Stability Analysis Of Roof - Pillar In Goaf Of 1 # Copper Mine In Dahongshan Iron Mine

At present, instability of large mined-out area is one of the major hazard installations in the mine. And it would influence the mine enterprise economic development and people’s life and property security seriously. However, the stability of goaf is determined by the two basic elements of pillar and roof. And they are the most important structure unit which reflect the stability of the goaf. Therefore, the core of studying the stability of mine goaf is to studying the stability of roof and pillar. Taking Dahongshan Iron Mine Goaf as engineering background, this paper collected some data and made some field investigation. Then it studied the stability of goaf-roof and pillar in room and pillar mining method deeply by using various means of theoretical analysis and numerical simulation. And its main work and achievements are:1) it collected the data of Dahongshan Iron Mine No.1copper800～880segments of room and pillar method of goaf and made some field investigation. Then it summarized the goaf roof pillar damage model and the mechanism and influence factors of unstability. And it calculated the safety thickness of gob roof by using four theoretical methods which included beam theory, span to depth ratio method, flat beam theory and the pressure-arch theory. Then it deduced the relationship of safety thickness and span of the goaf-roof. And it calculated the load and strength of the goaf-roof to get the safety coefficient of goaf-pillar in Dahongshan Iron ore mining and analyzed the stability of pillar goaf.2) Based on the pressure arch theory it analyzed the roof and pillar of goaf by using numerical simulation analysis and got the following conclusion:(1)Change rules of pressure arch boundary with successive mining stope roof;(2)The room and pillar and the vertical stress distribution;(3)Isolating effect of the disc area pillar;(4)The vertical displacement distribution of room and pillar and roof;(5)Continue mining influence on adjacent mined-chamber;(6)Room and pillar method of goaf damage is divided into4stages:the stage of stable pillar, the pillar of large deformation stage, instability of part of pillar, instability of the all. It expounds the mechanism of instability of the goaf in room and pillar method and found the essence of pressure arch which is a expanding dynamic iterative expansion arch structure of "balance-instability-rebalancing-instability" along with the continuous mining stope.3) With the factors of leading to mutation instability of goaf roof-pillar system, it found that instability and mutation of the system and the energy in the process is determined by its geometric characteristics of the system. Using the conclusion and the formula of this paper, combining with mechanical and geometrical parameters of Dahongshan Iron Mine of1#copper840subsection gob roof-pillar system and using the necessary and sufficient conditions of system, it calculated the stability of this goaf. The results showed that the size, structure and rock mechanical parameters of the goaf could meet the requirement of stability. And the goaf was stable. Therefore, the scientific, rational design of structure size of goaf, improving physical and mechanical properties of surrounding rock could avoid that the system reached the mutation conditions occur and ensure the safety production in mine.