JP2022028077A - Inverted construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverted construction method for suppressing floating-up of an in-service underground.

SOLUTION: In an inverted construction method, a structure 20 is constructed inside an earth-retaining wall 32 adjacent to an in-service underground structure 16 in plan view. A structural body 40 for a base having a floor part 40A arranged on the in-service underground structure 16 side in relation to the earth-retaining wall 32 is connected to a ground structural body 20B of the structure 20 supported by permanent steel columns 22 inside the earth-retaining wall 32 by a temporary diagonal beam 70, and soil 12 under an underground structural body 20A is excavated, while suppressing floating-up of the structural body 40 for the base by using a reaction force to the ground structural body 20B.

SELECTED DRAWING: Figure 4

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a reverse striking method.

A measuring method for measuring the amount of uplift (uplift amount) of the ground around the excavated area when excavating the ground is known (see, for example, Patent Document 1).

Further, there is known a method of constructing a mountain retaining wall under an underground structure in service (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-082676 Japanese Unexamined Patent Publication No. 8-028197

By the way, when the ground next to the underground structure in service is excavated or the existing underground structure next to the underground structure in service is dismantled in a plan view, the excavated area or the dismantled area and the ground around it become It may come up. As a result, the underground structure in service may also be lifted, and the underground structure in service may be affected.

In consideration of the above facts, an object of the present invention is to suppress the floating of an underground structure in service.

The floating suppression structure according to the first aspect has a mountain retaining wall adjacent to the in-service underground structure and a floor portion in a plan view, and is arranged on the in-service underground structure side with respect to the mountain retaining wall. It includes a base structure and an anchor member that extends downward from the base structure and is fixed to a support layer of the ground.

According to the floating suppression structure according to the first aspect, the base structure has a floor portion. This base structure is arranged on the side of the underground structure in service with respect to the retaining wall adjacent to the underground structure in service in a plan view. Further, the anchor member extends downward from the base structure and is fixed to the support layer of the ground.

As a result, the floor of the base structure pushes down the ground on the side of the underground structure in service of the retaining wall, and the ground is compressed. In other words, prestress is introduced into the ground on the side of the underground structure during operation of the retaining wall.

Here, for example, if the ground on the opposite side of the underground structure in service is excavated with respect to the retaining wall, the excavated area and the ground around the excavated area may be lifted. As a result, the underground structure in service may rise.

On the other hand, in this embodiment, as described above, the floor portion of the base structure compresses the ground on the side of the underground structure in service of the retaining wall. As a result, the floor portion of this base structure suppresses the floating of the ground on the side of the underground structure in service of the retaining wall. Therefore, the floating of the underground structure during operation is suppressed.

Further, for example, by using an existing structure as the base structure, the construction man-hours can be reduced.

The floating suppression structure according to the second aspect is the floating suppression structure according to the first aspect, in which the floor portion is arranged around the retaining wall side of the underground structure in service.

According to the floating suppression structure according to the second aspect, the floor portion of the base structure is arranged around the retaining wall side of the underground structure in service. As a result, for example, when excavating the ground on the opposite side of the in-service underground structure to the retaining wall, the floor of the base structure causes the ground around the in-service underground structure on the retaining wall side. Lifting is suppressed. Therefore, the floating of the underground structure during operation is further suppressed.

The reverse driving method according to the third aspect is a reverse driving method in which a structure is constructed inside a mountain retaining wall adjacent to an in-service underground structure in a plan view, and the in-service underground structure is applied to the mountain retaining wall. A base structure having a floor portion arranged on the object side and the structure of the structure supported by the structural pillar inside the retaining wall are connected by a restraining member, and a reaction force is applied to the structure. The ground under the structure is excavated while suppressing the lifting of the base structure.

According to the reverse striking method according to the third aspect, the base structure has a floor portion. The floor is arranged on the side of the underground structure in service with respect to the retaining wall adjacent to the underground structure in service in a plan view.

On the other hand, the structure of the structure is supported by the Shinbashira inside the retaining wall. This structure and the base structure are connected by a restraining member, and the ground under the structure is excavated while suppressing the lifting of the base structure by applying a reaction force to the structure.

As a result, when the ground under the structure is excavated, the floor of the base structure suppresses the floating of the ground on the side of the underground structure in service. Therefore, the floating of the underground structure during operation is suppressed.

As described above, according to the present invention, it is possible to suppress the floating of the underground structure in service.

It is a vertical sectional view which shows the ground to which the floating suppression structure which concerns on 1st Embodiment is applied. It is a vertical cross-sectional view which shows the state which the structure was constructed on the ground to which the floating suppression structure which concerns on 1st Embodiment was applied. It is a vertical cross-sectional view which shows the ground to which the modification of the floating suppression structure which concerns on 1st Embodiment is applied. It is a vertical cross-sectional view which shows the structure under construction to which the reverse driving method which concerns on 2nd Embodiment was applied. It is a vertical sectional view corresponding to FIG. 4 which shows the modification of the reverse driving method which concerns on 3rd Embodiment.

(First Embodiment)
First, the first embodiment will be described.

FIG. 1 shows the ground 12 to which the floating suppression structure 10 according to the present embodiment is applied. An underground structure 16 in service is provided on the ground 12. The underground structure 16 in service is, for example, a railway (subway) or a road that is in operation, and is buried in the ground 12 (underground).

It is sufficient that at least a part of the underground structure 16 in service is buried in the ground 12.

(Structure)
As shown in FIG. 2, in the present embodiment, the ground 12 (excavation area R) next to the underground structure 16 in service is excavated and the structure 20 is constructed (constructed). The structure 20 is composed of a plurality of layers. Further, the structure 20 includes a plurality of columns 22, a plurality of beams 24 erected on adjacent columns 22, and a floor slab 26 supported by the beams 24.

The pillar 22 inside the structure 20 is supported by the pile 21 for the structural pillar, and the pillar 22 on the outer periphery of the structure 20 is supported by the retaining walls 30 and 32, which will be described later.

The structure 20 has an underground structure 20A provided in the ground 12 and an above-ground structure 20B provided on the ground. The underground structure 20A is provided in the excavation area R of the ground 12. Further, the above-ground structure 20B is provided on the underground structure 20A.

The underground structure 20A and the above-ground structure 20B may be a single layer. Further, the structure 20 may have at least the underground structure 20A, and the above-ground structure 20B may be omitted. Further, the underground structure 20A and the above-ground structure 20B are examples of structures.

A retaining wall 30 is provided on the outer peripheral portion of the excavation area R of the ground 12. The retaining wall 30 is formed of, for example, soil cement (ground improvement body) or reinforced concrete. Further, the retaining wall 30 is formed in a frame shape, for example, in a plan view so as to surround the excavation area R. Among the retaining walls 30, the floating suppression structure 10 according to the present embodiment is applied to the retaining wall 32 on the side of the underground structure 16 in service.

(Floating suppression structure)
The floating suppression structure 10 includes a retaining wall 32, a base structure 40, and an anchor member 50. The retaining wall 32 is arranged adjacent to the underground structure 16 in service in a plan view. Further, the retaining wall 32 is arranged so as to face the underground structure 16 in service. A base structure 40 is arranged on the side of the underground structure 16 in service with respect to the retaining wall 32.

(Structure for base)
The base structure 40 is arranged, for example, along the wall surface 32S on the side of the in-service underground structure 16 of the retaining wall 32. The base structure 40 is not joined to the retaining wall 32 and is cut off from the retaining wall 32.

The base structure (base underground structure) 40 is, for example, made of reinforced concrete, and is formed in the ground 12S on the side of the in-service underground structure 16 of the retaining wall 32. Further, the vertical cross-sectional shape of the base structure 40 is formed in an L shape. The base structure 40 has a floor portion 40A and a wall portion 40B.

The floor portion 40A is, for example, a foundation slab or a foundation bottom, and is arranged along the excavation bottom K of the ground 12S. The floor portion 40A is arranged around the retaining wall 32 side of the underground structure 16 in service in a vertical cross-sectional view (vertical cross-sectional view). Further, the floor portion 40A is arranged above the center C of the underground structure 16 in service. A wall portion 40B is provided at an end portion of the floor portion 40A opposite to the retaining wall 32.

It should be noted that the vicinity of the in-service underground structure 16 is, for example, close to the in-service underground structure 16 according to the guideline to which the owner or the manager of the in-service underground structure 16 complies. It means the case of "3 ▼)" or the like, or the case of "proximity mountain retaining" or the like when viewed from the new structure (structure 20).

The "restricted range (▲ 3 ▼)" is the range in which the construction of a new structure is considered to have harmful effects such as displacement and deformation on the existing structure ("Proximity construction of urban railway structures"). Countermeasure Manual "p.24, p68, Fig. 3.6.6, Table 3.6.3, Railway Research Institute, January 2007).

In addition, for "proximity retaining", it is considered to set an allowable value for the displacement amount of the retaining wall or the inclination angle / displacement amount of the adjacent structure at the time of the retaining plan so as not to adversely affect the adjacent structure. This is the case (“Mountain Retention Design Guideline” p.64, p.67, Fig. 3.6.1, Table 3.6.1, Architectural Institute of Japan, published in November 2017).

The wall portion 40B is raised from the end portion of the floor portion 40A. Further, the wall portion 40B functions as a retaining wall, and the wall portion 40B secures an underground space on the floor portion 40A. Further, the floor portion 40A is provided with an anchor member 50.

(Anchor member)
The anchor member 50 is an earth anchor or a ground anchor that extends downward from the floor portion 40A and is fixed to the support layer 14 of the ground 12S. The anchor member 50 has a tension wire 52 and a fixing body 54.

The tension wire 52 is formed of, for example, a PC steel wire or a PC steel rod, and is inserted into an excavation hole formed in the ground 12S. Further, one end (lower end) of the tension wire 52 reaches the support layer 14 of the ground 12S. A fixing body 54 is provided at one end of the tension wire 52.

The anchor body 54 is formed, for example, by filling the excavation hole formed in the support layer 14 of the ground 12S with grout, mortar, or the like. By fixing one end of the tension wire 52 to the fixing body 54, one end of the tension wire 52 is fixed to the support layer 14.

The other end (upper end) of the tension wire 52 is fixed to the floor 40A by a fixture such as a nut or a wedge (not shown). Further, a tensile force (tension force) is introduced into the tensile wire rod 52. As a result, the excavation bottom K of the ground 12S is pushed down by the floor portion 40A, and the ground 12S is held in a compressed state.

(Construction method of floating suppression structure)
Next, the effect of this embodiment will be described while explaining an example of the construction method of the floating suppression structure 10.

First, a frame-shaped retaining wall 30 is constructed along the outer peripheral portion of the excavation area R of the ground 12.

Next, the ground 12S outside the mountain retaining wall 32 on the side of the in-service underground structure 16 of the retaining wall 30, that is, the ground 12S on the side of the in-service underground structure 16 of the retaining wall 32 is excavated and used as the excavated bottom K. The base structure 40 is constructed.

Next, an anchor member 50 that reaches the support layer 14 of the ground 12S is constructed under the floor portion 40A of the base structure 40, and the floor portion 40A is fixed to the support layer 14 of the ground 12S via the anchor member 50. .. At this time, a tensile force is applied to the tension wire 52 of the anchor member 50.

Next, as shown in FIG. 1, an excavation area R opposite to the in-service underground structure 16 is excavated with respect to the ground 12 inside the retaining wall 32, that is, the retaining wall 32.

Here, as shown by the two-dot chain line L1 in FIG. 1, when the excavation region R of the ground 12 is excavated, there is a possibility that the root cutting bottom R1 of the excavation region R and the ground 12 around the excavation region R will be lifted. Then, when the ground 12 around the excavation area R is lifted, the underground structure 16 in service may be lifted.

As a countermeasure for this, in the present embodiment, the base structure 40 is provided on the ground 12S on the side of the underground structure 16 in service with respect to the retaining wall 32. The base structure 40 has a floor portion 40A. The floor portion 40A is fixed to the support layer 14 of the ground 12S via the anchor member 50. Further, a tensile force is applied to the tension wire 52 of the anchor member 50.

As a result, the excavation bottom K of the ground 12S is pushed down by the floor portion 40A, and the ground 12S is held in a compressed state. Therefore, when the excavation area R inside the retaining wall 32 is excavated, the floor portion 40A of the base structure 40 suppresses the floating of the ground 12S on the side of the underground structure 16 in service of the retaining wall 32.

More specifically, by binding the floor portion 40A of the base structure 40 and the fixing body 54 with a tensile wire rod 52 to which a tensile force is applied, the tensile force inherent in the tensile wire rod 52 acts from the floor portion 40A to the ground 12S. Then, the ground 12S is in a state where a compressive force is applied (prestress). Due to this compressive force, the floating of the ground 12S on the side of the underground structure 16 in service of the retaining wall 32 is suppressed. Therefore, the floating of the underground structure 16 in service is suppressed.

Further, the floor portion 40A of the base structure 40 is arranged around the retaining wall 32 side of the underground structure 16 in service. As a result, for example, when the excavation area R inside the retaining wall 32 is excavated, the floor portion 40A of the base structure 40 raises the ground 12S around the retaining wall 32 side of the underground structure 16 in service. It is suppressed. Therefore, the floating of the underground structure 16 in service is further suppressed.

Further, the base structure 40 is not joined to the retaining wall 32 and is cut off from the retaining wall 32. As a result, the tensile force introduced into the tension wire 52 of the anchor member 50 is suppressed from being transmitted to the retaining wall 32 via the base structure 40. Therefore, damage to the retaining wall 32 and the like are suppressed.

(Modified example of the first embodiment)
Next, a modified example of the first embodiment will be described.

In the above embodiment, the base structure 40 is newly installed, but the above embodiment is not limited to this. The base structure may be, for example, an existing structure (underground structure). In this case, the man-hours for constructing the base structure can be reduced.

Further, as in the modified example shown in FIG. 3, when the depth of the underground structure 16 in service is deep, the ground improvement body 60 may be formed under the floor portion 40A of the base structure 40. The ground improvement body 60 is formed in a columnar or wall shape by, for example, soil cement. The lower end portion 60L of the ground improvement body 60 is arranged around the retaining wall 32 side of the underground structure 16 in service.

As a result, the floor portion 40A of the base structure 40 and the ground improvement body 60 suppress the floating of the ground 12S on the side of the in-service underground structure 16 of the retaining wall 32.

(Second embodiment)
Next, the second embodiment will be described. In the second embodiment, the members and the like having the same configuration as that of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

In the second embodiment, as shown in FIG. 4, the structure 20 is constructed by the reverse striking method. At this time, by connecting the base structure 40 and the structure 20 by a temporary inclined beam 70, the floating of the base structure 40 is suppressed. The temporary inclined beam 70 is an example of a restraining member.

Specifically, first, the retaining wall 30 is constructed along the outer peripheral portion of the excavation area R of the ground 12.
Next, the base structure 40 is constructed on the ground 12S on the side of the in-service underground structure 16 of the retaining wall 32. The base structure 40 of the present embodiment is not provided with the anchor member 50 (see FIG. 1).

Next, a plurality of structural shinbashira piles 21 are constructed below the root cutting bottom R1 of the excavation area R, and the structural shinbashira 22 is placed on each structural shinbashira pile 21.

Next, the excavation area R is excavated to a predetermined depth (primary excavation). Next, the beam 24 and the floor slab 26 on the first floor of the structure 20 (ground structure 20B) are constructed. The beam 24 and the floor slab 26 on the first floor of the structure 20 are supported by a plurality of structural pillars (pillars) 22. Further, the beam 24 and the floor slab 26 on the first floor of the structure 20 function as a timbering support for supporting the retaining wall 32.

Next, the excavation area R is excavated to a predetermined depth (secondary excavation), and the underground structure 20A is sequentially constructed. Further, in parallel with the construction of the underground structure 20A, the above-ground structure 20B will be sequentially constructed. Specifically, the pillar 22 on the first floor of the ground structure 20B is constructed on the plurality of structural pillars 22, and the beam 24 and the floor slab 26 on the second floor of the ground structure 20B are constructed.

Next, a temporary inclined beam 70 is erected on the second floor beam 24 of the ground structure 20B and the floor portion 40A of the base structure 40, and the temporary inclined beam 70 is used to construct the second floor beam 24 and the floor portion of the base structure 40. Connect with 40A. The temporary inclined beam 70 is provided with a jack 72 for expanding and contracting the temporary inclined beam 70. Further, on the floor portion 40A of the base structure 40, a base member 76 that is inclined according to the inclination angle of the temporary inclined beam 70 and supports the temporary inclined beam 70 is provided.

Next, with the second-floor beam 24 and the floor portion 40A of the base structure 40 connected by the temporary inclined beam 70, the ground 12 under the underground structure 20A is excavated to the root cutting bottom R1 (tertiary excavation). , Underground structure 20A will be constructed sequentially up to the lowest floor. Further, in parallel with the construction of the underground structure 20A, the above-ground structure 20B will be sequentially constructed. After that, the temporary inclined beam 70 is removed. It is preferable that the temporary inclined beam 70 is removed after the underground structure 20A is constructed to the lowest floor.

Here, if the excavation area R is gradually excavated, the excavation area R and the ground 12 around the excavation area R may be lifted. Then, when the ground 12 around the excavation area R is lifted, the underground structure 16 in service may be lifted.

On the other hand, in the present embodiment, as described above, the structure 20 is constructed by the reverse striking method. As a result, the lift of the excavation area R is suppressed by the weight of the constructed underground structure 20A and the above-ground structure 20B.

Further, in the present embodiment, the ground 12 under the underground structure 20A is excavated in a state where the ground structure 20B and the base structure 40 are connected by a temporary inclined beam 70. More specifically, the underground structure 20A is in a state where the second-floor beam 24 of the above-ground structure 20B supported by the structural pillar 22 and the floor portion 40A of the base structure 40 are connected by a temporary inclined beam 70. Excavate the ground 12 below.

As a result, when the floor portion 40A of the base structure 40 tries to rise, the temporary inclined beam 70 exerts a reaction force on the ground structure 20B to suppress the lifting of the floor portion 40A. Therefore, the floating of the ground 12S on the side of the underground structure 16 in service of the retaining wall 32 is further suppressed.

Further, the temporary inclined beam 70 is provided with a jack 72. Therefore, for example, by operating the jack 72 according to the amount of lifting of the floor portion 40A of the base structure 40 and extending the temporary inclined beam 70, the lifting of the floor portion 40A can be efficiently suppressed.

Moreover, it is not necessary to provide the anchor member 50 (see FIG. 1) on the floor portion 40A by suppressing the lifting of the floor portion 40A of the base structure 40 by the temporary inclined beam 70. Therefore, the man-hours for constructing the anchor member 50 can be reduced.

(Modified example of the second embodiment)
Next, a modified example of the second embodiment will be described.

When the depth of the underground structure 16 in service is deep as in the modified example shown in FIG. 5, the above-mentioned ground improvement body 60 may be provided under the floor portion 40A of the base structure 40.

Further, in the above embodiment, the anchor member 50 is not provided on the floor portion 40A of the base structure 40, but the anchor member 50 may be provided on the floor portion 40A of the base structure 40.

Further, in the above embodiment, the jack 72 is provided on the temporary inclined beam 70, but the jack 72 can be omitted as appropriate. Further, the restraining member is not limited to the temporary inclined beam 70, and may be, for example, another member or the like.

(Modified examples of the first and second embodiments)
Next, modifications of the first embodiment and the second embodiment will be described. In the following, various modifications will be described by taking the first embodiment as an example, but these modifications can be appropriately applied to the second embodiment.

In the first embodiment, the base structure 40 and the retaining wall 32 are not joined, but the base structure 40 and the retaining wall 32 may be joined.

Further, in the first embodiment, the floor portion 40A of the base structure 40 is arranged around the retaining wall 32 side of the underground structure 16 in service. However, the floor portion 40A of the base structure 40 may be arranged outside the periphery of the underground structure 16 in service on the premise that the suppressing effect can be exhibited.

Further, in the first embodiment, the excavation area R next to the underground structure 16 in service is excavated, but the embodiment is not limited to this. The above embodiment can also be applied to, for example, the case of dismantling an existing underground structure (existing underground structure) adjacent to the underground structure 16 in service.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modifications may be used in combination as appropriate. Of course, it can be carried out in various embodiments as long as it does not deviate.

12 Ground 16 In-service underground structure 20 Structure 20A Underground structure (structure of structure)
20B ground structure (structure of structure)
22 Structure Shinbashira 32 Mountain retaining wall 40 Base structure 40A Floor 70 Temporary slanted beam (suppressing member)
72 jack

Claims (3)

It is a reverse-strike method in which the structure is constructed inside the retaining wall adjacent to the underground structure that is in service in a plan view.
A member that suppresses a base structure having a floor portion arranged on the side of the underground structure in service with respect to the retaining wall and a structure of the structure supported by a structural pillar inside the retaining wall. The ground under the structure is excavated while the reaction force is applied to the structure to suppress the lifting of the base structure.
Reverse striking method. The floor portion is arranged around the retaining wall side of the underground structure in service.
The reverse striking method according to claim 1. The restraining member is provided with a jack that expands and contracts the restraining member.
The jack is operated according to the amount of lifting of the floor portion, and the restraining member is extended.
The reverse striking method according to claim 1 or 2.

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