Question

7. Use the AASHTO design method to determine the thickness of full depth AC pavement given the following information: subgrade resilient modulus is 10,000 psi; AC layer coefficient is 0.42; total ESAL on the design lane is 5x10°; reliability level is 95%; overall standard deviation is 0.40; initial serviceability index is 4.5; terminal serviceability index is 2.5; drainage coefficients for aggregate layers is 0.85. Show your work on the figure below 50 Design Serviceability Low APS 10 99.9 e 40 20 10 -90 70 - 60 50 Design Structural Number, SN Figure 19.10 Design Chart for Flexible Pavements Based on Using Mean Values for Each Input SOURCE From AASHTO Guide for Design of Pavement Seructures1993, AASHTO, Washington, D.C. Used by permission

Answer 1

Given data:

a1=0.42

ESAL=5x10⁶

R=95%

Step 1:

S=0.4

For the given data, from the charts

$\delta$ PSI=2

SN1=4

Step 2:

SN1=a1m1D1

4=0.42x0.85xD1

D1=11.2 in

Step 3:

Provide D=11.5 in as the total layered AC for the flexible pavement layer