JP6199453B2 - Construction method of breakwater - Google Patents

Description

  The present invention relates to a method for constructing a breakwater.

  As a method of constructing a liquid breakwater (wall) for an above-ground LNG tank, an inner frame (steel liner plate, precast concrete segment, etc.) is installed at a position that becomes the inner peripheral surface of the wall, and There is known a method in which an outer mold is installed at a position to be a surface, and concrete is placed between the inner mold and the outer mold (for example, see Patent Document 1). The inner mold is a so-called remaining mold and is left as it is after the concrete is hardened.

  The inner formwork (segment) is assembled by fixing it to the existing part of the wall or the lower inner formwork, but the lowermost inner formwork is assembled while supporting each segment with a temporary support member, etc. ing.

JP 2010-106501 A

The assembly of the segments needs to be performed while performing fine adjustment, but the segment fixed to the support member requires time and effort for fine adjustment.
In addition, since a large support member is required for the inner formwork of a large breakwater, it takes time to install and remove the support member and the material cost increases.

  An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to propose a method for constructing a breakwater excellent in workability and economy.

  In order to solve the above problems, a construction method of a breakwater according to the present invention is a construction method of a breakwater that forms a wall body rising from a bottom plate, and a plurality of segments placed on the upper surface of the bottom plate are ring-shaped. Forming a lowermost step of the inner mold frame by connecting to each other, a step of setting an outer mold frame outside the inner mold frame with a gap from the inner mold frame, the inner mold frame and the outer mold Placing the concrete of the leg of the wall body between the mold frame, the ring-shaped inner mold frame is self-supporting, and the outer mold frame is inserted through the separator. It is characterized by being connected to the inner formwork.

  According to such a construction method of the breakwater, the inner mold frame is self-supporting without being fixed to the bottom slab, so that fine adjustment can be easily performed and the workability is excellent.

In the present specification, “self-standing” means a state in which the support member is standing without using a support member or a fixing member. The inner mold frame in which a plurality of segments are connected in a ring shape is stable and independent because the force is dispersed between the segments and the stress concentration is suppressed.
In addition, in this specification, the “ring shape” includes not only a circular shape (ring) but also a state in which a part of the circular shape is lost (C shape).

  In the step of forming the lowermost stage of the inner mold, the plurality of segments may be connected in a state where at least a part of the segments is supported by a support member.

  According to the construction method of a breakwater according to the present invention, a breakwater can be constructed easily and inexpensively.

(A) is sectional drawing which shows the structure of a wall body, (b) is the lower part enlarged view of (a). (A) is a top view which shows a residual formwork, (b) is the sectional view on the AA line of (b) of FIG. (A) is sectional drawing which shows the construction condition of the 1st lot, (b) is sectional drawing which shows the construction condition of the 2nd lot. It is sectional drawing which shows the state which the concrete placement of the n-1st lot was completed.

  The wall body W according to the embodiment of the present invention is a liquid breakwater of a ground LNG tank and has a cylindrical shape in plan view.

  As shown in FIG. 1A, the wall body W is a prestressed concrete structure that rises from the bottom slab B, and is left on the concrete wall portion 1 made of cast-in-place concrete and the inner surface of the concrete wall portion 1. The remaining mold (inner mold) 2 is provided.

  As shown in FIG. 1B, in addition to the wall bars 1a and 1a, a circumferential PC steel material 1b, a longitudinal PC steel material, and the like are embedded in the concrete wall portion 1. The wall stripe 1a is a combination of vertical and horizontal stripes in a grid pattern. The circumferential direction PC steel material 1b is made of a PC steel wire extending from one pilaster to another pilaster, and is inserted into a sheath 1c (hereinafter referred to as “lateral sheath 1c”) extending in the circumferential direction. The transverse sheath 1c is disposed along the wall bars 1a on the outer peripheral side (opposite side of the remaining mold 2). The longitudinal PC steel material 1d is composed of a PC steel rod extending from the lower end portion of the concrete wall portion 1 to the upper end portion.

  The remaining mold 2 is formed by connecting a plurality of segments 2a, 2a... In the circumferential direction and the vertical direction (see FIG. 2). The segment 2a is a precast concrete product having a rectangular shape in front view and an arc shape in plan view. Although illustration is omitted, the segment 2a is integrated with an insert nut for an outer tank liner plate, an insert nut for a separator, and a concrete wall 1 in addition to a joint box opened to the concrete wall 1 side. The shear transmission member is embedded.

When the wall body W is constructed, it is divided into n lots (n is an integer of 2 or more) times and is started up by several m.
That is, the construction of the wall W includes the inner mold forming process for forming the first lot, the outer mold setting process and the placing process, and the upper inner mold forming for forming the second and subsequent lots. A process, an upper outer formwork installation process, and an upper placement process.

The inner mold frame forming step is a step of forming the inner mold frame 21 by connecting a plurality of segments 2a, 2a,.
The inner mold 21 (remaining mold 2) has a ring shape in plan view as shown in FIG. The lower lot (for example, the first and second lots) of the inner mold 21 is formed in a C shape in plan view by forming an opening for carrying in materials and the like. For example, the third and subsequent lots) are formed in an annular shape.

  As shown in FIG. 3A, the segment 2a is disposed on the upper surface of the bottom plate B and then connected to another adjacent segment 2a. At this time, a part of the segments 2a is supported by a multipurpose post (not shown) rising from the bottom plate B. Note that the support member of the segment 2a is not limited to the multipurpose post, and a temporary member, a scaffold, or the like may be used.

Here, the multipurpose post is made of an H-shaped steel rooted in the bottom slab B, and is disposed at the center of the concrete wall 1 in the wall thickness direction. The multipurpose post has a rigidity that can stand by itself even in the absence of concrete.
In addition, the material which comprises a multipurpose post is not limited to H-section steel, For example, I-section steel, C-section steel, a steel pipe, etc. may be used.

The segment 2a is suspended by a crane (not shown) and placed on the upper surface of the bottom plate B. At this time, the installation position is confirmed using a target (not shown) installed on the surface of the segment 2a, and the installation position of the segment 2a is adjusted as necessary.
Next, using the joint box (not shown) provided in each segment 2a, the segments 2a adjacent in the circumferential direction are bolted together.

  The inclination and height adjustment of the segment 2a are performed by interposing a height adjusting member (not shown) between the segment 2a and the bottom plate B. For example, a steel plate or the like may be used as the height adjusting member.

  The segment 2a may be supported by the multipurpose post (support member) as necessary. For example, in an unstable situation such as the beginning of assembling the segments 2a (inner form 21), the segments 2a are supported so as not to fall down. On the other hand, when the plurality of segments 2a are connected in an arc shape and stabilized, it is not necessary to support the segment 2a.

When the inner mold 21 is installed, necessary wall reinforcement 1a is arranged and the circumferential PC steel material 1b and the vertical PC steel material 1d are installed.
The wall reinforcement 1a may be assembled at a reinforcing bar processing site in the construction site and built in a state of a reinforcing bar net or a reinforcing bar rod.

The outer formwork installation process is a process of installing the outer formwork 3 outside the inner formwork 21 with a gap from the inner formwork 21 as shown in FIG.
The outer mold 3 is connected to the inner mold 21 via the separators 5 and 5.

In the present embodiment, the upper and lower two-stage separators 5 and 5 are disposed, but the number of the separators 5, the arrangement pitch, and the like are not limited.
The outer mold 3 has a strength that does not deform due to the side pressure of the concrete C.

The placing process is a process for placing concrete C between the inner mold 21 and the outer mold 3.
The concrete C is placed from two locations facing each other across the center of the inner mold 21 (see FIG. 2A). When the placement surface of the concrete C reaches a predetermined height, the concrete C is placed from two locations facing each other across the center of the other inner mold 21.

  The concrete C is placed by placing the concrete C to a position lower than the top edge of the outer mold 3 using a concrete pressure feeding pipe.

  With the placement of the concrete C, the side pressure of the concrete C acting on the outer mold 3 acts on the inner mold 21 via the separator 5. That is, the inner mold 21 is responsible for the lateral pressure of the cast concrete C.

When the construction of the first lot is completed, the second and subsequent lots are formed.
The upper inner formwork forming step is a step of forming the upper inner formwork 22 by connecting a plurality of segments 2 a and 2 a in the circumferential direction and the vertical direction on the upper surface of the inner mold 2.

As shown in FIG. 3B, the upper inner form 22 is formed by fixing the segment 2a to the upper surface of the existing segment 2a.
The upper inner mold 22 is formed of the same type of segment 2 a as the inner mold 21 and is left on the inner surface of the concrete wall 1.

  The segment 2a is suspended by a crane (not shown) and placed on the upper end surface of the existing remaining mold 2 (inner mold 21) without using a support member or the like. At this time, the installation position is confirmed by measuring the target installed in the segment 2a, and the segment 2a installation position is adjusted as necessary. Next, using a joint box (not shown) provided in each segment 2a, it is bolted to the existing remaining mold 2 and is bolted to another segment 2a adjacent in the circumferential direction. A frame 22 is formed.

Next, the necessary bar arrangements 1a and 1a and the arrangement of the circumferential PC steel material 1b and the vertical PC steel material 1d are performed.
The installation position of the bar arrangement 1a is confirmed by measuring an offset amount with respect to the upper inner form 22.

The lower end of the new wall reinforcement 1a is connected to the existing wall reinforcement 1a, 1a protruding from the existing concrete wall 1 _n-1 through an appropriate reinforcing steel joint (lap joint, mechanical joint, etc.). The wall reinforcement 1a may be assembled at a reinforcing bar processing site in the construction site and built in a state of a reinforcing bar net or a reinforcing bar rod.

  The circumferential PC steel material 1b is arranged in a state of being inserted through the transverse sheath 1c. The transverse sheath 1c (circumferential PC steel material 1b) is disposed along the outer wall reinforcement 1a. A fixing tool fixed to a pilaster (not shown) is attached to the end of the circumferential PC steel material 1b.

Further, the lower end portion of the longitudinal PC steel material 1d is connected to an existing longitudinal PC steel material protruding from the existing concrete wall portion 1 _n-1 via an appropriate mechanical joint. The installation position of the longitudinal PC steel material 1d is confirmed by measuring the offset amount from the upper inner formwork 21.

The upper outer formwork installation step includes a step of installing an upper outer formwork 31 on the outside of the upper inner formwork 22 with a gap from the upper inner formwork 22,
The upper outer mold 31 is connected to the upper remaining mold 22 via the separators 5 and 5.

The upper outer mold 31 is fixed to the upper surface of the existing outer mold 3.
The upper outer formwork 31 is installed by using a temporary scaffold 32 disposed outside the upper outer formwork 31.

  The upper placement process is a process of placing concrete C between the upper inner mold 22 and the upper outer mold 31. The details of the concrete C placing method in the upper placing process are the same as in the placing process.

As described above, in each lot after the second time, a new part having a predetermined height is formed on the existing part (the existing concrete wall part 1 _n-1 and the existing residual formwork 2 _n-1 ) formed in the previous lot. (New concrete wall 1 _n and new remaining mold 2 _n ) are formed.

The “existing concrete wall portion 1 _n-1 ” and the “existing remaining formwork 2 _n-1 ” are formed in the previous (n−1) th lot of the concrete wall portion 1 and the remaining formwork 2. The “new concrete wall portion 1 _n ” and the “new residual formwork 2 _n ” refer to portions formed in the current (n-th) lot. The subscript attached to the code corresponds to the number of lots.

FIG. 4 is a diagram showing a state where the concrete placement in the (n-1) th lot is completed.
The wall bars 1a and 1a and the longitudinal sheath 1d (longitudinal PC steel material) protrude from the upper end surface of the concrete (existing concrete wall portion 1 _n-1 ) placed in the ( _n-1 ) _th lot. The existing remaining formwork 2 _n-1 extends upward from the upper end of the existing concrete wall 1 _n-1 and serves as a fall prevention fence for the next lot work.

When the wall portion 1 reaches a predetermined height or more, the wall portion 1 may be constructed using the scaffold unit 4 instead of the upper mold 31 and the temporary scaffold 32.
Although there is no restriction | limiting in the structure of the scaffold unit 4, the thing of this embodiment is a work scaffold with a formwork, and supports the upper outer formwork 41 and the upper outer formwork 41 which shape | mold the outer surface of the concrete wall part 1. In addition, the lower scaffolding plate 42 serving as a work floor, the support girders 43 that support the lower scaffolding plates 42 from below, the brackets 44 that support the support girders 43 from below, and the upper scaffolding supported on the upper part of the upper outer formwork 41 A plate 45 and the like are provided. The upper outer frame 41 is slidable in the inner and outer directions of the wall body W (left and right in the drawing).

An insert nut 1e for fixing the scaffold unit 4 is embedded at an appropriate position of the existing concrete wall 1 _n-1 .
In addition, it is not always necessary to use the scaffold unit 4 for the work scaffold.

  Since the main work procedures in each lot after the second lot are the same, detailed description is omitted.

  When all the lots are completed, a tensile force is applied to the circumferential PC steel material 1b and the longitudinal PC steel material 1d, and prestress is introduced to the wall body W.

Thus, according to the construction method (the construction method of the breakwater) of the wall body W according to the present embodiment, since each segment 2a is not fixed to the bottom plate B, fine adjustment can be easily performed. Excellent workability.
Further, by omitting the support member of the segment 2a, it is possible to omit the trouble of installing the support member and the cost required for the support member.

  Since the concrete C is placed from two locations facing each other across the center of the inner mold 21, the side pressure at the time of concrete placement can be applied equally to the inner mold 21 and the outer mold 3. .

  Since the outer mold 3 can take a reaction force from the stable inner mold 21 via the separator 5, a temporary material for resisting the side pressure is not necessary. Therefore, the trouble and expense for installing temporary materials can be omitted.

The inner mold frame formed of segments connected in a ring shape is stable and independent because force is dispersed between the segments and stress concentration is suppressed. For this reason, it is possible to take a lateral pressure at the time of placing the concrete acting on the outer mold 3 connected via the separator 5.
Further, since the load is canceled as compared with the straight wall, it is possible to reduce the member thickness and the amount of reinforcing bars of the segment itself.

  Since the concrete side pressure acts equally on the inner mold 21 in the center direction, ring compression acts on the inner mold 21 and the movement and deformation of the inner mold 21 are suppressed. Therefore, the construction of the wall body W can be performed with high quality.

  The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and the above-described components can be appropriately changed without departing from the spirit of the present invention.

  For example, in the said embodiment, although the case where the segment which comprises the residual formwork 2 was a precast concrete product was illustrated, you may use segments made from steel. Moreover, you may form the residual formwork 2 using the segment by which the outer tank liner plate was affixed previously.

W Wall 1 Concrete wall 2 Remaining mold 21 Inner mold 22 Upper inner mold 3 Outer mold 31 Upper outer mold 4 Scaffolding unit 41 Upper outer mold 5 Separator B Bottom plate C Concrete

Claims (2)

A construction method of a breakwater that forms a wall that rises from a bottom plate,
Connecting a plurality of segments placed on the upper surface of the bottom plate in a ring shape to form the lowermost stage of the inner mold, and
A step of setting an outer mold on the outside of the inner mold with a gap from the inner mold; and
Placing the concrete of the leg of the wall between the inner mold and the outer mold,
The ring-shaped inner mold is self-supporting,
The outer mold is connected to the inner mold via a separator. The method for constructing a breakwater.   The step of forming the lowermost step of the inner mold frame connects the plurality of segments in a state where at least a part of the segments is supported by a support member. Construction method.

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