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.