ICE ACCUMULATION IN ROCK SAFETY CUSHION, CONSIDERING ATMOSPHERIC PRECIPITATION SEEPAGE AND MOIST MINE AIR LEAK IN THE CONDITIONS OF PERMAFROST REGION

For the extraction of mineral reserves of Udachnaya Pipe under the open pit bottom, the system of one-stage caving under a safety cushion is accepted. To ensure the mine safety, the cushion should preserve looseness within the whole mine life period. Developed for the analysis of ice accumulation, the general mathematical model of heat and mass transfer takes into account three interfering processes running in the safety rock cushion, namely, seepage of moisture from atmospheric precipitation, leak of moist air and heat transfer during phase transformations of moisture. It is analyzed how atmospheric precipitations and mine air affect the process of ice accumulation in the safety cushion. The mathematical model allows calculating ice formation in voids of the cushion owing water seepage and condensation of moist mine air. The model efficiency is discussed in terms of the calculations for a rock safety cushion 30 m thick. The calculations are performed for readily and weakly permeable rocks. For the readily permeable rocks, the maximum ice content is 0.1 at a depth of 1.5 m in the first summer and 0.15 at a depth of 2.2 m in the first winter. In the second summer, the maximum ice content is also observed at the depth of 2.2 m; moreover the ice content grows, which blocks pores. In case of the weakly permeable rocks, ice accumulates at a depth of 1.9 m. At the bottom of the cushion, rocks gradually thaw under leakage of air from the mine irrespectively of the season. In addition, ice accumulates in the cushion owing to condensation of moisture from the mine air. The ice content curve contains a characteristic “hump” which drifts toward the upper boundary of the cushion with time. The hump drifting is less intensive in the weakly permeable rocks. The developed mathematical models of heat and mass transfer and the programs for calculating temperature and moisture content of the safety cushion under moisture seepage can be used to predict rate of adfreesing in rocks and to control safe and uniform subsidence of the cushion. The calculation results will help develop guidelines on making safety cushions, maintaining their year-round flowability and permeability, as well as improving safety of underground extraction of diamond pipe reserves.

Keywords

Rock safety cushion, hybrid open pit/underground mining, permafrost region, phase transformations, moisture seepage and air leak, temperature, mathematic modeling.

Issue number: 12
Year: 2018
ISBN:
UDK: 622.272: 536.24
DOI: 10.25018/0236-1493-2018-12-0-39-47
Authors: Neustroev A. P., Khokholov Yu. A.

About authors: Neustroev A.P., Graduate Student, e-mail: wako0493@gmail.com, Khokholov Yu.A., Doctor of Technical Sciences, Leading Researcher, e-mail: khokh2001@mail.ru, Chersky Mining Institute of the North, Siberian Branch, Russian Academy of Sciences, 677018, Yakutsk, Republic of Sakha (Yakutia), Russia.

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