Damage Characteristics On Shaft Wall Under Impact In The Adit-ore Pass System Of Open-pit Mine

In the adit-ore pass system of an open pit mine,the ore coming from the chute will flow into the ore pass and severely damage the shaft wall.Traditional protection have high cost and short service life.It is important to determine the damage characteristics and choose the right protective method to solve the wall damage problem.In order to explore the ore motion law,study the wall damage characteristic,and improve the wall protection furtherly,the field investigation,laboratory test,theoretical analysis and numerical simulation are carried out in this work by taking an open-pit mine as a background.This work could be summarized as follows:(1)Firstly,the motion model of single ore is established according to the kinematic theory.The influences of critical parameters on the initial collision position are analyzed.Based on the pseudo-random algorithm,the motion of ore in ore pass is determined.The sliding-rolling coefficient of friction is the principle factor to determine the initial collision position.The critical coefficient has little effect on the initial collision position.With the increased normal coefficient of restitution and sliding-rolling coefficient of friction,the distance between the initial collision position and the wellhead of shaft will be enlarged.In addition,the initial collision position gets further away from the wellhead of shaft when the tangential coefficient of restitution and critical coefficient decrease.The distribution of the initial collision position in the collision area is exponentially distributed.The shaft wall in the range of 4~8 m from wellhead needs to be well protected.(2)Secondly,based on the erosion-wearing theory,the calculation model of the damage caused by single ore impact on ore pass wall is established and the method to calculate the volume loss is determined using Hertz contact theory,and the results are consistent with the actual situation.The ore will fall into the storage after three times collisions with ore pass wall.The impact area of the upper ore pass wall is small,but the damage is serious.On the contrary,the impact area of the lower ore pass wall is large,but the damage is insignificant.(3)Besides,in order to take the influence of ore interaction into consideration,a numerical model of sveral ores is built to analyze the motion of ore by using PFC2 D software.Taking the momentum as an indicator,the damage characteristics are studied.The depositional shape of ore evolves into a steady stream at first due to the the interactions between ores.The initial collision position is relatively fixed,but the later movement of ore is complicated due to the interactions between ore.The initial collision position is located at the right side of shaft wall in the range of 0~5 m from wellhead.This area needs to be well protected for its serious damage.The damage of other parts of the shaft wall are relatively small.(4)At last,according to the motion of ore in ore pass and the damage characteristic of shaft wall,a buffering method is proposed to protect the wall based on flexible protection theory.Moreover,the effect of buffer layer is analyzed by using numerical simulation.The buffer layer can effectively reduce the initial impact damage and subsequent impact times on the shaft wall.High grading level of buffering ore will reduce the protection of bottom,and low grading level of buffering ore will reduce the protection of bevel.