Study On Comprehensive Mining Technologies Of Orebody With Multiple Mined-out Areas In Xishimen Iron Mine

Xishimen iron mine is well-known for its mining difficulty in metallurgical enterprises, and its magnetite deposit is of contact metasomatic skarn type. Affected by illegal mining in the 1990s, multiple mined out areas are left, and most of them have caved. But there are some influencing factors caused by mined out areas, such as imperfection of orebody, rock movement and safety hazard. These factors make mining more difficult. In other words, how to realize the goal of safety and high yield is an important technique problem for Xishimen iron mine. So, research on comprehensive mining technologies of orebody with multiple mined-out areas is performed by site investigation, theoretical analysis, numerical simulation, and field test, the main contents are as following:(1) Sublevel caving method and some improved methods are analyzed. And then several new methods are proposed according to different characteristics of orebody with multiple mined out areas. Inclined drift and flat bottom trench structure is suggested for the orebody destroyed by illegal mining. And, double trenchs, trenchs in series connection, single trench are proposed for different dip angle and thickness; On the basis of orebody thickness and skarn, single trench structure and an improved sublevel caving scheme that loading in trench and ore drawing in drift are proposed for uninfluenced orebody in destroyed zone; For the remnant ore, a drift recovery scheme and series of trenchs are proposed. All of these mining methods can achieve safe and high efficient mining for orebody with multiple mined out areas.(2) On the basis of analyzing the possibility of caving, a new caving scheme that synchronous mining in upper and lower mining areas based on critical value of continuous caving is purposed. It realizes the objective of the simultaneous exploitation of destroyed orebody by mined out areas and deep primary ore, and problems such as low productivity of ores and waste rock mixed too many are also solved. Meanwhile, the rationality and the safety of this scheme are analyzed by FLAC 3D.(3) On the basis of analyzing influencing factors of development system, the technical measure of excavating in sublevels simultaneous is proposed to accelerate the development process in the deep. In addition, the problem of mutual interference between production in the shallow and development in the deep is sovled by optimization of hoisting system.(4) On the principle of adaptation to ground pressure, safety and being pritical, a new supporting method that overall arch shed over roof falling zone is proposed by reaserch on the area of falling zone and the character of arch supporting. So, the problem of repairing caving zone rapidly and safely is sovled. And, on the basis of analyzing ground pressure and particularity of bulk layer, the technical measure of shotcrete bolt mesh and U-shaped bracket combined supporting is proposed to meet the demand of roadway stability in ore block with high pressure or fragile ore block; forepoling bolt and U-shaped bracket combined supporting solves the problem of roadway passing bulk layer, and ensures production can normal run in bulk layer zone.In summary, technologies presented in this paper include inclined drift and flat bottom trench structure for the orebody destroyed by illegal mining, single trench structure and an improved sublevel caving scheme for uninfluenced orebody in destroyed zone, caving scheme that synchronous mining in upper and lower mining areas, the optimization of hoisting system and measures of accelerating the development process in deep. Theoretical research and production practices show that these technologies adapt to mining conditions. And these comprehensive mining technologies of orebody with multiple mined out areas can achieve safe and high efficient mining.