沥青混合料低温裂纹扩展演化行为分析

Low Temperature Crack Propagation and Evolution of Asphalt Mixture

以悬浮密实、骨架密实和骨架空隙这3种典型骨架结构沥青混合料为试验对象,通过间接拉伸试验(IDT),从宏观角度分析了骨架结构对沥青混合料低温裂纹扩展演化行为的影响;采用颗粒随机生长算法建立了沥青混合料离散元模型,结合数值分析,从裂纹类型、数量、裂纹能量释放率及裂尖应力场等细观尺度,对3种典型骨架结构沥青混合料低温裂纹扩展演化特征进行了分析.结果表明:在骨架空隙、骨架密实及悬浮密实骨架结构下,沥青混合料内部耗能速率提高,储能速率下降,裂纹能量总释放率增大,从能量角度证实悬浮密实型沥青混合料发生破坏时需要更多的能量;悬浮密实型沥青混合料内部更不易出现应力集中,有利于抑制剪应力场的出现,从而减少Ⅱ型裂纹数量.

Three typical structure asphalt mixtures,such as suspend-dense structure,skeleton-dense structure and coarse-aggregate-skeleton structure,were used as test subjects to analyze the influence of crack propagation from a macro prespective through the indirect tensile test(IDT).Combined with the numerical analysis,heterogeneous discrete element models for asphalt mixtures were established by the random particle-based growth algorithm.The crack evolution characteristics of three asphalt mixtures under low temperature were analyzed through four aspects:the change in the number and proportion of micro cracks,the energy release rate,and crack tip stress field.The results indicate that in terms of the time-domain variation of the crack energy release rate G(t),as changes of the spatial distribution of the aggregate in the coarse-aggregate-skeleton,skeleton-dense and suspend-dense asphalt mixture,the internal energy consumption rate increases,while the energy storage rate reduces,and thus increasing the total crack energy release rate.It indicates that more energy is required when the suspend-dense asphalt mixture is fractured.In terms of the stress field distribution in the crack tip region,compared with the coarse-aggregate-skeleton and skeleton-dense asphalt mixture,the interior of suspend-dense asphalt mixture is less likely to appear the phenomenon of stress concentration,which is beneficial to suppress the occurrence of shear stress field,thereby reducing the number of modeⅡcracks.