青藏高原寒冷地区沥青混合料真实环境冻融作用损伤累积与定量表征

In the Qinghai-Tibet Plateau Cold Region, the frequent and violent freeze-thaw cycles have critical impacts on the performance and service level of asphalt pavement. Research on the deterioration of asphalt pavement performance under Freeze-Thaw cycles has been mostly concentrated on qualitative evaluation and variation trend analysis based on the laboratory simulation. However, the statistical research on the in-situ Freeze-Thaw cycles in the Qinghai-Tibet Plateau is few, and the fatigue damage cumulative of asphalt mixture under in-situ Freeze-Thaw cycles are also few. These lead to the notable difference between in-situ and laboratory results, and result in the discrepancy between theoretical research and reality. Based on the mathematical statistical theory, the laboratory test and field tracking monitoring, theoretical analysis and numerical modeling were combined and applied in this study. Numerical model of the Freeze-Thaw cycles between in-situ and laboratory were applied by investigating the statistics, quantification, evaluation, expression functions and prediction of the actual in-situ Freeze-Thaw action in the Qinghai-Tibet Plateau Cold Region. Meanwhile, the comprehensive multi-factor durability assessment numerical model of asphalt mixture under actual field Freeze-Thaw action was established, based on the Palmgren-Miner fatigue linear cumulative damage theory. This can reveal the asphalt mixture performance deterioration trends under actual in-situ Freeze-Thaw action in the Qinghai-Tibet Plateau Cold Region. The results are also able to give scientific guidance to mixture parameters design and pavement deterioration analysis under Freeze-Thaw cycles in the Qinghai-Tibet Plateau Cold Region.

青藏高原寒冷地区频繁剧烈的冻融作用，对沥青路面使用性能与服务水平产生严重危害。目前关于冻融作用下沥青路面损伤特性的研究，主要采用室内冻融循环模拟试验进行定性评价与规律分析，而关于真实环境冻融作用的统计量化以及沥青混合料环境冻融疲劳累积损伤等研究较少，易造成冻融作用研究与实际偏差较大，导致理论分析与实际不符。因此，本项目基于数理统计理论，采用室内试验与现场跟踪监测相结合、理论分析与数值模拟相对照的方法，建立真实环境冻融作用与室内冻融试验数值模型，开展青藏高原寒冷地区考虑沥青路面冻融破坏的真实环境冻融作用统计、量化、函数表征与预估等研究；基于Miner疲劳线性累积损伤理论，建立多因素综合作用下沥青混合料真实环境冻融耐久性评估数值模型，揭示青藏高原寒冷地区真实环境冻融作用下沥青混合料性能的衰变趋势。研究结果将为青藏高原寒冷地区路面材料参数及冻融作用下路面结构性能演变等提供相关科学依据。

针对青藏高原寒冷地区频繁剧烈冻融作用对沥青路面的危害，利用数理统计、模拟仿真、室内试验、理论分析等方法对真实环境冻融作用进行了系统的研究。基于青藏公路沿线6个典型区域近60年气象资料，对沿线气温与降水进行统计分析；基于沥青路面温度场研究，得到沥青路面结构层与气温对应关系，以此为基础提出冻融作用强度划分准则，对比分析了各区域不同冻融强度下冻融作用次数影响。研究表明：青藏公路沿线一年内超过140天发生冻融作用，超过80天发生强冻融作用。利用截尾正态分布反映了冻融作用次数关于冻结温度的变化，采用二维联合概率密度函数表征了同时考虑冻结温度与融化温度的冻融作用。基于Mann-Kendall检验、小波方法和R/S分析建立了青藏高原寒冷地区实际环境冻融作用次数预估模型。利用室内模拟试验研究了冻融作用对沥青混合料性能的影响，分别采用指数模型与Logistic模型表征混合料抗压性能随冻融作用的衰变趋势与损失率变化趋势，沥青混合料的抗压性能随冻融循环次数的增加呈减小趋势。利用Miner疲劳线性累积损伤理论，建立了多因素综合作用下沥青混合料真实环境冻融耐久性评估数值模型，揭示了青藏高原寒冷地区真实环境冻融作用下沥青混合料性能的衰变趋势，提出了沥青混合料真实环境冻融疲劳寿命预估方法。探索了利用相变等功能材料降低沥青混合料冻融破坏的问题。