JP3791092B2 - Construction method of shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shaft construction method, and more particularly to a construction method suitable for construction of a shaft having a large depth and a large diameter.
[0002]
[Prior art]
The vertical shaft is used for, for example, defining an underground space used for a parking lot or for starting or reaching a shield machine. The construction method of this type of shaft is to construct a retaining wall from the ground, excavate the inside surrounded by the retaining wall, and integrally form the bottom and the ring frame inside the retaining wall. The method is generally adopted.
[0003]
However, in such a construction method, the wall thickness of the retaining wall needs to be increased as the shaft to be constructed has a larger diameter or depth, and the retaining wall is supported when excavating the inside. In addition, it was necessary to take measures to swell the panel, and there was a demand for improvements in terms of economy and construction efficiency.
[0004]
As a means for solving such a problem, for example, Japanese Patent Laid-Open No. 6-33679 proposes a construction method of a deep depth shaft in which a shaft is constructed in an excavation groove filled with an in-hole stabilizing liquid. In the shaft construction method disclosed in this publication, the annular frame is divided into a plurality of parts, and a bottom plate of a watertight structure is formed at the lower end of the divided first-stage annular frame. Install in a floating state.
[0005]
And then, the gist is to perform the laying work by stacking and joining the sequentially divided annular casings on the annular casing of the prior order, and applying a loading load that opposes buoyancy. According to the construction method disclosed in this publication, it is possible to reduce the thickness of the retaining wall, and there is an advantage that it is not necessary to install a beam. There was a technical problem described below.
[0006]
[Problems to be solved by the invention]
That is, in the construction method of the shaft disclosed in the above publication, at the initial stage of construction, a bottom plate of a watertight structure is formed at the lower end of the first-stage annular frame, and this is floated in a stable liquid by buoyancy. For example, in a deep shaft with a diameter of about 20 m, if the bottom plate is constructed of reinforced concrete, its weight will be several thousand tons, and it is very difficult to lift it by buoyancy.
[0007]
In addition, when the first stage of the annular frame having such a heavy weight bottom plate formed at the lower end is formed in advance, a heavy machine that lifts this and installs it in the vertical hole also requires a very large scale. In addition, if a heavy-weight member is to be lifted by a large-scale heavy machine, it is necessary to improve the ground at the place where the suspension stand is installed, and there are problems to be solved when implementing such a construction method. There were many.
[0008]
This invention is made | formed in view of such a problem, The place made into the objective is to provide the concrete construction method which can construct | assemble a large diameter and deep shaft.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention is designed to counteract soil water pressure when a shaft having an annular frame formed by dividing into a plurality of lots and a bottom plate closing the lower end of the annular frame is constructed in the ground. A hollow box-shaped steel segment that integrally defines an outer shell of the bottom plate and a lower end portion of the annular casing, and a first step of forming a vertical hole filled with outside water in the ground. In this state, the bottom plate and the divided annular frame are formed by on-site casting, and internal water for buoyancy is injected into the formed shaft and the bottom plate is moved to the longitudinal direction. After being settled in the hole, it is configured to include a third step of removing the internal water and replacing and filling a backfill material between the vertical hole and the casing.
According to the construction method of a shaft constructed in this way, a hollow box-shaped steel segment that integrally defines the outer shell of the bottom plate and the lower end of the annular frame is levitated above the outside water. As a result, the weight to be hung on the floor is reduced, and sufficient buoyancy is obtained, so that the concrete for forming the bottom base and the concrete for forming the annular frame can be placed in the floating state.
The steel segment has a bottom plate that defines a bottom surface of the bottom plate, a side wall that defines a side surface of the bottom plate and a side surface of a lower end portion of the annular housing, and divides the bottom plate concentrically, The side wall can be composed of a plurality of box-shaped units divided in the circumferential direction.
According to this configuration, since the steel segment is divided into a plurality of box-shaped units, the scale of the lifting heavy machine can be further reduced.
When the internal water is formed by placing a formwork and forming a lot on the upper side of the annular frame by casting concrete, the upper end side of the shaft in the middle of the construction protrudes from the surface of the external water by a substantially constant amount. Can be introduced.
According to this configuration, when forming each lot of the annular frame, the height of the work platform used for installing the mold can be made constant.
The bottom plate can be formed at the initial stage of the second step by placing concrete on the bottom plate.
According to this structure, since the gravity center position of the steel segment is lowered, the steel segment can be supported in a floating state in a stable state.
When each lot and bottom plate of the annular frame are formed by placing the concrete, the posture of the steel segment or the shaft in the middle of construction can be maintained in a predetermined state by the posture control device.
According to this configuration, even when an unbalanced load is applied due to the concrete placement, construction and the inclination of the shaft in the middle are prevented, and the concrete placement operation can be performed in a stable state.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. 1 to 7 show an embodiment of a shaft construction method according to the present invention. The whole cross section of the shaft A constructed | assembled by the construction method of this invention is shown by FIG.
[0011]
The vertical shaft A shown in the figure is integrally formed with an annular frame B divided into nine stages (first lot (1) to ninth lot (9)) and closed at the lower end of the annular frame B. And a bottom board C to be formed.
[0012]
When constructing the shaft A having such a structure, first, as shown in FIG. 2, a vertical hole 12 is formed in the ground filled with external water 10 for counteracting soil pressure. The vertical hole 12 is formed by excavating the interior surrounded by the retaining wall 13 after driving a simple retaining wall 13 having water-stopping properties such as a steel sheet pile from the ground to a predetermined depth.
[0013]
The diameter of the vertical hole 12 is slightly larger than the diameter of the shaft A to be constructed, and is formed to a depth slightly deeper than the entire length of the shaft A (first step). When the formation of the vertical hole 12 is completed, the building of the shaft portion (bottom base C, annular housing B) of the shaft A is performed (second step).
[0014]
In this step, first, the box-shaped steel segment 14 is levitated and installed on the outside water 10 in the vertical hole 12 as shown in FIG. The box-shaped steel segment 14 integrally defines a plurality of lower end portions of the bottom plate A and the annular casing B, for example, the outer shell of the second lot (2), and is formed hollow inside. ing.
[0015]
FIG. 6 shows details of the box-shaped steel segment 14. A box-shaped steel segment 14 shown in the figure has a bottom plate 14a that defines the bottom surface of the bottom plate A, and a side wall 14b that defines the side surfaces of the bottom plate A and a plurality of lower end portions of the annular casing B. .
[0016]
In the case of this embodiment, the box-shaped steel segment 14 is composed of one cylindrical box-shaped unit 140 whose upper end is opened, and four fan-shaped box-shaped units 141 whose upper ends are similarly opened, The bottom plate 14a is divided into two concentric circles, and the bottom plate 14a of the annular portion on the outer peripheral side is divided into four in the circumferential direction.
[0017]
The cylindrical box-shaped unit 140 has a circular bottom plate 140a and a ring plate 140b erected on the outer peripheral edge of the circular bottom plate 140a. Each fan unit 141 includes a fan-shaped bottom plate 141a, a pair of joint flange plates 141b erected on the side edges in the circumferential direction of the bottom plate 141a, and inner and outer curved surface plates 141c erected on inner and outer peripheral edges of the bottom plate 141a. , 141d.
[0018]
The inner curved surface plate 141c is joined to the outer periphery of the ring plate 140b, and the outer curved surface plate 141d constitutes a part of the side wall 14b, and when the fan-shaped box-shaped unit 141 is connected in the circumferential direction, the annular side wall 14b. Is formed.
[0019]
The ring plate 140b, the joining flange plate 141b, and the inner curved surface plate 141c are set to a height that fits within the bottom plate C. 6 (A) and 6 (B) is a through-hole used when adjusting the outside water level 10 to be described later or injecting a backfill material, and forms a bottom plate C. Until this is done, the through hole 142 is closed.
[0020]
When the steel segment 14 is installed on the external water 10, the cylindrical box unit 140 and the fan-shaped box unit 141 are lifted and floated on the external water 10 for assembly. At the time of this assembly, the cylindrical box-shaped unit 140 is arranged at the center, and the fan-shaped box-shaped unit 141 is arranged on the outer peripheral side so as to surround it, and as shown in FIG. And the inner curved surface plate 141b, and between the joint flange plates 141b, respectively, by interposing a watertight packing 143 and fastening them with bolts and nuts.
[0021]
The floating installation state of the steel segment 14 assembled in this way is shown in FIG. Here, for example, as shown in FIG. 1, the vertical shape of the vertical shaft A to be constructed is a circular section having a diameter of 16 m, a height of 36.8 m, a thickness of the bottom panel B of 2 m, and an annular shape. The height from the first lot (1) to the eighth lot (8) of the chassis B is 4 m, the height of the ninth lot (9) is 2.8 m, and the thickness of the bottom plate 14a of the steel segment 14 is 2 cm, specific gravity is 7.85, the weight per unit length of the side wall 14b is 16 t / m, and if the portion up to the second lot (2) is included in the steel segment 14, the total height of the steel segment 14 Is 10 m.
[0022]
In this case, the weight W ₀ of the bottom plate 14a is π / 4 × 16 ² × 0.02 × 7.85 = 31.55t. On the other hand, the weight W ₀ ′ of the side wall 14b is 16 t / m × 10 = 160 t, and the total weight W ₁ of the steel segment 14 at this stage is 31.5 + 160 = 191.55 t, and the specific gravity of the outside water 10 is 1 Then, when the steel segment 14 is levitated, the height at which the steel segment 14 protrudes on the surface of the external water 10 is 10−W ₁ / (π / 4 × 16 ² ) = 9.05 m. Become.
[0023]
Next, in this state, concrete is placed on the bottom plate 14a to form the bottom plate C as shown in FIG. If the thickness of the bottom plate C is 2 m and the specific gravity of the concrete is 2.4, the weight of the concrete of the bottom plate C is π / 4 × 16 ² × 2 × 2.4 = 965 t. The total weight W ₂ is W ₁ + 965 = 1157 t.
[0024]
In this case, the height at which the steel segment 14 protrudes from the surface of the external water 10 is 10−W ₂ / (π / 4 × 16 ² ) = 4.2 m. When placing concrete for forming the bottom plate C, a pipe 144 is installed at a position communicating with the through hole 142 provided in the bottom plate 14a, and the pipe 144 is connected to a hose for extracting the external water 10. (Not shown) is connected.
[0025]
Next, in the case of the present embodiment, as shown in FIG. 3C, the third lot (3) of the annular casing B is formed on the upper end side of the steel segment 14. When forming the third lot (3), the forming mold 16 is installed on the upper end of the steel segment 14, but the height of the mold 16 is 4 m. Since the upper end of the steel segment 14 protrudes 4.2 m above the surface of the external water 10, if installed as it is, the upper end of the formwork 16 protrudes 8.2 m above the surface of the water. The height becomes too large, which can hinder concrete placement work.
[0026]
Therefore, in the case of the present embodiment, buoyancy countermeasures are provided in the steel segment 14 so that the protruding height on the outside water 10 is substantially constant (for example, approximately 5 m corresponding to one lot). Internal water 18 was introduced. The state of introduction of the internal water 18 is shown in FIG.
[0027]
When the internal water 18 is introduced into the segment 14, the amount is gradually increased according to the assembled state of the mold 16. In addition, when placing the mold 16 and placing concrete therein, it is predicted that the steel segment 14 will be inclined due to uneven placement of the casting amount, etc. Further, it is predicted that the steel segment 14 will gradually sink, which may hinder the concrete placing work.
[0028]
Therefore, in the case of the present embodiment, as shown in FIG. 7 as an example, until the concrete is cast and demolded, the posture of the steel segment 14 and the shaft A during construction is kept constant. The attitude control device 20 is used.
[0029]
The attitude control device 20 shown in the figure includes a plurality of winches 20a and hydraulic jacks 20b. The winch 20a is installed at a position where the shaft A to be constructed is divided into four or three parts at equal angular intervals along the circumferential direction, and is fixedly installed on a gantry 20c partially embedded in the ground. . One end of the wire 20d wound around each winch 20a is coupled to the bottom surface of the steel segment 14 by appropriately installing a guide roller.
[0030]
In the hydraulic jack 20 b, a contact plate that contacts the inner surface of the retaining wall 13 is provided on the distal end side, and is installed on the side surface of the steel segment 14 on a step.
[0031]
The posture control device 20 configured as described above is performed by controlling expansion and contraction of the hydraulic jack 20b in the horizontal direction. Further, in the initial stage where the internal water 18 is not introduced, the vertical attitude control is supported by the winch 20a so that the steel segment 14 does not sink when the concrete is placed.
[0032]
On the other hand, when reaching the stage where the internal water 18 is introduced, it is balanced by appropriately discharging the internal water 18 when placing the concrete. Note that such posture control by the posture control device 20 is also performed when the bottom board C is formed by placing concrete.
[0033]
When the third lot (3) is formed, since the thickness of the annular casing B is 1.2 m, the weight of the third lot ( ³ ) is π / 4 × (16 ² -13.6 ² ) × 4.0. × 2.4 = 536t, and the total weight W ₃ of the third lot ▲ 3 ▼ forming end, the height of which projects W ₂ + 536 = 1693t, and the above water of the external water 10, 14- W ₃ / (Π / 4 × 16 ² ) = 5.5 m.
[0034]
Next, in this embodiment, as shown in FIG. 3D, the first lot (1) of the annular casing B is formed. When the first lot (1) is formed, the inner mold is placed on the inner surface side of the side wall 14b, and concrete is placed. When the first lot (1) is placed and formed, even if the protruding height on the outside water 10 is 5.5 m, the formwork is not installed on the upper part thereof, so the inside water 18 is not introduced. Only the attitude control by the attitude control device 20 is performed.
The total weight W ₄ at the end of formation of the first lot (1) is the same as the weight from the first lot (1) to the eighth lot (8), so W ₃ + 536 = 2229t. The height protruding upward is 18−W ₄ / (π / 4 × 16 ² ) = 3.9 m.
[0035]
When the formation of the first lot {circle around (1)} is completed, the formation of the fourth lot {circle around (4)} is performed as shown in FIG. When forming the fourth lot (4), it is necessary to install the mold 16 on the third lot (3). Similarly, introduction of the internal water 18 and posture control are performed.
[0036]
The total weight W ₅ at the end of formation of the fourth lot (4) is W ₄ + 536 = 2765 t, and the height of the outside water 10 protruding above the water surface is 22−W ₅ / (π / 4 × 16 ² ) = 4.2 m.
[0037]
Next, as shown in FIG. 4B, the fifth lot (5) is formed. When forming the fifth lot (5), it is necessary to install the mold 16 on the fourth lot (4). Therefore, prior to the formation of this, the third and fourth lots (3), As in the case of (4), the introduction of the internal water 18 and the posture control are performed.
[0038]
The total weight W ₆ at the end of formation of the fifth lot (5) is W ₅ + 536 = 3301 t, and the height of the outside water 10 protruding above the water surface is 26−W ₆ / (π / 4 × 16 ² ) = 5.5 m.
[0039]
Next, as shown in FIG. 4C, the second lot {circle around (2)} is formed. When forming the second lot (2), as in the case of forming the first lot (1), the internal water 18 is not introduced and only the attitude control by the attitude control device 20 is performed.
[0040]
The total weight W ₇ at the end of formation of the second lot (2) is W ₆ + 536 = 3837t, and the height of the outside water 10 protruding above the water surface is 30−W ₆ / (π / 4 × 16 ² ) = 2.8 m.
[0041]
Thereafter, as shown in FIG. 4D and FIGS. 5A to 5C, the sixth lot (6) to the ninth lot (9) are sequentially stacked. When placing and forming these lots, the introduction, discharge and posture control of the internal water 18 are performed as in the third lot (3). The protruding height of the outside water 10 on the surface of the water at the end of formation of each lot is 4.2 m, 5.5 m, 6.8 m, and 7.7 m.
[0042]
Then, when the formation of the ninth lot (9) is completed, the sinking internal water 18 is introduced into the formed shaft A, and the bottom surface of the bottom plate B is fixed to the bottom surface of the vertical hole 12, and then the bottom plate When the backfill material such as mortar is filled between the outer periphery of the shaft A and the vertical hole 12 through the pipe 144 provided in C so as to replace the outside water 10, and the backfill material is hardened, the shaft The construction of A is completed (third step).
[0043]
Now, according to the construction method of the shaft A performed in the above process, the hollow box-shaped steel which integrally defines the outer shell of the bottom base C and the lower end part of the annular frame B on the outer water 10. Since the made segment 14 is levitated, the weight to be hung on the outside water 10 is reduced, and sufficient buoyancy is obtained, so that the bottom plate forming concrete and the annular frame forming concrete can be placed in the levitated state. It becomes possible.
[0044]
In the case of the present embodiment, the steel segment 14 has a bottom plate 14a that defines the bottom surface of the bottom plate C, and a side wall 14b that defines the side surface of the bottom plate C and the side surface of the lower end of the annular casing B. In addition, since the bottom plate 14a is divided into concentric circles and the side wall 14b is constituted by a plurality of box-shaped units 140 divided in the circumferential direction, the scale of the lifting heavy machine can be further reduced.
[0045]
Further, when the formwork 16 is installed and the lot on the upper side of the annular frame B is formed by placing concrete, the upper end side of the shaft A in the middle of construction is the water surface 18 of the outside water 10. Since it is introduced so that it protrudes from the top by a certain amount, when forming each lot, the height of the worktable for installing the mold can be made constant, and there is no need to adjust the height of the worktable. Improve your efficiency.
[0046]
Further, since the bottom plate C is formed in the initial stage of the second step by placing concrete on the bottom plate 14a, the center of gravity of the steel segment 14 is lowered, and the steel segment 14 can be supported in a stable state. it can.
[0047]
Further, when forming each lot of the annular frame B and the bottom base C by placing concrete, the posture of the steel segment 14 or the shaft A in the middle of construction is maintained in a predetermined state by the posture control device 20, so that the concrete Even if an unbalanced load is applied due to the placement, the inclination of the shaft A during construction is prevented, and the concrete placement operation can be performed in a stable state.
[0048]
In addition, in the said Example, although the case where the cyclic | annular frame B was divided | segmented into 9 steps | lots was illustrated, the division | segmentation number is not restricted to this. Moreover, in the said Example, although the case where two lots of the cyclic | annular frame B was included in the steel segments 14 was shown, the number is not restricted to this.
[0049]
【The invention's effect】
As described above in detail in the embodiments, according to the construction method of a vertical shaft according to the present invention, a large-scale lifting facility is formed by on-site placement on a segment that supports the floating bottom of a heavy weight. It is possible to construct a large diameter and deep shaft without any incidental work such as ground improvement.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a shaft constructed by a construction method according to the present invention.
FIG. 2 is an explanatory cross-sectional view showing the first step of the shaft construction method according to the present invention.
FIG. 3 is an explanatory diagram of a process performed subsequent to the process of FIG. 2;
4 is an explanatory diagram of a process performed subsequent to the process of FIG. 3. FIG.
FIG. 5 is an explanatory diagram of a process performed subsequent to the process of FIG. 4;
FIG. 6 is a plan view, a sectional view, and an enlarged sectional view of a steel segment used in the shaft construction method according to the present invention.
FIG. 7 is an explanatory diagram showing an example of a posture control device employed in the shaft construction method according to the present invention.
[Explanation of symbols]
A Vertical shaft B Ring body C Bottom plate 10 Outer water 12 Vertical hole 13 Earth retaining wall 14 Steel segment 14a Bottom plate 14b Side wall 140 Cylindrical box-shaped unit 141 Fan-shaped box-shaped unit 16 Form 18 Internal water 20 Attitude control device

Claims (5)

When constructing a shaft with an annular frame divided into multiple lots and a bottom plate that closes the lower end of the annular frame, a vertical hole filled with external water for counteracting soil pressure is formed in the ground. The first step;
A hollow box-shaped steel segment that integrally defines an outer shell of the bottom plate and the lower end of the annular frame is floated on the outside water, and the bottom plate and the divided annular frame are placed on-site in this state. A second step formed by:
After injecting internal water for buoyancy into the formed shaft and allowing the bottom plate to settle in the vertical hole, a backfill material is disposed between the vertical hole and the frame. A shaft construction method characterized by including a third step of replacement filling. The steel segment has a bottom plate that defines a bottom surface of the bottom plate, and a side wall that defines a side surface of the bottom plate and a side surface of a lower end portion of the annular casing,
The shaft construction method according to claim 1, wherein the bottom plate is divided into concentric circles and the side walls are divided into a plurality of box-shaped units in the circumferential direction. When the internal water is formed by placing a formwork and forming a lot on the upper side of the annular frame by casting concrete, the upper end side of the shaft in the middle of construction protrudes from the surface of the external water by a substantially constant amount. The shaft construction method according to claim 1, wherein the shaft construction method is introduced. The shaft construction method according to claim 2, wherein the bottom plate is formed at the initial stage of the second step by placing concrete on the bottom plate. The posture of the steel segment or the shaft in the middle of construction is maintained in a predetermined state by a posture control device when forming each lot and bottom plate of the annular frame by placing the concrete. The construction method of the shaft described in 3 or 4.

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