Yield Failure Process Of 1000m Middle Horizontal Pillar In Jinchuan No.2 Mine And Its Influence On The Stability Of The Roadway

Jinchuan Mine Area is the third largest production base of nickel ores in the world.Its associated products have the third largest output of copper in the country,the forth in cobalt in the world,and the first in platinum group metals in Asia.It is known as the nickel capital of China.Nickel,cobalt,and platinum group metals are extremely important to the development of the current aviations and defense industries.Therefore,ensuring the safe and stable production in Jinchuan Mine Area(especially in the main mine area of No.2)plays an key role in national economic construction.At present,with the mining of the middle section of 1000m,the Jinchuan No.2 Mine Area faces two major problems:(1)When will the horizontal mine pillar of 1000m yield?Whether its instability occur or not in the future?(2)With the appearance of the horizontal pillar in the middle section of 1000m and the continuous decrease in its thickness,how does it affect the safety of tunnels located along the vein in the hanging wall of ore?Aiming at the above-mentioned problems,this paper combined with the project-"Distribution Law of Stress Field Before and After Mining of 1000m Middle Section in Jinchuan No.2 Mine Area",has carried out the works as follows:(1)The regional geological background of Jinchuan No.2 mine area including tectonic environment,rock characteristics and in-situ stress fields is summarized.(2)A two-dimensional finite element model including ore,rock,filler and tunnels is established,according to which the yield critical thickness of the 1000m and 1150m horizontal mine pillars are predicted;By comparison of stresses and displacements between the two horizontal mine pillars at their different thicknesses,the damage of the 1000-m horizontal pillar is evaluated;Meanwhile,the time-and space-damage laws of tunnels located along the vein in the hanging wall of ore at different thicknesses of the 1000m horizontal mine pillar are obtained.(3)The horizontal pillar is simplified as an elastic foundation beam under the action of the axial force,by using which the deflection curves of the horizontal pillar with respect to different thicknesses is calculated,as well as the influence of large tectonic principal stress in the transverse direction of the ore vein on the deflections of the horizontal pillar is analyzed;In addition,the possibility of the buckling of the 1000m horizontal pillar in the future is estimated by the energy method.