JP7228835B2 - Steel piles and onshore structures for supporting onshore structures - Google Patents

Description

TECHNICAL FIELD The present invention relates to the foundation structure of a structure, and more particularly to a protective structure for steel piles buried in the ground to support land structures.

A structure using piles is known as a foundation structure for supporting a structure. As materials for piles, wooden piles, stainless steel piles, aluminum piles, etc. are also used, but wooden piles are prone to rot due to water seeping inside, and stainless steel piles and aluminum piles are expensive. For this reason, steel piles such as steel pipes and shaped steel having galvanized, mortar, anti-corrosion coating, and anti-corrosion layers such as polyethylene and polyurethane on their surfaces are widely used.

Most of the structures are built on land, but some structures are built on the sea. The piles that support offshore structures are driven into the ground through a layer of seawater. Steel piles that support offshore structures are subject to severe corrosion in tidal zones, which are periodically submerged by the ebb and flow of the tide, and splash zones, where splashes of waves adhere. Therefore, a heavy anti-corrosion coating made of fiber reinforced plastic (FRP) such as glass fiber reinforced polyester or glass fiber reinforced urethane elastomer is provided on the surface of the anti-corrosion layer in the tidal zone and splash zone of the steel piles that support offshore structures. is proposed.

Patent Literature 1 proposes means for preventing separation between such a heavy anticorrosive coating and an anticorrosive layer composed of a synthetic resin layer such as polyethylene coating or polyurethane coating as an underlying layer. In order to solve a similar problem, Patent Document 2 proposes to coat the tidal zone and the splash zone of the steel pile with an anticorrosive coating made of reinforced concrete.

On the other hand, in Patent Document 3, regarding wooden piles that support lightweight structures on land, in order to prevent corrosion due to permeation of rainwater, etc., the pile head of the wooden pile is covered with a steel pipe cap, and the structure is attached to the steel pipe cap. Connected and supported structures have been proposed. A steel pipe cap covers the top end of the pile and has a length of, for example, 0.8 m.

Regarding the method of burying piles while rotating them, Non-Patent Document 1 describes in detail the standard construction procedure.

JP-A-2000-15744 JP-A-2007-33269 JP 2016-41886 A

"Rotating Pile Construction Method Construction Management Guidelines" General Incorporated Association Steel Pipe Pile and Steel Sheet Pile Technical Association March 2017

As described above, in the steel pile buried in the soil through seawater, in addition to the anticorrosion layer provided over the entire length of the steel pile in the tidal zone and splash zone of the steel pile, the FRP coating layer It has been proposed to provide a partial However, in steel piles that support structures on land, that is, steel piles that are buried in the ground without passing through the water layer on the ground, a part of the surface of the steel pile in the longitudinal direction is particularly resistant to corrosion. No attempt has been made to provide an elevated coating layer.

Steel piles that support onshore structures do not have areas where corrosion can progress significantly, such as tidal zones and splash zones. was not

In addition, if a coating layer with a certain thickness such as an FRP coating layer is partially provided in the place where the steel pile is buried in the ground, the partially provided coating layer, especially near the lower edge, when the pile is buried There is a risk of damage or separation due to friction with earth and sand, and this has also been an obstacle to partially providing a thick coating layer on the part of the steel pile that is buried in the soil.

However, in recent years, the problem of aging land structures that have been built for decades has been highlighted . There is an increasing demand for a foundation structure with excellent workability.

This invention has been made to provide a technique to meet such a demand, and to obtain a better protective structure for steel piles buried in the ground to support structures provided on land. It was made for the purpose.

The steel piles 2 (2a to 2d) of the present invention that solve the above problems are buried or buried in the ground to support the land structures 1 (1a, 1b, 1d), The ground surface area 3 of a predetermined vertical dimension of the position 3a penetrating the ground surface GL of the steel pile after being buried in the soil is a coating layer 4 including the FRP layer 4b, preferably the FRP layer 4b and the weather resistance covering the surface thereof. It is characterized by being coated with a coating layer 4 including a topcoat layer 4c made of a durable paint, an abrasion-resistant paint, or a friction-reducing paint.

A pile having a coating layer on its surface has a problem that the coating layer is scraped off by friction abrasion with earth and sand during burial. In particular, when the rotating pile construction method is adopted to avoid noise and vibration during burial, the frictional distance with earth and sand increases due to rotation, and wear and peeling of the coating layer become a problem. The present inventors have confirmed through tests that this problem can be solved by providing a topcoat layer 4c that has excellent weather resistance and wear resistance or reduces friction on the surface of the FRP layer 4b.

In addition, the land structure 1 of the present invention includes steel piles 2 buried in the ground to support the land structure, and a ground surface area having a predetermined vertical dimension of the portion where the steel pile penetrates the ground surface GL. 3 is coated with a coating layer 4 including an FRP layer 4b, preferably a coating layer 4 including a topcoat layer 4c made of a weather resistant paint, an abrasion resistant paint or a friction reducing paint covering the surface of the FRP layer 4b. It is characterized by

In general, the ground surface region 3 does not reach the upper end of the steel pile 2, and a pile head region 5 having no FRP coating layer exists between the upper end of the steel pile 2 and the ground surface region 3. are doing. In addition, the FRP layer 4b and the topcoat layer 4c were constructed after the steel piles 2 were buried until the lower edge of the ground surface area 3 was positioned slightly above the ground surface GL, and these layers 4b and 4c were hardened. Further, it is preferable to bury them to a depth such that a substantially intermediate position 3a of the ground surface area 3 including these layers is positioned on the ground surface GL. This is because if it is applied at a factory or before burying at the site, it becomes difficult to deal with when the pile stops at a high level, that is, when the pile is not buried to the planned depth.

An object of the present invention is to further improve the durability of steel piles over several decades. Therefore, at present, its effect cannot be sufficiently proved and confirmed. However, the state of earth and sand on the ground surface is diverse, and it is thought that there are multiple types of means for ensuring long-term durability.

It is clear that the structure of the present invention is particularly effective in the ground where the corrosion of steel materials on the ground surface is severe.In addition, according to the tests of the present inventors, even in burial by the rotary pile construction method in which the friction distance is long An actual burying test confirmed that the FRP layer did not separate when the pile was buried to a depth of about 1m from the ground surface.

That is, the present invention does not cause the problem of peeling of the coating layer at the time of burying the pile, which has been a concern in the past. It has the effect of improving sexuality.

FIG. 1 is a block diagram showing a first example of a construction procedure for steel piles according to the present invention; Partially enlarged cross-sectional view of the lower edge portion of the coating layer Block diagram showing a second example of the construction procedure of the steel pile of the present invention Block diagram showing the third example of the construction procedure of the steel pile of the present invention The front view which shows the 1st example of the land structure supported with the steel pile of this invention. Section A cross-sectional view of FIG. The side view which shows the 2nd example of the land structure supported by the steel pile of this invention. A partial perspective view showing a third example of a land structure supported by steel piles of the present invention.

Embodiments of the present invention will be described below with reference to the drawings showing examples. A steel pile 2 whose entire surface has been subjected to appropriate anti-corrosion treatment by a conventional method is driven until its tip comes into contact with a predetermined support layer SL (Fig. 1a), and a predetermined top and bottom of the ground surface area 3 as a high coverage area is driven. It is pulled up by half of the dimension L and the margin necessary for the work is taken into consideration (Fig. 1b). Then, sandblasting, shot blasting, dix sander, or the like is applied to the ground surface region 3, which has a position 3a that was located on the ground surface when the support layer SL was previously driven, as an intermediate position, so that the oxide film on the steel pile surface is formed. is removed, and a base coat is applied with a primer (Fig. 1c). Vinyl esters, for example, are used as primers.

On the other hand, a resin-impregnated mat 8 is prepared by impregnating a glass fiber mat or carbon fiber mat having a width covering the ground surface area 3 with an unsaturated polyester resin, a vinyl ester resin, or an epoxy resin (Fig. 1d), and a cured primer layer 4a. The resin-impregnated mat 8 is wrapped around and shaped, and then cured to form an FRP layer 4b, and a top coating agent is applied to the surface and the upper and lower edges of the FRP layer 4b to form the coating layer 4 (Fig. 1e). ).

As the top coat agent, in addition to weather resistant paints such as acrylic lacquer, unsaturated polyester resins (iso-based) and acrylic gel coat resins can be used. Furthermore, if necessary, an ultraviolet curable sheet or a coating agent (for example, a registered trademark Friction Cutter) that reduces friction by forming a water-containing gel on the boundary surface with earth and sand can be used.

After the FRP layer 4b and the topcoat layer 4c are completely hardened, the piles 2 are driven in to a depth where the tips of the piles 2 come into contact with the support layer SL (FIG. 1f). As a result, the mid-height position 3a of the ground surface area 3 provided with the covering layer 4 becomes the position of the ground surface GL. As a method of burying the pile 2, it is preferable to employ a rotary method using a steel pipe pile.

In the example of FIG. 1, the pile 2 is once driven to a desired depth and then pulled up to form the covering layer 4, but the surrounding of the pile 2 can also be excavated to form the covering layer 4. FIG. That is, as shown in FIG. 3, before or after driving the pile 2, the periphery of the pile 2 driven to a desired depth is excavated (FIGS. 3a and 3b). Then, the ground surface area 3 is set to form the covering layer 4 (FIGS. 3c to 3e), and after the FRP layer 4b and the topcoat layer 4c are completely hardened, the excavated hole is backfilled (FIG. 3f). In addition, if the location where the foundation piles are provided is the location where the embankment is to be built, the piles 2 are driven in before the embankment, the covering layer 4 is formed so that the upper surface of the embankment is located within the ground surface area 3, and then the embankment. It can also be constructed by the method of

FIG. 4 is a diagram showing a construction procedure when the embedding depth of the steel pile 2 is known by preliminary investigation such as driving test piles. After driving the steel pile 2, which has been subjected to appropriate anticorrosion treatment to the entire surface length by a conventional method, to a slightly shallow depth determined by the vertical dimension L of the ground surface area 3 formed from a predetermined burial depth (Fig. 4a), A covering layer 4 is formed in the ground surface area 3 having a predetermined vertical dimension, with the position of the ground surface GL being the middle position when the ground surface is driven to the burial depth of , in the same procedure as described above (FIGS. 4b and 4c). After hardening, the steel pile 2 is driven to a predetermined depth.

FIG. 2 shows a cross section of the lower edge of the coating layer 4 formed as described above, in which the FRP layer 4b is formed on the surface of the primer layer 4a, and the topcoat layer 4c is formed on the surface of the FRP layer 4b. It is The thickness of the coating layer 4 consisting of these three layers is appropriately about 2 mm in consideration of workability, etc., and the preferable range is 1.5 to 10 mm, more preferably 1.8 mm or more. 1.3 times or less. The coating layer 4 is formed only on a part of the steel pile 2 in the longitudinal direction, and the lower edge 4d and the upper edge thereof have oblique steps corresponding to the film thicknesses of the FRP layer 4b and the topcoat layer 4c. It is formed. In addition, the code|symbol 6 of FIG. 2 is the anti-corrosion layer apply|coated to the full length of the steel pile.

Generally, the ground surface area 3 does not reach the upper ends of the steel piles 2, although it depends on the structure of the supporting structure. That is, there is a pile head region 5 not coated with FRP above the ground surface region 3, and in the pile head region 5, the land structure 1 made of concrete or steel or its support base 13, 14, 15 ( 5 to 7) are adhered or fixed.

The inventors of the present application used a steel pipe pile made of STK400 with a diameter of 267.4 mm and a thickness of 8 mm and a steel pipe pile with a diameter of 216.3 mm and a thickness of 8.2 mm. Primer coating, formation of FRP layer and application of weather resistant paint are performed in the above procedure on the ground surface area 3 250 mm above and below the center, and after these are hardened, the middle position of the ground surface area 3 1 m from the top of the pile After the pile 2 was driven in until 3a became the ground surface GL, the pile was pulled out and the portion of the FRP coating layer buried in the soil was observed.

As a result, in some of the specimens, damage to the coating film of the weather-resistant paint was observed, but neither peeling nor damage to the FRP layer was observed. The thickness of the FRP coating layer was a reference value of 2 mm or more over the entire circumference, and no pinholes were observed.

The primer used in the test was an unsaturated polyester resin, the curing agent for the glass fiber was methyl ethyl ketone peroxide, and the weather resistant paint was acrylic lacquer.

5 to 8 are diagrams showing examples of land structures supported by the steel piles 2 driven as described above, and FIGS. 5 and 6 are examples of promenades provided on the slope LGL. , FIG. 7 is an example of an elevated railroad vehicle depot, and FIG. 8 is an example of supporting a pillar 1d of a land structure.

A promenade base 1a extending in the direction perpendicular to the plane of FIG. 5 is supported by supports 11 arranged at predetermined intervals in the longitudinal direction and a plurality of arms 12 fixed to the upper ends of the supports. The lower end of the column 11 is supported by a support base 13 as shown in FIG. 6, and the support base 13 is supported by a steel pile 2 composed of four steel pipes embedded in the soil slope LGL. Each steel pile 2 has a covering layer 4 including an FRP layer 4b formed on the ground surface region of a predetermined length above and below with a position penetrating the slope LGL as an intermediate position.

FIG. 7 is a view showing part of an elevated depot supported by steel piles of the present invention. The base 1b of the depot is supported by H-shaped steels 14 and 15 assembled in parallel grids in a plan view. 2a to 2c are arranged. A wall 16 and an embankment 17 surrounding the installation ground are provided outside the steel piles 2a located on the periphery of the base 1b of the depot. There is no embankment in the area other than the periphery.

FIG. 7 shows three steel piles 2a to 2c, and the steel pile 2c in the portion where the embankment 17 is not provided is a covering layer on a ground surface area of a predetermined size centered approximately on the ground surface GL. 4 is provided, and the steel piles 2a and 2b embedded in the portion where the embankment 17 is provided are provided with a coating layer 4 in the ground surface area from below the ground surface GL to above the surface of the embankment 17. there is

The ground surface region in the steel pile protection structure of the present invention may not be the surface of the pile itself, and may be surfaces substantially corresponding to the surface of the steel pile above and below the position where the pile penetrates the ground surface. good.

FIG. 8 shows the upper end of a steel pile 2d composed of two steel underground piles 21, 21 buried in the ground, a steel formwork 22, and reinforced concrete 23 in the formwork, and a land structure. It is the figure which showed the example which adhered the lower end of 1d of support|pillars which support a roof by the reinforced concrete 23 in the steel formwork 22. FIG. In this example, a steel formwork 22 penetrates the ground surface GL. The surface of the steel formwork 22 is the ground surface area 3 .

In the case of FIG. 8, the ground around the upper ends of the underground piles 21, 21 driven in advance to the original installation depth is excavated, a formwork 22 having an FRP coating on the outer surface is installed, and the lower end of the column 1d is installed. After inserting it into the formwork 22 and temporarily fixing it, concrete is poured into the formwork 22 and soil is backfilled around the formwork 22 to complete the foundation.

1 (1a, 1b, 1d) land structure 2 (2a to 2d) steel pile 3 ground surface area 3a intermediate position 4 coating layer 4b FRP layer 4c top coat layer 5 pile head area GL ground surface

Claims (7)

A steel pile for supporting a structure, comprising a fiber-reinforced plastic layer and a surface of the fiber-reinforced plastic layer and its upper and lower edges in the ground surface area of a predetermined length above and below the position where the ground surface of the steel pile is located. A steel pile provided with a covering layer, including a weather-resistant, wear-resistant or friction-reducing topcoat layer, in the covering area . The steel pile according to claim 1, wherein the top coat layer is formed of an acrylic lacquer, an isounsaturated polyester resin, an acrylic gel coat resin, an ultraviolet curable sheet, or a coating agent that produces a hydrous gel to reduce friction. . 3. The steel pile according to claim 1, wherein the lower part of said coating layer is buried in the ground by a rotary pile construction method. The steel pile according to claim 1, 2 or 3, wherein the ground surface area is an area that does not reach the upper end of the pile. A land structure supported in whole or in part by steel piles buried in the ground, wherein said steel pile is the steel pile according to claim 1, 2, 3 or 4. After the steel pile is driven to a depth shallower than the predetermined burial depth, it is driven to the predetermined burial depth. A fiber reinforced plaster is placed on the ground surface area with a predetermined vertical dimension, with the position that becomes the ground surface when the ground is in the middle position. Wear-resistant coatings on the plastic layer, the surface of the fiber-reinforced plastic layer, and the areas covering the upper and lower edges A topcoat layer formed by applying a topcoat agent consisting of a flexible paint or a friction-reducing paint After forming a coating layer containing The land structure according to claim 5, wherein: After the steel pile has been driven in to a predetermined burial depth, the surrounding area of the pile is excavated to remove the ground surface. A fiber-reinforced plastic layer and the fiber Abrasion-resistant paint or friction-reducing paint is applied to the surface of the reinforcing plastic layer and the area covering its upper and lower edges. Form a coating layer containing a top coat layer formed by applying a top coat agent comprising 6. The steel pile according to claim 5, which is installed by backfilling the excavated hole after the coating layer has hardened. land structure.

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