Study On Prediction Of Rock Burst And Risk About Deeply Buried Roadways In Underground Mine

Rock burst is one of the most common problems when mining ore bodies,it often brings many problems to the safety of construction and the stability of rock mass,even leads to major security incidents because of its high destructiveness;therefore,as the basis for preventing rock burst,it is of great significance to make prediction of rock burst.In this paper,based on such main factors affecting rock burst as geological condition,geostress condition,mine layout condition and so on,the lateral pressure coefficient,depth-span ratio,lithology and degree of joint were selected by using FLAC3 D numerical simulation software to analyze the possibility of rock burst in roadway surrounding rock under different conditions to predict the influence degree of these four factors on rock burst,explore the regularity of rock burst,so as to provide theoretical basis for the prevention and control of rock burst in the future.The main contents are as follows:Rectangular tunnel was constructed on the basis of geological conditions in Wuyang Coal Mine of Luan Shanxi,and the maximum principal stress of the tunnel was used for the analysis of model feasibility.Lateral pressure coefficient was chosen as variable,and then modified criterion of rock burst was used as criteria for determining rock burst grade to make predictive study on the rock burst law of rectangular roadway under different lateral pressure coefficients.The results shows that the influence on rock burst regularities of rectangular drift from coefficient of horizontal pressure is: roof plate > bottom plate,the rock burst grade of both roof plate and bottom plate will increase with the increases of coefficient of horizontal pressure;they are positively correlated.It was found that the rock burst grade was minimum when the lateral pressure coefficient of rectangular roadway was 0.5.Depth-span ratio was chosen as the variable to investigate the influence of depth-span ratio on rock burst grade of rectangular tunnel.The result shows that the influence on the rock burst grade of rectangular drift by depth-span ratio,the roof plate is slightly higher than the bottom plate.The rock burst grade of the bottom plate in rectangular drift shows a trend of increase,decrease and increase again with the increase of depth-span ratio.The rock burst grade is at its maximum value when depth-span ratio is 0.5;minimum when 0.75.Lithology was also selected as variable to compare the rock burst grade of rectangular roadway under three kinds of lithology.The results shows that the possibilities of rock burst between different lithologic characters are: granite> limestone> mudstone;and the hardness of surrounding rock is positively correlated with the possibilities of rock bursts occurred on the roof plate.Arched section tunnel was built as well,and the feasibility of the model was verified by the analysis of the maximum principal stress.And degree of joint was used as variable to compare the possible rock burst grades.The results shows that the effect of the degree of jointing on the possibility of rockburst in the surrounding rock of archway is: angle > arch shoulder > vertex > bottom,with the decrease of rock mass,the possible grade of rock burst in roadway surrounding rock will increase gradually.It was verified that the possibility of grade of rock burst in joint place of arch tunnel was greater than that in non joint place when mining rock mass containing transfixion joint,meanwhile,the influence of lateral pressure coefficient on rock burst of jointed rock mass was discussed.Results showed that the grade of rock burst in the vault and floor of the roadway increased with the increase of the pressure coefficient,and the possible rock burst grade in apex of arch was higher than that of floor.It is concluded that,surrounding rock of rectangular roadway had the most stable state and the lowest possible rock burst level under the conditions of 0.5 lateral pressure coefficient,0.75 depth-span ratio and mud stone.Therefore,the arch tunnel should be set in the slight jointed rock mass,and the roof and angular point had large rock burst during excavation,which was more dangerous.Therefore,the rock support of roof plate and corners should be pay more attention in the future mining.