.5)

(3.6)

that is ; pd = Gs.Pw (1 a/100) (1 + w.Gs)

for empty air voids condition;

(3.7)

pd = Gs.Pw (1 + w.Gs)

where; Pw = density of water Gs = the specific gravity of the solid particles of the soil W = moisture content

3.2

METHOD OF 4.5 KG RAMS (MODIFIED ASSHTO METHOD)

INTRODUCTION

Compaction is a process in which the soil particles are mechanically compacted to increase densities.

APPARATUS

a. Cylinder mold reference in 105 mm, measuring height in 115.5 mm and 1000 cm3 in volume b. Metal rams diameter 50 mm, weighing 4.5 kg and spacing of 450 mm c. Balance sheet with accuracy of 1 g d. Pallet knife e. Metal ruler f.

Sieve BS 20 mm

g. Rate metal plates h. Tools for determining moisture content

PROCEDURE

1. Soil samples for testing should be first dried with air, then sieved with BS 20 mm sieve. As many as 5 kg of sifted soil samples are required. Gravel content should

be recorded and if the gravel content is much (that is more than 5%), then correction should be made to the test results later. (refer to BS 1377) 2. A mixture of water into the sample (approximately 5% less than the original moisture content if known, or a value of 6% is used). Finish the sample for 2 or 3 hours before testing. 3. Weight of the mold with the base plate (M1). 4. Compacted the damp in the mold in the five layers of the same thickness and each layer is subjected to 27 impacts with a ram which is dropped from a height of 450 mm. The number of samples used in the test should be sufficient to meet the reference.The height of the sample that is allowed to stand out on the mold surface after the finished finish is more than 6mm (if more, the test should be repeated). This prominent piece is cut and decorated and with mold surface. 5. Weight reference with the sample of the soil that has been packed in it. 6. Remove the compacted soil from the mold and put it in the metal. Take some of the soil samples for moisture test, as follows : 

two in between 3 cm above the soil sample



two in between 3 cm below the soil sample



two in the center part of the soil sample

7. The remaining samples were broken down and re-mixed with other unused samples. Add water, but this time should be more (about 2% more). Repeat the test for at least five times.

3.3

METHOD OF 2.5 KG RAMS (PROCTOR METHOD)

This test method is the same as the 4.5 kg rams method, but with the following differences:

a.

The rams 2.5 kg is used and the fall height is 300 mm.

b.

Soil samples are compacted in three layers and each layer is subjected to 27 impacts.

Other aspects are the same.

DISCUSSION AND SUGGESTION

During construction, compaction is essential to increase the shear strength, decrease the compressibility, decrease its permeability and minimize long-term settlement in the soil. It is difficult to check those objectives directly therefore they are checked indirectly by finding the optimum moisture content and dry unit density. By finding the optimum moisture content and maximum dry density it allows civil engineers to gauge the soils strength. When soils close to 0% moisture content it can only be compacted by so much but as water is added, the dry unit weight increases because the water lubricates the particles making compaction easier. As more water is added and the water content becomes larger than the optimum values, the void spaces become filled with water so further compaction is not possible. Beyond this point, the dry unit weight decreases.

The points at which this begins to happen is described as the optimum moisture content and the maximum dry unit weight. In this test the Optimum Moisture Content for 4.5 kg were found to be 11.5 Mg/m3 and Maximum dry unit weight were 1.89 Mg/m3 saturation while Optimum Moisture Content for 2.5 kg were found to be 15.5 Mg/cm3 and dry unit weight 1.78 Mg/m3 saturation. For any given water content and soil solids, the zero-air-voids dry unit weight represents the best possible compaction. The actual compaction curve was below the zero voids curve which is an expected result. For a given soil and water content the best possible compaction is represented by the zero-air-voids curve on Graph 1 and Graph 2. The actual compaction curve will always be below it. Compaction of soil increases the density, shear strength, bearing capacity, thus reducing the voids, settlement and permeability. Hence the optimum moisture content and the maximum dry density are useful in the stability of field problems like earthen dams, embankments, roads and airfields. Compaction in the field is controlled by the value of the optimum moisture content determined by laboratory compaction test. In other words, the laboratory compaction tests results are used to write the compaction specifications for field compaction of the soil.

What is the need to conduct compaction tests on site when we have conducted soil compaction tests in the lab? Actually, the compaction test results in

the lab cannot be used directly for compaction on the site because the solids or compaction energy in the lab is different, and imposed by which differ from the use of equipment on the site. The laboratory test results are only a rough guide to the water supposed to be obtained for the maximum dry density value obtained. The strictly compaction test results in the lab are useful for the purpose of classification and selection of soil suitable for earthwork. The compaction of compaction on the required site can be determined according to the percentage of the maximum dry density produced in one of the standard laboratory tests. For example, it may be noted in the specification that the dry density must be not less than 95% of the maximum dry density obtained from the standard Proctor test in the laboratory. In addition, the water content limit must be stated. That is to say, compaction will be achieved as a result of the presence of natural groundwater within the limits.

Sources of error Water may not have been thoroughly absorbed into the dry soil. As a precaution an adequate period should be allowed to mature the soil after it is mixed with water Each layer of soil may not have been the same depth into the collar of the mould as a precaution proper care should be taken to make sure that each layer is nearly equal in weight. To avoid stratification each compacted layer should be scratched with spatula before next layer is placed. Human error in operating the hand rammer, it is impossible to apply the same compaction energy to each layer. A possible precaution that could be taken is to ensure that the same person applies the blows to each layer. Another will be to ensure the rammer blows are uniformly distributed over the surface.

Improvements More accurate results could be obtained if the manual compacting hammer was replaced with a mechanical arm along with using a fixed height and fixed force to uniformly compact the sample. CONCLUSION

Compaction of soil is an important process, as it helps it of achieve certain physical properties necessary for its proper behaviour under loading: for example proper compaction of an earthen dam or a highway Embankment reduces the chances of its settlement, increases the shear strength of the soil due to its increased density and reduces the permeability of the soil. The proctor compaction test was carried out succesfully and obtained a curve that satisfied the objectives. Clearly identified the relationship between the dry density and the water content of a soil and reasons to have that change was studied.

APPENDIX

REFERENCES

 Compaction of soil-process-necessity-and-theory-of-compaction. Z.Khan Available at: http://www.yourarticlelibrary.com/geography/compaction-of-soil-processnecessity-and-theory-of-compaction/45567/ [Last accessed: 12th October 2018]  Proctor soil compaction Available at: http://www.naturalbuildingblog.com/proctor-soil-compaction-test/ [Last accessed: 14th October 2018]  soil-compaction-test (2018) Available at: http://www.vertekcpt.com/blog/soil-compaction-test-intro#.V-IJNPl97IU [Last accessed: 9th October 2018]  BRAJA M. DAS. Principles of Geotechnical Engineering. Seventh Edition...