JPH0213240B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a blasting method employed when excavating a tunnel in ground made of hard rock.

[Conventional technology]

BACKGROUND ART Conventionally, a core blasting method has generally been adopted as a blasting method when excavating a tunnel in ground made of hard rock. In the case of this core blasting method, as shown in Figures 6 and 7,
A large number of centrally inclined blast holes 5 are formed in the bedrock 1 of the tunnel excavation face in the central part of the tunnel cross section, slanting from the rear to the front so as to approach the tunnel center line, and a large number of centrally inclined blast holes 5 that are lined up along the outer peripheral contour of the tunnel cross section. The outer peripheral blast hole 6 and each of the central inclined blast holes 5
and a large number of intermediate blast holes 7 arranged so as to surround the center of the tunnel cross section between the outer circumferential contours, and each blast hole is loaded with an explosive, and then first the central inclined blast hole 5 is drilled. By igniting and detonating the explosive, and crushing the rock 8 in the center of the tunnel cross section and ejecting it to the rear (front), a free surface is formed by core removal, and then the explosive in the intermediate blast hole 7 and the outer blast hole This is a construction method in which the rock at the face is successively crushed toward the inner free surface by igniting and detonating the explosives in order with a time difference of several milliseconds.

[Problem to be solved by the invention]

However, in the case of the conventional core blasting method, after the core is removed by explosion of the explosive in the central inclined blast hole 5 to form a free surface, the explosive in the intermediate blast hole 7 and the explosive in the outer peripheral blast hole 6 are removed. are detonated one after another, and the explosive force applies a force that moves the rocks around the free surface toward the center of the tunnel cross section.
Since the rock around the free surface resists the moving force due to the arch effect, the explosive force cannot be used effectively, and therefore a large amount of explosives must be used, which is uneconomical, and When the amount of explosives used increases, a pollution problem arises in that the blasting noise and vibration at the time of blasting increase.Furthermore, since the outer peripheral blasting holes 6 have a circular cross section and are drilled at large intervals, unevenness of the outer peripheral finished surface may occur. The problem is that it is large.

[Object and structure of the invention]

The purpose of this invention is to provide a blasting method for tunnel excavation that can advantageously solve the problems of the previous technique. A large number of slit-like outer circumferential holes 2, which are elongated along the outer circumferential contour of , a central blast hole 3 and a large number of intermediate blast holes 4 arranged between the outer peripheral contour so as to surround the center of the tunnel cross section are drilled, and then an explosive is charged into the central blast hole 3 and the intermediate blast holes 4. Blasting for tunnel excavation characterized by loading, then first igniting and detonating the explosive in the intermediate blast hole 4, and then igniting and detonating the explosive in the central blast hole 3 to crush the bedrock of the tunnel excavation face. It's in the construction method.

〔Example〕

Next, the present invention will be explained using illustrated examples.

1 to 5 show an embodiment of the present invention, in which the base ends of booms 11 and 12 are pivotally attached to a rotating support base 10 provided on a truck 9 by horizontal shafts. The intermediate portions of the booms 11, 12 and the rotating support base 10 are connected via hydraulic cylinders 13, 14 for elevation, and support members 17,
18 are connected to each other, guide cells 19 and 20 are rotatably attached to each support member 17 and 18, and each guide cell 19 and 20 has a slit rock drill 21,
22 is provided so as to be movable in the longitudinal direction of the guide cell.

To explain the configuration of the slit rock drills 21 and 22, five impact hammers 28 to 32 having spline shafts 23 to 27 are arranged in parallel,
Cross bits 33 to 37 are attached to the tip of each spline shaft 23 to 27, respectively, so that the rotation loci of the outer circumferences of adjacent cross bits 33 to 37 overlap and the phases of adjacent cross bits 33 to 37 change by 45 degrees. Gears 38 to 42, which are disposed in A drive pinion 45 rotated by a fixed motor 44 is meshed with the end gear 38, and the spline shafts 23-27 are continuously rotated by the motor 44 via the drive pinion 45 and gears 38-42.

The slit rock drills 21 and 22 intermittently drill a large number of slit-shaped peripheral holes 2, which are elongated along the peripheral contour of the tunnel cross section, in the rock mass 1 of the tunnel excavation face intermittently along the peripheral contour. be done. In this case, the length L of the slit-shaped peripheral hole 2 in the direction of the peripheral contour and the interval D are appropriately determined depending on the rock quality.

In addition, a plurality of (five in the illustrated case) central blast holes 3 located at the center of the tunnel cross section and a hole between the central blast holes 3 and the outer circumferential contour are drilled into the bedrock 1 using an ordinary rock drill. A large number of intermediate blast holes 4 are bored so as to surround the center of the tunnel cross section. The central blast hole 3 is bored so as to extend substantially parallel to the tunnel axis.
The holes are tilted so as to deviate outward as they move forward, making it easier for the rocks crushed by the first blast to be discharged to the rear (front).

Next, each central blast hole 3 and each intermediate blast hole 4
After the explosives are loaded only in the holes, the explosives in each intermediate blast hole 4 are ignited and exploded, so that the rock between the intermediate blast hole row and the slit-shaped outer hole row is pushed outward by the explosive force. After being compressed and crushed to form a free surface, the explosive in the central blasting hole 4 explodes, and several milliseconds later, the explosive in the central blasting hole 3 is ignited and exploded, resulting in intermediate blasting. The rock outside the row of holes is compressed outward by the explosive force and fractured.

〔Effect of the invention〕

Since this invention is configured as described above,
This produces the effects described below.

When a rock is fractured by the ignition explosion of explosives loaded in a large number of intermediate blast holes 4, there is a free surface consisting of a large number of slit-shaped peripheral holes 2 on the outside of the rock to be crushed, so the resistance force due to the rock arch effect is Even when the rock is crushed by the ignition explosion of the explosives loaded in the central blast hole 3, there is a free surface on the outside of the rock to be crushed, so the rock has a resistance force due to the arch effect. There is no explosion, and therefore rocks can be easily crushed with a small amount of explosives, making it economical and producing less blasting noise and vibration during blasting.
Furthermore, since a large number of slit-shaped outer circumferential holes 2, which are elongated along the outer circumferential contour of the tunnel cross section, are provided intermittently along the outer circumferential contour, unevenness on the finished surface of the tunnel outer circumference can be reduced. , it is possible to prevent cracks caused by blasting from reaching the rock mass outside the outer peripheral contour of the tunnel cross section.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention, and FIG. 1 shows a slit-shaped peripheral hole drilling device, a slit-shaped peripheral hole drilled in rock, an intermediate blast hole, and a central blast hole. 2nd longitudinal side view showing
The figure is a front view showing the slit-shaped peripheral hole, intermediate blast hole, and central blast hole drilled in the rock; Figure 3 is a partial cross-sectional plan view showing a part of the slit rock drill; Figure 4
The figure is a front view showing the arrangement of cross bits in the slit rock drill, and FIG. 5 is a longitudinal sectional front view showing the slit-shaped outer circumferential hole. FIG. 6 is a longitudinal side view showing the arrangement of blast holes in the conventional blasting method, and FIG. 7 is a front view thereof. In the figure, 1 is a rock, 2 is a slit-shaped peripheral hole,
3 is the central blast hole, 4 is the intermediate blast hole, 9 is the trolley, 1
1 and 12 are booms, 15 and 16 are rotation mechanisms, 19 and 20 are guide cells, 21 and 2
2 is a slit jackhammer, 23 to 27 are spline shafts, 28 to 32 are impact hammers, 33 to 37 are cross bits, 38 to 42 are gears, 44 is a motor, 4
5 is a drive pinion.

Claims (1)

[Claims] 1. A large number of slit-shaped outer peripheral holes 2, which are elongated along the outer peripheral contour of the tunnel cross section, are intermittently bored in the bedrock 1 of the tunnel excavation face along the outer peripheral contour, and the tunnel A central blast hole 3 located at the center of the cross section, and a number of intermediate blast holes 4 arranged between the central blast hole 3 and the outer peripheral contour so as to surround the center of the tunnel cross section, and then Explosives are loaded into the blast hole 3 and the intermediate blast hole 4, and then the explosive in the intermediate blast hole 4 is ignited and exploded first, and then the explosive in the central blast hole 3 is ignited and exploded to destroy the bedrock of the tunnel excavation face. A blasting method for tunnel excavation characterized by crushing.