J. Shanghai Jiaotong Univ. (Sci.), 2008, 13(2): 206–210
DOI: 10.1007/s12204-008-0206-5
Mechanical Properties of Asphalt Pavement
Structure in Highway Tunnel
SHI Chun-xiang
1∗
(石春香), GUO Zhong-yin
2
(郭忠印)
(1. Shanghai Institute of Technology, Shanghai 200233, China; 2. Tongji University, Shanghai 200092, China)
Abstract: A linear full 3D finite element method (FEM) was performed in order to present the key design
parameters of highway tunnel asphalt pavement under double-wheel load on rectangular loaded area considering
horizontal contact stress induced by the acceleration/deceleration of vehicles. The key design parameters are
the maximum horizontal tensile stresses at the surface of the asphalt layer, the maximum horizontal tensile
stresses at the bottom of the asphalt layer and the maximum vertical shear stresses at the surface of the as-
phalt layer were calculated. The influencing factors such as double-wheel weight; asphalt layer thickness; base
course stiffness modulus and thickness; and the contact conditions among the structure layers on these key
design parameters were also examined separately to propose construction procedures of highway tunnel asphalt
pavement.
Key words: tunnel asphalt pavement structure; three-dimensional finite element method; horizontal force;
horizontal tensile stress; vertical shear stress
CLC number: U 452.2 Document code: A
Introduction
Almost all mechanistic flexible pavement design pro-
cedures determine the fatigue life of pavements by con-
sidering the tensile stress or strain at the bottom of
the asphalt layers. They implicitly assume that fa-
tigue cracks originate at the bottom of the asphalt lay-
ers and propagate upwards towards the surface of the
pavement. Assuming a uniform normal contact pres-
sure distributed over a circular contact area between
the tyre and the pavement surface, layered elastic the-
ory predicts that the maximum horizontal tensile stress
(strain) occurs at the bottom of bound layers directly
under the load, and the maximum horizontal compres-
sive stress (strain) occurs at the surface of the pavement
directly under the load
[1]
.
However, observations from cracked roads in the
UK
[2]
,theUS
[3−5]
, Japan
[6]
and in Northwest area of
China
[7]
have shown that the cracking originated from
the surface of the pavement rather than at the base,
particularly for thick flexible constructions.
More recently, researchers have hypothesized that
the surface cracking phenomenon may be related to
the highly non-uniform three dimensional contact stress
distribution measured between the tyre and the pave-
ment, inducing large horizontal tensile stresses (strains)
in the top section of the pavement structure
[8]
.Mea-
surements from free-rolling car and truck tyres have
Received date: 2007-05-28
Foundation item: Western Traffic Technology Funds
(No. 2002-318-000-23)
∗E-mail: [email protected]
shown that, in addition to the normal contact pressure,
there can be large transverse and longitudinal shear
stresses acting in the contact area.
Traditional layered elastic models of a pavement
structure typically assume that the load is applied as
a uniform vertical contact pressure distributed over a
circular contact area. Under these conditions the max-
imum horizontal tensile stress and strains are usually
predicted at the bottom of the asphalt layers, due to
the bending stresses induced by the loading. However,
on the tunnel asphalt pavements, it should be noted
that horizontal tensile stresses at the surface away from
the loaded area (due to the negative curvature of the
surface).
The elastic stiffness modulus of highway tunnel
bedrocks is high; the deterioration of well-constructed
pavement is not structural. Furthermore, when vehi-
cles enter the tunnels, drivers will decelerate vehicles
because of weak light and narrow space, and acceler-
ate vehicles when leaving the tunnels. There exist high
horizontal stresses (in the direction of travel) between
the tyre and the pavement surface.
The objective of this paper is to use a linear elas-
tic full 3D finite element (FE) program to present the
key design parameters of highway tunnel asphalt pave-
ment under double-wheel loads considering horizontal
contact stress induced by the acceleration/deceleration
of vehicles. The following key design parameters were
to be calculated: ➀ the maximum horizontal tensile
stresses σ
max
at the surface of the asphalt layer; ➁ the
σ
max
at the bottom of the asphalt layer; ➂ the maxi-
mum vertical shear stresses τ
max
at the surface of the
