| Overburden breakage and water flowing fractured are key factors a ffecting the safe mining of the mine.Based on the geological conditions of the 42114 working face of Liang Shui-jing Coal Mine,the thesis comprehensively adopts the research methods of theoretical analysis,physical simulation,numerical simulation,and industrial test.Firstly,it analyzes the breaking characteristics of thin bedrock with thick unconsolidated stratas and the development law of water flowing fractured.Then,a more systematic analysis of the development regularity of the water flowing fractured zone under different unconsolidated stratas thicknesses and different mining heights was carried out,and the main research results are as follows:(1)Based on the discriminating theory of the key stratum and the drilling column,determine 42114 face as a single key strata face.The thickness ratio of bedrock stratum to unconsolidated stratum is 0.47,of which bedrock strata thickness is 50.1 5m and unconsolidated strata thickness is 107.60m.(2)Physical simulations show that the initial collapse step of the immediate roof of the 42114 wo rking face is 20m,the initial pressure step of the basic stratum is 40m,and the periodic pressure step of the basic roof is about 16m,the basic roof is fully cut along the coal wall of the working face,cutting angle is about 56°.With the advancement of the working face,the development height of the water flowing fractured on the side of the working face is continuously increasing.The mining fissure in the middle of the goaf have undergone a period of "development-opening-closing" periodic change.the final development height of the water flowing fractured is 68.9m,about 19 times the height.The final distribution pattern of water-condu cting fissures is "half-side trapezoid".(3)Numerical simulations show that the initial collapse step of the immediate roof of the 42114 working face is 22m,the initial pressure step of the basic roof is 38m,and the the periodic pressure step of the basic roof is 17m,when the basic roof periodically breaks,the structures of basic bedrock strata above and the unconsolidated stratum become unstable,and them sink synchronously with the basic roof,the overburden breaks down to show the phenomenon of"step sinking".With the advancement of the working face,the development height of the water-conducting fissures on the side of the working face and the side of the cut-out continued to increase,and the final development height of the water-conducting fissures was 75 meters,which was about 25 times the mining height.In the middle of the goaf,most mining fractures are closed,and the final distribution of water-conducting fractures is "trapezoid".(4)Both physical and numerical simulations show that there are three mutations in the development law of mining fractures:First,before the first break of the basic roof,the mining fracture has not penetrated the basic roof.When the basic roof is first pressed,the separation fracture is rapid It developed into the bedrock strata above the basic roof,and the water-conducting fissure did not develop into the bedrock strata above the basic roof;Second,after the first to second cycles of the basic roof occurred,the separation crack developed to the bottom of the unconsolidated strata for the first time and quickly.The water-conducting fissure develops into the bedrock strata above the basic top;Thirdly,continue to advance the working face,the separation-strata fissure continues to develop up to the surface,the water-conducting fissure develops to the lower part of the unconsolidated strata,and the water-conducting fissure development height is basically stable.(5)The main influencing factors of the height of water-conducting fissure zone are mining height,thickness ratio of bedrock strata and unconsolidated stratum.Among them,the height of water-conducting fissure zone is positively correlated with mining height and negatively related to the thickness ratio of bedrock strata and unconsolidated stratum.At the same time,it is concluded that when the thickness ratio of the bedrock strata to the unconsolidated strata is<0.8 and the mining height is 4.5 meters,the height of the water conducting fracture zone is 20 to 24 times the mining height;when the thickness ratio of the bedrock strata to the unconsolidated strata is>0.8,the mining height is at 4.5m,the water-conducting fissure reaches the surface directly.(6)Based on multiple sets of different unconsolidated strata thicknesses,different mining height numerical calculation models and on-site measured data,it is determined that under the condition of 0.4<base rock strata and unconsolidated strata thickness ratio<1.6,1.0 meters?mining height?4.5 meters,the relationship between the two-dimensional linear function of the height of the overlying water-conducting fissure zone in the thick bedrock of thin bedrock. |
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