Research On Non-undercutting Blasting Technology For Tunneling

As a new technology of tunnel excavation,non-undercutting simultaneous break staged blasting can good control the direction of explosive,reduce the blasting vibration to surrounding rock,make full use of explosive energy,and implement more effectively the mechanical construction of the whole tunnel section.At present,the study of non-undercutting blasting technology is relatively less,it is basically in the enlightenment stage of the preliminary practice project,and research analysis of the basic theory of rock damage and the influence of parameters is still rare.(1)On the basis of summarizing the advantages and disadvantages of cutting blasting,the basic principle of non-undercutting simultaneous break staged blasting is put forward and preliminary analyzed,the effect of non-undercutting blasting control parameters are analyzed.The pre-splitting fissure of blasting former reserving smooth blasting layer is the key to non-undercutting blasting,through the analysis of basic theory,under the action of explosion stress wave and explosive gas fracturing between adjacent hole charging,middle rock mass fracture penetrate and pushed to the direction of tunnel opening sections.(2)By using ANSYS/LS-DYNA numerical simulation software,this paper builds the two-dimensional double holes and triple holes model of non-undercutting simultaneous break staged blasting,and based on the large deformation theory and blasting parameters weighting analysis,study the influence factors of hole spacing,initiation time and empty hole etc of non-undercutting blasting.Analysis shows that the main effect of bar charging blasting stress wave is in the longitudinal direction.It is the key to select rational hole spacing for realizing non-undercutting blasting technology under the condition of a certain project.Initiation time in explosive detonation affects the effect of non-undercutting blasting technology in a certain extent.Empty hole can promote the expansion and connect of the crack,which is conducive to the implementation and popularization of non-undercutting blasting technology.(3)In the condition of the basic theoretical analysis and control variable simulation,this topic further analyze the each subsection reasonable sublevel caving depth,the reasonable charging of each section,and initiating the reasonable delay time between adjacent segment of non-undercutting simultaneous break staged blasting,hole section can good reduce the clip of rock when blasting.Finally,by three-dimensional simulation this paper analyze the effect of the row spacing and column spacing and tunnel cross-section hole arrangement to non-undercutting blasting technology,and through comparing with the traditional initiation method at the bottom of the bore,it is concluded that the non-undercutting blasting technology is advantageous,and has great prospects for development.