CALIFORNIA BEARING RATIO (CBR) TES PDF

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Summary

The California Bearing Ratio Test (CBR Test) is a penetration test developed by the California State Highway Department (U.S.A.) for evaluating the bearing capacity of subgrade soil for design of flexible pavement....

Description

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

GEOTECHNICAL LABORATORY ECG428 OPEN-ENDED LAB SEMESTER 2

TITLE OF EXPERIMENT

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CALIFORNIA BEARING RATIO (CBR) TEST

DATE OF EXPERIMENT

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24TH JUNE 2020

NAME

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UiTM NO

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CLASS GROUP

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LECTURER

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LEVEL OF OPENESS

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3

MARKS

COMMENTS

INTRODUCTION

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5

BASIC CONCEPTS

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METHODOLOGY

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RESULTS&ANALYSIS

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DISCUSSION

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3

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CONCLUSION

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5

ORGANIZATION

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TOTAL MARKS

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL COURSE

GEOTECHNICAL LABORATORY

COURSE CODE

ECG428

LEVEL OF OPENNESS

Fully Open

CATEGORY

3

DEGREE OF OPEN-ENDED (%)

100

ENGINEERING PROPERTIES TEST

California Bearing Ratio (CBR) Test (With referenced to clause 7 of BS1377: Part 7: 1990) PREAMBLE

Introduction Level 3 laboratory activities refer to the condition where only the Preamble is given. Students are required to find the problem statement, ways & means and provide the answers to the given assignment using the creativity and innovativeness. The activity will enable the students to appreciate independent learning and prepare them for a much harder task of open-ended laboratory activities. The California Bearing Ratio Test (CBR Test) is a penetration test developed by the California State Highway Department (U.S.A.) for evaluating the bearing capacity of subgrade soil for design of flexible pavement. Tests are carried out on natural or compacted soils in water soaked or un-soaked conditions and the results so obtained are compared with the curves of standard test to have an idea of the soil strength of the subgrade soil. The CBR Test is a penetration test meant for evaluation of subgrade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement Objectives To determine the California Bearing Ratio of the subgrade soil. CBR is the ratio expressed in percentage of force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5 mm . When the ratio at 5 mm is consistently higher than that at 2.5 mm, the ratio at 5 mm is used. The following table gives the standard loads adopted for different penetrations for the standard material with a C.B.R. value of 100%. Penetration of Plunger (mm) 2.5 5.0 7.5 10.0 12.5

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Standard Load(kg) 1370 2055 2630 3180 3600

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FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

Learning Outcomes At the end of the laboratory activities, students would be able to: 1. acquire the understanding of engineering properties of soils in determination of the California Bearing Ratio 2. acquire the necessary skill to prepare sample and conduct force measuring device and the axial deformation gauges in performing standard laboratory 3. calculate and analyze data to report and present result in a proper engineering format.

PROBLEM STATEMENT

CBR test is widely used for the design of flexible pavement, thickness of the pavement. It helps to find the strength of the subgrade ,sub-base, base course. It gives parameter which can enable a designer to estimate the loads that can be taken by the soil.

Apparatus CBR mould, Filter paper, Water, Soil, Weighing scale, Rammer, Loading machine, Metal weight, Spacer disk, dial gauge, IS sieves, Penetration plunger. Procedure 1) 2) 3) 4) 5) WAYS & MEANS

6) 7) 8) 9) 10) 11) 12) 13) 14) 15)

Take 4.5-5 kg of soil and mix it thoroughly with required quantity of water (OMC) or field moisture content. The super disc is place at the bottom of the mould over the base plate and coarse filter paper is placed over the spacer disc. The moist soil is to be compacted over this in the mould by adopting either IS light or heavy compaction. After compacting the last layer, the collar is removed and the excess of soil above the top is evenly trimmed off. The clamps are removed and the mould with the compacted soil is lifted, leaving below the base plate and spacer disc is removed. A filter is placed on the base plate, the mould with compacted soil is inverted and placed over the base plate and clamps are tightened. Weight of 2.5-5 kg are placed over the soil in the mould. Then the whole mould is placed in the water tank to allow soaking for 4 days. A swelling measuring device are placed on the top edge of the mould and the spindle of the dial gauge is placed touching the top of the sample. Initial dial gauge readings are recorded and the test sample is kept undisturbed in the water tank. After 4 days of soaking, the mould is clamped over the base plate and the same surcharge weights are placed on the specimen as the test could be conducted. The completely assembly is placed under the loading machine. Penetration plunger is brought in contact with the top surface of the soil by applying 4 kg of load. The dial gauge of proving ring and the penetration dial gauge is set on 0. The load is applied through penetration rate 1.25 mm/min The load readings are taken at 0.0, 0.5, 1.0, 1.5, 2.0, 3.0,4.0, 5.0, 7.5, 10.0, 12.5 mm of penetration

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May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL

Complete the following: Name of Tester : __CBR TEST___ Date : __24/6/2020__ Sample No : ______1______ Proving Ring conversion factor : 0.0233 kN/div Container Number Mass of Container Mass of Container + Wet Soil Mass of container + Dry Soil Moisture Content, w Soil sample penetration (div) 12500 2500 3750 5000 6250

Soil sample penetration (mm) (1 div = 0.002 mm) 2.5 5.0 7.5 10.0 12.5

(g) (g) (g) (%)

Proving Ring Dial Reading (div) 17 24.7 30.2 32 35

1 95.5 888.6 832.4 7.09 Applied Load(kg)

157.37 228.65 279.57 291.70 324.01

C.B.R. = (Applied Load/Standard Load) x 100% At 2.5 mm RESULTS 157.37  100% 1370

11 .49% At 5.5 mm 

228.65 100% 2055

11 .13%

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May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL Draw graph between Load Versus Penetration and find CBR at 2.5mm and 5.0.

DATA ANALISIS

CBR at 2.5 mm = 11.49 %

CBR at 5.0 mm = 11.13 %

CONCLUSION DISCUSSION AND RECOMENDATIO N

In a conclusion, the value of CBR obtained from this experiment at 2.5mm and 5.0mm are 11.49% and 11.13% respectively. Thus, the objective is achieved.

The California Bearing Ratio ( CBR) test was developed by the California Highway Division as a method for classifying and evaluating soil-subgrade and baseline materials for flexible pavements. CBR is a measure of resistance of a material to penetration of a standard plunger under controlled density and moisture conditions. The CBR test may be performed in a remodeled or undisturbed sample. The test consists of causing a cylindrical plunger of 50 mm diameter to penetrate the material of the pavement component at 1.25mm / minute. The loads for 2.5mm and 5mm are recorded. This load is expressed as a percentage of the standard load at the respective deformation level to obtain the CBR value. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement. The value of CBR is closely associated with the characteristics of compaction, such as the moisture content, dry weight, energy conditions and the method of compaction. Compacted soil with a moisture content higher than optimum moisture content will have lower CBR value. The CBR value will be lower on the samples which are compacted at optimum wet but will be higher when the applied energy increased.

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May 2020_mm

FAKULTI KEJURUTERAAN AWAM UNIVERSITI TEKNOLOGI MARA SHAH ALAM LABORATORY MANUAL There are few advantages from CBR Test which are the CBR method adapts more quickly to airfield pavement design for immediate use than any other method. Other than that, the tests can be run either in the field or the laboratory for design, construction control, or evaluation of existing construction. It is primarily intended for subgrades but applicable to a wide range of different materials. Lastly, it can be performed by personnel relatively little experience and training

REFERENCES ;

I.

https://www.scribd.com/document/364037361/Cbr-Lab-Report

II.

https://www.aboutcivil.org/california-bearing-ratio-test.html

III. http://armyengineer.tpub.com/EN54537/EN545370124.htm IV. https://www.academia.edu/24893617/LAB_REPORT_ON_CBR_COMPACTION_TEST

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