Study On Load Bearing Mechanism Of Warped Beam Structure And Deformation Collapse Characteristics Of Overlying Rock

Ground surface subsidence caused by strata movement due to coal mining is strongly linked with the deformation and damage of mining overburden structure.A clear understanding about the structure and deformation characteristics of overburden layer is the basis for people to predict overburden movement and subsidence development process.The previous researches on mining overburden structure are mainly hypothesis of structural bearing mode based on the overburden structure and the plate-beam structure theory of pressure-bearing stratum material characteristics.The first structural hypothesis focuses on the analysis of structural bearing area form on both sides of the worked-out section,but rarely analyzes the bearing mechanism of the structure and the quantification of the bearing area.By contrast,the second plate-beam structure researches focus on the rock deformation characteristics with stronger bearing capacity in the upper part of mined-out area,but fail to clearly explain the structure bearing mechanism and load mode within the mining influencing scope in front of the working surface,and just superficially analyze the interaction relationship between the upper structure and lower structure.In addition,the influence of structural support body and rock beam warping sequence on the development trend of overburden warping is not taken into consideration when strata structure damage is analyzed.Therefore,the study of the above problems is considerably significant for the prediction of mine pressure disaster areas and subsidence areas.In order to solve the above problems,it is necessary to establish mechanical structure that considers time factor,contains the main mining influence scopes on the space,and especially can meet the analysis of the working surface front structure state so as to provide research based for bearing strata structure,strata structure bearing mechanism,bearing area classification.Therefore,"cantilever beam" structure theory was introduced into the coal strata structure analysis as the basis of mechanics model.Combining the reality of mines,with the "key strata theory" and "transfer rock beam theory" of the strata structure as the basis,the structure form within the mining influencing scope of local strata structure in the process of extraction was analyzed.Moreover,a rock beam warping structure was put forward and then classified.Rock beam warping structure is suitable for the occurrence condition of coal seam with near horizontal and simple geologic structure.Besides,its basic characteristics were analyzed.Form the aspect of the loading mode of the rock beam warping structure,the bearing mechanism of conducted rock beam warping structure and its effect on deformation of overburden rock caving characteristics were studied through theoretical analysis,numerical simulation experiment,field measurement and coal-rock physical mechanics experiment.The interaction between the bearing mode and the overlying structure of rock beam warping structure was discussed.Based on the elastic damage transfer coefficient,the numerical relationship between the damage process and the changes of bearing capacity of rock beam was established.Furthermore,the range of bearing capacity was quantified.With SW4102 working surface of Xiaonan Iron Mine as an example,the bearing area scope of mining process was calculated,and verified through field separation layer test.In view of the overburden deformation,the deformation characteristics and function of the rock beam warping structure were analyzed.With the composite beam theory,the mechanism of rock warping structure cantilever to local rock formation deformation was analyzed.The load-bearing mode and overburden deformation characteristics of typical and non-typical rock beams warping structures were analyzed by FLAC3D numerical simulation.Aiming at the overburden warping,the overburden warping process was simulated with RFPA numerical simulation software.Based on the damage of rock beam warping structure,the characteristics and development process of overburden warping were analyzed.Besides,the characteristic equation of trapezoidal warping in local overburden control layer was established.The rock layer warping sequence of the local overburden structure was judged.The influence of the damage of the rear supporting body in the whole beam stage of the rock beam warping structure on overburden warping characteristics was analyzed.Based on the instableility damage sequence between bearing beam and the coal wall plastic softening characteristics,the theoretical calculation formula of overburden warping extension process was deduced.It was revealed that the extension process of overburden warping was related to the rear supporting damage of the whole beam stage of rock beam warping structure.The physical and mechanical experiments of coal-rock were carried out,and the theoretical calculation parameters of overburden caving expansion process were obtained.Similarly,by taking SW4102 working surface as an example,the theoretical calculation of overburden warping expansion process was conducted.The characteristics of overburden movement were analyzed by monitoring data of surface rock movement,and the calculated results were analyzed and verified by combining with the data of rock movement.