| Penetration(mm) | Applied Load (kg) |
|---|---|
| 0.50 | |
| 1.00 | |
| 1.50 | |
| 2.00 | |
| 2.50 | |
| 4.00 | |
| 5.00 | |
| 7.50 | |
| 10.00 | |
| 12.50 |
1. If the initial portion of the curve is concave upwards, apply correction by drawing a tangent to the curve at the point of greatest slope and shift the origin. Find and record the correct load reading corresponding to each penetration.
C.B.R. = (PT/PS) X 100
where PT = Corrected test load corresponding to the chosen penetration from the load penetration curve. PS = Standard load for the same penetration taken from the table above.
2. C.B.R. of specimen at 2.5 mm penetration = .
3. C.B.R. of specimen at 5.0 mm penetration =
4. The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the C.B.R. value at 2.5 mm will be greater than at 5 mm and in such a case/the former shall be taken as C.B.R. for design purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test should be repeated. If identical results follow, the C.B.R. corresponding to 5 mm penetration should be taken for design