The dispersed cartridge blasting design, which is a further optimization of the loading structure of chamber blasting is evolved from the concentrated cartridge blasting design.. This paper mainly introduces the basic conditions and character analysis of dispersed cartridge blasting, design and choice of blasting parameters and the excavation procedure as well as the chamber-cutting method in single-track railway construction.


Chamber loosening blasting has more than one advantages with obvious economic benefits: it is not limited by topographic conditions: it doesn't need large drilling and blasting equipment: and it can be done at several faces at the same time, which helps to increase working speed, shorten construction duration, and lower construction cost, hence it has a wide application in rock blasting of large quantities. For rock excavation in railway construction, except for very hard monolith, chamber blasting is usually adopted for loosening purpose. However, since the road cutting is of a trapezoidal section and the width of excavation for a single-line railway is relatively small (6–8m), concentrated cartridge blasting is usually adopted, leaving a V shaped crater. The shortcoming of such a blasting design is the large charge of the primary explosive and the shaking effect of blasting on the side slopes. In fact, by comparing the actual excavation outline with the designed outline, we find that large quantities of over breaking at the top and under-breaking at the bottom often happens with concentrated cartridge blasting, resulting in a substantial quantity of work for the side slopes, which, on the one hand, has a negative effect on the stability of the side slopes, and on the other hand, will also incur additional cost to the project. To make use of the advantages and overcome the disadvantages of chamber blasting, the key technology is to modify the concentrated charging structure so as to reduce the shaking effect of blasting on the side slopes and improve the shape of the crater to be as similar as possible to the designed road cutting section.


Engineering experiences have proved that, compared with concentrated cartridge blasting, the column-cartridges blasting can more evenly distribute the energy released, reduce the ratio of blocks and excessive crushing, help the inversion of the casting energy, and reduce the influence on the stability of the slopes. There are both difference and similarity between the working process of column-cartridges blasting and concentrated cartridge blasting. The blasting parameters of the former can be derived from the latter and the charge quantity can be calculated according to the concentrated cartridge and then evenly distributed into column cartridges according to the volume to be blasted. So, column-cartridges blasting, if it could be used in road cutting, would be an ideal plan. However, because of the relatively narrow section of excavation, and in order to guarantee the conformity to the designed outline, the one-time excavation depth in a single line railway is usually controlled within 10m.

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