JP2002188159A - Execution method for underwater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the residual stress of a steel pipe sheet pile caused when the upper section of a steel pipe sheet pile foundation is used as a temporary block wall in the execution of the steel pipe sheet pile foundation of an underwater structure such as a pier, eliminate the timbering in a well or the form scaffold of an upper skeleton, reduce the cost, and shorten the construction period. SOLUTION: Steel pipe sheet piles 1 are placed in the underground foundation ground A to form a well 10, and the steel pipe sheet piles 1 are cut and removed at the prescribed position. An upper skeleton 11 such as a steel shell manufactured in advance is sunk on the head section of the well 10, and the upper opening of the well 10 is watertightly covered with a footing 11a. The water level in the well head section is lowered to fix the upper skeleton 11 to the well head section with water pressure, then aerated concrete is placed in the dried well head section, thereby the footing 11a of the upper skeleton 11 and the head section of the well 10 are integrally and rigidly connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing an underwater structure such as a pier constructed underwater with a sheet pile foundation.

[0002]

2. Description of the Related Art A steel pipe sheet pile foundation is formed by casting a steel pipe sheet pile on site to form a circular, oval, rectangular, or other well-shaped closed cross section, and a top plate is provided at the head of the well to form a rigid connection. This is a substructure in which not only the rigidity of the steel pipe sheet pile alone but also the rigidity of the entire well is provided, and a predetermined horizontal resistance and vertical supporting force can be obtained. In addition, this steel pipe sheet pile foundation can adopt a temporary closing method, and there is an advantage that the steel pipe sheet pile can be used as a temporary closing wall and a foundation body at the time of building concrete.

FIG. 2 shows an example of the structure of a conventional steel pipe sheet pile foundation on a pier and a standard construction method.
The construction is generally performed in the following procedure. (1) Install a workbench and guides at the location where the piers are to be installed, and cast steel pipe sheet piles 1 using the guide frames 2. The outer tubular steel sheet pile 1 forms a well 3 having a closed cross section such as a circle. A bulkhead steel pipe sheet pile and a single-story pile are driven into the inside of the well 3 as necessary.

(2) A shoring is installed at the head of the well pipe 3, a waterproofing work of the joint of the outer steel pipe sheet pile 1 and a concrete filling work of the outer steel pipe sheet pile 1 are performed, and then the inside of the well pipe 3 is excavated. Pile concrete 4 on the bottom sand (gravel).

[0005] (3) While the support (belly, cut beam, fire beam) 5 is installed in the well 3, the water in the well 3 is pumped up gradually, and the inside of the well 3 is dried up.

(4) A connector 6 is attached to the inner surface of the well tube 3 at the position of the top slab, and a reinforcing bar of the top slab is arranged. After placing concrete on top slab, support 5
Are dismantled and removed, and a steel formwork and a scaffolding support are assembled around the skeleton, and skeleton concrete 8 is sequentially poured.

(5) The upper part of the top slab concrete 7 is backfilled, water is injected into the well 3, and then an underwater cutting machine is inserted into the outer periphery of the steel pipe sheet pile 1 to put the steel pipe sheet pile 1 at the upper end of the foundation main body. Cut and pull out the temporary cutoff section of the steel pipe sheet pile 1.

(6) By removing the temporary material, an upper frame (pier) in which the lower portion is rigidly connected integrally to the head of the steel pipe sheet pile foundation main body is completed.

[0009]

However, the structure and construction method of the conventional steel pipe sheet pile foundation as described above has the following problems.

(1) Due to the structure in which the upper portion of the well base is used as a temporary cut-off portion, when designing, it is generated by the residual stress of the steel pipe sheet pile generated by soil water pressure and the like during construction and by the design external force after completion. It is necessary to synthesize and evaluate the stress levels, and the steel sheet piles and the like need to have a strength higher than the strength as a completed foundation, and the steel sheet piles and the like become large.

(2) Since the inside of the well is excavated and dried up for the construction of the upper frame, a support work is required in the well, which increases the cost and the construction period.

(3) When constructing the upper frame, it is necessary to assemble the scaffold of the formwork in the well, and in order to secure this work space, the diameter of the well becomes larger than necessary.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to eliminate the residual stress of a sheet pile by using the upper part of the sheet pile foundation as a temporary cutoff wall. In addition, it provides a method for constructing underwater structures that can reduce the cost and shorten the construction period in the construction of sheet pile foundations, such as bridge piers, by eliminating the support work inside the izutsu and the scaffolding of the upper frame form. Is to do.

[0014]

A first aspect of the present invention is a method for constructing an underwater structure comprising a sheet pile foundation and an upper body, wherein a sheet pile is cast in an underwater foundation ground to form a well.
A prefabricated upper skeleton (bridge pier, etc.) is laid down on the head of this well, and the upper opening of the well is covered by the bottom of the upper body so that the water can be stopped. Is fixed to the well head by hydraulic pressure, and then the bottom of the upper skeleton is integrated with the well head inside the well head. Integration of the bottom of the upper body with the head of the well is done by casting concrete or other methods.

According to a second aspect of the present invention, in the construction method of the first aspect, the bottom of the upper skeleton is formed to cover the head of the well, and a waterproof material is provided between the bottom of the upper skeleton and the head of the well. It is a construction method of an underwater structure characterized by being interposed. That is, the upper frame is made of prefabricated steel shell or precast concrete, etc., the lower part is provided with a lid-shaped footing that covers the head of the well, and a waterproof material is interposed between the footing and the head of the well. Let it.

According to a third aspect of the present invention, in the construction method according to the first or second aspect, when the well is closed, a predetermined position is cut and the upper part of the well is removed by removal. The construction method of the object. That is, a sheet pile, such as a steel pipe sheet pile, is cast as usual, with the upper part protruding from the water surface, and the upper part is cut and removed from a predetermined position so that the upper skeleton can be laid down.

According to a fourth aspect of the present invention, in the construction method according to the first or second aspect, a sheet pile is driven so that a well head is located at a predetermined position. Is the way. That is, the sheet pile may be driven so that the uppermost end of the sheet pile is located at the cutting position (installation position of the upper frame), and the cutting operation may be omitted.

The above upper frame is not limited to the entire structure (such as a water intake tower of a power plant), but also includes a part of the structure (such as a substructure of a bridge). In the above configuration, when the well is formed, the bottom of the upper body is footed with a footing or the like, and aerial concrete is poured into the dried bottom, and the head of the well and the upper part of the well are formed. Since the lower part of the skeleton is integrally rigidly connected, the upper part of the sheet pile does not need to be used as a temporary cutoff wall as in the past, and the sheet pile does not generate residual stress unlike the conventional case. Only the strength as a foundation needs to be considered, and the members can be optimized, for example, the size of the sheet pile can be reduced.

Further, since the pre-fabricated upper frame can be easily and rigidly connected to the head of the well base, the conventional support work is not required. Further, it is not necessary to secure a work space for constructing the upper skeleton in the well, and the well base can be made to have a structurally necessary size.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. This embodiment is an example in which the present invention is applied to a steel pipe sheet pile foundation of a pier constructed underwater. FIG. 1 shows an example of the construction method of the present invention in the order of steps.

As shown in FIG. 1, a pier 11 as an upper skeleton used in the present invention includes a footing 11a and a skeleton leg 1a.
1b and a bridge seat portion 11c. These are formed of a prefabricated steel shell 12, and concrete 13 is cast into the sunk steel shell 12, whereby the pier 11 having a composite structure of a steel plate and concrete is constructed. .

The footing 11a has a flat plate portion 14 slightly larger than the plane shape of the steel sheet pile foundation (well cylinder) 10.
And a skirt portion 15 integrally hanging down from an outer edge of the flat plate portion 14, and has a shape capable of completely covering the head of the well 10 of the steel pipe sheet pile. Further, the flat plate portion 1
On the lower surface of the steel pipe sheet pile, a water-stopping material 16 made of rubber or the like abutting on the top end of the well 10 of the steel pipe sheet pile is provided continuously in the circumferential direction so that water does not enter the footing. To

The water-stopping material 16 is not limited to the illustrated example, but may be provided on the inner surface of the skirt portion 15 or the like, and the water-stopping material may function as a guide material, a cushioning material, or a positioning material. In addition, the skirt portion 15 is made longer to make the foundation ground A
It may be made to be able to penetrate into the inside, and the water stopping performance may be improved. Further, the pier 11 is not limited to the prefabricated steel shell 12, but may be precast concrete or a composite structure thereof.

In the above configuration, construction is performed in the following procedure. (1) In the same manner as the conventional method, a work table and a guide are installed (not shown), and a steel pipe sheet pile 1 is driven. A well 10 having a closed cross section such as a circle is formed by the steel pipe sheet pile 1 on the outer periphery. A bulkhead steel pipe sheet pile and a single-story pile are driven into the inside of the well 10 as necessary (not shown). Next, a waterproofing operation of the joint of the outer steel pipe sheet pile 1 and a concrete filling work of the outer steel pipe sheet pile 1 are performed. This waterproofing / filling concrete work is performed below the cutting position in the next step.

(2) An underwater cutting machine is inserted into the outer steel pipe sheet pile 1 to cut a predetermined position of the outer steel pipe sheet pile 1, and the upper portion of the cut outer steel pipe sheet pile 1 is pulled out. Here, this disconnection
It is necessary to perform the operation with high accuracy so that the top level of each peripheral steel pipe sheet pile 1 matches. As a result, the well 10
Is formed. In the present invention, since the upper part of the outer steel pipe sheet pile 1 is not used as a temporary cutoff wall, the outer steel pipe sheet pile 1 is not used.
The cutting work can be omitted by driving the upper end to the cutting position.

(3) The steel shell 12 of the pier 11 towed by a hoist ship or the like is laid on the well 10 of the steel pipe sheet pile. The footing 11a covers the head of the well 10 made of steel sheet piles,
This seals the head of the well 10 of the steel pipe sheet pile. From this state, the water in the steel shell 12 is discharged and dried up. The footing 11a is integrated with the head of the well 10 of the steel pipe sheet pile by water pressure, and complete water blocking is performed. Furthermore, in the next step of placing concrete, in order to improve the workability of the worker, the internal water in the foundation ground A in the well 10 of the steel pipe sheet pile is discharged to lower the water level.

(4) A stud bar 1 for integrating the footing is formed on the inner surface of the upper portion of the outer steel sheet pile 1 in the footing 11a.
After the 7 and the like are attached, concrete 13 is poured into the footing 11a (the head of the well 10 of the steel pipe sheet pile) in the air.
The concrete 13 is cast to a predetermined position of the skeleton leg 11b. A rib (not shown) for integration is attached in advance to the inner surface of the steel shell of the body leg 11b. As described above, the pier 11 having a composite structure of steel and concrete rigidly connected to the head of the well 10 of the steel pipe sheet pile is completed.

Although the description has been given of the case where the present invention is applied to a pier, the present invention is not limited to this, and the present invention can be applied to an underwater structure such as an underwater discharge tower of a power plant.

[0029]

Since the present invention has the above-described structure, the following effects can be obtained. (1) When the well is formed, cover the bottom of the upper body with the footing or the like of the upper body, place the submerged concrete in the dried-up bottom, and connect the head of the well and the lower part of the upper body. Since it is integrally rigidly connected, there is no need to use the upper part of the sheet pile as a temporary cut-off wall as in the past, so there is no residual stress in the sheet pile as in the past, and the Izutsu sheet pile is completed after completion. You only have to consider the strength as a foundation,
The members can be optimized, for example, the size of the sheet pile can be reduced, and the cost can be reduced.

(2) Since the prefabricated upper frame can be easily and rigidly connected to the head of the well tube base, the conventional support work is not required, and the cost and the construction period can be reduced.

(3) Further, it is not necessary to secure a work space for constructing the conventional upper frame in the well.
Izutsu foundations can be of the required size for the structure,
Cost reduction and shortening of the construction period can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a method for constructing an underwater structure according to the present invention in the order of steps.

FIG. 2 is a cross-sectional view showing a conventional method of constructing a steel pipe sheet pile foundation for a pier in the order of steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel sheet pile 2 ... Conductor frame 3 ... Well cylinder 4 ... Bottom concrete 5 ... Shoring 6 ... Connector 7 ... Top slab concrete 8 ... Body concrete 10 ... Steel pipe sheet pile well 11 ... Bridge pier 11a ... Footing 11b ... Body leg 11c ... Bridge seat 12 ... Shell 13 ... Concrete 14 ... Plate 15 ... Skirt 16 ... Water stop material 17 ... Stud streak

Claims (4)

[Claims] 1. A method for constructing an underwater structure comprising a sheet pile foundation and an upper body, wherein a sheet pile is cast into a submerged foundation ground to form a well, which is manufactured in advance on the head of the well. The upper body is submerged, the upper opening of the well is covered with the bottom of the upper body so that water can be stopped, the water level in the head of the well is lowered, and the upper body is fixed to the head of the well by water pressure. A method for constructing an underwater structure, comprising integrating a bottom portion of an upper frame with a head of a well. 2. The construction method according to claim 1, wherein the bottom of the upper skeleton is shaped to cover the head of the well, and a water blocking material is interposed between the bottom of the upper skeleton and the head of the well. Characteristic construction method of underwater structures. 3. The construction method according to claim 1, wherein when the well is closed, a predetermined position is cut, and the upper part of the well is removed by removal. . 4. The construction method according to claim 1, wherein the sheet pile is driven so that the well head is located at a predetermined position.