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本文叙述一种以沥青混合料,密级配乳化沥青混合料或水泥改善乳化沥青混合料铺筑的路面结构厚度的简化设计法。在制定这种方法时采用弹性层状体系理论。文中验证了计算路面厚度时所用两项临界应变——处治层底面的水平拉应变和路基表面的垂直压应变。拉应变的容许值是根据室内疲劳试验并考虑了野外所遭到的裂缝缓慢扩展的时间而得出的。路基垂直应变标准是根据现场路面工作状态观测结果确定的。选用这项标准目的是尽可能减少路基因应力过大所产生的表面车辙。在设计中考虑了环境条件(特别是温度),乳化沥青混合料的固化作用及冰冻对路基强度的影响。为了确定混合料在予计的使用温度和固化条件范围内的劲度特性,采用了径向回弹模量装置。对其疲劳性能文中建议采用一个关系式来表示混合料的空隙率和沥青用量,从而对所要求的路面结构厚度有重大影响。就乳化沥青混合料而论,它较之混合料成型初期强度较低对设计厚度的影响要大得多。本文还简要地叙述了各设计步骤,以便工程师据以确定要求的路面厚度;提供了一个设计实例,其中附有设计计算表,以说明各设计图表和公式的正确用法。本设计方法不必使用计算机。但是,为了避免文中所述冗长的手工计算,已经按BASIC语言编写了简单的计算机程序。这些程序适用于以沥青、乳化沥青或水泥改善乳化沥青混合料铺成的路面的设计。本方法所用拉应变或疲劳标准,充分地予计到了圣地亚哥县试验基地通车七年后所观察到的10～20％的裂缝。对室内环道混合料工作状态的分析结果证明采用路基垂直应变或车辙标准是正确的。
This article describes a simplified design method for improving the thickness of the pavement structure paved with asphalt mixture, dense graded emulsified asphalt mixture or cement to improve the emulsified asphalt mixture. The elastic layered system theory was used in developing this method. The paper verifies the two critical strains used in the calculation of pavement thickness - the horizontal tensile strain at the bottom of the treated layer and the vertical compressive strain at the subgrade surface. The allowable value of tensile strain is based on the indoor fatigue test and taking into account the slow expansion of the cracks encountered in the field. The vertical subgrade strain criterion is based on the observation of the working conditions of the pavement. The purpose of selecting this standard is to minimize surface rutting caused by excessive stress in roadbed. In the design, environmental conditions (especially temperature), the curing effect of emulsified asphalt mixture and the influence of freezing on the subgrade strength were considered. In order to determine the stiffness characteristics of the mixture within the expected service temperature and curing conditions, a radial resilience modulus device was used. For the fatigue performance of the paper, a relation is proposed to express the voidage and asphalt content of the mixture, which has a significant impact on the required thickness of pavement structure. As far as emulsified asphalt is concerned, it has a much greater impact on the thickness of the design than the lower strength of the initial mixture. This article also briefly describes each design step so that engineers can determine the required thickness of the pavement. A design example is provided with a design calculation sheet to illustrate the correct usage of the design diagrams and formulas. This design method does not have to use a computer. However, in order to avoid lengthy manual calculations described in the text, a simple computer program has been written in the BASIC language. These procedures are applicable to the design of pavement with asphalt, emulsified asphalt or cement to improve emulsified asphalt mixture. The tensile strain or fatigue criteria used in this method adequately account for 10-20% of the fractures observed seven years after the San Diego County trial was opened to traffic. The analysis of the working condition of the indoor loop mixture proves that it is correct to adopt the vertical subgrade strain or the standard of rutting.