PRACTICAL

Group
CALIFORNIA BEARING RATIO No.
TEST

FACULTY OF ENGINEERING TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING TECHNOLOGY

PRACTICAL/LABWORK

BNC 31803 SITE INVESTIGTION

INSTRUCTION SHEETS

PRACTICAL NO.

TITLE IN-SITU CALIFORNIA BEARING RATIO TEST

DATE OF PRACTICAL WORK

NAME MATRIX NO.

NAMA NO. MATRIK
1.

2.
GROUP MEMBERS
3.

4.

5.

1.
LECTURER / INSTRUCTOR
2.

RECEIVED DATE AND STAMP

TOTAL MARK (FROM RUBRIC

ASSESSMENT)
 PRACTICAL
CALIFORNIA BEARING RATIO TEST

STUDENT CODE OF ETHICS

DEPARTMENT OF CIVIL ENGINEERING TECHNOLOGY

FACULTY OF ENGINEERING TECHNOLOGY

I hereby declare that I have prepared this report with my own efforts. I also admit to not accept or

provide any assistance in preparing this report and anything that is in it is true.

1) Group Leader __________________________________ (Signature)

Name : __________________________________
Matrix No. : __________________________________

2) Group Member 1 ___________________________________ (Signature)

Name : ___________________________________
Matrix No : ___________________________________

3) Group Member 2 __________________________________ (Signature)

Name : __________________________________
Matrix No. : __________________________________

4) Group Member 3 __________________________________ (Signature)

Name : __________________________________
Matrix No. : __________________________________
 PRACTICAL
CALIFORNIA BEARING RATIO TEST

OBJECTIVE
• Determine the strength of a sub-grade, sub-base and base course materials.
• Determine the pressure required to penetrate a soil with a plunger.

LEARNING OUTCOMES

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

• Calculate the force applied to the plunger from each reading of the loading ring
observed during the penetration test.
• Determine the CBR value based on in-situ testing.
• Plot each value of force as ordinate against the corresponding penetration.

INTRODUCTION

The site instigation (SI) is the one thing that must be done before starting the construction of
the building. This is because the soil condition at the site need to be identifies to determine
the suitable foundation use for the building and soil play a main role to support the load that
come from the building and the building need a suitable foundation to transfer the load to the
ground. Therefore, the investigation of soil need to be done to identify the type of soil to
ensure the soil can carry the load. Three main processes of SI frequently carried which are
boring, sampling and testing of soil on site. Standard Penetration Test (SPT) is the most
popular method of SI that caters all the processes mentioned that recorded completely the
soil profile. Normally, large scale project with high budget suits this method which produce
detail information on soil profile and almost at sensible depth for construction.

Figure 1: California Bearing Ratio equipment

 PRACTICAL
CALIFORNIA BEARING RATIO TEST

The California Bearing Ratio (CBR) was developed by California division of highways as a
method of classifying and evaluating soil-sub-grade and base course materials for
flexible pavements. The CBR test is currently used in pavement design for both roads and
airfield pavement.

This method covers the determination of the California Bearing Ratio (CBR) of a soil tested
in situ, with a selected overburden pressure, by causing a cylindrical plunger to penetrate the
soil at a given rate and comparing the relationship between force and penetration into the
soil to that for a standard material. At certain values of penetration the California Bearing
Ratio (CBR) is defined in the form of a percentage, as the ratio of the force exerted on the
soil to a standard force that would be exerted on a specified crushed rock compacted and
confined in a given manner.

Plot the load deformation curve for each specimen. In some cases the initial penetration
takes place without a proportional increase in the resistance to penetration and the curve
may be concave upward. To obtain the true stress-strain relationships, correct the curve
having concave upward shape near the origin by adjusting the location of the origin by
extending the straight the portion of the stress strain curve down ward until it intersects with
x-axis. Determine the corrected load values at 2.5mm and 5.0 mm and determine the CBR
by the following relationship.

CBR = Test unit stress x 100

Standard unit stress

**Standard load at 2.5mm is taken 13.2kN and at 5.0mm it is on 20kN

EQUIPMENT

• 50kN Mechanical Jack (P001)

• Extension Rod Set (P002)

• Penetration Piston (P003)

• Dial Gauge Holder (P004)

• Surcharge Set (P005)
P006

• Datum Bar Set (P006)

• Dial Indicator
P002
• 50 kN Proving Ring (P007)
P005 P004
• Reaction Load (forklift, lorry etc)

P007 P003
P001
 PRACTICAL
CALIFORNIA BEARING RATIO TEST

PROCEDURE

1. Equipment for the test is assembled.

2. Remove from the test area any material which is not representative of the soil to be
tested, and prepare a circular area of about 500 mm in diameter such that it is flat
and horizontal, taking special care with the central area on which the plunger will
bear.
3. Position the reaction load and its supports, such as the jacks when using a vehicle,
so that the cylindrical plunger after assembly is directly over the central area to be
tested. Fit the jack (in the fully retracted position), extension rods, force-
measurement device and cylindrical plunger on to the reaction load frame such that
the whole assembly hangs vertically with the lower face of the plunger about 25 mm
above the soil surface to be tested.
4. Carefully lower the cylindrical plunger so that its lower surface just comes into
contact with the soil. Ensure the assembly is vertical.
5. Place a sufficient number of surcharge discs, one on top of another, around the
central test area and plunger to correspond with the specified overburden pressure
for the test.
6. Apply a seating force to the plunger. Record the reading of the force-measuring
device as the initial zero reading (because the seating force is not taken into account
during the test) or reset the force measurement device to read zero.
7. Reset to zero the penetration measurement gauge or record its initial zero reading.
8. Start the test so that the plunger penetrates the soil at a uniform rate of 1 ± 0.2 mm
per minute, and at the same instant start the clock.
9. Record the force measurement in kN at intervals of penetration of 0.25 mm, to a total
penetration not exceeding 7.5 mm.
10. At the completion of the test, the equipment is dissembled and cleaned before
storing.
 PRACTICAL
CALIFORNIA BEARING RATIO TEST

DATA SHEET

CALIFORNIA BEARING RATIO (CBR)

( TEST METHOD BS 1377 : PART 9 : 1990)
PROJECT :
CONTRACTOR :
MATERIAL :
SAMPLE DESCRIPTION : DATE :

RESULTS

Penetration (mm) Dial Gauge Force (kN)

0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
4.75
5.00
5.25
5.50
5.75
6.00

Force (kN) = Dail Gauge x Coefficient factor

 PRACTICAL
CALIFORNIA BEARING RATIO TEST

SUMMARY
Calculations

Penetration at 2.5 mm, CBR = _____________% 2.5 = Force (KN) X 100

Penetration at 5.0 mm, CBR = _____________%
13.2
IN SITU CBR = ____________%
5.0 = Force (KN) X 100
20

From the data, plot the graph of Force Applied to Plunger (kN) versus Penetration of Plunger
(mm).

QUESTIONS
1. Why do we have to take values at 2.5mm and 5mm in the CBR test of soil?
2. Why should the CBR value corresponding to 2.5mm be more than 5.0mm
penetration?
3. Why do we use the greater CBR (2.5mm or 5mm deeper) instead of the minor one?

Prepared by: Approved by:

______________________________________ ______________________________________
MOHD FAHMI BIN ABDUL RAHMAN ASSOC. PROF DR. NORSHUHAILA BINTI
MOHAMED SUNAR
Date/Tarikh : FEBRUARY 2019
Date/ Date/Tarikh : FEBRUARY 2019