Research On Cutting Roof Pressure Relief And Surrounding Rock Control Technology For Roadway Driving Along Goaf In Dongtan Mine

In deep coal mining,it is difficult to control the surrounding rock of the roadway along the goaf with the hard roof.Failure to collapse the hard roof in time will form a large area of suspended roof on the side of the coal pillar in the lower section,which will bring great harm to the stability of the surrounding rock along the goaf roadway.And the sudden breaking of the roof in the later stage is prone to a series of problems such as impact load,storm,induced rock burst and other dynamic disasters.Aiming at the hard roof,the method of cutting roof pressure is usually adopted to cut off the stress transmission and cantilever length of the hard roof,and new support schemes are proposed to make the surrounding rock of the roadway along the goaf be effectively controlled.Aiming at the problem of the hard roof suspended in Dongtan Coal Mine,this thesis uses the 6306 working face as the research background,combines on-site investigation,laboratory experiment,theoretical analysis,numerical simulation and field practice and other methods.Through analyzing the fracture pattern of the hard roof,the basic The breaking position of the roof affects the stability and stress evolution of the surrounding rock of the roadway along the goaf;the blasting roof cutting technology and the roof breaking form after roof cutting are studied,and a new support plan is proposed for the stability of the roadway surrounding rock after roof cutting.In addition,industrial experiments are carried out with 6306 track roadway as the research object.The specific research contents are as follows:(1)Four breaking methods for the basic roof of roadway driving along the goaf are analyzed.Based on the fixed beam model,combined with the site roof conditions,the maximum bending moment and the maximum collapse step of the hard roof are calculated.Under the condition of the hard basic roof of the working face,the basic roof will not collapse in time if there is a large overhang after mining.Under the influence of roadway excavation in the lower section,the hard roof will break,and the location of the break has an important influence on the stability of the roadway in the lower section.(2)A numerical simulation model of roof breaking position and stress evolution under different roof cutting angles was established,the optimal roof cutting angle was obtained,and the influence of roof breaking position on the roof cutting effect was analyzed.The results show that if the top-cutting angle is too large,the overlying rock strata of the goaf and the overlying roadway along the goaf will form a relatively large friction force on the fracture surface under the action of horizontal thrust,making the rock above the goaf unable to It collapses smoothly;if the roof cutting angle is too small,the overlying roof slab along the goaf roadway will form a longer suspended roof on the side of the goaf,which increases the stress concentration on the coal pillar and is extremely unfavorable for controlling the deformation of surrounding rock.Therefore,the simulation has obtained the best position of the roof cutting top.(3)Based on the theory of blasting impact and its relationship with the response of the rock formation,the mechanism of blasting shock wave rupture of the rock formation is revealed,and the fracture mode of the rock mass under impact load is analyzed.On-site rock-like brittle materials are subjected to dynamic impact loads,and tensile stresses are generated in the vertical and cracked surfaces,and open fracture occurs.The rock breaks in this area,and the crack continues to expand at the tip of the crack.A cracked area appears.Outside the cracked area,impact load occurs.Attenuate the elastic vibration zone.(4)The surrounding rock deformation support system of the large section roadway of Dongtan Mine was established,which revealed the surrounding rock deformation mechanism and realized effective control of the surrounding rock of the roadway.After pre-cutting the roof,the roof structure has been optimized.For this reason,a new support plan is proposed for the roadway along the goaf.The monitoring data of the onsite support effect shows that the deformation of the surrounding rock is reduced and the bearing capacity of the coal pillar is effectively improved.The total deformation of the surrounding rock on site is controlled within 30-60 mm,and the change rate of the anchor cable stress is controlled within the range of 13%～16%,which ensures the longterm safety and stability of the roadway along the goaf.There are 70 figures,7 tables and 100 references in this thesis.