CBR is the ratio expressed in percentage of force in step with unit region required to penetrate a soil mass with a popular round plunger of fifty mm diameter on the fee of 1.25 mm/min to that required for corresponding penetration in a general fabric. The ratio is typically determined for penetration of two.Five and 5 mm . Whilst the ratio at five mm is continually better than that at 2.Five mm, the ratio at five mm is used. cbr test
The following table gives the standard hundreds adopted for one-of-a-kind penetrations for the usual fabric with a C.B.R. Fee of 100%.
Penetration of Plunger (mm) wellknown Load (kg)
Desk 1 : fashionable Load Values at Penetration
For Railway Formation motive, the take a look at is performed on remoulded specimens that are compacted dynamically.
The technique covers the laboratory method for the willpower of C.B.R. Of remoulded /compacted soil specimens in soaked kingdom.
2. Equipment Required
Fig. 1: CBR take a look at apparatus
Which include Loading device with capacity of atleast 5000 kg and geared up with a movable head or base which allows Plunger of 50 mm dia. To penetrate into the specimen at a rate of one.25 mm/ minute.
Fig. 2: CBR mildew with Base Plate, live Rod and Wing Nut
Internal dia. 150mm and peak 175mm with a removable perforated base plate of 235mm dia. And 10mm thickness. Internet potential – 2250 ml; conforming to IS-9669:1980 (Reaffirmed-2016).
A removable extension collar of 60 mm peak.
148 mm in diameter and forty seven.7 mm in height together with deal with.
One annular steel weight and several slotted weights weighing 2.Five kg every, 147 mm in diameter, with a principal hollow 53 mm in diameter.
Fig. Three: Compaction Rammer
Weight – four.89 kg with a drop 450 mm.
IS 2720(element 16):1987 strategies of take a look at for soils: Laboratory determination of CBR (2d revision). Reaffirmed- Dec 2016.
RDSO file No. RDSO/2009/GE: G-0014 – pointers and Specification for design of Formation for Heavy Axle Load.
Coaching Of test Specimen:
1. Remoulded specimen: The check material need to bypass 19 mm IS sieve and retained on 4.Seventy five mm IS sieve.