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The optimization of delay time is very important for controlling blasting vibrations and guaranteeing the technical-economic effect of blasting projects. The proposed improved linear superposition method can be used to in-depth discover the relationship between the particle peak velocity (PPV) of blasting vibration and delay time. Because blast vibrations actually belong to random process, which means merely using a one-time measured single-hole blasting vibration signal to simulate a multi-hole blast vibration waveform may not be reasonable. Similarly, it is also not enough to simulate a multi-hole blast vibration waveform corresponding to a certain delay time only once. A method involving random variables and statistical treatments is necessary. Firstly, Fourier series is used to represent a measured single-hole blast vibration waveform. This is necessary to formulize a piece of measured time-series data. Secondly, random variables are added to the coefficients and phases of the Fourier series expansion to generate a specified number of single-hole blasting vibration waveforms. Thirdly, Monte Carlo simulation is used to calculate the mean value of PPVs corresponding to each delay time between 0ms and 250 ms with an increment of 1 ms, and the change curve of the average PPV with delay time can be obtained. The results of example analysis show that if the civil house 531 m away from the explosion source is taken as the protection target and 0.45 cm/s is taken as the peak particle velocity control threshold, any delay time more than 7 ms can be selected to meet the safety standard, and when the delay time increases, the PPV decreases in general. To pick a specific delay time from the range determined by the above process, it is necessary to observe the relationship between the rock fragmentation effect and delay times. By investigating the fragmentation results of four blast tests, the total amount of boulder yield decreases first and then increases with the delay time per meter, and the minimum value appears when the delay time is 7 ms/m. That is, if the designed hole spacing is 6 m, and hole-by-hole initiation is adopted, the optimal delay time in terms of rock fragmentation is about 40ms. This delay time just falls into the range larger than 7 ms determined previous by the improved linear superposition method. Therefore, by comprehensively considering both the results of Monte Calo simulation of blasting vibration and the rock fragmentation tests, the optimal delay time of the mine can be finally selected as 40 ms.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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