| With the large-scale application of electronic detonators,the intelligent blasting technology of rock roadway has entered a new stage,but the optimization and selection of millisecond time of rock roadway excavation blasting is still an urgent problem to be solved.Based on the previous research results and related blasting theory,this paper optimizes the theoretical calculation formula of the millisecond time between the cutting hole and the auxiliary hole of the straight-hole cutting blasting,and studies the formation process and characteristics of the cavity under different delay conditions by using the model experiment of the electronic detonator.Then the research results are applied to the rock roadway excavation blasting site,and the feasibility and practicability of the research results are tested.At the same time,the delay time setting of the engineering site is optimized to improve the tunneling efficiency.According to the optimized theoretical formula,the optimal delay time of the model experiment is calculated.Based on this,seven groups of experimental schemes are designed,which are 0ms,1ms,3ms,5ms,7ms,9ms delay time and only cutting hole initiation time.Super dynamic strain gauge was used to monitor the internal strain change process of the cavity when only the cut hole was detonated.At the same time,the cavity formation process of the experimental model was observed by high-speed camera,and the cavity volume,cavity depth and rock fragmentation after blasting were measured and analyzed to explore the cavity formation characteristics and differences under different delay conditions.The finite element analysis software ANSYS/LS-DYNA was used to numerically simulate the model experiment scheme with the best cutting effect.The crack propagation process of the cavity and the variation law of particle pressure and velocity in the simulation were analyzed,and the cavity formation rules and differences under different delay time were summarized,which were mutually verified with the model experiment results.The periodic results obtained were verified by field experiments,and the following research results were obtained :(1)The three-dimensional stress intensity of any point in the rock is expressed by Miss criterion,and the theoretical calculation formula of the millisecond time between the cutting hole and the auxiliary hole in the straight-hole cutting blasting is optimized.The practicability of the theoretical formula is verified by model experiments and field experiments,which provides theoretical guidance for the selection of the on-site delay time of rock roadway excavation blasting.(2)The superimposed stress wave intensity generated by the initiation of adjacent cutting holes will experience a process of first increase and then decrease.The compressive failure of rock medium is the strongest at the maximum stress wave superposition intensity,which provides a theoretical basis for the optimal distance between the cutting hole and the auxiliary hole.(3)According to the theoretical calculation formula of differential time,the optimal delay time between the cutting hole and the auxiliary hole in the model experiment and the field experiment is 1.1ms and 15 ms,respectively.The optimal delay time range of the cutting effect in the model experiment and the field experiment is 1ms～3ms and 15ms～30ms,respectively.The feasibility and practicability of the theoretical calculation formula of differential time are verified.At the same time,the selection of the cutting delay time in the engineering field is optimized and the tunneling efficiency is improved.(4)The numerical simulation results provide favorable support for the analysis of the internal crack propagation law in the cutting cavity.At the same time,the influence of different delay time on the cutting blasting effect is intuitively shown,and the selection of model experiment and engineering site millisecond time provides important guidance.Figure [40] Table [17] Reference [78]... |
