Impact of ground surface subsidence due to underground mining on surface infrastructure: the case of the Anomaly No. 12 Sechahun, Iran

Ground surface subsidence as the result of the application of caving methods (block caving, sublevel caving and longwall mining) may leave significant impact on surface infrastructures which are located in subsidence influence zone. The Anomaly No. 12 Sechahun located in 32 km from Bafq in Yazd province, Iran was planned to be extracted by sublevel caving method. Evaluating the amount of surface subsidence in this mine was very important because different surface infrastructures (railway, road, natural gas transmission pipeline and water pipeline) and an open pit mine (Anomaly No. 10) are located within the mining area. The main purpose of this research was to evaluate the effect of surface subsidence due to underground iron mine Anomaly No. 12 Sechahun on surface infrastructures through numerical and empirical methods. For this purpose, first, the subsidence parameters such as caving angle, subsidence angle and the influence zone were estimated by empirical methods. Then numerical modeling was applied. To estimate rock mass properties, joint mapping was taken from the site at Anomaly No. 10 and a set of numerical models were employed through a Discrete Fracture Network in 3DEC software to determine representative elemental volume. The FLAC3D software was used to simulate the ground surface subsidence due to sublevel caving method. Then, the longitudinal and transverse profiles of subsidence and the influence zone were studied. The results show that surface infrastructures which are located in subsidence influence zone should be moved to 2–3 km from the orebody deposit center. However, the results of this study still must be validated by engineering monitoring data.