Pile design method, and pile construction method

Abstract

To provide a pile design method capable of improving the construction accuracy of a new prefabricated pile when constructing a new prefabricated pile nearby an existing pile removal backfilling part formed by backfilling a drilled area after removing an existing pile.SOLUTION: A pile design method is configured to, when an overlap ratio L is outside the allowable range of an existing pile removal backfilling part 14 is formed by backfilling a drilled part 12 after removing an existing pile 10 and a new pile shaft drilled part 30 is formed in the ground G when a new prefabricated pile 20 is newly installed in a planned position, change at least one of the existing pile removal backfilling diameter D1 of the existing pile removal backfilling part 14 and the new pile shaft drilling diameter D2 of the new pile shaft drilling part 30 so that the overlap ratio L is within the allowable value.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

[0002] There is a ground improvement method of backfilling while improving the ground in the bored hole after removing an existing pile (see, for example, Patent Documents 1 and 2).

[0003] In addition, there is a construction method of constructing a cast-in-place concrete pile in the backfilled portion where the bored hole after removing the existing pile is backfilled (see, for example, Patent Document 3).

[0004] Furthermore, there are documents on constructing a new pile in the backfilled portion where the bored hole after removing the existing pile is backfilled (see Non-Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, it is conceivable to install a prefabricated pile (hereinafter referred to as "newly installed prefabricated pile") in a backfill area (hereinafter referred to as "existing pile removal and backfill section") that fills a drilling hole for removing an existing pile.

[0008] In the construction of a newly installed prefabricated pile, first, a drilling hole (hereinafter referred to as "newly installed pile shaft drilling hole") is formed in the ground, and the newly installed prefabricated pile is dropped into the formed newly installed pile shaft drilling hole in a state where a root fixing liquid, a pile circumference fixing liquid, etc. are injected.

[0009] Here, if there is an existing pile removal and backfill section in the construction area of the newly installed pile shaft drilling hole, the newly installed pile shaft drilling hole may bend due to the strength difference between the existing pile removal and backfill section and the original ground, etc., and the construction accuracy of the newly installed prefabricated pile may decrease.

[0010] In consideration of the above facts, the present invention aims to improve the construction accuracy of a newly installed prefabricated pile when constructing the newly installed prefabricated pile near an existing pile removal and backfill section formed by filling a drilling hole after removing an existing pile.

Means for Solving the Problems

[0011] The pile design method according to claim 1 is such that when the lap rate between the existing pile removal and backfill section formed by filling the drilling hole after removing the existing pile and the newly installed pile shaft drilling hole formed in the ground when installing the newly installed prefabricated pile at the planned position is outside the allowable value, at least one of the existing pile removal and backfill diameter of the existing pile removal and backfill section and the newly installed pile shaft drilling diameter of the newly installed pile shaft drilling hole is changed so that the lap rate becomes the allowable value.

[0012] According to the pile design method according to claim 1, when the lap rate between the existing pile removal and backfill part formed by filling back the bored hole after removal of the existing pile and the newly bored pile shaft part bored hole formed in the ground when installing a new precast pile at the planned position is outside the allowable value, the eccentricity of the newly bored pile shaft part bored hole may increase. As a result, the construction accuracy of the newly installed precast pile may decrease.

[0013] In contrast, in the present invention, when the lap rate between the existing pile removal and backfill part and the newly bored pile shaft part bored hole is outside the allowable value, at least one of the existing pile removal and backfill diameter of the existing pile removal and backfill part and the newly bored pile shaft part bored hole diameter of the newly bored pile shaft part bored hole is changed so that the lap rate becomes the allowable value. Thereby, the eccentricity of the newly bored pile shaft part bored hole is reduced. Therefore, the construction accuracy of the newly installed precast pile can be improved.

[0014] The pile design method according to claim 2 is the pile design method according to claim 1, wherein when reducing the newly bored pile shaft part bored hole diameter, the newly installed precast pile with a pile diameter that can be constructed in the newly bored pile shaft part bored hole is redesigned.

[0015] According to the pile design method according to claim 2, when reducing the newly bored pile shaft part bored hole diameter of the newly bored pile shaft part bored hole, the construction of the newly installed precast pile may become difficult.

[0016] Therefore, in the present invention, when reducing the newly bored pile shaft part bored hole diameter of the newly bored pile shaft part bored hole, the newly installed precast pile with a pile diameter that can be constructed in the newly bored pile shaft part bored hole is redesigned. Thereby, in the present invention, while improving the construction accuracy of the newly installed precast pile, the newly installed precast pile can be easily constructed.

[0017] The pile design method according to claim 3 is the pile design method according to claim 1 or claim 2, wherein the allowable value of the lap rate is set based on at least one of the allowable eccentricity of the newly installed precast pile and the allowable eccentricity of the boring rod for creating the newly bored pile shaft part bored hole.

[0018] According to the pile design method according to claim 3, the allowable value of the lap rate between the existing pile removal and backfilling portion and the newly installed pile shaft portion drilling portion is set based on at least one of the allowable eccentricity of the newly installed precast pile and the allowable eccentricity of the drilling rod for creating the newly installed pile shaft portion drilling portion. Thereby, since the eccentricity of the newly installed precast pile and the drilling rod is reduced, the construction accuracy of the newly installed precast pile can be improved.

[0019] The pile construction method according to claim 4 constructs the newly installed pile shaft portion drilling portion so that the lap rate between the existing pile removal and backfilling portion formed by backfilling the drilling portion after removal of the existing pile and the newly installed pile shaft portion drilling portion formed in the ground when installing the newly installed precast pile becomes an allowable value.

[0020] According to the pile construction method according to claim 4, when the lap rate between the existing pile removal and backfilling portion formed by backfilling the drilling portion after removal of the existing pile and the newly installed pile shaft portion drilling portion formed in the ground when installing the newly installed precast pile is outside the allowable value, the eccentricity of the newly installed pile shaft portion drilling portion may increase. As a result, the construction accuracy of the newly installed precast pile may decrease.

[0021] On the other hand, in the present invention, the newly installed pile shaft portion drilling portion is constructed so that the lap rate between the existing pile removal and backfilling portion and the newly installed pile shaft portion drilling portion becomes an allowable value. Thereby, the eccentricity of the newly installed pile shaft portion drilling portion is reduced. Therefore, the construction accuracy of the newly installed precast pile can be improved.

Effects of the Invention

[0022] As described above, according to the present invention, when constructing a newly installed precast pile in the vicinity of the existing pile removal and backfilling portion formed by backfilling the drilling portion after removal of the existing pile, the construction accuracy of the newly installed precast pile can be improved.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0024] Hereinafter, a pile design method according to an embodiment will be described with reference to the drawings.

[0025] (Pile Design Method) As shown in FIG. 1, the pile design method according to the present embodiment is used when there is an existing pile removal and backfilling portion 14 formed by backfilling a bored hole portion 12 for removing an existing pile 10 in a construction area of a bored hole portion 30 of a new pile shaft portion of a new precast pile 20.

[0026] (Existing Pile Removal and Backfilling Portion) As shown in FIGS. 1 and 2, the existing pile removal and backfilling portion 14 is a region where the bored hole portion 12 for removing the existing pile 10 is backfilled.

[0027] Note that the existing pile 10 may be a steel pipe pile or a concrete pile. Further, the existing pile 10 may be a prefabricated pile or a cast-in-place pile.

[0028] As a method for removing the existing pile 10, that is, a construction method for the existing pile removal and backfilling portion 14, for example, like the construction method disclosed in Patent Document 2 (hereinafter referred to as the "improved wheel throwing method"), first, a casing is driven around the existing pile 10 to form a bored portion 12, and the existing pile 10 inside the casing is pulled out by a crane. Next, an auger is inserted into the casing, and the tip of the auger is expanded below the lower end of the casing. Then, while pulling out the auger and the casing, the ground is stirred by the auger and cement milk is injected into the ground. Thereby, the existing pile removal and backfilling portion 14 of the existing pile 10 is backfilled with a predetermined strength.

[0029] Further, as another construction method for the existing pile removal and backfilling portion 14, for example, like the construction method disclosed in Patent Document 4 (hereinafter referred to as the "wheel throwing screw stirring method"), a casing is driven around the existing pile 10 to form a bored portion 12, and after pulling out the casing, the existing pile 10 is pulled out. Next, while inserting an auger having a diameter equal to or larger than that of the bored portion 12, the ground is stirred by the auger and cement milk or the like is injected into the ground. Thereby, the existing pile removal and backfilling portion 14 of the existing pile 10 is backfilled with a predetermined strength.

[0030] Here, it is desirable that the existing pile removal and backfilling portion 14 has a predetermined strength. This predetermined strength is set to be approximately equal to the strength of the original ground as an example. Further, the strength of the existing pile removal and backfilling portion 14 is evaluated by, for example, the N value or the uniaxial compressive strength.

[0031] Note that examples of the construction method capable of controlling the existing pile removal and backfilling portion 14 to a predetermined strength include the aforementioned improved wheel throwing method, the wheel throwing screw stirring method, the PG method, the CD method (full rotation all casing method), etc. On the other hand, an example of the construction method that makes it difficult to control the existing pile removal and backfilling portion 14 to a predetermined strength is the edge cutting and pulling out method.

[0032] (Newly installed prefabricated pile) The newly installed prefabricated pile 20 is made of steel piles (steel pipe piles) or concrete piles and is manufactured in factories or the like. The newly installed prefabricated pile 20 is constructed by the pre-boring method or the like. FIG. 3 shows, as an example, the newly installed prefabricated pile 20 constructed by the pre-boring and enlarged base consolidation method.

[0033] In the pre-boring and enlarged base consolidation method, first, a newly installed pile shaft boring part 30 is formed in the ground G by a boring rod 40 (see FIG. 5), and a newly installed pile base consolidation boring part 32 is formed at the lower end of the newly installed pile shaft boring part 30. Next, a consolidation liquid W2 is injected into the newly installed pile base consolidation boring part 32, and while pulling out the boring rod 40, a pile circumference fixing liquid W1 is injected into the newly installed pile shaft boring part 30. Next, the newly installed prefabricated pile 20 is dropped into the newly installed pile shaft boring part 30 and the newly installed pile base consolidation boring part 32. Thereby, the newly installed prefabricated pile 20 is constructed.

[0034] Note that the newly installed pile base consolidation boring part 32 may be provided as necessary and can be changed as appropriate.

[0035] Here, when constructing the newly installed prefabricated pile 20, for example, the eccentricity of the newly installed prefabricated pile 20 (newly installed pile shaft boring part 30) is managed. As shown in FIG. 4, the eccentricity R of the newly installed prefabricated pile 20 is represented by the displacement amount (deviation amount) of the planar position (x, y) of the center C1 of the newly installed prefabricated pile 20 with respect to the design center C0 of the newly installed prefabricated pile 20 and is obtained by the following formula (1). [Number]

[0036] The planar position (x, y) of the center C1 of the newly installed prefabricated pile 20 is measured, for example, by a light wave transit 42 or the like on the ground surface of the ground G in a state where the lower end of the boring rod 40 has reached the planned depth (boring lower end) after forming the newly installed pile shaft boring part 30 and the newly installed pile base consolidation boring part 32 by the boring rod 40 as shown in FIG. 5.

[0037] Note that the measurement timing and measurement method of the planar position (x, y) of the center C1 of the newly installed precast pile 20 can be changed as appropriate.

[0038] Here, the eccentricity R of the newly installed precast pile 20 varies depending on the lap rate between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 formed in the ground G when the newly installed precast pile 20 is installed at the planned position. This is presumably because the strength difference between the existing pile removal and backfilling portion 14 and the surrounding ground G makes the boring rod for creating the newly installed pile shaft boring portion 30 more likely to bend. Therefore, in the pile design method according to the present embodiment, first, the lap rate between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is calculated.

[0039] The lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is obtained by the following formula (2). Lap rate L [%] = (overlap amount d of the existing pile removal and backfilling portion and the newly installed pile shaft boring portion / newly installed pile shaft bore diameter D2 of the newly installed pile shaft boring portion) × 100 ··· (2)

[0040] As shown in FIG. 1, the overlap amount d of the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is the maximum length in the radial direction of the newly installed pile shaft boring portion 30 at the portion where the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 overlap in plan view.

[0041] Further, as shown in FIG. 6, when the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 do not overlap in plan view, the overlap amount d of the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is set to the shortest distance (distance between outer ends) between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30. Also, when the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 do not overlap in plan view, the lap rate L is set to negative (minus).

[0042] In addition, the existing pile removal and backfilling diameter (diameter) D1 of the existing pile removal and backfilling portion 14 is set to be the largest among the excavation equipment such as casings and augers used during construction, for example. Further, the new pile shaft boring diameter D2 of the new pile shaft boring portion 30 is set to be the diameter of the new pile shaft boring portion 30 on the ground surface of the ground (construction ground) G, for example.

[0043] FIG. 7 shows, as an example, a graph indicating the relationship between the lap rate L [%] of the existing pile removal and backfilling portion 14 and the new pile shaft boring portion 30, and the eccentricity R [mm] of the boring rod 40 for forming the new pile shaft boring portion 30. In FIG. 7, as described above, the existing pile removal and backfilling portion 14 is constructed by various construction methods capable of controlling the existing pile removal and backfilling portion 14 to a predetermined strength.

[0044] The allowable value of the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft boring portion 30 is set based on, for example, the allowable value of the eccentricity R of the new precast pile 20 (hereinafter referred to as the "allowable eccentricity").

[0045] Specifically, in the graph shown in FIG. 7, when the allowable eccentricity of the new precast pile 20 is 200 [mm], the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft boring portion 30 is in the range of 10 [%] or more and 30 [%] or less (10 - 30 [%]), and the allowable eccentricity of the new precast pile 20 will be exceeded. That is, the allowable value of the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft boring portion 30 is less than 10 [%] or more than 30 [ %]. This is presumably because the strength difference between the existing pile removal and backfilling portion 14 and the surrounding ground G makes the boring rod 40 (see FIG. 5) for forming the new pile shaft boring portion 30 prone to bending.

[0046] In this case, in the present embodiment, at least one of the existing pile removal and backfilling diameter D1 of the existing pile removal and backfilling portion 14 and the new pile shaft boring diameter D2 of the new pile shaft boring portion 30 is changed so that the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft boring portion 30 becomes the allowable value.

[0047] For example, in the embodiment shown in FIG. 8(A), the bored diameter D2 of the newly installed pile shaft bored part 30 is increased so that the lap rate L of the existing pile removal and backfilling part 14 and the newly installed pile shaft bored part 30 exceeds 30%.

[0048] On the other hand, in the embodiment shown in FIG. 8(B), the bored diameter D2 of the newly installed pile shaft bored part 30 is decreased so that the lap rate L of the existing pile removal and backfilling part 14 and the newly installed pile shaft bored part 30 is less than 10%.

[0049] Here, in the embodiment shown in FIG. 8(B), as a result of decreasing the bored diameter D2 of the newly installed pile shaft bored part 30, the pile diameter P of the newly installed precast pile 20 has also become smaller. If the pile diameter P of the newly installed precast pile 20 is decreased, there is a possibility that the vertical supporting force and the horizontal bearing capacity of the newly installed precast pile 20 will be insufficient.

[0050] Therefore, in the present embodiment, when the bored diameter D2 of the newly installed pile shaft bored part 30 is decreased, the newly installed precast pile 20 with a pile diameter P that can be constructed in the newly installed pile shaft bored part 30 is redesigned. At this time, for example, measures such as increasing the diameter D3 (see FIG. 3) of the bored part of the newly installed pile root consolidation part, increasing the pile length of the newly installed precast pile 20, changing the pile type of the newly installed precast pile 20, and changing the shape of the newly installed precast pile 20 are taken, so that the insufficient vertical supporting force and horizontal bearing capacity of the newly installed precast pile 20 can be compensated.

[0051] As an example of changing the pile type of the newly installed precast pile 20, for example, when the newly installed precast pile 20 is a PRC pile (prestressed reinforced concrete pile), the bending moment and shear resistance of the newly installed precast pile 20 can be increased by increasing the wall thickness of the newly installed precast pile 20 or increasing the bar diameter of the reinforcing bars.

[0052] Also, as another example of changing the pile type of the newly installed precast pile 20, for example, when the newly installed precast pile 20 is a PHC pile (pretensioned centrifugal high-strength prestressed concrete pile), it is conceivable to change the newly installed precast pile 20 to a PRC pile with a large amount of axial reinforcing bars.

[0053] As for the pile types of the newly installed precast piles 20, for example, RC piles (centrifugal reinforced concrete piles), PHC piles, SC piles (concrete piles with outer steel pipes), PRC piles, etc. can be mentioned. Further, as for the shapes of the newly installed precast piles 20, ST piles (tip-expanded PHC piles), joint piles (PHC piles with joints) can be mentioned.

[0054] Further, in the embodiment shown in FIG. 9(A), the existing pile removal and backfilling diameter D1 of the existing pile removal and backfilling part 14 is increased so that the lap ratio L of the existing pile removal and backfilling part 14 and the newly installed pile shaft boring part 30 exceeds 30 [%].

[0055] On the other hand, in the embodiment shown in FIG. 9(B), the existing pile removal and backfilling diameter D1 of the existing pile removal and backfilling part 14 is decreased so that the lap ratio L of the existing pile removal and backfilling part 14 and the newly installed pile shaft boring part 30 is less than 10 [%].

[0056] (Function and effect) Next, the function and effect of this embodiment will be described.

[0057] As described above, when the lap ratio L between the existing pile removal and backfilling part 14 formed by backfilling the bored part 12 after the removal of the existing pile 10 and the newly installed pile shaft boring part 30 formed in the ground G when newly installing the newly installed precast pile 20 at the planned position is outside the allowable value, the eccentricity of the newly installed pile shaft boring part 30 may increase. As a result, the eccentricity R of the newly installed precast pile 20 may increase, and the construction accuracy of the newly installed precast pile 20 may decrease.

[0058] In contrast, in this embodiment, when the lap ratio L between the existing pile removal and backfilling part 14 and the newly installed pile shaft boring part 30 is outside the allowable value, at least one of the existing pile removal and backfilling diameter D1 of the existing pile removal and backfilling part 14 and the newly installed pile shaft boring diameter D2 of the newly installed pile shaft boring part 30 is changed so that the lap ratio L becomes the allowable value. Thereby, the eccentricity of the newly installed pile shaft boring part 30 is reduced, and the eccentricity R of the newly installed precast pile 20 is reduced. Therefore, the construction accuracy of the newly installed precast pile 20 can be improved.

[0059] In addition, in the present embodiment, the allowable value of the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is set based on the allowable eccentricity of the newly installed precast pile 20. As a result, the eccentricity R of the newly installed precast pile 20 and the boring rod 40 is reduced, so that the construction accuracy of the newly installed precast pile 20 can be improved.

[0060] Here, as shown in FIG. 8(B), when the diameter D2 of the newly installed pile shaft boring of the newly installed pile shaft boring portion 30 is reduced, it may become difficult to construct the newly installed precast pile 20. Therefore, in the present embodiment, when the diameter D2 of the newly installed pile shaft boring of the newly installed pile shaft boring portion 30 is reduced, the newly installed precast pile 20 with a pile diameter P that can be constructed by the newly installed pile shaft boring portion 30 is redesigned. As a result, in the present embodiment, while improving the construction accuracy of the newly installed precast pile 20, the newly installed precast pile 20 can be easily constructed.

[0061] (Modification example) Next, a modification example of the above embodiment will be described.

[0062] In the examples shown in FIGS. 8(A) and 8(B), the diameter D2 of the newly installed pile shaft boring of the newly installed pile shaft boring portion 30 was changed so that the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 became the allowable value. On the other hand, in the examples shown in FIGS. 9(A) and 9(B), the diameter D1 of the existing pile removal and backfilling of the existing pile removal and backfilling portion 14 was changed so that the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 became the allowable value. However, it is also possible to change both the diameter D2 of the newly installed pile shaft boring and the diameter D1 of the existing pile removal and backfilling so that the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 becomes the allowable value.

[0063] In addition, the allowable value of the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 can be changed as appropriate. For example, when the allowable eccentricity of the newly installed precast pile 20 is 100 [mm], the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is in the range of 0 to 60 [%], and the allowable eccentricity of the newly installed precast pile 20 will be exceeded. That is, the allowable value of the lap rate L between the existing pile removal and backfilling portion 14 and the newly installed pile shaft boring portion 30 is more than 60 [%].

[0064] In addition, the allowable value of the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft portion drilling portion 30 may exceed 60 [%], or may be less than 10 [%], or may exceed 30 [ %].

[0065] In the above embodiment, the allowable value of the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft portion drilling portion 30 is set based on the allowable eccentricity of the new prefabricated pile 20. However, the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft portion drilling portion 30 is not limited to the allowable eccentricity of the new prefabricated pile 20, and can be set based on, for example, at least one of the allowable eccentricity of the new prefabricated pile 20 and the allowable eccentricity of the drilling rod 40. Further, the lap rate L of the existing pile removal and backfilling portion 14 and the new pile shaft portion drilling portion 30 may be set based on, for example, other indicators indicating the construction accuracy of the new prefabricated pile 20.

[0066] As described above, an embodiment of the present invention has been described. However, the present invention is not limited to such an embodiment, and an embodiment and various modifications may be used in appropriate combination, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.

Explanation of symbols

[0067] 10 Existing pile 12 Drilling portion 14 Existing pile removal and backfilling portion D1 Existing pile removal and backfilling diameter 20 New prefabricated pile 30 New pile shaft portion drilling portion D2 New pile shaft portion drilling diameter

Claims

Claim 1 When the lap rate L between the existing pile removal and backfilling part formed by backfilling the bored hole part after the removal of the existing pile and the newly bored pile shaft part formed in the ground when installing a new precast pile at the planned position is outside the allowable value, at least one of the existing pile removal and backfilling diameter of the existing pile removal and backfilling part and the newly bored pile shaft diameter of the newly bored pile shaft part is changed so that the lap rate L becomes the allowable value. Pile design method. Claim 2 When reducing the diameter of the newly bored pile shaft part, the new precast pile with a pile diameter that can be constructed in the newly bored pile shaft part is redesigned. The pile design method according to claim 1. Claim 3 The allowable value of the lap rate L is set based on at least one of the allowable eccentricity of the new precast pile and the allowable eccentricity of the boring rod for creating the newly bored pile shaft part. The pile design method according to claim 1 or claim 2. Claim 4 The newly bored pile shaft part is constructed so that the lap rate L between the existing pile removal and backfilling part obtained by backfilling the bored hole part after the removal of the existing pile and the newly bored pile shaft part formed in the ground when installing a new precast pile becomes the allowable value. Pile construction method.

Images