粒料基层设计指标和控制模型研究

Study on Design Index and Model for Controlling Permanent Deformation of Granular Base Course

为提出控制粒料基层永久变形的设计指标并建立控制模型,采用两种级配碎石,3种围压和不同应力比为试验加载条件,利用重复荷载三轴试验和安定理论,研究了粒料的永久变形安定特性。为了克服试验加载次数的限制,对试验结果进行了统计回归和曲线拟合。根据拟合结果,利用试验曲线外延的方法,分析了粒料永久变形处于不同安定状态下的安定极限荷载,提出了在A区(塑性安定状态)内建立控制粒料基层永久变形设计模型的原则。利用分层应变总和法和美国力学经验法路面设计指南目前所采用的粒料层永久变形预估模型,计算了典型沥青路面结构的粒料基层永久变形,确定了粒料基层永久变形量和永久应变临界值标准,在此基础上提出了控制粒料基层永久变形的应力比设计指标,初步建立了基于室内试验的应力比与荷载作用次数回归公式的控制模型。

To introduce a design index and a model for controlling permanent deformation of granular base course for asphalt pavements,by adopting 2 types of graded macadam,3 kinds of confining pressure stresses and different stress ratios as test loading conditions,the permanent deformation shakedown characteristics of the graded macadam are examined using triaxial repeated load test based on shakedown theory. The methods of statistical regression and curve fitting are used to the testing result in order to overcome the limitation of the number of repeated loads. According to the fitting result,the method of extension of testing curves is used to analyze the limit stresses for shakedown under different shakedown statuses of permanent deformation of the aggregates,and the principle of establishing design model for controlling permanent deformation of granular base course in zone A（ plastic shakedown status） is put forward. The permanent deformation of granular base courses of typical asphalt pavement structures is calculated by way of layerwise strain summation method and the evaluation model for permanent deformation of granular base course currently adopted by U. S.Mechanical-Empirical Pavement Design Guide. Consequently,the critical standard values of the permanent deformation and the permanent strain of granular base courses are determined. Finally,the stress ratio as design index for controlling permanent deformation of granular base course is put forward,and the control model of regression formula between stress ratio and numbers of axial loading is initially created based on the laboratory test.