Study On Safe Treatment Technologies Of Unsteady Goaf In Paishanlou Gold Mine

With the rapid development of mineral resources exploitation, the mines who is threatened by goaf caving become more and more. Now, how to handle goaf safely, efficiently and economically, has been the important problem of production technology solved imminently in the mining engineering.Transferred from open pit to underground mining, Paishanlou gold mine is mining ore body outside boundary by using the pillar sublevel open stope method. The goaf’s scale is very large under the open slope, which the goaf’s projected area of at+275m level is about11,250square meter, and the total volume of goaf is about0.5million cubic meter. At present, the roof rock has been in active state, and the ore quantity of more than0.4million tons need be mined imminently, meanwhile surface upper goaf is not allowed to collapse because the open pit has been tailings reservoir for stacking toxic tailings. In order to realize safe treatment of goaf, rational recovery of resources and effective protection of surface rock movement, this paper study systematically on the problem of goaf caving, control of caving, goaf disposal, safety guarantee, etc.By using the method of numerical simulation, this paper analyze the influencing factors of goaf stability including goaf shape, position relation of goafs, blasting vibration and weak planes of joints, and points out the distribution features of surrounding rock stress and the key point of bearing structure. Meanwhile the paper establishes a mechanical model of three hinged arch, and evaluates the stability of surrounding rock structure, and estimates the critical span and caving height of goaf. Then, this paper puts forward a conclusion that goaf roof can cave to surface.For analyzing caving form and controlling the range of goaf caving, this paper uses the comprehensive treatment scheme which there are drilling monitoring upper the goaf, preserving pillar in the middle of goaf to prevent caving, excavating packed well step by step from surface and filling goaf with waste stones. The RG monitoring images show that roof rock mass is complete from17.3m to32.3m in X line section and from35.1m to46.5m in VIII line section that can be used to control rock for preventing goaf caving. In order to realize the target, this paper preserves a12m-15m width pillar on the VI line, and makes together with trend pillar to form a "L" support structure for limiting the caving height, and fills waste stones to the goaf through packed well for reinforcing the load-bearing arch of surrounding rock and providing the bigger waste stones overburden to the stoping of low-grade ore under the goaf. Then, when the ore has been stoped, top filling by crushed stone concrete forms the steady bearing structure to prevent surface subsidence. In the scheme, digging packed well on the surface is the key engineering, for ensuring construction speed and safety this paper designs a technical proposal including digging packed well by VCR method, RG monitoring and warning device.At present, the scheme has been in full operation, and three packed wells have been excavated successfully by using VCR method, and0.4million cubic meter waste stones could be filled into goaf which protect the weak part of bearing structure and control effectively goaf caving. In addition,0.35million tons ores have been mined, ore recovery is83.5%, and ore dilution ratio is15.2%. As the conclusion, the idea goal of safe treatment of goaf and rational recovery of resources has been realized.In addition, this paper study on the problem of seepage when goaf roof caves to the surface for the safety of tailings reservoir. According to the actual conditions, paper puts forward an anti-seepage curtain preparedness that there are filling collapse crater rapidly with waste stones, thick loess grouting and cement grouting to fracture. Then, this paper gets the best concentration of yellow mud through the physical experiment.In sum, these comprehensive treatment technologies of unsteady goaf including the mechanical model of covariant bridge arch, excavating packed well by VCR method, filling with waste rock and drilling filling with crushed stone concrete, monitoring by RG, seepage preparedness of yellow mud filling and cement grouting, not only ensure the stability of open pit slope and the resource recovery, but also guarantee the safety of goaf disposal. So, this is a new applied technology of goaf disposal which is safe, economy and efficient.