Aiming at the structure of goaf roof supported by a large number of irregular pillars, Voronoi diagram can calculate the order of pillars failure fast and easily, but the influence of pillar height, the pillar adhesion, different thickness of overlying strata on the strength of ore pillar have not been considered. In this paper, the stability of pillar is analyzed by using fuzzy set theory and improved the Voronoi algorithm. Taking Xianglushan tungsten mine as an example, stability of the mined out area is calculated. The simulation results show the accuracy and rationality of this method, that can achieve the goal of optimal design and ensure the maximum in mining mineral resources on the premise of safety.
The exploitation of mineral resources will leave plenty of goaf. As time elapse, the mined-out areas subject to the overall collapse due to the weathering and rheological factors (Wang et al. 2011, Wang et al. 201 0). There are many large scale goaf collapse reports at domestic and abroad (Caquot & Kerisel 1948). Because of the complicity of geological condition, and improper design and management, lot of the pillars with irregular shape and distribution remained in mined out area in China. For example, Guangxi HepuHengdagypsum mine, Gansu Changba Lead-zinc Mine, Tangling Shizishan copper mine, Henan Luanchuan molybdenum deposit, Yunnan Lanping lead-zinc mine (Ma & Xie 2013), etc. The mined-out areas deteriorate mining conditions, bring the serious effect on mine production and safety.
There are many scholars have studied the largescale mining dynamic disaster caused by pillar instability. Ma Hai-tao (Ma 2007) established stope numerical model by means of the finite difference method to research stress and strain of mined-out area. Zipf R.K. Jr. (Zipf 1996) used boundary element method to simulate continuous collapse. In addition, in order to analyze large-scale goaf collapse, Ma Hai-tao (Ma & Xie 2013) also proposed a simplified Voronoi area average method to analyze pillar stress.