To determine the stress loading path suitable for true triaxial tests on asphalt mixtures, enabling accurate testing and analysis of their mechanical behavior under complex stress states. This study employed a triaxial sliding interlocking true triaxial testing system to conduct stress–strain testing and analysis of asphalt mixtures under three loading paths: equal-proportion loading, constant-rate loading, and sequential loading. It revealed the strain variation patterns of asphalt mixtures under different loading paths and comprehensively evaluated the applicability of the three loading paths for asphalt mixtures through error analysis. Results indicate: Under the equal-proportion loading path, the average strain error in all three directions is approximately 10%, demonstrating optimal deformation consistency and measurement accuracy. As the maximum principal stress σ1 increases, the strain evolution patterns and magnitudes in the intermediate (σ2) and minimum (σ3) principal stress directions remain generally consistent. With increasing σ2, specimen deformation primarily develops along the least constrained σ3 direction. Under the constant-rate loading path, strain errors in both σ2 and σ3 directions exceeded 400%. Strain curves for both directions exhibited distinct “plateau” characteristics, with the plateau length in the σ3 direction varying up to tenfold. The magnitude of the difference between σ1 and σ2 or σ3 was the key factor influencing plateau length, and a “reversal” feature also appeared in the σ2 direction. The sequential loading path yielded the highest strain testing errors in all three directions, with σ2 exhibiting the greatest error exceeding 1200%. Both the σ2-ɛ2 and σ3-ɛ3 curves displayed longer “plateau” lengths than the constant-rate loading path, and the maximum “reversal” length surpassed the “plateau” length. Under both constant-rate and sequential loading paths, strain errors in the σ2 direction showed significant variation across different stress combinations. This indicates that the stress loading path and the duration of the stress holding phase are key factors contributing to large errors. The research findings can provide reference for experimental studies on the mechanical properties of asphalt mixtures under complex three-dimensional stress states.

True triaxial strain characteristics of asphalt mixture under different stress loading paths

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发表日期：

2025年12月3日

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Qinxue Pan,
Yifu Huang,
Jia Hu,
Songtao Lv,
Jianlong Zheng

摘要

To determine the stress loading path suitable for true triaxial tests on asphalt mixtures, enabling accurate testing and analysis of their mechanical behavior under complex stress states. This study employed a triaxial sliding interlocking true triaxial testing system to conduct stress–strain testing and analysis of asphalt mixtures under three loading paths: equal-proportion loading, constant-rate loading, and sequential loading. It revealed the strain variation patterns of asphalt mixtures under different loading paths and comprehensively evaluated the applicability of the three loading paths for asphalt mixtures through error analysis. Results indicate: Under the equal-proportion loading path, the average strain error in all three directions is approximately 10%, demonstrating optimal deformation consistency and measurement accuracy. As the maximum principal stress σ₁ increases, the strain evolution patterns and magnitudes in the intermediate (σ₂) and minimum (σ₃) principal stress directions remain generally consistent. With increasing σ₂, specimen deformation primarily develops along the least constrained σ₃ direction. Under the constant-rate loading path, strain errors in both σ₂ and σ₃ directions exceeded 400%. Strain curves for both directions exhibited distinct “plateau” characteristics, with the plateau length in the σ₃ direction varying up to tenfold. The magnitude of the difference between σ₁ and σ₂ or σ₃ was the key factor influencing plateau length, and a “reversal” feature also appeared in the σ₂ direction. The sequential loading path yielded the highest strain testing errors in all three directions, with σ₂ exhibiting the greatest error exceeding 1200%. Both the σ₂-ɛ₂ and σ₃-ɛ₃ curves displayed longer “plateau” lengths than the constant-rate loading path, and the maximum “reversal” length surpassed the “plateau” length. Under both constant-rate and sequential loading paths, strain errors in the σ₂ direction showed significant variation across different stress combinations. This indicates that the stress loading path and the duration of the stress holding phase are key factors contributing to large errors. The research findings can provide reference for experimental studies on the mechanical properties of asphalt mixtures under complex three-dimensional stress states.