Caisson type pile foundation, and construction method of caisson type pile foundation

Abstract

To eliminate overcrowding bar arrangement at pile heads and the like in an underground structure having an earth retaining structure using liner plates.SOLUTION: A caisson type pile foundation comprises: liner plates arranged in a depth direction and a circumferential direction along a wall surface of a shaft formed by excavating the ground and having a main body, an axial flange extending in the depth direction, and a circumferential flange extending in the circumferential direction; an outer solidification material filled between the liner plate and the wall surface of the shaft; and an inner solidification material filled inside the liner plate. The liner plates include a first liner plate arranged at a top of the caisson type pile foundation with circumferential connecting positions aligned between a plurality of depth-wise stages, and a second liner plate arranged at a bottom of the caisson type pile foundation with circumferential connecting positions offset between a plurality of depth-wise stages.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a caisson foundation and a method for constructing a caisson foundation. [Background technology]

[0002] A deep foundation is generally constructed by excavating the ground and repeating the process of connecting the left and right and top and bottom edges of a liner plate to a predetermined depth, constructing an earth retaining wall inside the shaft, erecting reinforcing bars inside the wall, and then pouring concrete. An example of prior art related to such a deep foundation is described in Patent Document 1.

[0003] In the technology described in Patent Document 1, a space holder is fixed to a liner plate, a hoop is placed on a bracket attached to the space holder via a guide bar, the intersection of the bracket and the hoop is tied tightly with wire, and then the main reinforcing bars are placed inside the hoop, and the intersection of the main reinforcing bars and the hoop is tied tightly with wire, thereby completing the process of placing reinforcing bars in a deep foundation before pouring concrete. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Utility Model Registration No. 3158383 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology described in Patent Document 1 requires components such as space holders, guide bars, and brackets to install the reinforcing bars, which not only increases the cost of the components but also poses the problem that if the cross-sectional force acting on the pile head during an earthquake or other event is large, the reinforcing bars may be placed too densely, making design and construction difficult.

[0006] Therefore, the present invention aims to provide a deep foundation foundation and a construction method for a deep foundation foundation that has a retaining structure using liner plates, which reduces cost increases and enables the elimination of over-dense reinforcement at pile heads, etc. [Means for solving the problem]

[0007] [1] A deep foundation comprising: liner plates arranged in the depth direction and circumferential direction along the wall surface of a shaft formed by excavating the ground, the liner plates having a main body, an axial flange extending in the depth direction, and a circumferential flange extending in the circumferential direction; an outer solidification material filled between the liner plates and the wall surface of the shaft; and an inner solidification material filled inside the liner plates, wherein the liner plates include a first liner plate arranged at the top of the deep foundation with the circumferential connecting positions aligned between the multiple depth-wise stages, and a second liner plate arranged at the bottom of the deep foundation with the circumferential connecting positions shifted between the multiple depth-wise stages. [2] A deep foundation foundation as described in [1], wherein the thickness of the axial flange of the first liner plate is at least 1.3 mm thicker than the thickness of the main body of the first liner plate. [3] The deep foundation foundation described in [1], wherein the number of first liner plates arranged in the circumferential direction is greater than the number obtained by dividing the circumferential length by 1570 mm and rounding up. [4] The deep foundation described in [1] further comprises a connecting member interposed between the axial flanges across multiple depth-wise stages of the first liner plate. [5] A deep foundation foundation described in any one of [1] to [4], further comprising reinforcing members installed at both ends of the circumferential flange of the first liner plate. [6] The deep foundation foundation described in [5], wherein the reinforcing member includes a reinforcing plate interposed between the bolts and nuts connecting the circumferential flanges of the first liner plates adjacent in the depth direction and the circumferential flanges. [7] The deep foundation foundation described in [5], wherein the reinforcing member includes a reinforcing rib joined to the corner between the circumferential flange and the axial flange of the first liner plate. [8] The deep foundation foundation described in [5], wherein the reinforcing member includes a connecting fitting that clamps the circumferential flanges of the first liner plates adjacent in the depth direction. [9] The reinforcing member has a groove portion into which the cross-shaped intersection formed by the axial flanges and the circumferential flanges of the four first liner plates adjacent in the depth direction and the circumferential direction can be inserted. Deep foundation foundation as described in [5].

[10] The reinforcing member has a rod-shaped portion that can be inserted into the corner between each of the axial flanges and the circumferential flanges at the cross-shaped intersection formed by the axial flanges and the circumferential flanges of four of the first liner plates adjacent in the depth direction and the circumferential direction. [5] A deep foundation foundation as described in [5].

[11] A construction method for a deep foundation foundation, comprising: an excavation step of excavating the ground to form a vertical shaft; a liner plate installation step of arranging liner plates in the depth direction and circumferential direction along the wall surface of the vertical shaft; an outer filling step of filling an outer solidification material between the liner plate and the wall surface of the vertical shaft; and an inner filling step of filling an inner solidification material inside the liner plate, wherein the liner plate installation step comprises a first liner plate installation step of arranging the liner plates at the upper part of the deep foundation foundation by aligning the circumferential connecting positions between multiple depth-wise stages; and a second liner plate installation step of arranging the liner plates at the lower part of the deep foundation foundation by shifting the circumferential connecting positions between multiple depth-wise stages. [Effects of the Invention]

[0008] According to the above configuration, in the upper part of the caisson foundation, the liner plates are arranged so that the connection positions of the axial flanges are aligned between multiple depth stages, allowing the axial flanges to function as a substitute for the rebars in the depth direction, reducing the number and size of the rebars and further increasing the cross-sectional strength, making it possible to reduce the pile diameter.On the other hand, in the lower part of the caisson foundation, where the earth pressure is relatively high, the liner plates are arranged so that the connection positions of the axial flanges are staggered between multiple depth stages, preventing deformation of the retaining structure due to the liner plates. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a deep foundation according to one embodiment of the present invention. [Figure 2] 2 is a diagram showing an example of the arrangement of liner plates in the caisson foundation shown in FIG. 1. FIG. [Figure 3] 10A and 10B are diagrams showing a first example of a reinforcing member for a circumferential flange. [Figure 4] 10A and 10B are diagrams showing a second example of a reinforcing member for a circumferential flange. [Figure 5] 10A and 10B are diagrams showing a third example of a reinforcing member for a circumferential flange. [Figure 6] 10A and 10B are diagrams showing a fourth example of a reinforcing member for a circumferential flange. [Figure 7] 10A and 10B are diagrams showing a fourth example of a reinforcing member for a circumferential flange. [Figure 8] 10A and 10B are diagrams showing a fifth example of a reinforcing member for a circumferential flange. [Figure 9] 10A and 10B are diagrams showing a fifth example of a reinforcing member for a circumferential flange. [Figure 10] 10A and 10B are diagrams showing an example in which axial flanges are directly connected to each other. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] FIG. 1 is a cross-sectional view of a caisson foundation according to one embodiment of the present invention. As shown, the caisson foundation 1 includes a liner plate 4, which is installed along the wall of a shaft 3 excavated in the ground 2 to form an earth retaining structure; an inner solidification material 5 filled inside the liner plate 4; and an outer solidification material 6 filled between the liner plate 4 and the wall of the shaft 3. The inner solidification material 5 and the outer solidification material 6 are, for example, concrete or mortar. As described below, in the caisson foundation 1, the flanges of the liner plate 4 function as a substitute for rebar, so the number of rebars (not shown) embedded in the inner solidification material 5—specifically, the number of main rebars extending in the depth direction of the caisson foundation 1—is reduced.

[0012] Figure 2 shows an example of the arrangement of liner plates in the caisson foundation shown in Figure 1. A retaining structure is formed by arranging multiple liner plates 4 along the wall surface of the shaft 3 in the depth direction (z direction, also referred to as the axial direction in the figure) and circumferential direction (x direction in the figure) of the caisson foundation 1. As shown in the figure, the liner plates 4 include a first liner plate 4A arranged at the top of the caisson foundation 1 with aligned circumferential connecting positions between multiple depth stages. As described below, the liner plates 4 have axial flanges at the circumferential connecting positions. By aligning the circumferential connecting positions between multiple stages, the axial flanges can function as a substitute for reinforcing bars. Furthermore, the liner plates 4 include a second liner plate 4B arranged at the bottom of the caisson foundation 1 with staggered circumferential connecting positions between multiple depth stages. Because the lower part of the caisson foundation 1 experiences greater earth pressure than the upper part, alternating the connecting positions, which are weak points in the cross section of the retaining structure formed by the liner plates 4, between multiple stages can prevent deformation of the retaining structure. In the illustrated example, the cross-sectional shape of the retaining structure formed by the liner plate 4 is circular, but similar configurations are possible in various other shapes such as oval, elliptical, rectangular, and horseshoe.

[0013] Caisson foundations 1 are used, for example, for railway bridges and railway facilities. However, when earthquakes are examined, if the cross-sectional forces acting on the pile heads (i.e., the top of the caisson foundation 1) are large, the axial rebars can become over-dense, making design and construction difficult. In such cases, for example, by aligning the circumferential connection positions of the first liner plates 4A at the top of the caisson foundation 1 and using the axial flanges as a substitute for rebar, the number and size of the axial rebars can be reduced, eliminating the over-dense rebar arrangement. The pile head area where this arrangement is particularly effective is, for example, from the top of the caisson foundation 1 down to 1 / 3 to 1 / 2 of the total depth of the caisson foundation.

[0014] To allow the axial flange of the first liner plate 4A to function effectively as a substitute for reinforcing bars, the cross-sectional area of ​​the axial flange per liner plate may be increased by making the axial flange thicker than usual. The "Liner Plate Design and Construction Manual" (edited by the Japan Iron and Steel Federation, published by the Corrugated Liner Technology Association) specifies the thickness of each part of the liner plate in seven stages, as shown below. The thickness of a typical axial flange is one stage thicker than the main body of the liner plate. In contrast, in the present invention, the thickness of the axial flange of the first liner plate 4A may be two or more stages thicker than the main body. In this case, the thickness of the axial flange of the first liner plate 4A is at least 1.3 mm thicker than the main body.

[0015] [Table 1]

[0016] Similarly, to increase the total cross-sectional area of ​​the axial flanges of the entire cross section of the earth-retaining structure formed by the first liner plates 4A, the number of axial flanges included in the cross section of the earth-retaining structure may be increased by shortening the circumferential dimension of each first liner plate 4A. Typically, liner plates used in caisson foundations have 10 bolt holes arranged on the circumferential flanges, and the arc length per plate is 1570 mm. If these liner plates are used to adjust the circumferential length of the earth-retaining structure that is not divisible by 1570 mm with liner plates with shorter arc lengths, the number of liner plates arranged circumferentially is the number obtained by dividing the circumferential length by 1570 mm and rounding up. For the first liner plates 4A, the arc length per plate may be shorter than 1570 mm, so that the number N1 arranged circumferentially is greater than the number N2 obtained by dividing the circumferential length by 1570 mm and rounding up (N1 > N2). Preferably, N1 ≥ N2 × 1.2, and more preferably, N1 ≥ N2 × 1.5.

[0017] Although the axial flanges of adjacent first liner plates 4A in the depth direction (axial direction) of the caisson foundation 1 are not directly connected, their ends are in contact, allowing for the transmission of compressive forces. Furthermore, the circumferential flanges connected to the axial flanges at the corners of the liner plates are indirectly connected to each other by bolts, allowing for the transmission of tensile forces. However, out-of-plane deformation at both ends of the circumferential flanges connected to the axial flanges may reduce their rigidity and reduce their function as a substitute for reinforcing bars. To prevent this, reinforcing members may be installed at both ends of the circumferential flanges, as illustrated in Figures 3 to 10 below, or the axial flanges may be directly connected to each other. Note that Figures 3 to 10 illustrate the axial flanges 41, main body 42, circumferential flanges 43, bolt joints 44 between the axial flanges 41, and bolt joints 45 between the circumferential flanges 43 of the liner plate 4 that constitute the first liner plate 4A. The bolt joints 44 and 45 include bolts 441 and 451 and nuts 442 and 452, respectively.

[0018] 3 is a diagram showing a first example of a reinforcing member for a circumferential flange. In the illustrated example, the reinforcing member includes a reinforcing plate 46A interposed between each circumferential flange 43 and a bolt 451 and nut 452 that connects the circumferential flanges 43 of liner plates 4 adjacent in the depth direction (z direction in the figure). The reinforcing plate 46A reinforces the rigidity of the circumferential flange 43 near the bolt joint 45, and can prevent out-of-plane deformation of the circumferential flange 43 near the bolt joint 45 when, for example, a tensile force is transmitted via the axial flange 41.

[0019] 4 is a diagram showing a second example of a reinforcing member for the circumferential flange. In the illustrated example, the reinforcing member includes a reinforcing rib 46B joined to the corner between the circumferential flange 43 and the axial flange 41 of the liner plate 4. For example, when a tensile force is transmitted via the axial flange 41, the force is also dispersed to the reinforcing rib 46B, thereby preventing excessive stress in the circumferential flange 43. Furthermore, because the reinforcing rib 46B is a plate-shaped member perpendicular to the circumferential flange 43, the rigidity of the circumferential flange 43 near the corner is reinforced by joining the reinforcing rib 46B. These features prevent out-of-plane deformation of the circumferential flange 43 near the corner.

[0020] 5 is a diagram showing a third example of a reinforcing member for the circumferential flanges. In the illustrated example, the reinforcing member includes a connecting fitting 46C that clamps the circumferential flanges 43 of liner plates 4 that are adjacent in the depth direction (z direction in the figure). The connecting fitting 46C has a groove-shaped cross section, and the width of the inner side of the groove in the z direction is twice the plate thickness of the circumferential flanges 43 plus a small clearance. By clamping both circumferential flanges 43 with such connecting fittings 46C, it is possible to prevent out-of-plane deformation of the circumferential flanges 43 when, for example, a tensile force is transmitted via the axial flanges 41.

[0021] 6 and 7 are diagrams illustrating a fourth example of a reinforcing member for a circumferential flange. As shown in FIG. 6, the reinforcing member 47 has a base 471 and four wall portions 472 with hooked cross sections that are erected on the base 471 and form a cross-shaped groove. The width in the z direction of the inner side of the groove formed by the wall portions 472 is twice the thickness of the circumferential flange 43 plus a small clearance. As shown in FIG. 7, the cross-shaped intersection formed by the axial flanges 41 and circumferential flanges 43 of four liner plates 4 adjacent in the depth direction (z direction in the figure) and circumferential direction (x direction in the figure) is inserted into the cross-shaped groove formed by the wall portions 472 of the reinforcing member 47. This prevents out-of-plane deformation of the circumferential flanges 43 on both sides of the intersection, which could cause gaps at the intersection, for example, when a tensile force is transmitted via the axial flanges 41. Although bolts 441 and nuts 442 are omitted from FIG. 7, the reinforcing effect of base 471 and wall 472 allows bolts 441 and nuts 442 near the cross-shaped intersection to be eliminated.

[0022] 8 and 9 are diagrams illustrating a fifth example of a reinforcing member for a circumferential flange. As shown in FIG. 8, the reinforcing member 48 has a connecting portion 481 and four rod-shaped portions 482 extending from the connecting portion 481. As shown in FIG. 9, at a cross-shaped intersection formed by the axial flanges 41 and the circumferential flanges 43 of four liner plates 4 adjacent in the depth direction (z direction in the figure) and the circumferential direction (x direction in the figure), the four rod-shaped portions 482 of the reinforcing member 48 are inserted into the corners between the axial flanges 41 and the circumferential flanges 43. This prevents, for example, out-of-plane deformation of the circumferential flanges 43 on both sides of the intersection, which could cause gaps at the intersection, when a tensile force is transmitted via the axial flange 41. Note that although the bolts 441 and nuts 442 are omitted from FIG. 9, the reinforcing effect of the connecting portion 481 and the rod-shaped portions 482 allows the bolts 441 and nuts 442 near the cross-shaped intersection to be eliminated.

[0023] FIG. 10 illustrates an example of directly connecting axial flanges. In the illustrated example, connecting members 49 are interposed between axial flanges 41 across multiple stages in the depth direction (z direction in the figure) of the liner plate 4. The connecting members 49 are, for example, plate-shaped members, and have through holes formed at positions corresponding to the bolt joints 44 between the axial flanges 41. The connecting members 49 are fastened to the axial flanges 41 on both sides using bolts 441 and nuts 442. By providing the connecting members 49, the tensile force transmitted through the axial flanges 41 is transmitted directly between the multiple stages of liner plates 4 without passing through the circumferential flanges 43, thereby improving the function of the axial flanges 41 as a substitute for reinforcing bars. Note that if the tensile force increases, a gap between the bolt 441 and its through hole at the bolt joint 44 may shift, potentially reducing the function of the axial flanges 41 as a substitute for reinforcing bars. In this case, increasing the diameter of the bolt 441 or reducing the diameter of the through hole reduces the gap and prevents the performance degradation. In addition, to prevent misalignment from occurring in the gap between the bolt 441 and its through hole even when the tensile force increases, a method of increasing the tightening torque of the bolt 441 and nut 442 (such as using high-strength bolts) or a method of increasing the frictional resistance of the contact surface between the axial flange 41 and the connecting member 49 (such as blasting or phosphate treatment) may be used. [Explanation of symbols]

[0024] 1...deep foundation, 2...ground, 3...shaft, 4...liner plate, 4A...first liner plate, 4B...second liner plate, 41...axial flange, 42...main body, 43...circumferential flange, 44...bolt joint, 45...bolt joint, 46A...reinforcing plate, 46B...reinforcing rib, 46C...connecting fitting, 47...reinforcing member, 48...reinforcing member, 49...connecting member, 441...bolt, 442...nut, 451...bolt, 452...nut, 471...base, 472...wall, 481...connection portion, 482...rod-shaped portion, 5...inner solidification material, 6...outer solidification material.

Claims

1. a liner plate arranged in a depth direction and a circumferential direction along a wall surface of a shaft formed by excavating the ground, the liner plate having a main body portion, an axial flange extending in the depth direction, and a circumferential flange extending in the circumferential direction; an outer solidification material filled between the liner plate and the wall surface of the shaft; an inner solidification material filled inside the liner plate; A deep foundation with The liner plates include a first liner plate arranged at the top of the deep foundation with the circumferential connecting positions aligned between the multiple depth-wise stages, and a second liner plate arranged at the bottom of the deep foundation with the circumferential connecting positions shifted between the multiple depth-wise stages.

2. The deep foundation foundation according to claim 1, wherein the plate thickness of the axial flange of the first liner plate is 1.3 mm or more thicker than the plate thickness of the main body portion of the first liner plate.

3. The deep foundation foundation according to claim 1, wherein the number of the first liner plates arranged in the circumferential direction is greater than the number obtained by dividing the circumferential length by 1570 mm and rounding up.

4. The deep foundation foundation according to claim 1, further comprising a connecting member interposed between the axial flanges across multiple depth-wise stages of the first liner plate.

5. The deep foundation foundation according to any one of claims 1 to 4, further comprising reinforcing members installed at both ends of the circumferential flange of the first liner plate.

6. The deep foundation foundation described in claim 5, wherein the reinforcing member includes a reinforcing plate interposed between the bolts and nuts connecting the circumferential flanges of the first liner plates adjacent in the depth direction and the circumferential flanges.

7. The deep foundation foundation according to claim 5 , wherein the reinforcing member includes a reinforcing rib joined to a corner portion between the circumferential flange and the axial flange of the first liner plate.

8. The deep foundation foundation according to claim 5, wherein the reinforcing member includes a connecting fitting that clamps the circumferential flanges of the first liner plates adjacent in the depth direction.

9. The deep foundation foundation described in claim 5, wherein the reinforcing member has a groove portion into which a cross-shaped intersection formed by the axial flanges and the circumferential flanges of four adjacent first liner plates in the depth direction and the circumferential direction can be inserted.

10. The deep foundation foundation described in claim 5, wherein the reinforcing member has a rod-shaped portion that can be inserted into the corner between each of the axial flanges and the circumferential flanges at the cross-shaped intersection formed by the axial flanges and the circumferential flanges of four of the first liner plates adjacent in the depth direction and the circumferential direction.

11. A construction method for a deep foundation including an excavation step of excavating the ground to form a shaft, a liner plate installation step of arranging liner plates in the depth direction and circumferential direction along the wall surface of the shaft, an outer filling step of filling an outer solidification material between the liner plate and the wall surface of the shaft, and an inner filling step of filling an inner solidification material inside the liner plate, The liner plate installation process is a construction method for a deep foundation, and includes a first liner plate installation process in which the liner plates are arranged at the top of the deep foundation by aligning the circumferential connecting positions between the multiple depth-wise stages, and a second liner plate installation process in which the liner plates are arranged at the bottom of the deep foundation by shifting the circumferential connecting positions between the multiple depth-wise stages.

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