At this stage, what are the blasting methods commonly used by tunnel construction companies in my country? What's the basic situation? The editor of Zhongda Consulting has compiled the basic content of tunnel blasting as follows:
Zhongda Consulting has compiled the knowledge from the construction knowledge column of this website. The basic information of tunnel blasting methods is as follows:
Tunnel blasting is usually used Undercut blasting involves zoning out blastholes on the excavation section and blasting them in sequence, gradually expanding to complete one excavation. The zoning is based on the location and function of the blastholes. There are three types of blastholes: cutout holes, auxiliary holes, and peripheral holes. In addition to completing a cycle of blasting and excavation, these three types of blastholes each have their own functions, so they each have different requirements for location, length, direction, and spacing.
The editor of Zhongda Consulting takes the blasthole layout method in tunnel blasting and excavation as an example. The basic situation is as follows:
(1) Cutting holes
① For the layout of the cutout holes, the three dimensions of the blastholes should be mastered when arranging the cutout holes properly: depth, density and slope, and the amount of charge and blasting sequence should be determined through calculations
②The role of the cutout cannon, It is to first dig out a small notch at an appropriate part of the excavation surface to form a new air surface, creating a more favorable air surface for the auxiliary gun for post-explosion, thereby improving the blasting efficiency
③The cut hole itself has only one free surface and is squeezed by the surrounding rocks. Therefore, it is often necessary to use a larger explosive unit consumption K value and a larger charging coefficient A value to increase the blasting and crushing area. And use the explosion shock wave and explosion products to do work, throwing the rock out of the slot. In order to ensure that the cutting gun can effectively throw the gravel out of the slot, the cutting hole is often deepened by 10-20cm compared with the designed tunneling footage, and reverse frontier charging and double mine detonation are used;
④ The notch size is usually between 1.0 and 2.5m2, and must be coordinated with the circular footage, section size and cutout method. It is required that the error of the distance between the eye openings and the distance between the eyes shall not be greater than 5m;
⑤The cutting methods can generally be divided into two categories: slant-eye cutting and straight-eye cutting. The advantages of slant-eye cutting are: The cutting method and cutting angle are selected based on the actual conditions of the rock formation. It is easy to throw gravel out of the notch and the number of cutting holes is small. Its disadvantage is that the hole concentration is limited by the tunnel cross-section size, which makes it inconvenient for multiple drilling rigs to drill holes at the same time, and it is difficult to accurately control the drilling direction.
⑥ Advantages of straight hole cutting: it is convenient for multiple machines to drill holes at the same time and is not restricted by the cross-section size on the blasting footage. It is suitable for deep hole blasting, thus providing favorable conditions for accelerating the excavation speed, and The throwing distance of undercutting gravel is shorter. At present, direct eye cutting is mostly used on site. However, the disadvantage is that it has a large number of blastholes, the K value of the unit consumption of explosives also needs to be increased, and the position and vertical direction of the blastholes require high accuracy to ensure good blasting effects. Due to the changeable geology, several cutting methods can be mixed and used.
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