Investigations of the height of fractured zones in overburden induced by undersea mining

Water inrush accidents are devastating to underground mining operations and cause damage. In particular, in undersea mining, mining safety is endangered as the mining-induced fractured zone extends upwards towards the vast amount of seawater. This paper describes a case study of the development of a fractured zone induced by undersea mining of a tilted ore body in the Xinli district of the Sanshandao Gold Mine in Shandong Province, China. A theoretical prediction model based on overburden movement during mining is proposed to analyse the developed height of the fractured zone induced by undersea mining of the tilted ore body. The Universal Discrete Element Code (UDEC) software program is adopted to establish a numerical model to investigate the movement and fracturing of the overlying strata during mining of the gold deposit from the - 280-m level to the - 200-m level in the Xinli district. For the study area in the - 200-m level, in which the gold deposit is currently being mined and is the closest to the seafloor, the theoretical (32.7 m) and numerical (36.23 m) results for the height of the fractured zone are in agreement with the field observations (32.1 m) from a panoramic borehole televiewer. These results indicate that the fractured zone in the Xinli mining area has not reached the seafloor and that the mine remains safe.