| The large rare earth polymetallic open-pit mine used a small mining boundary initially and temporarily leaned the upper step on the side,then the temporary boundary slope was formed as multiple groups and section leans and large vertical height.Moreover,due to the steep temporary slope,narrow expanding platform,the safety of large equipment under severe environments and a large amount of auxiliary engineering conventional step sequence expanding road as well as the low efficiency of expanding,the mining operation of expanding boundary faced several engineering matters in the last stage.Thus,this article is based on the engineering problem of Bayun Ebo Mine innovatively put forward the "altering two to one" mining method.In addition,due to the air deck charging hole explosion load transmission mechanism and air deck charging rock broken pattern being unclear and the uncertainty of key technical parameters,according to the deep hole basting "inside to out" process,we developed a novel technology of high step deep hole blasting for metal open-pit mine based on the theoretical analysis,numerical simulation,and a series of experiments,such as original rock model experiment and field industrial experiment.The main research contents and conclusions are as follows:(1)A universal quantitative analysis method for the position of air deck charge was established.The air deck rod parameter was proposed to characterize the location of air interval,and the proportional parameter of air interval length was introduced to quantify the length and location of arbitrary air interval by two key parameters.The flow characteristics of cavity implosion product under different air interval charge lengths and positions were analyzed.The temporal and spatial distribution relation of detonation pressure variation is derived.The propagation characteristics of air interval charge to the spatiotemporal distribution of pressure change in the hole were quantitatively analyzed.(2)The interaction between explosive detonation and air in the hole,the flow characteristics of detonation gas and the characteristics of rock fragmentation in the near area are revealed.The PBM-SPH-FEM coupling method was used to analyze and find that the pore wall pressure in the charging section of the air-spaced structure was significantly lower than that in the full-hole continuous charging.Compared with the full-column charging,with the detonation wave propagation,the detonation pressure at the distance of 2.5～3.0 times aperture from the air section began to decrease.It corrects the cognition that the air interval charge structure only affects the pressure of the air interval.(3)It is found that the detonation pressure of the upper and lower cylinders in the middle air interval charge has bimodal characteristics.Compared with the full charge column,the peak pressure of the lower charge column is basically unchanged,and the pressure of the upper charge column is significantly reduced due to the influence of sparse reflection waves in the air interval.Under the influence of the air space structure in the middle,the pressure boost process of the upper and lower charging columns showed a double peak jump trend,but the maximum peak pressure of the upper charging column decreased significantly,and the peak pressure of the air space section was only 43.8%of that of the lower charging column,and the peak pressure of the lower charging column was only 28%.The total jump time to peak pressure of the upper column is 2.07 times that of the lower column.The step pressure time of the lower charge column is 3.6 times of that of the normal charge,and the time of detonation gas loading in the hole is increased by 65.3%.(4)The characteristics of rock breakage in the near area of deep hole air interval charge blasting are studied.The rock breaking in the near area of deep hole air spaced charge blasting is studied by the method of model test,CT scanning technology and numerical simulation calculation.The rock failure form of spaced charge structure blasting is explored through the fractal dimension of rock breaking characteristics in the near area of blasting and the calculation of rock breaking damage degree and the analysis of variation characteristics of variation coefficient.Analysis of the test results shows that the top air deck charging structure is more suitable for high step front hole blasting,and the middle air deck charging structure is more suitable for high step back hole blasting.(5)The optimal standard of air deck charge structure of 24 m high step vertical deep hole precision blasting is established.The slope top of the front vertical deep hole step has a small resistance line,and 27%～36%of the air deck length is suitable to adopt the top air deck charging structure.The reduced detonation pressure is far higher than the ultimate strength of rock mass,and significantly increased rock breaking action time better meets the needs of rock breaking.When other blasting parameters are unchanged,the size of the interval ratio parameter is related to the properties of rock,and the interval rod parameter has a decisive influence on the energy evolution of explosive detonation gas in the process of blasting rock breaking.The resistance line of step blasting is small,the required energy of rock crushing is small,and the interval rod parameter can be selected with a large value.For high-step vertical deep-hole blasting,the interval rod parameter value is generally 0.36 to 0.73.(6)The blasting technology of long air deck charge with high step and high density coefficient is studied and popularized.Compared with the damage cloud image of different sections of the numerical simulation step with large density coefficient,the front hole adopts the top air deck charging structure to effectively balance the pressure in the hole and prolong the rock breaking action time of detonation gas.The rock mass equivalent stress at the top of the step of the central air deck charging structure is greater than the ultimate strength of the rock mass,which can effectively break the rock mass.On two rows of three deep Kong Wei delay blasting hole blasting cloud computing results effective stress analysis,also shows that using the back hole central air deck structure,are critical steps side slope rock mass stress value is bigger,show that the first salvo holes at the top of the air deck charge structure is reasonable,the back hole central air deck charge structure should be adopted.In the field test,the photogrammetric measurement showed that the rate of rock breakage was only 0.82%,and the bad blasting phenomena such as no rock wall and foundation were tracked.In the later period,the large scale field application of high step,deep hole,large density coefficient,long air deck charging blasting was carried out in Bayan Obo Mine,and good blasting effect was achieved. |
PDF Full Text Request