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DOI: 10.25136/2409-7543.2022.4.38938
EDN: DUMHVO
Received:
13-10-2022
Published:
30-12-2022
Abstract:
The thermal regime of underground cryolithozone structures for various purposes, both related and not related to mining production, is an important factor determining their reliable and safe operation. In this regard, the forecast of the thermal regime in mine workings is a mandatory and important element in the justification of design solutions for the construction and reconstruction of underground structures in the areas of distribution of continuous and island permafrost. One of the main sources of heat generation in the workings is the work of diesel equipment, which is widely used, both in the development of mineral deposits by the underground method, and to ensure technological processes in underground structures of non-mining profile. The purpose of the research was to quantitatively assess the effect of diesel installations on the thermal regime in the underground structures of the cryolithozone. The results of numerical calculations are presented in the form of 2D and 3D graphs, which allow you to visually assess the effect of diesel equipment on the increment of air temperature in the underground structure, depending on the time of year and the efficiency of the diesel installation. It is shown, in particular, that in the most probable range of changes in the efficiency of a diesel installation, the air temperature can vary from 3.2 to 6.3 °C, depending on the standard values of the ventilation air flow. It is established that the temperature increment does not depend on the number of simultaneously operating diesel units and is determined only by the specific standard air flow (m3 / s per 1 kW of installation power).
Keywords:
underground structure, thermal regime, diesel installation, temperature, permafrost, calculation, power, efficiency, ventilation, safety
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Introduction. The thermal regime of underground cryolithozone structures for various purposes, both connected (mines, mines) and not connected (warehouses, shelters) with mining production is an important factor determining their reliable and safe operation [1,2,3,4]. Especially the negative influence of the thermal factor affects the operation of underground structures located in dispersed frozen rocks, when ice-saturated rocks (ice soils) or ice inclusions in the rock mass are located in the zone of thermal influence of the workings. Even at a negative air temperature in the workings, ice-saturated dispersed rocks change their strength characteristics, which affects the safety of operation of underground structures in the cryolithozone [5,6,7,8,9]. In this regard, the forecast of the thermal regime in mine workings is a mandatory and important element of the justification of design solutions for the construction and reconstruction of underground structures in the zones of continuous and island permafrost [4,10,11,12]. The formation of the thermal regime of underground structures is influenced by many factors (heat sources), which can be conditionally divided into relative (the power of which depends on the air temperature in the production) and absolute (the power of which does not depend on the air temperature) [1]. In many cases, it is the absolute sources that are the main ones and determine the thermal regime in underground structures [13,14,15,16,17]. One of these sources of heat generation is the operation of diesel equipment, which is widely used both in the development of mineral deposits by underground method and to ensure technological processes in underground structures of non-mining profile. The purpose of these studies was to quantify the effect of diesel installations on the thermal regime in the underground structures of the cryolithozone. Method. If we consider a diesel car as a point absolute source of heat, then the basic calculation formula will have the form [18]:  (1) where  is the increment of the air temperature in the production, 0C; N is the engine power, kW;  – engine efficiency, ie;  – air density, kg /m3; c is the specific heat of the air, kJ/kg 0C; Q is the air flow rate in the production, m3/s. The air consumption in the production during the operation of diesel equipment is determined by the formula: Q = QoN (2) where – Qo is the standard air consumption per kW of engine power (0.113 m3/s at a standard of 5.0 m3/min. at 1 hp or 0.086 m3/s at a standard of 3.5 m3/min. for 1 hp). The general formula for converting the standard air flow rate to [(m3/min)/(hp)] in [(m3/s)/(kW)] has the form Qo (kW) = 0.023+0.018 Q o(hp). (3) Substituting expression (2) into (1), taking into account (3), we get:  (4) Here Qo is the standard air consumption per hp of engine power, m3/min. Results and discussion. The analysis of expression (4) shows that the total power of diesel installations (the number of simultaneously operating machines in the mining) does not affect the increment of air temperature in the development, which is mainly determined by the average efficiency of the diesel engine. Moreover, the temperature increment in summer (with constant efficiency) is naturally greater than in winter (on average, by 10%), because the air density in winter is higher and the moisture content is lower. The graphs (Fig. 1) show the dependences of the temperature increment on the efficiency of the engine at various standard air flow rates. 
Fig. 1. Increment of air temperature during operation of diesel equipment in the production
Notes: 1-in winter (at a standard of 5 m3/min. for 1 hp); 2-in the summer (at a standard of 5 m3/min. for 1 hp); 3-in winter (at a standard of 3.5 m3/min. for 1 hp); 4-in the summer (at a standard of 3.5 m3/min. for 1 hp); 5-in winter (at a standard of 2.8 m3/min. for 1 hp); 6-in the summer (at a standard of 2.8 m3/min. for 1 hp). It follows from the graphs that the maximum temperature increment at the standard flow rate is 5 m3/min. at 1 hp, it can reach 3.2-4.3 0C for the most probable value of the efficiency of a diesel engine (0.4-0.5). When reducing the standard flow rate to 2.8 m3/min. for 1 hp, the temperature increment increases to 4.7- 6.3 0C. Figure 2 shows the graphs of the increment of air temperature in the underground mine (chamber) during the operation of diesel equipment in the range of air flow from 2.0 to 5.0 m3/min. at 1 hp at different engine efficiency values. As can be seen from the graphs, with a decrease in the standard air flow, the air temperature in the production increases. Moreover, the lower the efficiency of the engine, the higher the rate of change. The temperature change does not depend on the number of machines working in the production at the same time. The change in summer is slightly greater than in winter. 
Fig. 2. Increment of air temperature during operation of diesel equipment in the production depending on the value of the standard air flow Notes: 1-in the winter period (with a efficiency of 0.5); 2-in the summer period (with a efficiency of 0.5); 3-in the winter period (with a efficiency of 0.4); 4-in the summer period (with a efficiency of 0.4); 5-in the winter period (with ap.d. 0,3); 6-in the summer period (with a p.d. 0,3). Figure 3 shows a 3D graph of the increment of air temperature in the production (chamber) during the operation of diesel equipment in various ranges of changes in standard air consumption per 1 hp and efficiency of a diesel engine. 
Fig. 3. Increment of air temperature (T, 0 S) during operation of diesel equipment in the production: 1- in winter and 2- in summer The analysis of the graphs in the figure confirms the previously made inputs about the role of diesel technology in the formation of the thermal regime of the chambers of the underground structure. For the conditions under consideration, the increment of air temperature will not exceed 6.5 0 C. Moreover, both in the winter and summer periods of the year, this will improve the climatic conditions in the mine workings. Conclusion. The assessment of the influence of diesel installations on the formation of the thermal regime in the chambers of underground structures at various standard values of air flow was carried out. The results of numerical calculations are presented in the form of 2D and 2D graphs, which allow us to visually assess the influence of diesel technology on the increment of air temperature in an underground structure depending on the time of year and the efficiency of the diesel installation. It is shown, in particular, that in the most probable range of changes in the efficiency of a diesel installation, the air temperature can vary from 3.2 to 6.3 0C, depending on the standard values of the ventilation air flow. These increments are significant and can have a significant impact on the choice of support parameters in an underground structure. It is established that the temperature increment does not depend on the number of simultaneously operating diesel installations and is determined only by the specific standard air consumption (m3/s per 1 kW of installation power). The article is primarily of methodological importance and allows for a concrete example to trace in detail the ways of qualitative and quantitative analysis of the expected impact of diesel installations on the formation of thermal conditions in the chambers of underground structures of the cryolithozone. The article can be useful for both design engineers and practitioners of mining construction, as well as researchers in the field of mining thermophysics and mine aerology. In methodological terms, the article may be of interest to graduate students studying in various specializations of the 2.6.8 direction "Geomechanics, rock destruction, mining aerogasodynamics and mining thermophysics" as well as students studying in mining and construction specialties of this direction. Further research should be aimed at assessing the formation of the thermal regime in the chambers of underground structures with intermittent (periodic) operation of diesel installations and, accordingly, different ventilation modes of the chambers.
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Peer Review
Peer reviewers' evaluations remain confidential and are not disclosed to the public. Only external reviews, authorized for publication by the article's author(s), are made public. Typically, these final reviews are conducted after the manuscript's revision. Adhering to our double-blind review policy, the reviewer's identity is kept confidential.
The list of publisher reviewers can be found here.
The article submitted for review examines the temperature change in the chambers of underground structures during the operation of diesel installations in the context of safety. The research methodology is based on the consideration of a diesel engine as a point absolute source of heat, the application of the method of mathematical modeling of the thermal regime and visualization of the calculation results. The authors attribute the relevance of the work to the negative influence of the thermal factor during the operation of underground structures located in dispersed frozen rocks, when ice-saturated rocks (ice soils) or ice inclusions in the rock mass are located in the zone of thermal influence of workings, they note that even at negative air temperatures in the workings, ice-saturated dispersed rocks change their strength characteristics, which affects on the safety of the operation of underground structures in the cryolithozone. The scientific novelty of the reviewed study, according to the reviewer, consists in the assessment of the influence of diesel installations on the formation of thermal conditions in the chambers of underground structures at various standard values of air consumption. The following semantic sections are structurally highlighted in the text of the article: Introduction, Purpose, Method, Results and discussion, Conclusion and Bibliography. The authors provide calculation formulas for estimating the increment of air temperature in the production, air consumption in the production during the operation of diesel equipment, recalculation (translation) of the standard air consumption from one unit of measurement to another. Based on the calculations carried out, it is concluded that the total power of simultaneously operating machines in the mine does not affect the increment of air temperature in the mine, which is mainly determined by the average value of the efficiency of the diesel engine; it is noted that the temperature increment in summer is on average 10% higher than in winter because the air density is higher in winter and the moisture content is lower. The text is illustrated with three figures, which show the increment of air temperature during the operation of diesel equipment in production, its dependence on the value of the standard air consumption, temperature changes in winter and summer periods of the year. In conclusion, the results of the study are summarized, the possibilities of practical use of the results obtained and the prospects for further developments to assess the formation of a thermal regime in the chambers of underground structures with non-constant (periodic) operation of diesel installations and, accordingly, various modes of ventilation of the chambers are shown. The bibliographic list includes 18 sources – publications of domestic and foreign scientists on the topic of the article for the period from 1968 to 2019. The text contains targeted references to literary sources confirming the existence of an appeal to opponents. The following points should be noted as comments. Firstly, it seems advisable to expand the bibliographic list by means of publications published in recent years. Secondly, to facilitate the perception of the information presented in Figure 2, it is worth increasing it. The reviewed material corresponds to the direction of the journal "Security Issues", has been prepared on an urgent topic, contains theoretical justifications, elements of scientific novelty and practical significance, reflects the results of calculations carried out by the author of the article, which may be of interest to readers. The article is recommended for publication after some revision in accordance with the comments made.
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