Deformation And Failure Lows Of Coal Pillars And Joint Control Technology In Soft And Thick Coal Seam

The coal pillar can effectively improve the stress distribution in the lower working face,with clear and understandable principles and simple techniques,effectively maintaining the normal operation of the roadway in the lower working face.However,in soft and thick coal seams,the height of coal pillars is high,the exposed area of coal walls is large,and the geological conditions such as soft coal and developed fissures easily lead to serious instability of coal pillars,making roadway maintenance extremely difficult.At present,there are few studies on the shear failure of coal pillars,and it is urgent to carry out research on the failure laws and control techniques of coal pillars.Taking the mining of Coal Seam 3 # in Fuyan Mine as an engineering background,this thesis conducts research on coal pillars in the 3109 working face section,analyzes the deformation and failure mechanism of coal pillars under the influence of mining,establishes a theoretical model of shear slide blocks in the side of deep coal roadway based on the limit equilibrium theory,analyzes the width of the limit equilibrium zone of coal pillars and the stress distribution law,and explores the mechanism of shear slide blocks in the coal slope,Based on theory and practice,the control measures for coal pillar stability are proposed and the reinforcement effect is verified through on-site engineering practice.Based on the above research,the main achievements of this thesis are as follows:(1)The movement of the shear slider on the side of the coal pillar is a phenomenon of sliding and collapsing deformation of the broken surrounding rock caused by the mining of the upper working face.A theoretical mechanical model of shear slide in surrounding rock of deep coal roadway is established using an accurate solution of limit equilibrium analysis,and a mathematical model of safety coefficient of shear slide is derived.Through limit equilibrium theory and superposition theory,determine the movement range of the coal pillar shear slider and the vertical stress distribution law of the coal pillar,and solve the distribution law of the safety coefficient of the coal pillar shear slider: at 0～1.26 m,the safety coefficient of the upper part of the coal pillar is small,and at 1.26～3.95 m,the safety coefficient of the middle part of the coal pillar is large and small,which is prone to coal damage due to roof pressure.(2)Based on the shear slider theoretical model,a collaborative control strategy of "crack prevention,gap reduction,and slip prevention" is proposed,and joint control measures are adopted in the surface layer of the roadway,the shallow,deep,and severely unstable parts of the surrounding rock.Based on this,a joint control technology of coal pillar with "reinforcement anchor cable-grouting reinforcement-advance roof cutting" as the main body is proposed: using side reinforcement anchor cable to connect the shallow bearing structure with the deep stable coal body of the coal pillar;Grouting is used to reinforce the loose coal mass in the bonded roadway to form a stable bearing structure;Advance roof cutting improves the stress state of the coal pillar and ensures the normal production of the working face.(3)Using numerical simulation methods,the distribution characteristics of deformation,stress,cracks,and plastic zone of roadway surrounding rock under the scheme of unsupported,original anchor and cable support,reinforced anchor and cable grouting reinforcement and advanced roof cutting support were studied.The results show that after adopting the combined control technology of reinforcing anchor cables,grouting reinforcement,and advanced roof cutting in the roadway,the deformation and floor heave of the coal pillar have been greatly controlled,and the side cracks of the coal pillar have been reduced by 62.89% and 46.26% compared to the unsupported and original supporting conditions,respectively.The integrity of the surrounding rock in the roadway has been greatly improved,forming a strong bearing structure.(4)The specific control scheme and parameters of coal pillars in the section of3109 working face were proposed,and the underground test was completed to monitor and evaluate the effectiveness of coal pillar prevention and control.After grouting,the strength of the coal body is increased by more than 60%,meeting the energy industry standards.The cracks in the coal pillar are fully filled,and the grouting effect is good;According to the on-site monitoring,the roadway displacement,anchor cable stress,and delamination are all within a controllable range,indicating that grouting effectively improves the bearing capacity of the coal pillar,controls the deformation of the 3109 transport roadway,and meets the requirements for normal use of the roadway.There are 52 figures,14 tables and 73 references in this thesis.