Risk Factors for Construction and Exploitation of the Industrial Facilities on the Arctic Shelves: Actual Challenges and Perspective Approaches for Adequate Decisions

Abstract

The bottom sedimental cover on Arctic shelves includes a layer of subaqual permafrost. There are two types of soil grounds within this layer: the conventional 4-phase frozen soils MWIG ("mineral matrix-water-ice-gas"), and the binary type SSGH ("Frozen Soil Saturated by Methane Gas-Hydrates"), which present in fact a mix of MWIG and significant portion of the alternative clathrate subsystem, presented by hydrocarbon gases in icy nano-scaled cells. The SSGH type locates within the gas-hydrate stability zone (HSZ), its upper limit is not constant in a time and may change a depth from 0 meters at the cold glacial epochs up to some hundred meters deeper a surface of sea bottom during the warm interglacial periods. Into the Holocene warm stadia the HSZ depth on the Arctic shelves vary of 50 to 200 meters, but some relics of SSGH soils occur in metastable conditions over the upper limit. Moreover, the lenses of SSGH may to appear near surface in a result of transformation MWIG soil in a stress field under huge gravitational platforms installed on shallow shelf. Geomechanical features of SSGH drastically differ of MWIG, and so for industrial safety it is necessary to provide an advanced and permanent geophysical control of the SSGH abundance and stability under a basement of engineering facilities. The most attractive and reliable approach to those goals is installation around the large industrial objects a fiber optic sensing network, consisting of seismoacoustic and electromagnetic recorders integrated in the single "phase antenna" with digital "big data" processing.