Deformation Failure Mechanism Of Slope Rock Mass And Mining Control Technology In Highwall Mining Of Open-pit Coal Mine

Ningwu Coalfield coal bed floor Ao L aquifer is characterized by high pressure,strong water enrichment and stable recharge,which poses a serious challenge to safe and efficient mining in mines.Based on the hydrogeological characteristics of Ningwu Coalfield and typical mine coal seam-aquifer-diaphragm storage characteristics,this thesis comprehensively utilizes laboratory tests,field measurements,numerical simulations,theoretical analyses,and industrial tests to systematically study the evolution law of mining water-blocking characteristics of high-pressure water-blocking diaphragm,taking the storage characteristics of the diaphragm as an entry point,and controlling the diaphragm’s equivalent thickness of water-blocking as the core.The following research results have been achieved:（1）A model for evaluating the risk of water breakout in the coal bed floor in Ningwu Coalfield was established,and the type of water trap deposits was classified based on the characteristics of the rock strata within the damage range of mining.Combined with the geological conditions of Ningwu Coalfield,we constructed the main controlling factor system of coal bed water breakout and AHP hierarchical analysis model of coal bed water breakout,and clarified the main factors affecting the water breakout of the bed as the thickness of the water barrier,water pressure of the aquifer,and the depth of the coal seam;we used the gray correlation analysis method to clarify the sensitivity of the factors affecting the depth of the water barrier destruction,and put forward the linear and modified nonlinear regression model for predicting the depth of the water barrier destruction and verified the applicability,and based on the characteristics of the rock stratum in the range of the damage caused by the mining,we classified the type of the water barrier existence into the single structural type,the double-layer structural type,and the soft and hard composite type.（2）Defined the progressive damage characteristics of the combined specimens,characterized the damage variables of different combinations of rock types,established a coupled stress-damage-permeability model and verified its applicability.The larger the height ratio of sandstone in the combined specimen,the greater the overall peak strength,cutline modulus and modulus of elasticity of the specimen,which reveals the expansion of cracks from soft to hard and from inside to outside during the loading process,and the linear decrease of the residual strength with the increase of the proportion of mudstone,and the residual strength of different combinations of types of rock is used to characterize the damage variables,and a coupled stress-damage-permeability model is established to consider the whole process of matrix compression-fusion-rupture.A coupled stress-damage-permeability model considering the whole process of matrix compression,fusion and rupture was established,and a stress-strain-permeability curve model based on rock damage was constructed by combining with the Drucker-Prager criterion,and relevant parameters such as m₀,F₀,ζand the damage variable D were fitted,which is of good applicability.（3）Established the floor mining damage detection technology and applied it,and clarified the characteristics of mining damage and the evolution of seepage characteristics of diaphragms of different storage types.An integrated detection technology based on multi-source information fusion is established,and a quantitative characterization method of drilling fissures based on MATLAB image processing is proposed,and a negative logarithmic decrease in the percentage of mining fissure area with the increase of drilling depth is clar ified.Combined with numerical simulation,it is clarified that the process of overburden compaction of collapsed rock blocks in the mining area adjusts the stress state of the base plate,but does not change the destructive pattern of the base plate,and the irregular gradient distribution of the permeability of the base plate is grasped;and it is clarified that the"load-bearing"effect of hard rock and the"buffer"effect of soft rock are proposed on the basis of the MATLAB image processing.On the basis of clarifying the hard rock"bearing"and soft rock"buffer"effects,it is proposed that the degree of disturbance of different types of watertight layer by mining mainly depends on the layer position and thickness of soft rock.（4）Revealed the plastic slip mechanism of the mining damage zone,clarified the permeability evolution law of the mining damage zone under the mining stress path,and elucidated the evolution law of the mining water-resistance characteristics of the floor.According to the over-supporting pressure caused by the depth of damage to the footing of the layer in the construction of a single structure-type water barrier,double structure-type water barrier three kinds of damage state,soft and hard composite water barrier five kinds of damage state of the mechanical model,a clear plastic slip line in the interface between the rock layers in the extension of the helix characteristics,through the example of the quantification of water barrier endowment type of the footing of the mining damage depth of constraints.The mining stress path was equivalently converted into laboratory loading path,and the permeability evolution law of rock formation in mining damage zone under different mining stress paths was quantified,and the relationship between rock permeability and bias stress was characterized by using the exponential function segmentation;and it was clarified that the height of pressurized water-conducting uplift fissure development was directly proportional to the width of the fissure,inversely proportional to the fissure roughness,and logarithmically related to the pressurized water hydraulic pressure.The analytical solutions of the mining water resistance coefficient and the equivalent water resistance thickness of the water barrier based on permeability were obtained,the calculation method of the floor water resistance coefficient was modified,and the quantitative characterization method of the parabolic decline of the floor water resistance characteristics with the increase of the depth of burial,the length of the working face,the bearing pressure of the aquifer,and the height of the mining height was put forward.（5）Constructed a technical system of zoned and graded modification of the water barrier to increase resistance and conducted industrial tests.The mining damage characteristics of the diaphragm under different mining conditions and grouting effects were clarified,and the depth of the diaphragm mining damage increased linearly with the increase of the burial depth and the length of the working face,and decreased with the increase of the friction angle and cohesion of the rock layer,and the"damage reduction and damage reduction"diaphragm modification and drag enhancement control based on the equivalent water-blocking thickness was put forward.Countermeasures are proposed based on the equivalent water-blocking thickness of"reducing damage and decreasing damage",and water barrier modification and blockage control is developed,with corresponding grouting materials and processes,combined with the monitoring and early warning system of the effect of water barrier grouting reinforcement and modification,and the water barrier modification and blockage increase technology system is constructed by zoning and grading,and the industrial test is carried out in the hard-soft-hard composite water barrier of the Longquan Coal Mine 4301 working face,and in the single-structured soft-rock type of the Fenyuan Coal Mine 5-104 working face,to validate the validity and reliability of the theory.validity and reliability.This thesis has 99 figures,39 tables and 229 references.