Cast-in-place concrete piles and their construction methods

Abstract

To provide a cast-in-place concrete pile with a pile head capable of reliably securing the designed diameter of the pile head even when soil and water pressure is greater than the lateral pressure of the concrete, and a method for constructing the same. [Solution] This cast-in-place concrete pile 2 is provided with a diameter reduction prevention wall 6 that extends from the ground surface to a predetermined depth around the pile body 5, and the diameter reduction prevention wall 6 is formed from low-strength material 6a cast into an outer casing 9 placed outside the casing 7, and the low-strength material 6a has an adhesion strength that allows it to be torn off from the casing 7 and outer casing 9 with a predetermined force, and can maintain its shape even when subjected to the soil-water pressure of the ground 1 and the pressure of the concrete 5a cast into the casing 7, and has compressive strength that can withstand its own weight.

Description

[Technical Field]

[0001] The present invention relates to a cast-in-place concrete pile constructed by the so-called all-casing construction method and a method for constructing the same. [Background technology]

[0002] BACKGROUND ART Conventionally, the so-called all-casing construction method has been widely known as a construction method for constructing cast-in-place concrete piles used for the foundations of buildings and the like (see, for example, Patent Document 1).

[0003] In this all-casing method, first, the casing is rotated or swung to penetrate the ground to a predetermined depth, and then a hammer grab is used to excavate and remove the soil inside the casing to form a pile hole.

[0004] Next, once a pile hole of a predetermined depth has been formed, the necessary hole bottom treatment is carried out and a reinforcing bar cage is erected in the pile hole.

[0005] Then, while the casing is being pulled out, concrete is poured into the pile hole using a tremie pipe or the like, thereby constructing a reinforced concrete pile body in the ground.

[0006] In this case, the design outer diameter of the pile body (hereinafter referred to as the design diameter) is based on the outer diameter of the casing, and the internal pressure of the casing is controlled to be greater than the soil water pressure, allowing fresh concrete to flow up to the outer diameter of the casing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-156864 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the conventional technology as described above, the pressure exerted on the inner surface of the pile hole by the poured fresh concrete (hereinafter referred to as lateral pressure) is affected by the weight of the poured fresh concrete, and the lateral pressure is greater at the bottom of the pile hole and becomes smaller toward the top.

[0009] Therefore, with this type of cast-in-place concrete pile, the lateral pressure due to the fresh concrete decreases at the pile head, where the effect of the weight of the fresh concrete is less, and the pressure difference between the inside and outside of the casing becomes smaller, which could result in a problem where the pile head becomes smaller than the design diameter.

[0010] In particular, in soft ground, the earth pressure underground becomes greater than the lateral pressure of the poured fresh concrete, which poses a problem that the pile diameter at the pile head tends to become smaller than the designed pile diameter.

[0011] On the other hand, in order to address these issues, conventional measures have been taken, such as pouring extra concrete (overfilling) up to a position higher than the designed height of the pile head to increase the lateral pressure of the concrete, or placing a weight on the pile head after the concrete has been poured and increasing the lateral pressure of the concrete with the weight of the weight, but these measures have the problem of being insecure.

[0012] Therefore, in view of the above-mentioned conventional problems, the present invention has been made with the aim of providing a cast-in-place concrete pile with a pile head that can reliably ensure the designed diameter of the pile head even when the earth pressure is greater than the lateral pressure of the concrete, and a method for constructing the same. [Means for solving the problem]

[0013] The invention described in claim 1, which aims to solve the above-mentioned problems of the prior art, is characterized in that the cast-in-place concrete pile has a pile body formed by pouring concrete into a pile hole that is formed by drilling the inside of a casing that has penetrated the ground, while the casing is being pulled out, and the pile body is provided with a diameter reduction prevention wall that extends from the ground surface to a predetermined depth, and the diameter reduction prevention wall is formed from a low-strength material that has been cast into an outer casing that is placed outside the casing, and the low-strength material has an adhesive strength that allows it to be torn from the casing and the outer casing by a predetermined force, and can maintain its shape even when subjected to the soil-water pressure of the ground and the pressure of the concrete cast into the casing, and has a compressive strength that can withstand its own weight.

[0014] The invention described in claim 2 is characterized in that, in addition to the configuration of claim 1, the thickness of the diameter reduction prevention wall is 10% to 30% of the pile diameter of the pile body.

[0015] The invention described in claim 3 is characterized in that, in a method for constructing a cast-in-place concrete pile, the inside of a casing that has penetrated into the ground is excavated to form a pile hole, and the casing is pulled out while concrete is poured into the pile hole to form the pile body, the work of penetrating an outer casing that is larger in diameter than the casing into the ground, the work of excavating the inside of the outer casing and removing soil is repeated to a predetermined depth from the ground surface to form an outer pile hole, the casing is erected in the outer pile hole concentrically with the outer casing, and the casing is penetrated to a position slightly deeper than the bottom of the outer pile hole, and then low-strength material is poured into the gap between the casing and the outer casing to form a diameter reduction prevention wall, and then the casing is separated from the diameter reduction prevention wall, and the work of penetrating the casing, the work of excavating the inside of the casing and removing soil is repeated to form the pile hole, and the casing is pulled out while concrete is poured into the pile hole to form the pile body.

[0016] The feature of the invention described in claim 4 is that, in addition to the configuration of claim 3, the low-strength material has an adhesive strength sufficient to be torn off from the casing and the outer casing with a predetermined force, can maintain its shape even when subjected to the soil-water pressure of the ground and the pressure of the concrete poured inside the casing, and has compressive strength sufficient to withstand its own weight.

[0017] The invention described in claim 5 is characterized in that, in addition to the configuration of claim 3 or 4, the diameter reduction prevention wall is formed and the outer casing is pulled out before the casing is separated from the diameter reduction prevention wall.

[0018] The invention as set forth in claim 6 is characterized in that, in addition to the configuration of claim 3 or 4, the casing is penetrated to a predetermined depth into the ground while being rotated.

[0019] The invention as set forth in claim 7 is characterized in that, in addition to the configuration of claim 3 or 4, a release material is provided on the outer peripheral surface of the casing and / or the inner peripheral surface of the outer casing.

[0020] The feature of the invention described in claim 8 is that, in addition to the configuration of claim 7, the peeling material is made of a sealing material, and the sealing material is provided only on the outer surface of the casing and / or the inner surface of the outer casing in a portion that does not penetrate into the ground.

[0021] The invention as set forth in claim 9 is characterized in that, in addition to the configuration of claim 3 or 4, the pipe diameter ratio of the casing to the outer casing is 1.2 or more and 1.6 or less. [Effects of the Invention]

[0022] By being equipped with the configuration described in claim 1, the cast-in-place concrete pile of the present invention can block surrounding earth pressure with a diameter reduction prevention wall, prevent the concrete at the pile head from being subjected to earth pressure, and reliably ensure the designed diameter at the pile head of the pile body.

[0023] Furthermore, in the present invention, by providing the configuration described in claim 2, it is possible to form a diameter reduction prevention wall that can separate the casing and the outer casing and that has sufficient strength.

[0024] The method for constructing a cast-in-place concrete pile according to the present invention is provided with the configuration described in claim 3, thereby blocking the surrounding earth pressure with a diameter reduction prevention wall, preventing the concrete at the head of the cast-in-place concrete pile from being subjected to earth pressure, and ensuring that the designed diameter is maintained at the head of the pile body.

[0025] Furthermore, in the present invention, by providing the configuration described in claim 4, it is possible to form a diameter reduction prevention wall that can separate the casing and the outer casing and that has sufficient strength.

[0026] Furthermore, in the present invention, by providing the configuration described in claim 5, the outside of the diameter reduction prevention wall can be integrated with the ground before the casing is cut off. Also, the outer casing can be reused.

[0027] Furthermore, in the present invention, by providing the configuration described in claim 6, the concentricity between the casing and the outer casing can be improved.

[0028] In the present invention, by providing the configurations set forth in claims 7 and 8, it is possible to easily separate the diameter reduction prevention wall from the casing and the outer casing.

[0029] In the present invention, by providing the configuration described in claim 9, it is possible to make the pile diameter ratio between the pile body and the diameter reduction prevention wall appropriate. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a vertical cross-sectional view showing an example of a cast-in-place concrete pile according to the present invention. FIG. [Figure 2] This is an enlarged cross-sectional view of the pile head portion. [Figure 3]1 is a schematic enlarged longitudinal cross-sectional view showing the state of each step of the method for constructing a cast-in-place concrete pile according to the present invention, in which (a) shows the state in which the outer casing has been erected on the ground surface, (b) shows the state in which the outer casing has been inserted, (c) shows the state in which the casing has been erected into the outer pile hole and the tip has been inserted to a predetermined depth, and (d) shows the state in which low-strength material has been poured. [Figure 4] FIG. 4 is an enlarged cross-sectional view showing the state in which the casing and the outer casing shown in FIG. 3(d) are installed. [Figure 5] 1 is a schematic enlarged longitudinal cross-sectional view showing the state of each step of the above-mentioned process, in which (e) shows the state when the outer casing is being pulled out, (f) shows the state when the casing has been penetrated to a predetermined depth, (g) shows the state when concrete is being poured while the casing is being pulled out, and (h) shows the state when the cast-in-place concrete pile has been constructed. DETAILED DESCRIPTION OF THE INVENTION

[0031] Next, an embodiment of the cast-in-place concrete pile according to the present invention will be described based on the examples shown in Figures 1 and 2. In the figures, reference numeral 1 denotes the ground, and reference numeral 2 denotes the cast-in-place concrete pile.

[0032] In this embodiment, as shown in Figure 1, an example of ground 1 will be described in which soft ground 4 (clay soil: N value ≦ 2, sandy soil: N value ≦ 6) is layered to a certain depth on normal ground 3.

[0033] As shown in Figures 1 and 2, this cast-in-place concrete pile 2 comprises a reinforced concrete pile body 5 that extends to a predetermined depth in the ground 1, and a diameter reduction prevention wall 6 that extends from the ground surface to a predetermined depth around the pile body 5. The diameter reduction prevention wall 6 prevents the earth pressure of the ground 1 (soft ground 4) from acting directly on the head of the pile body 5, thereby preventing it from affecting the lateral pressure of the concrete.

[0034] The pile body 5 is formed of concrete 5a that is poured into a pile hole 8 formed by drilling the inside of a casing 7 that has penetrated into the ground 1, while the casing 7 is being pulled out.

[0035] Although not specifically shown, a reinforcing bar cage is placed inside the pile hole 8, and the pile body 5 is made of reinforced concrete.

[0036] The diameter reduction prevention wall 6 is formed by casting low-strength material 6a into an outer casing 9 arranged outside the casing 7, and the low-strength material 6a forms a cylindrical shape whose inner diameter is the same as the outer diameter (design diameter D) of the pile main body 5.

[0037] The thickness of the diameter reduction prevention wall 6 is formed to be 10% to 30% of the pile diameter of the pile main body 5.

[0038] Furthermore, this diameter reduction prevention wall 6 is formed to have a height (depth) that can cover the head of the pile body 5, where the lateral pressure of the concrete decreases and the pressure difference between the inside and outside of the casing 7 becomes smaller, and it is particularly desirable that the wall has a height (depth) that can cover the entire area of ​​the soft ground 4 (clay soil: N≦2, sandy soil N≦6).

[0039] Furthermore, if the daily groundwater level fluctuation in the ground 1 where the cast-in-place concrete piles 2 are manufactured exceeds 1 m, if the soil layer has large gaps such as a rubble layer, or if the construction range (depth) of the diameter reduction prevention wall 6 exceeds GL-10 m, care must be taken as there is a risk of problems with the diameter reduction prevention wall 6.

[0040] The low-strength material 6a has an adhesive strength sufficient to be torn off from the casing 7 and the outer casing 9 with a predetermined force, and is capable of maintaining its shape even when subjected to the soil and water pressure of the ground 1 and the pressure of the concrete poured inside the casing 7, and is also configured to have a compressive strength sufficient to withstand its own weight.

[0041] The specific conditions for the low strength material 6a are as follows.

[0042] (1) In order for the outer casing 9 to have sufficient adhesion strength to be separated from the diameter reduction prevention wall 6 by a predetermined force, f2≦(Ta-f1×A1) / A2 The conditions of Ta: Force that pulls off the peripheral friction (kN) Ta=Ma / ra Ma: Force to rotate the outer casing 9 (rotational torque) (kNm) ra: Radius of outer casing 9 (m) f1: Friction force between the ground 1 and the outer casing 9 (kN / m 2 ) A1: Contact area between the ground 1 and the outer casing 9 (m 2 ) f2: Adhesion strength of low strength material 6a (kN / m 2 ) A2: Contact area between the low strength material 6a and the outer casing 9 (m 2 )

[0043] (2) In order for the casing 7 to have sufficient adhesion strength to be separated from the diameter reduction prevention wall 6 by a predetermined force, f2≦(Tb-f1×A1) / A2 The conditions of Tb: Force that pulls off the peripheral friction (kN) Tb=Mb / rb (5) Mb: Force to rotate the casing 7 (rotational torque) (kNm) rb: radius of casing 7 (m) f1: Friction force between the ground 1 and the casing 7 (kN / m 2 ) A1: Contact area between the ground 1 and the casing 7 (m 2 ) f2: Adhesion strength of low-strength material 6a (kN / m2) A2: Contact area between the low strength material 6a and the casing 7 (m 2 ) is.

[0044] (3) In order to maintain the shape even under the soil and water pressure of the ground 1 and the pressure of the concrete poured into the casing 7, M / z+N / A≦σca The conditions of M: Bending moment (kNm) N: Axial force (N) σca: Compressive strength of diameter reduction prevention wall 6 (low strength material 6a) z: Section modulus of diameter reduction prevention wall 6 (low strength material 6a) A: Cross-sectional area of ​​the diameter reduction prevention wall 6 (low strength material 6a) (m 2 ) is.

[0045] (4) In order to have compressive strength that can withstand its own weight, σca≧W×H The conditions of W: unit weight of low strength material 6a (kN / m 3 ) H: Height of the wall 6 (low-strength material 6a) (m) is.

[0046] Therefore, the low-strength material 6a is set so as to satisfy all of the above conditions (1) to (4). Note that, since the strength of the low-strength material 6a tends to increase over time, it is desirable to carry out a laboratory test in advance to understand the change in strength and to determine the timing of whether to perform the work of removing the outer casing 9 or the casing 7.

[0047] As the low-strength material 6a, for example, low-strength mortar, fluidized soil, low-strength grout, etc. can be used.

[0048] Next, a method for constructing the above-mentioned cast-in-place concrete pile 2 will be described based on the embodiment shown in Figures 3 to 5. Note that the same components as those in the above-mentioned embodiment will be described with the same reference numerals.

[0049] To construct this cast-in-place concrete pile 2, first, as shown in Figure 3(a), an outer casing 9 is erected on top of the ground 1, and then, as shown in Figure 3(b), the outer casing 9 is repeatedly penetrated from the ground surface and excavated inside the outer casing 9 with a hammer grab or the like, until the outer casing 9 is removed from the ground and penetrated to a predetermined depth into the ground 1.

[0050] In this case, it is desirable to provide a release material made of a sealant or paint on the inner surface of the outer casing 9 in advance.

[0051] When a release material made of a sealing material is used, it is preferable to provide the sealant only on the portion of the inner circumferential surface of the outer casing 9 that does not penetrate into the ground, and specifically, no release material is provided on a portion of the tip of the outer casing 9 that is several meters long, and only the portion without the release material penetrates into the original ground. When a release material made of paint is used, no release material is applied to a portion of the tip of the outer casing 9 that is several meters long, and only the portion without the release material penetrates into the original ground, or the entire surface may be coated with release material.

[0052] The outer casing 9 is composed of a steel pipe pile or the like equipped with a drilling blade (not shown) at the lower end, and has a larger diameter than the casing 7 used to form the pile body 5, with the pipe diameter ratio between the casing 7 and the outer casing 9 being 1.2 or more and 1.6 or less.

[0053] Below are examples of combinations of the main casing 7 diameter and outer casing 9 diameter.

[0054] [Table 1]

[0055] The means for penetrating the outer casing 9 into the ground 1 is not particularly limited, and may be a vibro hammer or the like, or a rotary or swinging casing penetration device may be used.

[0056] Furthermore, when the outer casing 9 is inserted, it is inserted while adjusting its position using surveying equipment etc. so that it is concentric with the pile main body 5, based on the design value of the pile main body 5.

[0057] It is to be noted that the predetermined depth to which the outer casing 9 penetrates is preferably set to a depth that reaches a position deeper than the bottom end position of the soft ground 4 when soft ground 4 exists near the ground surface.

[0058] Then, the outer casing 9 is penetrated to a predetermined depth, and excavation inside the outer casing 9 using a hammer grab or the like and dumping of soil from the outer casing 9 to the ground are repeated to a predetermined depth to form the outer pile hole 10.

[0059] Next, as shown in Figure 3(c), the casing 7 is erected concentrically with the outer casing 9 into the formed outer pile hole 10, and the casing 7 is inserted to a position y1 slightly deeper than the bottom of the outer pile hole 10. It is desirable to provide a release material made of a sealant or paint on the outer surface of the casing 7 in advance.

[0060] The method of penetrating the casing 7, like the outer casing 9, is not particularly limited, and it may be penetrated using a vibro hammer or the like, or a rotary or swinging casing penetration device may be used, but it is preferable to rotate the casing 7 while penetrating it to a predetermined depth into the ground 1 to ensure concentricity with the outer casing 9.

[0061] The penetration depth of the casing 7 is preferably set to a position y1 slightly deeper than the bottom surface of the outer pile hole 10, penetrating the soft ground 4 and reaching the upper layer of the normal ground 3.

[0062] Then, as shown in Figure 4, once the casing 7 and the outer casing 9 are installed in a double-pipe configuration, a low-strength material 6a is poured into the gap between the outer surface of the casing 7 and the inner surface of the outer casing 9 to form a diameter reduction prevention wall 6.

[0063] Then, as shown in Figure 5(e), after the low-strength material 6a has been cast, the outer casing 9 is pulled out approximately 3 to 4 hours later. The pulling out is carried out using a rotary casing penetration device to cut the adhesion to the low-strength material 6a. It is also desirable to determine the timing of the outer casing 9 removal based on the results of laboratory tests carried out in advance.

[0064] At this time, the adhesive strength is such that the outer casing 9 can be torn off with a predetermined force, and the outer casing 9 can be easily pulled out. Furthermore, by providing a release material on the inner peripheral surface of the outer casing 9, the outer casing 9 can be more easily pulled out.

[0065] After the low-strength material 6a is cast, as shown in Figure 5(f), the casing 7 is disconnected from the diameter reduction prevention wall 6 after about one day has passed, and penetrated to a predetermined depth y2 into the ground 1. It is desirable to determine the timing of disconnecting the casing 7 based on the results of laboratory tests conducted in advance.

[0066] At this point, the low-strength material 6a has an adhesion strength sufficient to separate the casing 7 from the diameter reduction prevention wall 6, and also exerts a compressive strength sufficient to prevent the shape of the diameter reduction prevention wall 6 from collapsing, so that the casing 7 can be easily separated from the diameter reduction prevention wall 6 and penetrated into the ground 1.

[0067] The method of inserting the casing 7 is not particularly limited, but it is preferable to insert the casing 7 while rotating it in order to smoothly separate it from the diameter reduction prevention wall 6.

[0068] Then, the work of inserting the casing 7 and the work of excavating the inside of the casing 7 using a hammer grab or the like are repeated, the soil and sand inside the casing 7 are removed to the ground, the casing 7 is inserted to a predetermined depth, and a pile hole 8 is formed.

[0069] Once the pile hole 8 has been formed, a bucket (not shown) is used to carry out hole bottom preparation such as removing slime from the hole 8, and then a reinforcing bar cage (not shown) made of reinforcing bars assembled in a cage shape is erected in the hole 8 after this hole bottom preparation has been completed.

[0070] Next, as shown in Figure 5(g), when a predetermined number of days (about 3 days) have passed since the low-strength material 6a was poured and the diameter reduction prevention wall 6 has reached a predetermined strength, a tremie pipe (not shown) is inserted into the pile hole 8, and concrete 5a is poured into the pile hole 8 while the casing 7 is being pulled out. The timing for pulling out the casing 7 should preferably be determined based on the results of a laboratory test carried out in advance.

[0071] Then, as the casing 7 is pulled out and the concrete pouring continues, the lower end of the casing 7 is pulled out to the depth of the diameter reduction prevention wall 6, and the concrete pouring height reaches the area surrounded by the diameter reduction prevention wall 6.

[0072] At this time, the lateral pressure of the concrete decreases at the height of concrete pouring, i.e., at the top of the poured concrete, because the weight of the concrete is light, but the earth pressure received from outside the diameter reduction prevention wall 6 is blocked by the diameter reduction prevention wall 6, and the poured concrete flows to the outer diameter part of the casing 7 after the casing 7 is pulled out, i.e., the inner surface of the diameter reduction prevention wall 6, and the pile head is formed to approximately the designed diameter D.

[0073] Furthermore, in order to increase the lateral pressure of the concrete and allow it to flow to the inner surface of the diameter reduction prevention wall 6, extra concrete may be poured (excess pile) to a position higher than the designed height of the pile head, or a weight may be placed on the pile head after the concrete is poured.

[0074] Then, the casing 7 is completely pulled out from the pile hole 8, and the pile body 5 with the pile head surrounded by the diameter reduction prevention wall 6 is formed in the pile hole 8 as shown in FIG. 5(h). [Explanation of symbols]

[0075] 1 ground 1 2. Cast-in-place concrete piles 3 Normal ground 4 Soft ground 5 Pile body 6 Diameter reduction prevention wall 7 Casing 8 Pileholes 9 Outer casing 10 Outer stake hole

Claims

1. A cast-in-place concrete pile in which a pile body is formed by pouring concrete into a pile hole formed by excavating the inside of a casing that has penetrated the ground while the casing is being pulled out, A diameter reduction prevention wall is provided around the pile body, extending from the ground surface to a predetermined depth, The diameter reduction prevention wall is formed by a low-strength material cast into an outer casing arranged outside the casing, The low-strength material has an adhesive strength sufficient to be torn off from the casing and the outer casing with a predetermined force, and is capable of maintaining its shape even when subjected to the soil and water pressure of the ground and the pressure of the concrete poured inside the casing, and is a cast-in-place concrete pile characterized by having compressive strength sufficient to withstand its own weight.

2. 2. The cast-in-place concrete pile according to claim 1, wherein the thickness of the diameter reduction prevention wall is 10% to 30% of the pile diameter of the pile body.

3. A method for constructing a cast-in-place concrete pile, in which a pile hole is formed by excavating the inside of a casing that has penetrated the ground, and concrete is poured into the pile hole while the casing is being pulled out to form a pile body, The work of penetrating an outer casing with a larger diameter than the casing into the ground, the work of excavating the inside of the outer casing and removing the soil are repeated to a predetermined depth from the ground surface to form an outer pile hole, the casing is erected in the outer pile hole concentrically with the outer casing, and the casing is penetrated to a position slightly deeper than the bottom of the outer pile hole, a low-strength material is cast into the gap between the casing and the outer casing to form a diameter reduction prevention wall; Thereafter, the casing is separated from the diameter reduction prevention wall, and the work of inserting the casing, excavating the inside of the casing, and removing soil is repeated to a predetermined depth in the ground to form the pile hole, A method for constructing a cast-in-place concrete pile, comprising: pouring concrete into the pile hole while removing the casing to form the pile body.

4. A method for constructing a cast-in-place concrete pile as described in claim 3, wherein the low-strength material has an adhesive strength sufficient to be torn off from the casing and the outer casing with a predetermined force, and is capable of maintaining its shape even when subjected to soil and water pressure from the ground and the pressure of the concrete poured into the casing, and has compressive strength sufficient to withstand its own weight.

5. 5. A method for constructing a cast-in-place concrete pile according to claim 3 or 4, wherein the outer casing is pulled out before the diameter reduction prevention wall is formed and the casing is separated from the diameter reduction prevention wall.

6. 5. A method for constructing a cast-in-place concrete pile according to claim 3 or 4, wherein the casing is driven into the ground to a predetermined depth while being rotated.

7. 5. A method for constructing a cast-in-place concrete pile according to claim 3 or 4, wherein a release material is provided on the outer peripheral surface of the casing and / or the inner peripheral surface of the outer casing.

8. A method for constructing a cast-in-place concrete pile as described in claim 7, wherein the release material is composed of a sealing material, and the sealing material is applied only to the outer surface of the casing and / or the inner surface of the outer casing in a portion that does not penetrate into the ground.

9. 5. The method for constructing a cast-in-place concrete pile according to claim 3 or 4, wherein the pipe diameter ratio between the casing and the outer casing is 1.2 or more and 1.6 or less.

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