PSI - Issue 20

S.A. Tikhonova et al. / Procedia Structural Integrity 20 (2019) 230–235

231

2

S.A. Tikhonova et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction Underground trunk pipelines laid in the regions of permafrost distribution should be considered taking into account the interaction of pipeline system and surrounding frozen soil. Their security is the most important indicator of risk criterion, since the violation of its work affects the state of security of the whole region was pointed by Kapitonova et al. (2014). Mutual influence of pipeline and cryolithozone begins with construction of pipeline route, which leads to a sharp increase in dangerous geocryological processes in technological corridor. Deforestation during construction of corridor, disturbance of vegetation during trenching, violation of natural flow of water bodies during construction of line road and pipeline embankment are the main potentially dangerous geotechnical works, during which the inevitable impact on frozen soils occurs as shown by Dziuba (2006) At the stage of operation, thermal interaction of pipeline with frozen soil leads to thawing and liquefaction of the soil. When thawing frozen soils, the structure of soil is disturbed, which causes deterioration of its physical and mechanical properties. Such defrosting is accompanied by development of thermal precipitation under the pipeline, uneven development of which can cause a critical deformation of pipeline and, as a result, an emergency situation. For timely detection of hazardous areas, several times a year, the state of pipeline operating in difficult climatic conditions is assessed. One of such works is geotechnical monitoring (GTM), which allows not only to evaluate, but also to predict the state of pipeline system. At one of GTM stages, the following main tasks are solved with the help of aerial and satellite imagery: identifying areas with a violation of technical condition of the object, for example: ruptures, cracks, corrosive zones, damage to hydro and thermal insulation, etc. monitoring and inspection the state of natural environment throughout the entire length of the main pipeline route (state of hazardous geological processes, flooding zones, corrosive-hazardous environments, freezing and thawing soils, etc.); analysis of sections with underwater crossing of main pipeline; ranking of areas according to the degree of danger, allocation of areas for priority diagnostic research. In this paper, we studied the possibility of assessing of oil and gas pipeline state using satellite information decoding, namely, analyzing changes in parameters of vegetation as an indicator of activation of dangerous geological processes along the main pipeline route. For example, if in the pipeline corridor the state of vegetation changes, soil moisture increases, the number and size of wetland areas grows, then perhaps this is an indicator of geocryological processes activation. The use of remote sensing to monitor changes in land cover over time has a long history. Methods based on interpretation of multi-temporal satellite images using vegetation index to assess the state of environment and anthropogenic influence are described in many works by both Russian and foreign authors, see Adamovich at al. (2017), Alekseeva at al. (2013), Dneprovskaya at al. (2017), Peremitina at al. (2014), Tucker (1979), Adams at al. (1995), Elmore at al. (2000), Verbesselt at al. (2010). There are studies on deterioration of vegetation associated with permafrost degradation carried down by Luo at al. (2018). A comparison of satellite-derived estimates of vegetation cover over time with local climatic and environmental factors can help to better understand the complex mechanisms of interaction of man-made objects and environment. Currently, using remote sensing data, obtain information about the state of ground objects, with possibility of continuous collection of information for each specific territory. The main advantages of Earth remote sensing are high speed of obtaining data on large areas of the earth’s surface, as well as possibility of obtaining information about objects that are practically inaccessible for research in other ways.

Nomenclature GTM geotechnical monitoring; NDVI Normalized Difference Vegetation Index; ENVI software for visualization and processing of remote sensing data.

*