Theoretical Study On Recovering Strip Coal Pillar With Grouting Into Overburden Of Isolated Panels

Because of the strip mining,a large number of coal pillars have been left over for a long time.At present,the commonly used method of recovering strip coal pillar is underground filling technology,but it disturbs the mining severely.Therefore,this thesis proposes a new method.That is recovering strip coal pillars with grouting into overburden of isolated panels,or isolated grout injection(IGI).According to the principle of IGI,the basic thought of this method is to recover one strip coal pillar from the other in the strip mining area.The IGI has been successfully applied in dozens of coal mines for coal mining operation under buildings.However it is still a new attempt to use it for recovering strip coal pillars.It also lacks the research of relevant influencing factors and the design of construction process.With all this in mind,this thesis adopted a comprehensive methodology that incorporates theoretical analysis and numerical simulation to study the technology of recovering strip coal pillars with grouting into overburden of isolated panels.Firstly,the feasibility of the method was studied.According to the principle of IGI,it was shown that the method can be used for the recovery of strip coal pillar from three aspects,that was the overburden structure conditions,the compaction area and the control of surface movement and deformation.Aiming at finding the applicable conditions of the method to guide the implementation of the project,the effect of overburden conditions,mining width,mining degree and recovery rate on the result of this method were studied.Results indicated that: typical hard-and-thick strata existing in overburden was the ideal condition for the method;the efficiency in suiface subsidence control increased with the mining width and the recovery rate but decreased with the mining degree within limits.However combining the engineering fact,it pointed out that when the mining width was large,the overburden movement speed was accelerated,and the surface subsidence control and the application of IGI was more difficult.On the premise of guaranteeing the control effect of surface subsidence,the relatively small mining width can simultaneously combine the control effect of the subsidence and the implementation of the project,so the applicability was better.Take Wang Lou coal mine for example,construction process and determination of main parameters of the method was introduced.