Research on the shaping control of frozen wall and blasting vibration mitigation of shaft wall effect in mine vertical shaft

The disturbance and destruction of frozen pipe,frozen wall and shaft wall by blasting is an important control point in the construction of mine shaft. In Wan-fu Mine shaft project,a smoothing and slotted cartridge blasting in pe- ripheral holes was conducted. Through multi-fractal theory,the multi-fractal spectrum parameters of frozen wall three dimensional image were extracted under three conditions. Using frequency slicing wavelet,different frequency band sig- nal reconstruction was achieved under three schemes. Through the wavelet packet algorithm,the vibration of the shaft wall was monitored,and the energy distribution of the corresponding signal band was obtained. The results show that the multi-fractal spectrum can be used to evaluate the protective effect of the slotted cartridge on the frozen wall. The blasting vibration frequency of shaft wall is higher than ground one,usually about 150 Hz. With the increase of fre- quency,the amplitude and energy of vibration signal decrease. In the low frequency range (0 ~ 250 Hz),compared with the smoothing blasting of the peripheral holes, the energy of the half-circle slotted cartridge was reduced by 41． 54% and in the whole circle it was reduced by 52. 42% . In the low frequency band,slotted cartridge has a signifi- cant “energy absorption” effect. In the middle frequency band (300 ~ 500 Hz),due to half-circle slotted cartridge en- ergy release is not balanced and shaft wall structure is non-strict symmetry,the characteristic frequency band has an energy “selective amplification” effect. In the high frequency range (700 ~ 900 Hz),the “ regional concentration” phenomenon of energy reflects that the mitigation of vibration is more close to the blasting area. The frozen wall protec- tion and shaft wall vibration mitigation of slotted cartridge is verified.