# Application of Artificial Neural Networks in Assessing Mining Subsidence Risk
###### Abstract  
Subsidence at abandoned mines sometimes causes destruction of local areas and casualties. This paper proposes a mine subsidence risk index and establishes a subsidence risk grade based on two separate analyses of A and B to predict the occurrence of subsidence at an abandoned mine. For the analyses, 227 locations were ultimately selected at 15 abandoned coal mines and 22 abandoned mines of other types (i.e., gold, silver, and metal mines). Analysis A predicts whether subsidence is likely using an artificial neural network. Analysis B assesses a mine subsidence risk index that indicates the extent of risk of subsidence. Results of both analyses are utilized to assign a subsidence risk grade to each ground location investigated. To check the model's reliability, a new dataset of 22 locations was selected from five other abandoned mines; the subsidence risk grade results were compared with those of the actual ground conditions. The resulting correct prediction percentage for 13 subsidence locations of the abandoned mines was 83-86%. To improve reliability of the subsidence risk, much more subsidence data with greater variations in ground conditions is required, and various types of analyses by numerical and empirical approaches, etc. need to be combined.  
m m  
ANN provides tools for optimising operations, equipment selection, and problems involving large amounts of information that humans cannot easily assimilate in the process of decision-making. Hence, the neural network can serve as a tool for determining the relative importance of the factors influencing the stability of underground objects [18].  
Since the 1990s, when a number of ANN-based systems were introduced in the mining industry [19], ANN has significantly improved the current approach towards predicting abandoned mine subsidence risk [20; 21; 22; 23]. In particular, [PERSON] et al. [24] evaluated the performance of predictive Bayesian, functional, and meta-ensemble machine learning models in generating land subsidence susceptibility maps. [PERSON] et al. [25] also constructed a hazard map for possible ground subsidence around abandoned underground coal mines in Korea using an ANN together with a geographic information system (GIS). [PERSON] and [PERSON] [26] used an ANN to predict ground subsidence at a metal mine because ground subsidence is influenced by many factors which are fuzzy and nonlinear, and the ANN has a great function to be able to handle such nonlinear problems, without knowing specific mine conditions.  
Meanwhile, Mine Reclamation Corporation (MIRECO) who is responsible for the safety and management of abandoned mines and implements mine reclamation projects in Korea has made several attempts to reliably predict subsidence by numerical, statistical, probabilistic, and/or model approaches [27; 28; 29; 30; 31] prior to this study. However, the prediction results were not up to par with MIRECO's standards because they were not appropriate for the assessment of many as well as extensive abandoned mines.  
Finally, MIRECO decided to adopt ANN as well to predict subsidence considering the merits of ANN mentioned above. Hence, the main objective of this study is to predict the possibility of subsidence on any ground under which a goaf exists by subsidence risk grade that represents the likelihood of subsidence using ANN. This study can be used as an initial method screening the specific locations that are at highest risk of subsidence and thus require immediate detailed investigation, from an extensive mine area for subsequent detailed analyses by the other approaches.  
Meanwhile, from a civil engineering point of view, mining induced ground subsidence is described by parameters measuring ground deformation i.e., radius of curvature, tilt, and vertical as well as horizontal ground deformation [32; 33]. The subsidence in this study signifies the big downward movement of ground's surface enough for one to be able to easily recognize, and Figure 1 shows several examples of the subsidence.