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Several investigators have verified the validity of Burmister's
theory with the actual mechanical response of flexible pavements.
Foster and Fergus (37) have compared the results of extensive test
measurements on a clayey silt subgrade to theoretical stresses and
deflections based on Burmister's theory and reported satisfactory
agreement. The discrepancy between actual and theoretical stresses and
displacements can be mainly attributed to the assumption of a homoge
neous and isotropic material, the rate-dependent behavior of some
materials such as asphalt, and a circular loaded area representing the
wheel load. Nielsen (86) has made a detailed study in this area. His
review of the magnitude and distribution of stresses within a layered
system revealed regions where vertical and shearing stresses were criti
cal. His studies concluded that the layered-elastic theory is in every
respect consistent and that it is possible to establish fundamental
patterns of pavement performance based upon this theory. This suggests
that the elasticity theory could be used more extensively.
The moderators of the Fifth International Conference on the Struc
tural Design of Asphalt Pavements (76) concluded that the use of linear
elastic theory for determining stresses, strains, and deflections is
reasonable as long as the time-dependent and nonlinear response of the
paving materials are recognized. They noted that the papers presented
at the conference confirmed that multilayer elastic models generally
yield good results for asphalt concrete pavements.
Barksdale and Hicks (10) compared the multilayered elastic approach
with the finite element method and recommended the use of the former for
pavement analysis since only two variables are needed (modulus and
Poisson's ratio). Pichumani (91) used the BISAR computer program for