California Bearing Ratio Test (CBR)
The C.B.R. Method is used for finding the relative bearing ratio and expansion characteristics of soil of base, sub-base and sub-grade for the design of roads, pavements and runways.
Test can be made on all types of soils including sand, gravel, crushed stone etc. (Passing through 20mm IS sieve) C.B.R. test is used extensively for selection of materials and control of sub-grades. The procedure of test is very simple. A 50mm dia. penetration piston is forced in the test soil and loads required for the penetration to penetrate different depths are recorded by means of a proving ring fixed to the penetration piston assembly and a dial gauge. Both Laboratory C.B.R and field C.B.R apparatus are available.
AS PER IS: 2270 (PART-XVI)
California Bearing Ratio Apparatus is made both for laboratory and field use. CBR test is to evaluate the bearing capacity of soil for the flexible pavement design. It is extensively used for the selection of mater ials and cont rol of subgrades. The potent ial expansion/consolidation of the specimen is also measured before each test, under known surcharge weights.
This apparatus comprises of :
A hand operated load frame 50kN capacity, A mould of 150 mm. I.D. x 175 mm. high with clamping lugs complete with extension collar and perforated base plate made of gun metal. A cutting collar to fit mould body. A penetration piston assembly of 50 mm. diameter and a bracket for the dial gauge. A perforated swell plate of 148 mm. diameter with an adjustable stem and lock nut. A circular spacing disc of 148 mm. diameter x 47.7 mm. high complete with a removable `T' handle. A metal tripod for the dial gauge.
Surcharge weight :
annular _ 2.5 kg., 147 mm. diameter. Surcharge weight : slotted _ 2.5 kg., 147 mm. diameter.