CBR or California Bearing Ratio is a ratio between the penetration load of a layer of soil or pavement against standard materials carried out with the same depth and penetration speed. The implementation of cbr testing is regulated directly in the standards set by the government. This CBR method is a combination of penetration loading experiments, both in the field and in the laboratory. It is also used for the road planning method, the thickness or severity of the road is determined by the CBR value.
The values stated in the CBR are used as the basis for pavement planning contained in road embankments, the amount depending on how many classes of roads are desired. The basic soil condition will get better if the CBR value is higher.
However, if the original CBR value is low, the construction on the road will become more easily damaged.
This CBR value can be increased by compaction, but in practice, it will refer to the value stated on the optimum moisture content and maximum dry weight.
The quality of the original soil bearing capacity is one of the strengths found in road construction, which is the basic material. CBR test was also carried out to determine the bearing capacity of the subgrade of the road.
As for the basis of the next pile road pavement planning, it is known using the CBR value.
If the resulting CBR value does not meet the required carrying capacity standard, a soil replacement process must be carried out where the value is better than the CBR value, as well as mixing originating from other locations.
This is done when the compaction test in the laboratory using the standard proctor method on the original soil has been carried out. Usually, the method is used by taking soil samples in the field, then carrying out the CBR test by using the CBR test tool in the laboratory.
An example of a report from CBR itself can be seen from the following example:
If the maximum amount of dry density is 1.99 g / cm3 then how much CBR is there at the dry density with a size of approximately 95% (maximum dry density). The answer is:
Counting 95% of 1.986 cm3, the result is 1.89 g / cm3
As for the calculation, the dry density is 1.89 cm3 with a CBR size of 52%.
The report from this CBR test must include the following:
- Compaction energy
- Moisture content in compaction
- Dry density
One of the functions of the CBR data in the field is to plan and evaluate the thickness of the flexible pavement layer.