# A Case Study of Floating Offshore Super-Long Steel Pipeline Combing with Field Monitoring
## 1 Introduction  
The construction of the trans-sea pipeline is an important part of the municipal pipeline project. Due to the complexity of the sea environment, the construction of the pipeline floating on the sea is difficult. The existing floating transportation method is mostly a single pipeline segment floating by segment, while the overall floating transportation technology of super-long pipeline is to float the whole pipeline to the sinking position after individual pipelines make up the whole. [PERSON] et al. [1] studied the mechanical properties of the whole sinking process of super long asymmetric pipe. Compared with the pipelaying vessel method [2] and pipeline jacking method [3], this construction method has less navigation influence, shorter construction period, less influence from geological conditions and low construction cost, it can complete the laying of underwater long-distance water conveyance pipeline with high efficiency and high quality. However, floating transportation on the sea is greatly affected by wind, wave and flow, so real-time monitoring feedback and dynamic adjustment are the keys to ensuring the safety of floating transportation of steel pipelines. The Marine environment is complex. There are three main methods to study ocean engineering: theoretical research [4; 5; 6], numerical simulation [7; 8; 9], indoor modal and on-site test [10; 11; 12; 13]. Compared with other methods, field monitoring can obtain the rawdata of Marine structures and track the effective information in real-time, which provides essential support for offshore installations and reduce the risk of accidents [14; 15]. At present, the monitoring methods of offshore pipelines mainly include fiber Bragg grating, acoustic emission and wireless sensor testing. [PERSON] et al. [16] used optical fiber to monitor submarine pipelines as early as 2004. [PERSON] et al. [17] apply Distributed Optical Fiber Sensor (DOFS), including strain and temperature sensors, to the health monitoring of the Bohai CB271 oil production platform. The experimental investigations on a method for distributed detection of lateral buckling in subsea pipelines with Brillouin fiber optic sensor were conducted by [PERSON] et al. [18]. [PERSON] et al. [19] developed a new Fiber Bragg Grating (FBG)-based bundle-structure riser stress monitoring sensor which could meet the requirements of riser safety monitoring in offshore oil fields. Fiber Bragg gratings are easy to move and paste, and the installation process has less impact on the pipeline surface. However, it also has some disadvantages, such as chirps and creeps. [PERSON] and [PERSON] [20] proposed monitoring of distributed pipeline systems by acoustic sensor networks. Based on the Underwater Acoustic Sensor Networks, [PERSON] et al. [21] proposed an energy-efficient data transmission scheme called EGRC (Energy-efficiency Grid Routing based on 3D Cubes). [PERSON] and [PERSON] [22] proposed a novel passive acoustic-based system that could locate the leak holes and determine their size remotely. The acoustic sensor is portable and easy to install, but it is sensitive to environmental noise and prone to false positives. The Independent Remote Monitoring System (IRMS) of Mexico deepwater floating is fully independent of the primary Integrated Marine Monitoring Systems (IMMS) system in terms of sensors [23]. An energy-efficient cooperative scheme for wireless sensor network (WSN) nodes used in long-distance water pipeline monitoring systems was proposed by [PERSON] et al. [24]. [PERSON] and [PERSON] [25] developed new structural health monitoring (SHM) techniques, in which, the degree of damage was determined by local monitoring using a robotic crawler with magnetic flux leakage (MFL) sensor. It could monitor damage due to vibration fatigue. Production Systems Unmanned aerial vehicles (UAVs) technology prototypes to monitor pipelines were introduced by [PERSON] and [PERSON] [26].