Keyword: «underwater crossing»

The article considers the instrumental survey methods and their peculiarities for underwater pipeline crossings (UPC) located in a sharply continental climate. The following instrumental survey methods are described: profile sounding using the OKO-2 GPR, examination of the Lena River bottom in the area of the underwater crossing of the main gas pipeline (MGP) using Hydra 500E side-scan sonar, determination of the actual planned-high-altitude position of the floodplain part of the underwater gas pipeline employing the RD-8000 line locator. It is shown that there is a practical set of equipment that makes it possible to perform planned and real-time monitoring of the state of the UPC almost all year round, despite the unfavorable climatic conditions and the extension of some UPCs in Central Yakutia.

The movement of running sand massifs is one of the crucial hydrological processes along the Lena River. It significantly affects the nature of the ice drift and spring floods. In this regard, the morphology of the Lena river bed in the Tabaga-Kangalassy section is very dynamic since the riverbed type here is weakly stable or unstable. It is composed of sandy soils and therefore subjected to severe deformation. Consequently, the processing and systematization of long-term data of hydrological observations by the Federal State Institution YaUGMS (Yakut Weather Control and Environmental Monitoring Service) can be used to assess the deformation of the river Lena bottom in the bridge crossing site and the section of two lines of the Hatassy-Pavlovsk underwater crossing of MGP.

Underwater crossings of main pipelines are of great importance in the transport system of the country. Most underwater crossings are laid in an open-cut way by underwater trenching. Scours and sagging of the pipeline in the trench are common phenomena during operation. They lead to stress in the pipe wall. Its level increases with an increase in the length of the scoured section. Hence, protecting the underground crossing of the main pipeline from the impact of negative channel processes during their operation is crucial. The article shows that a comprehensive instrumental examination of the state of the underground crossing allows the detection of siphon denudation and the height of pipeline sagging. It has been established that the scours and denudations of the siphon are permanent.