Cast-in-place concrete pile construction method

Abstract

To provide a method for constructing a cast-in-place concrete pile, capable of constructing a high-quality cast-in-place concrete pile at low cost. [Solution] A construction method for a cast-in-place concrete pile in which the set fill height is above the construction ground, the construction method for a cast-in-place concrete pile comprising the steps of: a casing erection process in which a casing is erected into the construction ground; a hole drilling process in which a pile hole for the cast-in-place concrete pile is drilled into the casing; a reinforcing cage erection process in which a reinforcing cage is erected into the pile hole; an outer periphery cap installation process in which an outer periphery cap that surrounds the outer periphery of the casing is installed on the construction ground; a concrete pouring process in which concrete is poured into the casing up to at least the set fill height; a casing extraction process in which the casing is pulled out of the construction ground and the outer periphery cap receives the concrete that has spread from inside the casing onto the construction ground; and a vacuum treatment process in which the concrete inside the outer periphery cap is vacuum treated.

Description

[Technical field]

[0001] The present invention relates to a method for constructing a cast-in-place concrete pile, and more particularly to a method for constructing a cast-in-place concrete pile in which the set reinforcement height is above the construction ground. [Background technology]

[0002] 2. Description of the Related Art Cast-in-place concrete piles made of reinforced concrete have traditionally been used as foundations for buildings. A cast-in-place concrete pile is formed by drilling a pile hole while injecting a stabilizing fluid to protect the hole wall, erecting a reinforcing bar into the pile hole, and then pouring concrete into the pile hole. At this time, since impurities such as dirt and debris are mixed in the upper part of the poured concrete, it is common to first pour extra concrete above the top of the pile head to form a surplus part, and then remove the surplus part by chipping, as a pile head treatment.

[0003] When the top of a cast-in-place concrete pile is close to the construction ground, the reinforcement will be higher than the construction ground. In such cases, it is possible to apply the construction methods described in Patent Documents 1 and 2 as a construction method for the pile head of a cast-in-place concrete pile. The construction method of Patent Document 1 involves placing formwork for the pile head and excess reinforcement of a cast-in-place concrete pile inside a casing, and pouring concrete into the formwork. The construction method of Patent Document 2 involves placing a reinforcement formwork on top of a cast-in-place concrete pile, driving a standpipe with a larger diameter than the reinforcement formwork into the construction ground, and allowing concrete to overflow from the reinforcement formwork into the standpipe. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-34396 A [Patent Document 2] JP 2007-224657 A Summary of the Invention [Problem to be solved by the invention]

[0005] The formwork in Patent Document 1 is made up of a sheet of wire mesh or resin to prevent concrete from flowing out, a support part made of deformed steel bars, a reinforcing frame, etc. For this reason, creating the formwork requires a lot of work, such as welding and wire fixing. In addition, when creating the formwork on-site, a separate yard is required for this purpose. And because the removal of the formwork is done after the roots have been cut off and the excess reinforcement is to be chipped away, it cannot be reused at the same site. Also, since it is unclear to what extent the shape will be maintained after removal, it may not be possible to use it at another site. In addition, it seems likely that the work of chipping and removing the formwork will be required, but there is no clear description of these tasks.

[0006] The reinforcement formwork in the construction method of Patent Document 2 is made using two semi-cylindrical steel plates, but since it is not reinforced, there is a possibility that it may not be able to withstand the lateral pressure of the concrete. In addition, by driving standpipes into the construction ground around the periphery of the extra bank formwork, it is possible to prevent the collapse of the ground and to prevent the stabilizing liquid used in the pile holes when digging them from overflowing to the outside, but driving in the standpipes requires heavy machinery, which takes time and effort.In addition, removing the standpipes also requires heavy machinery, which takes time and effort. And, like the method of Patent Document 1, the excess reinforcement formwork is removed when the excess reinforcement is chipped off after the roots are cut, so it cannot be reused at the same site. Also, since it is unclear to what extent the shape will be maintained after removal, it may not be possible to use it at another site. In addition, it seems likely that the work of chipping and removing the formwork will be required, but there is no clear description of these tasks.

[0007] An object of the present invention is to provide a method for constructing a cast-in-place concrete pile, which can construct a high-quality cast-in-place concrete pile at low cost. [Means for solving the problem]

[0008] The present invention is a method for constructing a cast-in-place concrete pile with a set fill height above the construction ground, comprising: a casing erection process for erecting a casing into the construction ground; a hole drilling process for drilling pile holes for the cast-in-place concrete pile within the casing; a reinforcing cage erection process for erecting a reinforcing cage into the pile hole; an outer periphery cap installation process for installing an outer periphery cap surrounding the outer periphery of the casing on the construction ground; a concrete pouring process for pouring concrete into the casing up to at least the set fill height; a casing extraction process for pulling the casing out of the construction ground and using the outer periphery cap to receive the concrete spreading from within the casing onto the construction ground; and a vacuum treatment process for vacuuming the concrete inside the outer periphery cap. The outer circumferential cap may be a cylindrical body assembled with liner plates. During the casing extraction process, when the height of the lower end of the casing and the height of the top of the pile head are the same, the height of the concrete inside the casing may be measured to determine the actual fill height, or the height of the concrete received by the outer cap may be measured to determine the actual fill height. In addition, when the above-mentioned cast-in-place concrete pile construction method is repeated to construct two or more cast-in-place concrete piles, in the casing removal process when constructing the first cast-in-place concrete pile, the amount of concrete that falls within the casing when the casing is removed is measured, and in the concrete pouring process when constructing the second or subsequent cast-in-place concrete piles, the concrete is poured higher than the set excess fill height by the measured amount of concrete drop. Effect of the Invention

[0009] The present invention provides at least one of the following effects by solving the above-mentioned problems. (1) The concrete to be poured is contained within the casing, preventing loss of concrete due to overflow. (2) Since an excess reinforcement is secured within the casing protruding from the construction ground, even in the case of a cast-in-place concrete pile whose top end is close to the construction ground, it is possible to reliably prevent impurities from being mixed into the pile head. (3) The outer cap holds the concrete in place, preventing it from leaking out. (4) The amount of concrete poured from the second pile onwards can be adjusted based on the actual amount of concrete drop in the first pile, making it possible to pour an amount of concrete that will result in an appropriate reinforcement height. (5) Since the amount of concrete can be adjusted to the appropriate level, there is no need to pour concrete unnecessarily, and the amount of waste concrete, so-called leftover concrete and returned concrete, can be reduced. In addition, there is no need to prepare agitator trucks unnecessarily, and exhaust gases emitted by the movement of agitator trucks are also reduced. (6) After the vacuum treatment process, the outer cap can be moved, so that the outer cap can be reused and there is no need to reassemble the outer cap. (7) The outer cap can be made simply by combining liner plates and welding hanging hooks, which keeps material costs down and makes it easy to make. [Brief description of the drawings]

[0010] [Figure 1] An explanatory diagram of a cast-in-place concrete pile to which the present invention is applied. [Diagram 2] An explanatory diagram of the construction method of the cast-in-place concrete pile of the present invention. [Diagram 3] Diagram of outer cap [Figure 4] Diagram of the process for constructing cast-in-place concrete piles (1) [Diagram 5] Diagram of the process for constructing cast-in-place concrete piles (2) [Figure 6] Diagram of the process for constructing cast-in-place concrete piles (3) [Figure 7]Schematic diagram of concrete height during casing extraction process [Figure 8] Diagram of the process for constructing cast-in-place concrete piles (4) [Figure 9] An explanatory diagram of the steps of the construction method for cast-in-place concrete piles according to the second embodiment [Figure 10] Schematic diagram of concrete height during casing extraction process in Example 2 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the construction method for a cast-in-place concrete pile of the present invention will be described in detail with reference to the drawings.

[0012] [Example 1] (1) Overview of the construction method for cast-in-place concrete piles A cast-in-place concrete pile 1 to which the cast-in-place concrete pile construction method of the present invention is applied has a pile head top 11 close to the construction ground G, and the upper end of the reinforcement portion 2 set from the pile head top 11 is above the construction ground G (Fig. 1). In this embodiment, the height from the pile head top 11 to the construction ground G is 160 mm. The construction method of the cast-in-place concrete pile of the present invention involves installing a cylindrical outer cap 4 surrounding the outer periphery of a casing (surface casing) 3 that has conventionally been used when constructing a cast-in-place concrete pile 1 on the construction ground G (Figure 2).

[0013] (2) Outer cap In this embodiment, the thickness of the casing 3 is 22 mm, the outer diameter is 2200 mm (inner diameter 2156 mm), and the protruding height from the construction ground G is 1500 mm. The outer cap 4 has a thickness of 25 mm, an outer diameter of 3000 mm (inner diameter of 2950 mm), and a height of 1000 mm. However, these dimensions are not limited and can be changed appropriately according to the outer diameter of the casing 3 and the amount of concrete to be filled in the excess concrete portion 2, which will be described later. The outer periphery cap 4 is preferably made of a plurality of liner plates 41, which are widely used as construction materials, assembled into a cylindrical shape (FIG. 3). However, the outer periphery cap 4 is not limited to this, and may be a steel formwork or a wooden formwork.

[0014] (3) Construction process for cast-in-place concrete piles Next, a method for constructing a cast-in-place concrete pile of the present invention will be described with reference to Figs.

[0015] (3.1) Casing installation process A casing 3 is erected in the construction ground G where the cast-in-place concrete pile 1 is to be formed, by a conventional method (FIG. 4(a)).

[0016] (3.2) Drilling process, steel cage installation process A pile hole 5 for a cast-in-place concrete pile 1 is drilled in the casing 3. Then, a reinforcing bar cage 6 is erected in the pile hole 5 (FIG. 4(b)). Both drilling of the pile hole 5 and erection of the reinforcing bar cage 6 are performed by conventional methods.

[0017] (3.3) Outer cap installation process An outer periphery cap 4 surrounding the outer periphery of the casing 3 is placed on the construction ground G (FIG. 5(c)). When the outer periphery cap 4 is formed by combining liner plates 41, they are preassembled and the lifting hooks (not shown) are fixed by welding or the like, and then transported and installed using a lifting machine or the like used for erecting the reinforcing bar cage 6. All that is required is to combine the liner plates 41 and weld the lifting hooks, which keeps material costs down and makes production easy. The outer periphery cap 4 has sandbags 42 placed around the periphery to prevent it from shifting.

[0018] (3.4) Concrete pouring process Concrete 12 is poured into the pile holes 5 in the casing 3 (FIG. 5(d)). The concrete 12 is poured into the casing 3 up to a preset fill height 21 (800 mm from the pile top 11 in this embodiment) which is set to a predetermined height from the pile head top 11 of the cast-in-place concrete pile 1. Since the poured concrete 12 is contained within the casing 3, loss of the concrete 12 due to overflow can be prevented.

[0019] (3.5) Casing removal process After the concrete 12 is poured, the casing 3 is pulled out from the construction ground G. If the height of the concrete 12 inside the casing 3 is equal to the set reinforcement height 21 when the bottom end 31 of the casing 3 reaches the top end 11 of the pile head (Figure 6(e)) as the casing 3 is pulled out, the reinforcement portion 2 has been secured according to the standard. If the height of the concrete 12 inside the casing 3 decreases when the casing 3 is pulled out, more concrete 12 is poured in the previous concrete pouring process, taking into account the amount of decrease. Since the excess reinforcement portion 2 is secured within the casing 3 protruding from the construction ground G, even in the case of a cast-in-place concrete pile 1 whose pile head top end 11 is close to the construction ground G, it is possible to reliably prevent impurities from being mixed into the pile head. Then, when the casing 3 is further pulled out and the lower end 31 comes out of the construction ground G, the concrete 12 spreads out over the construction ground G and is received by the inner peripheral surface of the outer peripheral cap 4 that was placed on the outer periphery of the casing 3, and the concrete 12 is filled inside the outer peripheral cap 4 (FIG. 6(f)). By receiving the concrete 12 with the outer peripheral cap 4, it will not flow out.

[0020] (3.5.1) Beam height As described above, when the bottom end 31 of the casing 3 reaches the pile head top 11, if the height of the concrete 12 inside the casing 3 is the set reinforcement height 21, the reinforcement portion 2 has been secured. This can be confirmed by measuring the height of the concrete 12 inside the casing 3 when the position of the bottom end 31 of the casing 3 and the height of the pile head top 11 are aligned, and possible methods include measuring the height of the concrete 12 with a laser rangefinder or the like attached to the top end of the casing 3, or by providing a scale for the set reinforcement height 21 inside the casing 3 in advance and checking from the top end of the casing 3 with a camera or the like. On the other hand, by pulling out the casing 3 and measuring the height of the concrete 12 that has spread and been filled inside the outer cap 4, the excess fill height inside the casing 3 can be calculated.

[0021] 7(i) is a schematic diagram of the state in which the lower end 31 of the casing 3 is located at the pile head top 11 during the casing extraction process. If the excess fill height at this time is h1, the height from the pile head top 11 to the construction ground G is d, and the internal cross-sectional area of ​​the casing 3 is S1, then the volume V1 of the concrete 12 filled in the casing 3 above the construction ground G is S1 × (h1 - d). Fig. 7(ii) is a schematic diagram of the state in which the casing 3 is pulled out from the construction ground G, the concrete 12 in the casing 3 spreads over the construction ground G, and the concrete 12 is filled into the outer cap 4. If the height of the concrete 12 at this time is h2 and the inner cross-sectional area of ​​the outer cap 4 is S2, then the volume V2 of the concrete 12 above the construction ground G is S2 × h2. And, since this volume V2 is equal to the volume V1 of the concrete 12 filled above the construction ground G in the casing 3 in Fig. 7(i), the following formula 1 holds. [Formula 1] V1 = S1 × (h1-d) = V2 = S2 × h2 Then, by measuring the height h2 of the concrete 12 that has spread and been filled inside the outer cap 4, as shown in formula 1 and formula 2, the excess fill height h1 can be calculated from the height d from the top of the pile head 11 to the construction ground G, the inner cross-sectional area S1 of the casing 3, and the inner cross-sectional area S2 of the outer cap 4. [Formula 2] h1=(S1×d+S2×h2) / S1

[0022] In this embodiment, since the set reinforcement height 21 is 800 mm, it is required that h1 ≥ 800. In other words, it is sufficient that the following formula 3 is satisfied from formula 2. [Formula 3] (S1×d+S2×h2) / S1≧800mm In this embodiment, the height d from the top end 11 of the pile head to the construction ground G is 160 mm, and the inner cross-sectional area S1 of the casing 3 is π×(2156 / 2). 2 , the inner cross-sectional area S2 of the outer cap 4 = π × (2950 / 2) 2 Therefore, by substituting these into Equation 3 and performing calculations, we obtain Equation 4 below. [Formula 4] h2≧(S1×800-S1×d) / S2=341.8mm From the above, in this embodiment, if the height of the concrete 12 that has spread and been filled inside the outer cap 4 is 341.8 mm or more, the excess reinforcement portion 2 is secured.

[0023] (3.6) Vacuum treatment process Finally, the concrete 12 inside the outer cap 4 is vacuumed (Figure 8). By performing the vacuum treatment inside the outer cap 4 instead of above the pile hole 5, there is no risk of the concrete 12 being sucked out below the top end 11 of the pile head. After the vacuum treatment process, the outer perimeter cap 4 can be moved, so that when the next cast-in-place concrete pile 1 is formed on-site, the outer perimeter cap 4 can be reused and there is no need to assemble the outer perimeter cap 4 again.

[0024] (3.7) Amount of concrete poured for the second and subsequent runs When forming the first cast-in-place concrete pile 1 at a work site, if a larger amount of concrete 12 is poured into the casing 3 taking into account the amount of sagging of the concrete 12 when the casing 3 is removed, the actual amount of sagging of the concrete 12 when the casing 3 is removed can be calculated from the height of the concrete 12 that has spread and filled inside the outer cap 4, combined with the excess height inside the casing 3 when the first cast-in-place concrete pile 1 is formed. Therefore, from the second run onwards, the amount of concrete 12 poured can be adjusted based on the actual drop in the first run, and the amount of concrete 12 poured can be adjusted to achieve an appropriate excess height. This eliminates the need to pour concrete 12 unnecessarily, reducing the amount of so-called leftover concrete and returned concrete that becomes waste. In addition, it is no longer necessary to prepare agitator trucks unnecessarily, and the exhaust gas emitted by the movement of agitator trucks is also reduced.

[0025] [Example 2] In the above-described embodiment, the pile head top 11 is below the construction ground G, but the present invention can also be applied when the pile head top 11 is above the construction ground G (FIG. 9). In this embodiment, the pile head top 11 is above the construction ground G, and its height is set to 100 mm. Also, since the pile head top 11 is above the construction ground G, a cylindrical pile head formwork 7 is provided around the casing 3 to ensure the height of the pile head top 11 when the casing 3 is pulled out of the construction ground G. Fig. 10(i) is a schematic diagram of the state in which the bottom end 31 of the casing 3 is located at the pile head top 11 during the casing pulling out process. If the excess bank height is h1, the height (100 mm) from the construction ground G to the pile head top 11 is h3, and the internal cross-sectional area of ​​the casing 3 (calculated assuming the internal cross-sectional area of ​​the pile head formwork 7 to be the same) is S1, then the volume V1 of the concrete 12 filled above the construction ground G in the casing 3 and pile head formwork 7 is S1 × (h1 + h3). Fig. 10(ii) is a schematic diagram of the state in which the casing 3 is pulled out from the construction ground G, the concrete 12 in the casing 3 overflows from the pile head formwork 7, spreads over the construction ground G, and fills the outer periphery cap 4. If the height of the concrete 12 at this time is h2, the inner cross-sectional area of ​​the outer periphery cap 4 is S2, and the volume of the pile head formwork 7 is V3, then the volume V2 of the concrete 12 above the construction ground G is S2 x h2 - V3 (the volume of the pile head formwork 7 is omitted). This volume V2 is equal to the volume V1 of the concrete 12 filled above the construction ground G in the casing 3 in Fig. 10(i), so the following formula 5 holds. [Formula 5] V1=S1×(h1+h3)=V2=S2×h2-V3 Then, by measuring the height h2 of the concrete 12 that has spread and been filled inside the outer cap 4, as shown in equation 5 and equation 6, the excess fill height h1 can be calculated from the height h3 from the construction ground G to the top of the pile head 11, the inner cross-sectional area S1 of the casing 3, and the inner cross-sectional area S2 of the outer cap 4. [Formula 6] h1=(S2×h2-S1×h3-V3) / S1

[0026] In this embodiment as well, since the set reinforcement height 21 is 800 mm, it is required that h1 ≥ 800. That is, it is only necessary that the following formula 7 is satisfied from formula 6. [Formula 7] (S2×h2-S1×h3-V3) / S1≧800mm In this embodiment, the height h3 from the construction ground G to the top end 11 of the pile head is 100 mm, and the inner cross-sectional area S1 of the casing 3 is π×(2156 / 2). 2 , the inner cross-sectional area S2 of the outer cap 4 = π × (2950 / 2) 2 Therefore, by substituting these into Equation 7 and performing calculations, the following Equation 8 is obtained. [Formula 8] h2≧(S1×800+S1×h3-V3) / S2=480.7mm+V3 / S2 Here, if the volume V3 of the pile head formwork 7 is very small compared with the inner cross-sectional area S2 of the outer cap 4, and the value of V3 / S2 is small enough not to affect the calculation results, then if the height of the concrete 12 spread and filled inside the outer cap 4 is 480.7 mm or more, the excess reinforcement 2 will be secured. In addition, if the volume V3 increases due to reinforcing the pile head formwork 7, the height h2 shall be calculated including V3 / S2. [Explanation of symbols]

[0027] 1 Cast-in-place concrete pile, 11 Pile head, 12 Concrete 2 Reinforcement part, 21 Set reinforcement height 3 casing, 31 lower end 4 Outer perimeter cap, 41 Liner plate, 42 Sandbag 5. Pilehole 6 Reinforced Concrete Cage 7 Pile head formwork

Claims

1. A method for constructing cast-in-place concrete piles in which the set reinforcement height is above the construction ground, a casing erection process for erecting a casing in the construction ground; A drilling step of drilling a pile hole for the cast-in-place concrete pile in the casing; A reinforcing bar cage erection process for erecting a reinforcing bar cage into the pile hole; an outer periphery cap installation process for installing an outer periphery cap surrounding the outer periphery of the casing on the construction ground; A concrete pouring step of pouring concrete into the casing up to at least the set excess fill height; a casing extraction process for extracting the casing from the construction ground and receiving the concrete spreading from inside the casing onto the construction ground with the outer circumferential cap; A vacuum treatment process for vacuuming the concrete at the top of the pile head in the outer circumferential cap. How to install cast-in-place concrete piles.

2. The outer circumferential cap is a cylindrical body made up of liner plates. A method for constructing a cast-in-place concrete pile according to claim 1.

3. In the casing extraction process, when the height of the lower end of the casing and the height of the top end of the pile head are the same, the height of the concrete in the casing is measured to obtain the excess height. A method for constructing a cast-in-place concrete pile according to claim 1.

4. In the casing pulling process, The height of the concrete received by the outer circumferential cap is measured to obtain the excess height. A method for constructing a cast-in-place concrete pile according to claim 1.

5. When the method for constructing a cast-in-place concrete pile according to any one of claims 1 to 4 is repeated to construct two or more cast-in-place concrete piles, In the casing extraction step when constructing the first cast-in-place concrete pile, the amount of concrete falling inside the casing when the casing is extracted is measured; In the concrete pouring process when constructing the second or subsequent cast-in-place concrete piles, the concrete is poured higher than the set excess pile height by the measured drop amount. How to install cast-in-place concrete piles.

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