Pavement Structural Analysis of the Design Recommendations for ...

Pavement Structural Analysis August 2004
Report No. 15953-2/1 ARA-ERES Consultants
Where:
MR = Resilient modulus of the foundation soil, psi.
εv(Soil) = Vertical strain at the top of the foundation soil, in./in.
Table 4 summarizes the allowable or permissible vertical strain at the top of the sand
subbase and foundation soil for both the 20 and 40-year traffic levels. The vertical strains
at the top of the sand subbase and foundation soil were computed with EVERSTRS for
the AASHTO design, which are also included in table 4 (refer to Appendix C). As
shown, the computed vertical strains are significantly less than the permissible vertical
strains for both layers. Thus, distortion in the unbound layers should not be a problem for
the proposed structure.
Table 4 Limiting criteria that were used to evaluate the design layer thickness
(refer to figure 1) for a 20 and 40-year analysis periods.
Design Criteria
Limiting or Permissible
Values
20-Year 40-Year
Analysis Analysis
17
Computed
Responses
(See Note 1)
Design 80-kN (18-kip) ESALs 22,694,400 56,000,000 ---
Equation 1;
Tensile strain at the
20% Cracking
bottom of the HMA
Figure 13;
layers, in./in.
10% Cracking
Vertical Strain in the HMA layers,
in./in.
Vertical strain at the top of the nonfrost
susceptible sand material, in/in.
Vertical strain at the top of the
foundation soil, in./in.
Permissible maximum surface
deflection, in.
Unbound layer modulus ratios
0.000100 0.000075
0.000070 0.000053
0.0000497
0.000091 0.000068 0.00009196*
0.000284 0.000227 0.0000993
0.000235 0.000187 0.0000889
0.0175 0.0158 0.0108
Material and Thickness
Dependent, but