A block model estimate is generated within the study area. This process has been streamlined in Supervisor geostatistical software and is widely practiced in Australia, although published examples are hard to find. An example from a lithium deposit is provided in Figure 1. Figure 1. Mean slope of the regression and number of drillholes with increasing drillhole spacing.
Single Block Kriging Studies:. The single block kriging method considers the production rate, the variogram model and sample co-efficient of variation to assess the variability of grade estimation over various production periods for various drillhole grids.
It is referred to as a single block kriging method because the production volume is represented as a single large block, which may be equivalent to a month or quarter of production.
The authors apply the method described by Verly et al. A kriging estimate is performed in the large block for each drilling grid, and the estimation error stored. The error is assumed to be normally distributed due to the large block size and many samples, which then allows the practitioner to deduce confidence intervals. An example from an open pit gold mine is provided in Figure 2.
Figure 2. Increasing drillhole spacing overlain on a single block representing one month of production. While international reporting codes e. For the Inferred Category, the data are inadequate for assessing confidence intervals. A typical DHSS methodology based on a single block kriging estimate is summarised below:. Model a variogram for the element and area of interest using declustered and capped composites,.
Define dimensions of a large single block equivalent to one month of production,. Set up artificial drilling grids at various spacings no grade variable is necessary to produce errors ,. Run a kriging estimate in the large single block for each artificial drilling grid,.
Scale up results to represent quarterly and yearly volumes,. Plot results and use risk-based Mineral Resource category definitions. The authors are not aware of any commercially available software that has streamlined this process, however, due to its simplicity, it is able to be undertaken in most mining software packages. An example of the method applied to the predictions of tonnes above cut-off grade from an open pit gold mine is provided in Figure 3.
Figure 3. Conditional Simulation Studies:. Conditional simulation based DHS studies take many forms but they are all aimed at quantifying the reduced risk resulting from increased drilling.
While no standardized method exists in the literature, an example approach to DHSS using conditional simulation is summarised below:. Model a normal-score variogram for the element and area of interest,. Complete sequential Gaussian simulation SGS from the exploration drillholes and produce 10 realizations,. The line position further plays the role of breaking the rock and pushing the rock forward.
The comparison of the maximum effective stress at the top observation point of the two spacing parameter indicates that the stress values present a trend of decreasing first and then increasing. The stress peak near the middle of the front holes indicates that the blasting action of the front row of holes sufficiently broke the rock between the two holes, creating a good free surface for the rear row of holes and achieving a good blasting effect.
The maximum stress of the slope observation point of the two spacing parameters arrangement methods increases first and then decreases. Meanwhile, due to the existence of air gap, the rock breaking time is prolonged, and the energy distribution is more even.
It not only will not cause the waste of blasting energy but also will not cause harmful effects, such as flying rocks and excessive vibration. As shown in Figures 12 and 13 , through numerical simulation, the maximum effective stress Different combinations of spacing parameter will have different effects on the blasting effect. According to the maximum effective stress analysis of the simulated results of different section monitoring points and the comparison of the theoretical calculation values, as shown in Figures 14 — 16 , the three sections that meet the rock crushing requirements are selected for the field test.
The air deck charge structure and the large spacing parameter of the hole layout result in insufficient bench explosion energy and easily produce large blocks. During the blasting process, the resistance line at the bottom of the bench is extremely large, and the rock is difficult to break. Thus, high-bench blasting is more likely to produce the foundation than ordinary bench blasting.
At present, the large domestic air deck charge structure and the method of arranging holes with large spacing parameter have not been adopted in noncoal mines. Barun open-pit mine has carried out high-bench blasting tests and achieved significant results, but its use is still difficult to promote in mines.
After improvement, the field test blasting area is designed to use vertical drilling for the m-high bench blasting design. Considering the construction problems and the pressure bearing capacity of the air spacer and overcoming the bottom resistance line, the air spacer is arranged in the middle of the blast hole. The main rock at the site is dolomite, and the other rock composition is relatively small.
The simulation is performed under a single dolomite condition. This is the limitation of the simulation. Although some differences from the site exist, it can represent most of the site conditions and must be verified by experiments. The surface rock on-site is quaternary, with low hardness, small thickness, and uneven distribution, so the impact on blasting can be ignored. According to the existing shovel loading equipment in the mining area, the statistical analysis of the rock mass after blasting shows that the large lump rate in the experimental blasting area is only 0.
The TC blasting monitoring instrument was used to test the vibration of the field test explosion zone, which was compared with the conventional bench blasting vibration Table 5. Analysis indicates that although the single-hole charge of high-bench blasting is greater than that of conventional blasting, the air deck weakens the peak pressure, so the blasting vibration increases slightly, and it meets safety requirements.
This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Article of the Year Award: Outstanding research contributions of , as selected by our Chief Editors. Read the winning articles. Journal overview. Special Issues. Academic Editor: Junfei Zhang. Received 12 Dec Revised 18 Jan Accepted 01 Feb Published 13 Feb Abstract In view of the near slope blasting in Barun open-pit mine, which has merged sublevel mining, the operation safety conditions of middle-sized and large equipment in the second phase expansion are poor and need urgent improvement.
Stress Field Characteristics of Spherical Charge When the charge blast hole is detonated, the explosive will explode to produce high-pressure gas, impacting the wall and propagating a strong pressure wave outward into the rock medium [ 30 ]. Figure 1. Blasting zones partitioned in the rock, indicating the I crush zone, II fracture zone, and III elastic vibration zone.
Table 1. Figure 2. Cylindrical charge as near as possible or equal to the spherical charge. Figure 3. Figure 4. Principle stress of various direction attenuations with time.
Figure 5. Figure 6. Figure 7. Parameters Value 5. Table 2. Table 3. Parameters Dolomite 14 Table 4. Figure 8. Figure 9. Figure Effective stress of the section at the bottom resistance of bench. Effective stress of the section at the slope resistance of bench. Effective stress of the section at the top resistance of bench.
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