菱刈鉱山・山神鉱床における採鉱切羽の設計

Abstract

The Hishikari Gold Mine has met a new challenge in choosing a mining method for the Keisen vein group in the Sanjin deposit. The deposit mainly consists of 2 veins. The KE-2 is a composite vein, extending over a width of a 15m, with an average grade of 20 g / t. The KE-3 has a 2 m width and a very high grade of around 100 g / t. They are too closely spaced to be extracted selectively by employing the conventional Hishikari mining method of bench stoping. Consideration was given on alternative mining methods in order to extract these veins efficiently. A modified bench stoping method with a larger width appeared to be economically feasible, but would involve stability difficulties due to increased stoping width. Numerical and empirical analyses were used to determine an appropriate mining sequence and stope dimensions. Numerical analysis was performed using a two-dimensional elastic-plastic finite element code. The results indicated that a conventional mining sequence caused increased stability issues. The "Stability Graph Method", which is a well known empirical approach, led to a new mining sequence and cable bolting patterns, which allowed improved stope stability and efficient mining of Keisen veins. Numerical analysis was also used to establish the dependence of stope stability on the properties of backfill materials.