不同碎石化效果下沥青加铺结构断裂力学分析
首发时间:2013-06-25
摘要:为了研究不同碎石化效果下沥青加铺结构的反射裂纹应力强度因子及其疲劳寿命,探讨了旧水泥混凝土路面沥青加铺结构断裂力学模型的不同有限元建模方式,认为,碎石化能防治反射裂纹的力学机理是水泥混凝土碎石化使原反射裂纹名义长度变短,反射裂纹可视为从碎石化层顶部开始萌生、扩展。据此,利用碎石化各子层(共3个子层)的模量和厚度变化模拟不同碎石化施工效果,从而建立碎石化加铺的断裂力学有限元模型。计算结果表明,应控制碎石化表层的最大矿料粒径、级配与优质级配碎石接近;碎石化表层厚度过大对沥青路面疲劳寿命是不利的;在不存在层间脱层的情况下,保持碎石化表层以下水泥混凝土的完整性对沥青路面疲劳寿命是有利的;由于共振碎石化(RPB)能够更好的控制碎石化表层粒径、级配和厚度及保持碎石化表层以下混凝土的完整性,共振碎石化效果优于多锤头碎石化(MHB);共振碎石化加铺的沥青路面疲劳寿命是直接加铺时4.0-6.8倍。
关键词: 沥青加铺结构 碎石化 反射裂纹 应力强度因子 路面疲劳寿命
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FRACTURE MECHANICS ANALYSIS OF ASPHALT OVERLAY STRUCTURE UNDER DIFFERENT RUBBLIZATION DEGREES
Abstract:In order to study the Stress-Intensity-Factor of reflection crack and fatigue life of asphalt-overlay under different rubblization degrees, different fracture mechanics Finite-Element-Method (FEM) models for asphalt-overlay on rubblized concrete are discussed. The discussions show that, the mechanics mechanism of rubblization to prevent from reflectioncrack is that the nominal crack length becomes shorter, as well as the initiation, expansion of reflective crack can be seen to begin from the top of gravel layer. With the rubblized concrete considered to be three-layer-media and its elastic modulus changed to simulate different rubblization degrees, the FEM model for asphalt-overlay on rubblized concrete is established. The numerical results show that, it is preferable to control the particle size and gradation of top-sub-layer in rubblized concrete to approach the quality-grading-macadam's. As the top-sub-layer in rubblized concrete becomes thicker, the fatigue life of asphalt-overlay becomes shorter. In the case of the interlayer-separation being absent, it is beneficial to maintain the integrity of cement concrete below the top-sub-layer. Moreover, the results indicate the reason why the effect of the Resonant Pavement Breaker (RPB) is better than that of the Multi-Head Breasker (MHB). The fatigue life of asphalt-overlay by RPB is 4.0-6.8 times compared with the fatigue life by direct-overlay.
Keywords: asphalt overlay Rubblization reflection crack stress intensity factor fatigue life
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