【作者】 吕光印；

【导师】 郝培文；

【作者基本信息】 长安大学 ， 道路与铁道工程， 2008， 硕士

【摘要】 针对柔性基层沥青路面Top-Down裂缝,结合我国柔性基层沥青路面的工程实践,对轮胎-路面交互作用下的柔性基层沥青路面结构进行力学分析,研究其受力状况和温度状况,揭示沥青路面Top-Down开裂机理,探讨减缓Top-Down开裂的措施与方法。研究子午线轮胎的构造和传力机制,根据实际轮胎-路面接触应力,将接触区域简化为五个长度和宽度一定的矩形区域,结合子午线轮胎“泊松效应”,将轮胎-路面接触应力简化为垂直、横向和纵向接触应力,采用有限元软件ABAQUS,建立三维非线性轮胎-路面三向接触应力有限元模型,计算及分析表明:柔性基层沥青路面的受力机制导致其容易产生Top-Down开裂;面层厚度大于15cm,面层基层模量比大于4的路面结构,有助于减缓Top-Down开裂;轮组数量多、负载小、胎压介于0.6-0.8MPa的行车荷载,可以减缓Top-Down开裂的发生和发展;层间接触状况良好的路面结构,整体受力,有利于力的传递,可降低Top-Down开裂的几率,并运用数理统计方法,分析不同因素对Top-Down开裂影响的显著性。以柔性基层沥青路面的横断面作为研究对象,采用ABAQUS有限元程序,建立沥青面层预含不同深度Top-Down初始裂缝的二维有限元模型,研究不同降温幅度对沥青面层的力学影响,结果表明:轮胎-路面反复作用后存在微裂纹的沥青路面,在急剧的降温及升温循环过程中可能导致面层产生Top-Down裂缝;在降温过程中,路面结构不同深度处,路表应力最大,随着深度的增加,Mises应力和拉应力逐渐减小;初始裂缝深度越长,降温过程中应力强度因子KI越大,也就越容易开裂;随着降温幅度的增加,拉应力、应力强度因子KI均迅速增加,Top-Down裂缝的发展速度也就越快。综合轮胎-路面接触应力、温度、路面结构和材料特性,可以得出:荷载型裂缝开裂初期呈现V字形,裂缝竖直向下发展,这是路表拉应力反复作用下的第一阶段I型张开型疲劳裂缝。第二阶段,裂缝发展至路表下5-10cm左右后与竖直方向成一定角度斜向发展,这是由于剪应力随着深度的增加逐渐增加,在路表下5-10cm处出现最大值,这时剪应力成为Top-Down发展的主要诱因,所以第二阶段为II型剪切型裂缝;温度应力引发的是I型张开型裂缝。更多还原

【Abstract】 Based on the structure of asphalt pavement with flexible base in china, the mechanical model of asphalt pavement structure influenced on tire-asphalt pavement interaction was set up to specify the mechanical response of Top-Down cracking and search for measures in prevention and cure Top-Down cracks.Based on the real tire-asphalt pavement contact stress, the structure and load transfer mechanisms of radial tire, tire- asphalt pavement contact area was partition to five rectangles. Based on the Poisson effect of the radial tire treads structure, tire- asphalt pavement contact stress was predigested to the vertical contact stress, the transverse contact stress(perpendicular to the tire traveling direction), the longitudinal contact stress(parallel to the tire traveling direction). Three-dimensional nonlinear models were set up in ABAQUS to simulate tire-asphalt interaction. The numerical analysis results show that the mechanical response result in Top-Down cracking in the structure of asphalt pavement with flexible base; If AC surface thickness exceed 15cm, the modulus ratios between AC surface and base less than 4, the pavement structure is beneficial to prevent Top-Down cracking; Small wheel load, more wheel number, inflation pressure between 0.6-0.8MPa and continuous interlayer Contact Conditions are advantage factors for prevention of Top-Down cracks. An exploration of relation between above parameters and Top-Down cracking with the mathematical statistics method is analyzed.Two-dimensional nonlinear models were set up in ABAQUS to simulate Top-Down low-temperature cracking of asphalt pavement with flexible base, Study on Top-Down crack fracture length and temperature drop range, The numerical analysis results show that after cooling process, asphalt pavement with microcracks cause Top-Down cracking; In cooling process, tensile stress at surface is the biggest in pavement; Mises stress and tensile stress gradually reduce with the depth increased. The longer the initial crack depth, the greater the stress intensity factor KI in cooling process, the easier Top-Down cracking. With increase cooling rate, stress intensity factor KI are rapidly increasing, Top-Down cracks develop will sooner.Based on tire-pavement contact stress, temperature, pavement structure and material properties, the numerical analysis results show that the initial of load-caused Top-Down cracks show V-Shape; Top-Down cracks which develop along Vertical direction, is fatigue cracks in the first step; In the second step, when Top-Down crack developed under the surface about 5-10cm, the direction of Top-Down cracks have a certain oblique angle with Vertical direction. At the depth of 5-10cm, Shear stress which achieve the greatest, turn into the major incentive; temperature crack is I-type crack.更多还原