30 June 2001
and for the base course are 121, 176, and 303 MPa (17,500, 25,500, and 44,000 psi),
respectively. These values are shown in Figure J-3.
c. Relationships. The relationships indicated in Figure I-1 can be expressed as
= a layer in the pavement system
En = resilient modulus (in psi) of layer n
En+l = the resilient modulus (in psi) of the layer beneath layer n
= the thickness (in inches) of layer n for base-course materials and as
for subbase-course materials. Use of these equation for direct computation of modulus values for
the examples given above yields the value indicated in parentheses in Figures I-2 and I-3. It can be
seen that comparable values are obtained with either graphical or computational determination of
the modulus value for either material.