Page 101 - Lecture Notes DCC3113

b. Design life

The design life refers to the span of time between the initial opening to traffic until the pavement
requires a strengthening overlay. The design life should not be confused with the pavement life since
the pavement life can be extended by routine maintenance and rehabilitation. The typical design life is
10 years.

The design life on JKR Design Method is suggested for 10 years. The design life begins from the road
starts in use for traffic until the maintenance is required.

c. Sub-grade condition

In case of varying CBR for 1m depth of sub-grade, mean CBR is determined as follows:

3
1/3
CBRm = [(h1CBR1 1/3 + h2CBR2 + … + hnCBRn ) / (1000)]
1/3

Where:
CBRm = mean CBR for that location
CBR1, CBR2, … CBRn = CBR of soil strata
h1, h2, … hn = thickness of soil strata (mm)
h1 + h2 + … + hn = 1000 mm

A minimum CBR of 5% is recommended for pavements that have to support traffic volumes
corresponding to Traffic Classes T2 through T5.

For road pavements that designed for large volumes traffic (Traffic Classes T4 and T5), a minimum sub-
grade strength corresponding to CBR of 12% is recommended. For pavements design purposes, the use
of average CBR or sub-grade modulus test results is not recommended.

d. Drainage

To ensure the safety of the travelling public, careful consideration must be given to remove the runoff
from the roadway through the structure of the pavement drainage facilities.

7.2.2 Explain traffic loads and axle weight

Figure 7-5: Vehicle Classifications

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