Even though geological history, stratigraphic sequences and lithological features of marine sediments have been being studied for several decades (Rokos and Lyusternik 1992), the offshore soils required further in-depth research. Continental shelf is a submerged prolongation of the continent, featuring flattened underwater relief and geology complimentary to the adjacent firm land. Relatively shallow seas form above. For example, the average depth of Russian Arctic shelf seas is rarely more than 150 meters (Rokos and Lyusternik 1992; Kozlov 2012). The shelf areas only form by passive continental margins, where excessive tectonic deformations do not occur, where thick sedimentary cover can build up evenly during millions of years burying the oil and gas deposits. As studies from the Eastern Arctic area prove, the sedimentary cover has formed undisturbedly since the last stage of Caledonian orogeny circa 450 Ma, this being the average age of folded basement (Vinogradov et al. 2004). The sedimentary cover itself consists mainly of terrigenic sediments, altogether reaching the thickness of 17 km (Kozlov 2006). The desired fossil fuels are mainly found within the pore layers of those down to depths of 3 km.
The bottom offshore the Eastern Arctic is a spatial diversity of upheavals and thoroughs; the latter provide the deepest sea marking the greatest thickness of sedimentary layers. This in many cases is a key factor for forming fossil fuels deposits. One of the striking examples is the Eastern Barents sea depression, which contains the large oil and gas bearing Barentsevomorskaya province covering area of 60,000 km2, and the Ludlovskoye gas condensate deposit (Kozlov 2010). However, gas has a tendency to escape from deeper major deposits (due to lower density or to the unconformities in covering sediments) and accumulate in upper layers of soil under clay lenses. When covering clay is disturbed during a rig construction, gas bursts out with considerable force comparable to an explosion, what can cause destruction of construction parts and mounting vessels (Kozlov 2010).
Most of the soils on the Arctic shelf are composed of mixed sand and clay particles. The upper layer of sea bottom sediments cannot be considered as a significant construction base due to its high transfer liability, low pressure resistance or unsolid bedding. The underlying layer of ground that is older in age (up to 2 Ma), is often used as an appropriate base for drilling rigs. However, another challenge is often caused by the presence of ice. The permafrost constitutes the major part of the area both on land and offshore as the result of paleoclimatic events such as the sequence of quaternary Ice ages (Rokos and Lyusternik 1992). This extremely stiff solid formation of water frozen in the pores of a soil gets exposed in large areas at the sea bottom. In addition, the upper layer of marine soil may contain local lenses of recently formed clear ice (Kozlov 2012). Both ice types pose significant challenges to construction. Permafrost is extremely hard to drill through, what makes building of the drilling rigs significantly difficult.
All the before mentioned conditions have direct implications on projecting oil rigs or pipelines within the Arctic shelf seas. To ensure the durability, safety of usage and stability of future structures as well as to prevent accidents, decent strength and deformation properties of the bottom soil have to fit the previously calculated ones of that structure. At this stage of geotechnical research, the environmental conditions of the region play a vital role. For example, even though standard methods can be used for moisture, consistency and porosity characterization, and for defining the grain size composition, the ocean water saltiness has to be taken into consideration. The salt component makes soil grains stick together into larger particles, highly prone to unpredictable crumbling under a structure pressure.