Introduction of tunnel blasting method?

What are the blasting methods commonly used by China construction tunnel construction enterprises at present? What is the basic situation? The basic contents of Tunnel Blasting compiled by Bian Xiaozhongda Consulting Company are as follows:

According to the knowledge of architectural knowledge column of this website, the basic situation of tunnel blasting method is as follows:

Cut blasting is usually used in tunnel blasting, that is, the holes on the excavation section are arranged in different zones, and the excavation is gradually expanded. According to the position and function of blastholes, blastholes are divided into three types: cut holes, auxiliary holes and peripheral holes. These three kinds of blastholes have their own functions, so they all have different requirements on position, length, direction and spacing, except that blasting excavation is completed by cyclic footage.

Zhong Da Consulting Bianxiao Company takes the hole arrangement method of tunnel blasting excavation as an example, and the basic situation is as follows:

(1) hole cutting

① Arrangement of cut holes: To arrange cut holes reasonably, we should master the three dimensions of holes: depth, density and inclination, and determine the charge and shooting sequence through calculation.

(2) The function of the cut gun is to cut a small gap at a proper position on the excavation surface and form a new free surface, which will create a more favorable free surface for the sub-gun after blasting and improve the blasting efficiency.

(3) The cut hole itself has only one free surface, and it is squeezed by surrounding rock, so it is often necessary to use a larger explosive unit consumption K value and a larger charging coefficient A value to increase the blasting crushing area, and use the explosion shock wave and explosion products to do work and throw the rock out of the notch. In order to ensure that the cutting gun can effectively throw the stone slag out of the notch, the cutting hole is often deeper than the designed driving footage 10-20 cm, and the reverse front charge and double thunder initiation are adopted;

④ The notch size is often between 1.0 ~ 2.5m2, which should be coordinated with the circulating footage, section size and cutting method. It is required that the error of eye opening distance and fundus distance should not be greater than 5 m;

⑤ Cutting methods can be generally divided into oblique cutting and straight cutting. The advantages of oblique cutting are: the cutting mode and angle can be selected according to the actual situation of rock stratum, the stone slag is easily thrown out of the notch, and the number of cutting holes is small. Its disadvantage is that the concentration of holes is limited by the size of tunnel section, which is not convenient for multiple rigs to drill at the same time, and it is difficult to accurately grasp the drilling direction.

⑥ Advantages of straight hole cutting: it is convenient for multiple machines to drill holes at the same time, and it is not limited by the section size to the blasting footage. It is suitable for deep-hole blasting, which provides favorable conditions for accelerating excavation speed, and the throwing distance of cutting stone slag is short. At present, direct cutting is mostly used in the field. However, the disadvantage is that the number of blastholes is large, the unit consumption K of explosives is also increased, and the position and vertical direction of blastholes require high accuracy to ensure good blasting effect. Because of the changeable geology, several cutting methods can be mixed.

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