区分
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甲
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氏 名
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Ganda Marihot SIMANGUNSONG
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| 論
文
題名 |
Experimental study of ground
vibration induced by blasting in mine and quarry |
| (鉱山における発破振動に関する実験的研究) |
| This dissertation is a
condensation of research related with vibration induced by blasting.
The first research proposes a method of identification blast induced
rock mass damage using combination of vibration monitor and borehole
camera. Application of the method was performed in coal mine. Blast
vibration and attenuation within a rock mass adjacent to blast holes
were monitored. A borehole camera was applied to observe rock mass
damage, and worked properly to quantitatively count a number of cracks.
Comparison between the near field vibration monitoring and rock mass
damage measurement revealed that cracks grow proportionally with peak
particle velocity (PPV). The relationship is given by PPV=114 e
0.0015p. The PPV is specified in order of mm/s. p is defined as ratio
of crack density increase in percent. |
The second research was mainly performed to check whether or not the blast burden influence vibration magnitude. This is associated with the necessity to reconsider blasting design in order to reduce vibration to the acceptable levels. Blast vibration monitoring of three scenarios of burden were managed in limestone quarry. The vibration monitoring results are found in good agreement with what had been found by other researchers in terms of duration, amplitude, and frequency. Vibration waveforms typically last for 50 to 100 milliseconds. The peak amplitudes decrease according to additional distance. Frequencies decrease with increasing distance. The weight scaling law between the PPV and scaled distance revealed three relationships for three different scenarios of burden, which obviously indicate that blast burden influences vibration magnitude. The highest vibration magnitudes are produced by the biggest blast burden. Otherwise the lowest levels of vibration magnitude are produced by the smallest blast burden. Parallel with the main idea, which were mainly performed to check the influence of the blast burden to vibration magnitude, investigation was extended to measure fragmentation of the blasted rocks. Fragmentation measurement was achieved using the analysis of scaled photograph taken form a muckpile. Using software known as Split Engineering, the blasted rocks resulted from three scenarios of blast burden were simply calculated and presented in size distribution curve. The average fragment size (K50; mm) increases exponentially with increasing blast burden (B; m) that can be expressed by K50=0.536B4.227. |
Following the result of the previous research that vibration seemingly can be related with fragmentation, a case study was performed to support the result. Eight production blastings were investigated in terms of vibration and fragmentation in limestone quarry. Vibration monitoring revealed that three blasting operations produced higher vibration magnitudes at any given scaled distances compared to the other blasting operations. In terms of fragmentation, the three blasting operations, of those produced high vibration magnitudes, surprisingly resulted in bigger fragments compared to the other blasting operations. With a view to correlating vibration and fragmentation induced by blasting, a case study reveals condition that big fragments indicate relatively high vibration magnitudes. Otherwise, small fragments indicate relatively low vibration magnitudes. |
Two dimensional FEM analysis by ANSYS, based on the data of vibration monitoring, was performed to estimate the distribution of the PPV around the blasting source. Back analysis of vibration wave for modeling the explosive source using trial and error simulation has found the most suitable relationship between the time and pressure applied within the model that follows P(t)=0.62[exp(-100t)-exp(-500t)], where P is specified in order of MPa and t is in second unit. The suitable relationship is indicated by similar shape of computed vibration waveforms with the actual vibration waveforms. Duration of computed waveforms, which is found less than 100 milliseconds, agrees with the finding of the vibration monitoring. The simulation reproduces the PPV of vertical component which are in good agreement with the vibration monitoring results. The computed PPV of horizontal component do not correspond with the monitoring results, though the gradual decrease of PPV according to the increase of distance from blasting source are identified similar. The simulation process has given possibility of improving the way of prediction PPV, from the classic weight scaling law to the so-called computer modeling. |