海洋环境下预应力混凝土管桩耐久性损伤机理与水平承载性能退化规律研究

Prestressed concrete pipe pile foundation served in marine environments is not only subjected to lateral loading, such as wind, waves, tides and sea ice, but also long-term seriously exposed to chloride environments. Chloride-induced steel corrosion can cause the deterioration of structural strength and flexural stiffness, and the degradation of long-term resistance of pile foundation subjected to lateral loading, which has seriously affected the durability of prestressed concrete pipe piles exposed to marine environments. Therefore, it is essential to conduct the systematic research on the durability damage mechanism and deterioration law of lateral bearing behavior of prestressed concrete pipe piles exposed to marine environments. Based on the chloride penetration mechanism in prestressed concrete pipe piles, a durability damage theoretical model of prestressed concrete pipe piles due to chloride penetration is established. A time-dependent reliability analysis method for assessing the durability life of prestressed concrete pipe piles exposed to marine environments is proposed. By conducting the indoor model tests on model piles, the attenuation laws of structural strength and flexural stiffness of prestressed concrete pipe piles are analyzed. The nonlinear research on the horizontal bearing capacity and lateral deformation of existing prestressed concrete pipe piles is conducted by means of analytical and numerical simulation methods. The computational analysis theory of horizontal bearing capacity and lateral long-term deformation of existing prestressed concrete pipe piles is proposed. The deterioration law of lateral bearing behavior of existing prestressed concrete pipe piles exposed to marine environments is then analyzed.

服役于海洋环境中的预应力混凝土管桩基础不仅承受着风、海浪、潮汐和海冰等水平荷载的作用，还将长期暴露于严重的氯盐侵蚀环境中。氯离子侵蚀引起的钢筋锈蚀会导致桩身结构强度、刚度的不断劣化、以及水平荷载作用下桩基长期抗力的不断衰减，已经严重地影响了预应力混凝土管桩的耐久性。因此，有必要对海洋环境下预应力混凝土管桩耐久性损伤机理与水平承载性能退化规律进行系统研究。本项目基于氯离子对预应力混凝土管桩的侵蚀机理，建立海洋环境中氯离子侵蚀预应力混凝土管桩耐久性损伤理论模型，提出其耐久寿命时变可靠度分析计算方法。通过对模型桩开展室内模型试验，探讨海洋环境下预应力混凝土管桩桩身结构强度、刚度的衰减规律。采用解析法和数值模拟等方法，对海洋环境下在役预应力混凝土管桩水平承载力与侧向变形开展非线性研究，建立其水平承载力与侧向长期变形分析计算理论，进一步分析研究海洋环境下在役预应力混凝土管桩水平承载性能的退化规律。

服役于海洋环境中的预应力混凝土管桩不仅承受风、海浪、潮汐和海冰等水平荷载的作用，还将长期暴露于严重的氯盐侵蚀环境中。氯离子侵蚀引起的钢筋锈蚀会导致桩身结构强度、刚度的不断劣化、以及水平荷载作用下桩基长期抗力的不断衰减，已经严重地影响了预应力混凝土管桩的耐久性。因此，有必要对海洋环境下预应力混凝土管桩耐久性损伤机理与水平承载性能退化规律进行系统研究。本项目基于氯离子对预应力混凝土管桩的侵蚀机理，建立海洋环境中氯离子侵蚀预应力混凝土管桩耐久性损伤理论模型，提出其耐久寿命时变可靠度分析计算方法。通过对模型桩开展室内模型试验，探讨海洋环境下预应力混凝土管桩桩身结构强度、刚度的衰减规律。采用解析法和数值模拟等方法，对海洋环境下在役预应力混凝土管桩水平承载力与侧向变形开展非线性研究，建立其水平承载力与侧向长期变形分析计算理论，进一步分析研究海洋环境下在役预应力混凝土管桩水平承载性能的退化规律。研究结果表明，对流作用对对流区氯离子侵蚀有显著影响。氯离子对流扩散导致氯离子浓度增长，且对流区氯离子浓度增长相较于稳态扩散区更为显著。预应力混凝土管桩耐久寿命的失效概率随表面氯离子浓度、氯离子表观扩散系数、锈蚀速率、弹性模量和体积膨胀率的增大而逐渐增大，随临界氯离子浓度、龄期系数、抗拉强度和管桩保护层厚度的增大而逐渐减小。海洋环境中预应力混凝土管桩的水平承载性状有明显的时变特性。随着暴露时间的延长，桩身抗弯刚度呈非线性衰减，桩身水平位移和桩身负剪力最大值逐渐增大，桩身弯矩逐渐减小。当循环次数较小时，随着循环位移水平的增大，桩基的水平极限承载力退化较缓慢；当循环次数和循环位移水平较大时，桩基的水平极限承载力退化较为显著。本项目研究成果将为海洋环境下在役预应力混凝土管桩基础耐久性评价、剩余使用寿命预测和水平承载力评估提供理论基础。