基于港珠澳大桥结构混凝土耐久性设计，本文开展了现场混凝土的质量检测研究，在此基础上完成了港珠澳大桥施工阶段各个构件混凝土耐久性评估与再设计，为工程竣工验收与服役期管理提供了数据支持。本文首先汇总分析了实验室混凝土测得的抗压强度和氯离子扩散系数，以及在预制沉管隧道现场实体构件上无损测得的表面透气性系数、表面电阻率及保护层厚度。分析表明沉管抗压强度和氯离子扩散系数均满足控制规程的质量要求，保护层厚度合格率基本满足预期。沉管表面透气性系数普遍较低，尤其是56d龄期数据，表明预制节段现场混凝土结构致密。表面电阻率符合正态分布，并随混凝土龄期增长呈现出稳定的增大趋势。透气性和电阻率在数值上总体呈负相关，但不足以回归出定量关系。在现场检测数据的基础上，本文然后对氯盐侵入过程进行了施工阶段的评估。研究回顾了基于氯盐腐蚀的耐久性评估模型，总结分析了模型各个参数的统计特征，考虑了附加防腐蚀措施对模型的影响，在此基础上采用Monte-Carlo方法计算结构各个构件的120年失效概率Pf及可靠指标β，提出了结构初步维护方案和不同工况下的工程建议；计算结果表明大气区和水下区构件的可靠指标较高，可120年免维护；浪溅区构件需要120年耐久性维护预案。收费站暗桥和C匝道桥墩身内部、沉管隧道内部如有海水渗入时，按浪溅区工况计算所得120失效概率超过10%，在这些构件施工与构造中需要重点监测内部海水渗漏过程，并建立相应的耐久性再评估与再设计流程；沉管隧道竣工后如有海水渗入，则需要启动阴极保护措施，启动时间可根据海水渗漏面积比例和预定维护水平计算得到。本文最后进行了耐久性再设计过程研究，并以竣工评估后的沉管隧道的耐久性预案研究、DB01非通航孔桥浪溅区使用期中的维护方案研究为例展示了耐久性再设计方法。通过计算得出了在三个不同维护水平下，沉管阴极保护启动周期与海水渗入面积比例的关系曲线。并在一组模拟实测暴露数据的基础上，更新了DB01非通航孔桥120年可靠指标及失效概率时变曲线，运用全寿命周期成本方法，确定了水平-2耐久性维护方案为最优方案。
This study investigates the quality of concrete based on the durability design of the HongKong-Zhuhai-Macao sea link project, and then performs the durability assessment and redesign of all structural concrete members of the HZM Bridge. This work provides data support for construction quality control and acceptance as well as service life management.First of all, the compressive strength and chloride diffusion coefficient obtained from the laboratory, along with the covercrete thickness, air permeability as well as electrical resistance obtained from in-situ through non-destructive tests, are summarized and analyzed. The results show that both the compressive strength and chloride diffusion coefficient of the immersed tube tunnel achieve the expected construction quality. The relatively low air permeability indicates that structural concrete of tunnel has high compactness. The electrical resistance obeys normal distribution and is correlated strongly with the hardening age. It can be found that the air permeability and electrical resistance are qualitatively inversely correlated. Then the durability risk is assessed for chloride penetration based on the acquired data during construction phase. The assessment model for the chloride penetration is reviewed, and the parameters of the model along with their statistical features are discussed. The additional protective measures are also taken into consideration in the model. The reliability index of 120 years is obtained through Monte-Carlo method. The results show that the structural members in atmospheric zone and immerged zone own relatively high reliability index and therefore can be exempted from maintenanc; The failure probability of most structural members in splashing zone is between 1-5%, thus durability maintenance planing is needed; The internal side of the buried toll bridges, C ramp bridge and immerged tube tunnel could reach high failure probability (above 10%) in case of sea water infiltration. For this reason, it’s important to monitor the water infiltration of these structural members during construction and service life, and the corresponding reassessment and redesign are also needed. Cathodic protection mearsures of the tube tunnel are needed in case of water infiltration, and the startup time can be determined according to the water infiltration intensity and maintenance level. Then the principle and method of durability redesign through life cycle costing (LCC) method are discussed, and the durability maintenance plans of the tube tunnel and DB01 non navigable bridges in splashing zone are shown as durability redesign examples. The relation between the startup time of cathodic protection and the water infiltration intensity under different maintenance levels is obtained through calculation. The time-dependent curves of failure probability and the reliability index of DB01 non navigable bridges are updated based on a group of simulated exposure data, then the Level-2 maintenance plan is chose after comparison through LCC method.
