Study On Supporting Technology Of Roadway In Deep Extra-soft Coal With High Gas

Liangbei coal mine is recognized as a “double-outburst” coal mine by the state.The coal seam II1 is a typical "three soft" coal seam,whose dip is 8 ~ 15 °,thickness is 3 ~ 6m with an average of 4.18 m,and the hardness coefficient f is 0.15 ~ 0.25 with an average of 0.18.The whole coal seam is extra-soft and its structure is simple.The current mining level is-550 m,and the depth of coal roadway is 610 ~750m,which is located below the depth of softening critical.The coefficient of difficulty on the comprehensive support is more than 1.5 to 2.0,and the engineering practice shows that the roadway is supported quite difficultly.Meanwhile,the coal has some features in Liangbei mine,such as its soft coal,the poor ventilation,the high gas content,the high gas pressure,the high earth stress,the hazardous of easy outburst,and the difficulty on drainage.During the roadway excavating,gas outburst prevention and so on influences the excavating of coal roadway seriously and a succession of mining and excavating in Liangbei coal mine.This study focused mainly on the difficulty on deep high gas content and extra-soft coal roadway support in Liangbei coal mine.Through the research of engineering geological conditions and deformation characteristics and mechanism of II1 coal roadway in mining area 11 at-550 m level,Both the gas drainage and the roadway supporting stability are considered comprehensively.From the perspective of improving excavating speed and ensure the roadway stability,the support technology of etra-soft-coal roadway with high gas content in deep is researched.The new ideas,new materials,new processes,new technologies are used in the study,and the main results are made as follows:1.The high-convex steel strip is introduced into the bolt-mesh-cable coupling support technology,and the high convex strip-prestressed bolt-mesh-cable coupling support technology is put forward,and the supporting construction technology is developed,which success in the test roadway engineering of the mining area 11 and win the obvious economic and social benefits.2.The strength test is used for thin broken rock,which lays a solid foundation for subsequent analysis of the project.Meanwhile,according to characteristics of rock mass structure,the latest version of Hoek-Brown strength criterion is used to determine the strength of engineering geological rockmass groups,which is the important reference of the parameters determination in numerical analysis,and improves the results credibility of the numerical analysis.3.The engineering geological rockmass groups are divided.The characteristics of the tectonic stress field are determined.The roadway deformation mechanics mechanism at mining area 11 is ascertained.The main reason of the deformation and failure of coal roadway under the condition of the original support is found,the right support countermeasures is developed.The new technology-convex strip-prestressed bolt-mesh-cable coupling support technology,is successfully used for stability controlling of roadway in mining area 11.4.Based on the idea that the effective method to transform the low permeability reservoir is using pressure relief technology,adjusts the original program from the stand point of synergistic reaction between roadway support stability and efficient drainage.The adjusted program raises the coal roadway tunneling rate from 45 meter per month to over 70 meter per month,solves the problems of both gas outburst and over proof in coal roadway in mining area 11 in Liangbei Coal Mine,and achieves quick excavation of the coal roadway.5.The gas control of the “three soft” coal roadway is combined with the roadway support technology successfully.Coal beside roadway is not broken during the gas outburst prevention of coal roadway.Then bolt-mesh supporting was adopted to strengthen stability of the coal beside roadway,and weaken the effect of the floor heave.The application of comprehensive technology solves the problem of rapid excavation in the high gas content and extra-soft-coal roadway in Liangbei coal mine effectively,and relieves the pressure of mining and tunneling.