JP5584542B2 - Ground deformation prevention method and underground structure construction method using the same - Google Patents

Description

  The present invention relates to a ground deformation prevention method and an underground structure construction method using the same.

  For example, ground deformation called bulging may occur in excavation work or the like. This bulge is a phenomenon in which the ground on the bottom of excavation bulges. The causes of board swelling are as follows: 1. Stress release and dredging pressure by excavation. 2. Expansion of volume due to the collapse of soil or rocks by contact with water; 3. Uplift of underground structure due to excavation of ground mountain above underground structure buried underground, and weight reduction. It is possible that the underground structure will rise due to the increase in groundwater pressure. Conventionally, for example, the bottom of excavation has been improved and solidified to prevent board swelling (see, for example, Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 2003-171949 JP 2001-182088 A

  In the prior art described above, before the excavation process, the solidifying agent injection pipe is inserted from the ground to the bottom plate depth to improve the ground. Since this method requires work from the ground, a lot of time and effort are required for road regulation. In addition, if the existing underground structure is buried in the upper part of the ground improvement area and it is difficult to insert the solidifying agent injection pipe, the entire area that prevents ground deformation such as bulging due to various restrictions at the construction site Sometimes it is impossible to improve the ground. Therefore, a new construction method that replaces the prior art is demanded.

  From such a viewpoint, an object of the present invention is to provide a new ground deformation prevention method capable of preventing the deformation of the ground, and an underground structure construction method using the same.

The present invention has been made to solve the problems described above is to construct an upper tunnel existing underground structures in ground, in the tunnel to prevent Ri floating of the existing underground structure And a ground deformation prevention method for constructing a pressing structure for preventing deformation of the ground below the tunnel, wherein an anchor is inserted from the inside of the tunnel toward the lower ground, and the anchor and the pressing A ground deformation prevention method characterized by connecting a structure .

According to such a method, since the holding structure is built inside the tunnel after the tunnel is built, the holding structure can be built by working in the ground, reducing work from the ground and reducing ground deformation. Even when it is impossible to improve the ground over the entire area to be prevented, it is possible to prevent ground deformation such as swelling of the ground while preventing the existing underground structure from rising .

The anchor is preferably connected to the pressing structure when the pressing structure is constructed.

The tunnel is preferably composed of a plurality of small-section tunnels, and the adjacent small-section tunnels are constructed adjacent to each other.

Furthermore, it is preferable that the cross-sectional shape of the small cross-sectional tunnel has a hexagonal shape in which two corners on the upper side of the rectangle are linearly chamfered.

Furthermore, the present invention provides a bottom construction step of constructing a tunnel at the bottom of a planned construction position of a new underground structure to be constructed above an existing underground structure in the ground, and a lower part of the tunnel from within the tunnel. An anchor installation step for inserting an anchor toward the ground, a holding structure construction step for building a holding structure in the tunnel, an anchor connection step for connecting the holding structure to the anchor, and the tunnel And an upper construction step of constructing an upper part of the newly installed underground structure by excavating upward.

According to such a method, since the holding structure is built inside the tunnel after the tunnel is built, work from the ground can be reduced. In addition, since the tunnel has a small cross section, even if the tunnel is constructed before constructing the holding structure, there is little possibility of ground deformation such as bulging. Furthermore, the pressing structure can be effectively used as the bottom plate of the newly installed underground structure. Further , the pressing effect can be improved by connecting the pressing structure to an anchor embedded in the ground below the pressing structure. Alternatively, since the weight of the holding structure is small, it can be thinned.

  Furthermore, if the tunnel is constructed by the propulsion method or shield method in the tunnel construction process, and the upper part of the newly installed underground structure is constructed by the opening construction method in the upper construction process, the holding structure is constructed prior to the excavation. Therefore, even when the ground is dug down from the ground surface, the holding structure becomes a “weight” and can prevent ground deformation such as swelling of the ground.

  In addition, in the upper construction step, if water is retained between the earth retaining wall formed on the outer side in the width direction of the small section tunnel and the small section tunnel, it is possible to prevent water from entering the construction area.

  ADVANTAGE OF THE INVENTION According to this invention, the deformation | transformation of a ground can be prevented by the new construction method replaced with ground improvement.

It is sectional drawing which showed the ground which applies the ground deformation | transformation prevention method and underground structure construction method which concern on this invention. It is sectional drawing which showed the state which constructed | assembled the small cross-section tunnel in embodiment of the ground deformation | transformation prevention method and underground structure construction method which concern on this invention. It is the front view which showed the excavator. In embodiment of the ground deformation | transformation prevention method and underground structure construction method which concern on this invention, it is sectional drawing which showed the state which constructed | assembled the pressing structure. In embodiment of the ground deformation | transformation prevention method and underground structure construction method which concern on this invention, it is sectional drawing which showed the state which excavated the upper part of the small cross-section tunnel. It is sectional drawing which showed the state which excised the upper part of the small section tunnel in embodiment of the ground deformation | transformation prevention method and underground structure construction method which concern on this invention. It is sectional drawing which showed the state which constructed | assembled the upper part of the large section tunnel in embodiment of the ground deformation | transformation prevention method and underground structure construction method which concern on this invention. In embodiment of the ground deformation prevention method and underground structure construction method which concern on this invention, it is sectional drawing which showed the state which the large cross-section tunnel was completed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, a ground deformation preventing method and an underground structure building method using the ground deformation prevention method will be described by taking as an example a case where the lower portion of the large section tunnel is constructed using a small section tunnel.

  The ground deformation prevention method is a method for preventing ground deformation such as swelling of the ground, and a tunnel (small cross-section tunnel described later) is constructed in the ground, and deformation of the ground below the tunnel is prevented in the tunnel. It is characterized by constructing a holding structure for the purpose.

  The underground structure construction method according to the present embodiment is a large cross section in which a lower section (bottom plate 11) of a large section tunnel 10 which is a newly installed underground structure is constructed using a small section tunnel 20 (tunnel in the claims). There is a tunnel construction method in which a bottom construction step for constructing a tunnel at the bottom of a planned construction position of a new underground structure constructed in the ground, and a small construction at a bottom of the construction planned position 12 of the large-section tunnel 10 are provided. A bottom construction process for constructing the cross-section tunnel 20, a holding structure construction process for constructing the press structure 30 in the small cross-section tunnel 20, and an upper portion 14 of the large cross-section tunnel 10 by excavating above the small cross-section tunnel 20. And an upper construction process for constructing. The underground structure construction method according to the present embodiment includes an anchor connection step for connecting the presser structure 30 to the anchor 22 buried below, and a retaining wall 55 formed on the outer side in the width direction of the small cross-section tunnel 10. And a water stop step for stopping water between the small-section tunnel 10.

  In the present embodiment, only the lower portion of the large-section tunnel 10 is constructed using the small-section tunnel 20, but the underground structure construction method according to the present invention is not limited to this. In other words, it is only necessary to construct at least the lower part of the large section tunnel using the small section tunnel, and use the small section tunnel constructed by the propulsion method or the shield method up to the upper part of the large section tunnel. You may make it build.

  In the present embodiment, as shown in FIG. 1, a sewage tunnel (underdrain) 2 is embedded as an existing underground structure in a ground 1 for constructing a large-section tunnel 10 (see FIG. 8). Two sewage tunnels 2 are buried in parallel along the extending direction of the large-section tunnel 10. The large section tunnel 10 is constructed along the sewage tunnel 2 above the sewage tunnel 2.

(Bottom construction process)
First, as shown in FIG. 2, a small-section tunnel 20 is constructed above the sewage tunnel 2 in the ground 1. The small section tunnel 20 is constructed at the bottom of the planned construction position 12 of the large section tunnel 10. A plurality of small-section tunnels 20 are constructed in parallel, and are arranged linearly adjacent to each other in the width direction (in this embodiment, five rows). The cross-sectional area of the small cross-section tunnel 20 is a value that can prevent the sewage tunnel 2 from rising due to the weight of the small cross-section tunnel 20 and the surrounding earth and sand even if the ground sediment for the cross section of the small cross-section tunnel 20 is removed. Calculate as follows.

  The small section tunnel 20 is constructed by a known tunnel construction method (promotion method in this embodiment) such as a propulsion method or a shield method. The small-section tunnel 20 has a hexagonal shape in which the cross-sectional shape of the two upper corners of the rectangle is chamfered linearly. In addition, the cross-sectional shape of the small cross-section tunnel 20 is not limited to a hexagon, and is appropriately determined according to the state of the ground.

  The excavator 50 shown in FIG. 3 is provided at the tip of the propulsion box 21 of the small-section tunnel 20. The excavator 50 propels from a start shaft (not shown) toward a destination shaft. The excavator 50 includes a main cutter 51 and a corner cutter 52 on the front. The main cutter 51 has a shaft portion disposed at the center of the front surface of the excavator 50 and excavates most of the small-section tunnel 20. The corner cutters 52 are disposed at the corners on both sides of the front lower part, and excavate the two protruding corners below the small section tunnel 20. In addition, when the ground 1 contains a lot of gravel, the upper corner portion is chamfered and the corner cutter is omitted as in the present embodiment to reduce the cost. However, when the upper part of the large section tunnel is also constructed using the small section tunnel, corner cutters are provided at the four corners to form a rectangular section excavator. Further, when the ground is relatively easy to excavate, an excavator having a rectangular cross section may be used.

(Anchor connection process)
Next, a hole is made in the bottom of the small tunnel 20 at the center, and the anchor 22 is inserted from this hole toward the ground below as shown in FIG. A plurality of anchors 22 are formed at a predetermined pitch along the longitudinal direction of the tunnel. The anchor 22 is connected to the holding structure 30 when the holding structure 30 is constructed in the small cross-section tunnel 20. In this embodiment, after the anchor 22 is formed, the pressing structure 30 is constructed. However, the construction order is not limited to this, and the anchor is formed after the pressing structure is constructed. Also good.

(Presser structure construction process)
In the pressing structure constructing step, the pressing structure 30 is constructed in the small cross-section tunnel 20. The holding structure 30 is composed of a slab made of reinforced concrete. In the present embodiment, the holding structure 30 is formed with a weight that can prevent the sewage tunnel 2 from being lifted when the upper portion of the small-section tunnel 20 is cut. In constructing the holding structure 30, the skin plate of the steel shell at the contact portion of the adjacent propelling boxes 21, 21 is removed, and the insides of the plurality of small cross-sectional tunnels 20, 20,. Then, bar arrangement is continuously applied inside each small-section tunnel 20 communicated, and concrete is placed so as to have a predetermined thickness. The concrete is supplied from the starting shaft or the reaching shaft through the small section tunnel 20 and placed in the small section tunnel 20.

  At this time, reinforcement is also appropriately provided around the head of the anchor 22, and the pressing structure 30 and the anchor 22 are integrated (anchor connecting step). The holding structure 30 includes a concrete structure 31 integrally formed in the small cross-section tunnel 20 and a lower portion 21 a of the propulsion box 21. By constructing the holding structure 30 in the small cross-section tunnel 20 in this way, the weight above the sewage tunnel 2 is secured, and by pressing from above, the holding structure 30 becomes “weight” and is used for sewage. Prevent the tunnel 2 from lifting.

(Upper construction process)
Next, the process proceeds to the upper construction process. As shown in FIGS. 5 to 7, in the upper construction process of the present embodiment, the upper part 14 of the large-section tunnel 10 is constructed by an open-cut method.

  First, as shown in FIG. 5, a retaining wall 55 is formed on the outer side in the width direction of the plurality of small cross-sectional tunnels 20, 20. The retaining wall 55 is formed on both sides of the planned construction position of the large-section tunnel 10 before digging the ground in the excavation process. The retaining wall 55 is formed by, for example, driving a plurality of retaining piles made of H-shaped steel or the like and inserting a sheet pile between adjacent retaining piles.

  Thereafter, the upper part of the small-section tunnel 20 is cut from the ground. When the ground 1 is dug down, a beam or the like is assembled between the retaining walls 55 and 55 facing each other to form a mountain retaining work 56, and the retaining wall 55 is supported from the inside of the cut groove. In parallel with the excavation, water is stopped between the retaining wall 55 and the small-section tunnel 20 (water stop process). This water stop is performed by improving the ground 57 between the retaining wall 55 and the small-section tunnel 20 and below the ground 57. In the ground improvement, an injection material such as cement milk or a solidified chemical solution is injected into the ground 57 to reduce the water permeability coefficient. Here, the ground 1 above the sewage tunnel 2 is removed, but since the pressing structure 30 presses the sewage tunnel 2 from above, the sewage tunnel 2 does not rise.

  When the water stop construction is completed, as shown in FIG. 6, the upper portion 21 b of the propulsion box 21 of the small-section tunnel 20 (the portion protruding upward from the concrete structure 31 of the pressing structure 30) is cut and removed. To do. The propelling box 21 is cut at a height equivalent to the upper surface of the pressing structure 30. The holding structure 30 and the lower portion 21 a of the propelling box 21 constitute the lower portion (bottom plate 11) of the large-section tunnel 10.

  Thereafter, anchor bars (not shown) are installed on the upper portion of the bottom plate 11 and a mold (not shown) is formed. Then, for each area of a predetermined length in the tunnel longitudinal direction, the mountain retaining structure 56 is removed, and concrete is placed in the formwork to construct the upper portion 14 of the large section tunnel 10. When the strength of the large cross-section tunnel 10 is developed after a predetermined curing period, a mountain retaining work 56 ′ is formed between the large cross-section tunnel 10 and the retaining wall 55. Thereafter, in the adjacent area where the construction of the upper portion 14 of the large-section tunnel 10 is completed, the above steps are sequentially repeated to construct the upper portion 14 of the large-section tunnel 10. In this manner, by changing the pile support 56, 56 ′ for each area of a predetermined length, the length at which the pile support 56 is removed when placing concrete can be shortened. It is possible to fix the wall of the wall.

  When the construction of the upper portion 14 is completed over the entire length of the large cross-section tunnel 10, the mountain construction support 56 'is removed while performing backfilling, and the tunnel construction is completed. At this time, the retaining wall 55 is also buried.

  According to the ground deformation prevention method and the underground structure construction method as described above, the small-section tunnel 20 is constructed in the ground 1, and the holding structure 30 is constructed in the small-section tunnel 20. Therefore, the deformation of the ground 1 can be prevented by the construction in the ground 1. In particular, in this embodiment, since the pressing structure 30 is formed above the sewage tunnel 2, the sewage tunnel 2 can be prevented from being lifted. In addition, since the work from the ground in the work for preventing ground deformation is performed inside the small section tunnel 10 formed in the ground, it is significantly reduced compared to the conventional case where the solidifying agent is injected from the ground. Can do. Thereby, the influence on the ground such as road regulations can be minimized.

  Moreover, according to the new ground deformation prevention method and underground structure construction method for constructing the holding structure 30 in the ground as in the present embodiment, the existing underground structure in the upper part of the ground improvement region in the conventional construction method. Even if it is impossible to perform ground improvement over the entire area where ground deformation is prevented, such as when it is difficult to insert a solidifying agent injection pipe due to being buried, it prevents deformation of the ground 1 can do.

  Further, in the present embodiment, the pressing structure 30 constitutes the bottom plate 11 of the large-section tunnel 10 constructed in the ground 1 in a later step together with the lower portion 21a of the propelling box 21, so the pressing structure 30 can be used effectively. As a result, the construction period and cost of the large-section tunnel 10 can be shortened. In other words, since the ground deformation is prevented by using the bottom plate 11 of the large section tunnel 10, it is not necessary to perform the construction only for the ground deformation prevention like the conventional solidifying agent injection, and the construction period for that time And cost can be omitted.

  Moreover, in this embodiment, since the holding | suppressing structure 30 is connected to the anchor 22 embed | buried under the ground 1 of the downward direction, the improvement of the pressing effect which prevents a deformation | transformation of the ground 1 can be aimed at. Moreover, since the weight of the pressing structure 30 can be reduced by connecting the pressing structure 30 to the anchor 22, the main body of the pressing structure 30 can be made thin. As a result, the cost and construction period required for the construction of the holding structure 30 can be reduced.

  Furthermore, in this embodiment, since the upper part of the large-section tunnel 10 is constructed by the open-cut method, it is possible to shorten the construction period and reduce the cost in the upper construction process. In addition, since the earth retaining pile 54 in the excavation work is driven after the pressing structure 30 is constructed, the work from the ground (the anchor pile 54 is driven) can be performed continuously with the schedule of the excavation process. As a result, the road regulation period can be minimized.

  Furthermore, in the upper construction process, water is stopped between the retaining wall 55 formed on the outer side in the width direction of the small cross-section tunnel 20 and the small cross-section tunnel 20, so that inundation into the construction area can be prevented, and the construction environment Can be improved. In addition, depending on the state of the ground 1 (when there is little groundwater, etc.), it may not be necessary to perform the water stop construction.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not the meaning limited to the said embodiment, A design change is possible suitably in the range which does not deviate from the meaning of this invention. For example, in the present embodiment, the pressing structure 30 is provided above the sewage tunnel 2 and configured to prevent its lifting, but is not limited thereto. Even in the ground 1 where the sewage tunnel is not buried, when constructing a large section tunnel in the ground where the ground may be lifted or deformed, for example, the ground where the groundwater pressure is high, the large section tunnel Alternatively, a small-section tunnel may be constructed at the bottom of the planned construction position, and a holding structure may be formed in the small-section tunnel. Further, the existing underground buried object is not limited to the sewage tunnel 2, and the present invention can be applied to a structure buried underground such as a subway box or a fabric cloth foundation. Is possible.

  Furthermore, in the upper construction process of the present embodiment, the upper portion 14 of the large section tunnel 10 is constructed by the open-cut method, but the present invention is not limited to this, and the upper portion 14 is constructed using the small section tunnel. It may be. In this way, work from the ground can be further reduced.

  Moreover, in the said embodiment, although the large cross-sectional tunnel 10 was the newly installed underground structure built in the ground 1, it is not limited to this. For example, another underground structure such as an underground tank buried underground may be used. In this case, a tunnel is formed in the base portion formed below the underground tank, and a holding structure is constructed in the tunnel. As a result, deformation of the foundation portion and the ground below it can be prevented.

  Furthermore, in the ground deformation prevention method according to the present invention, the construction position of the small cross-section tunnel is not limited to the bottom of the construction planned position of the large cross-section tunnel. Specifically, even if it is not a place for constructing underground structures such as tunnels, a small-section tunnel is constructed and pressed inside the ground where ground deformation may occur due to, for example, an increase in groundwater pressure. A structure may be constructed. Even in this case, since the work from the ground can be omitted, the influence on the ground such as road regulation can be reduced.

1 Ground 10 Large section tunnel (new underground structure)
11 Bottom plate 12 Planned construction position (for large section tunnel) 14 Upper part (for large section tunnel) 20 Small section tunnel (tunnel)
21a Lower part (small section tunnel) 21b Upper part (small section tunnel) 22 Anchor 30 Holding structure 55 Earth retaining wall

Claims (7)

A holding structure for constructing a tunnel above an existing underground structure in the ground and preventing the existing underground structure from rising in the tunnel and preventing deformation of the ground below the tunnel A method of preventing ground deformation,
A ground deformation prevention method , wherein an anchor is inserted from the tunnel toward the lower ground to connect the anchor and the pressing structure . The ground deformation preventing method according to claim 1, wherein the anchor is connected to the pressing structure when the pressing structure is constructed . The tunnel comprises a plurality of small section tunnels,
The ground deformation preventing method according to claim 1 , wherein the adjacent small-section tunnels are constructed adjacent to each other . 4. The ground deformation prevention method according to claim 3, wherein the cross-sectional shape of the small-section tunnel has a hexagonal shape in which two corners on the upper side of the rectangle are linearly chamfered . A bottom construction process for constructing a tunnel at the bottom of the planned construction position of a new underground structure built above an existing underground structure in the ground ;
An anchor installation step of inserting an anchor from the inside of the tunnel toward the ground below the tunnel;
A holding structure construction process for building a holding structure in the tunnel;
An anchor connection step of connecting the pressing structure to the anchor ;
An upper construction step of excavating above the tunnel and constructing an upper part of the newly installed underground structure. In the bottom construction step, the tunnel is constructed by a propulsion method or a shield method,
6. The underground structure building method according to claim 5, wherein, in the upper building process, the upper part of the newly installed underground structure is built by an open-cut method. The underground structure construction method according to claim 6, further comprising a water stopping step for stopping water between a retaining wall formed on the outer side in the width direction of the tunnel and the tunnel.

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