Newly constructed pile structure, and construction method

Abstract

To provide a newly constructed pile structure and a construction method that can reduce pile construction costs.SOLUTION: A newly constructed pile structure 10 comprises: a newly constructed pile 30 penetrating a backfilled ground 20 and an existing pressure-resistant plate 14 and not being in contact with a through hole 15 formed in the existing pressure-resistant plate 14; a backfill material 40 filled between the newly constructed pile 30 and the through hole 15 and having lower strength and rigidity than those of the backfilled ground 20; an enlarged-diameter head 34 provided at a pile head of the newly constructed pile 30 while being in contact with the backfilled ground 20; and a newly constructed pressure-resistant plate 50 supported by the enlarged-diameter head 34 and the backfilled ground 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a new pile structure and a construction method.

Background Art

[0002] Patent Document 1 below discloses a continuous construction method for demolishing an existing structure and constructing a new pile, which includes steps of pressing a first casing into the ground to a depth deeper than an existing underground structure and removing the existing underground structure inside the first casing; inserting a second casing inside the first casing and then pulling out the first casing; and constructing a cast-in-place pile in the ground with the second casing as a surface casing.

[0003] Patent Document 2 below discloses a pile forming method in which, when forming a pile penetrating an existing structure in the ground, a member used for forming the pile and having a buffer material attached thereto in advance is arranged in a hole continuous with the existing structure and the ground, and the buffer material is arranged at a position corresponding to the outside of the pile and at a height corresponding to the existing structure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the continuous construction method for demolishing an existing structure and constructing a new pile described in Patent Document 1, a cast-in-place pile is constructed in the ground with the second casing as a surface casing. Therefore, when the existing structure and the new pile are in close contact, a large pile stress may be generated, and the cost of the pile may increase.

[0006] In the method of forming a pile described in Patent Document 2, by using a buffer material, an increase in pile stress can be suppressed. However, it is necessary to attach the buffer material in advance to the members used for forming the pile and arrange it at a position corresponding to the outside of the pile. For this reason, it takes time and effort during construction, and the construction period and cost of pile construction increase.

[0007] In consideration of the above facts, an object of the present invention is to provide a new pile structure and a construction method that can avoid the close contact between an existing structure and a newly installed pile, reduce the pile stress, and reduce the construction period and cost of the pile.

Means for Solving the Problems

[0008] The newly installed pile structure according to the first aspect penetrates the backfill ground and the existing bearing plate, and is a newly installed pile in a non-contact state with the through hole formed in the existing bearing plate. A backfill material having a lower strength and lower rigidity than the backfill ground is filled between the newly installed pile and the through hole. An enlarged diameter head provided at the pile head of the newly installed pile in contact with the backfill ground, and a newly installed bearing plate supported by the enlarged diameter head and the backfill ground.

[0009] According to the newly installed pile structure described in the first aspect, since the enlarged diameter head is in contact with the backfill ground, the horizontal force due to the building inertia force during an earthquake can be efficiently transmitted to the backfill ground. Further, the newly installed pile is in a non-contact state with the through hole formed in the existing bearing plate, and a backfill material having a lower strength and lower rigidity than the backfill ground is filled between the newly installed pile and the through hole. Therefore, the horizontal ground spring around the newly installed pile can be reduced. As a result, it is not necessary to design a pile with a length that can withstand a large pile stress, and the cost of the pile can be reduced.

[0010] The newly installed pile structure according to the second aspect is the newly installed pile structure according to the first aspect, wherein the backfill ground satisfies the condition that the N value is 15 or more, or the uniaxial compressive strength qu is 300 kN / m 2 or more.

[0011] According to the newly installed pile structure described in the second aspect, the backfilled ground satisfies the condition that the N value is 15 or more, or the uniaxial compressive strength qu is 300 KN / m 2 or more. As a result, in a state where the enlarged diameter head is in contact with the backfilled ground, the horizontal force due to the building inertial force during an earthquake can be efficiently transmitted from the enlarged diameter head to the backfilled ground.

[0012] The construction method described in the third aspect includes a backfilling step of filling the inside of the existing structure with backfilling material to form backfilled ground, an excavation step of forming an excavation hole that penetrates the existing pressure-resistant plate from the backfilled ground, a filling step of filling the inside of the excavation hole with a backfilling material having lower rigidity and strength than the backfilled ground, a newly installed pile construction step of constructing a newly installed pile smaller than the inner diameter of the excavation hole in the excavation hole filled with the backfilling material, an enlarged diameter head construction step of constructing an enlarged diameter head having a size that contacts the excavation hole formed in the backfilled ground at the pile head of the newly installed pile, and a pressure-resistant plate forming step of forming a newly installed pressure-resistant plate on the enlarged diameter head and the backfilled ground.

[0013] According to the construction method described in the third aspect, since the enlarged diameter head is in contact with the excavation hole formed in the backfilled ground, the horizontal force due to the building inertial force during an earthquake can be efficiently transmitted to the backfilled ground. Further, the newly installed pile is in a non-contact state with the through hole formed in the existing pressure-resistant plate, and a backfilling material having lower strength and rigidity than the backfilled ground is filled between the newly installed pile and the excavation hole, so that the horizontal ground spring around the newly installed pile can be reduced. As a result, it is not necessary to design a pile with a length that can withstand a large pile stress, and the cost of the pile can be reduced.

Effect of the Invention

[0014] According to the present disclosure, it is possible to avoid the adhesion between the existing structure and the newly installed pile, reduce the pile stress, and reduce the construction period of the pile construction and the cost of the pile.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2-1

Figure 2-2

Figure 2-3

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0016] Embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, those having low relevance to the present invention are omitted from illustration.

[0017] <First Embodiment> The new pile structure and construction method of the first embodiment will be described.

[0018] [New Pile Structure] In FIG. 1, the new pile structure 10 of the first embodiment is shown. As shown in FIG. 1, the new pile structure 10 includes a new pile 30 that penetrates the backfill ground 20 and the existing pressure-resistant plate 14, and a backfill material 40 filled between the new pile 30 and the through-hole 15 of the existing pressure-resistant plate 14. Further, the new pile structure 10 includes an enlarged diameter head 34 provided at the pile head of the new pile 30, and a new pressure-resistant plate 50 supported by the enlarged diameter head 34 and the backfill ground 20.

[0019] The existing pressure-resistant slab 14 forms part of the existing underground structure 12 provided inside the ground 100. As an example, the existing underground structure 12 includes the existing pressure-resistant slab 14 and the existing outer wall 16. The existing pressure-resistant slab 14 is provided horizontally along the lower part of the existing outer wall 16. The existing pressure-resistant slab 14 is part of the foundation that supports the load of the building with reinforced concrete. Although not shown in the figure, the existing underground structure 12 may have existing columns, beams, and walls.

[0020] A through-hole 15 is formed in the existing pressure-resistant slab 14, and the pile body 32 of the newly installed pile 30 described later penetrates through the through-hole 15. Although not shown in the figure, a plurality of through-holes 15 and newly installed piles 30 are provided.

[0021] By filling the inside of the existing underground structure 12 surrounded by the existing outer wall 16 and the existing pressure-resistant slab 14 with backfill soil 22, the backfilled ground 20 is formed. The backfill soil 22 is an example of a backfill material. In this embodiment, the inside of the existing underground structure 12 is filled with high-quality backfill soil 22 to form the backfilled ground 20. As an example, the backfill soil 22 is crushed gravel mixed with fragments such as concrete in the soil, and the backfilled ground 20 is formed by backfilling with the crushed gravel and performing rolling compaction. Also, instead of the crushed gravel, for example, fluidized treated soil with strength and rigidity (for example, uniaxial compressive strength is 400 kN / m 2 above 500 kN / m 2 below) can be used to backfill to form the backfilled ground 20.

[0022] The backfilled ground 20 preferably satisfies the condition that the N-value is 15 or more, or the uniaxial compressive strength qu is 300 kN / m 2 or more.

[0023] More specifically, the N-value of the backfilled ground 20 is preferably 15 or more and 50 or less.

[0024] More specifically, the uniaxial compressive strength qu of the backfilled ground 20 is preferably 300 kN / m 2 or more and 500 kN / m 2 or less.

[0025] Here, the N value is a numerical value that serves as an index for determining the compaction degree and strength of soil. The N value is obtained through a standard penetration test. The standard penetration test is a test in which a 63.5 kg weight attached to the tip of a measuring iron bar instrument is freely dropped from a height of 76 cm. The number of blows required to penetrate the sampler in the soil by 30 cm becomes the N value. The higher this numerical value, the more compact the soil is and it means that the ground can withstand heavy buildings.

[0026] The uniaxial compressive strength qu refers to the value indicating the compressive strength of the specimen, which is the maximum uniaxial compressive stress that a cylindrical specimen can withstand until it is destroyed. The uniaxial compressive strength qu is obtained through a uniaxial compression test. The uniaxial compression test is specified in JIS A 1216.

[0027] The new pile 30 includes a pile body 32 that constitutes from the lower side to the middle part in the axial direction, and an enlarged diameter head 34 provided at the pile head of the pile body 32. The pile body 32 and the enlarged diameter head 34 are integrally formed. The pile body 32 is constructed such that the lower end of the pile body 32 is located below the existing bearing plate 14 in the ground 100. As an example, reinforcing bars (not shown) are provided so as to straddle inside the pile body 32 and the enlarged diameter head 34. The position of the reinforcing bars may be outside the position of the enlarged diameter head 34 part compared to the position of the pile body 32 part.

[0028] The outer diameter of the pile body 32 is substantially equal in the axial direction (i.e., the vertical direction), and the outer diameter of the enlarged diameter head 34 is larger than the outer diameter of the pile body 32. The inner diameter of the through hole 15 of the existing bearing plate 14 is larger than the outer diameter of the pile body 32 of the new pile 30, and the pile body 32 of the new pile 30 and the through hole 15 are in a non-contact state.

[0029] In addition, an excavation hole 24 is formed in the backfill ground 20, and the inner diameter of the excavation hole 24 is substantially equal to the inner diameter of the through hole 15. Since the inner diameter of the excavation hole 24 is larger than the outer diameter of the pile body 32, the backfill ground 20 and the pile body 32 do not contact each other. The outer diameter of the diameter-expanded head 34 is substantially equal to or slightly smaller than the inner diameter of the excavation hole 24, and the diameter-expanded head 34 is in contact with the backfill ground 20.

[0030] The backfill material 40 is a material with lower strength and lower rigidity than the backfill ground 20. The backfill material 40 is filled between the pile body 32 of the newly installed pile 30 and the through hole 15 of the existing pressure-resistant disk 14. In addition, the backfill material 40 is continuously filled between the pile body 32 of the newly installed pile 30 and the backfill ground 20. The uniaxial compressive strength of the backfill material 40 is 2 200 kN / m 2 or less is preferable.

[0031] As an example, the backfill material 40 is a fluidized treated soil obtained by mixing cement into muddy water containing earth and sand and water. The backfill material 40 is liquid when filled between the pile body 32 of the newly installed pile 30 and the through hole 15 of the existing pressure-resistant disk 14, but hardens after a certain period of time.

[0032] The newly installed pressure-resistant disk 50 is formed on the diameter-expanded head 34 and the backfill ground 20. As an example, the newly installed pressure-resistant disk 50 is a part of a foundation or a floor slab that supports the load of a newly constructed building with reinforced concrete.

[0033] [Construction Method] Next, a construction method for constructing the newly installed pile structure 10 will be described.

[0034] As shown in Fig. 2-1(A), remove the new piles in the part surrounded by the existing outer wall 16 and the existing pressure-resistant plate 14 of the existing underground structure 12 and the existing structures that interfere with the construction thereof. Then, as shown in Fig. 2-1(B), fill the part surrounded by the existing outer wall 16 and the existing pressure-resistant plate 14 inside the existing underground structure 12 with backfill soil 22 to form a backfilled ground 20 (backfilling process). In the demolition work of the building having the existing underground structure 12, since the reduction in the mass of the building due to the demolition work may cause uplift, the inside of the existing underground structure 12 is filled with backfill soil 22.

[0035] Thereafter, as shown in Fig. 2-1(C), in order to partially demolish the existing pressure-resistant plate 14, use the full-rotation casing method to remove it together with a part of the backfilled ground 20. The full-rotation casing method refers to a method in which the casing 62 is rotationally pressed into the entire length of the excavation hole while cutting the backfilled ground 20, the existing pressure-resistant plate 14, and the ground 100 thereunder, and excavating and discharging the earth and sand etc. inside the casing 62. Thereby, an excavation hole 24 penetrating the existing pressure-resistant plate 14 from the backfilled ground 20, a through-hole 15, and an excavation hole 102 are formed (excavation process). The excavation hole 24 in the backfilled ground 20, the through-hole 15 in the existing pressure-resistant plate 14, and the excavation hole 102 in the ground 100 are formed continuously in the vertical direction and are an example of the excavation hole. At this time, for example, a casing 62 is used such that the inner diameter of the excavation hole 24 is larger in the range of 300 mm or more and 600 mm or less than the pile diameter of the pile body 32 of the new pile 30.

[0036] Thereafter, as shown in Fig. 2-2(D), fill the inside of the casing 62 with a backfill material 40 having lower rigidity and strength than the backfilled ground 20. As the backfill material 40, for example, a low-rigidity fluidized treatment soil obtained by mixing cement into muddy water containing earth and sand and water is used, and the uniaxial compression strength of the fluidized treatment soil is about 200 kN / m 2 degree. Then, as shown in Fig. 2-2(E), pull up the casing 62 before the backfill material 40 hardens. Thereby, the backfill material 40 is filled inside the excavation hole 24 in the backfilled ground 20, the through-hole 15 in the existing pressure-resistant plate 14, and the excavation hole 102 in the ground 100 (filling process). The backfill material 40 hardens after a certain period of time.

[0037] Subsequently, as shown in Fig. 2-2(F), the backfill material 40 and the ground 100 below the backfill material 40 are drilled to form a drilling hole 64. Then, the range to be the enlarged diameter head is drilled in accordance with the drilling hole 24. Note that the range to be the enlarged diameter head may be drilled first.

[0038]

[0037] Next, as shown in Fig. 2-3(G), the pile body 32 and the enlarged diameter head 34 of the new pile 30 are constructed. Thereby, in the drilling hole 24 of the backfilled ground 20 filled with the backfill material 40 and the through hole 15 of the existing pressure-resistant plate 14, the pile body 32 of the new pile 30 smaller than the inner diameters of the drilling hole 24 and the through hole 15 and the enlarged diameter head 34 substantially the same as the inner diameter of the drilling hole 24 are constructed (new pile construction process).

[0039] Thereafter, as shown in Fig. 2-3(H), the backfill soil 22 above the backfilled ground 20 is removed in accordance with the upper surface of the enlarged diameter head 34, and a new pressure-resistant plate 50 is formed on the enlarged diameter head 34 and the backfilled ground 20 (pressure-resistant plate forming process). Thereby, the construction of the new pile structure 10 is completed.

[0040] [Configuration and problems of the new pile structure of the first comparative example] Here, with reference to Fig. 5, the configuration and problems of the new pile structure 200 of the first comparative example will be described.

[0041]

[0038] As shown in Fig. 5, the new pile structure 200 includes an existing underground structure 212 having an existing pressure-resistant plate 214, a backfilled ground 220, a new pile 230, and a new pressure-resistant plate 250. The new pile structure 200 is provided such that the drilling hole 224 of the backfilled ground 220, the through hole 215 of the existing pressure-resistant plate 214, and the drilling hole 110 of the ground 100 are continuously provided in the vertical direction so as to penetrate the existing pressure-resistant plate 214 from the backfilled ground 220. The inner diameters of the drilling hole 224, the through hole 215, and the drilling hole 110 are substantially equal. A new pile 230 is constructed inside the drilling hole 224, the through hole 215, and the drilling hole 110. The outer diameter of the new pile 230 is substantially equal in the vertical direction.

[0042] A new bearing plate 250 is formed on the newly installed pile 230 and the backfill ground 220. The newly installed pile 230 is in contact with the existing bearing plate 214. Above the existing bearing plate 214, the newly installed pile 230 is in contact with the backfill ground 220.

[0043] In such a newly installed pile structure 200, since the existing bearing plate 214 restricts the rotation of the newly installed pile 230, large pile stresses are generated at two depths, namely, the pile head 230A of the newly installed pile 230 and the existing bearing plate 214, due to the horizontal force caused by the building inertial force during an earthquake (see the upper region 260 and the lower region 262 in Fig. 5). At this time, when the distance between the newly installed bearing plate 250 and the existing bearing plate 214 is large, the range of cross-sectional performance that can withstand the large pile stress expands. That is, the portion strengthening the newly installed pile 230 becomes larger. For this reason, there is a problem that the cost of the pile increases.

[0044] [Configuration and problems of the newly installed pile structure of the second comparative example] Next, with reference to Fig. 6, the configuration and problems of the newly installed pile structure 300 of the second comparative example will be described.

[0045] As shown in Fig. 6, the newly installed pile structure 300 includes an existing underground structure 312 having an existing bearing plate 314, a backfill ground 320, a newly installed pile 230, a backfill material 340, and a newly installed bearing plate 250. In the newly installed pile structure 300, a bored hole 324 in the backfill ground 320, a through hole 315 in the existing bearing plate 314, and a bored hole 112 in the ground 100 are continuously provided in the vertical direction so as to penetrate the existing bearing plate 314 from the backfill ground 320. The inner diameters of the bored hole 324, the through hole 315, and the bored hole 112 are substantially equal. Inside the bored hole 324, the through hole 315, and the bored hole 112, a newly installed pile 330 having an outer diameter smaller than the inner diameters of the bored hole 324, the through hole 315, and the bored hole 112 is constructed. The outer diameter of the newly installed pile 330 is substantially equal in the vertical direction. In other words, a through hole 315 larger than the outer diameter of the newly installed pile 330 is formed in the existing bearing plate 314.

[0046] Furthermore, between the newly installed pile 330, the excavation hole 324, the through hole 315, and the excavation hole 112, a backfill material 340 with lower strength and lower rigidity than the backfilled ground 320 is filled. A newly installed pressure-resistant plate 250 is formed on the newly installed pile 330, the backfill material 340, and the backfilled ground 320. The newly installed pile 230 does not contact the existing pressure-resistant plate 214 and the backfilled ground 220, but contacts the backfill material 340 filled inside the existing pressure-resistant plate 214 and the backfilled ground 220.

[0047] In the newly installed pile structure 300, the horizontal force of the pile head 330A of the newly installed pile 330 is made to flow into the surrounding ground 100. However, if the low-strength and low-rigidity backfill material 340 is filled up to the vicinity of the pile head 330A of the newly installed pile 330, the horizontal ground spring around the pile head 330A of the newly installed pile 330 decreases. The smaller the horizontal ground spring is, the greater the displacement required, and the pile stress increases considerably (see the upper region 360 in Fig. 6). For this reason, it is necessary to design the newly installed pile 330 that can withstand a large pile stress, and there is a problem that the cost of the pile increases.

[0048] [Actions and effects] Next, the actions and effects of the first embodiment will be described.

[0049] The newly installed pile structure 10 of the first embodiment includes a pile body 32 of a newly installed pile 30 that penetrates the backfilled ground 20 and the existing pressure-resistant plate 14 and is in a non-contact state with the through hole 15 formed in the existing pressure-resistant plate 14, and a backfill material 40 that is filled between the pile body 32 and the through hole 15 and has lower strength and lower rigidity than the backfilled ground 20. Furthermore, the newly installed pile structure 10 includes an enlarged diameter head 34 provided at the pile head of the newly installed pile 30 in a state of contacting the backfilled ground 20, and a newly installed pressure-resistant plate 50 supported by the enlarged diameter head 34 and the backfilled ground 20.

[0050] In the newly installed pile structure 10, since the enlarged diameter head 34 is in contact with the backfill ground 20, the horizontal force due to the building inertial force during an earthquake can be efficiently transmitted to the backfill ground 20. Further, the pile body 32 of the newly installed pile 30 is in a non-contact state with the through hole 15 formed in the existing pressure-resistant plate 14, and between the pile body 32 of the newly installed pile 30 and the through hole 15, a backfill material 40 with lower strength and lower rigidity than the backfill ground 20 is filled, so that the horizontal ground spring around the pile body 32 of the newly installed pile 30 can be reduced. As a result, it is not necessary to design a pile with a length that can withstand a large pile stress, and the cost of the pile can be reduced.

[0051] Further, the backfill ground 20 satisfies the condition that the N value is 15 or more, or the uniaxial compressive strength qu is 300 kN / m 2 or more. For this reason, in the newly installed pile structure 10, with the enlarged diameter head 34 in contact with the backfill ground 20, the horizontal force due to the building inertial force during an earthquake can be efficiently transmitted from the enlarged diameter head 34 to the backfill ground 20.

[0052] Moreover, the construction method of the first embodiment includes a backfill step of filling the inside of the existing underground structure 12 with backfill soil 22 to form the backfill ground 20, and a drilling step of forming a drilling hole 24 and a through hole 15 that penetrate the existing pressure-resistant plate 14 from the backfill ground 20. Further, the construction method includes a filling step of filling the inside of the drilling hole 24 and the through hole 15 with a backfill material 40 having lower rigidity and strength than the backfill soil 22. Moreover, the construction method includes a newly installed pile construction step of constructing the pile body 32 of the newly installed pile 30, which is smaller than the inner diameters of the drilling hole 24 and the through hole 15, in the drilling hole 24 and the through hole 15 filled with the backfill material 40, and an enlarged diameter head construction step of constructing an enlarged diameter head 34 having a size that contacts the drilling hole 24 formed in the backfill ground 20 at the pile head of the pile body 32 of the newly installed pile 30. Furthermore, the construction method includes a pressure-resistant plate forming step of forming a newly installed pressure-resistant plate 50 on the enlarged diameter head 34 and the backfill ground 20.

[0053] In the above construction method, since the enlarged-diameter head 34 is in contact with the excavation hole 24 formed in the backfilled ground 20, the horizontal force due to the building inertial force during an earthquake can be efficiently transmitted to the backfilled ground 20. Further, the pile body 32 of the new pile 30 is in a non-contact state with the through-hole 15 formed in the existing bearing plate 14, and a backfill material 40 having a lower strength and rigidity than the backfilled ground 20 is filled between the pile body 32 of the new pile 30 and the through-hole 15. Therefore, the horizontal ground spring around the pile body 32 of the new pile 30 can be reduced. As a result, it is not necessary to design a pile having a length within a range that can withstand a large pile stress, and the cost of the pile can be reduced.

[0054] <Second Embodiment> Next, the new pile structure of the second embodiment will be described. For the same components as those in the first embodiment described above, the same reference numerals are given and the description thereof is omitted.

[0055] As shown in FIG. 3, the new pile structure 130 of the second embodiment includes a new pile 132 instead of the new pile 30 of the new pile structure 10 of the first embodiment. The new pile 132 has a straight pile 134. The straight pile 134 has substantially the same outer diameter in the vertical direction. The outer diameter of the straight pile 134 is smaller than the inner diameters of the through-hole 15 of the existing bearing plate 14 and the excavation hole 24 of the backfilled ground 20.

[0056] A steel pipe 136 is wound around the upper portion 134A of the straight pile 134. By placing concrete between the steel pipe 136 and the backfilled ground 20, an enlarged-diameter head 138 is constructed on the upper portion 134A of the straight pile 134. The other configurations of the new pile structure 130 of the second embodiment are the same as those of the new pile structure 10 of the first embodiment.

[0057] In the new pile structure 130 of the second embodiment, the same operations and effects can be obtained by the same configuration as that of the new pile structure 10 of the first embodiment.

[0058] For example, when the surrounding ground is in good condition, a newly installed pile made of reinforced concrete (for example, the newly installed pile 30 of the first embodiment) is adopted. However, when the ground is not sufficiently firm, deformation will increase, and a newly installed pile made of reinforced concrete may not be able to bear the pile stress. In this case, by winding a steel pipe 136 around the pile head portion where the pile stress in the straight pile 134 becomes large and placing concrete to construct the enlarged diameter head portion 138, it becomes possible to bear a large pile stress.

[0059] <Third Embodiment> Next, the newly installed pile structure of the third embodiment will be described. For the same components as those in the above-described first and second embodiments, the same numbers will be assigned and their descriptions will be omitted.

[0060] As shown in FIG. 4, the newly installed pile structure 150 of the third embodiment includes a newly installed pile 152 instead of the newly installed pile 30 of the newly installed pile structure 10 of the first embodiment. The newly installed pile 152 uses a precast concrete pile 154. The precast concrete pile 154 is a pile that is manufactured in a factory and transported to the site.

[0061] The outer diameter of the precast concrete pile 154 is smaller than the inner diameters of the through hole 15 of the existing pressure-resistant plate 14 and the excavation hole 24 of the backfill ground 20. The precast concrete pile 154 is arranged so as not to be in contact with the through hole 15 of the existing pressure-resistant plate 14 and the excavation hole 24 of the backfill ground 20, and the backfill material 40 is filled between the precast concrete pile 154 and the existing pressure-resistant plate 14 and the backfill ground 20. Further, a fixing liquid (for example, cement milk, etc.) is filled between the upper portion 154A of the precast concrete pile 154 above the backfill material 40 and the backfill ground 20 and hardened to construct the enlarged diameter head portion 156. Note that the other configurations of the newly installed pile structure 130 of the second embodiment are the same as those of the newly installed pile structure 10 of the first embodiment.

[0062] In the newly installed pile structure 130 of the second embodiment, the same operations and effects can be obtained with the same configuration as the newly installed pile structure 10 of the first embodiment.

[0063] Note that, as the precast concrete pile 154, an SC pile wrapped with a steel pipe may be used. By using an SC pile wrapped with a steel pipe, the length of the precast concrete pile 154 can be shortened or the thickness of the steel pipe can be reduced.

[0064] <Others> In addition, the present invention is not limited to the above first to third embodiments.

[0065] In the above first to third embodiments, the material constituting the backfill material 40 can be changed to other low-rigidity materials.

[0066] Furthermore, the present invention can be implemented in various modes without departing from the gist thereof.

Explanation of Reference Numerals

[0067] 10 New pile structure 14 Existing pressure-resistant disk 15 Through hole 20 Backfill ground 22 Backfill soil (backfill material) 24 Excavation hole 30 New pile 34 Enlarged diameter head 40 Backfill material 50 New pressure-resistant disk 130 New pile structure 132 New pile 138 Enlarged diameter head 150 New pile structure 152 New pile 156 Enlarged diameter head

Claims

1. A newly installed pile that penetrates the backfilled ground and the existing bearing plate and is in a non-contact state with the through-hole formed in the existing bearing plate, A backfill material that is filled between the newly installed pile and the through-hole and has lower strength and rigidity than the backfilled ground, An enlarged diameter head provided at the pile head of the newly installed pile in contact with the backfilled ground, The enlarged diameter head and a newly installed bearing plate supported by the backfilled ground, A newly installed pile structure having the above.

2. The newly installed pile structure according to claim 1, wherein the backfilled ground satisfies the condition that the N value is 15 or more, or the uniaxial compressive strength qu is 300 kN / m ２ or more.

3. A backfilling process of forming a backfilled ground by filling the inside of the existing structure with a backfilling material, An excavation process of forming an excavation hole that penetrates the existing bearing plate from the backfilled ground, A filling process of filling the inside of the excavation hole with a backfilling material having lower rigidity and strength than the backfilled ground, A newly installed pile construction process of constructing a newly installed pile smaller than the inner diameter of the excavation hole in the excavation hole filled with the backfilling material, An enlarged diameter head construction process of constructing an enlarged diameter head having a size that contacts the excavation hole formed in the backfilled ground at the pile head of the newly installed pile, A bearing plate forming process of forming a newly installed bearing plate on the enlarged diameter head and the backfilled ground, A construction method having the above.

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