Mechanism Of Cemented Filling To Prevent Pillar Goaf Roof Disaster

Shanxi,Inner Mongolia and Shaanxi provinces accounted for 72 percent of the country’s raw coal output in 2021,and the western region has become the country’s main coal production base.However,in the past decades,due to the low level of production technology and equipment and relatively backward production technology,coal mining is extensive and simple,resulting in many mining areas using room and column mining,leaving a large number of columnar goaf with different sizes,isolated or groups,and poor distribution regularity.A large number of irregular coal pillars are left in the columnar goaf.Under the coupling action of overburden stress,disturbance load,natural weathering and water erosion,the coal pillars gradually lose stability and their bearing capacity decreases,resulting in local stress concentration.The instability of coal pillar will induce the instability of adjacent coal pillar,which will produce "domino effect" and lead to the roof disaster of goaf.In this thesis,theoretical analysis,laboratory test,physical similarity simulation,numerical analysis and other research methods were used to study the disaster mechanism and prevention methods of pillar goaf roof instability,and the following research results were obtained:(1)Taking the damage degree of coal pillar and roof as the standard,the instability of roof and remaining coal pillar in goaf is summarized into four states,and the plastic zone,stress and strength of remaining coal pillar in goaf are analyzed,and the safety factor of stability of coal pillar is 1.54.(2)The evolution process of coal pillar group instability and large area roof collapse in pillar goaf was simulated and analyzed by three-dimensional physical similarity simulation test,the dynamic change law of coal pillar support capacity weakening to instability was revealed,and the prevention and control method of goaf roof disaster prevention by filling and strengthening coal pillar was proposed.(3)Through the creep orthogonal experiment of backfill reinforced coal pillar,the co-bearing law of coal pillar and backfill body under the condition of different backfill thickness,strength and loading speed is obtained,and the primary and secondary relationship of the influence of various factors on the creep strength of coal pillar is summarized.(4)The stress distribution characteristics of coal pillar and filling body and the movement and deformation of surrounding rock are analyzed when the coal pillar is strengthened with cemented filling materials of different filling thickness and strength,so as to verify the obvious effect of filling and strengthening coal pillar in controlling roof disaster.There are 50 figures,13 tables and 72 references in this thesis.