Study On Rockburst Control By Destress Blasting Technique In Deep Underground Stressed Metal Mine

This thesis deals with the topic of rock burst control by destress blasting technique in deep underground metal mine.As previously researched,the mineral deposits are very important valuable materials strengthening the economic development of a nation.The unlimited needs of human being from mineral deposits are leading to the continuous increase in depth of underground mines.Along with the exploitation of deep resources and the subsequent high concentration of ground stresses,the frequent rock bursts occurrence increases consequently,which strongly hinder the safe and economic recovery of deep-seated mineral resources.Due to the fact that,the greater mining depth is probably followed by the occurrence of rock bursts problem,therefore,the application of destress blasting is recently growing as a deep mine safety tool.The other researchers have been found that after the prediction of rock burst tendency,the right decision can be made on how to destress the zone with high stresses concentration.In this regard,the principle of stress transfer can be used through the application of destress blasting technique.In order to realize the safe and efficient mining of deep resources in Gaofeng mine,this study has preliminarily reviewed both rock burst and destress blasting technique,and then apply the criteria for rock burst tendency evaluation to evaluate the rock burst tendency,which was based on by selecting the suitable mining method and proposing the destressing schemes.For rock burst,the review was conducted for a thorough understanding of rock burst disasters to arouse the Authors'great deal of interest to go through a detailed research on rock burst disasters in deep underground mine.From the deep review on destress blasting technique,a certain understanding and the ideas for further improvement of its field application are gained.By focusing on mine case study,a deep orebody No.105 in Gaofeng mine is taken as the research case study in this master thesis.The tendency of rock burst is mainly evaluated based on the geological conditions,in-situ stresses and rock mechanical parameters that have been preliminarily mastered in the mining area.According to the in-situ stress and rock mechanical parameters measured in the mining area,the rock burst tendency is evaluated with the 5 rock burst tendency evaluation criteria such as Barton criterion(?_t/?₁),Barton criterion(?_c/?₁),Maximum stored elastic strain energy index(?_vc²/2E),Elastic energy index(Wet),Brittleness criterion(?_c/?_t),and Impact energy index.Based on the analysis of evaluation results of rock burst tendency for No.105 tin ore body in Gaofeng mine,it is concluded that the orebody fulfills the rock burst tendency conditions.In order to limit the mining technical problems,and realize the safe and efficient mining of this orebody,this thesis studies the destress blasting schemes for No.105 orebody to prevent the rock burst problems that may occur during the mining process.In order to analyze and select the effective destressing schemes to be applied,the simulation software such as ABAQUS,Pro/E,and Hyper Mesh14.0 are used to simulate the proposed destress blasting schemes.Based on the mining technical conditions,in-situ stresses,the general trend of the ore body,and rock mechanical parameters,the influences of different depths of destress blastholes on destressing effect are particularly analyzed first.The analyzed different blasthole depths conditions are when blasthole depth is 6m,8m and 10m respectively.During the simulation of blasthole depths of 6 m,8 m and 10 m,the destress blasting is carried out in front wall of the mining face.For these three blasthole depths conditions,the charge length is 1m and the stemming length is 5m,7m and 9m respectively.Among these 3 blasthole depths,the destressing effect is obvious when the blasthole depth is 6m.This is mainly due to the fact that,after the destress blasting,the high stress in surrounding rocks of face's front wall is transferred ahead of working face.Under the condition that the optimal destress blasthole depth is 6m,therefore the 4 destress blasting schemes(DBS)are proposed to be analyzed and compared with 1 non destress blasting face(NDBF).The 4 proposed destress blasting schemes are such as:Face destress blasting in two sidewalls rocks(DBS ?),Face destress blasting in front wall rocks(DBS ?),Face destress blasting in overburden strata(DBS ?),and the simultaneous destress blasting in face's sidewalls and front wall rocks(DBS ?).Based on the simulation results,the following conclusions are drawn:1.Face destress blasting in overburden strata(DBS ?):This scheme transfers the high stress in vertical direction,but in along the direction of orebody strike,the high stress concentration is not transferred,therefore,the destressing effect is not obvious.2.Face destress blasting in sidewalls rocks(DBS ?):In this scheme,the high stress concentration is transferred to faraway from the surrounding rock masses of face's sidewalls,however the stresses acting on face's front wall rocks are not shifted.This indicates that the high stresses concentration of all surrounding rocks of face are not shifted effectively,therefore,the destressing effect is not very obvious.3.Face destress blasting in front wall rocks(DBS ?):In this scheme,after the destress blasting,the high stress in surrounding rocks of face's front wall is transferred ahead of working face,however the stresses acting on surrounding rocks of face's sidewalls may induce face bursting.Therefore,this scheme has a little destressing effect on the working face of the stope.4.The simultaneous face destress blasting in sidewalls and front wall rocks(DBS ?):This scheme is a combination of scheme ?(DBS ?) and scheme ?(DBS ?).It has the obvious destressing effect on the working face.After the destress blasting,on one hand,the high stress is transferred by DBS ? to deep(ahead of working face),and on the other hand,the high stress is transferred by DBS ?,to faraway from the surrounding rock masses of face's sidewalls.DBS ? transfers the high stresses to far away from all surrounding rocks(sidewalls and front wall)of the stope's face,which reduces the probability of rock burst occurrence in mining face and creates the good conditions for safe mining.Therefore,(DBS ?) is the optimal scheme recommended to be applied.