Design a flexible (1,000,000 ESAL) and a rigid (3,000,000 ESAL) pavement. Based
ID: 1885612 • Letter: D
Question
Design a flexible (1,000,000 ESAL) and a rigid (3,000,000 ESAL) pavement.
Based on the highway classification, assume a reliability and use standard deviation of So=0.4
a. Design an asphalt pavement (with HMA and crushed stone base on top of the subgrade. Assume the moduli of HMA and crushed aggregate base materials to get layer coefficient.
b. Design the slab thickness for a doweled jointed plain concrete pavement on subgrade, with HMA shoulder. Assume the material properties and other parameters, if necessary.
Explanation / Answer
(a) Flexible pavement:
ESAL=1x106
S=0.4
Let us assume the remaining data
Mr for asphalt=450,000 lb/in2
Mr for base=30000 lb/in2
Mr for sub grade=9000 lb/in2
Design servicability loss=2
Reliability=99%
From the above data, we get the structural numbers from the AASHTO charts
The structure number is always a function of the modulus of resilience of the next lying layer
SN1=a1d1
a1=coefficient for the modulus of HMA for resilient modulus of 450,000 lb/in2
a1=0.44
SN1=2.7
2.7=0.44(d1)
d1=6.13 in
Consider 6.2 in as the first layer
SN1*=6.2x0.44=2.728
SN2=3.6
a2=0.12
D2=SN2-SN1/(a2m2)
D2=3.6-2.728/(0.8x0.14)
D2=7.785 in
Use 8 in as sub base
The flexible pavement consists of 6.12 in as H.M.A and 8 in sub base layer above the top of subgrade
(b) Rigid pavement:
ESAL=3x106
S=0.4
Assume a reliability of 95%
k=72 lb/in3
Ec=5x106 psi
Sc=650 psi
J=3.2
Cd=1.0
Design servicability loss=2%
All the above mentioned values are assumptions
From the AASHTO charts we get
Match line value=68
For an estimated ESAL of 3x106 the slab thickness of the given concrete pavement has a thickness of 8 in
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