JP3436973B2 - Prior reinforcement method of tunnel leg - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preliminarily reinforcing a support portion of a leg portion of a steel gate-type support structure on a side wall of a tunnel during excavation of the tunnel.

[0002]

2. Description of the Related Art Generally, in tunnel excavation work by the NATM method, there is a limit to the amount of subsidence, and it is necessary to suppress subsidence as much as possible.

By the way, in conventional tunnel excavation,
Each time a predetermined length of excavation is carried out, rock bolts or steel pipes are driven horizontally or diagonally downward toward the tunnel side at the lower end positions of both sides of the face as a reinforcing material, and after the face is excavated, steel support work built in this part.

The ground near the legs is reinforced.

[0005]

In the above-mentioned conventional reinforcing material, since the reinforcing material driving-in construction is carried out after the construction of shotcrete or steel support construction, most of the crown and subsidence have already occurred. After that, when the reinforcement material is installed during tunnel excavation, which involves excavating the upper and lower halves alternately, such as the bench-cut method, most of the top and subsidence has already occurred. Therefore, in this method, it is unavoidable to reduce the settlement by the lower half excavation, and the effect of settlement suppression is halved at present.

[0006]

According to the present invention, leading foot bolts 4 are provided obliquely downward toward the front of the cutting face 1 on the supporting portions of the legs of the support 3 on the left and right sides of the cutting face 2 of the upper half 1 of the tunnel. Driving, preceding foot bolt 4 to be driven
Is a tunnel leg that is installed by alternately changing the inclination angles α, α ′ in the front-rear direction from the horizontal plane and the inclination angles θ, θ ′ in the left-right direction from the vertical plane for each construction span of the support work 3. This is to propose a method of preceding reinforcement of a part.

[0007]

Operation: By driving the preceding foot bolts 4 into the supporting portions of the legs of the supporting members 3 on the right and left sides of the cutting face 2 of the upper half 1 of the tunnel diagonally downward toward the front of the cutting face, before the excavation of the cutting face, the ground ahead of it is excavated. To suppress the top and ground subsidence during the excavation of the upper half 1 and the subsidence of the ground during the excavation of the lower half 5 to reduce the subsidence amount.

By driving the leading foot bolt 4 in various angles by driving it in various directions, pressures in various directions acting on the ground are surely received, the ground is restrained, and the effect of sinking reduction is enhanced as the sewing ground.

[0009]

[Example] In the tunnel excavation work by the NATM method, a leading portion of rock bolts is provided diagonally downward toward the front of the cutting face on the supporting portions of the legs of the steel gate-type support 3 on the left and right sides of the cutting face 2 of the upper half 1 of the tunnel. Drive in the foot bolt 4.

As the preceding foot bolt 4 to be driven, one having a length of about 3 to 4 m which is usually used as a lock bolt is used, and as shown in FIGS. The installation is performed by alternately changing the inclination angles α, α'of the direction and the inclination angles θ, θ'of the horizontal direction from the vertical plane (for example, α = 15 °, α '= 30 °, θ = 30 °,
θ '= 40 ° etc.).

As described above, by driving the leading foot bolt 4 in various angles by driving it in a polygonal manner, pressures in various directions acting on the ground are surely received to restrain the ground and enhance the effect of reducing the sinking as the sewing ground. The amount of subsidence can be reduced.

The leading foot bolt 4 is basically one on each side for each installation span. However, if the tunnel to be constructed has a large cross section, is soft sandy ground, or has a small overburden. If the allowable subsidence is small, the ground will be strengthened by adding two or more depending on the construction conditions that are usually required.

When a plurality of leading foot bolts 4 are provided at one place in this way, the installation height is 30 to 50, respectively.
Drive in multiple steps with a difference of about cm.

[0014]

[Effects of the Invention] By driving the legs of the supporting structure on the left and right sides of the face in the upper half of the tunnel diagonally downward toward the front of the face, the ground in front of the face is reinforced before excavation of the face, and the upper half is cut. The amount of subsidence can be reduced by suppressing the subsidence of the top and the ground during excavation of a part and the subsidence of the ground during the excavation of the lower half.

By driving the leading foot bolts in various angles with various angles, pressures in various directions acting on the ground can be reliably received and the ground can be restrained, and the effect of sinking reduction can be enhanced as a stitch.

[Brief description of drawings]

FIG. 1 is an additional side view showing a construction state of the present invention.

FIG. 2 is a cross-sectional front view showing a construction state of the present invention.

FIG. 3 is a vertical sectional side view showing a driving mode of a foot bolt of the present invention.

[Explanation of symbols]

1 upper half of the tunnel 2 face 3 support work 4 Leading foot bolt 5 Lower part of tunnel

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Claims (2)

(57) [Claims] 1. A leading leg of a tunnel leg portion, characterized in that front foot bolts are driven diagonally downward toward the front face of the face into the supporting portions of the leg portions of the steel gate-type support work on the left and right sides of the face face in the upper half of the tunnel. Reinforcement method. 2. A front foot bolt is driven diagonally downward toward the front of the face into the supporting portions of the legs of the steel portal support on the left and right of the face in the upper half of the tunnel. A method for preliminarily reinforcing a tunnel leg portion, characterized in that the inclination angle in the front-back direction from the horizontal plane and the inclination angle in the left-right direction from the vertical plane are alternately changed for each span of construction.