| Drilling and blasting method is a commonly used excavation method for rock slopes,and the effect of smooth blasting has a significant impact on the excavation quality.The conventional blasting method has problems such as uneven excavation cross-section,low blasting efficiency,severe overbreak and underexcavation,and the harm of stone throwing.In order to solve this kind of problem,it is proposed to use the energy concentration effect of the slotted blast hole to control the smooth blasting effect during excavation blasting,and at the same time adjust the thickness of the reserved smooth blasting layer to change the law of stress wave propagation so as to realize the optimization of smooth blasting and improve the excavation efficiency.This article adopts a combination of theoretical analysis,numerical simulation,and indoor experiments to conduct research.Taking the 339 province road cutting slope as an example,it simulates the impact of reserved smooth blasting layer based on slot holes on the blasting effect of the slope.Through the research in this article,the conclusions and main work contents are as follows:Through the research in this thesis,the conclusions and main work contents are as follows:(1)Using ANSYS/LS-DYNA software,establish two-dimensional models of slotted holes and conventional circular holes under different algorithm models,and analyze the dynamic response differences of slotted holes based on the crack morphology and hole wall pressure after blasting.Through verification of different calculation methods and theoretical values,it was found that the stress in the groove is mainly concentrated at the groove,and the hole wall pressure at the groove is 20.85% higher than that at the non groove,with a peak value appearing 30% earlier;Meanwhile,compared to the theoretical calculated pressure values,the SPH algorithm results are smaller,while the ALE algorithm results are larger but closer.Both are suitable for large deformation problems such as blasting and impact.The ALE algorithm has a more comprehensive foundation,while the SPH algorithm can demonstrate the process of blasting occurrence.(3)Using PMMA specimens for blasting tests,it was found that the crack direction of the groove hole was concentrated at the groove,and the crack was 1.3cm longer than the circular hole crack;Within the experimental range,double hole blasting will weaken the penetration effect of cracks between holes as the spacing between holes increases,and also reduce the overall crack length as the thickness of the smooth blasting layer increases.The density coefficient of the blasting holes is maintained between 0.71 and 1.4,indicating a good blasting crack effect.(2)The study on the effect of uncoupled charging of slot holes on blasting effectiveness shows that as the uncoupling coefficient increases,the efficiency of slot blasting first increases and then decreases;When the uncoupling coefficient K is between 1.5 and 2.5,the blasting damage control and crack quality are good.Comparing the simulation results of double hole blasting,it is shown that slot holes can suppress the number of cracks in the non slot direction and improve the quality of cracks in the slot direction.In the same situation,the effective crack initiation distance of slot holes is increased by 14% compared to conventional circular holes.Based on the optimized spacing of slot holes,blasting simulations were conducted with different thicknesses of smooth blasting layers.The analysis showed that the thicker the smooth blasting layer within the calculation range,the worse the blasting quality.The thickness of the smooth blasting layer is between 60 cm and 70 cm,and the density coefficient of the borehole is maintained between 0.93 and 1.08.The practical and economic benefits of blasting are good.(3)Using PMMA specimens for blasting tests,it was found that the crack direction of the groove hole was concentrated at the groove,and the crack was 1.3cm longer than the circular hole crack;Within the experimental range,the penetration effect of cracks between holes decreases with the increase of hole spacing,and the overall crack length decreases with the increase of the thickness of the smooth blasting layer.The density coefficient of the holes is maintained between 0.71 and 1.40,indicating a good blasting crack effect.(4)A three-dimensional numerical slope model is established for the cutting slope of Provincial Highway 339 K29+580-K29+650,and the SPH-FEM coupling algorithm is used to simulate the blasting of the reserved smooth blasting layer.Firstly,adjust the parameter adaptability of the HJC model,and then analyze the particle velocity evolution and motion state.It is found that as the thickness of the blasting layer increases,the blasting excavation effect weakens;When the reserved smooth blasting layer is 100 cm and the perforation density coefficient is 1.1,the range of blasting damage and throwing effect are better.At the same time,the optimized charging structure with increased water and air spacing can reduce blasting damage and improve blasting efficiency. |
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