Research On Gob-Side Entry Driving Technology Of Pre-Built Wall In 13131 Working Face Of Baiping Mine

In this thesis,the 13131 working face of Baiping Mine is taken as the research object.Through field investigation,laboratory experiment,numerical simulation and other methods,the causes of instability and failure of surrounding rock of roadway along goaf are analyzed.Through theoretical analysis and numerical simulation,the width of coal pillar and the size of pre-built wall are determined,and the influence of pre-splitting roof cutting on the stability of surrounding rock of gob-side entry driving is analyzed.On this basis,the control technology scheme of surrounding rock of gobside entry driving is put forward,and the field industrial test is carried out.The main conclusions are as follows :(1)The crossheading of 13131 working face in Baiping Mine belongs to high stress soft rock roadway.The deformation and failure characteristics of roadway surrounding rock are mainly roof subsidence,shoulder crack and two sides moving inward.Through field investigation and laboratory experiments,it is concluded that the main reasons for the deformation and failure of roadway surrounding rock are the large difference between roof and side lithology,poor bearing capacity of coal body,dynamic pressure influence and low supporting strength of roadway.(2)According to the deformation characteristics of gob-side entry driving under high stress,the mechanical analysis model of gob-side entry driving is established,and the simulation schemes of coal pillars with different widths and pre-built walls are designed.The stress distribution law and displacement variation characteristics of roadway surrounding rock are analyzed,and the minimum width of coal pillars is 4.76 m.The bearing capacity of the pre-built wall is calculated,and the minimum load of the wall is 16.2 MPa.According to the calculation results,the concrete of grade C25 is selected for pre-built wall masonry.With the increase of the width of coal pillar or prebuilt wall,its own bearing capacity and the stability of roadway surrounding rock are improved,and the deformation of surrounding rock decreases obviously.(3)The pressure relief effect of pre-splitting roof cutting on surrounding rock of roadway is analyzed by numerical simulation method.The monitoring results of internal stress of coal pillar and pre-built wall after roof cutting show that compared with gob-side entry driving without roof cutting,pre-splitting roof cutting can reduce the internal stress of roadway surrounding rock and effectively alleviate the influence of upper roof breaking and rotation on roadway majesty.By comparing and analyzing different width coal pillars and different pre-built wall size schemes,compared with coal pillars,the pre-built wall has high strength and good bearing performance,and the pre-built wall is constructed after the end of 13111 working face,which is less experienced than coal pillars.The influence of adjacent working face mining,the overall deformation of roadway is small,and the utilization rate of coal resources is high.Therefore,the pre-built wall gob-side entry driving is more suitable for 13131 working face tunneling,and the optimal width of the pre-built wall is determined to be2 m.(4)According to the geological conditions and surrounding rock deformation characteristics of the 13131 working face,and the stress blocking effect of the presplitting roof cutting on the roof strata,the anchor net support scheme of the 13131 working face is designed and the industrial test is carried out.The results show that the influence range of roadway excavation disturbance is 60 m,and the pre-built wall presplitting roof cutting combined with high-strength anchor net support scheme can ensure the stability of surrounding rock along goaf roadway.There are 71 figures,13 tables and 87 references in this thesis.