Gravity Flow Of Broken Rocks And The Control Of Rock Blasting In Mining Narrow Steeply Dipping Veins

In the heavy demand for energy and resources with the rapid development of national economy,the exploitation on deep-seated,residual and complicatecd ore bodies is being carried forward.Dipping narrow veins take a great proportion in gold and nonferrous mines in our country,nevertheless,because of their specific occurrence,leading to a series of technical problems during the mining process,such as the large blast clamping force,the difficulties in ore loss and dilution control,the excess of working circulations,the low level of mechanization and operation efficiency and the poor safety.Although a safer and more efficient mining method which applied medium-length hole blasting technique has been experimented in dipping narrow veins,none large-scale popularization and application is carried out nowadays due to the restriction of mining width which has a negative impact on blasting effect on account of the large blast clamping force,moreover,ore loss and dilution could be increased owing to the unstability of orebody and surrounding,rock.Consequently,there is crucial significance in resolving blast clampin force problem and controlling ore loss and dilution cduring mining process to promote the application of mecdium-length hole blasting in dipping narrow veins.On the engineering background of cdippincg narrow and fractured orebody in Jingchanggouliang gold mine,a stopingy scheme of non-pillar sublevel caving mining method was put forward based on the ground pressure managerment which filling the mined area with caved rock,the medium-length hole blast"ing technique and continuous mining.Aiming at the loss and dilution control of caving method and blast clamping force problem in dipping narrow veins,laboratory similar material experiments.3DEC numerical simulation,granular flow numerical simulation,SOM data mining and in-situ test were applied.The specific research are as follows:(1)On the base of 3EDC program,the principle of stress migration of dipping narrow and fractured veins during mining process were analyzed,the characteristics of pressure distribution by different stoping method was researched,provided theoretical support on stoping scheme and structure parameter selection of the stope from the perspective on pressure control.(2)To carry out the similar material test of drawing body and measure the development process and morphological characteristics under the condition of inclined boundary wall,the influence on moving principle of granule by the thickness of the orebody and wall roughness was analyzed,the conceptual model and range of granular flow under the condition of inclined boundary wall was discussed and the quantitative characterization of the size of drawing body was realized.(3)Calibration method of discrete element mesoscopic parameters was realized,which based on SOM algorithm combined with a large number of numerical experiments;and the numerical experiment of side drawing with PFC3D was carried out as Well,the numerical simulation method of drawing body and the calibration method of mesoscopic parameters based on discrete element were both verifGed to be reliable;the PFC1C numerical simulation experiment of single drawing hole under the condition of inclined boundary wall was carried out,the distribution characteristics and transformation principle of displacement field,velocity field and contact force field were analyzed in the process of ore drawing,consequently,the flow mechanism of loose ore-rock body under the condition of inclined boundary wall was revealed from the perspective on mechanics.(4)To carry out the physical simulation experiment of structural parameters of sublevel caving,in this paper,the influence on ore dilution and loss index by sublevel height,drawing space and cutoff grade was analyzed,while with the SOM algorithm,the physical simulation experiment data was clustering analyzed as well,and on the basis of this,a neural network prediction model was established,which was about the stope structure parameters and the index of ore loss and dilution so as to realize the optimization of stope structure parameters.(5)Considered the combined action of blasting stress waves and detonation gas during blasting process,discrete element numerical simulation method of blast in rock mass was established based on LS-DYNA and PFC program,then the numerical experimentation of single column charge under the impact of blast loading during the blasting process was carried out.Furthermore,the effect on blast clamping force by mining width and burden was analyzed ancd the parameters of medium-length hole blasting in narrow veins were optimized,namely,the effect on blasting impact by burden and spacing was analyzed taken both over and under excavation and the size fraction of blasting fragment as evaluation indexes,accordingly,blasting parameters of dipping narrow veins were optimized in Jinchanggoulaing gold mine and the parameters were applied in industrial field test.The field blasting effect was evaluated and verified comprehensively by means of CMS 3D laser scanning eventually.(6)The optimized results were applied to No.711 orebody,7#level,6#mining area in Jinchanggoulaing gold mine,and the mined area after blasting was quantitatively evaluated elaborately with CMS 3D laser scanning,realized the evaluation of blasting effect and verified the accuracy of blasting parameters.