Pile, pile construction method, structure, structure construction method, pile design method, and pile manufacturing method

Abstract

To provide a pile, a pile construction method, a structure, a structure construction method, a pile design method, and a pile manufacturing method which do not require large-scale equipment for construction, are excellent in economic efficiency and environmental aspects, and can exert high pull-out bearing force and high push-in bearing force even under conditions of little penetration into a bearing layer, and can suppress the occurrence of construction troubles. [Solution] The pile of the present invention is a pile having two or more plate-shaped fins arranged on the outer surface of the lower end of the pile body, and each fin has a vertical length of 0.5 to 1.75 times the outer diameter of the pile body, an inclination angle of 0 to 1 degree relative to the central axis of the pile body, and a lower end position above the lower end position of the pile body and a distance to the lower end position of the pile body of 50 mm or less.

Description

[Technical field]

[0001] The present invention relates to a pile, a pile construction method, a structure, a method for constructing a structure, a method for designing a pile, and a method for manufacturing a pile. [Background technology]

[0002] Steel pipe piles are commonly used in port structures. Depending on the structure and ground conditions, such as piers and wharf backing piles, high pull-out bearing capacity is required for steel pipe piles. A method for increasing pull-out bearing capacity is the rotary pile method, in which wings are attached to the tip of the steel pipe pile. In the port field, due to the constraints of construction space, the driving pile method using impact hammers and vibro hammers is mainstream, and the rotary pile method, which requires a relatively large rotary construction machine, has not been applied. Another method is to penetrate the steel pipe pile using a vibro method combined with a water jet, and then switch to cement milk injection underground to integrate the steel pipe pile and the ground. However, this method requires large equipment required for water jets and cement milk injection, making it uneconomical for offshore construction that requires a ship. Furthermore, this method is undesirable from the perspective of the port environment because it uses cement milk.

[0003] On the other hand, piles have been proposed that can be constructed by the driving pile method and press-in method that are mainstream in the port field without using water jets or cement milk injection, and that can demonstrate high pull-out bearing capacity. For example, a steel pipe pile with multiple spiral ribs formed in a spiral shape on the outer circumferential surface of the lower side of the steel pipe (see Patent Document 1) and a steel pipe pile with a plate-shaped protrusion fixed along the axial direction of the steel pipe pile body (see Patent Document 2) have been proposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-95880 A [Patent Document 2] Japanese Utility Model Application Publication No. 3-18238 Summary of the Invention [Problem to be solved by the invention]

[0005] The steel pipe pile described in Patent Document 1 enhances the pull-out bearing capacity by the peripheral friction force of the spiral rib. However, the steel pipe pile described in Patent Document 1 is not economical because it is necessary to form the spiral rib in a spiral shape on the outer circumferential surface of the steel pipe. On the other hand, the steel pipe pile described in Patent Document 2 enhances the pull-out bearing capacity by the peripheral friction force and bearing pressure of the plate-shaped protrusion. However, the steel pipe pile described in Patent Document 2 requires the formation of a relatively large protrusion to increase the peripheral friction force, so it is expensive and not economical in terms of material costs and processing costs. Furthermore, in order to exert sufficient pull-out bearing capacity, it is necessary to penetrate the tip of the pile into the supporting layer more than usual in order to penetrate the entire protrusion into the supporting layer. Therefore, the construction becomes large-scale, and there is a possibility of construction troubles such as construction space restrictions, noise and vibration, penetration failure, and damage to the pile body.

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a pile, a pile construction method, a structure, a method for constructing a structure, a method for designing a pile, and a method for manufacturing a pile that do not require large-scale equipment for construction, are economical and environmentally friendly, and further, are capable of exerting high pull-out support force and high compressive support force even under conditions of low penetration into the supporting layer, and are capable of suppressing the occurrence of construction problems. [Means for solving the problem]

[0007] The pile of the present invention has two or more plate-shaped fins arranged on the outer peripheral surface of the lower end of the pile body, and each of the fins has a vertical length of 0.5 to 1.75 times the outer diameter of the pile body and an inclination angle of 0 degrees to 45 degrees with respect to the central axis of the pile body.

[0008] The pile construction method of the present invention involves inserting the pile of the present invention into ground where a supporting layer exists, so that the upper end of the fin arranged on the pile is positioned within the supporting layer.

[0009] A structure according to the present invention includes the pile according to the present invention.

[0010] A method for constructing a structure according to the present invention includes a step of driving a pile according to the present invention into ground.

[0011] The pile design method of the present invention is a pile design method of the present invention, in which the inclination angle is set based on the pull-out support capacity and compressive support capacity required of the pile, and then the lower limit value of the vertical length is set in accordance with the pull-out support capacity and the compressive support capacity.

[0012] The pile design method of the present invention designs a pile having two or more plate-shaped fins arranged on the outer peripheral surface of the lower end of the pile body, and each of the fins is set so that the vertical length is between 0.5 and 1.75 times the outer diameter of the pile body, and the inclination angle is between 0 degrees and 45 degrees with respect to the central axis of the pile body.

[0013] The pile manufacturing method of the present invention produces a pile having two or more plate-shaped fins arranged on the outer peripheral surface of the lower end of the pile body, and each of the fins is formed so that its vertical length is between 0.5 and 1.75 times the outer diameter of the pile body and its inclination angle is between 0 degrees and 45 degrees with respect to the central axis of the pile body. Effect of the Invention

[0014] The piles, pile construction methods, structures, structure construction methods, pile design methods, and pile manufacturing methods of the present invention do not require large-scale equipment for construction, are economically and environmentally friendly, and can exert high pull-out support force and high compressive support force even under conditions of low penetration into the supporting layer, thereby suppressing the occurrence of construction problems. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a conceptual diagram illustrating a pile according to an embodiment of the present invention, in which (a) shows a case in which the fin is attached approximately parallel to the central axis of the pile body, and (b) shows a case in which the fin is attached at an angle to the central axis of the pile body. [Diagram 2] FIG. 2 is a conceptual diagram for explaining the behavior of the pull-out bearing capacity exhibited when a pull-out load acts on the pile according to the embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing the relationship between the penetration position of the lower end of a pile according to an embodiment of the present invention and the supporting layer. [Figure 4] FIG. 4 is a conceptual diagram of a construction method in which a pile according to an embodiment of the present invention is rotated and driven into a pile by a vertical load. [Diagram 5] FIG. 5 is a conceptual diagram showing the force acting on the fin when the pile according to the embodiment of the present invention is rotated and driven into the pile by a vertical load. [Figure 6] FIG. 6 is a diagram showing a three-dimensional FEM model used to verify the pull-out bearing capacity of a pile in the examples. [Figure 7] FIG. 7 is a graph showing the relationship between the applied load and the amount of pull-out calculated by an analysis of a pile with fins attached parallel to the central axis of the pile body. [Figure 8] FIG. 8 is a graph showing the relationship between the applied load and the amount of pull-out calculated by an analysis of a pile to which fins are attached at an angle relative to the central axis of the pile body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 1, a pile 1 according to an embodiment of the present invention has two or more plate-shaped fins 5 disposed on the outer peripheral surface of the lower end of the pile main body 3. Each fin 5 has a vertical length lfv of 0.5 to 1.75 times the outer diameter D of the pile main body 3, and an inclination angle β (see FIG. 1(b)) of 0 to 45 degrees with respect to the central axis of the pile main body 3.

[0017] 1(a) shows a case where the fin 5 is attached substantially parallel to the central axis of the pile main body 3, and FIG. 1(b) shows a case where the fin 5 is attached at an angle to the central axis of the pile main body 3. Here, "substantially parallel" indicates that the angle with respect to the central axis of the pile main body 3 is equal to or greater than 0 degrees and less than 1 degree.

[0018] Furthermore, the pile 1 according to the embodiment of the present invention satisfies one or more of the following conditions, as necessary: ​​the spacing between adjacent fins 5 is 1 / 16 or more of the outer periphery of the pile body 3; the spacing between adjacent fins 5 is 1 / 2 or less of the outer periphery of the pile body 3; the lower end position of the fin 5 is 50 mm or less from the lower end of the pile body 3; the upper end position of the fin 5 is 2 times or less than the outer diameter D of the pile body 3 from the lower end of the pile body 3; the fin width wf is 2 times or more the fin plate thickness tf; or the fin width wf is 1 / 2 or less of the outer diameter D of the pile body 3.

[0019] In FIG. 1, lt indicates the distance (50 mm or less) from the bottom end of the pile body 3 to the bottom end of the fin 5. α indicates the tip angle of the fin 5. Here, the tip angle α of the fin 5 is a predetermined angle determined from the relationship between the workability and bearing capacity required for the pile 1. The tip angle α is preferably 60 degrees or less to reduce the shear force received by the fin weld due to the bearing resistance of the fin plate thickness part when the pile is penetrated. Furthermore, the fin length lf is the distance when a straight line is drawn between the bottom end and the top end of the fin 5 on the attachment side of the pile body 3, and the fin horizontal length lfh is the length of the bottom end and the top end of the fin 5 in the direction perpendicular to the central axis of the pile body 3, and both are determined at the center of the plate thickness of the fin 5.

[0020] Before explaining the reason why the fins 5 in the pile 1 of this embodiment are limited as described above, we will explain the behavior of the pile 1 equipped with the fins 5 when a pull-out load acts on the pile 1.

[0021] Figure 2 shows a conceptual diagram of the pull-out capacity behavior when a pull-out load acts on the pile 1 shown in Figure 1(a). In Figure 2, the pull-out capacity exerting ground 13 shows the ground that resists in order to exert a pull-out capacity when the pile 1 is pulled out. Note that the pull-out capacity exerting ground 13 spreads near the top end of the fin due to the effect of the internal friction angle of the ground, and when it moves away from the fin by a certain distance, the spreading effect weakens and a cylindrical slide surface is formed. Also, the spreading effect due to the internal friction angle of the ground increases the stronger the ground is.

[0022] The pull-out bearing capacity increases as the range of the pull-out bearing capacity exerting ground 13 that resists when the pile 1 is pulled out becomes wider. Therefore, compared to the spiral ribs used in the steel pipe pile disclosed in the above-mentioned Patent Document 1, the use of fins 5 that protrude from the surface of the pile body 3 in the radial direction of the pile 1 makes the pull-out bearing capacity exerting ground 13 wider, and a high effect can be exhibited. Furthermore, the presence of the fins 5 not only increases the pull-out bearing capacity, but also improves the compressive bearing capacity because the compressive bearing capacity exerting ground (not shown) expands near the bottom end of the fins 5 due to the effect of the internal friction angle of the ground when the pile 1 is pushed in.

[0023] Next, the reasons for limiting the fins 5 in the pile 1 according to this embodiment will be described with reference to Figures 1 to 5. First, the "number of fins (lower limit)", "vertical length" and "inclination angle", which are conditions necessary to obtain the effects of the present invention, will be described.

[0024] (Number of fins (lower limit)) The number of fins 5 is two or more. The pull-out bearing capacity of the pile 1 is exerted by the resistance of the pull-out bearing capacity exerting ground 13, as shown in FIG. 2 described above. The more the number of fins 5, the stronger the force transmitted from the fins 5 to the ground, and the stronger the effect of the internal friction angle of the ground in the pull-out bearing capacity exerting ground 13 near the top end of the fins, and the higher the pull-out bearing capacity. In addition, the presence of the fins 5 not only increases the pull-out bearing capacity, but also improves the compressive bearing capacity, since the compressive bearing capacity exerting ground spreads due to the effect of the internal friction angle of the ground near the bottom end of the fins 5 when the pile 1 is pushed in. In addition, as described above, the presence of the fins 5 (i.e., one or more fins 5) not only increases the pull-out bearing capacity, but also improves the compressive bearing capacity. This is because, as described above, the compressive bearing capacity exerting ground spreads due to the effect of the internal friction angle of the ground near the bottom end of the fins 5 when the pile 1 is pushed in. Therefore, the number of fins 5 is determined by the workability, pull-out support force, and compressive support force required for the pile 1. Furthermore, in this embodiment, the number of fins 5 is set to two or more in order to stably penetrate the pile 1 in the axial direction.

[0025] (Vertical length) The vertical length lfv is 0.5 to 1.75 times the outer diameter D of the pile main body 3 (see Fig. 1). Here, the vertical length lfv is the distance between the lower end and the upper end of the fin thickness center in the central axis direction of the pile main body 3, as shown in Fig. 1.

[0026] The reason why the vertical length lfv satisfies the above range will be explained with reference to Fig. 3. Fig. 3 is a schematic diagram showing the relationship between the vertical penetration position of the pile 1 and the supporting layer 15 when the pile 1 is penetrated into the ground 11 below which the supporting layer 15 exists. Fig. 3(a) shows the case where the upper end of the fin 5 is located within the supporting layer 15, and Fig. 3(b) shows the case where the upper end of the fin 5 is not located within the supporting layer 15.

[0027] In general, the ground for which the pile is required to have improved pull-out and compressive bearing capacity is one in which a bearing layer (hard ground) exists under a thick, soft ground. This is because in a soft ground, the pull-out and compressive bearing capacity due to the peripheral friction between the pile body and the ground cannot be expected. In the pile 1 according to this embodiment, the presence of the fin 5 not only increases the pull-out bearing capacity, but also improves the compressive bearing capacity. This is because, as described above, the compressive bearing capacity exerting ground spreads due to the effect of the internal friction angle of the ground near the lower end of the fin 5 even when the pile 1 is pushed in. On the other hand, in the pile 1 according to this embodiment, the pull-out bearing capacity is exerted by the resistance of the pull-out bearing capacity exerting ground 13. Therefore, in order to make the pull-out bearing capacity exerting ground 13 sufficiently wide, it is desirable that the upper end of the fin 5 is located in the bearing layer 15, which is a solid ground with a large internal friction angle of the ground. In order to reliably position the upper ends of the fins 5 within the support layer 15, it is desirable to make the fin length lf short within a range that does not impair performance.

[0028] However, if the fin length lf is too short, it becomes difficult to temporarily fix the fin 5 with a jig when welding the fin 5 to the pile main body 3 made of a steel pipe, and the workability when attaching the fin 5 deteriorates. Since the size of the jig changes depending on the outer diameter of the pile main body 3, in the pile 1 according to this embodiment, the vertical length lfv is set to be 0.5 times or more the outer diameter of the pile main body 3 so that the fin length lf is not too short.

[0029] On the other hand, if the fin length lf is too long under the same construction conditions, the upper end of the fin 5 does not penetrate into the supporting layer 15 as shown in FIG. 3(b), and sufficient pull-out supporting force cannot be exerted.

[0030] Also, depending on the conditions of the supporting layer 15, it is possible to increase the penetration amount of the pile 1 into the supporting layer 15. However, in many cases, the penetration of the pile 1 stops before reaching the depth assumed in practice, and if the fin length lf is carelessly increased, the risk that the upper end of the fin 5 will not be located in the supporting layer 15 increases. In general, the guideline for the penetration amount into the supporting layer in the driving pile method is about twice the outer diameter of the pile body, taking into account the strength of the construction machine and the pile body. Therefore, in the pile 1 according to this embodiment, in order to stably penetrate the fin 5 into the supporting layer 15, position the upper end of the fin 5 in the supporting layer 15, and exert a sufficient pull-out bearing force by the resistance of the ground 13 that exerts a pull-out bearing force, the vertical length lfv is set to 1.75 times or less of the outer diameter D of the pile body 3.

[0031] (Tilt angle) The inclination angle β is between 0 and 45 degrees with respect to the central axis of the pile main body 3 (see FIG. 1). Here, the inclination angle β is the angle with respect to the central axis of the pile main body 3 when the point at 1 / 2 of the fin length lf is set as the center of rotation.

[0032] The reason for setting the inclination angle β in the above range is as follows: Fig. 4 shows a construction concept when a pile 1 having an inclination angle β of 1 to 45 degrees is vertically driven into the ground 11.

[0033] When the inclination angle β is 0 degrees or more and less than 1 degree (FIG. 1(a)), the fins 5 (vertical fins) are approximately parallel to the central axis of the pile body 3, resulting in vertical penetration similar to that of a typical steel pipe pile. On the other hand, when the inclination angle β is 1 degree or more and 45 degrees or less (FIG. 1(b)), the fins 5 (inclined fins) are inclined to the central axis of the pile body 3, so that when a vertical load is applied to the pile 1, the soil slips through between the fins 5 in the ground (black arrows in FIG. 4), and the pile 1 penetrates while rotating. In other words, when a vertical load is applied to the pile 1 with the fins 5 attached to the central axis of the pile body 3, the pile body 3 rotates, thereby reducing the penetration resistance provided by the fins 5.

[0034] As shown in FIG. 2, the pull-out capacity of the pile 1 is exerted by the resistance of the pull-out capacity exerting ground 13. The larger the inclination angle β, the stronger the force transmitted from the fin 5 to the ground, and the stronger the effect of the internal friction angle of the ground in the pull-out capacity exerting ground 13 near the top end of the fin, thereby increasing the pull-out capacity. On the other hand, if the inclination angle β is large, the resistance force at the time of penetration increases, and the construction efficiency decreases. Therefore, the inclination angle β needs to be considered not only in terms of the pull-out capacity but also in terms of the penetration resistance. The relationship between the inclination angle and the penetration resistance will be explained below.

[0035] Fig. 5 shows the force acting on the fin 5 when the pile 1 is rotated and inserted into the ground 11 by a vertical load when the inclination angle β is 30 degrees (Fig. 5(a)) and 60 degrees (Fig. 5(b)). Note that the pile 1 and the pile body 3 are not shown in Fig. 5.

[0036] When a vertical load is applied to the pile to penetrate the ground 11, a normal force acts on the fin 5 from the ground 11, and a rotational force (called the "fin thrust force") that rotates the pile main body 3 around its central axis acts on the pile main body 3. Specifically, the normal force on the fin 5 is divided into the vertical direction of the ground 11 and a direction perpendicular to the vertical direction. The component force perpendicular to the vertical direction corresponds to the "fin thrust force." In FIG. 5, the vertical direction of the ground 11 coincides with the axial direction of the pile main body 3, and the direction perpendicular to the vertical direction of the ground 11 coincides with the tangent direction to the outer periphery of the pile main body 3. Therefore, the fin thrust force becomes a rotational force on the pile main body 3.

[0037] Comparing the case where the inclination angle β is 30 degrees (FIG. 5(a)) with the case where the inclination angle β is 60 degrees (FIG. 5(b)), the fin thrust force is smaller when the inclination angle β is large, 60 degrees. In this way, when the inclination angle β is too large, the thrust force is smaller, and as a result, the penetration resistance is larger.

[0038] Therefore, in this embodiment, the inclination angle β is set to 45 degrees or less so that the ratio of the fin thrust force (the rotational force of the pile main body 3) to the vertical load does not decrease significantly and the pile 1 can be penetrated without losing the rotational force of the pile main body 3.

[0039] In this embodiment, the lower limit of the inclination angle β is set to 0 degrees or more. However, since the pile body 3 is rotated while being penetrated during construction to reduce the penetration resistance, it is preferable to set the inclination angle β to 1 degree or more.

[0040] Next, the selection conditions "fin lower end position", "fin upper end position", "fin width", "number of fins (upper limit)", and "fin spacing" will be explained. These selection conditions can be set as necessary depending on the use of the pile, the purpose of the pile construction, the ground and supporting layer to be penetrated, etc.

[0041] (Fin bottom position) The lower end position of the fin 5 is preferably set so that the distance lt from the lower end of the pile main body 3 to the lower end of the fin 5 is 50 mm or less (see FIG. 1). This is because the attachment position of the fin 5 is preferably as close to the lower end of the pile main body 3 as possible, taking into consideration the workability of the lower end of the pile main body 3 and, for example, the weldability when attaching the fin 5 to the pile main body 3 in the case of a pile main body 3 made of a steel pipe.

[0042] (fin top position) The position of the upper end of the fin 5 is preferably set to a distance not greater than twice the outer diameter D of the pile main body 3 from the lower end of the pile main body 3 (see Fig. 1). The position of the upper end of the fin 5 is determined from the viewpoint of stably penetrating the support layer 15 and positioning the upper end of the fin 5 within the support layer 15, as shown in Fig. 3(a) described above.

[0043] (fin width) The fin width wf is preferably at least twice the fin plate thickness tf. The fin width wf is preferably no more than 1 / 2 the outer diameter of the pile main body 3 (see FIG. 1). Here, the fin width wf is the circumferential length of the fin at the 1 / 2 position of the fin length lf, as shown in FIG. 1. The pull-out bearing capacity increases as the range of the pull-out bearing capacity exerting ground 13 that resists when the pile 1 is pulled out increases. For this reason, the greater the amount of protrusion from the surface of the pile main body 3, the wider the range of the pull-out bearing capacity exerting ground 13, and the greater the effect.

[0044] The lower limit of the fin width wf takes into consideration the ease of attaching the fin 5 to the pile body 3. The upper limit of the fin width wf is set because, when the outer diameter of an imaginary circle passing through the outermost edge of the fin 5 is defined as the fin outer diameter Df (see FIG. 1), from the viewpoint of workability, the fin outer diameter Df is preferably up to about twice the outer diameter of the pile body 3.

[0045] (Number of fins (maximum) and spacing) The number of fins 5 attached is preferably 16 or less. The lower limit of the interval between adjacent fins 5 is preferably 1 / 16 or more of the outer diameter D of the pile main body 3. The upper limit is preferably 1 / 2 or less. Here, the interval between adjacent fins 5 is the distance between the center of the plate thickness of the fins 5 in the outer circumferential direction of the pile main body 3.

[0046] The reason why the number and interval of the fins 5 are set within the above range is as follows. At least two fins are required to stably penetrate the pile 1 in the axial direction, and when two fins 5 are attached at equal intervals in the circumferential direction of the pile main body 3, the fin interval is 1 / 2 of the circumferential length of the pile main body 3. On the other hand, the upper limit of the number of fins 5 to be attached is preferably 16 or less, considering the required working space, since when a steel pipe is used for the pile main body 3, the fins 5 are generally attached to the pile main body 3 later by welding or the like. Then, when 16 fins 5 are attached at equal intervals in the circumferential direction of the pile main body 3, the interval between adjacent fins 5 is 1 / 16 of the circumferential length of the pile main body 3. Note that, within the above range, the more the number of fins 5, the more expensive it is, but the larger the bearing area of ​​the upper end of the fins 5 is, so that the load transmission force to the ground is increased and the pull-out bearing force is improved.

[0047] As described above, the pile 1 according to the embodiment of the present invention can exert high pull-out bearing force and high pushing bearing force even under conditions where penetration into the bearing layer is small. Therefore, less force is required to penetrate the bearing layer, and the machinery used for construction can be made smaller. This makes it possible to suppress construction troubles such as restrictions on construction space, noise and vibration, poor penetration, and damage to the pile body, and provides a pile that is excellent in terms of construction, economy, and environment.

[0048] Furthermore, the pile 1 according to the embodiment of the present invention is particularly suitable for port structures that require high pull-out and compressive load bearing capacity. Port structures here refer to piers, quay wall support piles, and the like. In addition to port structures, the pile 1 can also be similarly applied to offshore wind power foundations, building foundations, pier foundations, bedrock anchors, and the like. This is because these structures may also require high pull-out and compressive load bearing capacity.

[0049] As shown in Fig. 3, the most preferable usage of the pile 1 according to this embodiment is to penetrate into the bearing layer where the bearing capacity is maximized. The present invention is not limited to such usage, and can also be applied to friction piles that do not penetrate into the bearing layer and to batter piles. Furthermore, the pile can improve the pull-out bearing capacity and the compressive bearing capacity compared to a general steel pipe pile (also called a bare pipe).

[0050] The fins 5 may be attached at unequal intervals within the above-mentioned fin interval range. The fins 5 do not necessarily need to be attached symmetrically with respect to the central axis of the pile body 3, and may be attached asymmetrically by appropriate design and construction management. The fins 5 shown in FIG. 1 are attached so as to rotate clockwise with respect to the central axis of the pile body 3, but may be attached so as to rotate counterclockwise. Fins may be attached to the pile head, but they will hinder the rotation of the pile that occurs during construction and cause disturbance to the ground, so it is preferable not to attach fins to the pile head. Even if the fins are approximately parallel, the pile may rotate depending on the condition of the ground and the way the load is applied.

[0051] Furthermore, the pile 1 according to the present embodiment is not limited to a steel pipe pile having a steel plate fin attached to a steel pipe pile body, but can also be applied to a concrete pile. In the case of a concrete pile, the fin may also be made of concrete using a formwork.

[0052] In the above explanation, a pile has been described as an invention of a product, but the pile 1 according to the embodiment of the present invention can be used in a construction method in which the pile is penetrated so that the upper end of the fin 5 disposed at the lower end of the pile body 3 is located within the supporting layer. By this construction method, the pile 1 according to the embodiment can be penetrated into the ground where the supporting layer exists. Note that the construction method used in this case for penetrating the pile 1 into the ground is not particularly limited. Publicly known, previously known, or unknown pile construction methods can be used.

[0053] Furthermore, the pile 1 according to the embodiment of the present invention can be applied to a construction method of penetrating into the ground by a driving pile method or a press-in method. Furthermore, the pile 1 according to the embodiment is very suitable as a pile to be used in these construction methods. This is for the following reasons.

[0054] Generally, the smaller the resistance force generated when a load is applied to a pile during construction, the easier it is to construct. The pile 1 according to this embodiment has a relatively small inclination angle β (see FIG. 1(b)), so it has a small resistance force against a vertical load and is suitable for the driving pile method or the press-in method, which are construction methods using a vertical load. However, in order to minimize the resistance force during penetration, care must be taken to avoid any rotational constraint during construction.

[0055] Next, an example of the pile 1 according to the present embodiment constructed by the driving pile method and an example of the pile constructed by the press-in method will be described. First, in the case of the driving pile method, a hammer such as a weight is dropped to apply an impact load to the pile head, or the pile is vibrated to temporarily reduce the strength of the ground, and the vertical load due to its own weight is relatively increased, and the pile is penetrated. On the other hand, in the case of the press-in method, the pile is penetrated by applying a static press-in load to the pile head in the vertical direction. Even when using these construction methods, it is more preferable to penetrate the pile into the ground so that the upper end of the fin 5 arranged at the lower end of the pile body 3 is located within the supporting layer.

[0056] Moreover, the pile 1 according to the present embodiment may be used in a structure provided with the pile 1 according to the present embodiment.

[0057] As described above, the pile according to the present invention is particularly suitable for, among other structures, port structures, offshore wind power foundations, building foundations, bridge pier foundations, bedrock anchors, and the like.

[0058] Moreover, the pile 1 according to this embodiment can be used in a method for constructing a structure including a step of driving the pile 1 into the ground.

[0059] Moreover, the pile 1 according to this embodiment can also be used in a method for constructing a structure that includes the above-mentioned method for constructing the pile 1.

[0060] In the above explanation, the pile has been described as an invention of a product, but the pile 1 according to this embodiment is designed by the following design method. This is a method for designing a pile having two or more plate-like fins arranged on the outer circumferential surface of the lower end of the pile body, in which the vertical length of each fin is set to be 0.5 to 1.75 times the outer diameter of the pile body, and the inclination angle is set to be 0 degrees to 45 degrees with respect to the central axis of the pile body.

[0061] The order of each component of the pile design method of the present invention is not limited to the order described above. The preferred ranges of each selection condition, such as the interval between adjacent fins, the lower end position and the upper end position of the fin, and the fin width, are the same as those described for the pile 1 according to the present embodiment. Therefore, it is preferable to set each of these selection conditions within the preferred ranges described for the pile 1 as necessary.

[0062] The pile 1 according to this embodiment is also designed by the following design method. First, the target pull-out bearing capacity of the pile 1 according to this embodiment is set. Next, the inclination angle β and the upper limit of the number of fins are set according to the pull-out bearing capacity required of the pile 1. This is because the inclination angle β and the upper limit of the number of fins have a large effect on the pull-out bearing capacity. When setting these conditions, if workability is prioritized, the inclination angle β is reduced and the number of fins is increased within the allowable range. On the other hand, if economy is prioritized, the inclination angle β is increased within the allowable range and the number of fins is reduced within the allowable range.

[0063] Then, after determining the inclination angle β and the number of fins, the lower limit of the vertical length lfv is set according to the pull-out bearing capacity required of the pile 1. When determining the vertical length lfv, if priority is given to workability, the vertical length lfv is increased within the allowable range, and if priority is given to economy, the vertical length lfv is decreased within the allowable range.

[0064] Furthermore, in the design method of the pile 1 according to this embodiment, in addition to the vertical length lfv, it is preferable to set the fin width wf according to the pull-out bearing capacity required of the pile 1. When determining the fin width wf, if priority is given to the workability of the pile 1, the fin width wf is reduced within the allowable range, and the vertical length lfv is increased within the allowable range. On the other hand, if priority is given to economy, the fin width wf is increased, and the vertical length lfv is reduced within the allowable range.

[0065] In addition, in the design method of the pile 1 according to this embodiment, the "allowable range" may be a range set according to the pull-out bearing capacity required of the pile 1, or it may be within the range of each condition of the fin 5 described above for the pile 1 according to this embodiment.

[0066] Furthermore, the pile 1 according to this embodiment is manufactured by the following manufacturing method, which is a method for manufacturing a pile having two or more plate-shaped fins arranged on the outer circumferential surface of the lower end of the pile body, and each of the fins is formed so that the vertical length is 0.5 to 1.75 times the outer diameter of the pile body and the inclination angle is 0 to 45 degrees with respect to the central axis of the pile body.

[0067] The order of the components of the pile manufacturing method of the present invention is not limited to the order described above. In addition, in the method for manufacturing the pile 1 according to this embodiment, the preferred ranges of the selection conditions of the interval between adjacent fins 5, the lower end position and the upper end position of the fin 5, and the fin width are the same as those described for the pile 1 according to this embodiment. Therefore, it is preferable to form each of these selection conditions within the preferred ranges described for the pile 1 as necessary.

[0068] [Example] An analysis was carried out to verify the effects of the present invention, which will be described below. In the analysis, the pull-out bearing capacity of a pile 23 was calculated using a three-dimensional FEM model 21 shown in FIG.

[0069] In the 3D FEM model 21 for verification, a pile 23 (outer diameter (D) of the pile body 25 is 609.6 mm, plate thickness is 12 mm, length is 9.34 m) equipped with a steel pipe pile body 25 and a steel plate fin 27 is placed in the center of the ground 31, and the lower end side of the pile 23 is embedded 1.22 m (twice the outer diameter of the pile body). The ground 31 is cylindrical with an outer diameter of 12 m and a height of 12 m, and a stratum boundary is provided at a depth of 8.12 m to separate the upper layer 33 (N value 20) and the lower layer 35 (N value 50), simulating the bearing layer in the actual ground. The material data of the pile 23 and the ground 31 is a bilinear type elastoplastic model in which the secondary gradient changes at the yield point, and elements that can take into account the interaction behavior such as contact and friction between the pile 23 and the ground 31 are incorporated.

[0070] The relationship between the applied load and the pull-out amount when a pull-out load was applied vertically upward to the pile 23 was calculated to determine the pull-out bearing capacity of the pile 23. Note that the pull-out bearing capacity of a typical steel pipe pile is defined as the applied load at the standard pull-out amount, and the standard pull-out amount is defined as 0.1 times the outer diameter of the steel pipe or 0.1 times the outer diameter of the fin. Therefore, in this embodiment, the standard pull-out amount was defined as 0.1 times the outer diameter of the pile body 25, and the applied load at the standard pull-out amount was defined as the pull-out load.

[0071] Furthermore, in this embodiment, the pull-out bearing capacity was obtained when the shape of the fins 27 in the pile 23 was changed. The specifications of the shape and the like of the fins 27 in the pile 23 are shown below (see FIG. 1). Eight fins 27 were provided at equal intervals on the outer peripheral surface of the pile body 25. The vertical length lfv was set to 1, 1.75, and 2.5 times (1D, 1.75D, and 2.5D) the outer diameter D of the pile body 25. The distance lt from the lower end of the pile body 25 to the lower end of the fin 27 was set to 50 mm. The fin width wf was set to 0.25 times the outer diameter of the pile body 25. At this time, the fin outer diameter Df was set to 1.5 times the outer diameter D of the pile body 25. The inclination angle β was set to 0 degrees or 9.46 degrees. The tip angle α of the fin 27 was set to 60 degrees. Furthermore, the fin plate thickness tf was set to 25 mm. In addition, this specification is within the scope of the present invention except for the case where the vertical length lfv is 2.5 times the outer diameter of the pile body 25.

[0072] Fig. 7 shows the relationship between the applied load and the pull-out amount when the vertical length lfv is changed in the pile 23 with the inclination angle β set to 0 degrees. Here, Fig. 7 also shows the reference pull-out amount.

[0073] In general, the guideline for the penetration amount into the bearing layer in the driving pile method is about twice the outer diameter of the pile body, taking into account the strength of the construction machine and the pile body. Therefore, in this embodiment, taking this point into consideration, the penetration amount of the pile into the bearing layer is set to twice the outer diameter of the pile body 3 (i.e., 2D). From FIG. 7, it was confirmed that the pull-out bearing capacity is the highest when the vertical length lfv is short, 1 time (1D) the outer diameter of the pile body 25, which is within the range of the present invention. This is because the upper end of the fin 27 is located deep in the lower layer 35 (bearing layer) due to the short vertical length lfv, and the pull-out bearing capacity is exerted to the maximum extent because the pull-out bearing capacity is exerted on the wider ground. Also, even when the vertical length lfv is 1.75D, which is within the range of the present invention, the upper end of the fin 27 is located in the lower layer 35, so that the pull-out bearing capacity close to that when the vertical length lfv is 1D was obtained. It was revealed that the pull-out bearing capacity is exerted by the resistance of the pull-out bearing capacity exerting ground 13, and therefore the longer the distance between the upper end of the fin and the upper surface of the bearing layer, the greater the effect. On the other hand, when the vertical length lfv is as long as 2.5 times (2.5D) the outer diameter of the pile body 25, which is outside the range of the present invention, the upper end of the fin 27 is not located in the lower layer 35 (bearing layer), and therefore the resistance of the pull-out bearing capacity exerting ground 13 is insufficient, and the pull-out bearing capacity is not fully exerted.

[0074] Fig. 8 shows the relationship between the applied load and the pull-out amount when the vertical length lfv is changed in the pile 23 with the inclination angle β of 9.46 degrees. As in Fig. 7 described above, Fig. 8 also shows the standard pull-out amount based on 0.1 times the outer diameter of the steel pipe.

[0075] From Fig. 8, it was confirmed that even when the fin 27 is inclined with respect to the central axis of the pile body 25, the pull-out bearing capacity is the highest when the vertical length lfv is 1 time (1D) of the outer diameter of the pile body 25, which is within the range of the present invention, as in the case where the inclination angle β is 0 degrees. Also, even when the vertical length lfv is 1.75D, which is within the range of the present invention, the upper end of the fin 27 is located within the lower layer 35, so that a pull-out bearing capacity close to that when the vertical length lfv is 1D is obtained. In other words, it can be confirmed from this embodiment that in order to sufficiently expand the pull-out bearing capacity exerting ground 13 by the effect of the internal friction angle of the ground near the upper end of the fin in order to exert the pull-out bearing capacity, a distance of 0.25D or more from the upper end of the fin to the upper surface of the supporting layer is sufficient. On the other hand, when the vertical length lfv is as long as 2.5 times (2.5D) the outer diameter of the pile body 25, which is outside the scope of the present invention, the upper end of the fin 27 is not located in the lower layer 35 (bearing layer), so the bearing resistance of the pull-out bearing capacity exerting ground 13 is insufficient and the pull-out bearing capacity is not fully exerted. Furthermore, by comparing the results of Fig. 7 and Fig. 8, it was confirmed that when the fin 27 is inclined with respect to the central axis of the pile body 25, the bearing resistance of the pull-out bearing capacity exerting ground 13 becomes larger, and the pull-out bearing capacity is further increased. It is also expected that the compression bearing capacity, which shows the same tendency as the pull-out bearing capacity, will also increase. [Industrial Applicability]

[0076] According to the present invention, it is possible to provide a pile, a pile construction method, a structure, a method for constructing a structure, a method for designing a pile, and a method for manufacturing a pile, which do not require large-scale equipment for construction, are economical and environmentally friendly, and further, are capable of exerting high pull-out support force and high compressive support force even under conditions of low penetration into the supporting layer, and are capable of suppressing the occurrence of construction problems. [Explanation of symbols]

[0077] 1 stake 3 Pile body 5 Fin 11 Ground 13 Ground with pull-out bearing capacity 15 Support layer 21 3D FEM model 23 stake 25 Pile body 27 Finn 31 Ground 33 Upper layer 35 Lower layer

Claims

1. A pile constructed by a driving pile method or a press-in method, in which two or more plate-shaped fins are arranged on the outer peripheral surface of the pile body at the lower end of the pile body, Each of the fins is The vertical length is 0.5 to 1.75 times the outer diameter of the pile body, and the lower limit of the vertical length is set based on the pull-out bearing capacity required for the pile, The inclination angle is set based on the pull-out bearing capacity required for the pile, and is 0 degrees or more and less than 1 degree with respect to the central axis of the pile body; A pile whose lower end position is higher than the lower end position of the pile body and is located at a distance of 50 mm or less from the lower end position of the pile body.

2. A method for constructing a pile by inserting the pile according to claim 1 into ground having a bearing layer, A pile construction method, in which the fin arranged on the pile penetrates the pile so that an upper end of the fin is positioned within the supporting layer.

3. A structure comprising the pile according to claim 1.

4. A method for constructing a structure comprising the piles according to claim 1, comprising the steps of: A method for constructing a structure, comprising the step of driving the pile into ground.

5. A method for designing a pile to be constructed by a driving pile method or a press-in method, in which two or more plate-shaped fins are arranged on the outer peripheral surface of the pile body at the lower end of the pile body, Each of the fins is The vertical length is 0.5 to 1.75 times the outer diameter of the pile body, and the lower limit of the vertical length is set based on the pull-out bearing capacity required for the pile, The inclination angle is set based on the pull-out bearing capacity required for the pile, and is 0 degrees or more and less than 1 degree with respect to the central axis of the pile body; A method for designing a pile, in which the lower end position is set to be higher than the lower end position of the pile body and the distance to the lower end position of the pile body is set to be 50 mm or less.

6. A method for manufacturing a pile constructed by a driving pile method or a press-in method, in which two or more plate-shaped fins are arranged on the outer peripheral surface of the pile body at the lower end of the pile body, Each of the fins is The vertical length is 0.5 to 1.75 times the outer diameter of the pile body, and the lower limit of the vertical length is set based on the pull-out bearing capacity required for the pile, The inclination angle is set based on the pull-out bearing capacity required for the pile, and is 0 degrees or more and less than 1 degree with respect to the central axis of the pile body; A method for manufacturing a pile, in which the lower end position is formed so as to be higher than the lower end position of the pile body and so as to be 50 mm or less away from the lower end position of the pile body.

Images