Risk Assessment Methods in Mining Industry—A Systematic Review

Recently, there has been a growing interest in the mining industry in issues related to risk assessment and management, which is confirmed by a significant number of publications and reports devoted to these problems. However, theoretical and application studies have indicated that risk in mining should be analyzed not only in the human factor aspect, but also in strategic (environmental impact) and operational ones. However, there is a lack of research on systematic literature reviews and surveys of studies that would focus on these identified risk aspects simultaneously. Therefore, the purpose of this article is to develop a literature review in the area of analysis, assessment and risk management in the mining sector, published in the last decade and based on the concept of a human engineering system. Following this, a systematic search was performed with the use of Primo multi-search tool following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The main inclusion criteria were: (a) not older than 10 years, (b) article written in English, (c) publication type (scientific article, book, book chapter), (d) published in chosen electronic collections (Springer, Taylor and Francis, Elsevier, Science Direct, JSTOR). This resulted in the selection of the 94 most relevant papers in the area. First, the general bibliometric analysis was conducted. Later, the selected papers in this review were categorized into four groups and the critical review was developed. One of the main advantages of this study is that the results are obtained from different scientific sources/databases thanks to using a multi-search tool. Moreover, the authors identified the main research gaps in the area of the implementation of risk management in the mining industry.


Introduction
Mining has always constituted one of the most dangerous industries. This is confirmed by data published in Eurostat, OECD (Organisation for Economic Co-operation and Development), or by national organizations, such as, in Poland, the State Mining Authority. The reports presented by these organizations indicate the main risk groups and the effects of their occurrence in mining plants. Prepared reports on accidents in mining indicate their causes and circumstances of occurrence. Thanks to this, it is possible to develop standards relating to actions taken to improve health and safety at work in mining, public safety and environmental protection [1].
Moreover, the importance attributed to the risks associated with mining operations is determined not only by the fact that it is one of the most dangerous sectors of the economy, but also by the scale of mining operations. Figure 1 shows total mining productions by continents in tons.

Introduction
Mining has always constituted one of the most dangerous industries. This is confirmed by data published in Eurostat, OECD (Organisation for Economic Co-operation and Development), or by national organizations, such as, in Poland, the State Mining Authority. The reports presented by these organizations indicate the main risk groups and the effects of their occurrence in mining plants. Prepared reports on accidents in mining indicate their causes and circumstances of occurrence. Thanks to this, it is possible to develop standards relating to actions taken to improve health and safety at work in mining, public safety and environmental protection [1].
Moreover, the importance attributed to the risks associated with mining operations is determined not only by the fact that it is one of the most dangerous sectors of the economy, but also by the scale of mining operations. Figure 1 shows total mining productions by continents in tons. for commodity forecasts and activities in minerals policy at national and European level; it contains production of mineral commodities listed in detail by continents, country groups, development status, per capita income, economic blocks, political stability of producing countries, largest producers and others. The data are available online: https://www.world-mining-data.info/ (accessed 13 July 2020).
Such an intensive mining process, which results in a huge scale of production, generates many risks related to both the operations and resources used, but also to the interaction between the mining system (mines) and the environment. This makes research on risk analysis, assessment and management for this sector particularly important, especially regarding ecological, social and economic aspects. Therefore, the demand for research in this area and new publications, especially for the most productive areas, such as Asia and North America, should continue to grow.
Because mines are a complex human engineering system, they are exposed to multi-faceted risk. Often, the result of this risk occurrence is the loss of life and health of people. It is important to note that these effects may apply not only to employees of mines, but also to the environment-i.e., for example, residents of areas adjacent to the mine. For this reason, the mining sector has been focusing for several years on the need to implement and develop various risk assessment and management concepts. This risk should be analyzed not only in the professional aspect (human factor) but also in strategic (environmental impact) and operational aspects (safety of machines and devices, correctness of the implemented mining process). Research conducted in Polish mining enterprises for several years confirmed that the attention of managers has been focused primarily on the specific risk that for commodity forecasts and activities in minerals policy at national and European level; it contains production of mineral commodities listed in detail by continents, country groups, development status, per capita income, economic blocks, political stability of producing countries, largest producers and others. The data are available online: https://www.world-mining-data.info/ (accessed on 13 July 2020).
Such an intensive mining process, which results in a huge scale of production, generates many risks related to both the operations and resources used, but also to the interaction between the mining system (mines) and the environment. This makes research on risk analysis, assessment and management for this sector particularly important, especially regarding ecological, social and economic aspects. Therefore, the demand for research in this area and new publications, especially for the most productive areas, such as Asia and North America, should continue to grow.
Because mines are a complex human engineering system, they are exposed to multi-faceted risk. Often, the result of this risk occurrence is the loss of life and health of people. It is important to note that these effects may apply not only to employees of mines, but also to the environment-i.e., for example, residents of areas adjacent to the mine. For this reason, the mining sector has been focusing for several years on the need to implement and develop various risk assessment and management concepts. This risk should be analyzed not only in the professional aspect (human factor) but also in strategic (environmental impact) and operational aspects (safety of machines and devices, correctness of the implemented mining process). Research conducted in Polish mining enterprises for several years confirmed that the attention of managers has been focused primarily on the specific risk that comes from within the mining company and is associated with the occurrence of natural and technical hazards, the effects of which are particularly severe for human health and life [2].
The emphasis on implementing the concept of risk management in mine operations is also reflected in the laws, regulations and standards appearing in subsequent years that relate to risk assessment and management. An analysis of the currently applicable standards in this area has allowed us to distinguish 19 documents dedicated to the mining sector. It is worth noting that these standards can also be classified in accordance with the above-mentioned division of the analyzed risk into general and human-, machine-, and environment-focused standards. The division of the analyzed standards and directives is presented in Figure 2. Part of the presented standards are on a global scale, while others are related to the region of the European Union, but the figure also shows documents that are valid only in Poland. A detailed description of the standards is given in Appendix A, Table A1.
Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 40 comes from within the mining company and is associated with the occurrence of natural and technical hazards, the effects of which are particularly severe for human health and life [2]. The emphasis on implementing the concept of risk management in mine operations is also reflected in the laws, regulations and standards appearing in subsequent years that relate to risk assessment and management. An analysis of the currently applicable standards in this area has allowed us to distinguish 19 documents dedicated to the mining sector. It is worth noting that these standards can also be classified in accordance with the above-mentioned division of the analyzed risk into general and human-, machine-, and environment-focused standards. The division of the analyzed standards and directives is presented in Figure 2. Part of the presented standards are on a global scale, while others are related to the region of the European Union, but the figure also shows documents that are valid only in Poland. A detailed description of the standards is given in Appendix A, Table A1. The increasing importance of risk management in mining processes is also indicated by commercial reports prepared for the purpose of managing the mining sector. One such report is the Mining Risk Review, which is published by Willis Towers Watson. This report appeared for the first time in 2014, and since 2016 it has been published periodically every year. Each report deals with a different topic related to risk, but they all focus on emerging challenges for the mining sector and the threats therein. The list of topics covered in the years 2016-2019 is presented in Table 1. The second periodical risk report that deserves attention is the Risk and Opportunities for Mining that has been appearing for two years, published by KPMG International [3,4]. These reports present the results of research on state of mining industry-risks and opportunities, key trends, and managers' expectations for their organizations. The increasing importance of risk management in mining processes is also indicated by commercial reports prepared for the purpose of managing the mining sector. One such report is the Mining Risk Review, which is published by Willis Towers Watson. This report appeared for the first time in 2014, and since 2016 it has been published periodically every year. Each report deals with a different topic related to risk, but they all focus on emerging challenges for the mining sector and the threats therein. The list of topics covered in the years 2016-2019 is presented in Table 1. The second periodical risk report that deserves attention is the Risk and Opportunities for Mining that has been appearing for two years, published by KPMG International [3,4]. These reports present the results of research on state of mining industry-risks and opportunities, key trends, and managers' expectations for their organizations. The growing interest within the mining industry in issues related to risk assessment and management is also reflected in conducted scientific research. Therefore, in recent years, there have been more and more publications devoted to these issues. As a consequence, a large number of articles in a given area results in the appearance of review articles aimed at gathering, structuring and classifying knowledge about published scientific results. Analysis of publications from the last decade regarding literature reviews in the area of risk in the mining sector has allowed us to distinguish 20 articles. As well as standards, these articles can be thematically qualified into four groups: general, human factor, machine, and environment. The largest number of review articles concern research on the environmental impact of the mining sector [9][10][11][12][13][14][15][16]. Comparable attention was paid by researchers to conduct reviews on the risks related to the human factor. For this area, six review papers have appeared in the last decade. Analyses of human factor research have focused primarily on issues related to human health and safety (including accidents) [17][18][19][20] and work organization and team management [21,22]. There is a visible lack of review articles in the area of risks associated with mining machinery. The analyses carried out allowed us to identify only two reviews of literature devoted to machinery, while taking into account the human factor issues [23,24]. The remaining four review articles were classified as general as they did not concern any of the groups distinguished above and were more general in nature [25][26][27][28].
Therefore, the aim of the article is to develop a literature review in the area of analysis, assessment and risk management in the mining sector, including: (1) biometric analysis of publications from the period 2010-2020 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method, and (2) thematic analysis of the scope of analyzed publications, aimed at grouping research according to the adopted classification (human-machine-environment). Following this, the main contributions of this paper include: • a summary of the research developed in the mining sector in the last decade in the area of risk assessment, risk management, risk analysis, and risk decision, • conducting the qualification procedure in accordance with the adopted distribution criteria based on the concept of functioning of human engineering systems in the mining sector, • identification of research gaps in the area of implementation of risk management concepts in the mining sector.
In conclusion, the outline of this review paper is as follows: in Section 2, we explain the method used to select and scan relevant journal articles on the topic of risk in mining industry, which conforms to the PRISMA guidelines. This section also describes the strategy used for literature search process performance and criteria that were applied to assess the relevance of analyzed documents. Section 3 describes the main results of conducted bibliometric analysis. Section 4 is focused on the presentation of results of thematic analysis aimed at grouping research according to the defined classification. Later, in Section 5, the literature research and knowledge gaps are identified. Finally, Section 6 ends with the concluding remarks and recommendations for future studies.

Review Methodology
The presented systematic review was conducted based on the PRISMA guidelines, given in [29]. The chosen method gives the possibility to properly search and select relevant scientific literature on the given topic with defining research objectives and providing clear quantification of scientific developments in a specific field of knowledge [30][31][32][33]. Following this, this section explains the document search and selection process with the definition of eligibility criteria and identification of relevant papers for further investigation.

Literature Search Strategy
The literature searching process was based on the use of multi-search tool Primo (Primo is a scientific search engine which enables the simultaneous searching of many information resources, including databases, magazine and e-book services of various publishers and suppliers, contents of library catalogues, as well as other digital sources; available online: http://biblioteka.pwr.edu.pl/ezasoby/wyszukiwarka-primo (17 June 2020)), which gave the possibility to analyze many information resources, including, among others, ScienceDirect database, Elsevier and Springer publishers' databases, or the JSTOR database. The literature search was conducted between 8 June 2020 and 14 June 2020.
Primo is a scientific search engine that allows for the simultaneous searching of many information resources, which are searched in a quick and easy way, using a single search window, and the search results are displayed on a single platform in the form of a consolidated list of results. One of the basic functions of the PRIMO tool is filtering and narrowing the results. Therefore, during the selection process, the authors used the offered functionality of the chosen multi-search tool. However, the selection criteria were determined based on the authors' experience.
The initial searching procedure was based on the following search term "risk in mining industry". The first step of the searching procedure gave the possibility to identify 208,814 relevant records. In the next step, in order to focus on relatively new applications, problems and technologies, the searches were limited to studies published during the last 10 years. Additionally, only documents written in English were considered. Based on these exclusion criteria, 101,903 records were identified.
Later, the authors focused on filtering studies, taking into account four inclusion criteriathe results were limited to those publications which contained one of the following phrases in the title: risk analysis, risk assessment, risk management, and risk decision. These criteria were established based on expert experience (two authors) and reflect the most relevant aspects of the analyzed research area. As a result, the screening process had the purpose of filtering out papers that were not related with the main topic. Thus, the identified records were scanned by title. Out of the initial 101,903 records, 100,034 were eliminated during the screening process. Moreover, the search was limited only to the following types of documents: journal articles, books, and book chapters. These were selected according to the reason that they would be likely to present a good variety of unique approaches in the analyzed research area. The last selection criterion regarded the type of online databases used. The searching procedure was limited to such online databases as Springer (all available), Taylor and Francis, Elsevier with ScienceDirect, and JSTOR. This choice was dictated by the fact that these are the most important online databases with full access availability for authors. After applying these rejection criteria, the documents were reduced to 742. Moreover, 6 publications were deleted as duplicates.
In result, there were defined 736 papers, which were later fully read in order to identify the most relevant papers.

Selection Process
The obtained documents were subsequently examined by two independent reviewers (A.T. and S.W). The main goal of this step was to verify which of the articles were potentially eligible to be used for a further qualitative and quantitative analysis. The main criterion applied in the full text analysis was its relevance to the investigated thematic area and defined groups. The studies that described risk issues in other industries were excluded. Moreover, studies were excluded from further analysis that examined such problems as product development strategy or general issues potentially applicable in mining industry (but not confirmed).
After a consensus between the authors of this systematic review, 642 papers were rejected. They were consensually considered as being out of scope after reviewing the full document. Consequently, a total of 94 manuscripts were included for a further qualitative and quantitative analysis.

Results
At this stage, a detailed bibliometric analysis was carried out for the selected articles from four thematic groups for risk in mining industry from the last decade.
Ninety-four articles from four analyzed areas were adopted for detailed analysis. Most publications were found for the keywords "risk assessment", which together accounted for almost 80% of all the analyzed texts. The number of publications for each of the analyzed search terms was: • Two publications in the area of risk decisions, • Five publications in the area of risk analysis,

Results
At this stage, a detailed bibliometric analysis was carried out for the selected articles from four thematic groups for risk in mining industry from the last decade.
Ninety-four articles from four analyzed areas were adopted for detailed analysis. Most publications were found for the keywords "risk assessment", which together accounted for almost 80% of all the analyzed texts. The number of publications for each of the analyzed search terms was: The analysis of the authors' and scientific centers' origins allows us to state that most of the publications from the studied area come from China (32 articles), Australia (10 articles), the USA and Canada (7 articles each). The regions of origin of the authors of the analyzed publications are shown in Figure 4. The analysis of the authors' and scientific centers' origins allows us to state that most of the publications from the studied area come from China (32 articles), Australia (10 articles), the USA and Canada (7 articles each). The regions of origin of the authors of the analyzed publications are shown in Figure 4. The analyzed publications were limited in step 2 of the adopted methodology to those published during the last decade. The adopted limitation seems to be correct, as the verification of the years in which subsequent articles were published indicates a clearly growing trend from 2015. As shown in Figure 5, for the last five years, the annual number of publications has been above 10, while in previous years it did not exceed six articles per year. This suggests that the topic risk assessment and management in the mining sector is far from being exhausted, and its popularity among researchers is still rising. It is safe to say that further developments and unique studies regarding this field of knowledge will keep appearing in the near future. The analyzed publications were limited in step 2 of the adopted methodology to those published during the last decade. The adopted limitation seems to be correct, as the verification of the years in which subsequent articles were published indicates a clearly growing trend from 2015. As shown in Figure 5, for the last five years, the annual number of publications has been above 10, while in previous years it did not exceed six articles per year. This suggests that the topic risk assessment and management in the mining sector is far from being exhausted, and its popularity among researchers is still rising. It is safe to say that further developments and unique studies regarding this field of knowledge will keep appearing in the near future.
Articles concerning risks in the mining sector have appeared in many studies. The 94 publications under analysis have been published in a total of 45 journals, of which more than 70% include one article each. A detailed list of journals in which the analyzed research results were published is shown in Figure 6. The figure shows that only those scientific journals for which at least two articles from the analyzed 94 were identified. The largest number of publications appeared in the journal Human and Ecological Risk Assessment (12 articles). Numerous publications can also be found in Environmental Geochemistry and Health and Environmental Monitoring and Assessment (nine articles in each journal). Such a large number of publications in these top three journals is mainly due to the fact that research on risk in the mining sector refers to its environmental impact. This is confirmed by the analysis of the review articles presented in Section 1, as well as by the list of thematic areas presented in Section 4. It should be noted, however, that the topic of risk in the mining sector is of interest not only to journals devoted to the mining sector or environmental issues. Some publications also appeared in safety journals (Journal of Safety Research, Safety Science, Food Security, Journal of Loss Prevention in the Process Industries), as well as those related to management and production research (Production Planning and Control, Journal of Cleaner Production). The detailed analysis that also contains the presentation of investigated papers according to the place of their publication is given in Appendix B, Table A2. The analyzed publications were limited in step 2 of the adopted methodology to those published during the last decade. The adopted limitation seems to be correct, as the verification of the years in which subsequent articles were published indicates a clearly growing trend from 2015. As shown in Figure 5, for the last five years, the annual number of publications has been above 10, while in previous years it did not exceed six articles per year. This suggests that the topic risk assessment and management in the mining sector is far from being exhausted, and its popularity among researchers is still rising. It is safe to say that further developments and unique studies regarding this field of knowledge will keep appearing in the near future.  Articles concerning risks in the mining sector have appeared in many studies. The 94 publications under analysis have been published in a total of 45 journals, of which more than 70% include one article each. A detailed list of journals in which the analyzed research results were published is shown in Figure 6. The figure shows that only those scientific journals for which at least two articles from the analyzed 94 were identified. The largest number of publications appeared in the journal Human and Ecological Risk Assessment (12 articles). Numerous publications can also be found in Environmental Geochemistry and Health and Environmental Monitoring and Assessment (nine articles in each journal). Such a large number of publications in these top three journals is mainly due to the fact that research on risk in the mining sector refers to its environmental impact. This is confirmed by the analysis of the review articles presented in Section 1, as well as by the list of thematic areas presented in Section 4. It should be noted, however, that the topic of risk in the mining sector is of interest not only to journals devoted to the mining sector or environmental issues. Some publications also appeared in safety journals (Journal of Safety Research, Safety Science, Food Security, Journal of Loss Prevention in the Process Industries), as well as those related to management and production research (Production Planning and Control, Journal of Cleaner Production). The detailed analysis that also contains the presentation of investigated papers according to the place of their publication is given in Appendix B, Table A2. The conducted biometric analysis also concerned the repeatability of the indicated keywords used in the papers (Figure 7). The highest share among repeated keywords has the phrase risk assessment, which was indicated in 34 articles. It is significant that the term heavy metal(s) is placed in the second place. If we combine this result with the number of repetitions of this concept, only in the single number-heavy metal(s)-the concept of this keyword occurred in 26 of 94 articles. This indicates the main area of research, to which the publications on risk in the mining sector are devoted. Since the conducted research is largely focused on the negative impact of the work of mines on the environment, mining/mining activity is in third place regarding the most frequently used keywords. The conducted biometric analysis also concerned the repeatability of the indicated keywords used in the papers (Figure 7). The highest share among repeated keywords has the phrase risk assessment, which was indicated in 34 articles. It is significant that the term heavy metal(s) is placed in the second place. If we combine this result with the number of repetitions of this concept, only in the single number-heavy metal(s)-the concept of this keyword occurred in 26 of 94 articles. This indicates the main area of research, to which the publications on risk in the mining sector are devoted. Since the conducted research is largely focused on the negative impact of the work of mines on the environment, mining/mining activity is in third place regarding the most frequently used keywords.

Thematic Analysis of the Conducted Review
This section provides a detailed analysis of the selected papers. In order to clearly present the main thematic areas that are covered by the identified papers, the mind map was developed ( Figure  8).

Thematic Analysis of the Conducted Review
This section provides a detailed analysis of the selected papers. In order to clearly present the main thematic areas that are covered by the identified papers, the mind map was developed ( Figure 8).

Thematic Analysis of the Conducted Review
This section provides a detailed analysis of the selected papers. In order to clearly present the main thematic areas that are covered by the identified papers, the mind map was developed ( Figure  8).  According to the given Figure 8, the main classification based on the four main defined previously groups: human factor, machines, environment, and general. In each of these groups, there were defined the main problems analyzed in the selected papers. The four indicated basic thematic groups are marked in grey. For these groups, characteristic research areas were distinguished, which are repeated in the analyzed articles. For the group machines and general, one level of conceptual branches was defined. For example, three thematic subgroups were defined, namely maintenance accident/safety, reliability, and methods of risk assessment/analysis, for the thematic group machines. Additionally, for the group human factor, there were defined two main subgroups, and in the area of health and safety, a second level of conceptual branches was defined. For the last thematic group, environment, there were defined up to four conceptual levels. Issues assigned to each of the distinguished conceptual levels were marked with a different shape and different linear connections in order to increase the readiness of the developed map.
Furthermore, it should be noted that several of the investigated articles should have been classified in more than one thematic area due to their complexity. Therefore, they were presented on the mind map in all the areas in which they should be classified due to their thematic scope. In addition, in Appendix B, Table A2, their multidisciplinary character was indicated in the column of thematic areas.
First, the group that encompasses general issues was analyzed. In this group, six main research problems were identified. A few papers were dedicated to risk assessment (RA) and risk management (RM) issues. In the RM area, papers focused on the problems of mining project risk management [34], or procurement and contract management of construction services [35]. The model for the joint implementation of risk assessment and risk management was presented in [36], where two case studies were provided. Another approach for risk management was given in [37], where the authors, based on the ISO 31000:2009 standard, used and proposed a tool for complex system investigations.
Implementation of Monte Carlo (MC) simulations for risk assessment performance was presented in [38,39]. The first paper was focused on the development of stochastic simulation to quantify uncertainty in mineral deposits and allowing better management of the geological risk during mining scheduling. The second one was focused on the comparison of different correlation approaches on risk analysis associated with uncertain parameters of mining ventures in order to uncover which one would yield the most accurate result.
The other research problems in this area regarded risk assessment of agricultural soil contamination [40], safety violations in underground bituminous mines [41], and assessment of the risk of roof falls [42].
Safety issues in the mining sector were under consideration in six papers. The problems investigated in this area regarded multi-method or multi-criteria analyses approach implementation (e.g., [43,44]) or decision-making modelling use (e.g., [45][46][47]). In work [43], safety leadership analysis was performed, adopting a multi-method approach, in which the critical decision method, Rasmussen's risk management framework and the Accimap method were applied. The fuzzy-VIKOR-based approach for safety and risk assessment in the mining industry was presented in [44]. The decisionbased modelling approaches were related to issues such as safety measure system development in underground coal mines [45], information uncertainty [46], or the evaluation of safety of coal mining above a confined aquifer [47].
Decision-making problems were also analyzed in works [48,49]. The authors in [48] introduced a method using a multi-goal fuzzy cognitive map (FCM) and multi-criteria decision making based on sensitivity analysis to assess the risks associated with working accidents in underground collieries. The second work [49] was focused on the characteristics of concepts and methods for evaluating sequential information gathering schemes in spatial decision situations.
Moreover, in the analyzed thematic group, the problem of geological uncertainty was identified. In work [50], the authors proposed a new systematic framework to quantify the risk of kriging-based mining projects due to the geological uncertainties. The second interesting view of this problem was given in [51], where the authors provided guidelines for designing and organizing a geotechnical risk assessment process to satisfy the underground mining needs.
The second analyzed group is focused on the environmental issues and is the most represented. The relationships between the environment and the mines are bilateral. On the one hand, the mine, while carrying out its mining activities, directly influences the environment and generates certain negative effects on the environment in the form of, e.g., pollution of the air, water, and soil, health problems, and mining damages. The identified papers in this area were focused on two main issues: building damages and ecological problems, and were assigned to the group impact of mines on environment. On the other hand, however, the environment may also have a negative impact on the activities of the mine through natural processes that interfere with its proper operational performance, such as earthquakes or flooding with groundwater. The articles related to the risk assessment for this area were classified in the second group-environmental impact on mines.
Building damages were under the investigation of the authors of work [52]. They presented an approach to building damage risk assessment in mining induced areas, which is based on a comparison between buildings strength and terrain deformation. In another work [53], the authors proposed an integrated system comprising deep mining, coal-gangue dressing, and underground backfill mining. They also developed many numerical models for buildings aimed at studying the surface subsidence and deformation.
In the environmental thematic group can be defined the second approach, where the environmental impact on mining operation performance was investigated. In this area, research works were focused on seismic risk assessment (e.g., [109,110]) and water risk assessment (water inrush problems [111][112][113], water resources in mining [114], and surface water contamination [115]).
Another thematic group regards human factor issues. In this group, two main research areas were identified, namely social risk and health and safety.
In work [2], the problem of environmental and social risk management during the process of colliery liquidation was considered. The proposed conception is based on including the sustainable development and corporate social responsibility in the total system of risk management in a mining enterprise. In the second work [116], the authors introduced an approach for addressing social risk in mine feasibility studies.
Health and safety issues were analyzed by researchers in three aspects. The problems of health consequences of residents regarded disease risk assessment problems [117], radiation risk [118], and odor and dust influence on community [55]. Moreover, there was one reported work devoted to workplace accidents [119], and one work for system management [120].
The last thematic group was focused on machines. In this area, three main problems were investigated. The first regarded risk assessment method implementation in the mining industry for their machines and the proper operation of processes. For example, in work [121], the authors recognized risks in terms of operation, safety, geology, environment, finance, maintenance, repair, reliability, offer, and availability, and used preventative and mitigated controls to eliminate/reduce risks. In [122], this problem was analyzed with the use of a fuzzy logic-based safety evaluation method. However, in work [123], the authors proposed a method for risk assessment of mining machines, taking into account reliability and maintenance constraints. The issue on reliability was also analyzed in work [124]. The authors developed a methodology for risk assessment in order to support maintenance management based on criticality analysis, root cause analysis, and a tool for generation of effective and efficient solutions (TRIZ) implementation. Moreover, the maintenance problems were also investigated in [125], where the authors discussed the hazards connected to maintenance and operability of the equipment with the customer and identify safety improvements. The OHS/safety information management in the Australian coal industry was investigated in [126].
The articles classified in accordance with the distinguished four thematic groups were analyzed in relation to the countries in which the publications from a given area had appeared. The obtained results of the conducted analysis are presented in Figure 9.
Appl. Sci. 2020, 10, x FOR PEER REVIEW 13 of 40 The articles classified in accordance with the distinguished four thematic groups were analyzed in relation to the countries in which the publications from a given area had appeared. The obtained results of the conducted analysis are presented in Figure 9. The analysis of the results presented in Figure 9 shows that in many countries, research is most often conducted in the areas of environment and general issues. These topics dominate in Australia, parts of Asia (mainly China and India) and Brazil. In North America (USA and Canada), publications from the area of machines are additionally included in this group. In Chile, on the other hand, there are only general publications on the risks associated with machines. It is also worth noting that the topics in individual articles from Africa are mainly related to the environment thematic group.

Identification of the Main Research and Knowledge Gaps
Based on the conducted literature review, the main research and knowledge gaps in the area of risk management in mining sector can be defined.
Mining operators are complex human engineering systems, where the source of the risks involved may be man, machine or the system environment. Therefore, for the needs of the analysis, three research areas have been identified, which indicate the element of the mining system to which the risk analysis relates (machines, human factor, environment) and an additional general group (general). The largest share in the assessed material was held by research devoted to risk assessment in the area of environment. It should be noted, however, that the research described concerned both the impact of mining systems on the environment and the impact of the environment on mine operations.
The analysis shows that this research area can be considered as a knowledge gap for the area of risk assessment and management in the mining sector. This is the result of the bilateral relationship described in the Section 4, which links these two subsystems (environment and mining company). So many publications in this area are also the result of current trends in sustainable development concept implementation. The mining industry is a significant contributor to the environment and its immediate surroundings. Therefore, there is an understandable need for research results from this area. The literature review also suggests that this issue has not yet been fully explored and described. Therefore, it can be expected that the risk aspects of mine operations and their mutual relations with the environment will be further developed.
The lowest share was found in publications on the risks associated with the operation of mining machinery. In addition, only three research areas can be distinguished in this group, which relate to The analysis of the results presented in Figure 9 shows that in many countries, research is most often conducted in the areas of environment and general issues. These topics dominate in Australia, parts of Asia (mainly China and India) and Brazil. In North America (USA and Canada), publications from the area of machines are additionally included in this group. In Chile, on the other hand, there are only general publications on the risks associated with machines. It is also worth noting that the topics in individual articles from Africa are mainly related to the environment thematic group.

Identification of the Main Research and Knowledge Gaps
Based on the conducted literature review, the main research and knowledge gaps in the area of risk management in mining sector can be defined.
Mining operators are complex human engineering systems, where the source of the risks involved may be man, machine or the system environment. Therefore, for the needs of the analysis, three research areas have been identified, which indicate the element of the mining system to which the risk analysis relates (machines, human factor, environment) and an additional general group (general). The largest share in the assessed material was held by research devoted to risk assessment in the area of environment. It should be noted, however, that the research described concerned both the impact of mining systems on the environment and the impact of the environment on mine operations.
The analysis shows that this research area can be considered as a knowledge gap for the area of risk assessment and management in the mining sector. This is the result of the bilateral relationship described in the Section 4, which links these two subsystems (environment and mining company). So many publications in this area are also the result of current trends in sustainable development concept implementation. The mining industry is a significant contributor to the environment and its immediate surroundings. Therefore, there is an understandable need for research results from this area. The literature review also suggests that this issue has not yet been fully explored and described. Therefore, it can be expected that the risk aspects of mine operations and their mutual relations with the environment will be further developed.
The lowest share was found in publications on the risks associated with the operation of mining machinery. In addition, only three research areas can be distinguished in this group, which relate to the same method of analysis/risk assessment and to issues of maintenance safety and reliability. It should be noted, however, that the last two groups have a total of three articles. Following this, it can therefore be concluded that this is an important research gap identified for the risk area under consideration. This is also confirmed by the mind map that has been prepared, which is shown in Figure 8. However, in the available literature, one may find many publications focused on risk-based maintenance, reliability-based maintenance, failure-based maintenance, or safety engineering issues. Indeed, a broad analysis of resources during selection process performance based on the use of other keywords (e.g., risk-based maintenance, reliability-based maintenance, failure-based maintenance) allowed the authors to find publications on this subject for the mining sector as well. For the taken assumption in the selection process, the additional searching procedure gave the possibility to identify additional 39 papers that address the risk issues in maintenance safety and reliability. Moreover, the evolving concept of Industry 4.0 may lead to the focus of risk analysis and risk management researchers in the forthcoming period on issues related to risks arising from the operation of machinery.
Based on the research gap identified above, there can be identified further research work that can significantly affect the development of this area of science. Mining machines, their reliability and operational safety are the main risk factor occurring in mining processes. Their priority importance can be demonstrated by the fact that most of the standards and directives identified for the mining industry refer precisely to machinery (see Figure 2). This hypothesis is also confirmed by research conducted in analogous human engineering systems, such as production systems. The importance of analyzing the risks associated with machines operation can also be demonstrated by the intensive development of research in the area of risk-based maintenance. The main goal of this concept is to reduce the overall risk that may result as the consequence of unexpected failures of operating facilities [127]. Research on the implementation of this strategy in the field of mining machines maintenance is an interesting area for continuing further research analysis.
The last important research area which the authors would like to mention is financial and economic risk assessment issues.
Although financial and economic risk assessment is a broad research area for many sectors, the authors have not identified any literature related to these issues in the investigated databases during the selection procedure performance. The adopted assumptions (e.g., defined time period restriction, keywords used) have not allowed for finding any relevant publication focused on risk analysis, assessment or management in the mining sector, taking into account financial or economic requirements. The additional analysis of resources during selection process performance based on the use of other keywords (e.g., financial risk, currency risk, economic) gives the authors the possibility to find publications on this subject for the mining sector. However, the vast majority of the publications found in this area relate to the period 1990-2010, and therefore fall outside the assumed time frame of the analysis adopted in the carried out review.
The analysis of the publications also indicates changing trends in the area of risk research conducted in the mining sector. The turn of the 21st century was a period when research on financial and economic risks was in the interest of researchers and practitioners. The last decade has focused researchers' attention primarily on environmental issues. Simultaneously, in the future, the main direction of research development will be the issues related to the operation and maintenance of mines' infrastructure and machinery.

Conclusions
The prepared systematic literature review was aimed at providing a general overview of related research to risk in mining sector. After a search process that yielded 736 results, 94 papers were selected. These papers were strictly related to the area of analysis, assessment and risk management in mining. They were published in 45 journals, most of which were thematically related to environmental and human health protection. Most of the selected studies were published in the last 5 years, which proves that this research direction is only in its growth phase and should develop in the coming years.
Furthermore, the presented literature review can be a valuable resource for understanding the latest developments in risk management and assessment in the mining sector. Thus, it will be useful to many people including managers, engineers, and researchers, who are interested in risk management/engineering issues. The authors believe that the conducted literature review will introduce the readers to the major up-to-date theory and practice in risk management/assessment problems in the chosen industry sector. The presented study allowed us to identify the thematic structure related to risk assessment/management for the mining sector. In addition, it showed which topics from the studied scientific area dominate in a given country. At the same time, the conducted analysis gave an opportunity to develop future research directions in the areas identified as research and knowledge gaps.
Moreover, when analyzing the risk management/assessment issues in the mining sector, one cannot forget about the possible different risk factors and aspects occurring at various stages of the mining life cycle (MLC). MLC comprises six phases: exploration and feasibility, design and planning, construction and installation, exploitation and mineral processing, mine closure, and post-mining land use. The selected papers on risk management and assessment in mining industry mostly referred to the three last stages of MLC. However, the current literature study (selected 94 papers) did not allow us to perform a full analysis of the significance of risks and their types in the different phases of the MLC. At the same time, preliminary research done by the authors confirms the significance of this issue. Therefore, the authors consider the performance of a review of studies on risk management/assessment in mining life cycle to be the basic direction of their future research studies.

Conflicts of Interest:
The authors declare no conflict of interest.

PN-EN ISO 14001
Environmental management systems-Requirements and guidelines for use Defines the requirements for an environmental management system that an organization can use to improve the environmental effects of its operations.