Study On The Overlying Strata Movement Law And Control Technology Of "Three Soft" Coal Seam Up-dip Working Face

China's Huaibei region has a common occurrence of“three soft”coal seams and its geological conditions are complex.Affected by geological structures,many working faces that tend to be arranged along the dip direction are also faced with the difficulties of large up-dip angle mining in the mining along the strike direction,resulting in the movement law of overlying strata and the behavior law of mine pressure show different characteristics from the general stope.Affected by factors such as“three softs”,working face inclination,and up-dip angle,the rib spalling and support drilling in the working face is serious.Therefore,in this paper,combined with the mining conditions of Guobei mine8105^-1 working face,the field investigation and theoretical analysis,physical experiment,numerical simulation and field measurement was used to systematically study the overlying strata movement law and control technology of"three soft"coal seam up-dip working face,and the main research results are as follows:?1?Based on the theory of elastic thin plates,the initial and periodic fracture mechanics models of the basic roof of the“three soft”coal seam up-dip mining face under combined action of lateral and longitudinal loads are established,and the mechanical characteristics along the strike and dip of the basic roof and the main factors influencing its distribution are obtained.The initial fracture and periodic fracture criteria of the basic roof of“three soft”coal seam up-dip mining face was given;The paper theoretically analyzes the initial fracture and periodic fracture form of the basic roof of“three soft”coal seam up-dip mining face,and two types of“”and“”fracture forms that are distinguished from“O-X”fracture is proposed;The FLAC^3D three-dimensional numerical model of“three soft”coal seam up-dip mining face is established to study the stress evolution law and plastic zone distribution characteristics of the roof during the mining of working face,which verified the accuracy of the two fracture forms proposed in the theoretical analysis.?2?The UDEC numerical calculation model of the“three soft”coal seam up-dip mining face was established,the overlying strata collapse law,the roof mining stress,the distribution of the overlying strata displacement,and the different up-dip mining angles on the stress distribution and overlying strata movement of the working face were studied.The shifts and the causes of the vertical displacement curve of the basic roof and the pressure arches above the mining space under different up-dip mining angles were analyzed.?3?Using the KJ216 coal mine roof dynamic detection system,the average initial fracture step distance of the Guobei mine 8105^-1 up-dip working face is 32.93m,the average periodic pressure step distance is 18.54m,the periodic pressure step distance is approximately equal,verifying the results of theoretical analysis and numerical simulation.By analyzing the measured data,the initial support force,the distribution characteristics of the working resistance and the distribution characteristics of the working face resistance of the different working stations were analyzed.From the side,the interpretation of the characteristics of the initial fracture and periodic fracture of basic roof based on thin plate basic roof fracture criterion was confirmed.?4?Based on the analysis and study of the movement law of overlying strata in the“three soft”coal seam up-dip mining face,the numerical simulation and theoretical analysis of the coal wall rib spalling and the support drilling during actual mining of the working face were carried out,anti-rib spalling technology of water injection in shallow hole of coal wall,reducing mining height,rapid shifting of the top of the roof,management of the advancement of a beam and a column,and other measures to effectively reduce the occurrence of rib spalling and roof leakage;The method of enhancing the strength of the floor and increasing the piston rod hinged at the front end of the support base to increase the tilting arrangement of the jack can effectively prevent the support from drilling into the floor,ensuring the smooth transition of the support and ensuring that the working face is normally advanced.