Research On Key Strata Breaking Laws By Continuous Mining Methods And Roof Control

Based on corner coal recycled engineering background in 2-2# coal seam of Selian 1st Coal Mine, in site sampling tests, theoretical calculations and analysis, numerical simulation and analysis and field experient were undertaken to research the stability mechanism of coal pillars,overlying strata movement and key strata breaking laws and roof control technology. The major achievements are as follows:(1) The mechanics model of residual coal pillars was established by catastrophe theory,and its mechanical instability changed by:when elastic zone width of coal pillar is less than 14%, if slight disturbing from outside is occurred. We also verified the results with numerical simulation and field experient, revealing that instability mechanism of coal pillar to isolate sections is reasonable.(2) According to geological conditions in 2-2# coal seam of Selian 1st Coal Mine, combined with histogram of the coal petrography and key strata judgment software to find that multi-layers structure of key strata. Based on this we built the mechanical model to calculate the fracture length and weighting step of key strata with elastic plate theory, the calculation for special situations were revised by us. All of these provided a theoretical basis for roof control in continuous mining.(3) The 2-2# coal seam excavated process model was built by FLAC3 D numerical simulation software, by monitoring stress, displacement and yield area changes of coal pillars and key strata, we could analyze relevance between coal pillar stability and key strata breaking, besides we still analyze key strata breaking laws of Block-Stage Mining process. In conclusion,coal pillars and key strata can be seen as a system of "coal pillar-master key strata- secondary key strata ", key strata with the face forward bent down in the middle of the lower edge of slab pull damage zone appears first, followed by shear failure slab around the central area eventually pulled through the slab destruction, advancing to the first cycle occurred about 26 m broken, then there is a cycle by about 7m breaking.(4) Analyze the role played by protective coal pillars and sand filling to the goaf, through numerical simulation to study mechanisms and effects of sand filling to the goaf. In conclusion, the scene for the isolation section of pillar width of 12 ~ 15m; on the one hand sand filling to the goaf can protect coal pillars to reduce the development of the yield zones, which can give full play to its mining process the supporting role of the overburden; on the other hand, it can effectively control the overburden, especially curved main sink, sub critical layers.