Steel pipe piles and hybrid piles

Abstract

To provide a steel pipe pile that is particularly inexpensive in processing cost and can exhibit high bending strength despite being thin, and to provide a hybrid pile that has strong integrity as a composite structure and can exhibit high bearing capacity performance.SOLUTION: A steel pipe pile 10 comprises a steel pipe main body 11 with a wall thickness of less than 2.0 mm, and a plurality of anchor grooves 12 provided on an outer periphery of the steel pipe main body 11. The anchor groove 12 is an elongated groove having a longitudinal direction along a longitudinal direction of the steel pipe main body 11 and a width direction along a circumferential direction of the steel pipe main body 11. There is formed a valley line 12a which is sandwiched between two surfaces bent in the width direction and which extends in the longitudinal direction, in a groove bottom of the anchor groove 12. A hybrid pile 1 comprises: a substantially cylindrical improved body 20 formed from the ground surface so as to extend underground; and the steel pipe pile 10 arranged at the center of the improved body 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a steel pipe pile and a hybrid pile, and in particular to a steel pipe pile which has low processing costs, is thin-walled and yet can exhibit high bending strength, and a hybrid pile which has strong integrity as a composite structure and can exhibit high bearing capacity. [Background technology]

[0002] When constructing a building on ground that does not have sufficient bearing capacity, a pile-type ground reinforcement method is used to reinforce and support the ground below the building with piles. A known method of pile-type ground reinforcement is the hybrid pile, which is made by inserting a core material into the center of a cylindrical soil cement improvement body constructed underground. As a core material for hybrid piles, Patent Document 1 discloses a nodular steel pipe pile with tubular metal fittings attached at predetermined intervals on the periphery, while Patent Document 2 discloses a steel pipe pile with multiple depressions on the periphery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-172850 A [Patent Document 2] JP 2015-148246 A Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional techniques have the following problems. <1> The steel pipe pile in Patent Document 1 requires welding a metal tube to the outer periphery of the steel pipe pile, which requires a lot of work and increases manufacturing costs. In addition, when the hybrid pile is subjected to horizontal force, stress is concentrated at the corners of the metal tube inside the soil cement improved body, which may cause cracks inside the soil cement improved body. <2> In the steel pipe pile of Patent Document 2, a depression is created by clamping and pressing the steel pipe pile with steel pipe shaping rollers during the manufacturing process. However, because the steel pipe pile is thick and the cylindrical body is clamped with rollers, the depression is shallow and gentle, and the adhesion effect with the soil cement improvement body is small. <3> In both cases, the adhesion of the steel pipe pile to the soil cement improved body is insufficient, so the steel pipe pile and the soil cement improved body function separately and the bearing capacity performance expected of the composite structure cannot be fully demonstrated.

[0005] An object of the present invention is to provide a steel pipe pile and a hybrid pile that can solve the above-mentioned problems. [Means for solving the problem]

[0006] The steel pipe pile of the present invention comprises a steel pipe body having a thickness of less than 2.0 mm, and a plurality of anchoring grooves provided on the outer periphery of the steel pipe body, wherein the anchoring grooves are long grooves having a longitudinal direction along the longitudinal direction of the steel pipe body and a width direction along the circumferential direction of the steel pipe body, and are characterized in that at the bottom of the anchoring groove, it is sandwiched between two surfaces bent in the width direction, forming a valley line extending in the longitudinal direction.

[0007] The steel pipe pile of the present invention may have a plurality of anchorage grooves arranged at equal intervals along the circumferential direction of the steel pipe body to form a row of anchorage groove groups, and the anchorage groove groups may be arranged in multiple rows in the longitudinal direction of the steel pipe body.

[0008] In the steel pipe pile of the present invention, in multiple anchorage groove groups adjacent to each other in the longitudinal direction of the steel pipe body, the positions of the multiple anchorage grooves in one anchorage groove group in the circumferential direction of the steel pipe body may be different from the positions of the multiple anchorage grooves in another anchorage groove group in the circumferential direction of the steel pipe body.

[0009] The steel pipe pile of the present invention may have a plurality of anchorage groove groups adjacent in the longitudinal direction of the steel pipe body, wherein a portion of an anchorage groove of one anchorage groove group is adjacent to a portion of an anchorage groove of another anchorage groove group in the circumferential direction of the steel pipe body.

[0010] In the steel pipe pile of the present invention, the bottom of the anchorage groove may be exposed on the end face at least at one end of the steel pipe body.

[0011] The hybrid pile of the present invention is characterized by comprising an approximately cylindrical improvement body formed from the ground surface to underground, and a steel pipe pile placed in the center of the improvement body. Effect of the Invention

[0012] Since the hybrid pile of the present invention has the above-mentioned configuration, it has at least one of the following effects. <1> The deep valley line at the bottom of the anchorage groove allows the hardened improvement body to grip the steel pipe pile from the outside like a claw, giving the steel pipe pile extremely strong adhesion to the improvement body. This provides high integrity as a composite structure and allows it to demonstrate high bearing capacity. <2> Because the bearing capacity is so high, it is possible to apply steel pipe piles with smaller diameters than conventional technology for the same bearing capacity requirements, for example by scaling down from φ60.5mm to φ48.6mm, which reduces construction costs compared to conventional methods.

[0013] Since the steel pipe pile of the present invention has the above-mentioned configuration, it has at least one of the following effects. <1> Multiple fixing grooves with deep valley lines are formed along the longitudinal direction, so the material is thin yet capable of exhibiting high bending strength. <2> Because the wall thickness is thin, it is possible to manufacture the pipe by pressing a fixing groove into the steel strip, forming it into a tube, and forge welding it (forge-welded steel pipe). Therefore, the processing cost is lower than the conventional technology of creating irregularities on the surface of a formed steel pipe by rolling. <3> The steel pipe piles are thin, making them lightweight and easy to handle. <4> The construction machine can clamp the valley line of the anchoring groove with a chuck device, so that the anchoring groove can be fixed securely. Therefore, even though the anchoring groove is thin, it can be directly inserted into the ground by rotary or vibration. <5> By engaging the joint member with the inner projection, two steel pipe piles can be connected from inside the pipe. As a result, the joint member does not protrude outside the steel pipe pile, making it easier to handle the steel pipe pile. [Brief description of the drawings]

[0014] [Figure 1] Explanatory diagram of the hybrid pile of the present invention [Diagram 2] Diagram of steel pipe pile [Diagram 3] Illustrative diagram of the arrangement of fixing grooves [Figure 4] Diagram of joint structure of steel pipe pile [Diagram 5] Cross-sectional view of Example 2 [Figure 6] FIG. 3 is an explanatory diagram of the third embodiment. [Figure 7] FIG. 3 is an explanatory diagram of the third embodiment. [Figure 8] FIG. 3 is an explanatory diagram of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the steel pipe pile and hybrid pile of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0016] [Hybrid pile] <1> Overall configuration (Figure 1) The hybrid pile 1 is a composite pile that is installed under the foundation of a building. The hybrid pile 1 comprises at least a cylindrical improvement body 20 formed from the ground surface to underground, and a steel pipe pile 10 arranged in the center of the improvement body 20. One of the features of the hybrid pile 1 of the present invention is that the steel pipe pile 10 and the improvement body 20 are integrated by multiple anchorage grooves 12 with valley lines 12a, thereby enabling the composite structure to exhibit high bearing capacity.

[0017] <2> Steel pipe pile (Figure 2) The steel pipe pile 10 is a component that mainly exerts bending strength, shear strength, and tensile strength in the hybrid pile 1. The steel pipe pile 10 comprises at least a steel pipe body 11 having a wall thickness of less than 2.0 mm, and a plurality of fixing grooves 12 provided on the outer periphery of the steel pipe body 11. The fixing groove 12 is formed by pressing the steel strip of the steel pipe body 11, so that an inner surface protrusion 13 is formed on the inside of the fixing groove 12 in the steel pipe body 11. In this example, a forge-welded steel pipe having an outer diameter of φ48.6 mm, a length of 4,000 mm, and a wall thickness of 1.8 mm is used as the steel pipe body 11. There are no limitations on the outer diameter or length of the steel pipe body 11, but it is desirable that the outer diameter be approximately φ318.5 mm or less.

[0018] <2.1> Fixing groove (Fig. 2) The fixing groove 12 is a groove for increasing the adhesion between the steel pipe body 11 and the improvement body 20. The fixing groove 12 has an elongated shape having a longitudinal direction along the longitudinal direction of the steel pipe body 11 and a width direction along the circumferential direction of the steel pipe body 11. At the bottom of the fixing groove 12, a valley line 12a is formed which is sandwiched between two surfaces bent in the width direction and extends in the longitudinal direction. In the conventional steel pipe piles, the depressions were formed in the thick steel pipes by rolling, so it was not possible to form a clear valley line at the bottom of the depression. In contrast, in the present invention, by designing the wall thickness of the steel pipe body 11 to be extremely thin, less than 2.0 mm, the surface of the steel pipe body 11 can be bent inward at a steep angle to form a deep linear valley line 12a at the bottom of the fixing groove 12. This strengthens the adhesion between the steel pipe pile 10 and the improvement body 20, making it possible to construct a hybrid pile 1 that can exert high bearing capacity as a composite structure.

[0019] <2.1.1> Arrangement of fixing grooves (Fig. 3) The fixing grooves 12 can be provided in any arrangement on the outer periphery of the steel pipe body 11 . In this example, a plurality of fixing grooves 12 are arranged on the outer circumferential surface of a steel pipe body 11 in a so-called staggered pattern. In detail, a plurality of fixing grooves 12 are provided at equal intervals in the circumferential direction at the same height in the longitudinal direction of the steel pipe body 11 to form a fixing groove group 12'. In this example, one fixing groove group 12' is formed by two fixing grooves 12 each spaced 180° apart. In adjacent fixing groove groups 12' above and below (in the longitudinal direction) of the steel pipe body 11, the positions of the fixing grooves 12 in one fixing groove group 12' are shifted by 90° from the positions of the fixing grooves 12 in the other fixing groove group 12'. By arranging the anchoring grooves 12 in a staggered pattern on the outer periphery of the steel pipe body 11, the interval between the anchoring grooves 12 in the circumferential direction of the steel pipe body 11 is half that of a normal arrangement, making it possible for the improvement bodies 20 in the anchoring grooves 12 to surround and hold the steel pipe pile 10 from more directions. This further improves the unity between the steel pipe pile 10 and the improvement bodies 20.

[0020] <2.2> Inner protrusion (Fig. 3) The inner surface protrusion 13 is a convex portion that protrudes toward the inside of the steel pipe body 11 . The inner surface protrusion 13 has a ridge line extending along the longitudinal direction of the steel pipe body 11 . When extending the length of the steel pipe pile 10, two steel pipe piles 10 can be easily and securely connected by installing the joint member J inside the steel pipe body 11 and engaging it with the inner protrusion 13 (Figure 4). As a result, in the connection structure of the steel pipe pile 10, the joint member J does not protrude outside the steel pipe body 11, making the steel pipe pile 10 easier to handle.

[0021] <3> Improved body The improved body 20 is a structure that mainly exerts peripheral friction force and tip support force underground. The improved body 20 is formed by a deep mixing treatment method. In this example, the improvement body 20 is a roughly cylindrical soil cement improvement body having an outer diameter of φ300 mm and a length of 4,700 mm. The soil cement improved body is constructed from the ground surface to the ground using a construction machine A equipped with an agitator. In detail, the original ground is rotary excavated by the agitator while the cement-based solidification material is discharged into the ground, and this is mixed and stirred with the excavated soil to construct the soil cement improved body. The soil cement improved body has a larger outer diameter than the steel pipe pile 10, and therefore comes into contact with the surrounding soil over a larger surface area, enabling it to exert a high peripheral friction force.

[0022] <4> Integration of steel pipe piles and improvement body One of the features of the hybrid pile 1 of the present invention is the high integrity between the steel pipe pile 10 and the improvement body 20. When the steel pipe pile 10 is inserted into the center of the improvement body 20, the unhardened improvement body 20 penetrates into the deep valley line 12a at the bottom of the anchorage trench 12. After insertion, when the improvement body 20 hardens, the valley line 12a of the fixing groove 12 causes the tip of the improvement body 20 to grip the steel pipe pile 10 from the outer periphery like claws. In particular, in this example, the anchorage grooves 12 are arranged in a staggered pattern, so that the improvement bodies 20 in the anchorage grooves 12 surround and grip the pile from many directions. This results in a very strong adhesion between the steel pipe pile 10 and the improvement bodies 20, and the integrity of the hybrid pile 1 is high. With the above-described structure, the hybrid pile 1 of the present invention is able to exhibit high bearing capacity as a composite structure by firmly integrating the steel pipe pile 10 with its high horizontal strength against bending, shear, and tension, and the improvement body 20 with its high peripheral friction force and tip bearing capacity. EXAMPLES

[0023] [Example of a wrap section] In this example, lap portions R are provided in adjacent fixing groove groups 12' on the top and bottom of the steel pipe body 11 (FIG. 5). In this example, at the same height in the longitudinal direction of the steel pipe body 11, one fixing groove group 12' is formed by four fixing grooves 12 each at 90°, and these are arranged in a staggered pattern. In adjacent anchoring groove groups 12' above and below the steel pipe body 11, the upper (lower) part of the anchoring groove 12 of the lower (upper) anchoring groove group 12' partially overlaps with the lower (upper) part of the anchoring groove 12 of the upper (lower) anchoring groove group 12' in the circumferential direction of the steel pipe body 11. In this example, by providing the lap portion R in the anchoring groove group 12', there is no portion along the longitudinal direction of the steel pipe body 11 where the anchoring groove 12 does not extend. This increases the structural strength of the steel pipe body 11, allowing it to exhibit high bending strength despite its thin wall. EXAMPLES

[0024] [Example of using a steel pipe pile alone] In Example 1, the steel pipe pile 10 is used as a hybrid pile 1 in combination with the improvement body 20, but this is not limited to the above, and the steel pipe pile 10 can also be used alone. In this example, an engagement end 14 is formed at one end of the steel pipe body 11, where the bottom of the fixing groove 12 appears on the end surface. In detail, the engagement end 14 is formed by cutting one end of the steel pipe body 11 at the height where the fixing groove 12 extends. In the construction machine A, a plurality of engaging projections A2 corresponding to the positions of the engaging ends 14 are provided on the inner surface of the casing A1. The steel pipe pile 10 is inserted into the casing A1 and the engaging projection A2 is inserted into the groove of the engaging end 14, thereby restraining the steel pipe pile 10 in the circumferential direction within the casing A1 (FIG. 6). This allows the construction machine A to be used to rotate and drive the steel pipe pile 10 into the ground (Figure 7). If an engagement end 14 is provided at the tip of the steel pipe body 11 in addition to the head of the steel pipe body 11, the engagement end 14 functions as a bit (tooth) of the steel pipe pile 10, making it easier to drive the pile into the ground. In this example, for example, a steel pipe pile 10 having an outer diameter of φ48.6 mm is applied to the small diameter steel pipe pile construction method, and using construction machine A, multiple steel pipe piles 10 are driven at equal intervals into the ground below the designed building foundation, so that the load of the building can be distributed and supported by the ground and the steel pipe piles 10 (Figure 8). [Explanation of symbols]

[0025] 1 Hybrid pile 10 Steel pipe pile 11 Steel pipe body 12 Fixing groove 12' Settlement Groove Group 12a valley line 13 Inner projection 14 Engagement end 20 Improved body A Construction machine A1 Casing A2 Engagement protrusion J Joint material R Wrap

Claims

1. A steel pipe body having a wall thickness of 1.8 mm or less and 0.6 mm or more; A plurality of fixing grooves provided on the outer periphery of the steel pipe body, The fixing groove is a long groove having a longitudinal direction along the longitudinal direction of the steel pipe body and a width direction along the circumferential direction of the steel pipe body, a groove bottom of the fixing groove is sandwiched between two surfaces bent in the width direction and has a valley line extending in the longitudinal direction. Steel pipe pile.

2. The steel pipe pile according to claim 1, characterized in that the multiple anchorage grooves are arranged at equal intervals along the circumferential direction of the steel pipe body to form a row of anchorage groove groups, and the anchorage groove groups are arranged in multiple rows in the longitudinal direction of the steel pipe body.

3. A steel pipe pile as described in claim 2, characterized in that, in multiple groups of anchoring grooves adjacent to each other in the longitudinal direction of the steel pipe body, the positions of the multiple anchoring grooves in one group in the circumferential direction of the steel pipe body are different from the positions of the multiple anchoring grooves in another group in the circumferential direction of the steel pipe body.

4. A steel pipe pile as described in claim 3, characterized in that in multiple anchorage groove groups adjacent to each other in the longitudinal direction of the steel pipe body, a portion of an anchorage groove of one of the anchorage groove groups is adjacent to a portion of an anchorage groove of another of the anchorage groove groups in the circumferential direction of the steel pipe body.

5. A steel pipe pile as described in claim 1, characterized in that the steel pipe body is provided with an inner surface protrusion that protrudes toward the inside of the steel pipe body on the back side of the fixing groove, and the inner surface protrusion has a ridge extending along the longitudinal direction of the steel pipe body.

6. A substantially cylindrical improvement body formed from the ground surface to underground; The steel pipe pile according to any one of claims 1 to 5, which is arranged in the center of the improved body, Hybrid pile.

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