| Roadway deformation and failure is one of the main factors restricting the safe and efficient mining in coal mine.The deformation and failure mechanism of roadway is complex and controlled by many factors.In order to reveal the deformation mechanism of stope floor roadway,the No.8 main mining seam floor of Luling mine in Huaibei mining area is taken as the study object in this paper,and the sedimentary strata structure of the coal seam floor and the characteristics of the mine ground stress field are analyzed;meanwhile combined with the methods of theoretical analysis,numerical simulation,similar material simulation and field measurement,the deformation mechanism of stope floor roadway is systematically studied,which reveals the control mechanism of ground stress and sedimentary strata structure on the floor roadway deformation.Finally,the following research results and conclusions are obtained:(1)Based on the analysis of sedimentary environment and lithologic combination characteristics in the study area,the floor strata of No.8 coal seam is divided into two types of sedimentary mode,i.e.,the type of distributary bay-crevasse splay and the type of flood basin-distributary channel;and it is concluded the No.8 coal seam floor is composed of two types of sedimentary strata structure:full mudstone type(type ?),sandstone and mudstone interbedded type(type ?).(2)The ground stress in the mine is tested and analyzed with stress relieving method and AE method.The results show that the maximum principal stress is between 19.94?33.65MPa,and the direction is 73.2°?105.6°,nearly east-west direction,and the ground stress field in the mine is dominated by tectonic stress.Then the FLAC3D software is used to inverse the distribution characteristics of the stress field,which shows that the distribution of ground stress in Luling mine has obvious regional difference.(3)The stress solution model of the stope floor roadway is simplified as a semi-infinite space with a circular hole in the interior part of the elastic body.With the method of complex variable function,the elastic mechanical solution of the stress of the stope floor roadway is deduced under the influence of the primary rock stress and abutment stress.The results show that under the condition of high ground stress,the stope floor roadway wall is prone to tensile failure,and the roadway roof is prone to shear failure,and it is obvious with the increase of lateral pressure coefficient.(4)Two kinds of engineering geological model of sedimentary strata structure are established,combined with numerical simulation and similar material simulation,then the stress evolution of the stope floor and deformation characteristics of the roadway under different ground stress field are analyzed.The results show:?Under the condition of self-weight stress,there exists some differences between the two types of sedimentary strata structure in the mining induced stress evolution of the stope floor and the deformation characteristics of the roadway,i.e.,the stress increase and stress relief of the floor strata of type ? structure are all greater than those of type I structure,but the difference is small,mainly due to the sandstone with high mechanical strength is contained in the floor strata of type ? structure;?Under the condition of tectonic stress,there exists obvious differences between the two types of sedimentary strata structure in the mining induced stress evolution of the stope floor,i.e.,the mining induced stress of type ? structure is divided into two zones in the vertical range of the floor:stress concentration zone and stress recovery zone;while type ? structure is divided into three zones,and the stress inflection point appears at the interface of lithology,which shows that the differences of sedimentary structure of floor strata are magnified under tectonic stress condition;?Under the condition of tectonic stress,compressive stress is the main stress in the goaf floor,and under the condition of self-weight stress,tensile stress is the main factor,so the failure modes of floor roadway are obviously different.Under tectonic stress condition,the roadway is mostly compressive shear failure,while the tensile stress failure is mostly under self-weight stress condition.It reveals the control mechanism of ground stress field on roadway deformation.?Under the condition of tectonic stress,the floor roadway deformation of type ?structure is larger than that of type ? structure.(5)A boundary fault model with sedimentary strata structure of type ? is established,combined with numerical simulation and similar material simulation,to study the stress evolution of floor strata and the deformation of floor roadway when coal mining is along or against the fault tendency.The results show that the fault zone plays an important role in controlling the stress evolution of the stope floor strata:?When the mining direction is against the fault tendency,the mining induced stress is obstructed by the fault zone,and the stress concentration is produced on the upper plate.When the mining direction is along the fault tendency,the mining induced stress is transferred to the opposite plate through the fault zone.It reveals that the fault zone acts as a 'shield' to the mining induced stress when mining direction against fault tendency;?The deformation of floor roadway is different when the position between the roadway and the fault changes.The deformation of floor roadway near the fault zone is greater,while the deformation of floor roadway far away from the fault zone is smaller.It shows the control mechanism of boundary faults on the roadway deformation.(6)With a self-developed monitoring device for mining induced stress,the synchronous monitoring on mining induced stress of floor roadway is carried out during coal mining.It shows that the vertical stress state of the floor roadway appears the process of stress increase,stress relief and stress recovery,and the range of stress increase is obviously less than stress relief.The influence of stress relief of the goaf on the floor roadway is obviously higher than the influence of concentrated stress ahead of the working face,which is consistent with numerical simulation results.(7)The deformation of floor roadway during coal mining is tested synchronously,the results show:?The deformation of the floor roadway below the goaf is larger than that ahead of the working face;the roadway deformation is obviously controlled by ground stress,and the difference of roadway deformation can better correspond with stress partition;the roadway deformation is large in the position with higher initial stress.It reveals the control mechanism of ground stress field on the deformation of roadway surrounding rock;?When the ground stress is the same but the sedimentary strata structure is different,the roadway deformation is also different,i.e.,the roadway deformation of type ? is smaller than that of the type ?.It reveals the control mechanism of the sedimentary strata structure on the deformation of roadway surrounding rock.The differences of roadway deformation in Luling mine are mainly caused by the combined effects of sedimentary strata structure and ground stress,and the stability of the floor roadway of type ? structure is better than that of type ? structure. |
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