Research On Supporting Technology And Equipment In Ultra Large Height Mining Face

Generally,the working surface with cutting height of 3.5m?6.0m was called fully-mechanized working surface with large mining height,and the working surface with cutting height of more than 6.0m was called fully-mechanized mining face with super-large mining height.The thickness of coal seam 1-2 in the fourth panel of Shangwan in Shendong coal mine was 5.35m?9.6m,and the average thickness was 8.9m.With the adoption of one-time and full-height mode of comprehensive mechanized mining.Fully-mechanized working surface with super large mining height had several characteristics,such as the cutting height and strength of coal was high,the coal wall formed rib spalling easily,the roof caved easily,the load of the equipment was high and dynamic impact load was serious.Hydraulic support was the core equipment for controlling the structural stability of surrounding rock in working surface.Its adaptability,stability and reliability to surrounding rock directly determined the success or failure of fully-mechanized mining technology with super-large mining height.According to this problem,this paper adopted the method of job-site survey,theoretical analysis,numerical simulation and the combination of indoor test and field test,and the following researches were carried out:(1)This paper measured physical and mechanical properties of 8.8m high working surface coal in Shendong mining area.The overburden movement law of fully-mechanized working surface with super large mining height in Shendong mining area was studied by using key stratum theory.Taking different mining heights,different working face lengths and different support strengths as research dimensions,the law of rock pressure appearance of working surface was studied.The first weighting step,periodic weighting step and the length of the first mining surface were determined.Also the support strength of working surface is preliminarily determined.(2)Quantitatively analyzed the main factors that affected rib spalling,and proposed the mechanics basis of rib spalling.It was determined that shear failure was the main form of formation of rib spalling in fully-mechanized working surface with super large mining height in Shendong mining area.The main factors affecting rib spalling were mining height,mechanical properties of coal and support strength.The height and depth of rib spalling were calculated.This paper studies the probability distribution of rib spalling on the working surface with super large mining height,and proposed the probability distribution function of rib spalling.Muti-objective optimization of factor weighted average methods was used to construct the decision model of coal wall stability grade,and the stability grade of working surface was determined,which belonged to medium stability coal wall.Then this paper studied the quantitative distribution of large coal cinder and proposed its mathematical model,predicted the possible quantities of large coal cinder in the process of mining,which provided data support for the design and selection of equipment in fully-mechanized mining working surface.(3)By analyzing the coupling relationship between hydraulic support and the strength,stiffness and stability of the surrounding rock,proposing the adaptability of support to surrounding rock,and combing the geological and mechanical conditions of working surface,this paper determined the main technical parameters of hydraulic support with great height.Further more,this paper studied the main factors that affected the strength of rib spalling under the coupling effect between coal and rock,and proposed several prevention and control measures.(4)In order to establish a mechanical model for the stability of support and propose several measures to increase the bidirectional stability of hydraulic support,qualitative and quantitative analysis was also needed to research the main factors that affected the transverse and longitudinal stability in the working process of hydraulic support.The multistage telescopic column of hydraulic support with great height was unbalanced under pressure,by studying that,the critical condition and judgement basis could be obtained.The columns bore the impact loads such as rock pressure,by studying the response characteristics,we could propose several technical measures to increase the impact resistance of columns.(5)Besides,this paper analyzed the logical relationship of reliability between hydraulic support system and its components,and made a comparison of reliability between two-column and four-column pillars,which provided a theoretical basis for choosing the two-column scheme.This paper separately analyzed the shear force,stretching force,torque and bending moment of roof beam,caving shield,connecting rod and foundation plate of hydraulic support.This paper also analyzed the reliability,life and the complex loading condition,as well as the possible areas where design defects may existed.The Bootstrap method was used to do the re-sample analysis of data collected from the stress-strain concentration area around the pillar of the support roof beam.This paper also used the computing methods of normal stress mean value and variance,and the result had high accuracy and reliability.The research work in this paper is of great theoretical and practical significance to the full-mechanized mining engineering of ultra large mining height working face.This paper consists of 66 pictures,25 tables and 155 reference documents.