Submarine pipeline stability under the influence of currents and waves

Abstract

When designing and constructing submarine pipelines, special measures must be envisaged and implemented to ensure reliable, trouble-free operation for an extended period of time. The submarine pipelines lying loose on the bottom are subject to the influence of water flow both in the construction period (with different methods of laying) and in the period of operation. A submarine pipeline stability depends on the water flow force and the amount of negative buoyancy. An underwater pipeline will be stable against floating if its weight with the product is sufficiently higher than the ejective force of the water. The factors affecting pipeline stability must be considered when constructing submarine pipelines. The submarine pipeline must be stable under the influence of various loads tending to cause the pipeline to shift or float with inevitable damage. Damage to submarine pipes caused by anchors, wave pressure, and bottom currents is quite a large percentage. Therefore, reasonable prevention efforts are needed so that leaks do not occur, negatively impacting the environment and economy. To achieve stability, it is common practice to add weight coating to the outside surface of the pipeline. The pipelines are weighted with cast iron or reinforced concrete individual weights and in the form of a continuous concrete coating of the pipe. This complicates the work and creates additional difficulties when laying the pipeline. Solid concreting is associated with significant labour intensity of its application, and also leads to an increase in the rigidity of the pipeline. A literature review has shown that, to date, the exact cause of submarine pipeline surfacing has not been established. Some researchers suggest that wave, seismic and bottom current effects may be the causes, but there is no definite answer. Additional experiments and studies are required to resolve this issue. The article discusses theoretical research results for assessing factors affecting submarine pipeline stability, such as wave, current, and geotechnical soil characteristics around the pipeline. The efficiency of applying modern concrete mattresses to protect submarine pipelines from damage and ensure their resistance to surfacing and shifting while creating additional weight is considered.