| Deep mining is faced with the strong influence of ’ three high and one disturbance’and has problems such as large gangue production,low lifting efficiency,and complex control of surrounding rock in the stope.Against this background,the integrated technology of mining,selection,and filling provides an effective way to solve the above problems.Gob-side entry retaining in the deep backfilling mining face and gob-side entry driving with narrow coal pillar is an important part of the integrated miningdressing-filling technology system,which can reduce the tunneling rate and maintenance cost of the roadway and reduce the loss of coal to some extent.However,although some scholars have researched the technology of gob-side entry retaining and gob-side entry driving on the filling side of the working face,it is still in the preliminary exploration stage.The influence of the filling body,the roadway side’s mechanical properties,and the supporting structure on the gob-side entry’s stability still needs to be determined.Therefore,this paper adopted the research methods of theoretical analysis,laboratory tests,numerical simulation,and field measurement to simulate and analyze the characteristics of confined compressive stress and deformation of gangue under engineering conditions.The deformation and failure characteristics of the combination of roof and gob-side coal-rock mass were studied.The method of using discrete element numerical simulation software to determine the parameters of the supporting structure of gob-side entry was proposed.The influence of the supporting system on surrounding rock failure of gob-side entry was discussed.The stability control strategy of the surrounding rock of gob-side entry filled with deep thick and hard roofs was constructed to ensure the control effect of gob-side entry retaining and gob-side entry driving.The research results can provide a theoretical basis and reference for the stability control of gob-side entry in deep backfilling working faces.The following innovative results were achieved:(1)The compaction and bearing characteristics of the gangue filling body were studied,and the gangue compression test was designed.The influence of particle size and initial porosity on gangue compressive stress,strain,and block crushing was analyzed,and the compaction characteristics of gangue filling body in the experimental scale were obtained.According to the morphological characteristics of the gangue block,a three-dimensional block discrete element numerical simulation method for gangue compression is innovatively proposed,which can be broken again and generate a threedimensional block discrete element with a specified particle size range and porosity.The proposed method was used to establish a numerical simulation scheme.The influence of particle size range,initial porosity,and model size on the mechanical properties of gangue compression was simulated,and the rationality of the method was verified.Finally,a suitable large-scale numerical model was established.Considering the tamping effect of hydraulic support,the Salamon formula was used to fit the stress and deformation curve of gangue-confined compression,and the fitting parameter is E0= 4.1 MPa.εm = 0.32.(2)The combination of coal rock mass and roof compression experiments were designed to combine coal rock mass and roof siltstone,two typical types of coal rock mass and filling material.By analyzing the failure,deformation,and acoustic emission characteristics of anchorage and non-anchorage specimens in the process of stress loading,the adaptability of the two types of roadway protection materials as coal rock mass protection was obtained.A UDEC-Trigon-Weibull discrete element simulation method was proposed considering the heterogeneity and deterioration characteristics of the rock mass.The microscopic parameter characteristics of the combination were analyzed and verified by comparison with experiments.The proposed method was used to study the fracture development,stress characteristics,and energy distribution characteristics of the combined specimen under the strength of the filling body,the strength of the hard rock,the uniformity index of the coal and rock mass,and the thickness of the hard rock from the laboratory scale.It provides a basis for selecting coal and rock mass materials and support design for filling gob-side entry retaining.(3)According to the engineering conditions of gob-side entry retaining in thick and hard roof backfilling working face,the method of using UDEC numerical analysis to determine the parameters of supporting structure of gob-side entry retaining was proposed.For the gob-side entry retaining in the goaf filling condition,the influence of supporting structure on the stability of gob-side entry retaining is further studied from the perspective of the displacement field,fissure field,and energy field of surrounding rock.(4)Based on the theory of elastic foundation beam,the mechanical interaction model of roof,coal-rock mass of roadway protection,and filling body in goaf was established.The influence of the foundation stiffness of the filling body in goaf,the foundation stiffness of coal-rock mass of roadway protection,and the width of coalrock mass of roadway protection on the subsidence of thick and hard roof of gob-side entry was analyzed.Considering the horizontal stability of the coal-rock mass of roadway protection,a mechanical model based on Coulomb’s earth pressure theory was established.The minimum width index of coal-rock mass of roadway protection to maintain lateral stability was obtained.Based on the theory of elastic foundation beam,a piecewise mechanical model considering partial dense filling in goaf was established,and the deflection curves of roof rock beam under different dense filling lengths were obtained.Based on the variation law of compressive bearing stress and strain of gangue in goaf,the influence of main factors on roadway stability was studied by numerical simulation,and the relevant parameters of a gob-side entry meeting the requirements of deformation control were determined.(5)The large deformation control countermeasures of gob-side entry retaining based on the ’ three-body ’(gob filling body + gob-side entry retaining coal-rock mass+ supporting structure)synergy principle were proposed.Combined with the actual situation and the study of the bearing characteristics of the filling body,the roof combination failure characteristics of the gob-side entry retaining coal-rock mass and the roof deformation characteristics,the gob-side entry retaining(driving)parameters of the working face were designed,and the control effect of gob-side entry retaining was ensured in the application site.This thesis has 121 figures,20 tables and 193 references. |
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