Study On The Support Type Selection Theory Of Fully Mechanized Mining Face In Shallow Seam With Peak-cluster Landform

Typical peak-cluster landforms represented by Guizhou in southwest China,the surface is more undulating and more mountainous terrain.During mining of shallow seam with peak-cluster landform,the coal seam depth changes greatly,the mining pressure appears unusually strong,the safety valve opening rate of hydraulic support is high even the phenomenon of bracket being pressed.It is not conducive to ensuring safe and efficient production of mines.In this paper,1107 face of hair ear coal mine is a field research object.Comprehensive use of field research and measurement,laboratory physical simulation,numerical simulation and theoretical analysis and other research means,In this paper,the characteristics of overburden movement and the Law of rock pressure appearing in the fully mechanized mining face in the shallow seam of the peak-cluster landform are analyzed systematically.Based on this research conclusion,the reasonable selection of hydraulic support in working face is carried out.The main findings are as follows:(1)Similar simulation results show that: The basic roof of the face of the first collapse step distance of 42.5m,a total of eight cycles to pressure,the period of pressure step distance between 14.4~23.1m,the average 18.4m.To the Valley mining period to the average pressure step distance of 18.7m,the bottom section of the mining is 19.9m,back Valley section mining for 15 m.The average of the periodic pressure-step distance presents the characteristics of the "bottom section and the Valley section and the Back Valley segment".(2)In the similar simulation experiment,the average load of bracket in Valley mining,bottom mining and back Valley mining stage is 2760 kN,2680kN and 3150 kN respectively.The "High Pressure zone" and "Low pressure zone" appear periodically in the face pressure,the influence range and the overall value of the "High Pressure zone" are the largest in the back Valley mining stage.Because of the existence of the surface of mountain slope,the mining of Back Valley section there exists vertical load and horizontal force between rock bodies,resulting in horizontal displacement of overlying strata,insufficient frictional force between rock blocks,slipping instability easily,and difficulty in supporting support in Back Valley stage.The working resistance of the bracket reaches the maximum of 4300 kN in the back Valley segment,exceeding 26.4% of the resistance of the actual working surface bracket,indicating that the existing bracket cannot provide enough support strength.(3)Using FLAC3 D numerical simulation software to analyze: the characteristics of the stress concentration of the front coal rock mass under the influence of mining in the face is the feature of "Back Valley section and Valley section".(4)Based on existing research results,according to the different states of "given deformation" and "limited deformation",the relationship between bracket and surrounding rock is analyzed.The calculation of different strength support scheme is carried out,and the reasonable working resistance of hydraulic support supporting is obtained.(5)According to the different states of "given deformation" and "limited deformation",the relationship between bracket and surrounding rock is analyzed.Combined with the above experimental results,the different strength support schemes are calculated and the reasonable hydraulic support work resistance is obtained.