Concerning the Planned-High-Altitude Position of the Underwater Crossing of Hatassy-Pavlovsk MGL Across the River Lena

One of the determining factors for the efficiency of the main gas lines in Yakutia is their interaction with complex geotechnical and operating conditions. The most complex structures are underwater crossings of pipelines across the water bodies. Underwater crossings are among the high-risk systems; they are the most critical. The terms of accident elimination at underwater crossings are much longer than those of similar damage on the linear section of pipeline. Besides, their repair during operation is comparable in complexity and cost to the construction of a new underwater passage. This article provides data on conducting monitoring studies of the state of the Hatassy-Pavlovsk MGL across the channel part of the river Lena, determination of the planned-high-altitude positions of two pipelines on the floodplain sections of the route, on channel processes that affect SSS of welded joints of the pipes and determine the operational reliability and durability of the MGL.The determination of riverbed deformations in the area of the underwater crossing of the main gas line (MGL) is one of the most important issues of the research. Changes in the characteristics of the river flow, safety and service reliability of the underwater crossing of MGL across the river Lena depend on the riverbed deformations. The quicksand disturbance along the course of the river Lena significantly affects the nature of ice drift and spring floods. Due to the erosion of bottom sediments and soil heaving on the coastal slopes of the Hatassky channel, as well as its shallowing, the underwater crossing of the gas pipeline is completely seized by freezing ice and soil of the coastal slopes and is tightly clamped. Studies have revealed the seasonal loosening of the surface pipeline and scour at its underwater part, wearing away of the riverbanks, as well as anthropogenic impact under changing climatic conditions.