Method for controlling uplift of existing underground structure and method for constructing underground structure

Abstract

To construct a new underground structure while minimizing the impact of a construction of a new underground structure on an existing underground structure.SOLUTION: A method for controlling uplift of an existing underground structure 91 includes a step S1 of driving anchor bodies 21 to generate a force resisting uplift of the existing underground structure 91, a step S2 of constructing girder shafts 12A, 12B to expose a top surface 91a of the existing underground structure 91, a step S3 of placing a reaction girder 3 on the top surface 91a of the existing underground structure 91 exposed from the girder shafts 12A, 12B, steps S41 and S42 of attaching fixing devices 4 to top surfaces of the reaction girders 3, respectively, for applying a vertical downward reaction force generated by the action of pulling wires 22 to each of the reaction girders 3, and a step S43 of applying a vertical downward reaction force (tension force) to each of the pair of reaction girders 3 by performing an action of pulling the pair of wires 22 with the fixing devices 4.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for controlling the uplift of an existing underground structure and a method for constructing an underground structure. [Background technology]

[0002] Structures buried underground, such as shield tunnels, are subjected to forces from the surrounding ground. These forces include forces that push the structure vertically upwards and forces that push the structure vertically downwards. When the balance of these forces acting on a structure is balanced, the structure is in a stable state.

[0003] However, the balance of these forces may be disrupted due to some factor. For example, if the force pushing the structure vertically upward becomes greater than the force pushing the structure vertically downward, the structure will tend to rise up. Patent Documents 1 to 3 disclose techniques for suppressing such uplift of the structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2-261604 [Patent Document 2] Japanese Patent Application Publication No. 9-303082 [Patent Document 3] Patent No. 6744638 Summary of the Invention [Problem to be solved by the invention]

[0005] Assume that there is an existing structure (hereinafter referred to as "existing underground structure") installed underground, and the existing underground structure maintains a balance of forces it receives from its surroundings. A new underground structure (hereinafter referred to as "new underground structure") may be constructed near such an existing underground structure. The forces acting on the existing underground structure are affected by the ground surrounding the existing underground structure. When constructing a new underground structure, the ground surrounding the existing underground structure is excavated, etc., which brings about a change in the condition of the ground surrounding the existing underground structure. As a result, a change occurs in the balance of forces acting on the existing underground structure, which may result in the existing underground structure moving or deforming.

[0006] The present invention provides a method for controlling the uplift of an existing underground structure in order to construct a new underground structure while suppressing the impact on the existing underground structure caused by the construction of the new underground structure, and a construction method for the new underground structure. [Means for solving the problem]

[0007] A method for controlling the uplift of an existing underground structure, which is one form of the present invention, comprises the steps of providing at least a pair of pull-out resistance members that are arranged to sandwich the existing underground structure and generate a force that resists the uplift of the existing underground structure; providing at least a pair of vertical shafts that contain a pair of pulling portions connected to each of the pair of pull-out resistance members and expose the top surface of the existing underground structure; placing a reaction member on the top surface of the existing underground structure exposed from the pair of vertical shafts; attaching at least a pair of fixing devices that are installed on the reaction members and apply a vertical downward reaction force generated by the action of pulling the pair of pulling portions to the reaction members; and applying a vertical downward reaction force to each of the reaction members by performing the action of pulling the pair of pulling portions with the pair of fixing devices.

[0008] According to this method, a vertical downward force can be applied to the existing underground structure by the pull-out resistance member, the tensioning portion, the reaction member, and the fixing device. The magnitude of the vertical downward force applied to the existing underground structure can be controlled by controlling the action of the pair of fixing devices to pull the tensioning portions. In other words, even if the balance of forces acting on the existing underground structure changes due to changes in the surrounding environment of the existing underground structure caused by the construction of the new underground structure, a force to maintain the balance can be applied to the existing underground structure. As a result, the new underground structure can be constructed while suppressing the impact on the existing underground structure caused by the construction of the new underground structure.

[0009] In one embodiment, the reaction member is a reaction girder extending from a first shaft of one of a pair of shafts to a second shaft of the other, and in the step of placing the reaction member, the reaction member may be placed so that a first end of the reaction girder is exposed from the first shaft and a second end of the reaction girder is exposed from the second shaft. This reaction member can suitably apply a vertical downward force to the existing underground structure.

[0010] In one embodiment, the reaction girder is formed by connecting a plurality of girder members to each other, and the step of placing the reaction members may repeat the steps of introducing the girder member from the first shaft, connecting the introduced girder member to the end of the girder member exposed in the first shaft, and pushing the connected girder member from the first shaft toward the second shaft. This step allows the reaction member to be provided according to the width of the existing underground structure without constructing holes for bridging the reaction member.

[0011] In one embodiment, the reaction girder is formed by connecting a plurality of girder members to each other, and the step of arranging the reaction members may include a step of providing a girder pilot tunnel from the first shaft to the second shaft, and after the step of providing the girder pilot tunnel, a step of connecting the introduced girder member to the end of the girder member exposed in the first shaft and a step of pushing the connected girder member from the first shaft toward the second shaft may be repeated. According to this step, by providing a girder pilot tunnel, the reaction members according to the width of the existing underground structure can be easily provided.

[0012] In one embodiment, the reaction member may include a first girder frame and a second girder frame that are separate from each other, and the step of arranging the reaction member may include a step of arranging the first girder frame on a top surface of the existing underground structure exposed from a first shaft of one of the pair of shafts, and a step of arranging the second girder frame on a top surface of the existing underground structure exposed from a second shaft of the other of the pair of shafts. According to this step, a vertical downward force can be applied to the existing underground structure without bridging the reaction member from the first shaft to the second shaft.

[0013] Another embodiment of the present invention relates to a method for constructing an underground structure, the method comprising the steps of: providing at least a pair of pull-out resistance members arranged to sandwich an existing underground structure and for generating a force resisting uplift of the existing underground structure; providing at least a pair of vertical shafts containing a pair of pulling parts connected to each of the pair of pull-out resistance members and exposing the top surface of the existing underground structure; arranging reaction members on the top surface of the existing underground structure exposed from the pair of vertical shafts; and providing at least a pair of reaction members arranged on the reaction members for applying a vertical downward reaction force generated by the action of pulling the pair of pulling parts to the reaction members. The method includes the steps of attaching at least a pair of fixing devices, applying a vertical downward reaction force to each of the reaction members by performing an operation of pulling the pair of pulling portions with the pair of fixing devices, and constructing a new underground structure, wherein the process of constructing a new underground structure includes the steps of excavating the ground above the existing underground structure, checking the degree of uplift of the existing underground structure, and keeping the degree of uplift of the existing underground structure within a predetermined range by adjusting the degree to which the pair of fixing devices pull the pair of pulling portions in accordance with the degree of uplift of the existing underground structure.

[0014] This construction method includes the above-mentioned method for controlling the upheaval of the existing underground structure, and therefore it is possible to construct a new underground structure while suppressing the upheaval of the existing underground structure. Effect of the Invention

[0015] According to the present invention, a method for controlling the uplift of an existing underground structure in order to construct a new underground structure while suppressing the impact on the existing underground structure caused by the construction of the new underground structure, and a construction method for the new underground structure are provided. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a new underground structure and an existing underground structure constructed by applying a method for controlling uplift of an existing underground structure and a method for constructing an underground structure according to an embodiment. [Diagram 2]FIG. 2 is a flow chart showing the main steps of the method for controlling the uplift of an existing underground structure and the method for constructing an underground structure. [Diagram 3] FIG. 3 is a perspective view for explaining the process of driving a ground anchor. [Figure 4] FIG. 4 is a perspective view for explaining the process of constructing a girder shaft. [Diagram 5] FIG. 5 is a perspective view for explaining the process of installing the reaction girder. [Figure 6] FIG. 6 is a perspective view for explaining the process of fixing the ground anchor. [Figure 7] FIG. 7 is a perspective view for explaining a part of the process of constructing a new underground structure. [Figure 8] FIG. 8 is a perspective view for explaining the remaining part of the process of constructing the new underground structure. [Figure 9] FIG. 9 is a perspective view showing the state in which a girder frame used in the modified method for controlling the uplift of an existing underground structure and the modified method for constructing an underground structure is installed. [Figure 10] FIG. 10 is a flow chart showing main steps of a modified method for controlling uplift of an existing underground structure and a modified method for constructing an underground structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted.

[0018] 1 shows an underground structure constructed using the method for controlling the uplift of an existing underground structure 91 and the method for constructing an underground structure of this embodiment. An existing underground structure 91 and a new underground structure 92 are buried below a ground surface 90. The method for controlling the uplift of an existing underground structure 91 and the method for constructing an underground structure of this embodiment are used to construct a new underground structure 92 on top of the existing underground structure 91.

[0019] The so-called cut-and-cover method can be used as a method for establishing a new underground structure 92 on an existing underground structure 91. According to the cut-and-cover method, first, an area where the new underground structure 92 will be established is excavated above the existing underground structure 91. Next, the new underground structure 92 is established in the excavated area. Then, the new underground structure 92 is backfilled.

[0020] A certain amount of buoyancy acts on the existing underground structure 91 before excavation, i.e., while it is buried, and this buoyancy causes the existing underground structure 91 to move vertically upward. Meanwhile, the existing underground structure 91 is subjected to a vertically downward force caused by the mass of the ground above. Therefore, while buried, the existing underground structure 91 is constantly subjected to vertically upward and vertically downward forces, and maintains its position by maintaining a balance between these forces.

[0021] Then, when the ground above the existing underground structure 91 is excavated during construction of the new underground structure 92, the vertical downward force acting on the existing underground structure 91 is reduced. As a result, the existing underground structure 91 may rise vertically upward.

[0022] On the other hand, the existing underground structure 91 is required to remain in a specified position from the time of excavation until the new underground structure 92 is backfilled. More specifically, an allowable displacement is set for the existing underground structure 91 during the construction of the new underground structure 92. During the construction of the new underground structure 92, the displacement of the existing underground structure 91 needs to be kept within this allowable range. Therefore, during the period when the new underground structure 92 is being constructed, it was necessary to control the amount of uplift of the existing underground structure 91 so that it would fall within the allowable range.

[0023] Examples of techniques for controlling the amount of uplift of the existing underground structure 91 include the partial excavation method, the counterweight method, and the groundwater level lowering method. However, even with these techniques, it is extremely difficult to keep the amount of uplift of the existing underground structure 91 within an acceptable range. For example, the vertical downward force acting on the existing underground structure 91 gradually decreases as the excavation progresses. In this way, when the force acting on the existing underground structure 91 changes over time, it is difficult with these methods to maintain a balance of the force acting on the existing underground structure 91 so as to follow the change in this force.

[0024] The method for controlling the uplift of an existing underground structure 91 and the method for constructing an underground structure in this embodiment were developed as a result of careful consideration in order to keep the amount of uplift of the existing underground structure 91 within an acceptable range.

[0025] Fig. 2 is a flow chart showing the main steps of the underground structure construction method of this embodiment. Figs. 3 to 8 are perspective views showing the steps shown in the flow chart. Hereinafter, the method for controlling the uplift of an existing underground structure 91 and the underground structure construction method of this embodiment will be described in detail with reference to Figs. 3 to 8.

[0026] Some steps of the underground structure construction method constitute a method for controlling the uplift of an existing underground structure 91. The underground structure construction method includes, as main steps, a step S1 of driving the ground anchors 2, a step S2 of constructing a girder shaft, a step S3 of installing the reaction girder 3, a step S4 of fixing the ground anchors 2 to the reaction girder 3, and a step S5 of constructing a new underground structure 92. Among these, the step S1 of driving the ground anchors 2, the step S2 of constructing the girder shafts 12A, 12B, and the step S3 of installing the reaction girder 3 constitute a method for controlling the uplift of an existing underground structure 91.

[0027] <Step S1 of installing ground anchor 2> First, step S1 is performed to cast the ground anchors 2. As shown in Fig. 2, step S1 of casting the ground anchors 2 includes step S11 of constructing anchor holes 11A, 11B and step S12 of casting the ground anchors 2.

[0028] As shown in Fig. 3, first, a plurality of anchor holes 11A, 11B are constructed (S11). The plurality of anchor holes 11A, 11B are for providing anchor bodies 21 for generating a force to resist the uplift of an existing underground structure 91. The anchor holes 11A, 11B are provided along the width direction Y of the existing underground structure 91 so as to sandwich the existing underground structure 91. The pair of anchor holes 11A, 11B are provided at a predetermined interval along the extension direction X of the existing underground structure 91.

[0029] The anchor holes 11A and 11B have an anchor hole bottom surface. The position of the anchor hole bottom surface is, for example, lower in the vertical direction than the existing underground structure 91. In other words, the position of the anchor hole bottom surface is provided at a position deeper than the existing underground structure 91. Furthermore, the anchor hole bottom surface is provided in the hard ground 93. As a result, the anchor body 21 provided near the anchor hole bottom surface is fixed to the hard ground 93 and can become a starting point for generating a strong reaction force.

[0030] Next, the ground anchor 2 is cast (S12). The ground anchor 2 has an anchor body 21 (pull-out resistance member) and a wire 22 (tension portion). The anchor body 21 is formed of grout or the like, and is fixed to the ground 93. The wire 22 is connected to the anchor body 21. The wire 22, which is the tension portion, is, for example, a PC steel strand. The tension portion may be a PC steel round bar or the like. One anchor body 21 is provided for each of the anchor holes 11A, 11B. One wire 22 is also provided for each of the anchor holes 11A, 11B.

[0031] <Step S2 of constructing girder shafts 12A and 12B> Next, a step S2 of constructing girder shafts 12A and 12B (first shaft and second shaft) is carried out. As shown in FIG. 4, the inner diameter of the anchor shafts 11A and 11B on the ground surface 90 side is enlarged. In other words, the girder shafts 12A and 12B are portions of the anchor shafts 11A and 11B on the ground surface side that have been enlarged in diameter. Therefore, the girder shafts 12A and 12B contain the wires 22 of the ground anchors 2. The girder shaft bottom surfaces 12a of the girder shafts 12A and 12B reach the top surface 91a of the existing underground structure 91. The girder shaft bottom surfaces 12a of the girder shafts 12A and 12B may reach a position deeper than the top surface 91a of the existing underground structure 91. The top surface 91a of the existing underground structure 91 is exposed from the girder shafts 12A and 12B. That is, when viewed from above, the girder shafts 12A, 12B overlap with the existing underground structure 91. On the other hand, when viewed from above, the anchor holes 11A, 11B do not overlap with the existing underground structure 91. Furthermore, when the girder shaft bottom surface 12a reaches a position deeper than the top surface 91a of the existing underground structure 91, the side surface 91b of the existing underground structure 91 is also exposed.

[0032] <Step S3 of installing the reaction girder 3> Next, a step S3 of installing the reaction girder 3 is carried out. As shown in Fig. 2, the step S3 of installing the reaction girder 3 includes a step S31 of constructing a girder pilot hole 15, a step S32 of introducing a girder member 31, a step S33 of connecting the girder member 31, and a step S34 of pushing in the girder member 31.

[0033] As shown in Fig. 5, the reaction girder 3 is a member extending from one girder shaft 12A to the other girder shaft 12B. The reaction girder 3 is disposed on the top surface 91a of the existing underground structure 91. The reaction girder 3 installed in step S3 may be in direct contact with the top surface 91a of the existing underground structure 91. The reaction girder 3 prevents the existing underground structure 91 from rising. In other words, the reaction girder 3 cooperates with the ground anchor 2 and the fixing device 4 to apply a vertical downward force to the existing underground structure 91.

[0034] The length of the reaction girder 3 is longer than the width of the existing underground structure 91. Therefore, one end of the reaction girder 3 and the other end of the reaction girder 3 protrude from the side surface 91b of the existing underground structure 91. One end of the reaction girder 3 is exposed inside one girder shaft 12A. The other end of the reaction girder 3 is exposed inside the girder shaft 12B.

[0035] As described above, the reaction girder 3 is longer than the width of the existing underground structure 91. In other words, the length of the reaction girder 3 is longer than the inner diameter of the girder shafts 12A and 12B. Therefore, the reaction girder 3 is divided into several girder members 31, and one reaction girder 3 is formed by joining the girder members 31.

[0036] First, a girder pilot tunnel is constructed (S31). The girder pilot tunnel 15 is a hole that penetrates from one girder shaft 12A to the other girder shaft 12B. One opening of the girder pilot tunnel 15 is formed on the inner wall surface of one girder shaft 12A. The other opening of the girder pilot tunnel 15 is formed on the inner wall surface of the other girder shaft 12B that exists on the opposite side of the existing underground structure 91. The girder pilot tunnel 15 may expose the top surface 91a of the existing underground structure 91. Next, the girder member 31 is introduced (S32). The length of the girder member 31 is smaller than the inner diameter of the girder shafts 12A and 12B. As shown in FIG. 5, the girder member 31 is carried into the girder shafts 12A and 12B from the openings of the girder shafts 12A and 12B by a crane or the like. Next, the girder member 31 is connected (S34). The girder member 31 is added to the rear end of the previously pushed-out girder member 31 by welding or the like. Next, the girder member is pushed into the girder pilot hole 15 (S33). The connected girder member 31 is pushed toward the girder shaft 12B that exists on the opposite side across the existing underground structure 91.

[0037] By repeating this process of introduction (S32), connection (S33), and pushing (S34), a reaction girder 3 is formed extending from one girder shaft 12A to the other girder shaft 12B.

[0038] <Step S4 of fixing the ground anchor 2 to the reaction girder 3> Next, step S4 is carried out to fix the ground anchor 2 to the reaction girder 3. As shown in Fig. 2, step S4 of fixing the ground anchor 2 to the reaction girder 3 includes step S41 of arranging the fixing device 4, step S42 of connecting the ground anchor 2 to the fixing device 4, and step S43 of introducing tension.

[0039] As shown in FIG. 6, first, the fixing device 4 is placed (S41). Specifically, the fixing device 4 is placed on both ends of the reaction girder 3 exposed from the girder shafts 12A and 12B. The fixing device 4 connects the wire 22 of the ground anchor 2 to the reaction girder 3. The connection here means that the wire 22 is structured to be capable of transmitting a vertically downward force acting on the wire 22 to the reaction girder 3. The force of the wire 22 is first transmitted to the fixing device 4. Then, the fixing device 4, which receives the vertically downward force acting from the wire 22, presses the upper surface of the reaction girder 3. As a result, the reaction girder 3 can apply a vertically downward force to the existing underground structure 91 that counters the vertically upward force that attempts to lift the existing underground structure 91.

[0040] Next, the ground anchor 2 is connected to the fixing device 4 (S42). Specifically, the wire 22 of the ground anchor 2 is gripped by a gripping mechanism provided in the fixing device 4.

[0041] For example, a through hole is provided in the reaction girder 3, and the wire 22 passes through this through hole from the lower surface to the upper surface of the reaction girder 3. The fixing device 4 is placed on the through hole of the reaction girder 3. That is, the fixing device 4 is in contact with the upper surface of the reaction girder 3. A gripping mechanism provided in the fixing device 4 grips the upper end portion of the wire 22 protruding from the upper surface of the reaction girder 3.

[0042] Then, tension is introduced (S43). The fixing device 4 generates a force that pulls the held wire 22 vertically upward. When the force with which the fixing device 4 pulls the wire 22 increases, the vertically downward force that the fixing device 4 applies to the reaction girder 3 also increases. In other words, the fixing device 4 can control the magnitude of the vertically downward force that the fixing device 4 applies to the reaction girder 3 to be increased or decreased. Therefore, the fixing device 4 may be equipped with a so-called jack mechanism. In step S43, the fixing device 4 pulls the wire 22 by a predetermined length so as to generate a predetermined initial tension.

[0043] By the above steps S1 to S4, a structure for controlling the uplift of the existing underground structure 91 is formed.

[0044] <Process S5 of constructing new underground structure 92> Then, a process S5 is carried out to construct the new underground structure 92. As shown in Fig. 2, the process S5 of constructing the new underground structure 92 includes a process S51 of setting up an earth retaining wall 7, a process S52 of deep excavation, a process S53 of constructing the new underground structure 92, a process S54 of removing the reaction girders 3 and the anchoring devices 4, and a process S55 of backfilling.

[0045] As shown in Fig. 7, first, an earth retaining wall 7 is constructed (S51). The earth retaining wall 7 forms a construction area including an area where a new underground structure 92 is to be constructed. At this time, since the ground above the existing underground structure 91 still exists, a balance is maintained between the vertically upward force and the vertically downward force acting on the existing underground structure 91. In other words, basically, the existing underground structure 91 does not rise.

[0046] Next, deep excavation is performed (S52). As shown in Fig. 7, the ground in the construction area sandwiched between the retaining walls 7 is excavated and removed. This deep excavation gradually reduces the ground present above the existing underground structure 91, causing a change in the balance between the vertically upward force and the vertically downward force acting on the existing underground structure 91. As a result, the existing underground structure 91 is raised.

[0047] Therefore, during the deep excavation (S52a), the amount of uplift is checked (S52b). Then, if necessary, the force with which the anchoring device 4 pulls the wire 22 is adjusted (S52c). Specifically, since the vertical downward force acting on the existing underground structure 91 is reduced by the excavation, the vertical downward force by the anchoring device 4 is increased to compensate for the reduced force.

[0048] The control of the fixing device 4 may be, for example, to monitor the displacement of the existing underground structure 91 using a displacement sensor or the like provided in the existing underground structure 91 (S52b). Then, when it is determined that the displacement of the existing underground structure 91 has exceeded a threshold, the fixing device 4 may be controlled so that the displacement of the existing underground structure 91 becomes equal to or less than the threshold (S52c). Also, a strain gauge may be provided on the reinforcing bars of the existing underground structure 91, and the strain value may be used as a parameter for detecting the amount of uplift.

[0049] Next, as shown in FIG. 8, a new underground structure 92 is constructed (S53). At this time, the operation (S52b, S52c) of controlling the uplift of the existing underground structure 91 by the anchoring device 4, the reaction girder 3, and the ground anchor 2 may be continued. During this period, the vertical downward force acting on the existing underground structure 91 is provided by the reaction girder 3 and the ground anchor 2, so it basically does not change. However, it is considered that the influence of the deep excavation on the surrounding ground will gradually become apparent over time. As a result, the vertical upward force acting on the existing underground structure 91 may change. Therefore, during the period in which the new underground structure 92 is constructed, the anchoring device 4 may be controlled as necessary by monitoring the displacement of the existing underground structure 91.

[0050] Next, the anchoring device 4 and the reaction girder 3 are removed (S54). This step S54 may be performed after it has been confirmed that the construction of the new underground structure 92 will not cause uplift of the existing underground structure 91.

[0051] Then, the new underground structure 92 is backfilled (S55).

[0052] <Action and effect> The method for controlling the uplift of an existing underground structure 91 includes a step S1 of casting at least a pair of anchor bodies 21 that are arranged to sandwich the existing underground structure 91 and generate a force resisting the uplift of the existing underground structure 91; a step S2 of constructing at least girder shafts 12A, 12B that contain a pair of wires 22 connected to each of the pair of anchor bodies 21 and expose the top surface 91a of the existing underground structure 91; a step S3 of arranging a reaction girder 3 on the top surface 91a of the existing underground structure 91 exposed from the girder shafts 12A, 12B; steps S41 and S42 of attaching at least a pair of fixing devices 4 that are installed on the reaction girder 3 and apply a vertical downward reaction force generated by the action of pulling the pair of wires 22 to the reaction girder 3; and a step S43 of applying a vertical downward reaction force to each of the reaction girders 3 by performing the action of pulling the pair of wires 22 with the pair of fixing devices 4.

[0053] Further, the construction method of the new underground structure 92 includes a step S1 of casting at least a pair of anchor bodies 21 arranged to sandwich the existing underground structure 91 and for generating a force resisting the uplift of the existing underground structure 91, a step S2 of constructing at least girder shafts 12A, 12B containing a pair of wires 22 connected to each of the pair of anchor bodies 21 and exposing the top surface 91a of the existing underground structure 91, a step S3 of placing a reaction girder 3 on the top surface 91a of the existing underground structure 91 exposed from the girder shafts 12A, 12B, and a step S4 of placing at least a pair of wires 22 installed on the reaction girder 3 for applying a vertical downward reaction force generated by the action of pulling the pair of wires 22 to the reaction girder 3. The method includes steps S41 and S42 of attaching the fixing devices 4, step S43 of applying a vertical downward reaction force to each of the reaction girders 3 by pulling the pair of wires 22 with the pair of fixing devices 4, and step S5 of constructing a new underground structure.The step S5 of constructing the new underground structure 92 includes a step S52a of excavating the ground above the existing underground structure 91, a step S52b of checking the degree of uplift of the existing underground structure 91, and a step S52c of keeping the degree of uplift of the existing underground structure 91 within a predetermined range by adjusting the degree to which the pair of fixing devices 4 pull the pair of wires 22 in accordance with the degree of uplift of the existing underground structure 91.

[0054] According to these methods, it is possible to apply a vertically downward force to the existing underground structure 91 by the anchor body 21, the wire 22, the reaction girder 3, and the fixing device 4. Then, it is possible to control the magnitude of the vertically downward force applied to the existing underground structure 91 by controlling the operation of the pair of fixing devices 4 to pull the wire 22. As a result, even if the balance of the forces acting on the existing underground structure 91 changes due to a change in the surrounding environment of the existing underground structure 91 caused by the construction of the new underground structure 92, a force for maintaining the balance can be applied to the existing underground structure 91. As a result, it is possible to construct the new underground structure 92 while suppressing the impact on the existing underground structure 91 caused by the construction of the new underground structure 92.

[0055] The reaction member is a reaction girder 3 extending from one of the girder shafts 12A and 12B to the other girder shaft 12B. In step S3 of placing the reaction girder 3, the reaction girder 3 is placed so that a first end of the reaction girder 3 is exposed from the girder shaft 12A and a second end of the reaction girder 3 is exposed from the girder shaft 12B. This reaction girder 3 allows a vertical downward force to be applied to the existing underground structure 91 in an appropriate manner.

[0056] The reaction girder 3 is formed by connecting a plurality of girder members 31 to each other. In step S3 of arranging the reaction girder 3, step S31 of constructing a girder pilot shaft 15 from the girder shaft 12A to the girder shaft 12B is carried out, and after carrying out step S31 of constructing the girder pilot shaft 15, step S32 of connecting the introduced girder member 31 to the end of the girder member 31 exposed to the girder shaft 12A and step S33 of pushing the connected girder member 31 from the girder shaft 12A toward the girder shaft 12B are repeated. According to this step S3, by providing the girder pilot shaft 15, the reaction girder 3 according to the width of the existing underground structure 91 can be easily provided.

[0057] <Variation 1> The method of controlling the uplift of an existing underground structure 91 and the method of constructing an underground structure of the present invention are not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0058] In the embodiment, the reaction member is a girder-shaped member that is laid across the width of the existing underground structure 91 along the top surface 91a. The reaction member is not limited to a girder-shaped member. As shown in Fig. 9, girder frames 8A and 8B that are L-shaped when viewed from the side may be used.

[0059] The girder frames 8A, 8B (first girder frame, second girder frame) have a main body portion 81 and a hook portion 82. The main body portion 81 extends along the wire 22, and the fixing device 4 is placed on its upper surface. The main body portion 81 is provided with a through hole through which the wire 22 passes. The side surface of the main body portion 81 faces the side surface 91b of the existing underground structure 91. The side surface of the main body portion 81 may or may not be in contact with the side surface 91b of the existing underground structure 91. The hook portion 82 extends from the side surface of the main body portion 81 toward the existing underground structure 91. The bottom surface of the hook portion 82 contacts the top surface 91a of the existing underground structure 91.

[0060] <Action and effect> The reaction members include a girder frame 8A and a girder frame 8B which are separate from each other. Step S3A (see FIG. 10) of placing the reaction girder 3 includes step S35 of placing the girder frame 8A on the top surface 91a of the existing underground structure 91 exposed from one of the girder shafts 12A and 12B, the girder shaft 8B, and step S36 of placing the girder frame 8B on the top surface 91a of the existing underground structure 91 exposed from the other of the girder shafts 12A and 12B. According to this step S3A, a vertical downward force can be applied to the existing underground structure 91 without bridging the reaction girder 3 from the girder shaft 12A to the girder shaft 12B.

[0061] <Variation 2> In the embodiment, the new underground structure 92 is perpendicular to the existing underground structure 91. However, when applying the method for controlling the uplift of the existing underground structure 91 and the underground structure construction method of the present invention, the new underground structure 92 may be disposed arbitrarily relative to the existing underground structure 91. For example, the new underground structure 92 may extend obliquely to the existing underground structure 91 in the ground area above the existing underground structure 91, or may extend along the direction in which the existing underground structure 91 extends.

[0062] <Variation 3> In the embodiment, the reaction girder 3 is removed on the condition that it is confirmed that no uplift or the like of the existing underground structure 91 will occur after the construction of the new underground structure 92 is completed. For example, the fixing device 4 is removed, but the reaction girder 3 may be left in place without being removed.

[0063] <Modification 4> In the embodiment, the step S3 of placing the reaction girder 3 includes the step S31 of constructing the girder pilot tunnel 15. The step S31 of constructing the girder pilot tunnel 15 may be omitted. In other words, the step S3 of placing the reaction girder 3 may include a step S32 of introducing the girder member 31 from the girder shaft 12A, a step S33 of connecting the introduced girder member 31 to the end of the girder member 31 exposed to the girder shaft 12A, and a step S34 of pushing the connected girder member 31 from the girder shaft 12A toward the girder shaft 12B, without carrying out the step S31 of constructing the girder pilot tunnel 15. According to this step S3, the reaction girder 3 can be provided according to the width of the existing underground structure 91 without constructing a hole for bridging the reaction girder 3.

[0064] <Variation 5> In the above embodiment, the ground anchor 2 is exemplified as the pull-out resistance member. As the pull-out resistance member, any member capable of generating a reaction force that resists the uplift of the existing underground structure 91 may be appropriately adopted. For example, a friction pile may be used as the pull-out resistance member. [Explanation of symbols]

[0065] 11A, 11B... anchor hole, 12A, 12B... girder shaft, 12a... bottom of girder shaft, 15... girder pilot tunnel, 2... ground anchor, 21... anchor body, 22... wire, 3... reaction girder, 31... girder member, 4... anchoring device, 7... retaining wall, 8A, 8B... girder frame, 81... main body, 82... hooking part, 90... ground surface, 91... existing underground structure, 91a... top surface, 91b... side, 92... new underground structure, 93... ground, X... extension direction, Y... width direction.

Claims

1. providing at least a pair of pull-out resistance members arranged to sandwich the existing underground structure and for generating a force resisting uplift of the existing underground structure; A step of providing at least a pair of vertical shafts that contain a pair of tension parts connected to the pair of pull-out resistance members, respectively, and expose the top surface of the existing underground structure; A step of placing a reaction member on a top surface of the existing underground structure exposed from the pair of shafts; a step of attaching at least a pair of fixing devices to the reaction member for applying a vertically downward reaction force to the reaction member, the reaction force being generated by an action of pulling the pair of tension portions; A method for controlling the uplift of an existing underground structure, comprising the steps of: applying a vertically downward reaction force to each of the reaction members by performing an operation of pulling the pair of tension portions using the pair of anchoring devices.

2. The reaction member is a reaction girder extending from a first shaft of one of the pair of shafts to a second shaft of the other of the pair of shafts, A method for controlling the uplift of an existing underground structure as described in claim 1, wherein in the step of positioning the reaction member, the reaction member is positioned so that a first end of the reaction girder is exposed from a first shaft and a second end of the reaction girder is exposed from a second shaft.

3. The reaction beam is formed by connecting a plurality of beam members to each other, The step of disposing the reaction member includes: Introducing the girder member through the first shaft; A step of connecting the introduced girder member to an end of the girder member exposed to the first shaft; pushing the connected girder members from the first shaft toward the second shaft; The method for controlling upheaval of an existing underground structure according to claim 2, further comprising repeating the steps of:

4. The reaction beam is formed by connecting a plurality of beam members to each other, In the step of disposing the reaction member, A step of providing a girder pilot shaft leading from the first shaft to the second shaft is carried out; After carrying out the step of providing the girder pilot hole, A step of connecting the introduced girder member to an end of the girder member exposed to the first shaft; pushing the connected girder members from the first shaft toward the second shaft; The method for controlling upheaval of an existing underground structure according to claim 2, further comprising repeating the steps of:

5. The reaction member includes a first girder frame and a second girder frame that are separate from each other, The step of disposing the reaction member includes: A step of placing a first girder frame on a top surface of the existing underground structure exposed from a first shaft of one of the pair of shafts; A method for controlling the uplift of an existing underground structure as described in claim 1, comprising a step of placing a second girder frame on the top surface of the existing underground structure exposed from the other second shaft of the pair of shafts.

6. providing at least a pair of pull-out resistance members arranged to sandwich the existing underground structure and for generating a force resisting uplift of the existing underground structure; A step of providing at least a pair of vertical shafts that contain a pair of tension parts connected to the pair of pull-out resistance members, respectively, and expose the top surface of the existing underground structure; A step of placing a reaction member on a top surface of the existing underground structure exposed from the pair of shafts; a step of attaching at least a pair of fixing devices to the reaction member for applying a vertically downward reaction force to the reaction member, the reaction force being generated by an action of pulling the pair of tension portions; a step of applying the reaction force in a vertical downward direction to each of the reaction members by performing an operation of pulling the pair of pulling portions by the pair of fixing devices; and constructing a new underground structure. The step of constructing the new underground structure includes: Excavating the ground above the existing underground structure; A step of confirming the degree of uplift of the existing underground structure; A construction method for an underground structure comprising: a step of adjusting the degree to which the pair of fixing devices pull the pair of pulling portions in accordance with the degree of uplift of the existing underground structure, thereby keeping the degree of uplift of the existing underground structure within a predetermined range.

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