Research On Key Technologies And Rock Pressure Law Of 110 Mining Method With Compound Hard Roof In Tashan Coal Mine

Coal plays an extremely important strategic role in energy development and application in China and the world.However,with the large-scale exploitation of coal resources,problems have gradually emerged such as increasing mining depth,resource shortage,rock pressure control and so on.The traditional coal miming methods and processed need to be optimized urgently.Through the combination use of constant resistance large deformation anchor cable(CRLDAC)support technology,bidirectional energy-gathering tension blasting(BETB)technology,retained entry temporary support technology,gangue wall maintaining support technology and so on,the roof cutting pressure releasing no coal pillar gob-side entry retaining mining method(110 mining method)can realize the mining without section pillars leaving and additional filling materials using.This technology greatly improves the coal mining rate of mining area and greatly reduces the section roadway excavation rate,which has the wide application prospect and high research value.In order to further expand the applicable geological conditions of this technology,deepen the theoretical study of roof cutting pressure releasing and excavate more application forms of roof cutting pressure releasing technology,this paper takes 8304 working face of Tashan coal mine as an example to carry out the study about the application of roof cutting pressure releasing no coal pillar mining technology and the law of rock pressure under compound hard roof condition.The specific research contents are as follows:(1)The basic principle of 110 mining method is summarized at first,and on this basis,the technological process of this technology is summed up to six steps and related key technologies are extracted according to each technological step,including BETB technology,CRLDAC support technology,gangue wall maintaining support technology,retained entry temporary support technology,combined blasting technology,etc.Then this paper deduces the stress state evolution process of entry surrounding rock with 110 mining method,which provides a theoretical basis for the following entry support design.Finally,the geological conditions of the test face are summarized and preliminarily analyzed as the basic data for subsequent design of key parameters of roof cutting entry retaining and analysis of rock pressure laws.(2)Aiming at the characteristic of compound hard roof in test face,the key parameters design of entry retaining with roof cutting are systematically studied.Firstly,the roof lithology is inspected in detail through roof lithology peep and rock mechanics experiment;secondly,according to mechanics deduction and geometric analysis,the geometric parameters such as roof cutting height and angle are designed with zoning;then,the key parameters about roof cutting blasting are determined by experiments and optimized by intelligent algorithm;finally,the entry support scheme during retaining process is designed systemically.The key parameters of each procedure in roof cutting entry retaining are obtained,and a complete design method system is formed,which can provide a certain design reference for the optimization and promotion of 110 mining method.(3)After the detailed geological investigation and roof cutting entry retaining design of test working face,the mechanism and effect of roof cutting pressure releasing have been thoroughly studied by means of field test and numerical simulation,and the surrounding rock structure and stress distribution characteristics of the roadway under the condition of roof cutting pressure releasing have been further revealed.Firstly,based on the law of overburden strata movement,the mechanical structure of roof cutting short beam is analyzed;secondly,the stress distribution characteristics of entry surrounding rock in each technological stage of 110 mining method are explored;then,the working face weighting characteristics under this technology are studied and summarized;finally,on the basis of the above research,the following entry deformation law and the rock pressure law of working face in the retained entry reuse process are also studied.By exploring the regularity of entry deformation and stope pressure in the whole process cycle of entry retaining and reuse,not only the roof cutting pressure releasing principle is further explained from the theoretical level,but also the effect of roof cutting pressure releasing is verified in the experimental practice.(4)In order to explore the pressure distribution characteristics of entry surrounding rock with roof cutting under different composite roof structures and to further optimize the support design during entry retaining under different geological conditions,mechanical analysis and numerical simulation are used to study the structural characteristics and the roof cutting pressure releasing effect of compound roof.In addition,the 8304 working face of Tashan coal mine is taken as an engineering example,and the above theoretical research results are verified by the monitoring of rock pressure and entry deformation.The research results show that the weak interlayer in the compound roof is easy to be destroyed under external force,and its stratum distribution has a key influence on the overall characteristics of the roof.In the roof cutting pressure releasing gob-side entry retaining with compound roof,when the weak interlayer is in the middle of the roof cutting range,the strength requirement of the entry support is the highest;when the weak interlayer is at the top of the roof cutting range,the strength requirement of the entry support is the lowest.With the increase of the weak strata height in the roof cutting range,the peak value of stress concentration on the coal wall side first decreases,then increases,and then decreases,the variable trend can be fitted by a cubic equation curve.(5)The control of roof weighting at the beginning and end of longwall face mining has a great influence on its safety production and continuity.Based on the study of roof cutting pressure releasing technology mechanism and its application of entry retaining,the open-off cut roof cutting pressure releasing technology and retracement channel roof cutting pressure releasing technology are put forward.Firstly,the mechanisms of the two technologies and the design method of key parameters are summarized.Then,mechanical calculation and numerical simulation are used to analyze the roof cutting pressure releasing effect and the stress evolution process of surrounding rock.The feasibility of the two technologies is verified theoretically.Finally,the field test is carried out at 8304 working face of Tashan coal mine.The field test results show that the open-off cut roof cutting pressure releasing technology can effectively shorten the first weighting step length and weaken the first weighting strength of the working face,and the retracement channel roof cutting pressure releasing technology can effectively reduce the mining pressure at the end mining stage of working face,which all have good pressure releasing effects.