| At present,deep hole blasting has been widely applied to underground mining,sometimes there are some adverse conditions such as high explosive consumption,high blasting block rate,large blasting vibration effect and so on.In order to guarantee the safety and efficiency of mining,it is important to optimize the blasting parameters and adopt some safety measures.The project which is named "Research on blasting engineering technology of new type deep hole drilling equipment in Taibai Gold Mine" is finished.Through the completion of the project,the parameters of deep hole blasting in Taibai Gold Mine are optimized and the corresponding safety control measures are proposed by rock mechanics parameter experiment and field blasting vibration measurement and numerical simulation analysis and so on.The main contents are as follow:(1)The rock samples of 1100-1200 m level in Taibai Gold Mine were collected to conduct rock mechanics experiments,and geological survey based on RMR method was carried out.The results showed that the grade of surrounding rock was Grade II and the quality of rock was good.Finally the mechanical parameters of rock mass is obtained with the help of the generalized HoekBrown criterion.(2)According to the principle of blasting vibration measurement and the situation of engineering,the 90 mm and 70 mm deep hole blasting vibration testing scheme was formulated,the signal information such as amplitude and main frequency were obtained by spectrum analysis.the blasting vibration attenuation law was obtained by the Sadolfsky formula.(3)The wavelet and EEMD method were used to decompose blasting signal,and the main energy frequency band of the signal is determined by the wavelet energy spectrum coefficient and EEMD energy entropy.The main energy frequency band of the 70 mm deep hole blasting was35.9～234.3 Hz,and the main energy frequency band of the 90 mm deep hole blasting was 16～256Hz.The results showed that 70 mm deep hole blasting was safer than 90 mm deep hole blasting by safety assessment.It is necessary to conduct numerical simulation to analysis the stability of roadways because blasting vibration may damage mining entrances and adjacent haulage roadways.(4)The stability of mining entrances and adjacent entrances and haulage roadways and the effect of the safety control measures were simulated by FLAC3 D.First,the roadways excavation process was simulated,the results showed the roadway junction area was easier to damage and the phenomenon of falling,slabs and bottom heaves may happen in the roadways.Secondly,the application of blasting load was simulated,the results showed that the damage of mining entrances was mainly concentrated on the bottom and two sides of the roadway and some minor shear failures happened in the roof and two sides and bottom of the haulage roadway and adjacent entrances.Finally,mine roadways support was simulated,the results showed that the displacement and speed of the roofs of adjacent entrances were controlled and support effectiveness was proved satisfying,the safety control measures are feasible.(5)The blasting parameters were optimized.According to the blasting effect and empirical formula,the blasting density coefficient of 70 mm deep hole was 2.0～2.6,and the blasting density coefficient of 90 mm deep hole was 1.6～2.0.The blasting vibration attenuation formula was used to calculate the maximum single-stage charge at different blasting center distances.The results showed when the blasting center distance is 0～15 m,the maximum blasting single-stage charge can’t exceed 769.65 kg,when the blasting center distance is 15～30 m,the maximum single-stage charge can’t exceed 6157.21 kg.The wavelet time energy density method and signal superposition analysis and blasting blocks surveys were used to determine the millisecond time of 70 mm deep hole blasting,the results showed the optimal millisecond time was 35 ms.(6)Combined with the previous research results,the safety control measures of Taibai Gold Mine were proposed.Firstly,the shotcrete and anchor support and borehole pressure relief were used to avoid the situation of falling,slabs and bottom heaves of roadways.Secondly,the explosive charge was reasonable controlled according to projects.Thirdly,the millisecond blasting time was reasonable determined,and inter-hole millisecond blasting time is designed to respond special engineering situations.Finally,the charging structure was changed such as un-coupled charging,hole-bottom blasting,charge management. |
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