【作者】 张鹏；

【导师】 黄承逵； 李清富；

【作者基本信息】 大连理工大学 ， 结构工程， 2007， 博士

【摘要】 本文在分析半刚性基层裂缝形成机理的基础上，提出了通过改善基层材料本身性能来提高半刚性基层抗裂性的措施，即在水泥稳定碎石中掺加聚丙烯纤维。通过大量试验，对聚丙烯纤维水泥稳定碎石的各种力学性能和抗裂性能进行了系统的研究，主要内容包括：(1)推导了半刚性基层收缩应力的计算公式，对影响最大收缩应力的各种因素及半刚性基层收缩裂缝产生的规律进行了分析，提出了相应的路面裂缝防治措施。(2)通过聚丙烯纤维水泥稳定碎石击实试验，确定了每组配合比试件的最大干密度和最佳含水量；根据规范中圆柱体标准试件成型的原理，自行设计了一套钢制梁式试模以及试件脱模方法。试验表明，所设计的试模及试件成型、脱模方法能较好地保证试件的最大干密度。(3)在大量试验的基础上分析了试验龄期、纤维掺量、水泥掺量对聚丙烯纤维水泥稳定碎石抗压强度、劈裂抗拉强度、抗压回弹模量、抗弯拉强度和抗弯拉弹性模量等的影响，并得出了相应的影响规律。结果表明：聚丙烯纤维的掺入对水泥稳定碎石的各种强度影响不大，但使回弹模量和抗弯拉弹性模量有显著的降低。(4)采用千分表机测法及应变片电测法分别对聚丙烯纤维水泥稳定碎石的干缩及温缩性能进行了测试。研究分析了试验龄期、纤维掺量、水泥掺量对聚丙烯纤维水泥稳定碎石平均干缩系数和温缩系数的影响。结果表明：聚丙烯纤维的掺入可以有效地减小水泥稳定碎石的干缩系数和温缩系数。(5)采用三点弯曲试验方法对水泥稳定碎石和聚丙烯纤维水泥稳定碎石的断裂性能进行了大量的试验研究，测得了试件的最大荷载、跨中挠度、预制裂缝嘴张开位移和裂缝尖端张开位移，并由此计算出了材料的断裂韧度和断裂能。试验结果表明：聚丙烯纤维的掺入对水泥稳定碎石的断裂韧度和断裂能均有提高，对水泥稳定碎石的临界裂缝嘴张开位移和临界裂缝尖端张开位移有略微的增大，但对极限裂缝嘴张开位移和极限裂缝尖端张开位移有明显的增大。聚丙烯纤维对水泥稳定碎石的裂后行为有很大改善，并且可以改善水泥稳定碎石的裂缝尖端位移场分布，能有效地增强水泥稳定碎石的断裂韧性。(6)采用灰色关联分析法对几种常用的抗裂性评价指标体系进行了对比分析，结果表明，评价半刚性基层材料抗裂性的最佳指标是干缩能抗裂系数和温缩能抗裂系数。通过试验，得出了聚丙烯纤维的掺入可以使水泥稳定碎石的干缩能抗裂系数和温缩能抗裂系数有明显的增大，显著地增强了其抗裂性。(7)运用纤维间距理论和乱向不连续纤维复合材料理论以及断裂力学的相关知识对聚丙烯纤维对水泥稳定碎石的增强抗裂机理进行了分析。得出影响聚丙烯纤维对水泥稳定碎石阻裂效应的因素主要有两个，即纤维与水泥稳定碎石基体之间的粘结力和水泥稳定碎石中纤维间距的大小。(8)在叶信高速公路铺筑了试验路段，并对试验路段进行了跟踪观测。由观测和取芯调查的结果可知，聚丙烯纤维对水泥稳定碎石基层的强度有一定的提高，使基层裂缝产生的数量减少、平均间距增大、裂缝率减小，显著地提高了基层抵抗收缩裂缝产生和发展的能力，从而有效地减少了沥青路面裂缝的产生。更多还原

【Abstract】 On the base of analyzing the forming mechanism of semi-rigid base course, this thesis presents a measure to advance the anti-cracking performance of semi-rigid base course by improving the properties of base materials, which is mixing polypropylene fiber into cement stabilized macadam. According to a great deal of tests, each mechanics property and anti-cracking performance of polypropylene fiber cement stabilized macadam were investigated systemically. The main content includes:(1) The formulae of shrinkage stresses of semi-rigid base course were deduced. This thesis analyzed each influencing factor of the maximum value of shrinkage stress and the cracking rule of semi-rigid base course. At the same time, the corresponding prevention measures of the cracks were presented.(2) According to the compaction test of polypropylene fiber cement stabilized macadam, the maximum dry density and optimum moisture content of each mix proportion were obtained. Based on the shaping principle of standard specimen in the criterion, a suite of steel beam models and the corresponding liftout method of the specimen were designed. The tests indicate that the designed model, shaping and liftout method can ensure the maximum dry density of the specimens.(3) On the base of large amount of tests, this thesis analyzes the impacts of testing period, fiber dosage and cement dosage upon the compressive strength, splitting tensile strength, compressive resilient modulus, flexural strength and flexural elastic modulus of polypropylene fiber cement stabilized macadam, and the corresponding impact rule was found. The results show that the addition of polypropylene fiber has little impact on each strength of cement stabilized macadam, but it can reduce the compressive resilient modulus and flexural elastic modulus evidently.(4) By adopting the method of millesimal gauges, the dry shrinkage property was measured, and by adopting the method of resistance strain gauge, the thermal shrinkage property was measured. The impacts of testing period, fiber dosage and cement dosage upon the average dry shrinkage coefficient and average thermal shrinkage coefficient of polypropylene fiber cement stabilized macadam. The results show that the addition of polypropylene fiber can reduce the dry shrinkage coefficient and thermal shrinkage coefficient of cement stabilized macadam effectively. (5) Adopting three-point-bending method, a large amount of experimental researches was carried on the fractural properties of cement stabilized macadam and polypropylene fiber cement stabilized macadam. During the course of the testing, the maximum load, mid-span deflection, crack mouth opening displacement, crack tip opening displacement was measured. Therefore, the fracture toughness and fracture energy of the material were calculated. The testing results indicate that the addition of polypropylene fiber can increase the fracture toughness and fracture energy of cement stabilized macadam. The fiber can increase the critical crack mouth opening displacement and critical crack tip opening displacement appreciably, buy it can increase the ultimate crack mouth opening displacement and ultimate crack tip opening displacement of cement stabilized macadam evidently. Polypropylene fiber can improve the property after the cracking of cement stabilized macadam and it also can extensively improve the strain filed ahead of the crack tip. The addition of polypropylene fiber improves the fracture parameters of cement stabilized macadam.(6) This thesis evaluates some kinds of common evaluation indices of anti-cracking performance applying grey relational analysis. The result shows that the optimal evaluation indices of anti-cracking performance of semi-rigid base course are dry shrinkage energy anti-cracking coefficient and thermal shrinkage energy anti-cracking coefficient. By the test, a conclusion is drawn that the addition of polypropylene fiber can improve dry shrinkage energy anti-cracking coefficient and thermal shrinkage energy anti-cracking coefficient of cement stabilized macadam, furthermore the anti-cracking performance is improved.(7) Applying fiber distance theory, disorder discontinuous fiber composite theory and the corresponding knowledge of fracture mechanics, the strengthening and anti-cracking mechanism of polypropylene fiber was analyzed. There are two main influencing factors of anti-cracking effect of polypropylene fiber on cement stabilized macadam, which are the bond strength between cement stabilized macadam and the fiber, and the fiber distance.(8) A length of test road was constructed in Ye-Xin expressway and the following observation was conducted. The observation and investigation of the core samples indicate that polypropylene fiber can increase the compressive strength to some extent. And it can decrease the number of cracks of base courses, enlarge the average distance between two cracks and decrease the crack ratio. The addition of polypropylene fiber can obviously improve the resistance to the forming and expanding of shrinkage cracks, and thus the cracks of asphalt pavements were restricted effectively.更多还原