California bearing ratio


California bearing ratio

The California bearing ratio (CBR) is a penetration test for evaluation of the mechanical strength of road subgrades and basecourses. It was developed by the California Department of Transportation.

The test is performed by measuring the pressure required to penetrate a soil sample with a plunger of standard area. The measured pressure is then divided by the pressure required to achieve an equal penetration on a standard crushed rock material. The CBR test is described in ASTM Standards D1883-05 (for laboratory-prepared samples) and D4429 (for soils in place in field), and AASHTO T193.

The CBR rating was developed for measuring the load-bearing capacity of soils used for building roads. The CBR can also be used for measuring the load-bearing capacity of unimproved airstrips or for soils under paved airstrips. The harder the surface, the higher the CBR rating. A CBR of 3 equates to tilled farmland, a CBR of 4.75 equates to turf or moist clay, while moist sand may have a CBR of 10. High quality crushed rock has a CBR over 80. The standard material for this test in Crushed California Limestone which has a value of 100.

CBR=frac {p}{p_s} cdot 100 quad

External links

* [http://www.highwaysmaintenance.com/cbrtext.htm CBR]


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • California bearing ratio — The bearing ratio of soil determined by comparing the penetration load of the soil to that of a standard material. The method covers evaluation of the relative quality of subgrade soils but is applicable to sub base and some base course materials …   Aviation dictionary

  • California Bearing Ratio-Versuch — Der California Bearing Ratio Versuch (kurz CBR Versuch) ist eine Prüfmethode, mit deren Hilfe die Trägfähigkeit von Böden und hydraulisch gebundenen Schichten (eher selten) untersucht werden kann. Das Verfahren wurde ursprünglich für… …   Deutsch Wikipedia

  • California Institute of Technology — Motto The truth shall make you free [1] Established 1891 Type …   Wikipedia

  • Geotechnical investigation — Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil and rock around a site to design earthworks and foundations for proposed structures and for… …   Wikipedia

  • Geotechnical engineering — [ Boston s Big Dig presented geotechnical challenges in an urban environment.] Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. Geotechnical engineering includes investigating …   Wikipedia

  • Deep foundation — A deep foundation installation for a bridge in Napa, California, United States …   Wikipedia

  • Earthquake — For other uses, see Earthquake (disambiguation). Global earthquake epicenters, 1963–1998 …   Wikipedia

  • Landslide — This article is about the geological phenomenon. For other uses, see Landslide (disambiguation). Rockslide redirects here. For the comic book character, see Rockslide (comics). Computer simulation of a slump landslide in San Mateo County,… …   Wikipedia

  • Cone penetration test — A CPT truck operated by the USGS. The cone penetration test (CPT) is an in situ testing method used to determine the geotechnical engineering properties of soils and delineating soil stratigraphy. It was initially developed in the 1950s at the… …   Wikipedia

  • Dynamic load testing — of piles is a fast and effective method of assessing foundation bearing capacity that requires instrumenting a deep foundation with accelerometers and strain transducers and analyzing data collected by these sensors. The procedure is based on the …   Wikipedia


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.