Orthogonal design and numerical simulation of room and pillar configurations in fractured stopes

Room and pillar sizes are key factors for safe mining and ore recovery in open-stope mining.To investigate the influence of room and pillar configurations on stope stability in highly fractured and weakened areas,an orthogonal design with two factors,three levels and nine runs was proposed,followed by three-dimensional numerical simulation using ANSYS and FLAC3 D.Results show that surface settlement after excavation is concentrically ringed,and increases with the decrease of pillar width and distances to stope gobs.In the meantime,the ore-control fault at the ore-rock boundary and the fractured argillaceous dolomite with intercalated slate at the hanging wall deteriorate the roof settlement.Additionally,stope stability is challenged due to pillar rheological yield and stress concentration,and both are induced by redistribution of stress and plastic zones after mining.Following an objective function and a constraint function,room and pillar configuration with widths of 14 m and 16 m,respectively,is presented as the optimization for improving the ore recovery rate while maintaining a safe working environment.

Nonlinear chaotic characteristic in leaching process and prediction of leaching cycle period

A laboratory leaching experiment with samples of different grades was carried out, and an analytical method of concentration of leaching solution was put forward. For each sample, respectively, by applying phase space reconstruction for time series of monitoring data, the saturated embedding dimension and the correlation dimension were obtained, and the evolution laws between neighboring points in the reconstructed phase space were revealed. With BP neural network, a prediction model of concentration of leaching solution was set up and the maximum error of which was less than 2%. The results show that there exist chaotic characteristics in leaching system, and samples of different grades have different nonlinear dynamic features; the higher the grade of sample, the smaller the correlation dimension; furthermore, the maximum Lyapunov index, energy dissipation and chaotic extent of the leaching system increase with grade of the sample; by phase space reconstruction, the subtle change features of concentration of leaching solution can be magnified and the inherent laws can be fully demonstrated. According to the laws, a prediction model of leaching cycle period has been established to provide a theoretical foundation for solution mining.