Pile foundation structure, and construction method for pile foundation structure

Abstract

To provide a pile foundation structure, and a construction method for the pile foundation structure, allowing easy adjustment of the height of a foundation member made of precast concrete upon installation of the foundation member onto a foundation pile.SOLUTION: A pile foundation structure 1 includes a foundation pile 2 and a precast-concrete foundation member 3 to be installed on the foundation pile 2, the pile foundation structure 1 being provided with a level adjustment steel member 5 including a base part 51 that is installed on the ground G around a pile head part 2h of the foundation pile 2 or a leveling concrete layer 71 on the ground G and a rise part 52 that extends upward from the base part 51 and includes a level adjustment mechanism 55 to fix the foundation member 3 by adjusting the height position of the foundation member 3, wherein the foundation member 3 is positioned apart upward from the pile head part 2h of the foundation pile 2, with an outer peripheral side surface 33 positioned along the rise part 52 of the level adjustment steel member 5, and the outer peripheral side surface 33 of the foundation member 3 is fixed on the rise part 52 with the level adjustment mechanism.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pile foundation structure including foundation piles and precast concrete foundation members provided on the foundation piles, and a method for constructing the pile foundation structure. [Background technology]

[0002] A foundation structure can be constructed by placing precast concrete foundation members on top of foundation piles. In this case, using precast concrete for the foundation members can shorten the construction period and make construction easier. For example, Patent Document 1 describes a joint structure for joining the superstructure and piles of a building, which includes a storage section for accommodating the pile head, a precast concrete cap member that is joined to the superstructure and installed to cover the pile head, and a cushioning material that is placed between the outer peripheral surface of the pile head and the inner surface of the storage section of the foundation member.

[0003] When installing precast concrete foundation members as described above, it is necessary to accurately adjust the height of the foundation members. In this regard, Patent Document 2 describes a configuration that includes a precast concrete footing member with a recess formed on the underside to cover the pile head of the pile, and a filler that is filled between the recess and the pile head to join the footing member to the pile head, and the footing member is placed on an installation plate that is installed on the ground surrounding the pile head. In Patent Document 2, the installation plate is a concrete flat plate or a steel plate, and is installed so that when the footing member is placed on this installation plate, the footing member is positioned horizontally at a height determined by the design. Patent Document 3 also describes a pile foundation structure comprising foundation piles and a precast concrete foundation member placed on the foundation piles, in which a recess is formed on the underside of the foundation member to accommodate the head of the foundation pile, and which comprises a level adjustment material placed on the ground surface around the foundation pile or on a basing concrete layer on the ground surface to support the foundation member, a cover member to cover the head of the foundation pile, and a filler filled between the cover member and the recess of the foundation member. In Patent Document 3, the level adjustment material is made of laminated thin metal plates, and the height position of the upper surface can be adjusted by changing the number of laminated thin plates, and the foundation member is placed on such a level adjustment material.

[0004] In Patent Documents 2 and 3, the height of a foundation member such as a footing member is adjusted by being placed on a plate-shaped installation plate or level adjustment material with an adjusted thickness. In such a configuration, in order to adjust the height of the foundation member, it is necessary to calculate the distance between the bottom surface of the foundation member and the surface of the ground, etc., on which the foundation member is to be installed when the foundation member is installed at the planned height, and to process the installation plate or level adjustment material by stacking thin metal plates or cutting a concrete plate material so that the thickness exactly matches the distance. In addition, if the installation plate or level adjustment material with the adjusted thickness is once installed on the surface of the ground, etc., and the foundation member is installed on it, and the foundation member is not installed at the planned height, it is necessary to lift the installed foundation member, process the level adjustment material so as to adjust the thickness again, and reinstall the foundation member, and repeat this procedure until the foundation member is installed at the planned height. Therefore, it is not easy to adjust the height of the foundation member. When installing a precast concrete foundation member on foundation piles, it is desired to be able to more easily adjust the height of the foundation member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-190097 A [Patent Document 2] JP 2015-200094 A [Patent Document 3] JP 2022-124976 A Summary of the Invention [Problem to be solved by the invention]

[0006] The problem that the present invention aims to solve is to provide a pile foundation structure and a method for constructing a pile foundation structure that allow the height of a precast concrete foundation member to be easily adjusted when installing the foundation member on top of a foundation pile. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following means. In other words, the pile foundation structure of the present invention is a pile foundation structure comprising a foundation pile and a precast concrete foundation member placed on the foundation pile, and is provided with a level-adjusting steel material having a base placed on the ground around the head of the foundation pile or on a basin concrete layer on the ground, and a rising portion extending upward from the base and provided with a level adjustment mechanism for adjusting the height position of the foundation member and fixing the foundation member, the foundation member is positioned above the head of the foundation pile and such that its outer peripheral side surface is aligned with the rising portion of the level-adjusting steel material, the outer peripheral side surface of the foundation member is fixed to the rising portion via the level adjustment mechanism, and a cement-based material is filled between the head of the foundation pile and the foundation member to form a bottom concrete portion. According to the above-mentioned configuration, the foundation member is provided at a distance above the head of the foundation pile. The foundation member is provided so that the outer peripheral side of the foundation member is aligned with the rising part of the level adjustment steel material that is provided so as to extend upward from the base part installed on the ground around the head of the pile or the sacrificial concrete layer on the ground, and is fixed via the level adjustment mechanism of the level adjustment steel material. In this way, the level adjustment steel material is provided on the side of the foundation member so as to be aligned with the outer peripheral side, not below the foundation member. Therefore, when installing the foundation member, after positioning the foundation member so as to rest at an appropriate height using a lifting machine or the like, the height position of the foundation member is adjusted by the level adjustment mechanism at a position to the side of the foundation member, and the foundation member and the level adjustment steel material are fixed to support the foundation member. In such an operation, there is no need to perform a process of calculating in advance the distance between the bottom surface of the foundation member and the ground or the sacrificial concrete layer on the ground, or to process the thickness of the member used for level adjustment according to the calculated distance. Even when the height of a foundation member that has already been fixed needs to be readjusted, the fixation can be released while supporting the foundation member with a lifting machine or the like, the height of the foundation member can be readjusted with the level adjustment mechanism, and then the foundation member and the level adjustment steel material can be fixed again. Even in such a procedure, there is no need to process the thickness of the member used for level adjustment. The above-mentioned effects are combined to provide a pile foundation structure that allows the height of a precast concrete foundation member to be easily adjusted when the foundation member is installed on the foundation pile.

[0008] In one aspect of the present invention, the level adjustment mechanism is a long hole extending in the vertical direction formed in the raised portion, and a bolt is fastened to the outer peripheral side surface of the foundation member through the long hole in the level adjustment steel material. According to the above-mentioned configuration, since the bolt is inserted into the long hole formed to extend in the vertical direction, by adjusting the height of the foundation member up or down with the base of the level adjustment steel material placed on the ground or the sacrificial concrete layer on the ground, even if the relative height positions of the foundation member and the level adjustment steel material change, the bolt can be inserted into the long hole at any height position corresponding to this. Therefore, it is not necessary to perform the work of opening a hole for inserting the bolt in the level adjustment steel material at a position corresponding to the height of the foundation member.

[0009] In another aspect of the present invention, the pile head of the foundation pile is covered with a pile head cap to form a gap on the side of the pile head, and the bottom concrete portion is formed between the pile head cap and the foundation member. According to this configuration, by providing a pile head cap on the pile head of the foundation pile, it is possible to form a pile foundation structure in which the foundation pile and the precast concrete foundation member are semi-rigidly joined rather than rigidly. By semi-rigidly joining the foundation pile and the precast concrete foundation member, the rotational constraint of the pile head at the joint between the foundation pile and the foundation member is alleviated, thereby reducing the earthquake load acting on the foundation pile and improving the structural safety of the pile foundation structure.

[0010] The present invention also provides a method for constructing a pile foundation structure comprising a foundation pile and a precast concrete foundation member provided on the foundation pile, the method comprising the steps of: driving the foundation pile into the ground and causing the head of the foundation pile to protrude upward from the ground; installing a level-adjusting steel material having a base and a rising portion provided with a level adjustment mechanism for adjusting the height position of the foundation member and fixing the foundation member such that the base is located on the ground or a basing concrete layer on the ground and the rising portion extends upward from the base; positioning the foundation member at a distance above the head of the foundation pile and supporting the foundation member along the rising portion of the level-adjusting steel material on the outer peripheral side surface of the foundation member while adjusting the height position via the level adjustment mechanism; and filling a cement-based material between the head of the foundation pile and the underside of the foundation member to form a bottom concrete portion. According to this configuration, after the level adjustment steel material is installed on the ground or the sacrificial concrete layer on the ground, the foundation member is positioned above and away from the head of the foundation pile, and the foundation member is supported along the level adjustment steel material while adjusting the height position via the level adjustment mechanism on the outer peripheral side surface of the foundation member. In this way, the level adjustment steel material is provided on the side of the foundation member so as to support the foundation member on the outer peripheral side surface, not below the foundation member. Therefore, when installing the foundation member, the foundation member is positioned to be stationary at an appropriate height using a lifting machine or the like, and the height position of the foundation member is adjusted by the level adjustment mechanism at a position on the side of the foundation member, so that the foundation member is supported by the level adjustment steel material. In this type of work, there is no need to perform a process of calculating in advance the distance between the bottom surface of the foundation member and the ground or the sacrificial concrete layer on the ground, or to process the thickness of the member used for level adjustment according to the calculated distance. Therefore, when installing a precast concrete foundation member on top of the foundation piles, the height of the foundation member can be easily adjusted. Effect of the Invention

[0011] According to the present invention, it is possible to provide a pile foundation structure and a method for constructing a pile foundation structure that allow the height of a precast concrete foundation member to be easily adjusted when placing the foundation member on a foundation pile. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a configuration of a pile foundation structure according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of a portion of the pile foundation structure of FIG. 1 corresponding to a foundation member, taken along the line A in FIG. [Diagram 3] FIG. 1 is a diagram showing the flow in the construction direction of a pile foundation structure. [Figure 4] 13 is a diagram showing the process of covering the pile head with a pile cap in the method of constructing a pile foundation structure. FIG. [Diagram 5] FIG. 13 is a diagram showing a step of installing a level adjustment steel material in a method for constructing a pile foundation structure. [Figure 6] 1 is a diagram showing a process of supporting a foundation member with level-adjusting steel materials in a method for constructing a pile foundation structure. FIG. [Figure 7] FIG. 2 is a diagram showing a step of forming a bottom concrete portion in a method for constructing a pile foundation structure. [Figure 8] FIG. 4 is a cross-sectional view showing a pile foundation structure according to a second modified example of the first embodiment of the present invention. [Figure 9] FIG. 11 is a partial cross-sectional view of the periphery of a level adjustment steel material in a pile foundation structure according to a third modified example of the first embodiment of the present invention. [Figure 10] FIG. 5 is a cross-sectional view showing a pile foundation structure according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention relates to a pile foundation structure including a foundation pile and a precast concrete PCa foundation member provided on the top of the foundation pile, and a method for constructing the pile foundation structure. The pile foundation structure includes a pile foundation structure (first embodiment) in which a pile head cap is provided on the pile head where the foundation pile and the PCa foundation member are semi-rigidly joined, and a pile foundation structure (second embodiment) in which no pile head cap is provided between the foundation pile and the PCa foundation member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the accompanying drawings, an embodiment for carrying out a pile foundation structure and a method for constructing a pile foundation structure according to the present invention will be described based on the drawings. A cross-sectional view showing the configuration of the pile foundation structure according to the first embodiment of the present invention is shown in Fig. 1. Fig. 2 is a cross-sectional view of a portion corresponding to a foundation member of the pile foundation structure in Fig. 1, taken along the arrow A. As shown in FIG. 1, the pile foundation structure 1 mainly comprises a foundation pile 2, a foundation member 3, a bottom concrete portion 4, and a level adjustment steel material 5. The foundation pile 2 is provided so as to extend vertically in the ground G. The foundation pile 2 is made of, for example, precast concrete. A pile head 2h of the foundation pile 2 protrudes upward from a surface Gf1 of the ground G. In this embodiment, the surface Gf1 forms the bottom surface of a recess K that is formed by excavating the ground G so as to be recessed below a surface Gf2 of the surrounding ground G.

[0014] A pile head cap 6 is placed on the pile head 2h of the foundation pile 2. The pile head cap 6 is formed of, for example, a steel plate. The pile head cap 6 is integrally provided with a cap top plate 61 that covers the upper surface of the pile head 2h, and a peripheral wall portion 62 that extends downward from the outer periphery of the cap top plate 61 and surrounds the side surface 2s of the foundation pile 2 from the outside in a truncated cone shape. In this embodiment, the peripheral wall portion 62 is inclined so as to move away from the pile head 2h outward as it extends downward from the outer periphery of the cap top plate 61. The lower end of the peripheral wall portion 62 is in contact with the surface Gf1 of the ground G. Such a peripheral wall portion 62 is provided so as to form a gap D between the side surface 2s of the pile head 2h.

[0015] The foundation member 3 is provided on the foundation pile 2. The foundation member 3 is provided at a distance upward from the pile head 2h and the pile head cap 6 of the foundation pile 2. The foundation member 3 is made of precast concrete. The foundation member 3 is, for example, rectangular in plan view and has a lower surface 31, an upper surface 32, and an outer peripheral side surface 33. The lower surface 31 is formed facing vertically downward. The upper surface 32 is formed a predetermined distance above the lower surface 31 and facing vertically upward. The outer peripheral side surface 33 is formed so as to connect the outer peripheral edge of the lower surface 31 and the outer peripheral edge of the upper surface 32. The outer peripheral side surface 33 is formed facing the four sides of the rectangular foundation member 3 in plan view.

[0016] In this embodiment, the outer circumferential side surface 33 has a lower outer circumferential side surface 33a, a middle outer circumferential side surface 33b, and an upper outer circumferential side surface 33c. The lower outer peripheral side surface 33 a is formed on the lower part of the base member 3 . The middle outer peripheral side surface 33b is formed between the lower outer peripheral side surface 33a and the upper outer peripheral side surface 33c located higher. The middle outer peripheral side surface 33b is formed closer to the center (inner) of the base member 3 than the lower outer peripheral side surface 33a. An upwardly facing step surface 33d is formed between the lower outer peripheral side surface 33a and the middle outer peripheral side surface 33b. The upper outer peripheral side surface 33c is formed on the upper part of the base member 3. The upper outer peripheral side surface 33c is formed closer to the center (inner) of the base member 3 than the intermediate outer peripheral side surface 33b. An inclined surface 33s is formed between the intermediate outer peripheral side surface 33b and the upper outer peripheral side surface 33c, extending upward toward the center of the base member 3.

[0017] As shown in Figs. 1 and 2, first slab connection bars 35, second slab connection bars 36, cage bars 37, and bottom reinforcing bars 38 are buried inside foundation member 3. The first slab connection bars 35 extend in a direction perpendicular to the plane of the paper in Fig. 1. A plurality of the first slab connection bars 35 are arranged at intervals in a direction parallel to the top surface 32 (left-right direction on the plane of Fig. 1). The first slab connection bars 35 are provided in three tiers at intervals in the vertical direction. The first slab connection bars 35 are provided at a height corresponding to the upper outer peripheral side surface 33c and at a height corresponding to the middle outer peripheral side surface 33b. Both ends of each first slab connection bar 35 are connected to a first connection sleeve 35j exposed on the upper outer peripheral side surface 33c and the middle outer peripheral side surface 33b. The second slab connection bars 36 extend in the left-right direction of the paper in Fig. 1. A plurality of the second slab connection bars 36 are arranged at intervals in a direction parallel to the top surface 32 (a direction perpendicular to the paper in Fig. 1). The second slab connection bars 36 are provided in three tiers at intervals in the up-down direction. The second slab connection bars 36 are provided at a height corresponding to the upper outer peripheral side surface 33c and at a height corresponding to the middle outer peripheral side surface 33b. Both ends of each second slab connection bar 36 are connected to second connection sleeves 36j exposed on the upper outer peripheral side surface 33c and the middle outer peripheral side surface 33b. As shown in FIG. 1, the cage reinforcement 37 is provided in a cage shape along the upper surface 32 and the outer peripheral side surface 33 of the base member 3 so as to surround the inner structure of the base member 3 from the outside. A plurality of bottom reinforcing bars 38 are arranged along the lower surface 31 of the foundation member 3. The plurality of bottom reinforcing bars 38 are arranged in a lattice shape in a plan view.

[0018] The base member 3 has a lower surface 31 with a central portion formed with a lower surface recess 34 recessed upward. A concrete injection hole 39 is formed in the center of the foundation member 3, extending in the vertical direction and opening into the upper surface 32 and the lower surface recess 34. As a result, the lower space and the upper space of the foundation member 3 are connected via the concrete injection hole 39. The diameter of the concrete injection hole 39 is smaller than the diameter of the lower surface recess 34. In this embodiment, a base plate 81 is provided on the upper surface 32 of the foundation member 3. A laminated rubber bearing 100 is fixed onto the base plate 81, and is interposed between the foundation member 3 and a building main body (not shown) constructed above the foundation member 3. The base plate 81 is made of, for example, a steel plate that is rectangular in plan view. Anchoring members 82 extending downward and embedded in the foundation member 3 are integrally provided on the underside of the base plate 81. A plurality of connection sleeves 83 to which bolts (not shown) for fixing the laminated rubber bearing 100 are connected are provided on the base plate 81. The plurality of connection sleeves 83 are arranged concentrically. The lower end of each connection sleeve 83 is connected to an anchor bar 84. The connection sleeves 83 are embedded in the foundation member 3 together with the anchor bar 84. The laminated rubber bearing 100 is fixed to the foundation member 3 by fastening each of a plurality of bolts (not shown) from above to the connection sleeves 83 via the base plate 81.

[0019] As will be described later, below the foundation member 3, the bottom concrete portion 4 is formed by pouring concrete in place. When constructing the pile foundation structure 1, the foundation member 3 is supported by level-adjusting steel materials 5 until the bottom concrete portion 4 is formed. The level-adjusting steel materials 5 are placed in a sacrificial concrete layer 71 formed on the ground G around the pile head 2h. The sacrificial concrete layer 71 has crushed stones 71a laid on the surface Gf1 of the ground G around the pile head 2h, and level concrete 71b poured on the crushed stones 71a.

[0020] 2, a plurality of level adjustment steel materials 5 are provided at intervals in the circumferential direction of the base member 3. For example, two level adjustment steel materials 5 are provided on each of the four outer peripheral side surfaces 33. 1, each level adjustment steel material 5 integrally comprises a plate-shaped base portion 51 that fits along the surface of the sacrificial concrete layer 71, and a rising portion 52 that extends upward from one end of the base portion 51. The base portion 51 is fixed to the sacrificial concrete layer 71 by fixing bolts 53. The rising portion 52 is provided so as to fit along the lower outer peripheral side surface 33a of the outer peripheral side surface 33. In other words, the foundation member 3 is positioned so that the outer peripheral side surface 33 fits along the rising portion 52 of the level adjustment steel material 5. The rising portion 52 is provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3 when the foundation member 3 is supported by the level adjustment steel material 5. In this embodiment, the level adjustment mechanism 55 is a long hole 55A formed in the rising portion 52 so as to extend in the vertical direction. The rising portion 52 is fixed to the outer circumferential side surface 33 by tightening the bolt 58 inserted through the long hole 55A from the outside. In other words, the foundation member 3 is supported by the level adjustment steel material 5 by tightening the bolt 58 through the long hole 55A. In this way, the outer circumferential side surface 33 of the foundation member 3 is fixed to the rising portion 52 via the level adjustment mechanism 55, i.e., the long hole 55A. Here, the height position of the foundation member 3 can be adjusted by adjusting the vertical position of the bolt 58 tightened to the outer circumferential side surface 33 within the range of extension of the long hole 55A.

[0021] The bottom concrete portion 4 is formed by filling the space between the pile head 2h and the foundation member 3 with a cement-based material by casting in place. The bottom concrete portion 4 is formed in an area that overlaps with the lower surface 31 of the foundation member 3 in a plan view. More precisely, the bottom concrete portion 4 is formed between the pile head cap 6 and the foundation member 3. The bottom concrete portion 4 is formed so as to extend upward so as to be continuous with the inside of the concrete injection hole 39 of the foundation member 3. Mesh reinforcement 45 is embedded in the bottom concrete portion 4 to prevent cracking of the bottom concrete portion 4. In this way, the bottom concrete portion 4 is provided between the pile head cap 6 provided on the pile head 2h of the foundation pile 2 and the underside of the foundation member 3, thereby joining the foundation pile 2 to the precast concrete foundation member 3. Here, the pile head cap 6 forms a gap D between the side surface 2s of the pile head 2h and the pile head cap 6, so that the foundation pile 2 and the precast concrete foundation member 3 are not rigidly joined, but rather have a semi-rigidly joined structure. Furthermore, since a bottom surface recess 34 is formed on the bottom surface 31 of the foundation member 3, horizontal displacement due to an earthquake or the like is transmitted well between the bottom concrete portion 4 and the foundation member 3.

[0022] A mat slab 110 is formed around the foundation member 3 so as to cover the surface Gf2 of the ground G. The lower outer peripheral side surface 33a of the foundation member 3 and the bottom concrete portion 4 are backfilled with a backfilling material 101 such as mortar or earth and sand in the recess K of the ground G. The mat slab 110 is formed with a predetermined thickness on crushed stones 102 laid so as to cover the surface Gf2 of the ground G and the backfilling material 101, and on concrete 103 poured on the crushed stones 102. A plurality of mat slab reinforcements 111 are embedded in the mat slab 110. The ends of each mat slab reinforcement 111 are connected to the first connection sleeve 35j and the second connection sleeve 36j.

[0023] Next, a description will be given of a method for constructing the above-mentioned pile foundation structure 1. Fig. 3 is a diagram showing the flow in the construction direction of the pile foundation structure. As shown in Figure 3, the method of constructing the pile foundation structure 1 includes a step S1 of driving the foundation pile 2 into the ground G, a step S2 of installing level-adjusting steel materials 5, a step S3 of supporting the foundation member 3 with the level-adjusting steel materials 5, and a step S4 of forming the bottom concrete portion 4. FIG. 4 is a diagram showing a step of covering a pile head with a pile cap in a method for constructing a pile foundation structure. As shown in FIG. 4, in step S1 of driving the foundation pile 2 into the ground G, first, the ground G is excavated around the area where the foundation pile 2 is to be installed to form a recess K, and the bottom surface of the recess K, i.e., the surface Gf1 of the ground G, is leveled. Next, the foundation pile 2 is driven into the ground G. When driving the foundation pile 2, it is confirmed that the misalignment of the foundation pile 2 in the horizontal plane is within a predetermined error range. In addition, the vertical level of the foundation pile 2 is confirmed so that the pile head 2h protrudes upward from the surface Gf1 of the ground G within a predetermined dimensional range. Thereafter, the pile head 2h of the foundation pile 2 protruding upward from the surface Gf1 is covered with the pile head cap 6. Furthermore, crushed stone 71a is laid on the surface Gf1 of the ground G around the pile head 2h (pile head cap 6), and level concrete 71b is poured on top of the crushed stone 71a to form a basin concrete layer 71. In addition, mesh reinforcement 45 is arranged on the sacrificial concrete layer 71 to prevent cracks in the bottom concrete portion 4.

[0024] FIG. 5 is a diagram showing a step of installing a level adjusting steel material in the method for constructing a pile foundation structure. As shown in Fig. 5, in step S2 of installing the level adjustment steel materials 5, a plurality of level adjustment steel materials 5 are installed at predetermined positions on the sacrificial concrete layer 71. Each of the plurality of level adjustment steel materials 5 is installed so that the base portion 51 is aligned along the surface of the sacrificial concrete layer 71 and the rising portion 52 extends upward. Each of the plurality of level adjustment steel materials 5 is installed so that it is positioned and oriented so that when the foundation member 3 is later installed in the planned position, the outer peripheral side surface 33 of the foundation member 3 is aligned along the level adjustment steel material 5. Thereafter, the base portion 51 is fixed to the sacrificial concrete layer 71 by fixing bolts 53.

[0025] FIG. 6 is a diagram showing a step of supporting a foundation member with a level adjusting steel material in a method for constructing a pile foundation structure. As shown in Fig. 6, in step S3 of supporting the foundation member 3 with the level-adjusting steel material 5, the precast concrete foundation member 3 previously manufactured in a factory or the like is lifted by a crane or the like and positioned above the pile head 2h of the foundation pile 2 and with the outer circumferential side surface 33 aligned with the level-adjusting steel material 5. Next, the outer circumferential side surface 33 of the foundation member 3 is supported along the rising portion 52 of the level-adjusting steel material 5 while the height position is adjusted based on the design value via the level adjustment mechanism 55. More specifically, the bolt 58 is tightened through the long hole 55A formed in the level-adjusting steel material 5 so as to extend in the vertical direction, so that the foundation member 3 with the adjusted height position is supported by the level-adjusting steel material 5.

[0026] FIG. 7 is a diagram showing a step of forming a bottom concrete portion in the method for constructing a pile foundation structure. As shown in FIG. 7, in step S4 of forming the bottom concrete portion 4, a formwork (not shown) is set on the basing concrete layer 71 according to the outer shape of the bottom concrete portion 4 to be formed. As a result, the space between the lower surface 31 of the foundation member 3 and the surface Gf1 of the ground G is blocked from the side by the formwork. Then, a cement-based material is filled from above the foundation member 3 through the concrete injection hole 39 into the space between the pile head 2h of the foundation pile 2, more specifically, the pile head cap 6 covering the pile head 2h, and the lower surface 31 of the foundation member 3, to form the bottom concrete portion 4. The cement-based material is filled up to the inside of the concrete injection hole 39. After the cement-based material forming the bottom concrete portion 4 hardens and develops a predetermined strength, the formwork is removed.

[0027] 1, the lower outer peripheral side surface 33a of the foundation member 3 and the periphery of the bottom concrete portion 4 in the recess K are backfilled with backfilling material 101 such as mortar or soil, crushed stone 102 is laid on top, and concrete 103 is poured. Furthermore, mat slab reinforcement bars 111 are arranged above the concrete 103. The ends of each mat slab reinforcement bar 111 are connected to the first connection sleeve 35j and the second connection sleeve 36j. Next, concrete is poured to a predetermined thickness to form the mat slab 110. Thereafter, the laminated rubber bearing 100 is attached onto the foundation member 3, and the main body of the building is constructed on top of it.

[0028] The pile foundation structure 1 as described above is a pile foundation structure 1 comprising a foundation pile 2 and a foundation member 3 made of precast concrete placed on the foundation pile 2, and is provided with a level adjustment steel material 5 comprising a base 51 installed in a basin concrete layer 71 on the ground G around the pile head 2h of the foundation pile 2, and a rising portion 52 extending upward from the base 51 and provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3, the foundation member 3 is positioned above the pile head 2h of the foundation pile 2 and such that the outer peripheral side surface 33 (lower outer peripheral side surface 33a) is aligned with the rising portion 52 of the level adjustment steel material 5, the outer peripheral side surface 33 of the foundation member is fixed to the rising portion 52 via the level adjustment mechanism 55, and a cement-based material is filled between the pile head 2h and the foundation member 3 to form a bottom concrete portion 4. According to the above-mentioned configuration, the foundation member 3 is provided at a distance above the pile head 2h of the foundation pile 2. The foundation member 3 is provided so that the outer peripheral side surface 33 of the foundation member 3 is aligned with the rising portion 52 of the level adjustment steel material 5, which is provided so as to extend upward from the base portion 51 installed on the dummy concrete layer 71 on the ground G around the pile head 2h, and is fixed via the level adjustment mechanism 55 of the level adjustment steel material 5. In this way, the level adjustment steel material 5 is provided on the side of the foundation member 3 so as to be aligned with the outer peripheral side surface 33, rather than below the foundation member 3. For this reason, when installing the foundation member 3, the foundation member 3 is positioned so as to be stationary at an appropriate height using a lifting machine or the like, and then the height position of the foundation member 3 is adjusted by the level adjustment mechanism 55 at a position to the side of the foundation member 3, and the foundation member 3 and the level adjustment steel material 5 are fixed, so that the level adjustment steel material 5 supports the foundation member 3. In such work, there is no need to perform processes such as calculating in advance the distance between the underside 31 of the foundation member 3 and the sacrificial concrete layer 71 on the ground G, or processing the thickness of the member used for level adjustment to match the calculated distance. Even when the height of the foundation member 3 that has been fixed needs to be readjusted, the fixation can be released while supporting the foundation member 3 with a lifting machine or the like, and the height of the foundation member 3 can be readjusted with the level adjustment mechanism 55, after which the foundation member 3 and the level adjustment steel material 5 can be fixed again. Even in such an operation, there is no need to process the thickness of the member used for level adjustment. The above-mentioned effects are combined to provide a pile foundation structure 1 that allows the height of the precast concrete foundation member 3 to be easily adjusted when the precast concrete foundation member 3 is installed on the foundation pile 2.

[0029] In particular, in the above-mentioned configuration, the foundation member 3 is provided above the foundation pile 2 at a distance from the foundation pile 2, and then the bottom concrete portion 4 is poured between the foundation pile 2 and the foundation member 3. Therefore, the installation position of the foundation member 3 can be determined independently of the position of the foundation pile 2, so that even if the installation position or height of the foundation pile 2 deviates slightly from the intended position when installing the foundation member 3, it is possible to install the foundation member 3 at the planned position. Therefore, even if the height position or horizontal position of the foundation pile 2 deviates due to a construction error when erecting the foundation pile 2, the construction error of the foundation pile 2 can be absorbed.

[0030] In addition, the level adjustment mechanism 55 is a long hole 55A extending in the vertical direction formed in the rising portion 52, and a bolt 58 is fastened to the outer peripheral side surface 33 of the foundation member 3 through the long hole 55A of the level adjustment steel material 5. According to the above-mentioned configuration, the bolt 58 is inserted through the long hole 55A formed to extend in the vertical direction, so that by adjusting the height of the foundation member 3 up or down with the base 51 of the level adjustment steel material 5 placed on the sacrificial concrete layer 71 on the ground G, even if the relative height positions of the foundation member 3 and the level adjustment steel material 5 change, the bolt 58 can be inserted through the long hole 55A at any height position corresponding to this. Therefore, there is no need to perform the work of opening a hole for inserting the bolt 58 in the level adjustment steel material 5 at a position corresponding to the height of the foundation member 3.

[0031] In addition, a pile head cap 6 is placed on the pile head 2h of the foundation pile 2 to form a gap D on the side surface 2s of the pile head 2h, and a bottom concrete portion 4 is formed between the pile head cap 6 and the foundation member 3. According to this configuration, by providing the pile head cap 6 on the pile head 2h of the foundation pile 2, it is possible to form a pile foundation structure 1 in which the foundation pile 2 and the precast concrete foundation member 3 are semi-rigidly joined rather than rigidly joined. By semi-rigidly joining the foundation pile 2 and the precast concrete foundation member 3, the rotation constraint of the pile head 2h at the joint between the foundation pile 2 and the foundation member 3 is alleviated, thereby reducing the earthquake load acting on the foundation pile 2 and improving the structural safety of the pile foundation structure 1.

[0032] The construction method of the pile foundation structure 1 as described above is a construction method of the pile foundation structure 1 including the foundation piles 2 and the precast concrete foundation members 3 provided on the foundation piles 2, and includes a step S1 of driving the foundation piles 2 into the ground G and causing the pile heads 2h of the foundation piles 2 to protrude upward from the ground G, and a step S2 of driving the level adjustment steel material 5 including a base 51 and a rising portion 52 provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3 to the ground G, the step S3 of driving the level adjustment steel material 5 including a base 51 and a rising portion 52 provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3 to the ground G. The method includes a step S2 of installing the level adjustment steel material 5 so that the level adjustment steel material 5 is positioned above the base 51 and the rising portion 52 extends upward from the base 51; a step S3 of positioning the foundation member 3 at a distance above the pile head 2h of the foundation pile 2 and supporting the foundation member 3 along the rising portion 52 of the level adjustment steel material 5 on its outer peripheral side surface 33 (lower outer peripheral side surface 33a) while adjusting its height position via a level adjustment mechanism 55; and a step S4 of filling a cement-based material between the pile head 2h of the foundation pile 2 and the underside 31 of the foundation member 3 to form a bottom concrete portion 4. According to this configuration, after the level-adjusting steel material 5 is installed on the dummy concrete layer 71 on the ground G, the foundation member 3 is positioned above and away from the pile head 2h of the foundation pile 2, and is supported along the rising portion 52 of the level-adjusting steel material 5 on the outer peripheral side surface 33 of the foundation member 3 while adjusting the height position via the level adjustment mechanism 55. In this way, the level-adjusting steel material 5 is provided on the side of the foundation member 3 so as to support the foundation member 3 on the outer peripheral side surface 33, not below the foundation member 3. Therefore, when installing the foundation member 3, the foundation member 3 is positioned so as to rest at an appropriate height using a lifting machine or the like, and then the foundation member 3 and the level-adjusting steel material 5 are fixed at a position on the side of the foundation member 3 while adjusting the height position of the foundation member 3 by the level adjustment mechanism 55, so that the foundation member 3 is supported by the level-adjusting steel material 5. In such work, there is no need to perform processes such as calculating in advance the distance between the underside 31 of the foundation member 3 and the sacrificial concrete layer 71 on the ground G, or processing the thickness of the member used for level adjustment to match the calculated distance. Therefore, when placing a precast concrete foundation member 3 on the foundation pile 2, the height of the foundation member 3 can be easily adjusted.

[0033] (First Modification of the First Embodiment) The pile foundation structure and the method for constructing the pile foundation structure of the present invention are not limited to the first embodiment described above with reference to the drawings, and various modifications are possible within the technical scope. For example, in the first embodiment, the plurality of level adjusting steel materials 5 are provided at intervals in the circumferential direction, but this is not limited to this. For example, the formwork used to form the bottom concrete portion 4 may also be used as the level adjusting steel materials 5, and the formwork may support the foundation member 3 after forming the long holes 55A in the formwork. In this case, after fastening the level-adjusting steel material (formwork) 5 and the foundation member 3 with bolts and supporting the foundation member 3 with the level-adjusting steel material 5, there is no need to set up formwork to form the bottom concrete portion 4. In this case, in order to prevent the concrete poured when forming the bottom concrete portion 4 from flowing out of the long hole 55A, it is desirable to block the long hole 55A after the level adjustment of the foundation member 3 is completed and before pouring the concrete to form the bottom concrete portion 4.

[0034] (Second Modification of the First Embodiment) FIG. 8 is a cross-sectional view showing a pile foundation structure according to a second modified example of the first embodiment of the present invention. In the first embodiment, the laminated rubber bearing 100 is provided on the foundation member 3, but this is not limited to the above. As shown in Fig. 8, a base plate 200 for providing a sliding bearing may be provided on the foundation member 3. The base plate 200 has a plurality of mounting holes 201 for mounting the sliding bearing. Here, for example, when the area of ​​the sliding plate of the sliding bearing is large, the size of the foundation member 3 when viewed in plan also becomes large. For this reason, in order to further increase the degree of restraint of the relative displacement in the horizontal direction between the foundation member 3 and the bottom concrete portion 4, a peripheral recess 130 recessed upward may be formed on the outer periphery side of the lower surface recess 34 on the lower surface 31 of the foundation member 3. Even when a laminated rubber bearing 100 is provided on a foundation member 3 as in the first embodiment described above, for example when the laminated rubber bearing 100 has a large diameter, an outer peripheral recess 130 may be formed as in this modified example.

[0035] (Third modified example of the first embodiment) A partial cross-sectional view of the periphery of the level adjustment steel material of the pile foundation structure according to the third modified example of the first embodiment of the present invention is shown in Fig. 9. For the sake of simplicity, Fig. 9 shows a state immediately before the bottom concrete portion 4 is poured. In this modified example, the structure of the level adjustment steel material 5A is different from that of the above embodiment. The level adjustment steel material 5A has a plate-shaped base portion 51 that fits along the surface of the sacrificial concrete layer 71, and a rising portion 52A. The base 51 is provided so as to fit along the surface of the sacrificial concrete layer 71. The base 51 is fixed to the sacrificial concrete layer 71 by fixing bolts 53. The rising portion 52A includes a first vertical plate portion 52a that is provided so as to extend upward from one end of the base portion 51.

[0036] In this modification, the rising portion 52A is provided with a level adjustment mechanism 55 at the upper end of the first vertical plate portion 52a. The level adjustment mechanism 55 in this modification includes a first horizontal plate portion 55a, a second vertical plate portion 55b, a second horizontal plate portion 55c, and a height adjustment bolt 55d. The first horizontal plate portion 55a is provided so as to extend outwardly, on the opposite side to the foundation member 3, from the upper end of the first vertical plate portion 52a. The second vertical plate portion 55b is provided above the first vertical plate portion 52a at a distance from the first vertical plate portion 52a. The second vertical plate portion 55b and the first vertical plate portion 52a are provided so as to extend in the same plane. The second horizontal plate portion 55c is provided so as to extend from the lower end of the second vertical plate portion 55b toward the outside, on the opposite side to the foundation member 3. The second horizontal plate portion 55c is provided above the first horizontal plate portion 55a at a distance from the first horizontal plate portion 55a and parallel to the first horizontal plate portion 55a. The second horizontal plate portion 55c has a bolt hole (not shown). A height adjustment bolt 55d is screwed into and inserted into the bolt hole from above to below the second horizontal plate portion 55c. The lower end of the height adjustment bolt 55d abuts against the upper surface of the first horizontal plate portion 55a. The second vertical plate portion 55b has a bolt hole (not shown). A bolt 58 is inserted through this bolt hole from the outside toward the outer peripheral side surface 33 of the foundation member 3 and tightened, thereby fixing the rising portion 52A to the outer peripheral side surface 33. In other words, the foundation member 3 is supported by the level adjustment steel material 5A by tightening the bolt 58 through the bolt hole of the second vertical plate portion 55b.

[0037] In this way, the rising portion 52A is provided so as to entirely fit along the lower outer peripheral side surface 33a of the outer peripheral side surface 33. In other words, the base member 3 is positioned so that the outer peripheral side surface 33 fits along (the first vertical plate portion 52a and the second vertical plate portion 55b of) the rising portion 52A of the level adjusting steel material 5A. The rising portion 52A having the above-described structure can be manufactured, for example, by forming the base 51, the first vertical plate portion 52a, and the first horizontal plate portion 55a using a channel steel, and forming the second vertical plate portion 55b and the second horizontal plate portion 55c using an L-shaped steel.

[0038] In such a configuration, by rotating the height adjustment bolt 55d, the height of the second horizontal plate portion 55c relative to the first horizontal plate portion 55a, the height of the second vertical plate portion 55b which is immovable relative to the second horizontal plate portion 55c, and the base member 3 can be adjusted as desired in the vertical direction. That is, in this modified example, when the foundation member 3 is supported by the level adjustment steel material 5A, the level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3 comprises a first horizontal plate portion 55a, a second horizontal plate portion 55c arranged above the first horizontal plate portion 55a and spaced apart from the first horizontal plate portion 55a, a second vertical plate portion 55b arranged to rise upward from one end of the second horizontal plate portion 55c, and a height adjustment bolt 55d screwed and inserted from above to below through the bolt hole of the second horizontal plate portion 55c so that its lower end abuts against the upper surface of the first horizontal plate portion 55a. In this manner, the outer peripheral side surface 33 of the base member 3 is fixed to the rising portion 52A via the level adjustment mechanism 55 as described above.

[0039] In this modification, in step S2 of installing the level adjustment steel materials 5 after step S1 of driving the foundation piles 2 into the ground G as shown in FIG. 3, a plurality of level adjustment steel materials 5A are installed at a predetermined position on the sacrificial concrete layer 71. More specifically, only the channel steel parts forming the base 51, the first vertical plate part 52a, and the first horizontal plate part 55a of the level adjustment steel material 5A are installed on the sacrificial concrete layer 71. Each of the plurality of level adjustment steel materials 5A is installed so that the base 51 is aligned with the surface of the sacrificial concrete layer 71 and the rising part 52A (the first vertical plate part 52a) extends upward from the base 51. Each of the plurality of level adjustment steel materials 5A is installed so that the outer peripheral side surface 33 of the foundation member 3 is aligned with the level adjustment steel material 5A when the foundation member 3 is later installed at the planned position. Thereafter, the base 51 is fixed to the sacrificial concrete layer 71 by the fixing bolts 53. Additionally, the L-shaped steel forming the second vertical plate portion 55b and the second horizontal plate portion 55c are joined in advance to the outer peripheral side surface 33 of the foundation member 3 with bolts 58, and the height adjustment bolt 55d is screwed and inserted into the bolt hole of the second horizontal plate portion 55c from above to below the second horizontal plate portion 55c.

[0040] Next, in process S3 of supporting the foundation member 3 with the level-adjusting steel material 5A, the foundation member 3 is lifted by a crane or the like and moved upward away from the pile head 2h of the foundation pile 2 so that the outer peripheral side surface 33 is aligned with the first vertical plate portion 52a of the level-adjusting steel material 5A and so that the first horizontal plate portion 55a and the second horizontal plate portion 55c face each other and are spaced apart in the vertical direction. Thereafter, the base member 3 is lowered until the lower end of the height adjustment bolt 55d abuts against the upper surface of the first horizontal plate portion 55a, and the base member 3 is supported at its outer circumferential side surface 33 by the height adjustment bolt 55d. In this state, the height position of the foundation member 3 relative to the first horizontal plate portion 55a is adjusted in the vertical direction based on the design value by appropriately rotating the height adjustment bolt 55d. In this way, the foundation member 3 is supported at its outer circumferential side surface 33 by the rising portion 52A of the level adjustment steel material 5A via the level adjustment mechanism 55 while its height is adjusted. Thereafter, as described as step S4 of forming the bottom concrete portion 4 in the above embodiment, the bottom concrete portion 4 is formed.

[0041] It goes without saying that this modified example also provides the same effects as the above embodiment.

[0042] Second embodiment Next, a pile foundation structure according to a second embodiment of the present invention will be described. In this embodiment, only the parts that are different from the first embodiment will be described, and the description of the same structure will be omitted. FIG. 10 is a cross-sectional view showing a pile foundation structure according to a second embodiment of the present invention. In the above-described first embodiment, the pile head cap 6 is placed on the pile head 2h of the foundation pile 2, and the bottom concrete portion 4 is formed between the pile head cap 6 and the foundation member 3. Instead, in the present embodiment, the pile head cap 6 is not provided. In this embodiment, as shown in FIG. 10, the bottom concrete portion 4 is configured to be in direct contact with the pile head 2h of the foundation pile 2, and no gap D is formed on the side surface 2s of the pile head 2h. The construction method of the pile foundation structure 1 in this embodiment is generally the same as that described using Figure 3 in the first embodiment above, except that in step S1 of driving the foundation pile 2 into the ground G, the pile head cap 6 is not placed on the pile head 2h of the foundation pile 2.

[0043] The pile foundation structure 1 as described above, like the first embodiment, is a pile foundation structure 1 including a foundation pile 2 and a precast concrete foundation member 3 provided on the foundation pile 2, and includes a level adjustment steel material 5 including a base 51 installed in a basin concrete layer 71 on the ground G around the pile head 2h of the foundation pile 2, and a rising portion 52 extending upward from the base 51 and provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3, the foundation member 3 is positioned above the pile head 2h of the foundation pile 2 and the outer peripheral side surface 33 (lower outer peripheral side surface 33a) is aligned with the rising portion 52 of the level adjustment steel material 5, the outer peripheral side surface 33 of the foundation member is fixed to the rising portion 52 via the level adjustment mechanism 55, and a cement-based material is filled between the pile head 2h and the foundation member 3 to form a bottom concrete portion 4. With this configuration, as in the first embodiment described above, a pile foundation structure 1 can be provided in which the height of the precast concrete foundation member 3 can be easily adjusted when installing it on the foundation pile 2.

[0044] The construction method of the pile foundation structure 1 as described above is, like the first embodiment, a construction method of the pile foundation structure 1 including the foundation pile 2 and the precast concrete foundation member 3 provided on the foundation pile 2, and includes a step S1 of driving the foundation pile 2 into the ground G and causing the pile head 2h of the foundation pile 2 to protrude upward from the ground G, and a step S2 of driving a level adjustment steel material 5 including a base 51 and a rising portion 52 provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3, so that the base 51 is placed in the throw-out concrete on the ground G. The method includes a step S2 of installing the level adjustment steel material 5 on the cement layer 71 so that the rising portion 52 extends upward from the base 51; a step S3 of positioning the foundation member 3 at a distance above the pile head 2h of the foundation pile 2 and supporting the foundation member 3 on its outer peripheral side surface 33 (lower outer peripheral side surface 33a) along the rising portion 52 of the level adjustment steel material 5 while adjusting its height position via a level adjustment mechanism 55; and a step S4 of filling a cement-based material between the pile head 2h of the foundation pile 2 and the underside 31 of the foundation member 3 to form a bottom concrete portion 4. According to such a configuration, as in the above-described first embodiment, when the precast concrete foundation member 3 is provided on the foundation pile 2, the height of the foundation member 3 can be easily adjusted.

[0045] (Other variations) In addition, in each of the above-described embodiments, the level adjustment steel material 5 is provided on the sacrificial concrete layer 71. However, the present invention is not limited to this. The level adjustment steel material 5 may be placed on the surface Gf1 of the ground G. That is, the pile foundation structure 1 may be a pile foundation structure 1 comprising a foundation pile 2 and a precast concrete foundation member 3 placed on the foundation pile 2, and comprising a level adjustment steel material 5 having a base 51 installed on the ground G around the pile head 2h of the foundation pile 2, and a rising portion 52 extending upward from the base 51 and provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 and fixing the foundation member 3, the foundation member 3 is positioned above the pile head 2h of the foundation pile 2 and such that the outer peripheral side surface 33 (lower outer peripheral side surface 33a) is aligned with the rising portion 52 of the level adjustment steel material 5, the outer peripheral side surface 33 of the foundation member is fixed to the rising portion 52 via the level adjustment mechanism 55, and a cement-based material is filled between the pile head 2h and the foundation member 3 to form a bottom concrete portion 4. The method for constructing the pile foundation structure 1 includes a foundation pile 2 and a precast concrete foundation member 3 provided on the foundation pile 2, and includes a step S1 of driving the foundation pile 2 into the ground G and causing the pile head 2h of the foundation pile 2 to protrude upward from the ground G, and a step S2 of driving a level adjustment steel material 5 having a base 51 and a rising portion 52 provided with a level adjustment mechanism 55 for adjusting the height position of the foundation member 3 to fix the foundation member 3, the step S1 being located on the ground G and the rising portion 52 being located on the ground G. the level adjustment steel material 5 extends upward from the base 51; a step S3 of positioning the foundation member 3 at a distance above the pile head 2h of the foundation pile 2 and supporting the foundation member 3 on its outer peripheral side surface 33 (lower outer peripheral side surface 33a) along the rising portion 52 of the level adjustment steel material 5 while adjusting its height position via a level adjustment mechanism 55; and a step S4 of filling a cement-based material between the pile head 2h of the foundation pile 2 and the underside 31 of the foundation member 3 to form a bottom concrete portion 4.

[0046] In addition, in the above embodiment, the base plate 81 is provided on the upper surface of the foundation member 3, and the laminated rubber bearing 100 is arranged on the base plate, but it is also possible that the pillar material is provided from the foundation member 3 without providing the base plate 81 and the laminated rubber bearing 100. Alternatively, it is also possible that the laminated rubber bearing 100 is provided directly on the upper surface of the foundation member 3, without providing a base plate on the upper surface of the foundation member 3.

[0047] In addition, the configurations described in the above embodiments can be selected or changed as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0048] 1 Pile foundation structure 55 Level adjustment mechanism 2 Foundation pile 55A long hole 2h Pile head 58 bolts 2s Side 71 Concrete layer 3 Foundation member G Ground 33 Outer periphery side D Gap 33a Lower outer peripheral side (outer peripheral side) 4 Bottom concrete section S1 The process of driving foundation piles into the ground 5. 5A Level adjustment steel material S2 Process of installing level adjustment steel material 6 Pile cap S3 Process of supporting foundation members with level adjustment steel materials 51 Base S4 Process of forming bottom concrete part 52, 52A Rising part

Claims

1. A pile foundation structure comprising a foundation pile and a precast concrete foundation member provided on the foundation pile, A level adjustment steel material is provided, the level adjustment steel material having a base portion installed on the ground around the head portion of the foundation pile or on a basing concrete layer on the ground, and a rising portion extending upward from the base portion and provided with a level adjustment mechanism for adjusting the height position of the foundation member and fixing the foundation member, The foundation member is positioned so as to be spaced upward from the pile head of the foundation pile and so that the outer peripheral side surface is along the rising portion of the level adjustment steel material, and the outer peripheral side surface of the foundation member is fixed to the rising portion via the level adjustment mechanism, A pile foundation structure, characterized in that a cement-based material is filled between the pile head and the foundation member to form a bottom concrete portion.

2. The pile foundation structure described in claim 1, characterized in that the level adjustment mechanism is a long hole extending in the vertical direction formed in the rising portion, and a bolt is fastened to the outer peripheral side of the foundation member through the long hole of the level adjustment steel material.

3. The pile head of the foundation pile is covered with a pile head cap to form a gap on the side of the pile head, 3. The pile foundation structure according to claim 1, wherein the bottom concrete portion is formed between the pile head cap and the foundation member.

4. A method for constructing a pile foundation structure comprising a foundation pile and a precast concrete foundation member provided on the foundation pile, A step of driving the foundation pile into the ground and causing a pile head of the foundation pile to protrude upward from the ground; a step of installing a level adjustment steel material having a base and a rising portion provided with a level adjustment mechanism for adjusting the height position of the foundation member and fixing the foundation member, such that the base is located on the ground or a basing concrete layer on the ground, and the rising portion extends upward from the base; A step of positioning the foundation member at a distance above the pile head of the foundation pile, and supporting the foundation member on the outer peripheral side surface thereof along the rising portion of the level adjustment steel material while adjusting the height position via the level adjustment mechanism; A method for constructing a pile foundation structure, comprising the steps of: filling a cement-based material between the pile head of the foundation pile and the underside of the foundation member to form a bottom concrete portion.

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