Cast-in-place pile construction method

Abstract

To provide a construction method for a cast-in-place pile that can preferably prevent a pile main reinforcement protruded from an extra banking body from being damaged by contacting excavation heavy equipment when excavating a soil to expose the extra banking body.SOLUTION: A method has a pile construction process that constructs a cast-in-place pile 10 by placing a protective cover 3 encircling an outer peripheral side of a top 13 of a pile main reinforcement inside a surface layer casing 2, excavation processes (e) and (f) that pull off the surface layer casing 2, then excavate a soil G down to a bedding surface A to expose an extra banking body 12 while keeping the protective cover 3, and chipping removal processes (g) and (h) that pull off the protective cover 3 from a pile body 11 to remove chipping in the extra banking body 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for constructing cast-in-place piles. [Background technology]

[0002] Conventionally, when constructing a cast-in-place pile, concrete is poured into the pile hole, and the pile body and the pile fill formed on the top of the pile body are constructed. Since the concrete in the pile fill is lean, the pile is generally exposed by excavating the ground and then chipped away and removed. In addition, generally, after constructing the pile body and the pile fill, the pile hole is backfilled, and then the ground is excavated with an excavation machine to expose the pile fill from the ground.

[0003] Here, since the upper part of the pile main reinforcement protrudes above the pile body, when the ground is excavated to expose the pile body, if the bucket of an excavation heavy machine comes into contact with the pile main reinforcement protruding from the pile body, the pile main reinforcement may be damaged. As a measure to prevent such contact between the excavation heavy machine and the pile main reinforcement, for example, Patent Document 1 discloses a method in which the soil used to backfill the pile hole has a different soil quality, such as color and hardness, from the surrounding ground. This makes it possible to notify the operator of the excavation heavy machine of the presence of the pile main reinforcement by the change in soil quality during excavation work. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-165431 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 and other documents relies on the visual inspection of the excavation machine operator to detect the pile main reinforcement, and therefore, if soil changes are overlooked or misidentified, contact between the excavation machine and the pile main reinforcement may not be avoided.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a construction method for cast-in-place piles that can effectively prevent damage to the pile main reinforcement protruding from the pile body due to contact with an excavation machine when excavating the ground to expose the pile body. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the method for constructing a cast-in-place pile according to the present invention is to The first excavation is performed on the surface of the ground, and a surface casing is erected. A protective cover, which is a cylindrical member similar to the surface casing, is inserted inside the surface casing; The ground is excavated to a predetermined depth to create a pile hole, the pile hole is filled with a stabilizing liquid, and a reinforcing bar cage including a plurality of pile main reinforcements and pile ties arranged around the plurality of pile main reinforcements is erected in the pile hole, At this time, the outer periphery of the upper part of the plurality of pile main reinforcements is surrounded by the protective cover, and then, Concrete is poured into the pile hole, and the pile body and the pile reinforcement are constructed. The pile reinforcement is formed on the top of the pile body and then chipped and removed. of protrusion To make, Pile construction process; an excavation process for removing the surface casing, leaving the protective cover, and excavating the ground to a bedding surface so that at least a lower end of the pile is positioned above the bedding surface, and the protective cover is exposed above the bedding surface; A chipping and removal process of removing the protective cover from the pile body and chipping and removing the excess pile body; The present invention is characterized by having the following.

[0008] According to this aspect, a protective cover is placed inside the surface casing to surround the outer periphery of the upper part of the pile main reinforcement, and then the surface casing is removed, and the ground is excavated to the bedding surface while leaving the protective cover, to expose the pile main reinforcement. When the bucket of the excavation heavy machine approaches a position where there is a risk of contacting the pile main reinforcement, it always comes into contact with the protective cover before coming into contact with the pile main reinforcement. When the excavation heavy machine comes into contact with the protective cover, a reaction force generated in response to the contact is transmitted to the heavy machine side, so that the operator of the excavation heavy machine can be notified of the approach to the pile main reinforcement by using tactile information other than visual information. In addition, when the excavation heavy machine comes into contact with the protective cover, a contact sound that is clearly different from that of the soil is generated, so that the approach can be notified by sound information other than visual information. Tactile information and sound information can be detected even if the operator does not necessarily see the bucket, and the detection range can be expanded compared to visual information, so that the operator of the excavation heavy machine can detect the approach to the pile main reinforcement with higher sensitivity. Furthermore, by providing a protective cover between the excavation machine and the pile main reinforcement, the pile main reinforcement can be protected more reliably, and thus the pile main reinforcement protruding from the pile can be prevented from being damaged by contact with the excavation machine when the ground is excavated to expose the pile.

[0009] In another aspect of the method for constructing a cast-in-place pile according to the present invention, the protective cover is inserted inside the surface casing between erecting the surface casing and the secondary excavation.

[0010] According to this embodiment, after the installation of the surface casing is completed and the inside of the surface casing is excavated, the protective cover is inserted, eliminating the need to excavate new soil to install the protective cover or the trouble of pressing the protective cover directly against the soil, making it easier to place the protective cover.

[0011] In another aspect of the method for constructing a cast-in-place pile according to the present invention, the protective cover is erected integrally with the surface casing into the ground.

[0012] According to this aspect, the protective cover can be installed at the same time as the surface casing is erected, so that it is possible to omit the step of placing the protective cover on the inside of the surface casing, thereby reducing the labor and work time required for constructing the cast-in-place piles.

[0013] In another aspect of the method for constructing a cast-in-place pile according to the present invention, the outer peripheral surface of the protective cover or the inner peripheral surface of the surface casing is subjected to a slippery surface treatment.

[0014] According to this aspect, when the surface casing is removed while leaving the protective cover in place during the excavation process, the contact surface between the protective cover and the surface casing can be made slippery, making it easier to remove the surface casing.

[0015] In another aspect of the method for installing a cast-in-place pile according to the present invention, the protective cover is made of resin.

[0016] According to this aspect, since the protective cover is made of resin, even if the bucket of the excavation heavy equipment contacts it during the excavation process, the protective cover can absorb the impact force by, for example, deforming or breaking, so that the pile main reinforcement can be protected and the occurrence of failures such as damage to the excavation heavy equipment can be suppressed. In addition, since the protective cover can be made lighter than metal, it can be easily removed after the ground is excavated up to the bedding surface and the protective cover exposed above the bedding surface is removed. Effect of the Invention

[0017] As can be understood from the above explanation, according to the construction method for cast-in-place piles of the present invention, when the ground is excavated to expose the pile, damage to the main pile reinforcement protruding from the pile due to contact with the excavation machinery can be effectively prevented. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing the first to fourth steps of a method for constructing a cast-in-place pile according to an embodiment; [Diagram 2]Schematic diagram showing the fifth to eighth steps of the construction method for a cast-in-place pile according to an embodiment. [Diagram 3] FIG. 1 is a schematic diagram showing a modified example of a protective cover according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0020] A method for constructing a cast-in-place pile 10 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic diagram showing first to fourth steps of the method for constructing a cast-in-place pile 10 according to an embodiment. Fig. 2 is a schematic diagram showing fifth to eighth steps of the method for constructing a cast-in-place pile 10 according to an embodiment. Fig. 1 (a) to (d) show the first to fourth steps, respectively, and Fig. 2 (e) to (h) show the fifth to eighth steps, respectively.

[0021] First, in the first step (pile construction step) shown in Fig. 1(a), the surface layer of the ground G is first excavated to form a hole 1. The hole 1 is excavated, for example, to a depth position (shown by a dashed line in Fig. 1) that becomes the bedding surface A (see Fig. 2(h)). The hole 1 is formed with a diameter that allows the surface layer casing 2 to be inserted.

[0022] Next, in the second step (pile construction step) shown in FIG. 1(b), the surface layer casing 2 is inserted into the hole 1 as shown by the arrow X1, and the surface layer casing 2 is erected. The surface layer casing 2 is a cylindrical member, for example made of metal. The surface layer casing 2 is inserted into the hole 1 so that the axial direction of the cylindrical shape coincides with the axial direction of the hole 1, thereby forming a space on the axial side of the surface layer casing 2. The surface layer casing 2 is inserted into the bottom of the hole 1.

[0023] The order of the first step in Fig. 1(a) "primary excavation of the surface layer of the ground G" and the second step in Fig. 1(b) "installation of the surface casing 2" does not matter. That is, as in the example of Fig. 1, the surface layer of the ground G may be first excavated and then the surface casing 2 may be installed, or, as opposed to the example of Fig. 1, the surface layer of the ground G inside the surface casing 2 may be first excavated after the surface casing 2 is installed in the ground G.

[0024] Next, in the third step (pile construction step) shown in FIG. 1(c), the protective cover 3 is inserted inside the surface layer casing 2 as indicated by the arrow X2. The protective cover 3 is a tubular member like the surface layer casing 2, and its outer diameter is smaller than the inner diameter of the surface layer casing 2, so that it can be inserted inside the surface layer casing 2. The protective cover 3 is inserted to the bottom surface of the hole 1 like the surface layer casing 2, so that the protective cover 3 is inserted to a depth position that will ultimately become the bedding surface A. Unlike the surface layer casing 2, the protective cover 3 is preferably made of resin.

[0025] In addition, the protective cover 3 may be constructed so as to be integrally built into the ground G with the surface casing 2, that is, the second step in FIG. 1(b) and the third step in FIG. 1(c) may be simultaneously performed. In this case, it is preferable to form a flange portion at the lower end of the protective cover 3 so as to protrude radially outward. Since the lower end of the surface casing 2 inserted outside the protective cover 3 is caught by the flange portion, the surface casing 2 can be prevented from shifting downward from the lower end of the protective cover 3, and the surface casing 2 and the protective cover 3 can be easily built integrally, and the surface casing 2 and the protective cover 3 can be easily aligned in the depth direction after the building. Note that it is sufficient to at least prevent the surface casing 2 from shifting downward from the lower end of the protective cover 3, and it is not necessarily required to provide the flange portion over the entire circumferential direction of the protective cover 3. For example, a configuration may be used in which protrusions protruding radially outward are provided at predetermined angles in the circumferential direction.

[0026] Furthermore, even when the protective cover 3 is erected into the ground G integrally with the surface casing 2, the first step in Figure 1(a) may be carried out later, and after the surface casing 2 and the protective cover 3 are erected into the ground G, the surface of the ground G inside the protective cover 3 may be primarily excavated.

[0027] Next, in the fourth step (pile construction step) shown in FIG. 1(d), a cast-in-place pile 10 (hereinafter sometimes simply referred to as a "pile 10") is constructed. More specifically, a pile hole 4 is constructed by second excavation of the ground G to a predetermined depth. Next, the pile hole 4 is filled with stabilizing liquid, and a reinforcing bar cage including a plurality of pile main bars and pile tie bars arranged around the plurality of pile main bars is erected in the pile hole. Note that FIG. 1(d) shows only the upper part 13 of the pile main bar (hereinafter sometimes simply referred to as the "pile main bar 13"). Next, concrete is poured into the pile hole 4 to construct the cast-in-place pile 10. The cast-in-place pile 10 has a pile main body 11 and an extra pile body 12 formed on the upper part of the pile main body 11. The upper part 13 of the pile main bar protrudes above the extra pile body 12.

[0028] Next, in the fifth step (excavation step) shown in Fig. 2(e), the surface casing 2 is removed while leaving the protective cover 3 as indicated by the arrow X3. It is preferable that the outer peripheral surface of the protective cover 3 or the inner peripheral surface of the surface casing 2 is subjected to a slippery surface treatment such as Teflon (registered trademark). This makes the contact surface between the protective cover 3 and the surface casing 2 slippery in this step, which makes it easier to remove the surface casing 2.

[0029] Next, in the sixth step (excavation step) shown in FIG. 2(f), the protective cover 3 is left in place and the ground G is excavated up to the bedding surface A as shown by the arrow X4 so that at least the lower end of the pile body 12 is positioned above the bedding surface A and the protective cover 3 is exposed above the bedding surface A. A heavy excavator is mainly used to excavate the ground G in this step, but since the outer periphery of the pile main reinforcement 13 above the pile body 12 is covered with the protective cover 3 during excavation work, even if the bucket of the heavy excavator approaches close enough to come into contact with the pile main reinforcement 13, the protective cover 3 is always interposed between the bucket and the pile main reinforcement 13. Therefore, the protective cover 3 can protect the pile main reinforcement 13 and prevent contact between the bucket and the pile main reinforcement 13.

[0030] In addition, since the protective cover 3 is made of resin in this embodiment, even if the bucket of an excavation heavy machine contacts the protective cover 3 during the excavation process, the impact force can be absorbed by, for example, deforming or breaking the protective cover 3. This makes it possible to protect the pile main reinforcement 13 and to suppress the occurrence of failures such as breakage on the excavation heavy machine side.

[0031] Next, in the seventh step (chisel removal step) shown in Fig. 2(g), the protective cover 3 is removed from the pile 10 as indicated by the arrow X5. This causes the pile 12 and the pile main reinforcement 13 to be exposed above the bedding surface A. In addition, since the protective cover 3 is made of resin in this embodiment, it is possible to reduce the weight of the protective cover 3 compared to metal, and therefore it is possible to easily remove the protective cover 3 exposed above the bedding surface A after the ground G has been excavated to the bedding surface A.

[0032] 2(h), the excess pile 12 is chipped and removed from the pile 10. As a result, the pile body 11 is buried below the bedding surface A, and the upper portion 13 of the pile main reinforcement is protruded from the pile body 11 above the bedding surface A.

[0033] According to this embodiment, the protective cover 3 surrounding the outer periphery of the upper part 13 of the pile main reinforcement is placed inside the surface layer casing 2, and the pile 10 is constructed. The surface layer casing 2 is then removed, and the ground G is excavated up to the bedding surface A while leaving the protective cover 3, exposing the extra bank 12. When the bucket of the excavation heavy machine approaches a position where it may come into contact with the pile main reinforcement 13, it always comes into contact with the protective cover 3 before coming into contact with the pile main reinforcement 13. When the excavation heavy machine comes into contact with the protective cover 3, a reaction force generated in response to the contact is transmitted to the machine side, so that the operator of the excavation heavy machine can be notified of the approach to the pile main reinforcement 13 using tactile information other than visual information. In addition, when the excavation heavy machine comes into contact with the protective cover 3, a contact sound that is clearly different from that of the soil is generated, so that the approach to the pile main reinforcement 13 can also be notified by sound information other than visual information. Tactile information and sound information can be detected even if the operator does not necessarily see the bucket, and the detection range can be expanded compared to visual information, so that the operator of the excavation machine can detect the approach to the pile main reinforcement 13 with higher sensitivity. Furthermore, by interposing the protective cover 3 between the excavation machine and the pile main reinforcement 13, the pile main reinforcement 13 can be protected more reliably. This makes it possible to suitably prevent the pile main reinforcement 13 protruding from the pile body 12 from being damaged by contact with the excavation machine when the ground G is excavated to expose the pile body 12.

[0034] FIG. 3 is a schematic diagram showing a modified example of the protective cover according to the embodiment. In the above embodiment, the protective cover 3 is made of resin, but it may be made of other materials than resin as long as it can surround at least the outer periphery of the pile main reinforcement 13. For example, as shown in FIG. 3(a), a paper protective cover 31 may be used. In this case, it is preferable to use a material such as a paper tube base paper formed of multiple layers to increase durability, or a reinforced cardboard with multiple flutes. In addition, when using a paper protective cover 31, it is preferable to cover the outer periphery with a waterproof layer 32 such as a resin film or to waterproof the outer periphery in order to prevent weakening due to rainwater or groundwater when the protective cover 31 is installed in the hole 1 of the ground G.

[0035] In the above embodiment, the protective cover 3 is a cylindrical member similar to the surface casing 2, but a shape other than a cylinder may be used. For example, as shown in Fig. 3(b), a configuration may be used in which the outer peripheral surface of a cylinder is formed by curving in a wavy shape along the circumferential direction. In this configuration, if the thickness of the protective cover 3 itself increases, care must be taken to ensure that the inner surface of the protective cover 3 is not smaller than the designed cross section of the pile 10.

[0036] 3(c), a configuration may be used in which the protective cover 34 has an outer circumferential surface, for example, a mesh-like surface, and a part of the outer circumferential surface is inserted into the axial center side. With this configuration, the amount of material for forming the protective cover 34 can be reduced, and the protective cover 34 can be made lighter.

[0037] In addition, it is preferable to color the surface of the protective cover 3 with a color that is complementary or opposite to the color of the soil of the ground G (for example, "greenish blue" which is the opposite color of orange (the same hue as brown) on the color wheel). This makes it possible to visually clarify and distinguish the boundary between the protective cover 3 and the ground G more clearly when excavating the ground G to the bedding surface A while leaving the protective cover 3 in place in the sixth step shown in Fig. 2(f), and therefore makes it possible to more reliably notify the operator of the excavation heavy equipment that the bucket is approaching the pile main reinforcement 13.

[0038] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0039] 2. Surface casing 3 Protective cover 4. Pilehole 10 Cast-in-place piles 11 Pile body 12 Extra-heavy body 13 Upper part of pile main bar G. Ground A Floor mounting surface

Claims

1. A method for constructing cast-in-place piles, comprising the steps of: a pile construction process including a first excavation of the surface layer of the ground to erect a surface casing, a second excavation of the ground to a specified depth to create a pile hole, filling the pile hole with stabilizing liquid, erecting a reinforcing bar cage comprising a plurality of pile main reinforcements and pile ties arranged around the plurality of pile main reinforcements in the pile hole, surrounding the outer periphery of the upper part of the plurality of pile main reinforcements with the protective cover, pouring concrete into the pile hole to construct a pile body and an overfill formed on the upper part of the pile body and to be chipped and removed thereafter, and allowing the upper part of the pile main reinforcements to protrude above the overfill. an excavation process for removing the surface casing, leaving the protective cover, and excavating the ground to a bedding surface so that at least a lower end of the pile is positioned above the bedding surface, and the protective cover is exposed above the bedding surface; A chipping and removal process of removing the protective cover from the pile body and chipping and removing the excess pile body; A method for constructing a cast-in-place pile, comprising:

2. 2. The method for constructing a cast-in-place pile according to claim 1, further comprising inserting the protective cover inside the surface casing between erecting the surface casing and the secondary excavation.

3. 2. The method for constructing a cast-in-place pile according to claim 1, wherein the protective cover is erected integrally with the surface casing into the ground.

4. The method for constructing a cast-in-place pile according to any one of claims 1 to 3, characterized in that an outer peripheral surface of the protective cover or an inner peripheral surface of the surface casing is subjected to a slippery surface treatment.

5. 5. The method for constructing a cast-in-place pile according to claim 1, wherein the protective cover is made of resin or paper.

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