Highway Engineering

196 Highway Engineering

Penetration Load

(mm) (kN)

2 11.5

4 17.6

6 22.2

8 26.3

10 30.3

12 33.5

Table 7.1Standard

force-penetration

relationship

(CBR =100%)

Example 7.1

A CBR test on a sample of subgrade yielded the data shown in Table 7.2.

Determine the CBR of the subgrade.

Solution

Penetration Load

(millimetres) (kN)

0.5 1.6

1.0 3.3

1.5 4.9

2.0 6.6

2.5 8.2

3.0 9.3

3.5 10.5

4.0 11.4

4.5 12.2

5.0 13.0

Table 7.2Laboratory

CBR results of sample

2

4

6

8

10

12

14

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

8.2 kN

13.0 kN

Figure 7.4CBR curve for subgrade sample tested.

Contd