Example 8.1 – Pavement design using LR1132
Design is required for a new pavement to be constructed in 2006. The annual
average daily traffic for commercial vehicles on the opening day will be 1500.
Growth rate =4%
Subgrade CBR =3%
Design life =20 years
Assume a bituminous roadbase is to be used.
Solution
where
F 0 = 1500
r =0.04
n = 20
P = 1
Therefore:
Mid-term year = 2016
Therefore:
Design traffic =16.3 ¥3.5499
=57.86 million standard axles say 60 msa
CBR =3%
Therefore:
Subbase thickness=310 mm subbase or 150 mm subbase plus 350 mm
capping.
Roadbase+surfacing=375 mm, assuming a bituminous roadbase (wet-mix
roadbase is unsuitable and lean-mix roadbase results in surfacing of 200 mm
on top of the lean-mix roadbase of 250 mm).
tFF rD
nttF=-
=
=+()
=¥()
=
=
+
-
+
Ê
Ë
ˆ
̄
Ê
Ë
ˆ
̄
=
+
-
+
Ê
Ë
ˆ
̄
()∏∏2016 1945
71
1
1500 1 04
2220
035
093 0082
026
092 0082
10
39
035
093 0082
026
092 0082
10
39
02
10150071 71 2220 1550.
.
..
.
..
.
.
.
..
.
..
.
.
commercial vehicles in the mid-term year(()Ê
Ë
ˆ
̄
=-¥()
=-
=
3 987 3 07 0 14238
3 987 0 4371
3 5499
...
..
.
Tn=¥()()-
=¥ ¥
=
365 1500
104 1
004
365 1500 29 78
16 3
.^20
.
.
. million
TF
r
r
n Pn
=()()+ -
365
11
0