JP5700678B2 - Air supply method and air supply device to work room in pneumatic caisson - Google Patents

Description

  The present invention relates to an air supply method and an air supply device to a work chamber in a pneumatic caisson for supplying air to a work chamber in a pneumatic caisson.

  A caisson may be used as the foundation of the ground, and a pneumatic caisson is conventionally known as a caisson. The pneumatic caisson includes a cylindrical concrete casing, and a work chamber partitioned by a ceiling of the working chamber is formed at a lower portion of the cylindrical concrete casing.

  In the pneumatic caisson, a blade is provided at the lower end portion of the cylindrical concrete casing, and the cylindrical concrete casing is buried in the ground by its own weight and loading. After that, the tubular concrete frame is expanded to make the pneumatic caisson itself a desired size and used as a load when the cylindrical concrete frame is embedded.

  In addition, while the work for burying the cylindrical concrete frame is being performed, a worker is performing excavation work on the ground in the work room. At this time, in order to maintain the working chamber at a pressure higher than the groundwater pressure and prevent inflow of groundwater into the working chamber, compressed air is supplied to the working chamber from the outside of the cylindrical concrete housing (for example, Patent Document 1).

JP 2007-285052 A

  By the way, in the pneumatic caisson, when adding a cylindrical concrete frame, for example, reinforced concrete is placed at the upper end of an existing cylindrical concrete frame. When placing reinforced concrete, the reinforcing bar is installed at the upper end of the existing cylindrical concrete frame. Moreover, in recent years, the prefabrication of the reinforcing bar installed in the upper end part of the existing cylindrical concrete frame is progressing.

  At this time, the air supply pipe for supplying compressed air to the working chamber in the pneumatic caisson disclosed in Patent Document 1 supplies compressed air for applying a pressure higher than the groundwater pressure to the working chamber. For this reason, it is necessary to make the air pipe have a certain diameter. When such a large-diameter air supply pipe is used, there is a problem that the air supply pipe may interfere with the installation of the reinforcing bar, which may hinder the work of installing the reinforcing bar.

  Accordingly, an object of the present invention is to provide an air supply method and an air supply to a work room in a pneumatic caisson that can prevent an air supply pipe from becoming an obstacle when installing reinforcing bars in a cylindrical concrete casing in a pneumatic caisson. To provide an apparatus.

  In the pneumatic caisson according to the present invention for solving the above problems, the air supply method to the working chamber is performed when cast-in-place concrete is placed on the upper end of the cylindrical concrete casing in the pneumatic caisson including the cylindrical concrete casing. When the compressed air is supplied from the pneumatic feeding device arranged outside the concrete housing to the work chamber formed at the bottom of the concrete concrete housing, the first pneumatic feeding is arranged outside the cylindrical concrete housing. An air collecting apparatus including a plurality of small pneumatic feed pipes having a diameter smaller than that of the first pneumatic feed pipe and the second pneumatic feed pipe, the pipe and the second pneumatic feed pipe disposed inside the cylindrical concrete housing. Via a pneumatic feeder, and a small-diameter pneumatic feed pipe is placed between the longitudinal bars of the reinforcing bars that are placed when casting cast-in-place concrete. And air compressed air to one pressure feed pipe, air compressed air through a gas collector device and a second pneumatic flue, characterized in that it is supplied to the working chamber.

  In the pneumatic feeding method to the work room in the pneumatic caisson according to the present invention, a pneumatic pneumatic feeding device is arranged by arranging a small-diameter pneumatic feeding pipe between vertical bars in a reinforcing bar arranged when casting cast-in-place concrete. Compressed air is supplied to the first pneumatic supply pipe from the air supply, and the supplied compressed air is supplied to the working chamber via the air collecting device and the second pneumatic supply pipe. For this reason, what is necessary is just to arrange | position a small diameter pneumatic feeding pipe between reinforcing bars, and when installing a reinforcing bar in the cylindrical concrete frame in a pneumatic caisson, an air feeding pipe can be prevented from getting in the way. In addition, it is conceivable that the amount of air flowing through the small-diameter pneumatic pipe is limited, and it is difficult to sufficiently supply compressed air to the working chamber. In this regard, the air collecting device used in the present invention includes a plurality of small-diameter pneumatic pipes. For this reason, compressed air can fully be supplied with respect to a working chamber.

  Here, a manlock and a material lock communicating with the work room from the upper surface of the cylindrical concrete casing are provided in the cylindrical concrete casing, and the second pneumatic feeding pipe is connected via the manlock and the material lock. Compressed air communicated with the work chamber and supplied from the pneumatic feeder can be supplied to the work chamber.

  The pneumatic caisson is usually provided with a manlock through which a worker entering and exiting the work room passes and a material lock for discharging the excavated earth and sand from the work room. By using these manlock and material lock, compressed air can be suitably supplied to the working chamber.

  In addition, the air collecting device includes a plurality of first air collecting members including a plurality of small diameter connection ports to which one end sides of a plurality of small diameter pneumatic feeding pipes are respectively connected and a large diameter connection port to which the first pneumatic feeding pipes are connected; A plurality of small-diameter connection ports to which the other end sides of the small-diameter pneumatic feeding pipes are respectively connected, and a second air collecting member having a large-diameter connection port to which the second pneumatic feeding pipes are connected. The pipe is connected to the small diameter connection port in the first air collection member and the second gas collection member, the first pneumatic pipe is connected to the large diameter connection port in the first gas collection member, and the second pneumatic pipe is further connected. Can be connected to the large-diameter connection port of the second air collecting member to supply compressed air from the pneumatic feeding device.

  As described above, the air collecting device includes the first air collecting member and the second air collecting member, so that the connection work of the pneumatic feeding tube using the air collecting device can be smoothly performed.

  On the other hand, the air supply device to the working chamber in the pneumatic caisson according to the present invention that solves the above-described problems is when placing cast-in-place concrete on the upper end of the cylindrical concrete casing in the pneumatic caisson including the cylindrical concrete casing. An air feeding device to a working chamber in a pneumatic caisson for feeding compressed air to a working chamber formed at the bottom of the cylindrical concrete housing, the pneumatic feeding device disposed outside the cylindrical concrete housing; A first pneumatic feeding pipe connected to the pneumatic feeding device and arranged outside the cylindrical concrete casing; a second pneumatic feeding pipe arranged inside the cylindrical concrete casing and communicating with the work chamber; and a first pneumatic pressure There are a plurality of small-diameter pneumatic pipes having a smaller diameter than the pipe and the second pneumatic pipe, and the first pneumatic pipe and the second pneumatic pipe are connected so as to be able to supply air. Characterized in that it comprises a gas collector apparatus.

  In addition, the air collecting device includes a plurality of first air collecting members including a plurality of small diameter connection ports to which one end sides of a plurality of small diameter pneumatic feeding pipes are respectively connected and a large diameter connection port to which the first pneumatic feeding pipes are connected; And a second air collecting member having a plurality of small diameter connection ports to which the other ends of the small diameter pneumatic feeding pipes are respectively connected and a large diameter connection port to which the second pneumatic feeding pipes are connected. .

  According to the air supply method and the air supply device to the working room in the pneumatic caisson according to the present invention, when the reinforcing bar is installed in the cylindrical concrete frame in the pneumatic caisson, the air supply pipe is prevented from becoming an obstacle. it can.

It is a sectional side view of a pneumatic caisson. It is a perspective view of an air collection apparatus. It is process drawing which shows the construction process of a pneumatic caisson. It is process drawing which shows the process following FIG. It is a sectional side view of a pneumatic caisson using a large-diameter air pipe. It is a top view which shows the installation state of a gas collection apparatus.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each embodiment, portions having the same function are denoted by the same reference numerals, and redundant description may be omitted.

  First, a pneumatic caisson that uses the air supply method to the working room in the pneumatic caisson according to the present embodiment will be described. FIG. 1 is a sectional side view of a pneumatic caisson according to the present embodiment. As shown in FIG. 1, the pneumatic caisson N according to the present embodiment includes a cylindrical concrete casing 1 having a cylindrical shape. A reinforcing bar T is built inside the cylindrical concrete housing 1.

  A blade 11 is formed at the lower end of the cylindrical concrete housing 1, and a working ceiling 12 is provided at a lower position inside the cylindrical concrete housing 1. A work chamber 13 is formed between the work ceiling 12 located below the work ceiling 12 and at the bottom of the cylindrical concrete housing 1 and the ground G. A friction cut 14 is formed on the side of the cylindrical concrete housing 1.

  Further, a manlock 15 and a material lock 16 communicating from the upper surface of the tubular concrete housing 1 are provided inside the tubular concrete housing 1. Both the manlock 15 and the material lock 16 have a cylindrical shape, and the manlock 15 is formed with stairs that reach the working chamber from the upper opening through the lower opening. An operator can enter the work room 13 through the stairs.

  On the other hand, the material lock 16 is used when the soil excavated in the work chamber 13 is discharged by the crane C or the like. In addition, the tubular concrete housing 1 is provided with an air supply pipe 17 and an exhaust pipe 18. Further, the manlock 15 and the material lock 16 are provided with similar air supply pipes (not shown). The air supply pipe 17 is used to send air into the work chamber 13. On the other hand, the exhaust pipe 18 is used to exhaust the air in the working chamber 13 to the outside. The exhaust pipe 18 is provided with a check valve to prevent a backflow of air into the working chamber 13.

  Further, an air supply device 2 for supplying compressed air to the work chamber 13 is provided on the side of the cylindrical concrete housing 1. By supplying compressed air from the air supply device 2 to the work chamber 13, the inside of the work chamber 13 is maintained at a pressure higher than the groundwater pressure. The air feeding device 2 includes an air tank 21 and a compressor 22 that is a pneumatic feeding device. The air tank 21 stores air to be supplied to the work chamber 13, and the compressor 22 sends the air in the air tank 21 to the work chamber 13.

  In addition, the air supply device 2 includes an upstream high-pressure hose 23 that is a first pneumatic feeding pipe and a downstream high-pressure hose 24 that is a second pneumatic feeding pipe of the present invention. A plurality of upstream high-pressure hoses 23 and downstream high-pressure hoses 24 are provided, both of which are flexible tubes. Further, when the reinforcing bar is being built, the upstream high pressure hose 23 and the downstream high pressure hose 24 are connected by the air collecting device 3.

  One end side of the upstream high-pressure hose 23 is connected to the air tank 21, and the other end side is connected to the air collecting device 3. In this way, the upstream high-pressure hose 23 and the downstream high-pressure hose 24 are provided across the upper end of the cylindrical concrete housing 1, and the upstream high-pressure hose 23 is disposed outside the tubular concrete housing 1, and the downstream side A high-pressure hose 24 is disposed inside the cylindrical concrete housing 1. One end side of the plurality of downstream high-pressure hoses 24 is connected to the air collecting device 3, and the other end side is connected to the manlock 15, the material lock 16, and the air supply pipe 17.

  Furthermore, as shown in FIG. 2, the air collecting device 3 includes an upstream base member 31 that is a first air collecting member of the present invention and a downstream base member 32 that is a second air collecting member. The upstream base member 31 and the downstream base member 32 are connected via a plurality of small diameter air supply pipes 33, which are six small diameter pneumatic supply pipes in this embodiment.

  The upstream base member 31 includes a large-diameter connection port connected to the upstream high-pressure hose 23 and a plurality of small-diameter connection ports connected to the small-diameter air supply pipe 33. Similarly, the downstream side base member 32 includes a large diameter connection port connected to the downstream side air supply pipe and a plurality of small diameter connection ports connected to the small diameter air supply pipe 33. Note that the number of the small-diameter air supply pipes 33 may be other than six. Each of the small-diameter air supply pipes 33 is a flexible pipe. One end of the small-diameter air supply pipe 33 is attached to the upstream base member 31, and the other end side is attached to the downstream base member 32. It has been.

  In this way, compressed air can flow between the air tank 21 and the work chamber 13 in the cylindrical concrete housing 1 via the upstream high-pressure hose 23, the air collecting device 3, the downstream high-pressure hose 24, the air supply pipe 17, and the like. It is said that. Further, in the air collecting device 3, compressed air is supplied between the upstream high-pressure hose 23 and the downstream high-pressure hose 24 through the upstream base member 31, the small-diameter air supply pipe 33, and the downstream base member 32. It is possible.

  The small-diameter air supply pipe 33 is attached to the downstream base member 32 via a connection joint 34. The connection joint 34 is a member that can be connected, for example, by screwing the female screw portion into the male screw portion. For this reason, the small-diameter air supply pipe 33 can be easily detached from the downstream side base member 32 by the connection joint 34.

  On the other hand, when the reinforcement work is not performed, as shown in FIG. 3, the air tank 21, the manlock 15, the material lock 16, and the air supply pipe 17 are used by the high-pressure hose 50 without using the air collecting device 3. And connected. The connection between the air tank 21 and the manlock 15, the material lock 16, and the air supply pipe 17 by the high-pressure hose 50 is a conventionally performed technique.

  Next, a method for supplying air to the work chamber in the pneumatic caisson according to the present embodiment will be described. The air supply of compressed air to the work chamber in the pneumatic caisson according to the present embodiment is characterized by the air supply method when constructing the pneumatic caisson. Hereinafter, a method for supplying air to the work room will be described together with a procedure for constructing the pneumatic caisson.

  Construction of the pneumatic caisson starts embedding in the ground G from the portion of the blade 11, and then casts cast-in-place concrete into the cylindrical trunk and adds the trunk. The blade 11 sinks with respect to the ground by a load such as a loading load by the added concrete trunk, and is buried in the ground by performing excavation work in the work chamber 13. After that, a pneumatic caisson is constructed by performing multiple additions of concrete.

  FIG. 4A is a side view of the pneumatic caisson in the middle of construction and before a new concrete is added. 4 and 5, members such as manlock 15 and material lock 16 are omitted. Further, while the pneumatic caisson is being constructed, the working chamber 13 is in principle always supplied with compressed air via the air supply pipe 17 shown in FIG.

  As shown in FIG. 4 (a), when the concrete addition work is started, the upper end portion of the reinforcing bar T provided in the existing cylindrical concrete casing 1 protrudes from the top end surface of the cylindrical concrete casing 1. Yes. A high pressure hose 50 is passed above the reinforcing bar T, and compressed air is supplied to the work chamber 13 via the high pressure hose 50 and the air supply pipe 17 and the like.

  From this state, the air collecting device 3 is installed in a state where the small-diameter air supply pipe 33 in the air collecting device 3 is disposed between the reinforcing bars T protruding from the top end surface of the cylindrical concrete housing 1. Subsequently, the upstream hose member 23 and the downstream hose member 24 are connected to the air collecting device 3. Thus, compressed air is supplied from the air tank 21 to the air supply pipe 17 and the like via the air collecting device 3, and compressed air is supplied to the work chamber 13 via the air supply pipe 17 and the like.

  Subsequently, new concrete is added to the cylindrical concrete housing 1. For this reason, as shown in FIG. 4B, the prefabricated reinforcing bar PT, which is a prefabricated reinforcing bar, is suspended by a crane C via a balance H. Moreover, before installing the prefabricated reinforcing bar PT in the cylindrical concrete housing 1, the high-pressure hose 50 is vented and removed.

  The prefabricated reinforcing bar PT is temporarily fixed by a temporary fixing steel material S in which a plurality of hoop bars are arranged in the vertical direction and extend along the vertical direction. In FIG. 4B to FIG. 5B, the hoop bars and the newly installed vertical bars in the prefabricated reinforcing bar PT are drawn in a side view rather than a cross section.

  Then, as shown in FIG.4 (c), the prefabricated reinforcement PT is mounted in the top end surface of the cylindrical concrete housing 1. FIG. Then, the prefabricated reinforcing bar PT is removed from the balance H. At this time, the prefabricated steel bar PT is temporarily fixed by the temporary fixing steel material S, and the temporary fixing steel material S is placed at a position avoiding the small diameter air supply pipe 33 in the air collecting device 3.

  When the prefabricated reinforcing bar PT has been installed, as shown in FIG. 5A, the high pressure hose 50 is connected above the prefabricated reinforcing bar PT to restore the compressed air supply path via the high pressure hose 50. Air supply through the hose 50 is resumed. In parallel with the connection of the high-pressure hose 50, the air supply path via the air collection device 3 is blocked and the air collection device 3 is removed. In this way, the air supply path for the work chamber 13 is switched from the path passing through the air collecting device 3 to the path passing through the high-pressure hose 50. During the air supply path switching operation, the excavation work in the work chamber 13 is interrupted, and when the air supply path switching operation is completed, the excavation work is resumed.

  Then, as shown in FIG.5 (b), many vertical bars HT are attached with respect to the hoop of the prefabricated reinforcing bar PT, and hoops are connected through the vertical bars HT. Further, it is removed from the temporary fastening steel material S. Furthermore, the newly installed vertical bars HT are bound with the reinforcing bars T protruding from the top end surface of the cylindrical concrete housing 1.

  When the prefabricated reinforcing bar PT and the vertical reinforcing bar HT are thus built, a mold frame (not shown) is provided around the prefabricated reinforcing bar PT and the vertical reinforcing bar HT, and concrete is placed in the mold frame. Here, a formwork is provided and concrete is laid. And as shown in FIG.5 (c), the cylindrical concrete housing 1 sinks by the loading of the newly laid concrete, the excavation work in the working chamber 13, etc. As shown in FIG. Thereafter, the state shown in FIG. 4A is obtained, and the same process is repeated until the tubular concrete casing 1 reaches a predetermined height, and the entire pneumatic caisson N is constructed.

  When constructing the pneumatic caisson N in this way, air is supplied to the working chamber 13 via the air collecting device 3. Here, for example, as shown in FIG. 3, without passing through the air collecting device 3, if the compressed air is directly supplied from the air tank 21 to the material lock 16 by the large-diameter air supply pipe 50, the tubular concrete When the reinforcing bar is built in the top end surface of the casing 1, the air supply pipe 50 becomes an obstacle.

  On the other hand, in the present embodiment, the air collecting device 3 is used to supply air to the work chamber 13, and the air collecting device 3 includes a small diameter air supply pipe 33. For this reason, as shown in FIG. 6, when the vertical bars HT are built and the vertical bars HT and the existing reinforcing bars T are joined, the small-diameter air supply pipe 33 is disposed between the vertical bars HT and the reinforcing bars T. be able to. For this reason, when constructing a reinforcing bar such as the vertical bar HT, the pneumatic feeding pipe can be prevented from becoming an obstacle.

  Further, there is a concern that the amount of air supplied to the working chamber 13 is reduced simply by reducing the diameter of the pressure feeding tube. Here, in the present embodiment, a plurality of small-diameter air supply pipes 33 in the air collecting device 3 are provided. For this reason, a sufficient amount of compressed air is supplied to the work chamber 13. Further, a plurality of small diameter air supply pipes 33 are connected by the upstream base member 31 and the downstream base member 32. For this reason, although a plurality of small-diameter air supply tubes 33 are provided, the plurality of small-diameter air supply tubes 33 can be easily connected.

  In the present embodiment, the small-diameter air supply pipe 33 and the downstream base member 32 are connected via the connection joint 34, and the connection joint 34 can be easily attached and detached. For this reason, even after the reinforcing bars such as the vertical bars HT are installed, the air collecting device 3 can be easily removed from between the reinforcing bars by removing the connecting joint 34. And it can be moved and attached to the upper end side of the newly constructed cylindrical concrete housing 1.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the air feeding method according to the present invention can be used also when a non-prefabricated reinforcing bar is built in which the reinforcing bar placed on the pneumatic caisson N is a prefabricated reinforcing bar PT. .

  Moreover, in the said embodiment, although the prefabricated reinforcement PT prefabricates only the hoop reinforcement, it can also be set as the aspect prefabricated also including the vertical reinforcement. Furthermore, in the above embodiment, the air supply pipe is connected by the air collecting device 3, but when an exhaust pipe that straddles the upper end of the cylindrical concrete housing 1 similar to the air supply pipe is provided, the exhaust pipe is connected to the air collection pipe. It can also be set as the aspect connected with an apparatus. Furthermore, in the above-described embodiment, compressed air is supplied to the working chamber 13 via the manlock 15, the material lock 16, and the air supply pipe 17, but the compressed air is supplied only via the air supply pipe 17. You can also. Alternatively, the compressed air can be supplied from any one of the manlock 15, the material lock 16, and the air supply pipe 17, or the compressed air can be supplied from other paths.

  On the other hand, in the said embodiment, although the pipe | tube which has flexibility is used as the small diameter air supply pipe | tube 33 in the air collection apparatus 3, a non-flexible pipe body can also be used. In the above embodiment, the connection joint 34 is provided between the small-diameter air supply pipe 33 and the downstream base member 32, but the connection joint is provided between the small-diameter air supply pipe 33 and the upstream base member 31. It can also be set as the aspect provided. Furthermore, it can also be set as the aspect which connects the small diameter air supply pipe | tube 33 and the base members 31 and 32, without using a connection coupling.

DESCRIPTION OF SYMBOLS 1 ... Cylindrical concrete housing 2 ... Air supply apparatus 3 ... Air collection apparatus 11 ... Blade 12 ... Work ceiling 13 ... Work room 14 ... Friction cut 15 ... Manlock 16 ... Material lock 17 ... Air supply pipe 18 ... Exhaust pipe 21 ... Air Tank 22 ... Compressor 23 ... Upstream side air supply pipe 24 ... Downstream side air supply pipe 31 ... Upstream side base member 32 ... Downstream side base member 33 ... Small diameter air supply pipe 34 ... Connection joint 50 ... Air supply pipe C ... Crane G ... Ground H ... Balance HT ... Vertical rebar N ... Pneumatic caisson PT ... Prefabricated rebar S ... Steel T ... Rebar

Claims (5)

When placing cast-in-place concrete on the upper end of the cylindrical concrete casing in a pneumatic caisson including the cylindrical concrete casing, the outer side of the concrete casing with respect to a working chamber formed at the bottom of the cylindrical concrete casing In supplying compressed air from the pneumatic feeder arranged in
The first pneumatic feeding pipe and the second pneumatic feeding pipe arranged on the outer side of the cylindrical concrete casing and the second pneumatic feeding pipe arranged on the inner side of the cylindrical concrete casing. It is connected so as to be able to supply air through an air collecting device having a plurality of small-diameter pneumatic pipes that are thinner than
Placing the small-diameter pneumatic feeding pipe between the longitudinal bars in the reinforcing bars disposed when placing the cast-in-place concrete;
Compressed air is supplied from the pneumatic feeding device to the first pneumatic feeding tube, and the compressed air thus fed is supplied to the working chamber via the air collecting device and the second pneumatic feeding tube. An air supply method to a work room in a pneumatic caisson characterized by the above. For the working chamber, a manlock and a material lock communicating from the upper surface of the cylindrical concrete casing are provided in the cylindrical concrete casing,
The said 2nd pneumatic feeding pipe is connected to the said working chamber via the said man lock and the said material lock, The compressed air sent from the said pneumatic feeding apparatus is supplied to the said working chamber. The air supply method to the working room in the pneumatic caisson described. The air collecting device includes a plurality of small diameter connection ports to which one end sides of a plurality of small diameter pneumatic feeding pipes are respectively connected, and a first air collecting device having a large diameter connection port to which the first pneumatic feeding pipe is connected;
A plurality of small-diameter connection ports to which the other end sides of the plurality of small-diameter pneumatic feeding pipes are respectively connected, and a second air collecting device including a large-diameter connection port to which the second pneumatic feeding pipe is connected,
The small-diameter pneumatic pipe is connected to the small-diameter connection port in the first air collector and the second air-collector, and the first pneumatic pipe is connected to a large-diameter connection port in the first air collector. Further, the pneumatic device according to claim 1 or 2, wherein the pneumatic pressure feeding device feeds compressed air from the pneumatic feeding device by connecting the second pneumatic feeding tube to a large-diameter connection port in the second air collecting device. Air supply method to the work room in the caisson. Pneumatic for supplying compressed air to a working chamber formed at the bottom of the cylindrical concrete casing when placing cast-in-place concrete on the upper end of the cylindrical concrete casing in a pneumatic caisson having a cylindrical concrete casing An air supply device to the work room in the caisson,
A pneumatic feeding device disposed outside the cylindrical concrete housing;
A first pneumatic feeding pipe connected to the pneumatic feeding device and disposed outside the cylindrical concrete housing;
A second pneumatic feeding pipe disposed inside the cylindrical concrete housing and communicating with the working chamber;
A plurality of small-diameter pneumatic pipes having a diameter smaller than that of the first pneumatic pipe and the second pneumatic pipe, and the first pneumatic pipe and the second pneumatic pipe are connected so as to be able to feed air. Qi device,
An air supply device to a work room in a pneumatic caisson characterized by comprising: The air collecting device includes a plurality of small diameter connection ports to which one end sides of a plurality of small diameter pneumatic feeding pipes are respectively connected and a first air collecting member having a large diameter connection port to which the first pneumatic feeding pipes are connected;
5. A second air collecting member including a plurality of small diameter connection ports to which the other end sides of the plurality of small diameter pneumatic feeding pipes are respectively connected and a large diameter connection port to which the second pneumatic feeding pipes are connected. Air supply device to the working room in the described pneumatic caisson.

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