Al-Qadisiya Journal For Engineering Sciences Vol. 4 No.

1 Year 2011

A COMPARISON OF (CBR) SOAKED TEST WITH BRITISH

SPECIFICATIONS FOR FINE-GRAINED SOILS FROM AL-KUT
IN IRAQ

Asst. Lec. Qais Kadhim Jahanger Asst. Lec. Zuhair Kadhim Jahanger

Environmental Engineering. Dep. Dep. of Water Resources Engineering

Al-Mustansiriyah University /Iraq University of Baghdad /Iraq

ABSTRACT:
The California bearing ratio (CBR) test has been widely used in pavement design since mid
1940's. It is a relative measure of sub-grade soil or base/sub-base aggregate strength. Nine samples,
about 50 kg are taken from different test pits dig to 1.5m from natural ground surface, the soil is
fine grained either silt or clay. The nine (CBR) specimens were compacted at optimum moisture
content and at 95% of the maximum dry density of the modified compaction test were prepared.
All specimens were soaked for periods of 96hr with more than 4.5kg surcharge load. Penetration
test was done for both two faces (top and bottom) of the specimen. The tests denoted that most CBR
curves are convex upwards so no correction is needed. CBR number is less than 20 so is very poor
to fair, where the best using for sub grade due to its fine grained soil. Mostly CBR number that is
calculated from bottom face is grater than top face, as they are less wetting than top face.
The paper reveals that most CBR values are small, depended from 5mm penetration of the
bottom face of specimens, which no correction method is needed for curves.

Key Words: CBR Test, Fine-Grained Soils, Proctor's Compaction test, Soaking

‫( ﻤﻘﺎﺭﻨﺔ ﺍﺨﺘﺒﺎﺭ ﻤﻌﺩل ﺍﻟﺘﺤﻤل‬CBR) ‫ﺍﻟﻤﻐﻤﻭﺭ ﻤﻊ ﺍﻟﻤﻭﺍﺼﻔﺎﺕ ﺍﻟﺒﺭﻴﻁﺎﻨﻴﺔ ﻟﺘﺭﺒﺔ‬

‫ﺩﻗﻴﻘﺔ ﺍﻟﺤﺒﻴﺒﺎﺕ ﻤﻥ ﺍﻟﻜﻭﺕ ﻓﻲ ﺍﻟﻌﺭﺍﻕ‬
‫ زھﯿﺮ ﻛﺎﻇﻢ ﺟﮭﺎن ﻛﯿﺮ‬.‫م‬.‫م‬ ‫ ﻗﯿﺲ ﻛﺎﻇﻢ ﺟﮭﺎن ﻛﯿﺮ‬.‫م‬.‫م‬
‫ﻗﺴﻢ ھﻨﺪﺳﺔ اﻟﻤﻮارد اﻟﻤﺎﺋﯿﺔ‬ ‫ﻗﺴﻢ ھﻨﺪﺳﺔ اﻟﺒﯿﺌﺔ‬
‫ اﻟﻌﺮاق‬/‫ﺟﺎﻣﻌﺔ ﺑﻐﺪاد‬ ‫ اﻟﻌﺮاق‬/‫اﻟﺠﺎﻣﻌﺔ اﻟﻤﺴﺘﻨﺼﺮﯾﺔ‬

532
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

‫ﺍﻟﺨﻼﺼﺔ‬

‫ ﺤﻴـﺙ‬.‫( ﻴﺘﻡ ﺍﺴﺘﺨﺩﺍﻤﻪ ﺒﺸﻜل ﻭﺍﺴﻊ ﻓﻲ ﺘﺼﻤﻴﺼﻡ ﺍﻟﻁﺭﻕ ﻤﻨﺫ ﻤﻨﺘﺼﻑ ﺃﺭﺒﻌﻴﻨﺎﺕ ﺍﻟﻘﺭﻥ ﺍﻟﻤﺎﻀـﻲ‬CBR) ‫ﻓﺤﺹ ﻤﻌﺩل ﺍﻟﺘﺤﻤل‬
‫ ﻜﻐﻡ ﺍﺨﺫﺕ ﻤـﻥ‬50 ‫ ﺘﺴﻌﺔﻋﻴﻨﺎﺕ ﺒﺤﺩﻭﺩ‬.‫ﻴﻌﺘﺒﺭﺍﻟﻔﺤﺹ ﻤﻘﻴﺎﺱ ﻨﺴﺒﻲ ﻟﻘﻭﺓ ﺘﺭﺒﺔ ﺍﻟﺘﺩﺭﺝ ﺍﻭ ﺭﻜﺎﻡ ﻁﺒﻘﺎﺕ ﺍﻟﺴﺒﻴﺱ ﺍﻭ ﺘﺭﺒﺔ ﺍﻟﺘﺴﻭﻴﺔ‬
‫ ﻨﻤـﺎﺫﺝ‬.‫ ﺍﻟﺘﺭﺒﺔ ﻫﻲ ﺩﻗﻴﻘﺔ ﺍﻟﺤﺒﻴﺒﺎﺕ ﺃﻤـﺎ ﻏـﺭﻴﻥ ﺍﻭ ﻁـﻴﻥ‬,‫ ﻤﺘﺭ ﻤﻥ ﺴﻁﺢ ﺍﻻﺭﺽ‬1,5 ‫ﺤﻔﺭ ﺍﺨﺘﺒﺎﺭﻴﺔ ﻤﺨﺘﻠﻔﺔ ﺒﺤﻔﺭ ﻴﺼل ﺍﻟﻰ‬
‫ ﻤﻥ ﺍﻟﻜﺜﺎﻓﺔ ﺍﻟﺠﺎﻓﺔ ﺍﻟﻘـﺼﻭﻯ ﻟﻔﺤـﺹ‬%95 ‫( ﺍﻟﺘﺴﻌﺔ ﻗﺩ ﺘﻡ ﺭﺼﻬﺎ ﺤﺴﺏ ﻤﺤﺘﻭﻯ ﺍﻟﺭﻁﻭﺒﺔﺍﻷﻤﺜل ﻭﺍﻋﺩﺍﺩﻫﺎ ﻋﻨﺩ ﻤﺴﺘﻭﻯ‬CBR)
. ‫ﺍﻟﺭﺹ ﺍﻟﻤﻌﺩل‬

‫ ﺘﻡ ﺃﺠﺭﺍﺀ ﻓﺤـﺹ ﺍﻷﺨﺘـﺭﺍﻕ ﻟﻜـﻼ‬.‫ ﻜﻐﻡ ﺍﻭ ﺃﻜﺜﺭ ﻤﻥ ﺍﻻﺤﻤﺎل ﺍﻟﺩﺍﻓﻌﺔ‬4.5 ‫ﺴﺎﻋﺔ ﻤﻊ‬96 ‫ﺜﻡ ﺠﻤﻴﻊ ﺍﻟﻨﻤﺎﺫﺝ ﺘﻡ ﻏﻤﺭﻫﺎ ﺒﺎﻟﻤﺎﺀ ﻟﻤﺩﺓ‬
‫ ﺃﺸﺭﺕ ﺍﻻﺨﺘﺒﺎﺭﺍﺕ ﺍﻥ ﻤﻌﻅﻡ ﺍﻟﻤﺨﻁﻁﺎﺕ ﻫﻲ ﻤﺤﺩﺒﺔ ﺍﻟﻰ ﺍﻻﻋﻠﻰ ﻟﺫﻟﻙ ﻻ ﺘﺤﺘﺎﺝ ﺍﻟﻰ ﺘﺼﺤﻴﺢ‬.(‫ﻭﺠﻬﻲ ﺍﻟﻨﻤﻭﺫﺝ )ﺍﻟﻌﻠﻭﻱ ﻭ ﺍﻟﺴﻔﻠﻲ‬
‫ ﺍﻻﺴﺘﻌﻤﺎل ﺍﻻﻓﻀل ﻜﺘﺭﺒﺔ ﻁﺒﻘﺔ ﺴﻔﻠﻴﺔ ﺒﺴﺒﺏ ﺤﺒﻴﺒﺎﺘﻬـﺎ‬،‫ ﻟﺫﻟﻙ ﺍﻟﺘﻘﻴﻡ ﻫﻭ ﻤﻥ ﻓﻘﻴﺭﺠﺩﺍﹰ ﺍﻟﻰ ﻤﻨﺎﺴﺏ‬%20 ‫( ﺃﻗل ﻤﻥ‬CBR) ‫ﻭﺍﻥ ﻗﻴﻤﺔ‬
‫ ﻷﻨﻪ ﺍﻗل ﺭﻁﻭﺒﺔ ﻤﻥ ﺃﻟﻭﺠـﻪ‬،‫( ﺍﻟﻤﻘﺎﺴﺔ ﻤﻥ ﺍﻟﻭﺠﻪ ﺍﻻﺴﻔل ﻫﻲ ﺃﻜﺒﺭ ﻤﻥ ﻗﻴﻡ ﺍﻟﻭﺠﻪ ﺍﻟﻌﻠﻭﻱ ﻟﻠﻨﻤﻭﺫﺝ‬CBR) ‫ ﻭﺃﻥ ﻤﻌﻅﻡ ﻗﻴﻡ‬.‫ﺍﻟﺩﻗﻴﻘﺔ‬
.‫ﺍﻻﻋﻠﻰ ﻟﻠﻨﻤﻭﺫﺝ‬

،‫ ﻤﻠﻡ( ﻤﻥ ﺍﻟﻭﺠﻪ ﺍﻟﺴﻔﻠﻲ ﻟﻠﻨﻤﺎﺫﺝ‬5)‫ ﺤﻴﺙ ﺘﻡ ﺍﻋﺘﻤﺎﺩﻩ ﻤﻥ ﺍﺨﺘﺭﺍﻕ ﺍﻟـ‬،‫( ﻟﻠﻨﻤﺎﺫﺝ ﻫﻲ ﺼﻐﻴﺭﺓ‬CBR) ‫ﻴﻭﻀﺢ ﺍﻟﺒﺤﺙ ﺃﻴﻀﺎﹰ ﺍﻥ ﻤﻌﻅﻡ‬
.‫ﻭﻟﻡ ﺘﻜﻥ ﻫﻨﺎﻙ ﺤﺎﺠﺔ ﻟﻭﺴﻴﻠﺔ ﺍﻟﺘﺼﺤﻴﺢ ﻟﻠﻤﺨﻁﻁﺎﺕ‬

NOMENCLATURE

I. CBR: California Bearing Ratio

II. USCS: Unified Soil Classification System
III. LL: Liquid Limit
IV. PL: Plastic Limit
V. PI: Plasticity Index
VI. CL: Clay Low Cohesive
VII. ML: Silt Low Cohesive

INTRODUCTION:

In the last two decades, there has been rapidly expanding road construction programs in the
Middle East and in many of world's hot desert regions where evaporation exceeds precipitation, to
minimize the construction cost for road projects in such regions, the use of locally available
materials will always be necessary task of highways engineers (Razouki, 2003).
In the field of highways and roads construction, the California Bearing Ratio (CBR) test has
been widely used in pavement design since mid 1940's. It is a relative measure of sub- grade soil or
base/sub-base aggregate strength (Hossain, 2005).
The standard shape of force-penetration curve corresponding to a CBR value is convex upward
as shown in Fig. (1) Of typical test result.

533
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Where the forces corresponding to standard curve are: 11.5 KN at 2mm penetration, 13.2 KN at
2.5mm, 17.2KN at 4mm, 20KN at 5mm, 22.2KN at 6mm and 26.3KN at 8mm. According to the
curve shape, it will be no correction needed where this shape is convex upward as stated by BSI
(BS 1377-9).

Laboratory tests of Iraqi fine grained soils (Clay and Silt soils) for these 9 specimens in Al-Kut
City shows the differences in curve shape so the forces strength.
The objective of this study is make a comparison between CBR curves that connecting of Al-
Kut fine-grained soils of different sites from designed road, with the standard correction methods
for laboratory (CBR) tests to obtain (CBR) number. It worth mentioning that the tests have been
done by the authors themselves and for all specimens.

METHODOLOGY

Soil description
The program consists of 9 (CBR) tests on specimens of fine grained soils (Clay and Silt)
according to USCS and Hydrometer test as shown in Table (1) of Al-Kut City (southeast area) in
soaking term as worst case, the soil is placed in the compaction mold under the specification of
(ASTM D1883-05) and take its test series from compaction to penetration test for both faces of
specimens top face and then bottom face, where tests are controlled laboratory circumferences.

PROCEDURE OF THE TEST

Compaction
CBR tests are usually carried out on test specimens at the optimum moisture content value for
the soil as determined using the standard (or modified) compaction test, depended on the grain size
distribution and percentage of retained on sieve No.200. Next, using methods C of ASTM D1557-
02 or D698 - 00 (for the 15.2 cm diameter mold) the specimens are made using the compaction
energy as shown below in Table (2)(Bowels,1988)(ASTM, D 1557- D 698):
In this research the specification (ASTM D1557-02 C modified) is used for the soil compaction
for CBR test and the equipment are explained in the following Table (3):

Soaking
The flowing standard steps as mentioning were applied to soak the specimens and prepare it for
the penetration test (Bowels, 1988)(ASTM, D1883).

• After the compaction, the collar was removed then the specimen was trimmed smooth and
flush with mold

534
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

• The base plate and spacer disk were removed; the mold + compacted soil had been weight
and determining the wet unit weight (take sample for water content determination).
• A piece of filter paper was Placed on the base plate, the specimen was inverted (so the
5.1cm gap is on top), and attach the base plate so the soil is in contact with the filter paper
on the base.
• The perforated plate with adjustable stem was placed on the compacted soil and applied
sufficient additional slotted weights to obtain the desired surcharge with in 2.2 kg but with a
total surcharge weight of not less than 4.5 kg (the perforated plate is a part of surcharge
weight).
• The mold and weights were immersed in a container of water so the water has access to both
the top and bottom of the sample and attach the dial gage (reading to 0.01 mm) in its holding
brackets (Tripod).
• The swell gage was set to zero to start reading and recorded the time of the start of the test
.Take readings at 0, 1, 2, 4, 12, 24, 48, 72 and 96h of elapsed time.
• At the end of 96h of soaking, the sample was removed and it was let to drain for 15 min.
Blot the sample surface by paper towels
• The Soaked sample including the mold was Weight.

CBR penetration
Penetration testing is accomplished in a manual compression machine using a strain rate of 1.27
mm/min. Readings of load vs. penetration are taken at each 0.5mm of penetration to include the
value of 5mm and then at each 2.5mm increment there after until the total penetration is
12.7mm(Bowels,1988)(Gupta,2005).

RESULTS

Test specimens results about its swelling, CBR and curves will be explained in the following
tables and figures. During soaking in CBR test, measurement of vertical movement (swelling or
settlement) was carried out by means of an (0.01) mm dial gauge attached to the stem of the
swelling plate (Razouki,2003), as shown in Fig.(2). Therefore, Table (4) illustrates the swelling and
CBR of the specimens.

Load- Penetration curve

The penetration loads was calculated in kilopascal (or megapascals) and the load penetration
curve was drawn (ASTM, D1883). In some instances the load-penetration curve may be concave
upward initially, because of surface irregularities or other causes, and in such cases the zero point
shall be adjusted as shown in Fig.(1), and the corrected curve shape should be taken to calculate the
bearing ratio.

535
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Bearing ratio
The load values (the normal or the corrected due to the curve shape) were taken from the load –
penetration curve (curves as shown from Fig.3 to Fig.11) for (2.5mm) and (5mm) penetrations were
used to calculate the bearing ratios for each by the equation(1) (ASTM, D1883):

The Calculated Load

CBR (%) = ×100 (1)
The Sandard Load

Where:
The calculated load = material resistance or the unit load on the piston (pressure)
for 2.5 mm or 5mm of penetration
The standard load = standard unit load (pressure) for well graded crushed stone

= for 2.5 mm penetration = 6900 kPa

= for 5 mm penetration = 10300 kPa
The bearing ratio reported for the soil is normally the one at 2.5mm penetration, when the ratio
at 5mm penetration is greater, the test was rerun. If the check test gives a similar result, use the
bearing ratio at 5mm penetration. Where Table (5) explains the calculated CBR for each specimen.

Calculation
The following Table (6) shows example for the calculation that was done for determination of
loads and penetration for sample no.1:
For column no. 3 and no.6 the penetration was calculated as:

Penetration (mm) = [( Time * P .R ) - ( Factor * D.G.R )] (2)

Where
Time: readings time (min.)
P.R.: Penetration Rate = 1.27 mm/min
Factor: dial gauge factor=0.0025 mm/div.

D.G.R.: Dial gauge reading (div.)

536
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

For column no.4 and no.7 the stress was calculated as:

D.G.R * P .R.Factor
Stress (kPa) = * 98.1 (3)
Area
Where:
D.G.R.: Dial gauge reading (Div.)

P.R.Factor: Proving ring factor= 0.336 kg/div.

Area: Plunger area= 19.4cm

CONCLUSIONS

This paper has presented the results of an experimental work of 9 different soil samples used as
subgrade soil for road site. From the results of this work, the following conclusions can be taken:
1. The soil studied was obtained from Iraq, Waset governorate, Al-Kut city(south east area).
The soil is fine-grained either Silt or Clay (where ML or CL) belonging to the unified soil
classification system and Hydrometer tests.
2. CBR values are small for most specimens between 0 to14%, where depended from 5mm
penetration of bottom face, so the general rating from very poor to fair, therefore; best using
for sub grade usually, due to its fine grained particles.
3. Mostly CBR values that were determined from bottom face of specimen are greater than top
face, because that the upper layer in the mold during compaction becomes the bottom face
of the specimen for CBR test.
4. The closing and faring between top and bottom curves like Fig.5 and Fig 6 depend on
classification of soil, Silt mostly has closing values for top and bottom curves, so clay has
faring values between top and bottom.
5. The intersection of top and bottom curves in Fig.6 resulted from low cohesive silt soil of
high moisture content to dry unit wet.
6. The linear behaviour of curves like in Fig.11 explains the constant increasing for strength of
soil to penetration due to particle size of high percentage of silt.

ACKNOWLEDGMENT

Special thanks to Andrea Engineering test laboratory to allow us to use their devices and
information.

537
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

REFERENCES

1. ASTM D1883-05,"Standard Test Method for CBR (California Bearing Ratio) of

Laboratory-Compacted Soils", 2005.

2. ASTM, D 698-00, "Standard Test for Laboratory Compaction Characteristics of Soil Using
Standard Effort", November 2003.

3. ASTM, D 1557-02, "Standard Test for Laboratory Compaction Characteristics of Soil Using
Modified Effort", November 2003.

4. Bowels, J.E.," Engineering Properties of Soils and Their Measurement", 2nd Edition,
McGraw-Hill, 1988.

5. British Standard Institute, "BS 1377-9:1990" Licensed Copy: Robert Mcapline, Amec
Capital Projects Ltd, November 2004.

6. Gupta, R.D. et al," Effect on CBR Value and Other Geotechnical Properties of Fly Ash
Mixed with Lime and Nom-Woven Geofibers, "College of Eng. &Tech., University of
Polytechnic, AMU, Aligahra (India), October 2005.

7. Hossain, S., Dickerson, G.M. and Weaver C.B.," Comparative Study of VTM and AASHTO
Test Method for CBR", Co Materials Division, VDOT, September 2005.

8. Razouki, S.S. and Al-Azawi, M.S.," Long-Term Soaking Effect on Strength and
Deformation Characterises of a Gypsiferous Sub grade Soils", Engineering Journal of the
University of Qatar, Vol.16, pp46-60, 2003.

538
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Table (1) Geotechnical properties for Al-Kut Specimens

Sample Sieve Analysis & Index Properties Natural USCS

No. Hydrometer
Water
Sand% Silt% Clay% LL% PL% PI%
Content%

1 6.6 46.5 46.9 44 23 21 10 CL

2 4.5 33.2 62.3 43 23 20 14.3 CL

3 7.3 62.6 30.1 41 26 15 13.1 ML

4 5.9 64.4 29.7 34 23 11 12.8 ML

5 8.1 53.5 38.4 36 21 15 14.1 CL

6 6.8 63.3 29.9 36 25 11 14.6 ML

7 5.3 71.5 23.2 35 24 11 13.8 ML

8 6.4 51.9 41.7 41 20 21 18.8 CL

9 7.2 67.7 25.1 32 23 9 28.9 ML

Table (2) CBR Compaction Specification

Method Mould Passing Layers Blows Rammer

weight (N)
(mm) Sieve No.

D 698: A 101.6 4 3 25 24.5

B 101.6 9.5mm 3 25 24.5

C 152.4 19mm 3 56 24.5

D 1557: A* 101.6 4 5 25 44.5

B 101.6 9.5mm 5 25 44.5

C 152.4 19mm 5 56 44.5

* D1557 A is used to determine the water content and dry unit weight

539
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Table (3) Compaction Apparatus (1)(4)(7)

Equipments and
CBR Test Standard Remarks
Accessories

Loading Machine Capacity of 44.5KN

Uniform movement rate of
1.27mm/min.

Mold Size Diameter= 15.2 cm Or Equivalent

Height= 17.8 cm

Extension Collar Diameter= 15.2 cm

Height= 5 cm

Spacer Disc Diameter= 15.1 cm Or 5.1 Height as available

Height= 6.14 cm

Compaction Rammer 44.5 N weight Or 24.5 N as Standard

Swell Base Plate Diameter= 15 cm

Height= 0.625 cm
Perforated with 42 hole
Hole diameter= 0.16 cm

Surcharge weight Diameter= 15 cm Not less than 4.5 Kg

Weight= 2.268 Kg

540
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Table (4) Specimen Swelling and CBR Number

Sample No. Swelling % CBR 2.5mm CBR 5mm General

Rating
Top Bottom Top Bottom
1 7.5 1.3 3.69 1.74 8.55 * Fair
2 5.25 2.4 * 6.5 1.95 7.35 Very Poor
3 3.32 4.42 7.24 5.9 8.57 * Fair
4 1.66 2.6 2.75 3.15 2.92 * Very Poor
5 1.34 2.25 4.5 2.55 5.35 * Very Poor
6 4.27 4.05 13.9 * 6.33 10.95 Fair

7 4.17 3.77 7.1 5 9.24 * Fair

8 2.85 3 3.25 * 3.15 2.7 Very Poor
9 1.65 2.3 3.45 3.3 4.15 * Very Poor
* Represent the CBR value of specimen

Table (5) CBR Values

Sample No. USCS Compaction Test CBR Value

at 95%
Max. Dry Optimum Compaction
Density Moisture
kN/m3 Content %

1 CL 18.27 10.1 8.55

2 CL 18.04 10.6 2.4

3 ML 17.85 13.2 8.57

4 ML 17.95 14.3 2.92

5 CL 17.88 12.5 5.35

6 ML 18.02 11.5 13.9

7 ML 17.91 12 9.24

8 CL 18.28 12.7 3.25

9 ML 17.95 14.9 4.15

541
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Table (6) Sample No.1 calculations

1 2 3 4 5 6 7

Time Top Face Bottom Face

(min.) Dial Penetration Stress Dial Penetration Stress
gauge gauge
reading (mm) (kPa) reading (mm) (kPa)

(div.) (div.)

0 0 0 0 0 0 0

0.5 12 0.605 20.3 41 0.53 70

1 27 1.2 45 72 1.09 122

1.5 41 1.8 70 107 1.64 181

2 55 2.4 93 145 2.18 246

3 77 3.61 130 228 3.24 387

4 97 4.84 164 308 4.31 522

6 135 7.28 230 434 6.54 737

8 173 9.73 294 517 8.87 877

10 218 10.15 370 577 11.26 279

542
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Fig.1 Typical CBR test results curves (BS 1377-9)

543
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

A. Specimen in swelling tank

B. Specimen before penetration C. CBR penetration Experimental set-up

D. Top face penetration E. Bottom face penetration

Fig.2 CBR Penetration Apparatus

544
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Stress - Penetration Curve

12
Stress (Kpa ) X100
10
Bottom
8 Top

0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)

Fig. 4 CBR Curve for Test Sample No.2

Stress - Penetration Curve

12
X100

Bottom
10
Top
8
Stress (Kpa)

0
0 1 2 3 4 5 6 7 8 9 10
Penetration (m m )

Fig.5 CBR Curve for Test Sample No.3

545
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Stress - Penetration Curve

Stress (Kpa) X100 8

7 Top
6 Bottom
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)

Fig.6 CBR Curve for Test Sample No.4

Stress - Penetration Curve

10
S tre s s (K p a ) X 1 0 0

9
8 Bottom
7 Top
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10

Penetration (mm)

Fig.7 CBR Curve for Test Sample No.5

Stress - Penetration Curve

12
Stress (Kpa) X100

10

6
4
Bottom
2
Top
0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)

Fig.8 CBR Curve for Test Sample No.6

546
Al-Qadisiya Journal For Engineering Sciences Vol. 4 No. 1 Year 2011

Stress - Penetration Curve

16
Stress (Kpa) X100 14 Bottom
12 Top
10
8
6
4
2
0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)
Fig.9 CBR Curve for Test Sample No.7

Stress - Penetration Curve

5
Stre ss (Kp a) X100

Top
4
Bottom
3

0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)
Fig.10 CBR Curve for Test Sample No.8

Stress - Penetration Curve

10
Stress (Kpa) X100

Bottom
8 Top
6
4

0
0 1 2 3 4 5 6 7 8 9 10
Penetration (mm)

Fig.11 CBR Curve for Test Sample No.9

547