Parameter Optimization of Graded Macadam Transitional Layer for Inverted Asphalt Pavement Based on the Mechanical Response and Strength Standard

Chen Zhang,Yong Lei,Songtao Lv

doi:10.1155/2021/9945372

Abstract

To improve the durability of asphalt pavement with heavy traffic conditions in cold regions, the parameter optimization of graded macadam transitional layer (GMTL) for the inverted asphalt pavement based on the mechanical response and the strength standard was studied. The stress distribution laws of GMTL were studied with different loads by means of BISAR3.0. The influences of the thickness and the modulus of GMTL on the pavement stress were analyzed. The optimal thickness and the modulus range of the GMTL were determined. Combined with a self-developing real-time data acquisition and a processing system for aggregate attitude (RDAPS), the strength control standard of the GMTL was established. Finally, the performance of the optimized inverted asphalt pavement structure was verified through the MEPDG design method. The results show that the tensile stress at the bottom of the surface layer reduced by about 58%, and the shear stress in GMTL increased by about 17% when the modulus of GMTL increases from 300 MPa to 800 MPa. However, the change in modulus has no significant influence on the maximum shear stress in the asphalt surface layer and the tensile stress in the base layer bottom. When the thickness of GMTL increases from 12 cm to 20 cm, the tensile stress in the bottom of the base layer reduced by about 31%. Based on the mechanical results from simulation calculation and the technical indicator required in the field, the recommended optimal parameters of GMTL are the modulus of 700 MPa and the thickness of 18 cm. In addition, the spatial attitude angle ΦN of wireless intelligent attitude aggregate (WIAA), the compressive strength Rc standard, and the California Bearing Ratio (CBR) standard were analyzed, and the strength control standard of inverted asphalt pavement with GMTL was proposed, namely, CBR ≥ 354%, Rc ≥ 1.06 MPa, and ΦN ≤ 3°. A significant improvement in the resistance to crack can be seen in the inverted asphalt pavement when the optimized structure was applied. Taking the 20-year service life as an example, the top-down cracks reduced by 29.3% and the bottom-up cracks reduced by 32.6% in comparison to the original structure. The recommended structural parameters of GMTL could be used to guide the construction and design of inverted asphalt pavement in cold regions.

Highlights

Under the continuous effect of heavy traffic, the traditional pavement structure design method based on the multilayer elastic theory analysis is facing a severe challenge
The main distress types of the Inverted asphalt pavement (IAP) structure with graded macadam transitional layer (GMTL) are cracking in the surface layer, rutting, and shear failure in the base layer [12]. e shear failure of GMTL is essentially related to the shear deformation caused by the excessive shear stress in the structure. erefore, the shear strength reflecting the shear deformation ability should be used as the strength control index
Guo et al made an analysis on the control indicators based on the damage form of the graded crushed stone (GCS) layer of the flexible asphalt pavement structure. e result showed that 10 cm thickness of asphalt surface is a turning point of change curve for the tensile stress indicator of the asphalt layer and the shear stress indicator of the graded macadam layer [14]

Summary

Introduction

Under the continuous effect of heavy traffic, the traditional pavement structure design method based on the multilayer elastic theory analysis is facing a severe challenge. It is embodied in the following aspects: (1) the mechanical indexes considered are mainly tensile stress and compressive stress, which are too simple to analyze the damage mechanism of the current road under the complex traffic and climate condition. To improve the durability of asphalt pavement with heavy traffic conditions in cold regions, the parameter optimization of GMTL for IAP based on the materials mechanical response and strength standard was conducted in this study

Raw Materials and Experimental Methods

Mechanical Response Analysis

Results and discussion

Conclusion

Strength Control Standard of GMTL