JP3123863B2 - Tunnel support method and support member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel supporting method and a supporting member, and more particularly to a tunnel supporting method and a tunnel supporting method in which an internal pressure is applied to an excavated ground surface to prevent the progress of a tunnel loosening. Support member to be used.

[0002]

2. Description of the Related Art Recently, NAT tunnel excavation work has been carried out using NAT.
M (: New Austrian Tunneling Method) is becoming popular as a standard method. This NATM controls the displacement of the ground by using thin-walled shotcrete and rock bolts as flexible support members, and supports the tunnel using the inherent support force of the ground. . In tunnels constructed by the conventional sheet pile method, sheet piles and steel supports are used to support the loose load of the ground. On the other hand, in tunnels constructed by NATM, the shotcrete, which is the support member, is used as the foundation. Since the construction is carried out in close contact with the mountain surface, there are various advantages such as the temporal deformation and loosening of the ground can be minimized. For this reason, NATM has been actively employed in earth and sand tunnels in urban areas and the like.

On the other hand, in urban areas, excavation is often carried out in a soft sedimentary layer, so that a shield method is often employed in order to minimize the influence on ground structures. In this shield construction method, a prefabricated structural segment as a primary lining is continuously assembled in a cylindrical shape behind a shield machine, and a ground load acting on a tunnel is supported by the cylindrical support structure.

[0004] More recently, an ECL method has been developed and implemented which can prevent the formation of a gap (tail void) between a segment assembled after passing through a shield machine and the ground. In this ECL method, the inner formwork is assembled immediately after passing through the shield machine, and cast-in-place concrete is poured between the inner formwork and the ground. Therefore, the lining concrete is also filled in the tail void portion. The characteristic feature is that the shield excavator is propelled while reacting to the lining concrete. As described above, in tunnel excavation, it is important to surely prevent the loosening of the ground after excavation, and for this purpose, various support structures are being developed.

[0005] Except for the open tunnel, the tunnel generally has a substantially circular cross section formed by a combination of circular or circular arcs. This is because it is mechanically preferable that the lining member having the arch structure or the closing ring structure resists the ground load applied by tunnel excavation. When a ground load as an external pressure acts on the arch structure or the closing ring structure, a compressive force is predominantly generated in the lining member, but a bending moment also occurs due to uneven pressure or a distributed load. It is designed as a bending compression section.

[0006]

As described above, in the conventional tunnel excavation method, the tunnel lining is designed from the following viewpoints regardless of the method of construction. (1) After excavation, do not loosen the ground as much as possible. (2) The ground load acting on the lining member is borne by the arch structure or the closing ring structure as it is. That is, the ground support is performed early so as to suppress the loosening of the ground immediately after the tunnel excavation, but the design concept is such that the load due to the loosening of the ground generated up to that stage is borne by the supporting structure. For this reason, in the design of the lining member, a sectional design is performed by setting an applied load corresponding to earth pressure or a predetermined loose load.

By the way, the upper half arch of the tunnel section generally has an arc shape as shown in FIG. 8, and when there is no bedding or fault in the excavation section, the external pressure as shown (the magnitude of the load is Is non-scale). Therefore, the internal load P is positively applied by the support structure to offset the load acting on the ground, and the loosening of the ground can be prevented from increasing due to the internal pressure effect. NA as a support structure based on such an idea
There is a lock bolter of TM. A predetermined tensile force is introduced into the lock bolt cast on the tunnel wall surface, and an internal pressure can be applied to the tunnel wall surface by the introduced tensile force. At this time, a ground arch in a three-axis constrained state is formed in the ground, and the supporting force of the ground can be positively used for tunnel support.

However, since the lock bolt is an auxiliary support member used in accordance with the NATM support pattern, its installation pitch varies, and depending on the looseness of the ground or the installation pattern, it may cover the entire tunnel wall. There is a problem that a sufficient internal pressure effect cannot be provided. Further, since the lock bolt is buried linearly in the ground, it is difficult to grasp the internal pressure effect. Therefore, development of a supporting method and a supporting member capable of directly applying an internal pressure to a tunnel wall surface has been required. According to such a support method, it is possible to reduce the excessive load due to loosening by pushing back the looseness of the ground generated immediately after the excavation, and also to prevent the loosening over time.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, apply a direct internal pressure to a tunnel wall surface, reduce a loose load, and prevent a tunnel from being loosened. Is to provide.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention as a supporting method is a method in which an elastic arch member is brought into contact with an inner surface of a tunnel in a state in which the elastic arch member is curved and restrained, and the elastic arch member is released from a curving constraint. The restoring elastic deformation operation of the elastic arch member is restrained at the position of the inner surface of the tunnel to press the inner surface of the tunnel, thereby suppressing loosening of the ground of the tunnel.

Further, the present invention as a support member used directly in the above-mentioned support method is characterized in that the elastic arch member is separated from the elastic arch member by a predetermined eccentric distance via a spacer member attached to the elastic arch member. A tension wire holding member disposed along the longitudinal direction, and a tension wire inserted through and supported by the tension wire holding member, and provided with fixing portions at both ends, and introducing tension to both ends of the tension wire. Wherein the elastic arch member is curved.

[0012]

According to the present invention, the elastic arch member is brought into contact with the inner surface of the tunnel in a state in which the elastic arch member is curved and restrained, the curved arch constraint of the elastic arch member is released, and the restoration elastic deformation operation of the elastic arch member is changed to the inner surface position of the tunnel. And the inner surface of the tunnel is pressed, so that the internal pressure acts on the ground of the tunnel, so that the loosening of the ground that has already occurred can be pushed back, and the loosening that occurs with time is minimized. Can be minimized.

Further, a tension wire is inserted through a tension wire holding member disposed along a longitudinal direction of the elastic arch member at a predetermined eccentric distance via a spacer member attached to the elastic arch member. Since the fixing portions are provided at both ends and tension is introduced to both ends of the tension wire, the elastic arch member can be easily curved with a predetermined curvature, and the fixing at the both ends is released. Thereby, the tunnel inner surface can be surely pressed by the restoration elastic deformation operation of the elastic arch member.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a tunnel support method and a support member according to the present invention will be described below with reference to the accompanying drawings. FIG.
Each figure is an overall view showing each installation state of the support beam 1 as a tunnel support member. 2A shows the initial state of the support beam 1, and FIG. 2B shows a state in which the tension member of the support beam 1 is tensioned by introducing a predetermined tension, and the arch shape of the support beam 1 is changed to an arc shape. In the state shown in FIG. 3 (c), the supporting beam 1 is installed at the position of the tunnel wall in accordance with the curvature of the excavated tunnel ground, and is pressed against the tunnel ground to apply internal pressure to the tunnel wall. FIG.

Here, the structure of the support beam 1 will be described with reference to FIG. FIG. 2 shows a part of the support beam 1 in the initial state of FIG. In the figure, reference numeral 10 denotes an arch frame as an elastic arch member, and the arch frame 10 is made of two fiber-reinforced plastic inequilateral angle irons having a substantially L-shaped cross section and a large elastic deformation performance, The parallel position of the arch frame 10 is held by horizontal members 11 arranged at predetermined intervals. Also, both ends of the horizontal member 11 are arch frames 10.
Is fixed to a mounting flange (not shown) formed on the lower surface of the spacer frame, and an end portion 12a of a spacer frame 12 constituting a three-dimensional lattice is rotatably attached to the mounting flange. The spacer frame 12 has a substantially V-shape, and a vertex portion (a lower end portion in the figure) has a support hole 1 of a joint portion 14 formed on the upper surface of a sheath tube 13 serving as a tension wire holding member.
5 and is rotatably supported.

At this time, horizontal members 11 are arranged at predetermined intervals over the arch frame 10 in the longitudinal direction, and the upper end of the spacer frame 12 is supported at each horizontal member 11 position. As a result, a three-dimensional lattice forming a quadrangular pyramid having the joint portion 14 of the sheath tube 13 at the top and the bottom face between the adjacent horizontal members 11 is formed continuously in the longitudinal direction of the arch frame 10. Accordingly, the sheath tube 13 is also arranged at a lower end position of the quadrangular pyramid at a predetermined interval. Further, one PC cable 16 as a tension member is inserted so as to continuously connect each sheath tube 13. A cone fixing section 20 having a fixing chuck 21 is provided at an end of the PC cable 16.
The PC cable 16 can be fixed at a predetermined position. Reference numeral 30 indicates a sheet pile plate for directly pressing the tunnel ground G.

A procedure for supporting a tunnel by using the support beam 1 having the structure shown in FIG. 2 will be described with reference to FIGS. First, the PC cable 16 at the lower end of the support beam 1 in the initial state as shown in FIG. 1A is pulled in the direction of arrow A by a tension jack (not shown). Then, the cable is fixed in the cone fixing section 20 by the amount of tension.
In this process, the adjacent sheath tubes 13 approach each other from the end portions while being pushed by the cone fixing portion 20, and accordingly, an eccentric axial compressive force acts on the arch frame 10. Is curved as a whole. Then, when the curvature of the arch frame 10 becomes larger (smaller radius) than the curvature of the tunnel ground G in the undig state, the support beam 1 is arranged at a predetermined position in the tunnel (see FIG. (B)). In this state, the sheet pile plate 30 is arranged so as to be spread between the inner surface of the tunnel and the arch frame 10, and the support beam 1 is brought into contact with the ground G and the PC cable 16 inserted into the sheath pipe 13 is inserted. The tension of the cone fixing unit 20 is released.

At this time, since the arch frame 10 is curved within the elastic range, the predetermined curved state is released, and the arch frame 10 is elastically deformed so as to return to the initial state shown in FIG. However, both ends of the support beam 1 are located at predetermined positions on the inner surface of the tunnel.
2, the support beam 1 is in close contact with the ground pile G so as to press the sheet pile plate 30 from the inside as shown in FIG. Thus, the support beam 1 functions as an arch support that exerts an internal pressure effect on the tunnel. Since the internal pressure effect of the support beam 1 is exerted by the deformation behavior of the arch frame 10 in the elastic region, the arch frame 10 can be curved to a predetermined curvature, and after the state is restrained and held, the restraint is released. If removed, the material is not limited to fiber reinforced plastic as long as it can be restored to the initial state again by elastic deformation. Various metal plates and resin molded products can be used. It goes without saying that various cross-sectional shapes such as a flat plate can be adopted.

FIG. 4 shows an example in which a support beam 1 is used as a support for a circular section tunnel. As shown in the figure, the circular cross section is supported by three-piece support beams 1, and each support beam 1 is connected to a joint bolt (not shown) via a joint plate 23 provided at an end portion in advance. To form a closing ring as a whole.

In FIG. 1, the sheet pile plate 30 disposed between the tunnel ground and the arch frame 10 is not shown, but as shown in FIG. 12 to face plate frame 2
It is also possible to attach directly to 5. As a result, the tunnel ground G is used only with the support beam 1 without using the sheet pile plate 30.
Can be applied to apply an internal pressure to the tunnel. In this case, it is preferable to use a material equivalent to the arch frame 10 as the material of the face plate frame 25.
In addition, if the ground surface of the tunnel is roughened by excavation in the state shown in FIG. 4, a gap may be generated between the sheet pile plate 30 or the face plate frame 25 and the ground. In such a case, it is preferable that backfilling is performed from a predetermined position of the sheet pile plate 30 or the face plate frame 25, and the generated gap is filled with the filling material.

FIG. 5 is a vertical sectional view of a tunnel schematically showing a state where the tunnel excavation by the TBM 40 is performed. As shown in the figure, the sheet pile plate 30 is arranged at the tunnel base exposed at the rear of the TBM 40, and the support beam 1 presses the sheet pile plate 30 from the inside of the tunnel. Thus, the internal pressure can be applied to the ground, and the loosening of the ground after passing through the TBM 40 can be minimized. Further, from the rear, a second lining concrete 41 is provided by a centre (not shown).
Has been constructed. In this case, as shown in the figure, concrete may be cast so as to bury the entire support beam 1, or the spacer frame 12 and the sheath pipe 13 may be removed and the arch pressing the sheet pile plate 30. Concrete casting may be performed so that only the frame 10 is buried.

FIG. 6 is a partially enlarged cross-sectional view showing a state in which the sheet pile plate 30 is pressed by the support beam 1 to achieve close contact with the ground G. The sheet pile plate 30 is pressed in the direction shown by the arrow by the arch frame 10 of the support beam 1 in a curved state, and the close contact with the ground is achieved. As a result, the ground G is subjected to the internal pressure, and the already loose ground is pushed back to reduce the load due to the looseness, and it is possible to minimize future loosening of the ground.

FIG. 7 is a tunnel sectional view showing an example in which the support beam 1 is applied to tunnel excavation by an advanced shaft. As shown in the figure, the support beam 1 is used as a support for the upper half of the tunnel with the advanced shaft abutment 42 constructed in advance as a fulcrum. Since the arch frame 10 in the curved state is pressed so as to be in close contact with the ground in the upper half of the tunnel, a ground arch in a three-axis constrained state is formed near the open surface of the ground, and the loosening that has already occurred is pushed back. And the subsequent loosening is reliably prevented.

The tunnel to which the support beam 1 can be applied is not limited to the tunnel excavation method described above. Even when excavating a shaft or the like, deformation of the tunnel section due to lateral pressure can be prevented, and partial reinforcement of the NATM can be achieved. It can also be used to prevent deformation of shield segments and construction. In addition, it can be additionally used in support after tunnel excavation to exert an internal pressure effect on the tunnel ground. The structure for bending the member corresponding to the arch frame 10 or the face plate frame 25 is the same as the solid lattice and the PC shown in FIGS.
The configuration is not limited to the combination of the cables 16, and any configuration can be adopted as long as the configuration can maintain a predetermined eccentric position with respect to the position of the arch frame 10 and introduce an axial force.

[0025]

As is apparent from the above description, according to the present invention, since the support can be performed while applying the internal pressure to the tunnel ground, it is effective as a tunnel lining and actively loosens the ground. Thus, there is an effect that high security of the tunnel can be maintained.

[Brief description of the drawings]

FIG. 1 is a modified state diagram showing an embodiment of a tunnel support structure according to the present invention.

FIG. 2 is a partial perspective view showing an example of a support beam of the present invention.

FIG. 3 is a partial perspective view showing a modified example of the support beam shown in FIG. 2;

FIG. 4 is a tunnel cross-sectional view showing an example in which a shoring beam is applied to a circular cross-section tunnel.

FIG. 5 is a longitudinal sectional view of a tunnel showing an example in which a shoring beam is applied as a TBM shoring.

FIG. 6 is a partially enlarged side view showing a support state of the ground by the support beam.

FIG. 7 is a tunnel cross-sectional view showing an example in which a shoring beam is applied to the upper half of an advanced tunnel.

FIG. 8 is a tunnel load diagram schematically showing an example of a load state acting on the upper half of the tunnel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support beam 10 Arch frame 12 Spacer frame 13 Sheath tube 16 PC cable 20 Cone fixing part 25 Face plate frame 30 Sheet pile plate

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tatsuo Goto 2, Tobanjima Construction, Sanbancho, Chiyoda-ku, Tokyo, Japan (72) Inventor Masao Fukuda 2, Sanbancho, Chiyoda-ku, Tokyo Tobishima Construction, Inc. 56) References JP-A-1-131798 (JP, A) JP-A-52-130941 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21D 11/18-11/26

Claims (2)

(57) [Claims] An elastic arch member is brought into contact with an inner surface of a tunnel in a state of being curved and constrained to release a curb restriction of the elastic arch member, and a restoring elastic deformation operation of the elastic arch member is constrained at an inner surface position of the tunnel. A tunnel supporting method, wherein an inner surface of the tunnel is pressed to suppress loosening of the ground of the tunnel. 2. An elastic arch member, and a tension wire holding member disposed along a longitudinal direction of the elastic arch member at a predetermined eccentric distance via a spacer member attached to the elastic arch member. A tension wire inserted and supported by the tension wire holding member, and a tension wire provided with a fixing portion at both ends, and the elastic arch member is curved by introducing tension to both ends of the tension wire. And tunnel support members.