SOIL COMPACTION TEST

Introduction

In general, the soil bearing capacity will be increased simultaneously with the increment of density or unit weight of the soil. The increment of soil density can be obtained via compaction process i.e. the process of mechanically reducing the air void.

Objective

Determine the maximum dry density at the optimum moisture content under laboratory condition.

Theory

The test consists of compacting the soil or aggregate to be tested into a standard mould using a standardized compactive energy at several different levels of moisture content. The maximum dry density and optimum moisture content is determined from the results of the test.

Soil in place is tested for in-place dry bulk density, and the result is divided by the maximum dry density to obtain a relative compaction for the soil in place.

In the other hand, soil compaction test is carried out in the laboratory in determining the ideal volume of water to be poured while compaction the soil on site so that the required compaction degree can be obtained. The important characteristics of soil compacted with an ideal compaction degree are:

a) High shear strengthb) Low permeability coefficient and capacityc) Reduce settlement when additional load is applied

The moisture content recorded when the maximum dry unit weight is achieved is known as the optimum moisture content.

There are two types of compaction i.e.:

1. Standard Proctor2. Modified Proctor

Standard Proctor will be used in undertaking the experiment where the standard data are recorded as the following:

Volume of mould

Mass of Hammer

Drop Distance

No. of Blows Per Layer

No. of Layer

Standard Proctor

944 cm3 2.5 kg 305 mm 25 3

Equipment

a) Sieve 5.0 mmb) Weighing machinec) Empty mould with inner diameter of 101.6 mm, inner height of 16.43

mm and volume of 944 cm together with the base plated) Hammer with diameter of 50 mm and mass of 25 kge) Other equipment in determining the soil moisture content

Procedures

1 Small soil sample from jobsite collected.2 5kg of dry soil passing through 4.75mm sieve opening prepared.3 Empty mould, collar and base plate weighed. The empty containers

also weighed.4 The sample mixed thoroughly with approximately 9% water of the total

soil volume.5 The soil sample divided into three sections.6 The any first section placed in the mould and compacted. Distribute 25

blows uniformly over the surface and ensure that rammer always falls freely and is not obstructed by soil in the guide tube.

7 The second section place into the mould and being compacted followed by the last section of soil sample.

8 The attached collar removed when the compaction completes.9 The compacted soil trimmed using the straightedge until it is even with

the top of the mould.10 Small amount of soil from the upper mould taken and placed into a

container.11 Then the container with the soil sample being weighed.12 Small amount of soil from the bottom mould taken and placed into a

container.13 Then the container with the soil sample being weighed.14 Both containers placed into an oven to determine its moisture contain.15 The compacted soil’s sample unit weight determined by dividing the

weight of the compacted soil in the mould with the soil sample volume (volume of the mould).

16 The experiment repeated with three varying water content (12%, 15% and 18%).

17 The dry density computed by using the compacted soil’s wet (bulk) density and the moisture content known.

18 The soil’s dry density versus moisture content graph plotted.

Data

Table 1

No. of Test 1 (9.5%) 2 (12.5%) 3 (15.5%) 4 (18.5%)

Mass of empty mould (kg)

5.305 4.1756.385 5.200

Mass of mould + wet soil(kg)

7.015 5.9358.270 7.150

Mass of wet soil, M (kg)

1.710 1.7601.885 1.950

Volume of mould, V (m3)

9.433x10-4 9.433x10-4

9.433x10-4 9.433x10-4

Bulk density (ρ) = M/V (kg/m3)

1812.785 1865.7901998.304 2067.211

Dry density, (ρ) = ρ b /(1+m) (kg/m3)

1226.512 1404.962 569.480 421.622

Table 2

No. of Container

1(9.5%) 2(12.5%) 3(15.5%) 4(18.5%)

Upper

Bottom

Upper

Bottom

Upper

Bottom

Upper

Bottom

Mass of empty container (g)

16.54

16.00 15.97 15.90 16.40 16.48 15.89 16.68

Mass of empty container + wet soil (g)

46.50

45.99 56.06 63.56 38.79 39.43 69.30 57.77

Mass of container + dry soil (g)

46.37

45.84 55.94 63.39 38.26 38.85 67.42 56.13

Mass of water, Mw (g)

0.13 0.15 0.12 0.17 0.53 0.58 1.88 1.64

Mass of dry 29.8 29.84 39.97 47.49 21.86 22.37 51.53 39.45

soil, Ms (g) 3

Moisture content, m =Mw/ Ms (%)

0.436

0.520 0.300 0.356 2.425 2.593 3.648 4.157

Average Moisture content (%)

0.478 0.328 2.509 3.903

Gs = 2.70

γw = 1000kg/m3

Table 3

A= 0% A= 5%

M % 10 15 20 25 10 15 20 25

Ρd(kg/m3)

2125.984

1921.708

1753.247

1611.940

2019.685

1825.623

1665.584

1531.343

A= 10%

M % 10 15 20 25

ρd(kg/m3) 1913.386 1729.537 1577.922 1450.746

Calculation

Example for test no 1

From table 1:

Mass of wet soil (M) = 1.710 kg

Volume of mould (V) = 9.433x10-4 m 3

Bulk density, ρb = (M/

V )

= 1.710 /9.433x10-4

= 1812.785 kg/ m 3

Dry density, ρd = ρpb / (1+m)

= 1812.785 /(1+0.478)

= 1226.512 kg/m3

From table 2:

Moisture content,m

Mass of water, Mw (g)

= 0.478%

= Mass of empty container + wet soil (g) - Mass of container + dry soil (g)

= 46.50-46.37

= 0.13 g

Mass of dry soil, Ms (g) = Mass of container + dry soil (g) - Mass of empty container (g)

= 46.37 - 16.54

= 29.83 g

From table 3:

When A =0%

Dry density, ρd = pw (1-A)/ (1/Gs +m)

= 1000(1-0)/ (1/2.7+0.1)

= 2125.984

Result

Maximum Density (ρdry) =

Optimum moisture content (V) =

Discussion

Conclusion

Daripada ujikaji yang dijalankan, nilai ketumpatan maksimum dan nilai kelembapan optimum yang diperolehi ialah masing masing. Oleh itu, objektif ujikaji ini iaitu untuk menentukan ketumpatan kering yang maksimum pada kandungan kelembapan optimum dibawah keadaan makmal tercapai.