JP2001026922A - Earthquake-proof reinforcing method for existing tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform earthquake-proof reinforcing work for an existing tunnel so as to reduce shear deformation amount of the ground at outer periphery of the existing tunnel when earthquake occurs. SOLUTION: Soil improvement agent is poured into outer periphery of a tunnel 1 from the inside of the tunnel 1 or a ground surface 6 to increase shear rigidity of the ground 7 at outer periphery of the tunnel 1 so as to reduce shear deformation amount 9 of the ground 7 at outer periphery of the tunnel 1 when earthquake occurs and shear deformation amount 9 of the tunnel 1 so that a cross sectional force generated when earthquake occurs of the tunnel 1 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic retrofitting method for an existing tunnel, and more particularly to a seismic retrofitting method for an existing tunnel by improving the ground around the tunnel and suppressing the shear deformation itself of the cross section of the tunnel. It is.

[0002]

2. Description of the Related Art Conventionally, when a shield machine is excavated in the ground to form a tunnel, a ground around the shield machine is stirred while a solidifying agent mixed with a fibrous reinforcing material is injected thereinto, and the surroundings of the shield machine are stirred. There is one that forms a fiber-reinforced solidified layer by kneading a solidifying agent and ground. On the other hand, when reinforcing existing underground structures such as subways, roads and sewer tunnels in preparation for a large earthquake, shear reinforcement by winding reinforced concrete on side walls and floor slabs, and iron plate And reinforced plastic (FRP) sheet attachment, shear and bending reinforcement, and toughness and shear reinforcement of the middle pillar in a tunnel having a middle pillar.

[0003]

The method of reinforcing the ground around the shield machine is intended to prevent collapse and water leakage of the ground after the construction of the tunnel and to maintain the stability of the tunnel. Is not considered.

On the other hand, among the above-mentioned seismic reinforcement, the reinforcement is effective for shear reinforcement for increasing the cross section of a member or for bending reinforcement in which the inner surface of a structure is tensile, but bending in which the outer surface of the structure is tensile. It is not effective for reinforcement for Furthermore, due to the limited space of the structure itself, it is often not possible to reduce the inner space section by increasing the member cross section of the structure.

[0005] In addition, when the above-mentioned reinforcement is applied to a subway station or the like, the reinforcement work is performed while the service is in use, and the reinforcement work becomes difficult due to restrictions on the building space and the like. Therefore, to reinforce the exterior of the structure, increase the section of the member, or increase the bending strength, do not excavate the ground to the structure position in an underground structure (tunnel) that is covered with the ground. As long as it is impossible.

Accordingly, seismic reinforcement of the tunnel in case of a large earthquake is performed from the inside of the tunnel and from the ground surface to increase the shear rigidity of the ground around the tunnel, thereby reducing the amount of shear deformation of the ground around the tunnel. The technical problem to be solved arises in order to obtain the method, and the present invention aims to solve this problem.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and it is an object of the present invention to provide a method for seismic retrofitting of an existing tunnel which has been evaluated as needing seismic retrofitting by seismic diagnosis of the tunnel. By injecting a ground improvement material from the inside of the tunnel or from the ground surface to the outer periphery of the tunnel, and increasing the shear rigidity of the ground around the tunnel, reducing the amount of shear deformation of the ground around the tunnel during an earthquake, and A seismic reinforcement method for an existing tunnel that reduces the cross-sectional force generated during an earthquake in the tunnel by reducing the amount of shear deformation of the tunnel, the range of a ground improvement unit that increases the shear rigidity of the ground around the tunnel, and required improvements The rigidity of the back ground is
The seismic retrofitting method of the existing tunnel determined by numerical analysis, the range of the ground improvement part and the required rigidity of the ground after the improvement are based on the permissible value of the tunnel member sectional force in the seismic design and the range of the ground improvement part. Or, it is determined from the relationship with the Young's modulus of the improved ground, and provides a method for seismic reinforcement of an existing tunnel by injecting a ground improvement material blended to be the improved ground of the Young's modulus into the ground around the tunnel. is there.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows an existing excavation tunnel 1 whose periphery is covered with a ground 7. The excavation tunnel 1 has an oblong rectangular section having an upper floor slab 2 at an upper part, a lower floor slab 3 at a lower part, and side walls 4 and 4 on both sides, and a middle pillar 5 is erected in the center. Seismic reinforcement is required to protect the excavation tunnel 1 from shear deformation 8 of the ground 7 during a large earthquake. When the excavation tunnel 1 is newly constructed, a seismic isolation layer (not shown) is formed between the surrounding ground and the tunnel to greatly reduce the cross-sectional force generated due to the cross-sectional deformation of the tunnel. Safety at the time can be improved. However, it is difficult to form the seismic isolation layer in an existing tunnel.

The seismic load that generates a sectional force in the cross section of the tunnel is caused by the relative displacement of the ground relatively generated between the upper and lower slabs, and the peripheral surface caused by the difference between the rigidity of the tunnel and the rigidity of the ground. It consists of the shear force and the inertial force due to the mass of the tunnel itself. When comparing the ratio of the seismic loads,
Depending on the cross-sectional shape and the rigidity of the tunnel, it is not clear which of the above is larger, but it occupies most of the seismic load, and the above-mentioned ratio is small.

Therefore, by increasing the shear rigidity of the ground 7 on the outer periphery of the excavation tunnel 1, the amount of shear deformation 9 of the ground 7 on the outer periphery of the excavation tunnel 1 during an earthquake is reduced. The upper floor slab 2 and the lower floor slab 3 of the excavation tunnel 1 in order to reduce the shearing cross-sectional force of the excavation tunnel 1 by reducing the amount of shear deformation of the excavation tunnel 1.
And the ground 7 surrounding a predetermined portion inside the side walls 4 and 4.
A plurality of ground improvement materials such as cement milk, fine particle cement powder, etc. are introduced into the outer ground 7 of the excavation tunnel 1 from the perforated portion (not shown) by a nozzle (not shown). )) To construct the ground improvement unit 10. The range of the ground improvement unit 10 and the required rigidity of the ground 7 after the improvement are set by numerical analysis performed in advance as described later.

In the case of a shield tunnel in the injection of the ground improvement material, etc., it is possible to use a grout hole (not shown) used for the backfill injection of the shield tunnel. Further, when a tunnel is constructed at a relatively shallow position from the ground surface 6, the ground improvement unit is directly used from the ground surface 6 by using a boring hole (not shown) by a boring machine (not shown). Form 10.

Next, the seismic retrofitting method of the existing open-cut tunnel 1 will be described with reference to FIGS. FIG. 2 (a)
Shows an analytical model for improving the ground as seismic reinforcement of the excavation tunnel 1. The ground 7 has a layer thickness from the base 12 to the ground surface 6 of 15 m. The interval between the ground surfaces 6 is 4.5 m, the tunnel height between the upper slab 2 and the lower slab 3 of the excavation tunnel 1 is 7 m, and the height of the excavation tunnel 1 between the side walls 4, 4 at both ends. The middle pillar 5 is erected at the center as a rectangular section having a width of 17 m in the width direction.

The ground 7 has a Young's modulus E of 1000 kgf / cm.
² , unit weight is 1.7 tf / m ³ , Poisson's ratio is 0.4
8 uniform ground. The excavation tunnel 1 is buried at a position close to the base 12, that is, at a distance of 3.5 m between the base 12 and the lower slab 3 so that the influence of shear deformation of the ground 7 is relatively large. I do. In the analysis, the surrounding ground was modeled with a plane strain element and the tunnel member was modeled with a beam element.
This is performed using a three-dimensional finite element model. Further, a sinusoidal horizontal acceleration distribution 11 of 300 gal on the ground surface 6 is assumed, and a ground inertia force corresponding thereto is applied statically to each node of the analysis model as a seismic load, thereby The deformation of the ground 7 and the open tunnel 1 is analyzed linearly.

FIG. 2 (b) shows that the width of 2 m from the side walls 4 and 4 on both sides of the cut tunnel 1 and the four corners of the cut tunnel 1 are 45 m from the upper deck 2 and the lower deck 3 respectively. Assuming an improved pattern (Type-1) with ground improvement in the range of °,
FIG. 2 (c) assumes an improved pattern (Type-2) in which the entire outer periphery of the excavation tunnel 1 is improved over the ground over a width of 2 m, and the ground based on the improved range in each analysis model. 7
The analysis is performed by increasing the Young's modulus from 10 times to 1000 times of the above. The analysis relates to the horizontal relative displacement between the upper slab 2 and the lower slab 3 at the center position of the excavation tunnel 1 and the sectional force of the tunnel member, and each analysis case for the base case where the ground improvement and the ground improvement are not performed. Obtain the ratio of the maximum value of, and organize the analysis results.

FIG. 3 (a) shows the horizontal case with respect to the basic case.
The ratio E of the Young's modulus of the ground improvement unit 10 _RAnd ground improvement
Relative displacement RD_RThis shows the change of The phase
Displacement RD_RConsidering the change in
In the Type-1 improvement pattern that only improves the ground,
Young's modulus ratio E_REven when the size is 1000 times
The relative displacement RD of the channel 1_RCan be reduced to only about 60%
I can't. On the other hand, Type-2 modification to improve the ground around the entire circumference
In a good pattern, the Young's modulus ratio E_RIs 100 times that phase
Displacement RD_RCan be reduced to 40%, and the Young
Rate ratio E_RBut relative displacement up to nearly 10% at 1000 times
RD_RAnd ground improvement is one of the seismic loads.
It turns out that it is effective in reducing a certain ground displacement.

FIG. 3B shows a shear force ratio S._RAnd the young
Rate ratio E_RAnd only the outside of the side walls 4 and 4
With the improved Type-1, almost no effect can be obtained,
In the Type-2 improved pattern for improving the outer circumference,
Ratio of the Young's modulus to _RIf you take large, it is 1 or less
Thus, it can be seen that this is effective in reducing the sectional force.

FIG. 3C shows a bending moment ratio M _R.
Shows the relationship between the ratio of the Young's modulus and the ratio of the Young's modulus E _R. Similar to the relationship with the ratio of the shearing force S _R , little effect is obtained with the Type-1. E _R 500
It can be seen that it is possible to halve it about twice.

From the above, as a result of the seismic design based on each technical standard, assuming that the existing open-cut tunnel 1 has no bending strength, for example, as shown in FIG. The ratio E _R = 600 of the Young's modulus is determined from the allowable value of the section force of the member of the open-cut tunnel 1 that the seismic design will not be established unless the value is set to 0.5. Improvements can lead to acceptable bending moments.

If the ground improvement is performed by changing the Young's modulus by performing a numerical analysis in this way, the required ground rigidity can be obtained with the minimum necessary ground improvement. Incidentally, in order to obtain a ground having a predetermined Young's modulus, the cement milk injection rate is changed or the like. In addition, if the same effect can be obtained by the improvement of only the side wall instead of the improvement of the entire outer periphery, seismic reinforcement can be made.

Thus, the present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.

[0021]

As described above, according to the first aspect of the present invention, a ground improvement material is injected into a tunnel or from the ground surface.
Since the shear rigidity of the ground at the outer periphery of the tunnel is increased, seismic reinforcement can be performed without reducing the cross section inside the tunnel, and the shear deformation of the cross section of the tunnel can be efficiently reduced.

According to a second aspect of the present invention, the range of the ground improvement part and the required rigidity of the ground after the improvement are determined by numerical analysis, so that an easy and effective ground improvement zone can be set. Can be.

According to a third aspect of the present invention, the range of the ground improvement section and the required improvement of the ground rigidity are determined by the allowable value of the tunnel member sectional force in the seismic design and the range of the ground improvement section or the improved ground. Because the soil around the tunnel is improved by determining from the relationship with the Young's modulus of the tunnel, it is possible to improve the ground only at the necessary places by injecting the necessary minimum ground improvement material, etc. Since there is no need to perform this, economical ground improvement can be performed, and costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention and showing a state in which the outer periphery of an open-cut tunnel is improved in ground.

FIG. 2A is an explanatory cross-sectional view showing an analysis target ground and an open excavation tunnel. (B) Type-1 with ground improvement on both side walls of excavation tunnel
FIG. (C) Type-2 ground improvement of the entire outer periphery of the excavation tunnel
FIG.

3 (a) top floor plate-relationship diagram of the relative displacement ratio RD _R and E _R between under deck. (B) Relationship between shear force ratio S _R and E _R. (C) Relationship diagram between bending moment ratio M _R and E _R.

[Explanation of symbols]

1 Tunnel (digging tunnels) Seismic shear deformation amount 10 ground improvement of 6 ground surface 7 Ground 9 Ground S _R shear ratio M _R bending moment ratio E _R Young's modulus

Claims (3)

[Claims] In a method of seismic retrofitting of an existing tunnel, which has been evaluated that seismic retrofitting is necessary by a seismic diagnosis of the tunnel, a ground improvement material is injected into the outer periphery of the tunnel from the inside of the tunnel or from the ground surface. By increasing the shear rigidity of the outer ground, the amount of shear deformation of the ground around the tunnel during an earthquake is reduced, and by reducing the amount of shear deformation of the tunnel, the cross-sectional force generated during the earthquake of the tunnel is reduced. A seismic retrofitting method for existing tunnels. 2. The existing tunnel according to claim 1, wherein the range of the ground improvement portion for increasing the shear rigidity of the ground around the tunnel and the required ground rigidity after the improvement are determined by numerical analysis. Seismic reinforcement method. 3. The range of the ground improvement portion and the required rigidity of the ground after the improvement are determined by comparing the allowable value of the sectional force of the tunnel member in the seismic design with the range of the soil improvement portion or the Young's modulus of the improved ground. 3. The method for seismic reinforcement of an existing tunnel according to claim 2, wherein a ground improvement material determined to be the relationship and blended so as to become the improved ground having the Young's modulus is injected into the ground around the tunnel.