JP7655342B2 - Pile, pile construction method, structure, structure construction method, pile design method, and pile manufacturing method - Google Patents

Description

The present invention relates to piles, pile construction methods, structures, methods for constructing structures, methods for designing piles, and methods for manufacturing piles.

Steel pipe piles are commonly used in port structures. Depending on the structure and ground conditions, such as piers and wharf support piles, high pull-out bearing capacity is required of steel pipe piles. One method to increase 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 construction space restrictions, the driving pile method using impact hammers and vibro hammers is mainstream, and the rotary pile method, which requires relatively large rotary construction machines, 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 ships. Furthermore, this method is undesirable from the perspective of the port environment, as it uses cement milk.

On the other hand, piles have been proposed that can be constructed using the driving pile method and pressure-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 periphery 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.

JP 2017-95880 A Japanese Utility Model Application Publication No. 3-18238

The steel pipe pile described in Patent Document 1 enhances the pull-out bearing capacity by the peripheral frictional 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 frictional 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 frictional force, so it is expensive in terms of material costs and processing costs and is not economical. 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.

The present invention was made in consideration of the above problems, and its purpose 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 can exert high pull-out support force and high compressive support force even under conditions of low penetration into the supporting layer, and can suppress the occurrence of construction problems.

The pile according to the present invention has two or more plate-shaped fins arranged on the outer periphery 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 to 45 degrees with respect to the central axis of the pile body.

The pile construction method of the present invention involves inserting the pile of the present invention into ground containing a supporting layer, so that the upper end of the fin attached to the pile is positioned within the supporting layer.

The structure according to the present invention is equipped with the pile according to the present invention.

The method for constructing a structure according to the present invention includes a step of driving a pile according to the present invention into the ground.

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 bearing capacity and compressive bearing capacity required of the pile, and then the lower limit of the vertical length is set according to the pull-out bearing capacity and the compressive bearing capacity.

The pile design method of the present invention is to design 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 0.5 to 1.75 times the outer diameter of the pile body and the inclination angle is 0 degrees to 45 degrees with respect to the central axis of the pile body.

The method for manufacturing a pile according to the present invention is for manufacturing 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 the vertical length is 0.5 to 1.75 times the outer diameter of the pile body and the inclination angle is 0 degrees to 45 degrees with respect to the central axis of the pile body.

The piles, pile construction method, structure, structure construction method, pile design method, and pile manufacturing method 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 compression support force even under conditions of low penetration into the supporting layer, thereby suppressing the occurrence of construction problems.

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. FIG. 2 is a conceptual diagram for explaining the behavior of the pull-out bearing capacity exerted when a pull-out load acts on the pile according to the embodiment of the present invention. 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. 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. 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. FIG. 6 shows a three-dimensional FEM model used to verify the pull-out bearing capacity of a pile in the examples. FIG. 7 is a graph showing the relationship between the applied load and the pull-out amount calculated by an analysis of a pile having fins attached parallel to the central axis of the pile body. 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 having fins attached thereto at an angle with respect to the central axis of the pile body.

As shown in Fig. 1, the pile 1 according to the embodiment of the present invention has two or more plate-shaped fins 5 arranged on the outer peripheral surface of the lower end of the pile body 3. Each fin 5 has a vertical length lfv of 0.5 to 1.75 times the outer diameter D of the pile 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 body 3.

Figure 1(a) shows a case where the fin 5 is attached substantially parallel to the central axis of the pile body 3, while Figure 1(b) shows a case where the fin 5 is attached at an angle to the central axis of the pile body 3. "Substantially parallel" here means that the angle with respect to the central axis of the pile body 3 is equal to or greater than 0 degrees and less than 1 degree.

In addition, 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 perimeter of the pile body 3, the spacing between adjacent fins 5 is 1/2 or less of the outer perimeter 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 than 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.

In Figure 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 when the pile is inserted. 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 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.

Before explaining why the fins 5 in the pile 1 of this embodiment are limited as described above, we will explain how the pile 1 with the fins 5 exerts its pull-out support force when a pull-out load acts on it.

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

The pull-out bearing capacity increases as the area of the pull-out bearing capacity ground 13 that resists when the pile 1 is pulled out becomes wider. Therefore, compared to the spiral ribs used in the steel pipe piles disclosed in the aforementioned Patent Document 1, the use of fins 5 that protrude from the surface of the pile body 3 by a large amount in the radial direction of the pile 1 increases the area of the pull-out bearing capacity ground 13, and a high effect can be achieved. Furthermore, the presence of the fins 5 not only increases the pull-out bearing capacity, but also improves the compressive bearing capacity by expanding the compressive bearing capacity ground (not shown) 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.

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 explained.

(Number of fins (minimum))
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 higher the force transmitted from the fins 5 to the ground, and the higher the effect of the internal friction angle of the ground in the pull-out bearing capacity exerting ground 13 near the upper end of the fin, 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 lower 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 lower end of the fins 5 when the pile 1 is pushed in. Therefore, the number of fins 5 is determined based on the workability, pull-out bearing capacity, and compressive bearing capacity 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.

(Vertical length)
The vertical length lfv is 0.5 to 1.75 times the outer diameter D of the pile 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 body 3, as shown in FIG.

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

In general, the ground that requires the pile 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, pull-out and compressive bearing capacity due to 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 mentioned above, the compressive bearing capacity exerting ground spreads near the lower end of the fin 5 due to the effect of the internal friction angle of the ground 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. Also, to ensure that the upper end of the fin 5 is positioned within the support layer 15, it is desirable to have the fin length lf as short as possible without impairing performance.

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 steel pipe pile body 3, and the workability of installing the fin 5 deteriorates. Since the size of the jig changes depending on the outer diameter of the pile 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 body 3 so that the fin length lf is not too short.

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

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 for practical use, 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.

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

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

When the inclination angle β is between 0 degrees and 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 between 1 degree and 45 degrees (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, reducing the penetration resistance of the fins 5.

As shown in FIG. 2, the pull-out bearing capacity of the pile 1 is exerted by the resistance of the pull-out bearing 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 bearing capacity exerting ground 13 near the top end of the fin, thereby increasing the pull-out bearing capacity. On the other hand, if the inclination angle β is large, the resistance force during penetration increases, and construction efficiency decreases. For this reason, the inclination angle β must be considered not only in terms of the pull-out bearing capacity but also in terms of the penetration resistance. The relationship between the inclination angle and the penetration resistance will be explained below.

Figure 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 (Figure 5(a)) and 60 degrees (Figure 5(b)). Note that the pile 1 and pile body 3 are not shown in Figure 5.

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") acts on the pile body 3 around its central axis. 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. This 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 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 body 3. Therefore, the fin thrust force becomes a rotational force on the pile body 3.

Comparing the case where the inclination angle β is 30 degrees (Figure 5(a)) with the case where it is 60 degrees (Figure 5(b)), the fin thrust force is smaller when the inclination angle β is large at 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 large.

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 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 body 3.

In this embodiment, the lower limit of the inclination angle β is set to 0 degrees or more, but since the pile body 3 is rotated while being inserted during construction, and this reduces the resistance to insertion, it is preferable to set the inclination angle β to 1 degree or more.

Next, we will explain the selection conditions "fin lower end position," "fin upper end position," "fin width," "number of fins (upper limit)," and "fin spacing." 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.

(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.

(Fin top position)
The position of the upper end of the fin 5 is preferably set to be not more than twice the outer diameter D of the pile body 3 from the lower end of the pile body 3 (see Fig. 1). The position of the upper end of the fin 5 is set 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.

(Fin width)
The fin width wf is preferably at least twice the fin plate thickness tf. The fin width wf is preferably at most 1/2 the outer diameter of the pile body 3 (see FIG. 1). Here, the fin width wf is the circumferential length of the fin at 1/2 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. Therefore, the larger the amount of protrusion from the surface of the pile body 3, the wider the range of the pull-out bearing capacity exerting ground 13, and the greater the effect.

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, from the viewpoint of workability, when the outer diameter of an imaginary circle passing through the outermost edge of the fin 5 is the fin outer diameter Df (see Figure 1), it is preferable that the fin outer diameter Df be up to about twice the outer diameter of the pile body 3.

(Number of fins (maximum) and spacing)
The number of fins 5 to be 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 of the interval is preferably 1/2 or less. Here, the interval between adjacent fins 5 is the distance between the center of the thickness of the fins 5 in the circumferential direction of the pile main body 3.

The reason for setting the number and spacing of the fins 5 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 around the periphery of the pile body 3, the fin spacing is 1/2 the periphery of the pile body 3. On the other hand, when a steel pipe is used for the pile body 3, the fins 5 are generally attached to the pile body 3 later by welding or the like, so considering the required work space, it is preferable to set the upper limit of the number of fins 5 to 16 or less. Then, when 16 fins 5 are attached at equal intervals around the periphery of the pile body 3, the spacing between adjacent fins 5 is 1/16 of the periphery of the pile body 3. Note that within the above range, the more fins 5 are used, the more expensive it is, but the larger the bearing area at the top of the fins 5 is, so the load transmission force to the ground is increased and the pull-out bearing force is improved.

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

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.

As shown in FIG. 3, the most preferable use of the pile 1 according to this embodiment is to penetrate into the supporting layer where the bearing capacity is maximized. The present invention is not limited to such use, and can also be applied to friction piles that do not penetrate into the supporting layer and to inclined piles. Furthermore, the pull-out bearing capacity and the push-in bearing capacity can be improved compared to general steel pipe piles (also called bare pipes).

The fins 5 may be attached at unequal intervals within the above-mentioned fin spacing 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 they may also 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.

The pile 1 according to this embodiment is not limited to steel pipe piles in which steel plate fins are attached to a steel pipe pile body, but can also be applied to concrete piles. In the case of concrete piles, the fins can also be made from concrete using a formwork.

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. This construction method allows the pile 1 according to the present embodiment to be penetrated into the ground where a 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.

Furthermore, the pile 1 according to the embodiment of the present invention can be applied to a construction method in which the pile is driven into the ground using a driving pile method or a press-in method. Furthermore, the pile 1 according to the embodiment of the present invention is highly suitable as a pile to be used with these construction methods. This is for the following reasons.

In general, 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 low resistance to vertical loads and is suitable for pile driving or press-in construction methods, which use vertical loads. However, in order to minimize resistance force during penetration, care must be taken to avoid rotational constraints during construction.

Next, an example of the pile 1 according to this 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 relatively increase the vertical load due to its own weight, 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.

The pile 1 according to this embodiment may also be used in a structure equipped with the pile 1 according to this embodiment.

As mentioned above, the piles of the present invention are particularly suitable for structures such as port structures, offshore wind power foundations, building foundations, bridge pier foundations, and bedrock anchors.

The pile 1 according to this embodiment can also be used in a method for constructing a structure that includes a process of driving the pile 1 into the ground.

The pile 1 according to this embodiment can also be used in a method for constructing a structure that includes the construction method for the pile 1 described above.

In the above explanation, the pile was 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 pile design method for designing a pile having two or more plate-shaped fins arranged on the outer periphery 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.

The order of each component of the pile design method of the present invention is not limited to the order described above. In addition, the preferred ranges of each selection condition, such as the spacing between adjacent fins, the bottom and top end positions of the fins, and the fin width, are the same as those described for the pile 1 in this embodiment, as described above. Therefore, it is preferable to set each of these selection conditions within the preferred ranges described for the pile 1 as necessary.

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.

After that, 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 workability is prioritized, the vertical length lfv is increased within the allowable range, and if economy is prioritized, the vertical length lfv is decreased within the allowable range.

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

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

Furthermore, the pile 1 according to this embodiment is manufactured by the following manufacturing method. This is a method for manufacturing 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 the vertical length is 0.5 to 1.75 times the outer diameter of the pile body and the inclination angle is 0 degrees to 45 degrees with respect to the central axis of the pile body.

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 manufacturing method of pile 1 according to this embodiment, the preferred ranges of the selection conditions for the spacing between adjacent fins 5, the lower end position and upper end position of fin 5, and the fin width are the same as those described for pile 1 according to this embodiment. Therefore, it is preferable to form each of these selection conditions within the preferred ranges described for pile 1 as necessary.

[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.

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 an actual ground. The material data of the pile 23 and the ground 31 is a bilinear type elastoplastic model with a secondary gradient that changes at the yield point, and elements that can take into account interactive behavior such as contact and friction are incorporated between the pile 23 and the ground 31.

Then, 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 the applied load at the standard pull-out amount, and the standard pull-out amount is 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 is 0.1 times the outer diameter of the pile body 25, and the applied load at the standard pull-out amount is the pull-out load.

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. This specification is within the scope of the present invention, except when the vertical length lfv is 2.5 times the outer diameter of the pile body 25.

Figure 7 shows the relationship between the load and the pull-out amount when the vertical length lfv is changed for pile 23 with an inclination angle β of 0 degrees. Here, Figure 7 also shows the standard pull-out amount.

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 a 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 is close to that when the vertical length lfv is 1D. Since the pull-out bearing capacity is exerted by the resistance of the pull-out bearing capacity exerting ground 13, it was revealed that the longer the distance between the top end of the fin and the top surface of the bearing layer, the more effective it is. 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 top end of the fin 27 is not located in the lower layer 35 (bearing layer), so the resistance of the pull-out bearing capacity exerting ground 13 is insufficient and the pull-out bearing capacity is not fully exerted.

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

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) 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 a pull-out bearing capacity close to that when the vertical length lfv is 1D is obtained. In other words, it can be confirmed that in order to sufficiently expand the pull-out bearing capacity exerting ground 13 near the upper end of the fin by the effect of the internal friction angle of the ground 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 in this embodiment. 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, when comparing the results of Figures 7 and 8, it was confirmed that when the fin 27 is inclined relative 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 can also be expected that the compression bearing capacity, which shows the same tendency as the pull-out bearing capacity, will also increase.

The present invention provides piles, pile construction methods, structures, structure construction methods, pile design methods, and pile manufacturing methods that do not require large-scale equipment for construction, are economical 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.

Reference Signs List 1 Pile 3 Pile body 5 Fin 11 Ground 13 Ground exerting pull-out bearing capacity 15 Bearing layer 21 3D FEM model 23 Pile 25 Pile body 27 Fin 31 Ground 33 Upper layer 35 Lower layer

Claims (6)

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. 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. A structure comprising the piles according to claim 1. 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. 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. 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.

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