Paper Information

Journal:   MODARES CIVIL ENGINEERING JOURNAL   APRIL 2017 , Volume 17 , Number 1 #F0062; Page(s) 127 To 134.
 
Paper: 

INVESTIGATING THE EFFECTS OF TIRE TYPE AND AXLE LOAD ON CRACKING OF ASPHALTIC PAVEMENTS USING FINITE ELEMENT METHOD

 
 
Author(s):  TAHERKHANI HASAN*, JALALI MASOUD
 
* CIVIL ENGINEERING DEPARTMENT, UNIVERSITY OF ZANJAN
 
Abstract: 

Cracking is one of the major modes of failure in asphaltic pavements. Structural cracks occur in two forms of top-down and bottom-up cracking. Bottom-up cracking occurs due to the fatigue of asphaltic materials under repetition of tensile strain at the bottom of asphaltic layer. Top-down cracking (TDC) is among the major forms of asphaltic pavement distresses that significantly affects the serviceability and development of structural failure. Interaction of tire and pavement plays a key role in the initiation of TDC. This study utilizes viscoelastic analysis -using finite element modeling- to evaluate the influence of axle loads and tire configuration on the top-down and bottom-up cracking (BUC) in typical unreinforced and reinforced asphaltic pavement structures. Reinforcing by glass-grid geogrid is selected for the reinforced structure.
The highest vertical tensile strain at the surface and the highest horizontal tensile stress at the bottom of asphaltic layer are related to the TDC and BUC, respectively. Viscoelastic behavior is assumed for the asphaltic layer and linear elastic behavior is assumed for the base, sub-base and sub-grade. Prony series is used for characterizing the viscoelastic behavior of asphaltic layer. Using the tire pressure of 600kPa, effects of three axle load levels of 5, 8.2 and 15 ton and two tire configurations (conventional dual tire assembly and super single tire) on TDC and BUC have been investigated. Results show that the highest tensile strain at the surface occurs at the edge of super single tire and dual tires, with a higher values for the single tire. However, the location of the highest tensile strain shifts to the central region of dual tire with increasing axle load level. The results also show that under axle load of 5 and 8.2 ton, top-down cracking initially occurs at the inner edges of the tires, while under axle load of 15 ton its occurrence between the tires is more probable than in the other zones. For the pavement without reinforcement, the highest tensile strain at the surface is higher than that at the bottom under dual tires; however, under super single tire, the critical tensile strain at the surface is lower than that at the bottom of asphaltic layer. The results show that geogrid reinforcement is more effective in reducing the critical tensile strain at the bottom of asphaltic layer than that at the surface. This indicates that the reinforcement of pavement using geogrid at the bottom of asphalt layer is more effective on the bottom up cracking than on the top down cracking. In addition, geogrid reinforcement is more effective in reducing the critical strains under single tire than under dual tires. The rate of increase in the critical tensile strain at the surface with increasing axle load is more than that of the critical tensile strain at the bottom of asphaltic layer. Among bottom-up cracking (BUC) and TDC, BUC is more sensitive to the variations of tire type. By comparison, the super single tire created more TDC damage ratio than the dual tires assembly, in both reinforced and unreinforced pavements. However, the damage ratio due to the super single tire in unreinforced pavement is more than in reinforced pavement.

 
Keyword(s): ASPHALT PAVEMENT, TOP-DOWN CRACKING, AXLE WEIGHT, TIRE TYPE, GEOGRID
 
References: 
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