CALIFORNIA BEARING RATIO (CBR) METHOD
description
Transcript of CALIFORNIA BEARING RATIO (CBR) METHOD
![Page 1: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/1.jpg)
CALIFORNIA BEARING RATIO (CBR) METHOD
Typical Testing Machine
![Page 2: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/2.jpg)
Introduction
• The California Bearing Ratio devised by engineers of the California Division of Highways in nine years period to 1938.
• Most universally accepted pavement design methods.
• A standard penetration-type load-deformation test is carried out, and using the values obtained from the test from an empirical design chart, the pavement thickness are calculated.
![Page 3: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/3.jpg)
CBR LABORATORY TEST
Specimen may be• Prepared• In-situ
Mould • 150mm diameter• 127.3mm height• Separate base plate• A collar
![Page 4: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/4.jpg)
• The specimen is soaked and the expansion is measured.
• Load is applied by the loading frame through a cylinder plunger of 50mm diameter and penetration is measured.
• Rate of penetration is maintained at 1.25mm/minute.
• Loads are recorded for 2.5 and 5.0mm.• Load is expressed as a percentage of the
standard load at the respective deformation level, and is known as the CBR value.
![Page 5: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/5.jpg)
CBR Equipment
Typical Testing Machine Soaking Samples
![Page 6: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/6.jpg)
CBR Test – Load-Penetration Measurement
CBR Test – Sample Preparation
CBR Equipment
![Page 7: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/7.jpg)
California Bearing Ratio (CBR)
• Load a piston at a constant rate
• See what load it takes to make it penetrate a known amount
![Page 8: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/8.jpg)
CBR Equation
yxCBR 100
x = material resistance or the unit load on the piston (pressure) for 2.5 mm or 5 mm of penetration
y = standard unit load (pressure) for well graded crushed stone. For 2.5 mm of penetration = 1000 psi For 5.0 mm of penetration = 1500 psi
![Page 9: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/9.jpg)
General Soil Type USC Soil Type CBR Range
Clean gravelsGW 40 – 80GP 30 – 60
Gravels with finesGM 20 – 60GC 20 – 40
Clean sandsSW 20 – 40SP 10 – 40
Sands with finesSM 10 – 40SC 5 – 20
Silts and clays
ML 15 or lessCL 15 or lessOL 5 or lessMH 10 or less
CH (LL>50%) 15 or lessOH 5 or less
Typi
cal C
BR R
ange
s
![Page 10: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/10.jpg)
California Bearing Ratio Equipment
California Bearing Ratio Vs Moisture content
![Page 11: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/11.jpg)
CBR DESIGN METHOD
• In this method, the CBR values are used to determine the total thickness of the flexible pavement and its various layers.
• Following are the graphs used in the design of the pavement thickness.
![Page 12: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/12.jpg)
Flexible Pavement Design Using CBR (Road Note 31)
![Page 13: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/13.jpg)
![Page 14: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/14.jpg)
![Page 15: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/15.jpg)
![Page 16: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/16.jpg)
![Page 17: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/17.jpg)
![Page 18: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/18.jpg)
![Page 19: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/19.jpg)
![Page 20: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/20.jpg)
![Page 21: CALIFORNIA BEARING RATIO (CBR) METHOD](https://reader035.fdocuments.in/reader035/viewer/2022081421/56815c85550346895dca99aa/html5/thumbnails/21.jpg)