CALIFORNIA BEARING RATIO TEST

1. Goal
CBR is the ratio expressed in percent of force according to unit location required to penetrate a soil mass with a cbr test
Popular round plunger of fifty mm diameter on the price of one.25 mm/min to that required for
Corresponding penetration in a standard material. The ratio is commonly determined for penetration of 2.5
And 5 mm . When the ratio at five mm is continuously better than that at 2.Five mm, the ratio at 5 mm is
Used.
The following table offers the standard loads adopted for distinctive penetrations for the same old fabric
With a C.B.R. Price of 100%.
Penetration of Plunger
(mm)
Widespread Load
(kg)
2.5 1370
Five.0 2055
Table 1 : widespread Load Values at Penetration
For Railway Formation motive, the check is performed on remoulded specimens which are compacted
Dynamically.
The method covers the laboratory method for the determination of C.B.R. Of remoulded
/compacted soil specimens in soaked state.
2. Equipment Required
Fig. 1: CBR take a look at equipment
Including Loading gadget with ability of atleast 5000 kg and prepared with
A movable head or base which enables Plunger of 50 mm dia. To penetrate into
The specimen at a fee of one.25 mm/ minute.
Fig. 2: CBR mold with Base Plate, stay Rod and Wing
Nut
Cylindrical mildew:
Inner dia. 150mm and height 175mm with a detachable perforated
Base plate of 235mm dia. And 10mm thickness. Internet ability – 2250
Ml; conforming to IS-9669:1980 (Reaffirmed-2016).
Collar
A removable extension collar of 60 mm peak.
Spacer Disc
148 mm in diameter and 47.7 mm in height at the side of deal with.
Weights
One annular steel weight and several slotted weights weighing 2.Five kg
Each, 147 mm in diameter, with a significant hole 53 mm in diameter.
Fig. Three: Compaction Rammer
Weight – four.89 kg with a drop 450 mm.
Three. Reference
IS 2720(component 16):1987 techniques of check for soils: Laboratory determination of CBR (2d revision).
Reaffirmed- Dec 2016.
RDSO file No. RDSO/2009/GE: G-0014 – suggestions and Specification for design of Formation for
Heavy Axle Load.
4. Procedure
Instruction Of take a look at Specimen:
1. Remoulded specimen: The take a look at cloth need to pass 19 mm IS sieve and retained on 4.75 mm IS
Sieve. The dry density for a remoulding shall be both the sphere density or the value of the maximum
Dry density expected by means of the compaction test (Heavy Compaction test as in step with IS 2720 (element-eight) –
1983, for Railway Formation). The water content material used for compaction will be the superior water
Content or the sphere moisture because the case can be.
2. Dynamic Compaction: A representative pattern of the soil weighing about 4.5 kg or more for
Quality grained soil and 5.5 kg or greater for granular soil shall be taken and combined thoroughly with water.
If the soil is to be compacted to the maximum dry density at the greatest moisture content, the
Genuine mass of the soil required will be taken and the vital quantity of water brought so that the
Water content material of the soil pattern is equal to the determined foremost moisture content material.
3. Fix the extension collar and the bottom plate to the mold. Insert the spacer disc over the bottom. Region
The clear out paper at the top of the spacer disc.
4. Observe Lubricating Oil to the internal side of the mould. Compact the combination soil within the mould using heavy
Compaction. I.E. Compact the soil in 5 layers with 55 blows to every layer by way of the 4.89 kg rammer.
5. Get rid of the extension collar and trim the compacted soil cautiously at the extent of pinnacle of mold, by
Way of a immediately part. Any holes developed on the floor of the compacted soil by way of elimination of
The coarse fabric, shall be patched with the smaller length cloth. Do away with the perforated base
Plate, Spacer disc and clear out paper and file the mass of the mould and compacted soil specimen.
Region a disc of coarse clear out paper at the perforated base plate, invert the mold and compacted soil
And clamp the perforated base plate to the mould with the compacted soil in touch with the clear out
Paper.
6. Region a clear out paper over the specimen and location perforated plate on the compacted soil specimen in
The mould. Placed annular weights to produce a surcharge identical to weight of base cloth and
Pavement, to the closest 2.5 kg.
7. Immerse the mold meeting and weights in a

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