This paper performs the durability assessment and maintenance planning of concrete structures during construction phase in the ongoing Ningbo-Zhoushan Port Main Channel (NZPMC) sea link project with a service life of 100 years. The background of this project is first introduced and the durability design at preliminary study phase is recalled; the chloride-induced corrosion of reinforcement steel was considered as the most critical process that controls the design. Then, the durability model for assessment is established for this durability limit state and the statistical properties of the model parameters are given. From the collected data on the concrete cover thickness and modified chloride diffusion coefficients, the statistical properties of these parameters are updated. With the design options adopted in design phase and the updated parameter properties, taking one non-navigable bridge as an example, the achieved reliability levels and failure probabilities are calculated for structural elements under different exposure conditions by using full probabilistic approach. On the basis of the achieved reliability level of durability, a preliminary maintenance planning is performed for the concrete elements in the concrete structures, and the corresponding recommendations are given.
在深海采矿车布放回收中,准确预报脐带缆在底部自由悬垂边界条件和顶部波浪载荷随机激励等共同影响下的动力响应是关键点之一.基于三维势流理论与集中质量法,结合水面支持船运动和海流联合激励,对深海布放回收中脐带缆的顶端张力等力学特性进行研究.结果表明:在布放回收过程中,轴向张力在结构载荷中占主要成分;由波浪引起的轴向张力极值与均值差距最大可达到54%;轴向张力的频谱存在双谱峰,分别为0.14 Hz的主峰和0.10 Hz的次峰;当浪向角为180°时,轴向张力处于峰谷.
Deep-sea mineral resources are becoming an essential guarantee for humankind’s future socioeconomic sustainable development due to the decrease in terrestrial mineral resources. Collection devices, as vital components of deep-sea mining systems, need to address the efficiency of collection and the environmental disturbances caused by mining activities. The present study investigated the influence of the angle of jets and the radii of a convex wall on the flow field inside the Coandǎ-effect-based collection device to optimize the collection device using a numerical approach. The results indicated: (1) the increase of the angle of jets and radii of a convex wall of the collection device improved flow field uniformity, and the kinetic energy of flow concentrated in the bottom region. The higher mobile speed of the collection device induced a greater Coandǎeffect beneath the convex wall. The internal flow field remained relatively stable when the device was at a speed of 0.5 m/s. (2) the angles of jets and the radii of the convex wall had a significant correlation with the lift and drag force on the nodule. The lift force on the nodule increased when a larger angle of jets or smaller radii of the convex wall occurred in the present study. (3) after analysing the transportation path of nodule particles in stages of separating, lifting, and carrying, it was found that the collection device accurately captured the nodules into the inlet in the scenarios that the collection device had a height of 80 mm above the seafloor and an input jet with an angle of 45°meanwhile the convex wall had a radius of 350 mm with the collection device movement at a speed of 0.5 m/s. This study provides important guidelines for the design and development of deepsea polymetallic nodule collection devices.
吸力式导管架基础具备高承载力、高施工效率、高环境友好度、低造价等特点,使用其作为海上风电底部支撑结构有利于产业的规模化发展,实现上述愿景的前提在于使筒型基础顺利安装以满足设计要求.基于此,在不同初始施加泵压下,对吸力式导管架的沉贯效率特征值、基础内外围渗流变化、筒裙端部土压力特点进行探究.通过抱桩器使吸力式导管架在吸力安装过程中仅具备竖向自由度,从而进行纯沉贯试验.结果表明:初始泵压2 kPa时沉贯效率特征值最高;沉贯过程中基础外围渗流水压小于基础内围渗流水压;筒裙外侧所受土压要大于筒壁内侧所受土压.
深海采矿船是未来人类获取深海矿产资源的重要装备,研究其水动力特性具有重要意义.月池和输运管是影响深海采矿船水动力特性的重要因素.以世界上第一艘超深水采矿船"鹦鹉螺新纪元"号为研究对象,基于三维势流理论,分析月池尺寸、输运管长度及内径对采矿船水运动特性的影响.结果表明:月池开口会使采矿船垂荡、纵荡和纵摇运动出现共振峰,峰值随着开口尺寸的增加而增大,其中垂荡运动峰值可增加将近2倍;输运管的存在会明显改变采矿船横摇运动固有周期,增大垂荡运动峰值,降低横摇运动峰值,对横荡和纵荡运动的影响亦较大,当输运管长度为5 000 m,内径为0.480 5 m时,横荡和纵荡响应峰值能够达到无输运管时的3倍以上.通过探究月池开孔和输运管不同参数对采矿船运动的影响,为深海采矿船月池和输运管设计提供一定的借鉴和参考.
