Review of Underground Space Utilization and its Relevance in Nepal

Underground space, both open-cut and fully underground method, has been in use throughout the world for mining, storage, waterway, transport, and others from past centuries. But still the clear demarcation of ownership in terms of surface and underground is not clear in most parts of the world. The concept of underground space utilization is an evolving concept. The developed nations have opted for this option to accommodate growing urbanization need. Two modes of space utilization are reviewed for this paper, open excavation and full underground excavation. Also world case scenario is presented and is compared to the situation in Nepal. Social factors and geological factors in the context of Nepal are also addressed that have been crucial in case of some completed projects. Ambiguous underground rights in relation to surface ownership in Nepal is taken in account and example of some cities like Singapore, Tokyo, Helsinki is presented to make it clear how right segregation is possible and is needed for better underground space utilization. Historical evolution of Tunneling in Nepal is discussed along with the future designed and scheduled projects. Despite the geological complexity and lack of experienced manpower in the context of Himalayan geology the importance of underground space is highlighted because emerging researches and technological innovation around the world and also in Nepal have been confirming this concept now and again. As a conclusion for betterment and well managed cities in Nepal underground space would be an undefeated option in the long run.

NUMERICAL SIMULATION MODELLING OF TEMPERATURE DISTRIBUTION IN THE PROCESS OF COAL SELF-HEATING IN THE MINED-OUT SPACES

Researches of thermodynamic processes of oxidation, self-heating and self-ignition of coal are necessary for studying of dependence of terminal parameters on a set of the influencing factors. In practice of coal mining by the underground method cases of coal self-ignition in the mined-out spaces of production units (lavas) are frequent. In this case one of the tasks consists in determination of temperature in arbitrary point of the nubbly-porous medium of the mined-out space. Need of the solution of this difficult task is caused by the probability of emergency situations in places with the explosive concentration of methane. It is possible that for each seam and grade of coal it is necessary to develop, substantiate and accept an individual indicator for assessing the state of fire hazard. It is proposed to systematize and methodically process the results of field measurements and observations on the analyzed and investigated cases of endogenous fires in problem areas of mines in order to create basin databases for subse- quent operational decisions in emergency situations.

Analysis of efficiency of drilling equipment use in mining operations

When developing coal and ore deposits by underground method, it is necessary to carry out a large volume of preparatory mine workings using drilling and blasting operations. Minerals are found in rocks under various conditions and their physical and mechanical properties change in a wide range. Under such conditions, it is necessary to use drilling machines this different to the principle of action and structural features. The article considers geometric parameters of roc cutters, peculiarities of drilling modes, affecting energy intensity and drilling productivity in rocks with different strength coefficient.

On the formation of a waterproofing shell around the underground structure lining in watered ground

To prevent the filtration of groundwater into the used underground structure in operation through its lining, it is proposed to make two waterproofing shells by the underground method around the outer surface of the lining of an underground structure; the upper one is made of the soil mass compacted by cementation with reduced water permeability and the lower one is made of the silicate cement. To make the upper shell, boreholes are drilled from an underground structure through its lining and the cement mortar is alternately injected through them into the watered ground providing its hydraulic fracturing; and to make the lower shell, injection pipes with a diameter of 102-152 mm are installed between the boreholes in the lining flush with its outer surface, the silicate cement mortar is alternately injected into the injection pipes, an incipient crack is created between the outer surface of the lining and the ground under the action of the mortar injection pressure on the ground opposite the injection pipe, an incipient crack is hydraulically extended along the contact of the lining with the ground and filled with the silicate cement mortar until refusal to absorb it. To determine the optimal parameters of the hydraulic separation process, tests were carried out on the laboratory table simulator.

Investigation of the electric drive system of the lifting unit with parallel coordinate correction

In the presented publication, the issues of improving the energy efficiency of the electric drive system, in relation to mine lifting installations, are considered. A block diagram of the electric drive system of a mine lifting installation with parallel coordinate correction is considered, as well as a mathematical description of the presented system. It should be noted that the conducted research will significantly affect the improvement of the level of safety and accident-free operation of the mine lifting plant, which will increase the competitiveness of coal mining by underground method.

Alteration of initial stress state in the north area of the Sokolov deposit in the course of mining

The stress-strain behavior of rocks is one of the major factors which govern the value and nature of strata pressure, while the latter in many ways determines the safety and efficiency of underground mineral mining. The subject of the research is the stress-strain behavior of rock mass in the north of the Sokolov deposit developed by the underground method. The aim of the research is to study the change in the stress-strain behavior in the north area of the Sokolov deposit in the course of mining. The methods of the research involve the analysis of the stress-strain behavior measured instrumentally using the borehole slotter technique and the comparison of the data with the instrumental measurements of acoustic emission by GS-01 device. The analysis yields that mined-out space has influence on the stress-strain behavior of rocks, while the effective loads across the orebody strike beyond the influence zone of the mined-out area remain yet high and approach the initial values.

Professional risk of health disorders of employees of enterprises for the extraction of polymetallic ores by underground method

The hygienic assessment of working conditions of workers engaged in underground mining of ores corresponds to the category of occupational risks ranging from «average» to «very high». Taking into account the risk category and severity of occupational disease, occupational disease index for workers, the level of occupational risk ranges from «small» to «very high».