Pile construction method

Abstract

To provide a pile construction method that can address negative friction without increasing the number of piles and eliminates the need to apply a surface treatment agent.SOLUTION: There is provided a pile construction method in which a pile is driven into a ground G to construct the pile. The ground G has a first area G1 into which the piles are driven and a second area G2 located vertically below the first area G1. The pile construction method includes the steps of: replacing a ground material M1 constituting the first region G1 of the ground G with a low-friction material M3 which is a material having a smaller peripheral friction force than the ground material M1; and driving a pile 1 into the ground G so as to penetrate the first region G1 in which the low-friction material M3 is placed and to reach the second region G2.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a pile installation method for installing piles in ground. [Background technology]

[0002] Patent Document 1 describes a negative friction countermeasure pile (SL pile) that is a foundation pile to be constructed on soft ground and that has measures implemented to counter negative friction (negative frictional force) that occurs when the ground around the pile pulls the pile down during ground subsidence. The SL pile has a concrete pile body and a peripheral friction reducing material application part (SL application part) that is applied to the outer periphery of the pile body.

[0003] The SL coating section is composed of a primer layer applied to the outer periphery of the pile body, an asphalt layer formed on the primer layer, and a surface protection layer applied on the asphalt layer. The SL coating section has the function of reducing the force that pulls the pile down due to negative friction.

[0004] Patent Document 2 describes a negative friction countermeasure pile that reduces negative friction during ground subsidence. This negative friction countermeasure pile has an outer pipe having a first threaded portion formed on its outer circumferential surface and a second threaded portion provided so as to cover the first threaded portion and screwed into the first threaded portion. A convex portion having a semicircular cross section is formed on the outer circumferential surface of the outer pipe. The outer pipe has a mechanism that slides downward when a downward force exceeding a predetermined value acts on the outer pipe, and that restricts the sliding when an upward force acts on the outer pipe.

[0005] Patent Document 3 describes a surface treatment agent used in the negative friction cut method. The surface treatment agent has a surface treatment layer that is applied to the peripheral surface of the pile. The surface treatment layer contains a water-absorbent resin and a binder resin that is insoluble in water and alkaline water. By applying this surface treatment agent to the peripheral surface of the pile, friction between the peripheral surface of the pile and the ground is reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-96768 A [Patent Document 2] JP 2005-299292 A [Patent Document 3] JP 2008-163733 A Summary of the Invention [Problem to be solved by the invention]

[0007] If piles are designed without taking measures against the negative friction described above, the amount of piles must be increased. Specifically, the diameter of the piles must be increased, or the number of piles must be increased. Therefore, it is necessary to take measures against negative friction while avoiding increasing the amount of piles.

[0008] The negative friction countermeasure pile and surface treatment agent described above can counter negative friction without increasing the amount of piles. However, the method of applying the surface treatment agent to the pile before driving the pile into the ground may cause the surface treatment agent to peel off from the pile when driving the pile into the ground. For example, when the rotary press grips the body of the pile and rotates and presses the pile into the ground, the surface treatment agent may peel off from the body of the pile. Therefore, depending on the situation, the surface treatment agent may not be used.

[0009] The application of the surface treatment agent can be costly and time-consuming. For example, the application of the surface treatment agent to the piles may be carried out in a factory separate from the factory where the pile bodies (concrete parts of the piles) are manufactured. In this case, the cost and time-consuming transportation of the piles can be a problem.

[0010] The present disclosure aims to provide a pile construction method that can address negative friction without increasing the amount of piles and that eliminates the need to apply a surface treatment agent. [Means for solving the problem]

[0011] (1) The pile construction method according to the present disclosure is a pile construction method for constructing a pile by driving the pile into the ground. The ground has a first area into which the pile is driven and a second area located vertically below the first area. The pile construction method includes a step of replacing the ground material constituting the first area of ​​the ground with a low-friction material that has a lower peripheral friction force than the ground material, and a step of driving a pile into the ground so as to penetrate the first area replaced with the low-friction material and reach the second area.

[0012] The ground to which this pile construction method is applied has a first region into which the pile is driven and a second region located vertically below the first region. In this pile construction method, before driving the pile into the ground, the ground material constituting the first region is replaced with a low-friction material having a smaller peripheral friction force than the ground material. Then, the pile is driven into the first region replaced with the low-friction material. At this time, the pile is driven into the ground so as to penetrate the first region vertically and reach the second region. Therefore, since the first region into which the pile is driven is replaced with the low-friction material, the peripheral friction force on the pile can be reduced. Therefore, measures can be taken against negative friction and an increase in the number of piles can be avoided. Furthermore, since the pile is driven into the replaced low-friction material, the peripheral friction force on the pile can be reduced without applying a surface treatment agent to the pile. Therefore, the surface treatment agent can be eliminated, and the cost and effort required for the surface treatment agent can be eliminated.

[0013] (2) In the above (1), the pile construction method may include a step of measuring the N-value of the ground material, and a step of preparing a low-friction material having an N-value smaller than that of the ground material. In the step of replacing the ground material with the low-friction material, the ground material may be replaced with the low-friction material prepared in the preparation step. In this case, the low-friction material in the first region into which the pile is driven can be a material with a smaller N-value and a softer material. Therefore, the occurrence of negative friction can be more effectively suppressed.

[0014] (3) In the above (1) or (2), the pile construction method may include a step of measuring the adhesive force C of the ground material, and a step of preparing a low-friction material having an adhesive force C smaller than the adhesive force C of the ground material. In the step of replacing with the low-friction material, the ground material may be replaced with the low-friction material prepared in the preparing step. In this case, the low-friction material in the first region can be a material having a smaller adhesive force C. Thus, since the adhesive force C of the first region into which the pile is driven is reduced, the occurrence of negative friction can be more effectively suppressed.

[0015] (4) In any of the above (1) to (3), the replacing step may include a step of placing a cylindrical casing so as to surround the first region in a plan view and pressing the casing into the ground, a step of removing the ground material in the first region located inside the casing to form a space inside the casing, and a step of placing a low-friction material in the space. In this case, the ground material in the first region located inside the casing can be replaced with the low-friction material by pressing the casing into the ground. Therefore, the replacement of the ground material with the low-friction material can be easily performed using the casing. Effect of the Invention

[0016] According to the present disclosure, measures against negative friction can be taken without increasing the number of piles, and application of a surface treatment agent can be eliminated. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a plan view showing an example of a site to which a pile construction method according to an embodiment is applied. [Diagram 2] FIG. 2 is a cross-sectional view of the site of FIG. 1. [Diagram 3] 2 is a graph showing an example of the relationship between ground depth and N value at the site of FIG. 1. [Figure 4] 1A is a diagram showing the positional relationship between a pile and a casing in a plan view, and FIG. 1B is a diagram for explaining the position of the pile driven into the ground. [Diagram 5]1(a) and 1(b) are diagrams illustrating an example of steps of a pile construction method according to an embodiment. [Figure 6] 1(a), (b), and (c) are diagrams illustrating an example of steps of a pile construction method according to an embodiment. [Figure 7] 1(a), (b), and (c) are diagrams illustrating an example of steps of a pile construction method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the pile construction method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios and the like are not limited to those shown in the drawings.

[0019] Fig. 1 is a diagram showing a typical example of a site A to which the pile construction method according to the present embodiment is applied. Fig. 2 is a cross-sectional diagram showing a typical example of the site A. As shown in Figs. 1 and 2, at the site A, a pile 1 which is a foundation pile for a pier A2 of a road bridge A1 is constructed. As an example, the pile 1 has a cylindrical shape.

[0020] The piles 1 are driven into the ground G at the site A. At the site A, a plurality of piles 1 are constructed so as to be lined up along the extension direction D1 of the road bridge A1 and also lined up along the width direction D2 of the road bridge A1. As an example, three piles 1 are lined up along the extension direction D1 and two piles 1 are lined up along the width direction D2.

[0021] The driving of the pile 1 at the site A is performed, for example, in a low head environment. The "low head" is, for example, 15 m or less, and as an example, the height of the road bridge A1 is 15 m. Therefore, the pile construction method according to this embodiment is performed within a range of heights of 15 m or less from the ground J.

[0022] In this embodiment, a part of the ground G into which the pile 1 is driven is replaced with a low-friction material M3 (see FIG. 5(b)), which is a material with a smaller peripheral friction force. The "material with a smaller peripheral friction force" refers to a ground material with a smaller peripheral friction force on the pile 1 driven into the ground G. For example, the strength of the peripheral friction force is indicated by the magnitude of the N value, which will be described later, or the magnitude of the adhesive force C. The unit of the N value is the same as the unit of the adhesive force C.

[0023] FIG. 3 is a graph showing an example of the relationship between the depth of the ground G and the N value of the ground G. As shown in FIG. 2 and FIG. 3, the ground G has a first region G1, which is a region into which the pile 1 is driven, and a second region G2 located vertically below the first region G1. For example, the first region G1 is a fill layer at the head of the pile 1, and the second region G2 is a consolidated layer. The pile 1 is driven into the ground G so as to penetrate the first region G1 and reach the second region G2. For example, the depth from the ground J to the bottom end of the first region G1 is 10 m or more and 15 m or less, and the depth from the ground J to the bottom end of the second region G2 is 20 m or more and 25 m or less.

[0024] For example, the ground material M1 constituting the first region G1 of the ground G is gravelly soil (Bg layer). The ground material M2 constituting the second region G2 of the ground G is clayey soil (Ac layer). The N-value of the ground material M1 constituting the first region G1 is greater than the N-value of the ground material M2 constituting the second region G2. The N-value is an index that indicates the relative value of the hardness and compactness of the soil. The N-value is a value measured by a standard penetration test. The N-value may be calculated from the internal friction angle φ of the soil.

[0025] More specifically, the N-value indicates the number of blows required to drive a standard penetration test sampler 300 mm into the ground material by allowing a hammer weighing 63.5±0.5 kg to fall 760±10 mm freely into the ground material. A larger N-value indicates a harder ground material, and a smaller N-value indicates a softer ground material.

[0026] For example, the N value of the ground material M1 in the first region G1 is 30 or more and 60 or less, and the N value of the ground material M2 in the second region G2 is 2 or more and 8 or less. Therefore, in the ground G, the hard ground material M1 is located on the soft ground material M2. Therefore, when consolidation settlement occurs in the ground material M2, negative friction (negative peripheral friction force) may occur in which the hard ground material M1 pushes the pile 1 downward.

[0027] For example, the adhesive force C of the ground material M1 constituting the first region G1 is greater than the adhesive force C of the ground material M2 constituting the second region G2. The adhesive force C indicates the strength of the cohesive soil to resist external forces. More specifically, the adhesive force C indicates the electrochemical bonding force between soil particles that occurs when the soil particles adsorb water molecules or ions. The adhesive force C is measured by a direct shear test, a uniaxial compression test, or a triaxial compression test. If the adhesive force C of the ground material M1 is greater than the adhesive force C of the ground material M2, negative friction may also occur in the pile 1.

[0028] One possible measure to deal with negative friction is to apply a slip layer compound (SL compound) to the surface of the pile 1. The SL compound is a slip layer made of an asphalt mixture, and when applied to the surface of the pile 1, it reduces the peripheral friction force of the ground material M1 against the surface of the pile 1, thereby suppressing negative friction.

[0029] However, the SL compound has problems in that it is expensive and takes a long time to apply. For example, in the manufacture of the pile 1, it may be necessary to transport the pile 1 to a factory other than the manufacturing factory of the pile 1 in order to apply the SL compound. In addition, it may take several months to apply the SL compound.

[0030] Furthermore, when driving the pile 1 in a low head environment as in this embodiment, it may be impossible to use the SL compound. In a low head environment, a rotary press B (see FIG. 6(c)) is used to grip the body of the pile 1 and press the pile 1 into the ground G while rotating it. However, if the SL compound is applied to the surface of the pile 1, the SL compound may peel off when the rotary press B grips the pile 1.

[0031] As described above, in the pile construction method according to this embodiment, the pile 1 is constructed without using an SL compound. An example of the steps of the pile construction method according to this embodiment is described below. First, the N-values ​​of the ground materials M1 and M2, which are the portions of the ground G into which the pile 1 is driven, are measured (step of measuring the N-value). The adhesive strength C of the ground materials M1 and M2 may also be measured (step of measuring the adhesive strength C). The N-value and the adhesive strength C are measured, for example, by conducting an indoor test on the ground materials M1 and M2.

[0032] After measuring the N value and adhesive strength C of ground material M1, and the N value and adhesive strength C of ground material M2 as described above, it is determined whether the N value of ground material M1 is greater than the N value of ground material M2, and whether the adhesive strength C of ground material M1 is greater than the adhesive strength C of ground material M2. For example, when the N value of ground material M1 is greater than the N value of ground material M2, or the adhesive strength C of ground material M1 is greater than the adhesive strength C of ground material M2, the following steps are performed.

[0033] As shown in Fig. 4(a), a casing K is prepared to be placed so as to surround the area of ​​the pile 1 to be driven into the ground G and to be pressed into the ground G (step of preparing the casing). For example, the casing K is a steel pipe having a cylindrical shape. For example, the casing K is placed in a position surrounding a planned pile driving area R, which is an area of ​​the ground G into which the pile 1 is to be driven, in a plan view (step of placing the casing).

[0034] The planned pile driving region R is, for example, the upper end surface of the first region G1 of the ground G. As an example, in a plan view, the casing K is arranged so as to be concentric with the planned pile driving region R. The inner region of the casing K in the ground G is replaced with a low-friction material M3 (see FIG. 5(b)). The low-friction material M3 will be described in detail later.

[0035] Incidentally, as shown in Figure 4(b), when the pile 1 is driven into the ground G, the extension direction of the pile 1 may tilt with respect to the vertical direction. If the depth of the pile 1 driven into the ground G is H (m) and the horizontal deviation of the pile 1 driven into the ground G is L (m), it is expected that the pile 1 will tilt until the value of L / H becomes 1 / 300. In this case, if the value of H is 10 (m), the value of L will be 0.033 (m).

[0036] Therefore, as shown in Figures 4(a) and 4(b), if a casing K is arranged with an inner diameter such that the distance X from the outer peripheral surface R1 of the pile driving area R to the inner peripheral surface K1 of the casing K in a plan view is longer than 33 (mm), the entire inner area of ​​the casing K can be replaced with the low-friction material M3 even if the pile 1 tilts. However, in this embodiment, the distance X is set to 100 (mm) or more. As an example, the diameter of the pile driving area R is 1000 (mm), and the inner diameter of the casing K is 1200 (mm).

[0037] In this case, the inner region of the casing K can be more reliably replaced with the low-friction material M3. The distance X may be calculated from the particle size of the ground material interposed between the inner circumferential surface K1 of the casing K and the outer circumferential surface of the pile 1. In this case, the distance X is calculated so that the larger the particle size of the ground material is, the longer the distance X is, and the smaller the particle size of the ground material is, the shorter the distance X is.

[0038] After placing the casing K in a position surrounding the planned pile driving area R, as shown in Figures 5(a) and 5(b), the ground material M1 constituting the first area G1 of the ground G is replaced with a low-friction material M3, which is a material having a smaller peripheral friction force than the ground material M1. The casing K, which is placed so as to surround the first area G1 of the ground G in a plan view, is pressed into the ground G (pressing-in process).

[0039] At this time, the casing K arranged to surround the planned pile driving area R is pressed vertically downward to embed the casing K in the ground G, and the casing K is pressed in so that the casing K is located outside the first area G1 in a plan view. Then, the ground material M1 of the first area G1 located inside the casing K is removed to form a space S inside the casing K (a process of forming a space).

[0040] Also, a low-friction material M3 to be replaced is prepared (step of preparing a low-friction material). At this time, a low-friction material M3 having an N value smaller than the N value of the ground material M1 constituting the first region G1 is prepared. Also, a low-friction material M3 having an adhesive force C smaller than the adhesive force C of the ground material M1 may be prepared. For example, the low-friction material M3 is sand. In this case, the N value of the low-friction material M3 is 4 or more and 10 or less (7 as an example). Also, the low-friction material M3 may be soil generated on-site. In this case, soil from the site A is obtained in advance, and an indoor test is performed on the soil to measure the N value and adhesive force C of the soil, and then the soil is treated as soil generated on-site.

[0041] After forming the space S and preparing the low-friction material M3, the low-friction material M3 is placed in the space S (step of placing the low-friction material). At this time, it is replaced with the low-friction material M3 prepared in the step of preparing the low-friction material. The low-friction material M3 is filled into the space S until it reaches the ground J. Through the above steps, the ground material M1 constituting the first region G1 of the ground G is replaced with the low-friction material M3 having a smaller peripheral friction force than the ground material M1 (step of replacing).

[0042] After the low-friction material M3 is placed inside the casing K, the casing K is pulled out of the ground G, and the pile 1 is driven into the ground G. At this time, the pile 1 is driven into the ground G so as to penetrate the first region G1 replaced with the low-friction material M3 and reach the second region G2 (pile driving process).

[0043] A specific example of driving the pile 1 will be described below. The pile 1 is driven into the ground G by, for example, the SPACE21 method. The SPACE21 method is a type of inner excavation pile method, and employs a cement milk jet mixing method (mechanical mixing method). As shown in Fig. 6(a), a rail E1 is installed on the ground J, and a rotary press-in machine B is placed on the rail E1 by a crane E2.

[0044] The rotary press-in machine B is, for example, a machine dedicated to the space construction method (space machine). The rotary press-in machine B is a hydraulic full-swivel machine. The rotary press-in machine B can reduce the peripheral friction force of the pile 1 during driving by injecting drilling water W (described later) into the location where the pile 1 is driven and rotating the pile 1 at a predetermined speed or faster. This reduces the force required to drive the pile 1, allowing the rotary press-in machine B to be made compact. As an example, the weight of the rotary press-in machine B is 10 tons.

[0045] After the rotary press-in machine B is installed on the rail E1, the rotary press-in machine B is moved along the rail E1 so that the rotary press-in machine B is positioned directly above the planned pile driving area R (first area G1). Then, as shown in Fig. 6(b), a drilling head E3 is attached to the lower end of the pile 1, and the pile 1 is hoisted up by a crane.

[0046] The drilling head E3 is a device that injects drilling water W into the ground G. As shown in FIG. 6(c), a shaft E4 extends from the drilling head E3 into the pile 1, and the upper end of the shaft E4 is connected to a swivel E5 located above the pile 1. Then, the pile 1 is lowered onto the rotary press B, and drilling water W is supplied from above the pile 1 into the inside of the pile 1, and the pile 1 is rotary pressed into the ground G (first region G1) while the drilling water W is discharged from the drilling head E3. At this time, muddy water F is generated, which is, for example, collected by a sand pump P and disposed of.

[0047] When the pile 1 is a joint pile, as shown in Fig. 7(a), the lower pile 1A of the pile 1 is pressed into the upper pile 1B to a height where they can be connected, and then the swivel E5 is removed from the lower pile 1A. For example, the upper pile 1B is joined to the lower pile 1A by welding. Then, the upper pile 1B is rotary pressed into the ground G by the rotary press-in machine B.

[0048] As shown in FIG. 7(b), after the upper pile 1B is pressed into the ground G, pliers E6 are placed on the upper pile 1B. Then, the upper pile 1B is further pressed into the ground G, and the height of the pile 1 (upper pile 1B) is confirmed. As shown in FIG. 7(c), the drilling water W is switched to cement milk Y, and the cement milk Y is discharged from the bottom end of the pile 1. By discharging the cement milk Y from the bottom end of the pile 1 in this manner, a base reinforcement bulb Z of the pile 1 is created. After that, the swivel E5 and pliers E6 are removed from the pile 1, and the rotary press B and rail E1 are removed, completing the series of steps in the construction of the pile 1.

[0049] Next, the effects of the pile construction method according to this embodiment will be described. The ground G to which this pile construction method is applied has a first region G1 into which the pile 1 is driven, and a second region G2 located vertically below the first region G1. In this pile construction method, before driving the pile 1 into the ground G, the ground material M1 constituting the first region G1 is replaced with a low-friction material M3 having a smaller peripheral friction force than the ground material M1. Then, the pile 1 is driven into the first region G1 replaced with the low-friction material M3. At this time, the pile 1 is driven into the ground G so as to penetrate the first region G1 vertically and reach the second region G2.

[0050] Therefore, by replacing the first region G1 into which the pile 1 is driven with the low friction material M3, the peripheral friction force on the pile 1 can be reduced. Therefore, measures can be taken against negative friction and an increase in the amount of piles 1 can be avoided. In other words, since the peripheral friction force generated in the pile 1 is reduced by replacing it with the low friction material M3, there is no need to increase the number of piles 1 or make the piles 1 thicker to deal with negative friction. Furthermore, by driving the pile 1 into the replaced low friction material M3, the peripheral friction force on the pile 1 can be reduced without applying a surface treatment agent to the pile 1. Therefore, the surface treatment agent is unnecessary, and the cost and effort required for the surface treatment agent can be eliminated.

[0051] The pile construction method according to this embodiment includes a step of measuring the N-values ​​of ground materials M1 and M2, and a step of preparing a low-friction material M3 having an N-value smaller than that of the ground material M1. In the step of replacing the ground material M1 with the low-friction material M3, the ground material M1 is replaced with the low-friction material M3 prepared in the preparation step. In this case, the low-friction material M3 in the first region G1 into which the pile 1 is driven can be a material with a smaller N-value and a softer material. Therefore, the occurrence of negative friction can be more effectively suppressed.

[0052] In this embodiment, the pile construction method may include a step of measuring the adhesive force C of the ground materials M1 and M2, and a step of preparing a low-friction material M3 having an adhesive force C smaller than the adhesive force C of the ground material M1. In the step of replacing the ground material M1 with the low-friction material M3, the ground material M1 may be replaced with the low-friction material M3 prepared in the preparation step. In this case, the low-friction material M3 in the first region G1 can be a material having a smaller adhesive force C. Therefore, since the adhesive force C in the first region G1 into which the pile 1 is driven is reduced, the occurrence of negative friction can be more effectively suppressed.

[0053] In this embodiment, the replacing step includes a step of placing a cylindrical casing K so as to surround the first region G1 in a plan view and pressing the casing K into the ground G, a step of removing the ground material M1 in the first region G1 located inside the casing K to form a space S inside the casing K, and a step of placing a low-friction material in the space S. In this case, the casing K is pressed into the ground G to replace the ground material M1 in the first region G1 located inside the casing K with the low-friction material M3. Therefore, the casing K can be used to easily replace the ground material M1 with the low-friction material M3.

[0054] The above describes the embodiment of the pile construction method according to the present disclosure. However, the pile construction method according to the present disclosure is not limited to the above-mentioned embodiment, and may be further modified within the scope of the gist described in the claims. In other words, the content and order of the steps of the pile construction method according to the present disclosure can be appropriately changed within the scope of the above gist.

[0055] For example, in the above-mentioned embodiment, an example was described in which the rotary press-in machine B grips the body of the pile 1 and rotates and presses the pile 1 in under a low headroom environment, thereby driving the pile 1. However, a machine other than the rotary press-in machine B may be used to drive the pile 1, and the site may not be under a low headroom environment. At a site not under a low headroom environment, for example, the pile 1 can be driven by a three-point pile driver. For example, in the above-mentioned embodiment, a pile construction method was described in which the pile 1 is driven into the ground G of the site A where the pier A2 of the road bridge A1 is to be provided. However, the pile construction method according to the present disclosure is also applicable to various sites other than the site A where the pier A2 of the road bridge A1 is to be provided. [Explanation of symbols]

[0056] 1...pile, 1A...lower pile, 1B...upper pile, A...site, A1...road bridge, A2...pier, B...rotary press, C...adhesion, D1...extension direction, D2...width direction, E1...rail, E2...crane, E3...drilling head, E4...shaft, E5...swivel, E6...pliers, F...mud, G...ground, G1...first area, G2...second area, J...ground, K...casing, K1...inner surface, M1, M2...ground material, M3...low-friction material, P...sand pump, R...area to be driven into piles, R1...outer surface, S...space, W...drilling water, X...distance, Y...cement milk, Z...root reinforcement bulb.

Claims

1. A pile construction method for driving a pile into ground and constructing the pile, The ground has a first area into which the pile is driven and a second area located vertically below the first area, A step of replacing the ground material constituting the first region of the ground with a low-friction material that has a lower peripheral friction force than the ground material; Driving the pile into the ground so as to penetrate the first region replaced with the low friction material and reach the second region; Equipped with Pile construction method.

2. Measuring the N value of the ground material; Providing the low friction material with an N value smaller than the N value of the geotechnical material; Equipped with In the step of replacing the ground material with a low friction material, the ground material is replaced with the low friction material prepared in the step of preparing. The pile installation method according to claim 1.

3. Measuring the adhesion C of the ground material; preparing the low friction material having an adhesion force C smaller than the adhesion force C of the ground material; Equipped with In the step of replacing the ground material with a low friction material, the ground material is replaced with the low friction material prepared in the step of preparing. The pile installation method according to claim 1.

4. The replacing step includes: A step of placing a cylindrical casing so as to surround the first region in a plan view and pressing the casing into the ground; removing the ground material in the first area located inside the casing to form a space inside the casing; disposing the low friction material in the space; having The pile construction method according to any one of claims 1 to 3.

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