Technology Of Shaft Excavation By One-step With Spherical Charge Blasting Based On Deep-hole Presplitting

The shaft excavation technology has been an emphasis and a hotspot in the field of geotechnical engineering research. In recent years, with the promotion of High sublevel mining system and cavity filling technology, a series of related engineering problems gradually appeared, especially on how to form the high depth and large section shaft efficiently. Influenced by drilling equipment and rock clamping force, the tradition technology of shaft excavation by blasting cannot meet the engineering needs. Therefore, proposing a high depth, large section shaft excavation technology has become a problem that must be solved.Based on the analysis of traditional shaft excavation technology, a series of methods are used for the new technology in Sandaozhuang open-pit mine supported by the project of shaft excavation by one-step with deep-hole blasting, including theoretical analysis, mathematical model, numerical simulation and industrial test. Researching results can be concluded as follow:(1) The theory of shaft excavation by one-step with spherical charge blasting based on deep-hole presplitting is studied. According to the theory, the main presplitting parameters (decoupling coefficient, liner density, presplitting holes spacing) and spherical charge blasting parameters (holes layout, stratification height, hole spacing, delay time) are confirmed.(2) Based on the projection pursuit regression theory, seven factors (compressive strength, tensile strength, rock density, diameter of presplitting hole, spacing of presplitting hole, decoupling coefficient, line charge density) are selected and the predictive model are set up to predict half-hole rate and pre-splitting crack breadth. Apply the established model to predict the effect of presplitting blasting,25groups of data are trained and tested. The predicted results are consistent with the measured ones. Thus, this paper uses the model to optimize the presplitting parameters in Sandaozhuang open-pit mine.(3) Through the approach of LS-DYNA, dynamic rock breakage process of millisecond blasting and same delay time blasting can be visualized. The research results of numerical stimulation indicate that the same delay time blasting are better than the former in blasting effects and energy utilization. After, the numerical stimulation of shaft excavation effects by spherical charge blasting is achieved and it shows that the rock clamping force gradually increases with the increase of layers. According to the range of elements failure, the spacing with spherical hole and presplitting hole needs to satisfy the relationship:S≤1.35m.(4) Finally, In Sandaozhuang open-pit mine, two industrial tests are done with the selected parameters and it succeeds with forming a26m patio and a30m patio. The rock lumpiness is well-distributed. The results of the tests prove the feasibility of this Deep-hole Presplitting Spherical Charge Blasting technology in shaft excavation.