JP3826331B2 - Pneumatic caisson and its installation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic caisson and a method for its deposition, and more particularly to a pneumatic caisson and a method for its deposition in which an underground wall is efficiently constructed when an underground tank for storing liquefied natural gas is built.
[0002]
[Prior art]
Conventionally, many large-scale underground tanks have been constructed as tanks for storing liquefied natural gas (hereinafter referred to as LNG). In order to build these LNG underground tanks, it is necessary to perform deep excavation on the target ground. Usually, in order to perform deep excavation, it is necessary to construct a large-scale mountain retaining work with high rigidity. For this reason, the underground continuous wall method and the caisson method are often applied to the construction of the LNG underground tank.
FIG. 5 is a cross-sectional view showing a state in which a LNG underground tank housing is constructed on the ground at a high groundwater level by the caisson method. The figure shows a caisson body 50 that has been laid by a pneumatic caisson method. The caisson body 50 functions as a ceiling slab for the work chamber 53 while closing the cylindrical side wall housing 51, the blade 52 formed at the lower end of the side wall housing 51 and grounded to the ground, and the lower end opening of the side wall housing 51. And a bottom plate casing 54.
[0003]
In the pneumatic caisson method shown in FIG. 5, the working chamber 53 provided in the closed space under the bottom plate casing 54 is maintained in a pressurized state. Thereby, intrusion of groundwater from the ground surface into the work chamber 53 is prevented, and excavation work in the work chamber 53 can be performed in a dry state. In addition, an overhead traveling excavator 61 and an inboard bulldozer 62 are provided as excavating machines in the working chamber 53 under the pressurized air. These excavating machines can be operated by remote control from the ground, and excavation within a predetermined range can be freely performed. The excavated earth and sand is loaded on the vessel 58, and is carried by a soil removal carrier tower 56 installed on the ground via a material shaft 55 standing on a part of the bottom plate casing 54 and communicating with the work chamber 53. (Not shown). A known material lock 57 is provided on a part of the material shaft 55. Therefore, even when the vessel 58 loaded with unloading soil is pulled up from the work chamber 53, the airtightness of the work chamber 53 is reliably maintained.
The caisson main body 50 is laid down by excavating the ground under the blade 52 of the caisson main body 50 in a well-balanced manner so that the caisson main body 50 is uniformly subsidized. In parallel with this sinking operation, a ring-shaped concrete side wall (not shown) is sequentially constructed on the upper part of the side wall casing 51, and this concrete side wall is sequentially set in the ground as the caisson main body 50 to a predetermined depth. The side wall 51 is completed in the ground.
[0004]
In the above-described pneumatic caisson method, the frame can be set while the groundwater is reliably controlled. At the time of setting, the bottom plate box is used as the ceiling slab of the work room. For this reason, the plate thickness of the bottom plate frame must be thicker than the plate thickness at the time of installation. Moreover, in order to obtain the strength as a slab, sufficient reinforcing bars must be arranged. In order to maintain the airtightness of the working chamber, there are various structural problems such that the lower end of the side wall casing and the peripheral edge of the bottom plate casing must be joined together.
[0005]
Therefore, as shown in FIG. 6 (a), the cylindrical side wall housing portion is constituted by a double wall structure, and the outer peripheral wall 71 and the inner peripheral wall 72 are connected by the partition walls 76 arranged in a radial manner. Also proposed is a pneumatic caisson method in which a caisson 70 provided with a compartment 77 in the room is submerged, and after the caisson installation is completed, the ground region 80 partitioned by the caisson is excavated to a supporting ground position to construct a bottom plate frame not shown. (See JP-A-3-28421). In this pneumatic caisson method, the pressure working space at the bottom of the caisson is limited to the blade edge portion 75 at the lower end of the double wall, so the pressure scale can be greatly reduced, which is advantageous in terms of cost.
[0006]
[Problems to be solved by the invention]
However, since the caisson 70 having a double wall structure has a small body weight, if the ground subsidence resistance is large when the caisson is set, the set weight is insufficient and proper setting work cannot be performed. 6B, the outer peripheral wall 71 acts as a compression member due to the ring effect against the working earth pressure, but a tensile force acts on the inner peripheral wall 72. Therefore, it is necessary to arrange a sufficient amount of reinforcing bars. Further, since the radially arranged partition walls 76 serve as fulcrums at the connecting portions 78 with the wall body, a fulcrum moment or an out-of-plane shear force is generated at the connection position of the partition walls 76. For this reason, it is necessary to sufficiently carry out the shear reinforcement of the connection part 78, and the reinforcement arrangement for reinforcement becomes large. In addition, if the settlement does not proceed evenly due to the influence of the ground, excessive local stress is generated at the connecting portion with the partition wall, and the wall body may be damaged.
[0007]
In addition, in order to solve such a problem of the double wall structure, there is an example in which a blade is provided at the lower end of the inner and outer peripheral surfaces of the bottom of the single cylindrical wall having a constant wall thickness (Japanese Patent Laid-Open No. 8-4351). See the official gazette). However, this single cylindrical wall has a thin wall thickness, and it is not possible to secure an excavation work chamber having a size necessary for operating the work machine at the bottom of the wall. For this reason, quick caulking work cannot be expected with a large caisson. Moreover, there is a problem that the difference in rigidity between the bottom plate and the side wall is large, and the stability as a structure when integrated is lacking.
Further, the excavation work at the blade edge position must proceed in parallel with the work of efficiently excavating a wide bottom area and the work of carefully excavating the blade edge portion in a narrow work chamber. For this reason, it is necessary to adjust the arrangement and operation of each excavating machine.
[0008]
Therefore, the object of the present invention is to solve the problems of the prior art described above, to improve the efficiency of the laying work, to be surely connected to the bottom plate frame, and further to the maintenance pipeline after the frame is completed. It is an object of the present invention to provide a pneumatic caisson in which equipment and the like can be incorporated, and a method for installing the pneumatic caisson.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a vertical support pile for supporting a structure constructed on soft ground, and an intermediate layer whose tip is in the ground along the outer edge of the structure, the tip of which is below the soft ground. And a slant pile placed at a predetermined inclination angle so as to form a lattice wall-shaped region along the outer edge of the structure, and a horizontal force generated when a horizontal load is applied is applied to the lattice wall-shaped region. It bears in each slant pile which comprises, and it was made to suppress the stress increase of the said vertical support pile.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a pneumatic caisson of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a radial cross section of caisson body 10 of the LNG underground tank shown in FIG. 3 and a part of ground equipment. FIG. 2 shows a wall section in the circumferential direction of caisson body 10 of the LNG underground tank shown in FIG. 3 and a part of the ground equipment.
In the present embodiment, the built LNG underground tank has an outer diameter D = 80 m and a side wall thickness B = 2.5 m (upper end) to 5.2 m (lower end) as shown in FIGS. It is assumed that the capacity is about 200,000 kiloliters with a depth of 65m.
[0013]
As shown in FIG. 1, at the lower end position of the side wall casing 11 of the caisson body 10, the wall peripheral surface 11a is widened toward the center of the circle as the center of the cylindrical caisson by a height substantially equal to the bottom plate thickness T. A wall widening portion 19 is formed. Double blade openings 12 and 13 are formed at the inner peripheral lower end of the wall widening portion 19 and the outer peripheral lower end of the side wall casing 11. Thus, by providing the wall body widening portion 19 to widen the lower end of the side wall housing 11 to form a double blade edge, the support area of the entire blade edge is increased, the ground pressure is reduced, and the caisson main body 10 is inconsistent. Settlement can be prevented. Since the closed space at the lower end of the side wall housing 11 between the blade edges 12 and 13 is used as the work chamber 14, the width expansion amount Δ of the wall widening portion 19 may be set according to the scale of the work chamber 14 to be secured. Further, since the wall widening portion 19 has a shape protruding Δ inward from the side wall housing 11, when the caisson main body 10 is sunk, the friction between the upper wall body peripheral surface and the ground is cut off. It can serve as a friction cutter that reduces the settling resistance of the inner peripheral surface. The side wall thickness B and the bottom plate thickness T to be constructed later are set by the design load at the time of main installation. In addition, reinforcing bars for connecting to the bottom plate are arranged in the concrete of the wall widening portion 19, and a mechanical joint 25 is embedded in the vicinity of the inner peripheral surface. The connection with the 36 rebars 37 can be performed reliably and quickly. Thereby, it is possible to reliably resist a large stress generated at the corners of the bottom plate 36 and the side wall. Although the position of the mechanical joint 25 is schematically shown in the drawing, it goes without saying that the mechanical joint 25 is arranged at a predetermined position according to the bar arrangement plan.
[0014]
On the other hand, compressed air is supplied from a ground pressure source (not shown) into the working chamber 14 formed in the closed space at the lower end of the side wall casing 11. Further, a material shaft 15 is shown in the side wall housing 11 in the left half of FIG. The lower end of the material shaft 15 communicates with the ceiling position of the work chamber 14. In the present embodiment, the diameter of the material shaft 15 is set to 1 m. A material lock 16 is installed at the lower end of the material shaft 15. The vessel 17 is pulled up to the ground via the material lock 16 and the material shaft 15.
[0015]
A traveling rail 20 is attached to the ceiling of the work chamber 14. An overhead traveling excavator 21 is suspended on the traveling rail 20 so as to travel. This overhead traveling excavator 21 can be operated by remote control from a ground operating room (not shown). In order to control the excavation operation by the overhead traveling excavator 21 with certainty, a plurality of surveillance cameras (not shown) are provided at various locations on the ceiling and at each excavator. The imaging information obtained by this monitoring camera is displayed on the monitor installed in the operation room so as to be selectable as an image of each place. As a result, the operator in the operation room can grasp the situation in the unmanned work room 14 by switching each image. In addition, a predetermined calculation can be performed using this imaging information as input data, and a virtual reality space that matches the work space in the work room 14 can be configured. In this virtual reality space, the operator may operate the boom and bucket of the overhead traveling excavator.
[0016]
On the ground from which the material shaft 15 protrudes, a truss-structured earth removal carrier tower 30 is constructed. A transverse winch 32 is mounted on the horizontal boom 31 of the earthing carrier tower 30. By running this traverse winch 32, the vessel 17 lifted from the upper end of the material shaft 15 can be moved to the carry belt conveyor 33. The excavated sediment in the vessel 17 is transferred to the carrying belt conveyor 33 and further transferred to the sediment hopper 34 by the carrying belt conveyor 33 and dropped into the sediment hopper 34 as shown in FIG. It has become.
[0017]
1 and 2, a large number of reinforcing bars 35 assembled for the upper lot of frame concrete are shown on the ground portion of the side wall frame 11.
[0018]
FIG. 2 is a cross-sectional view showing the side wall housing 11 in a circumferential cross section (see FIG. 3) along the wall body.
As shown in the figure, a partition wall 18 that partitions the work chamber 14 is formed at a predetermined position in the work chamber 14 sandwiched between adjacent material shafts 15. A lower end 18a of the partition wall 18 bites into the ground so as to partition the work chamber 14 from the ground surface. For this reason, the adjacent working chambers 14 partitioned by the partition wall 18 can be in different pressure states. An overhead traveling excavator 21 is provided in each work chamber 14 so that the blade edges 12 and 13 of each work chamber 14 can be excavated. A sediment loading conveyor 22 is disposed in the work chamber 14. The earth and sand loading conveyor 22 can be operated by remote control, and excavated earth and sand are loaded on the vessel 17 using the earth and sand loading conveyor 22.
In addition, in the case of a small-scale side wall housing 11, since the amount of settlement of the entire housing is easy to manage, each work chamber 14 is not partitioned by the partition wall 18, and the entire work chamber 14 has the same shape as the side wall housing 11. An annular shape is also possible.
[0019]
FIG. 3 is a schematic facility layout view of the caisson body 10 and various ground facilities as viewed from above. As shown in the figure, in the present embodiment, twelve material shafts 15 are provided in the side wall casing 11. The material shaft 15 is constructed by fixing a steel pipe to be the material shaft 15 to a reinforcing rod of a concrete frame, but a predetermined position of the concrete may be boxed by a void pipe or the like.
Also, the earth removal carrier tower 30 is constructed in the number corresponding to each material shaft 15 (12), but the earth removal carrier tower provided with a boom in which a plurality of material shafts 15 enter the turning radius. 30 may be constructed, and the excavated earth and sand carried out from each material shaft 15 within the turning radius may be processed by one carrier tower 30 for earth removal. Further, in the planar layout of the present embodiment, the earth and sand hopper 34 is provided only at one place to process the earth and sand, but the earth and sand are processed by various known alternative means in consideration of the carrying capacity and route of the belt conveyor 33. May be.
[0020]
FIGS. 4A to 4C are construction state explanatory views showing a process of building a casing portion of a cylindrical underground tank by the pneumatic caisson of the present invention and its deposition method.
First, as shown in FIG. 4A, the cylindrical side wall housing 11 shown in FIG. 1 is lowered until the blade edges 12 and 13 reach the support layer 2 by a predetermined setting step. At this time, in the explanatory view, the concrete wall thickness of each lot above the wall widening portion 19 at the lower end of the side wall casing 11 is constant, but the wall thickness is related to the applied load at the depth at the time of main installation. Economic design that can be set and reduced according to the depth may be performed. The side wall of the caisson body 10 according to the present embodiment is made of concrete having a sufficient wall thickness that resists the working load at the time of installation with sufficient margin, and this is referred to as “thick wall concrete”.
And if the caisson main body 10 sinks to a predetermined depth, the ground 3 surrounded by the side wall frame 11 is excavated (see FIG. 4B). In this case, since the bottom blade edges 12 and 13 of the caisson main body 10 reach the support layer 2, the ground 3 surrounded by the side wall casing 11 is in a dry state. For this reason, the excavation work can be performed by arranging a normal excavator heavy machine 5, and the work efficiency is also very good.
[0021]
Furthermore, when the board lowering work up to the final excavation board 4 is completed, the bottom slab concrete 36 is placed as shown in FIG. At this time, the bottom slab concrete 36 can be constructed with the inner peripheral surface of the wall widening portion 19 at the lower end of the side wall being supported on the support layer 2 as a reference of the connecting portion. Since the mechanical joint 25 is embedded in the concrete in the vicinity of the inner peripheral surface of the wall widening portion 19 in the bar arrangement work, the bottom plate can be accurately and efficiently arranged by using the mechanical joint 25. . Further, in the reinforcing bar design, it is only necessary to consider the load acting at the time of actual installation, and the amount of reinforcing bar arrangement is less than in the conventional case where the bottom plate is used as a ceiling slab at the time of installation.
A known threaded rebar coupler or the like can be used as the mechanical joint 25, but a reinforcing bar rack (not shown) for accurately performing multistage bar arrangement of the bottom plate is embedded in the wall widening portion 19. You may keep it. The rebar rack is preferably an assembled shape steel.
In addition to connecting the peripheral edge of the bottom plate so as to coincide with the thickness of the wall widening portion 19 as described above, the bottom plate is hung on the upper half portion of the wall widening portion 19 and the side wall casing portion having a normal wall thickness. Or the peripheral edge of the bottom plate may be placed on the upper shoulder portion of the wall widening portion 19 and connected to the side wall casing.
[0022]
In the present embodiment, the inner concrete 41 is constructed in the work chamber 14 space at the lower end of the side wall housing 11 as necessary, and the inspection gallery 40 and the water collecting pit (not shown) are constructed. Moreover, it is also possible to pipe the pumping pipe 43 to a part of the vertical shaft 42 used as the material shaft 15 at the time of laying. The water collected in the water collecting pit can be pumped up to the ground by the pumping pipe 43 and drained.
To simplify the figure, the roof of the LNG underground tank, the equipment such as the lining membrane, and the structural material are omitted in FIG. 5C, but the same configuration as before is applied. it can. Moreover, although the above description demonstrated the application of a pneumatic caisson by exemplifying an LNG underground tank, it is clear that this pneumatic caisson can be used in a caisson foundation applied as a building foundation. Furthermore, the planar shape of the caisson is not limited to a circle, but may be an oval shape or a rectangle. In the case of a circle, the wall may be widened toward the center of the circle, but in the case of an oval or rectangular shape, the wall may be widened toward the center of the caisson planar shape.
[0023]
【The invention's effect】
As is apparent from the above description, according to the present invention, it is possible to increase the efficiency of caisson laying work, reduce the concrete frame, and construct a maintenance facility after completion.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a construction state in which a side wall housing is being deposited by a pneumatic caisson of the present invention.
FIG. 2 is a cross-sectional view illustrating a construction state in which the side wall frame is being laid by the pneumatic caisson of the present invention.
FIG. 3 is an equipment layout diagram showing ground equipment used for the pneumatic caisson of the present invention.
FIG. 4 is a construction sequence diagram illustrating a construction state in which an underground tank is being constructed by the pneumatic caisson deposition method of the present invention.
FIG. 5 is a cross-sectional view illustrating a construction state in which a caisson body is set using a conventional pneumatic caisson.
FIG. 6 is a front cross-sectional view and a plan cross-sectional view showing a configuration of a pneumatic caisson having a conventional double wall structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Caisson main body 11 Side wall housing | casing 12,13 Cutting edge 14 Working room 15 Material shaft 19 Wall body widening part 20 Traveling rail 21 Ceiling traveling type excavator 30 Carrier tower 33 for earth removal Carrying belt conveyor

Claims (2)

Widening so that the inner peripheral surface in the vicinity of the lower end of the side wall frame made of thick wall concrete protrudes, and forming a cutting edge at the lower end position and the lower end position of the outer peripheral surface to form a double cutting edge, the double cutting edge a plurality of tasks and a lower portion of the side wall skeleton sandwiched, the lower end is partitioned and formed by the plurality of partition walls provided to bite into the excavating ground surface, each chamber is capable gas to individual pressure state wherein a chamber, each of said plurality of working chambers, a drilling machine, that the upper end and a material shaft projecting on the ground its lower end through said side wall skeleton body communicating with the working chamber Pneumatic caisson. The lower part of the side wall casing sandwiched between the double edge formed by widening the inner peripheral surface in the vicinity of the lower end of the side wall casing made of thick wall concrete so as to protrude, and the lower end of the outer peripheral surface ; The drilling is performed in a plurality of working chambers defined by a plurality of partition walls provided so that the lower end bites into the excavation ground surface, the lower end communicates with each of the plurality of working chambers, and the upper end is on the ground. Through the projecting material shaft, the excavated earth and sand from each of the working chambers are individually discharged to the ground, and the side wall frame is set to a predetermined depth, and then the inner ground surrounded by the side wall frame is excavated, A method for laying a pneumatic caisson, wherein a bottom plate is constructed so that a peripheral edge is connected to an inner peripheral surface of a casing.

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