Instability Mechanism And Control Technology Of Surrounding Rock In Gob-side Entry Retaining Of Shallow Embedment And Without Filling Wall

In view of the lack of long-term study on the pressure mechanism of the gob free entry,the need to strengthen the support design such as the selection of the combined support and the auxiliary unit in the roadway,the lack of analysis and Research on various factors affecting the instability of the gob free entry,and the lack of further Exploration on the general applicability of the gob free entry technology,the study is based on the 5101 working face of laomupo mine The research object,using the methods of laboratory test,theoretical analysis and numerical simulation,has carried out the research on the instability mechanism and related control technology of the surrounding rock in the gob side entry without wall,and has achieved the following main results:(1)This paper presents the structural mechanics model of overlying rock mass in gob free entry,summarizes its movement mode and characteristics,carries out the parameter research of arc triangle block,and calculates the roof subsidence of gob free entry.The mechanical properties of surrounding rock and supporting materials are tested.The design of the combined support for the side cutting of the gob side entry without wall is carried out,and the cutting resistance is checked.(2)The numerical simulation calculation of the side cutting load and the supporting load in the roadway without wall is carried out.When 400 kN and 600 kN cutting load are used,the upper stratum appears separation layer,but it is not cut along the roadway side;when 800 KN cutting load is used,the separation layer expands,and the cracks before cutting along the roadway side are produced,but still not cut along the roadway side completely;when 1000 KN cutting load is used,It has been completely cut along the side of the roadway,and the best cutting load is 1000 KN.Through the simulation of the auxiliary support in the roadway,two rows of props are selected for high cost performance.On this basis,the research on the movement law and stress distribution of the surrounding rock in the retained roadway under the disturbance of sublevel mining is carried out.(3)Based on the analysis of the influencing factors of the instability of the gob side entry without wall,the key influencing factors are selected,and the single factor analysis is carried out to find out the influence of the key factors on the instability of the surrounding rock of the gob side entry without wall.The roof subsidence is in direct proportion to the mining height,mining depth,lateral pressure coefficient and roadway width,and the roof subsidence is in inverse proportion to the direct roof thickness and direct roof strength Through the comprehensive analysis of multi factors,the weight of each key influencing factor is obtained,which is mining depth > direct roof thickness > mining height > roadway width > direct roof thickness.(4)The roadway side support is composed of bolt beam,wire mesh and combination of single hydraulic support and I-steel roof cutting combination support.The side wall of the goaf is closed with air leakage proof isolation mold and elastic material spraying.The simulated deformation of the remained roadway is 392 mm along the top and floor of the roadway,and 243 mm along the two sides,both of which reach the maximum deformation speed at 40 m behind the working face;when it reaches 80 m,the deformation gradually stabilizes and basically reaches the maximum value;YTJ20 rock layer detector is used for borehole peeping monitoring,and the analysis shows that most of the roof is broken It occurs in the shallow part and develops to the deep part,which proves that the grouting reinforcement has good control effect on roof subsidence and damage,and the integrity of the deep surrounding rock is good.The paper has 64 figures,17 tables and 98 references.