Engineering Geological Characteristics of the Wind-oxidized Zone of Bedrock in the Working Face:Taking Zhangji Coal Mine in Huainan Mining Area as an Example
The shallow working face of the hidden coal field is affected by the wind-oxidized zone of the bedrock of the roof,and under the influence of wind-oxidization,the engineering geological conditions of the rock body deteriorate,which has a greater impact on the management of the roof of the working face and the prevention and control of water hazards.The engineering geological characteristics of wind-oxidized zone were studied in the working face of 1410(3)near loose layer in Zhangji coal mine,Huainan mining area,Anhui Province,as an example.Based on the drilling project of the underground roof of the working face,cores were taken within 30 m of the roof of the working face,and on the basis of which,the mineral composition analysis of the wind-oxidized zone rocks was carried out by X-ray diffraction(XRD).The physical and mechanical property tests of fresh and wind-oxidized rocks were carried out by indoor physical and mechanical tests,and the depth and degree of development of the wind-oxidized zone on the top of the working face were evaluated based on the rock mechanical properties and macro-geological characteristics of the core.The results show that the mineral composition of bedrock wind-oxidized zone is dominated by kaolinite,montmorillonite,illite and other clay minerals,which are easy to expand in contact with water,and are beneficial to inhibit the development of water-conducting crack zones in the roof slab.Under the influence of wind-oxidized action,the porosity of the rock increases by about 15％,and the uniaxial compressive strength is reduced by about 50％,which makes the deterioration of the engineering geological conditions of the mudstone more obvious than that of the sandstone.The depth of the wind-oxidized zone of bedrock in the working face is about 16～20 m,and the wind-oxidized degree is divided into grades.The degree of rock wind oxidation is mainly manifested as strong weathering-complete weathering.The research results provide the basis and reference for the selection of support type and roof management of the working face,and provide reference for the exploration of wind-oxidized zone and evaluation of engineering geological conditions of the working face under similar conditions.
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