Science and technological developments: article

Natural explosive processes in the permafrost area
A. Vlasov1
A. Khimenkov2
D. Volkov-Bogorodskiy1
Y. Levin1
1 Institute of Applied Mechanics of the Russian Academy of Sciences, Moscow, Russia
2 Sergeev Institute of Environmental Geoscience of the Russian Academy of Sciences, Moscow, Russia
Journal: Science and technological developments
Tome: 96
Number: 3
Year: 2017
Pages: 41-56
UDK: 551.345; 544.454
DOI: 10.21455/std2017.3-4
Keywords: permafrost, gas hydrates, blister, explosion, crater, stages, dissociation
Аnnotation: The aim of the paper is the consideration of the group’s natural explosive processes on the area of permafrost, which have not been allocated. The first group described the long and associated with freezing of water in closed environments (explosions of blisters and icing mound). The second was allocated in the last 3 years. It is associated with the release of underground gases formed during dissociation of gas hydrate contained in permafrost. The cause of the explosion in both cases is formation overpressure in the soil mass containing free water or gas. Once pressure exceeds the strength of the roof of permafrost occurs her release. It can identify a number of common features of preparation of the explosive processes in the permafrost. First, there is a local zone where is concentrated substance forming explosion: over-freezing streambed ground water flow, water concentration zone in over-freezing soil mass, gas hydrates in frozen soil. Second, there is the pressure of a compressive the substance. Third, there are deformations in overlying soils. If pressure increases slowly and the roof have time to deform, then there is plastic deformation. In this case mounds are formed. It is expressed in the topography. If the pressure increases quickly then plastic deformation may not occur. Fourth, it is the explosion itself. As many authors described the explosion effect on the objects of various origins has common characteristics. It is a gas-saturated water and gas ejection, also ground and ice debris, which are launched on ten and sometimes on hundred meters. During dissociation of the gas hydrate in frozen ground first micro-cracks are arising. Then they make up ascended subvertical channels and elongate pores growing under sufficiently high pressure. Gas hydrat cropout on the soil surface and gas evaporation is prevented by the durable monolithic overlying ice-soil “cover”. As a result of this impossibility the crack-pore structure of the frozen ground is formed under “cover”. Then the width of crack opening and the pore size are increased with pressure grow by gas filtration from the source. They merge together founded cavity in which continue gas leakage. In the moment of exceeding the ultimate strength limit, the “cover” could not bear stresses and accumulated potential gas energy is released (i.e. transformed to the kinetic one) by the explosion. During Arctic development the hazard of explosion processes for engineering constructions will be increased. Nevertheless this group of risk is not only not considering under designing and prediction, but even not including in the group of danger geological processes.