Heat capacity of dispersed rocks

Protection of automobile roads from negative cryogenic processes is a current issue to which significant attention is devoted in both scientific and engineering communities. In many cases important for practice, the the thermal factor determines the reliability and security of the use of the road in the cryolithic zone. The heat capacity of dispersed rocks is among the most important indicators of the physical properties determining the intensity of thermal processes in the road surfaces and road foundations. The precision of determination of the total heat capacity of the rocks in thawed and frozen state largely determines the precision of the forecast of the thermal regime of roads in the cryolithic zone. A complex assessment of the impact of ice content of the dispersed rocks on the value of total heat capacity was done. 2D and 3D charts which allow to assess the possible range of change in the heat capacity of the dispersed rocks in thawed and frozen state, in both a wide range and in the typical range of values, were produced. Among the main criteria determining the extent of the seasonal freezing and thawing of the soils of the active layer is the Stefan number, a dimensionless criterion. An overall assessment of the impact of ice content on the ground (rock) foundations of the roads and of the air temperature in the warm period of the year on the quantitative values of the Stefan number was done. Charts allowing to determine in both a wide and typical range the changes of values of the Stefan numbers, permitting to assess the possible range of changes of the Stefan number, were made. It was determined, in particular, that for the typical dispersed rocks of the road foundations in the cryolithic zone the range of change in the Stefan numbers is 2.1-6.5.

Parageneses of cryogenic formations of gas emission funnels (Part 1). Morphology of cryogenic formations

The subject of this research is the cryogenic formations found in gas emission funnels in the north of Western Siberia. The object of this research is cryogenic processes that prepare the explosion, which forms a gas emission funnel. The study of cryogenic structures that shape the walls of gas emission funnels is based on the structural-genetic analysis, which reveals the peculiarities of the initial cryogenic structure of frozen rock, as well as the cryogenic textures modified as a result of dynamic metamorphism. The authors examine such aspects of the topic as the general orientation of plastic and explosive deformations under the influence of high pressure. Analysis is conducted on the role of intra-ground gas filtration in transformation of the initial cryogenic structure. Special attention is given to the patterns of emergence and development of the local geodynamic system that ultimately substantiates the formation of gas emission funnel. The novelty of this research consists in the establishment of paragenetic relations between the processes of gas filtration and deformations of gas-saturated ice surface material (from viscoplastic motion to brittle fracture). The main conclusions are as follows: such external influences as increase in the temperature or pressure change thermodynamic conditions, which lead to multi-phase structural transformation of the initial cryogenic structure of the cryolithic zone; a series of plastic and explosive deformations instigates the intense heat and mass transfer, redistributing the substance in the liquid, solid and gaseous state; in frozen rocks, ice is the most deformable component, thus, most information on the processes preceding the formation of gas funnels can be acquired by studying the morphology of cryogenic formations observed in the walls of the funnels, as well as in the unthawed fragments of frozen rocks thrown to the surface. The authors’ special contribution lies in examination of the complete lifecycle of the development of selected geosystems, from the initial stage –  formation of conditions for decomposition of the gas hydrates, to the final stage – explosion and emission of ice surface material.

Modeling the effect of skidded timber bunches on forest soil compaction

An increasing demand for forest products incites a large number of log transportation operations, which may lead to negative consequences for the soil and the ecosystem as a whole. This paper presents a mathematical model to estimate the soil deformation and compaction processes under the influence of individual components of the skidding system, such as the forwarder, limbs, butts, and tops of tree-lengths in high latitudes, permafrost soil, and forests of the cryolithic zone. The effectiveness of the proposed model was evaluated according to experimental results. Comparative analysis showed that the calculated data differ from the experimental data by no more than 10%. The deformation of the soil by the bunch of tree-length logs occurs due to shearing processes. It has been established that the initial vertical stress exceeds the radial stress by 30–40%. The result of estimating the dependency of the shelterbelt width on the number of tree-length logs showed that the limit values for logs amount to 4–6 units for the mild, medium, and solid soil categories. The obtained results and the developed model will allow for a qualitative and quantitative assessment of the technological impact on the soil during the projecting of maps for logging operations.

Influence of the parameters of the layer of ore being brought down on its freezing and losses during the face ore draw

Application of mining systems with ore caving and adjacent strata, which do not entail high expenditures on delivery of freed ore and rock pressure management, allows to considerably increase efficiency of underground mining of ore deposits in the cryolithic zone. However, their use where permafrost formations are prevalent, requires taking into account factors complicating mining operations, in particular, the congealing of broken ore in the stoping zone. In order to assess the impact of thermal and humidity conditions on the completeness of reserves recovery, a study was carried out to determine the dependence between the volume of losses of broken ore prone to congealing and the width and height of the layer being brought down. Experimental studies were conducted by physical simulation in a cryo chamber on a laboratory bench. The ore drawing was conducted in a uniform sequence at the temperature in the stoping zone of minus 5 ˚C. The final parameter to be determined the loss of ore prone to congealing, was defined as the difference between the mass of ore in the block and the mass of ore drawn. It has been established that the losses of the broken ore due to congealing increase significantly when the depth of the layer being freed decreases and the width increases. The established patterns of influence of parameters of a beaten layer on losses of ore mass will be used during development of recommendations on technology of drawing of ore mass prone to congealing in the negative thermal conditions of underground mines of a cryolithic zone.

Geological and engineering conditions of deposits as foundation of their safe development

The article studies geological and engineering conditions of the mineral deposits located in cryolithic zone. The demand to study and analyze geological and engineering conditions is justified by safety requirements established to development of the deposits. The article is focused on pebble-phosphate deposit located in Polar Urals. The geological and engineering conditions of this site fall within very severe category, which is connected with endogenetic and exogenic processes of its accumulation. It is the genesis of the deposit that generated the factors that complicate drilling-in conditions, included but not limited to weathering crusts with significant depths and discontinuity, frozen rock mass and its cavernous porosity.