半刚性基层沥青路面车辙控制方法

Method  of Rutting Control for Semi-rigid Asphalt Pavements

研究生：曹林涛

指导教师：郭忠印教授

二○○九年元月

摘要

车辙是沥青混凝土路面主要损坏模式之一，通常采用沥青混合料车辙试验评价和控制路表车辙。调研发现，新材料的开发应用有效改善了沥青路面服务寿命，然而沥青混合料性能评价脱节于结构设计，沥青混凝土路面车辙问题依然严峻。本文主要研究半刚性基层沥青混凝土路面车辙控制方法，并建立基于结构性能需求的材料设计高温性能评价标准。

通过调研和试验室车辙试验分析，研究了车辙试验方法。提出采用蠕变率和相对变形指标共同评价车辙试验，并且采用现场初始空隙率取代设计空隙率成型车辙试件。通过野外加速加载试验与试验室车辙试验的比较分析，验证了改进车辙试验方法的可行性。

基于车辙及其外部影响因素的有限元模拟分析，以及材料设计性能评价，提出新型沥青层永久变形预估模型框架。通过大量的车辙试验，采用回归分析的方法初步确立永久变形预估模型的参数系数。通过现场加速加载试验，基于车辙等效原则，修正试验室预估模型。鉴于温度和交通轴次月分布差异性，提出以月为单元的永久变形增量计算方法。

运用弹性层状体系理论和有限元方法，结合沪宁高速环道试验和桐庐试验段加速加载试验，分析了沥青层竖向变形分布特征。结果表明，对于沥青层，其弹性变形比例与实测竖向变形比例具有良好的一致性。据此，可以采用弹性变形比例把半刚性基层沥青路面路表容许车辙分配给自然层。

鉴于采用不同性能材料分层铺筑面层的实际，现阶段路表容许车辙整体检验方法无法体现对自然层的合理检验，不能排除因薄弱自然层导致整体车辙损坏的可能性。为此，提出基于厚度分层容许永久变形检验的车辙控制新概念和方法。基于此，推导出沥青混合料设计的高温性能技术要求计算方法，并最终建立适用于半刚性基层结构的沥青混合料车辙试验评价新标准。该标准体现交通等级、温度分区以及结构层位等对高温性能的差异性要求。 

通过收集车辙调研数据对本文预估模型和车辙试验评价标准进行初步检验，结果表明它们能够满足工程应用需要。

最后，关于进一步工作的方向进行了简要的讨论。

关键词：沥青路面，车辙，沥青混合料，车辙试验,  加速加载试验，永久变形预估模型，分层容许永久变形检验，车辙试验评价标准

ABSTRACT

Rutting  is one of main damage modes of asphalt concrete pavements, and wheel tracking  tests of asphalt mixtures are commonly used to evaluate and control surface  rutting depth. Investigation showed that the service life of asphalt  pavements was effectively improved through development and application of new  materials. But due to the performance evaluation of asphalt mixtures  separated with structural design, rutting problem of asphalt pavements  remained grimly. Rutting control method of semi-rigid asphalt pavements was  studied in this paper, and high-temperature performance evaluation standard  of material design based on performance requirement of structural design was  established.

Through  investigation and analysis on laboratory wheel tracking tests, wheel tracking  test method was studied. Both Creep Slope and Percentage of Rut Depth were  recommended to evaluate wheel tracking test results. Field initial air voids  were also recommended to substitute desin air voids to control the molding or  prepareing of tracking samples. Through the comparison between field  accelerated loading test and laboratory wheel tracking test, the feasibility  of improved wheel tracking test was verified.

Based  on finite element simulation analysis of rutting and external factors, and in  view of the need of performance evaluation during material design phase, the  basic framework of permanent deformation predictive model of asphalt layers  was put forward. Through abundant laboratory wheel tracking tests, parameter  coeffcients of permanent deformation predictive model were preliminary  established by regression analysis method.Through field accelerated loading  tests and based on the principle of rutting equivalent, calibration of  laboratory predictive model was conducted. In view of the difference of  monthly distribution of temperature and traffic repeated times, monthly  increment approach of permanent deformation was put forword.

Based  on circular track test for Shanghai-Nanjing expressway and accelerated loaded  facility test in Tonglu pavements，characteristic  of vertical deformation distrubition of asphalt layers was analyzed by  elastic layered theory and finite element method. Results showed that for  asphalt layers, the proportion of elastic deformation and that of measured  vertical deformation enjoyed a good consistency. Accordingly, the surface  tolerated rutting depth of semi-rigid asphalt pavements could be assigned to  natural layers by the proportion of elastic deformation.  

In  view of the actuality of asphalt pavements paved by layers with different  materials, natural layers can’t be reasonably tested during current surface  tolerated rutting depth test method, and the likelihood of rutting failure of  holistic pavements resuted from failure of natural layers can’t be ruled out.  Therefore, new rutting control concept and method based on tolerated  permanent deformation checkouts by layers was put forward. Based on this,  calculation method of high-temperature technical requirements of asphalt  mixtures design was put forword. New evaluation standard of wheel tracking  tests for asphalt mixtures of semi-rigid asphalt pavements was finally  established, which embodied differential high-temperature technical  requirements of asphalt mixtures in terms of traffic grading, temperature  subarea, layer position and etc.

Through  collecting and combing rutting investigation data, the predictive model and  recommended evaluation standards of wheel tracking tests for asphalt mixtures  were preliminary conducted to test. The results showed that they met the need  of engineering application.

In  the finality, the problems requiring further studies are discussed.

Key  Words: asphalt pavements, rutting, asphalt  mixtures, wheel tracking test, accelerated loading test, permanent  deformation predictive model, tolerated permanent deformation checkouts by  layers, evaluation standard of wheel tracking test for asphalt mixtures