CBR (California Bearing Ratio) is a soil bearing capacity experiment developed by the California State Highway Department. The principle of this test is penetration testing by inserting objects into the test object. In this way, it can be assessed the strength of the subgrade or other materials used to make pavements. Soil strength is tested by the CBR test according to the standards set by the government. The soil strength value is used as a reference to whether or not it is necessary to stabilize after being compared with what is required in the specifications. Meanwhile, if you want to perform this test safely and effectively, we highly recommend you hire the experts of cbr test from a trusted company.
CBR testing is a comparison between the penetration load of a material against a standard material with the same penetration depth and speed. The value of CBR is measured at penetration of 0.1 inches and penetration of 0.2 inches, then the value from two calculations are compared based on the predetermined standard, whie the biggest result is taken.
This test value is the ratio between the pressure necessary to penetrate the ground with a 3-inch square round-section piston with the speed of 0.05 inch/minute to the pressure necessary to penetrate a standard material. The purpose of this CBR test is to determine the CBR value at the variation of compaction water content. To determine the strength of the subgrade layer using the CBR experiment, a value is obtained which is then used to determine the required pavement thickness above the layer with a certain CBR value. Testing the soil’s CBR value may be done in a lab. Subgrade in the construction of a new road is the original soil, stockpile, or excavated soil that has been compacted until it reaches a density of 95% of the maximum density. Thus the carrying capacity of the subgrade is the value of the ability of the soil layer to bear the load after which the soil is compacted. It is called the CBR of point plan and due to it is arranged in the lab, it is called the CBR lab. The higher the CBR value of the soil (subgrade), the thinner the pavement layer above it, and the smaller the CBR value (low soil bearing capacity), the thicker the pavement layer on top will be according to the load it will bear.
Lab CBR may be divided into 2 types, they are:
- CBR soaked laboratory (soaked design CBR)
- Laboratory CBR without immersion (Unsoaked Design CBR)
In immersion laboratory CBR testing, the implementation is more difficult because it requires relatively greater time and cost compared to laboratory CBR without immersion. Meanwhile, from the CBR laboratory test results without immersion, so far it has always produced a greater soil bearing capacity compared to the CBR of the immersed laboratory.
That’s it for the info regarding the CBR test that we may share with you in this article. We hope this info can help you to understand the CBR test better, and so you can do it safely and properly in the future.