Study On Energy-distance Effect Of Roadway Damage Caused By Impact Of Thick And Hard Roof

As an indispensable excavation space in coal mine production,the stability of roadways is of great significance to safe production.According to research statistics,more than 85%of rock burst phenomena occur in roadways,especially in roadway with thick and hard roof overburden.A large number of field practices have shown that the degree of destruction of roadway surrounding rock is not only related to the source energy,but also related to the source distance.Based on the engineering background of Hujiahe Coal Mine in Shaanxi Province,the research objective is to study the energy-distance effect relationship of rock burst roadway failure.This thesis comprehensively uses indoor experiments,theoretical analysis,numerical simulation,and typical case verification methods to conduct research and analysis,analyzes the deformation and failure characteristics of coal and rock samples under dynamic and static loads,reveals the mechanical mechanism of thick and hard roof impact roadway failure,and studies the energy distance effect relationship of thick and hard roof overlying rock impact roadway failure,Compared with typical mine cases,the main results include:1)The crack propagation law and deformation and failure characteristics of standard coal and rock samples under dynamic and static loads are analyzed.The indoor mechanical properties of coal and rock samples were tested,and the mesoscopic parameters were verified and analyzed using PFC^2Dnumerical simulation software;Furthermore,the deformation and failure characteristics and crack propagation law of coal and rock under dynamic load are simulated.The results show that compared with the failure of coal and rock under uniaxial loading,the dynamic load action time is shorter but the damage caused is extremely strong;Under the same impact energy,the number of fractures in coal and rock samples can be divided into slow growth and linear rapid growth stages;The strength of the specimen under dynamic loading condition as shock disturbed degree increased and improved,and the increase in the ultimate strength of coal and rock slows down when the impact energy increases to a certain value.2)The failure mechanics mechanism of surrounding rock of impact roadway under the energy release due to fracture of thick and hard roof is revealed.A mechanical model of impact roadway failure with thick and hard roof was constructed,and mechanical analysis was conducted for the initial collapse and periodic fracture instability of the basic roof,respectively.The total energy released by roof fracture in both cases was calculated;Studied the dynamic load in the transmission mechanism of rock strata and the attenuation law of vibration wave;Based on the static load superposition principle,the stress and energy criteria for roadway impact damage are obtained through formula calculation,and the influencing factors for roadway impact damage with thick and hard roof are analyzed.3)The failure energy distance effect relationship between the surrounding rock of the roadway impacted by the front and side roof is studied.Using the FLAC^3Dnumerical simulation software,the influence of different focal energies and different focal distances on the destruction of roadway surrounding rock is analyzed.Research shows that there is a critical impact dynamic load intensity（energy）for roadway destruction under positive roof impact.Beyond this critical value,roadway surrounding rock destruction is severe and deformation increases rapidly,with strong particle vibration and displacement responses;There exists a critical impact distance for roadway failure.When the impact source distance is less than this critical value,the particle vibration velocity of the surrounding rock of the roadway is large and the damage is serious;For side roof impact,there are also critical impact energy and critical impact distance for roadway failure.4)The influence of different energy-distance ratio on the deformation and failure of surrounding rock of roadway covered with thick hard roof slabs was simulated.The research shows that the degree（grade）of roadway impact damage can be classified according to the magnitude of the energy distance ratio（the ratio of source energy to distance）;When the energy distance ratio is 10²,there is no impact,10³,there is slight impact,10⁴,there is medium impact,and 10⁵,there is strong impact;10⁶and above will cause major disasters.5)Typical engineering case statistics are in good agreement with the previous research results,the rationality of classifying roadway impact damage levels based on the energy distance ratio is preliminarily verified.There are 66 figures,12 tables and 82 references in this thesis.