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Commonly used trenching methods for tunneling are:
First, the tapered groove. The tapered gutter is mostly used for shaft excavation, and a conical blasthole group is formed in the middle of the working face, and the bottom of each trough hole is not penetrated, forming a pyramid shape and a conical shape. The pyramidal gutter is used for roadway excavation, and the conical gutter is used for circular wellbore. See Figure 1.
Figure 1 Conical gutter
(É‘) pyramid; (b) conical
Second, the wedge-shaped groove. The wedge-shaped gutter uses two rows of opposite blastholes to form a wedge-shaped space after blasting. The wedge-shaped gutter is used for the excavation of medium-hard homogeneous rock and roadway section greater than 4 m 2 . According to the bedding or joint direction of the rock, there are two types of horizontal wedge-shaped gutters and vertical wedge-shaped gutters, as shown in Fig. 2.
Figure 2 Wedge-shaped groove
(É‘) vertical wedge; (b) horizontal wedge
Third, the cracked gutter, also known as the slit-shaped gutter, is used for medium-hard rock. It is now replaced by a barrel-shaped gutter, as shown in Figure 3.
Figure 3 cracked gutter
1-charge hole; 2-hole; I, II-detonation sequence
4. Barrel-shaped gutters, also known as cylindrical gutters, are the most widely used vertical gutters in medium-hard rock. There are many specific schemes. As shown in Figure 4.
Figure 4 Small diameter barrel-shaped gutter
1,2,3,...-starting order; â—‹-empty hole; â—-filling hole, hole spacing 100~300mm
Five, spiral groove. The distance between the charging holes and the empty holes of the spiral gutter is increasing in turn, and the volume of the cavity is gradually enlarged as the charging holes are sequentially detonated. The specific scheme is shown in Figure 5.
Figure 5 Schematic diagram of the spiral groove scheme
(É‘) small diameter holes; (b) large diameter holes; 1, 2, 3... detonation sequence
Sixth, mixing the trough. When the rock is extremely hard or the section of the roadway is large, a mixed groove can be selected. The specific scheme includes a double wedge or a barrel-shaped pyramid or a multi-layer groove. See Figure 6 and Figure 7.
Figure 6 barrel and cone and compound wedge groove
(É‘) barrel and cone; (b) compound wedge
Figure 7 Multiple grooving
(É‘) triple; (b) quadruple