| The most widely used in tunnel blasting is wedge-shaped undercutting structure.However,in the current tunnel engineering blasting,the choice of wedge-shaped undercutting parameters is mostly based on experience and engineering analogy.It is often difficult to achieve good cutting effects and reduce tunnelling blasting effectiveness.The Grade III surrounding rock section of Hongtuzhang tunnel project is taken as the research object in This paper,the statistical analysis of the blasting vibration test data on site,and the use of Sadowsky nonlinear regression formula to describe the attenuation law of vibration intensity during tunnel blasting,It is found that the surrounding rock generates the most vibration when the cutout blasts.It is shown that controlling the vibration intensity generated by the blasting eye blasting is the key to reducing the blasting vibration damage,and the amount of medicine in the auxiliary eye and the surrounding eye can be greater than that of the pitting eye.The theoretical analysis method is used to study the stress field distribution law between the two cutout eyelets based on the theory of explosive stress waves.The wedge cutout optimization scheme is analyzed from the layout of the wedge cutout holes and the blasting parameters.The above proposed a differential blasting technique for tunnel wedge-shaped notch holes that can reasonably cycle footage and ensure effective vibration reduction.Combined with the theory of differential blasting,the formation mechanism and vibration reduction mechanism of the cavity in this technology were studied.The finite element software ANSYS / LS-DYNA was used to simulate the differential blasting process in the hole,and the depth of the outer and inner cutouts of the notch eye,the charge of the inner and outer charge sections,and the time between initiation of the section and other key parameters on the effect of micro-blasting in the wedge-shaped notch hole and the magnitude of vibration.Finally,the research results of this paper are applied to the on-site blasting test of Hongtuzhang Ttunnel,and the single-shot footage and the peak value of vibration speed are statistically analyzed during each test blasting.The analysis results show that using the intra-hole differential blasting technology can increase the tunneling construction efficiency by about 13% without increasing the difficulty of construction,and the horizontal radial,horizontal tangential and vertical vibration reduction efficiency of the initial support of the tunnel reached 40.7%,28.8% and 34.7% at the same moment. |
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