| In areas of coal seams that shallow buried and upper excavation limit lifted,rock mass is efflorescent-oxidized significantly,leading to:(1)weakening microstructures of coal and rock mass,(2)degradation of coal and rock strength,(3)increasing contents of clay minerals filled in pore of sandstone layer,and(4)sludge shape deterioration induced by roof aquifer leaching.The efflorescent-oxidized roadway surrounding rock,especially when the deterioration process promoted by roof aquifer leaching,has great hazards potential to the stability control of roadway surrounding.At present,the studies of basic theory and control technology of the grading of rock efflorescent oxidation,deformation mechanisms and stability control technology of roadway are desiderated.In this paper,a scientific problem was focused that the efflorescent-oxidized roadway undergoes instability and collapse induced by coupling of surrounding rock and fissure water in typical mining area.Two sub-problems were analyzed: first,the transformation and alteration behavior of rock mass in the shallow buried coal seams and efflorescent-oxidized area;second,the large deformation,instability and collapse of surrounding rock in the efflorescent-oxidized roadway.A synthetical analytical method has been applied,involving literature review,laboratory test analysis,similarity simulation,numerical simulation and theoretical analysis of efflorescent-oxidized roadway,so as to address the following issues.The mechanical properties of efflorescent-oxidized rock mass and the variation of mineral components were characterized.A comprehensive index of efflorescent-oxidation degree of rock mass was defined,of which a novel grading technique has been proposed.A constitutive equation of rock mass in different efflorescent oxidation degree and an oxidation model of rock strength parameters were established.The mechanical mechanism was revealed in the efflorescent-oxidized rock mass of unloading-dilatancy-expansion when the rock was excecated.The simulation experimental platform was developed to simulate deformation and failure of surrounding rock of efflorescent-oxidized and water-enrichment roadways.The evolving processes of surrounding rock deformation and fail were analyzed in varies efflorescent oxidation degrees roadway.A ground control technique has been proposed and implemented in coal mines,to achieve the goal of rock stability in the special hydrogeological areas for shallow buried coal seams and efflorescent-oxidized roadways.Main research results are listed as following:(1)The typical mine geology was investigated,then geological and hydrological data,engineering application data and rock test results of the efflorescent-oxidized rock mass were combined,to analyze the physical and mechanical properties,mineral composition and structural characteristics,founding loose structure,high content of clay mineral particles,low rock strength and poor self-stabilization in the efflorescent-oxidized rock mass.The physical and mechanical properties,mineral composition and structural characteristics of efflorescent-oxidized rock mass were studied.The variation characteristics of loose structure,high content of clay mineral particles,low overall strength and poor self-stabilization ability of efflorescent-oxidized rock mass were revealed.(2)A comprehensive index for the degree of rock efflorescent oxidation was defined,including five sub-indexes,they are: strength attenuation rate,variation coefficient for rock integrity,water absorption variation,permeability,and clay mineral content.The analytical hierarchy process and computer analysis software were applied to determine the weight value of the five sub-indexes.According to the comprehensive index of efflorescent oxidation degree of rock mass,the efflorescent-oxidized rock mass was divided into five grades: non-efflorescent oxidation,breeze efflorescent oxidation,weak efflorescent oxidation,moderate efflorescent oxidation and serious efflorescent oxidation.The efflorescent oxidation degree evaluation has been achieved both qualitatively and quantitively.The grading evaluation of different degree of efflorescent oxidation was realized by combining qualitative and quantitative methods.(3)Based on elastic-plastic mechanics and dilatancy-dilatancy theory,the mechanical model and the dilatancy-dilatancy model of surrounding rock in the process of "excavation unloading-support reinforcement" of efflorescent-oxidized roadway were established.The synergistic coupling relationship between dilatancy coefficient and plastic strain increment was analyzed,and constitutive equation of rock mass with different degrees of efflorescent oxidation and the model of rock strength parameters were established.According to the effective plastic strain,strength parameters and efflorescent oxidation modulus(cohesion and internal friction angle)are determined.The strength parameters of efflorescent-oxidized rock in a typical mining area were used to calculate the damage range of the efflorescent oxidation zone,the non-support rupture zone and the support rupture zone.(4)The similar simulation experiment platform for deformation and failure of surrounding rock of efflorescent-oxidized and water-enrichment roadway was developed.By using the experimental set,different material composition was designed to model varies efflorescent oxidation degree,the physical and numerical simulation experiments were carried out to simulate the deformation,instability and fail of surrounding rock.The evolving processes of surrounding rock deformation and fail were analyzed in varies efflorescent-oxidized roadways.(5)By analysis occurrence conditions of surrounding rock in efflorescent oxidation area in the No.3 Coal Mine of Pingshuo Mine Company of China Coal Mining Group,the technology has been implemented,a novel comprehensive technique has been proposed,which is called intermittent grouting in situ modification,by which the goal of stability of surrounding rock in the special hydrogeological efflorescent-oxidized area has been achieved.There are 124 figures,27 tables and 189 references in this dissertation. |
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