Research On Law And Control Technique Of Blast-Induced Rock Movement In Deep-Hole Bench Blasting

During the open-pit bench blasting process,rock mass will be fragmented under the action of explosive energy,both ore and waste fragments move toward the bench face and redistribute,leading to the huge difference between pre-and post-blast ore boundary.At present,the accurate blast-induced rock movement distance and the post-blast ore boundary can only be determined using the field measurement method,but these methods are inaccurate or expensive.As a result,only pre-blast ore boundary can be utilized to design loading plans and guide shovel loading in most open-pit mines,causing serious ore loss and dilution.Therefore,it is of great significance to analyze the law and control technique of blast-induced rock movement in deep-hole bench blasting to reduce the ore loss and dilution in deep-hole surface mining.Aiming at the research on law and ore loss and dilution control of blast-induced rock movement in deep-hole bench blasting,theoretical analysis,numerical simulation,field monitoring,machine learning and field experiment are applied in this study.The obtained blast-induced rock movement law and control technique can provide theoretical basis and technical support for ore loss and dilution control caused by blast-induced rock movement in open-pit mines.The primary work and achievements include the following several aspects:(1)The chemical reaction process of explosives,the interaction process of blast loading and rock,and the process of rock-throwing and accumulation are described.Meanwhile,the expansion of explosive gas was found to be the main reason for rock-throwing velocity.Based on the proposed and validated single-row bench blast model using the equivalent spherical charge theory,and the discrete element simulation study,a multi-row bench blast model which can be utilized to analyze the blat-indued rock movement was proposed.(2)Using the single-row and multi-row bench blast models,the impact of blast parameters on the throwing velocity of rock fragments and mean fracture-rock-mass horizontal movement were studied.The obtained results show that the maximum throwing velocity and mean fracture-rock-mass horizontal movement increase with the increasing bench height and borehole diameter,and the decreasing burden and stemming length.(3)According to the blast-induced rock movement datasets from Husab Uranium Mine trial blast and previous literature,the impact of many factors on blast-induced rock movement was obtained using a multi-factor influence study,and the accumulation characteristics of rock strips were also obtained using discrete element simulation.A fold-back stacking phenomenon was found in most of the rock strips.The movement direction is usually perpendicular to the isochron.Blast-induced rock movement distance first increases and then decreases with the depth.Meanwhile,a positive relationship between blast-induce rock movement distance and depth height and powder factor,a negative relationship between blast-induced rock movement distance and rock strength,single-hole bearing area,drilled burden and characteristic burden of rock fragments,and no obvious relationship between blast-induced rock movement distance and surface conditions were found.(4)Considering that the accurate blast-induced rock movement distance of rock fragments can only be determined using field measurement technique,machine learning method was introduced to the study of blast-induced rock movement,and a novel method based on supervised learning method was proposed.High-speed and high-precision prediction of blast-induced rock movement distance can be achieved by developing three original supervised learning models and six novel supervised learning models.After evaluating the model performance,WOA-GP was found to be more accurate than other models.(5)Two post-blat ore boundary determination methods were proposed by combining the Monte Carlo method and geological modeling theory.Compared with guiding shovel loading using pre-blast ore boundary,serious ore loss and dilution can be avoided using the post-blast ore boundary obtained by the proposed post-blast ore boundary determination method.Then,a post-blast ore boundary prediction system with the function of model performance comparison,blast-induced rock movement prediction model development and post-blast ore boundary determination was developed.(6)For the blast block with different ore body complexity,four blast-induced rock movement controlling ideas including “Separately divide the blast block to achieve independent fragmentation of rock and waste”,“Control the movement direction to reduce the mixing of ore and waste fragments”,“Optimize the blast parameter to reduce blast-induced rock movement distance” and “Reduce the movement space to weak the blast-induced rock movement”.Based on the latter three ideas,a divided open-pit blast technique,a large-burden blast technique and an in-situ blast technique were proposed after theoretical analysis and numerical simulation.Then these techniques have been successfully verified through field tests in Husab Uranium Mine,Namibia,and an open-pit mine in Baicheng,China.This paper contains 159 figures,14 tables and 278 references.