| The hard roof generally has the characteristics of high hardness,high density,large thickness and strong self-stabilizing ability,which supports the overburden.Usually the hard roof is difficult to collapse by itself,forming a large area of suspended roof,which leads to the increase of the stress concentration coefficient of the working face,and adversely affects the support of the working face and the management of the roof.Once the hard roof collapses in a large area,huge energy will be released,leading to accidents on the working face.Based on the thick hard roof of1313 working face of Weiqiang Coal Mine as the background,and on the premise of safe mining of working face,this paper studies the initial mining and caving technology of thick hard roof of 1313 working face of Weiqiang Coal Mine by means of field measurement,theoretical analysis,numerical simulation and field industrial experiment,and obtains the following results:(1)Through borehole peeping method,it is found that there are relatively developed fractures in the direct roof of the working face,while there are a few fractures in the old roof and the degree of development is not high.The theoretical formula is used to calculate the old roof as the key layer of the working face,and the analysis shows that the old roof belongs to the IVA level,and the ore pressure is very strong.As it may cause the ore pressure burst,roof caving measures should be taken.The roof breaking mode is O-X type(2)Based on the analysis of "two fields and one zone" of working face based on FLAC3 D software,it is found that under the influence of mining,there is a certain degree of stress concentration in front of coal wall and coal pillar,and the triangle area and the edge of roof belong to the difficult caving area in the process of roof breaking.The fracture field of 1313 working face is mainly distributed in and above the roof,presenting a ? type distribution.The middle roof is more developed,while the corner corner is less developed.(3)The mechanism of hydraulic fracturing is analyzed.Aiming at the shortcomings of low efficiency and inaccurate position of conventional grooving tools,a kind of cutter which can realize one hole repeatedly grooving is proposed,which greatly improves the working efficiency and the accuracy of grooving.Combined with the previous experience of hydraulic fracturing and the evolution law of stress field,plastic zone and fracture field of working face,the initial mining and roof caving scheme and technology of hydraulic fracturing for thick hard roof of 1313 working face were designed..(4)Hydraulic fracturing in Weiqiang coal mine 1313 working face mining caving the scene at the beginning of practice,the effect of hydraulic fracturing,roof caving conditions,working face support work situation and the coal Weiqiang,pillar and roof and floor deformation condition monitoring,analysis summarized the effect of hydraulic fracturing,hydraulic fracturing technology can effectively reduce the first weighting interval and strength,to ensure safety in production during the preliminary extraction.There are 60 pictures,18 tables and 83 references in this paper. |
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