Underwater crossings of main pipelines belong to the most critical areas of the pipelines. Their performability must be considered from the perspective of the requirements of the provision and management of security, because damage with the loss of integrity may lead to serious environmental consequences.
Currently Transneft PJSC operates about 1400 of underwater crossings constructed by one of three methods: trench method, directional drilling, microtunnelling. In the construction of underwater crossing by trench method, special attention must be paid to the mutual influence of channel processes of water and an object underwater crossing in order to prevent deviations from the horizontal and vertical position. Critical deviations occur within weakly stable channels of water of object with intense bed processes, in which erosion of the floodplain and banks of hundreds of meters, and the erosion of the bottom – up to several meters per year. Method of the directional drilling has several advantages over the trench method of construction: shorter construction times, a weak influence of natural and anthropogenic impacts on the underwater passage, in cramped conditions, regardless of the time of year, comparable in some cases the cost of construction and installation works. Microtunnelling method should be used in difficult engineering-geological conditions. For example, the reliability of the underwater crossing with seismic activity up to 7 points on MSK-64 is provided by structural strength microtunnelling passage.
The article covers technical and economic aspects of construction of the pipeline route. Constraints are formulated methods of construction of underwater passages of main pipelines. Technological scheme for selecting a method of construction of main pipelines underwater passages is developed.
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