The California bearing ratio measures the associating subgrade value. It aims at evaluating the ground and its substrates strengths. The CBR testing was an initiative by the California Department of Transport. The testing has found use in road construction as well as in the development of airstrips and pavements. The concept of the CBR has spread and become applicable in many parts of the world. It gives its measurements inform of rates and can be expressed as a ratio or percentage. If you are looking for cbr testing in the UK try https://www.cbrtesting.com who will be able to give you a quote on cbr or plate testing services.
Usually, the bearing ratio for hard surfaces is higher than that of soft areas. The softness or hardness determines the amount of weight that can pass on the surface without any effect. For the roads scenario, bearing ratio means that the soil below the proposed road, which is also referred to as the subgrade, has to be tested for things such as its density. What is CBR testing?
The CBR testing is used in building roads and airstrips as well as other constructive pathways. The need to have correct load bearing amounts necessitates the CBR. Before this construction, CBR results are used to determine factors like the material thickness to be used so that when the newly constructed roads are ready for use, any load can be passed by the heavy vehicles with their cargos.
The road usage has to be left intact despite use. CBR testing, therefore, results in the development of high-quality roads that are predetermined in a load balancing aspect. The pressure exerted is determined by the force of the object and the area it’s exerted. Normally, the vehicles have a small area on the wheels that uses all its pressure on the road. Pressure is simply the ratio of force exerted on the area the object has.
CBR testing process involves performing a test on a soil sample whereby pressure is exerted to determine the maximum it can withhold. The soil sample is entered using standard plunder. Different kinds of soils have varying CBR value outcomes. Test results show that sub-base should have at least 80 percent CBR value to be dependable for any weight of the load to pass through it. For this reason, the results promote the importation of soils and other building materials with good density to ensure that the CBR recommended range ratio is met.
A CBR of 100 percent is the desire of an engineer. There are a lot of efforts done to achieve the ratio including the application of pressure to ensure the targeted CBR rate is met.
The CBR test is done explicitly for those particles that are not more than 20mm regarding size. Any size that goes beyond that cannot be handled in this test.
CBR testing on the ground involves slight ground levelling in preparation for the test. The 1935 mm2 cylindrical plunger is used and exerted to the intended ground at a specified rate. The process involves the use of a 4wd vehicle to source the reaction load needed to drive the CBR press as well as moving the CBR testing machinery.
Records are taken at regular intervals of time for the plunger penetration. Six to eight tests can be conducted in a day by each machine. The recorded measurement results are plotted on a graph. The slope of the graph has to be determined to obtain the CBR ratio.
The Test can still be done using portable machinery. Some companies also apply the use of Dynamic Cone Penetrometer in CBR testing. In general, these tests are aimed to test the ground fitness in the development of a road.
The CBR tests are also done to determine factors such as CBR value of the soil, Value of base course, the value of sub-base course, the thickness of road to be constructed and the maximum load that can use the particular highway on development.
CBR tests result in the building of quality, durable and safe roads and other pavements. There are many other reasons behind the use of CBR testing, which includes the following:
Conclusively, the testing is all about determining the penetration of the load on the ground it lays the pressure. Therefore the goal of CBR tests is to eliminate the penetration possibilities as loads pass over the built roads.