温湿荷载下连续配筋混凝土路面早期开裂机理与裂缝主动控制方法

Punchout is recognized as the most fatal structural distress in Continuously Reinforced Concrete Pavements (CRCP), and is found mostly developed at the clusters of closely spaced transverse cracks. Recently, the active control method, early entry saw cut method, could eliminate the potential of the occurrence of the uniform crack pattern and thus reduces the risk of punchout development in the long-term of CRCP. However, the determination of the appropriate timing and depth at which the saw cut should be made is still problematic in practice, and it should be assessed from a theoretical point of view. To resolve these problems, this study firstly develops a procedure to predict the early age temperature and moisture development of a concrete pavement. In order to correlate the concrete properties in field and laboratory conditions for accurate predicting the cracking, degree of hydration based descriptions of the early age concrete properties, tensile strength, elastic modulus, coefficient of thermal expansion, fracture toughness, are given based on experimental tests. Then, the concrete stress history at early age is calculated by the superposition principle, by considering the time-dependent relaxation of early age concrete and the degree of restraint of early age CRCP. Using the above proposed stress prediction models and the estimated early age concrete properties, a fracture mechanics based procedure is developed to calculate the saw cut depth and saw cut timing for the active crack control method based on field climate and construction conditions. This study can provide theory foundation and technology support for early age performance evaluation and elimination of the risk of punchout development of CRCP.

冲断是连续配筋混凝土路面（CRCP）的首要病害，其主要发生在密集裂缝处。横向裂缝主动控制方法可有效避免密集裂缝等不利裂缝分布的产生，但目前CRCP裂缝主动控制实践中，诱导缝深度、诱导缝切缝时间仍根据经验确定，尚缺乏系统的理论依据。本课题紧扣现场条件下早龄期混凝土路面板温湿特性与混凝土强度发展规律，开展温湿荷载下CRCP早期开裂机理与裂缝主动控制方法研究。基于热传导和水分扩散方程，采用有限差分法，描述早龄期水泥混凝土路面温湿特性及其变形发展规律；基于叠加原理和应力增量法，考虑应力松弛的影响，构建施工期间CRCP温湿荷载应力计算模型；基于断裂力学理论，建立温湿荷载作用下带诱导缝的CRCP横向开裂预估模型，探究在内外因素影响下的裂缝主动控制方法。研究成果将为连续配筋混凝土路面早期性能评估、减少冲断破坏提供理论依据与技术支撑。

冲断是连续配筋混凝土路面（CRCP）的首要病害，其主要发生在密集裂缝处。横向裂缝主动控制方法可有效避免密集裂缝等不利裂缝分布的产生，但目前CRCP裂缝主动控制实践中，诱导缝深度、诱导缝切缝时间仍根据经验确定，尚缺乏系统的理论依据。本课题紧扣现场条件下早龄期混凝土路面板温湿特性与混凝土强度发展规律，开展温湿荷载下CRCP早期开裂机理与裂缝主动控制方法研究。首先基于热传导和水分扩散方程，构建早龄期水泥混凝土路面湿度场预测模型，并利用MATLAB编制相应计算程序；考虑路表水分蒸发散热和养护条件的影响；通过试验测量早龄期混凝土试件温度场、湿度场与混凝土应变，验证所建立的早龄期混凝土温湿度预测模型；通过室内试验探究早龄期混凝土相对湿度变化与其对应干缩变形之间的联系。随后通过室内试验，研究对CRCP温湿荷载应力与开裂影响显著的早龄期混凝土关键参数发展规律，包括混凝土弹性模量、抗拉强度与断裂韧度；考虑龄期与温度对早龄期混凝土性能指标发展的影响，研究并建立基于水化度的早龄期混凝土关键参数预估模型。最后，基于叠加原理和应力增量法，考虑应力松弛的影响，构建施工期间CRCP温湿荷载应力计算模型；基于断裂力学理论，建立温湿荷载作用下带诱导缝的CRCP横向开裂预估模型，探究在内外因素影响下的裂缝主动控制方法。研究成果将为连续配筋混凝土路面早期性能评估、减少冲断破坏提供理论依据与技术支撑。

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