A three-index estimator based on active thermometry and a novel monitoring system of scour under submarine pipelines

A submarine pipeline system is a major asset. Scour monitoring under submarine pipelines is a tough problem and lacks research, especially for nearshore and landfill sections. While these sections are critical for the viability of the pipeline system, they are also the most vulnerable to scour. In this study, a three-index estimator (TIE1) based on active thermometry was developed for solving this problem and thereby a novel scour monitoring system was designed for nearshore and landfill sections. Heat dissipates in different ways between in-water and in-sediment scenarios. TIE, consisting of three indices obtained through time history analysis of temperature change during heating and cooling, can well characterize the distinction of heat transfer behaviors between in liquids and solids. By calculating TIE, it is possible to identify whether a location along a pipe is surrounded by water or soil. Considering this, the system utilizes a thermal cable to generate heat with a heating belt and concurrently measure temperature with DS18B20s. The thermal cable was deployed parallel to the pipeline. Analyzing the acquired data by TIE, identification of free spans is achieved. Several experimental tests were conducted using the system. Results confirm the methodology and substantiate the scour monitoring system.