CN116724159A - Pile, method for constructing pile, structure, method for constructing structure, method for designing pile, and method for manufacturing pile - Google Patents

Abstract

In the pile (1), two or more plate-shaped fins (5) are arranged on the outer peripheral surface of a pile body (3) at the lower end of the pile body (3), the vertical length of each fin (5) is 1-1.75 times or less the outer diameter of the pile body (3), and the inclination angle is 0-45 degrees relative to the central axis of the pile body (3).

Description

Pile, method for constructing pile, structure, method for constructing structure, method for designing pile, and method for manufacturing pile

Technical Field

The present invention relates to a pile, a method of constructing a pile, a structure, a method of constructing a structure, a method of designing a pile, and a method of manufacturing a pile.

Background

In port structures, steel pipe piles are often used. Depending on the structure such as wharf and quay anchor piles and the foundation conditions, a high pulling load capacity is required for the steel pipe piles. As a method for improving the drawing load capacity, there is a rotary pile method in which a vane is attached to the tip of a steel pipe pile. In the harbor field, pile driving methods using a hammer or a vibrator are mainly used due to the construction space, and a rotary pile method requiring a relatively large rotary construction machine is not applied. As other methods, there are the following: the steel pipe pile is penetrated by spraying water and vibrating, and the cement slurry spraying is switched to the ground to integrate the steel pipe pile and the foundation. However, this method is uneconomical in offshore construction requiring a ship because of the large equipment required for water spraying and cement slurry jetting. Also, since this method uses cement slurry, it is also undesirable in terms of the environment of the port.

On the other hand, the following piles are proposed: the pile driving method and the pile driving method, which are mainstream in the port area, can be performed without using water spraying or cement slurry spraying, and a high drawing load capacity can be exhibited. For example, there have been proposed a steel pipe pile in which a plurality of spiral ribs are formed in a spiral shape on the outer peripheral surface on the lower side of a steel pipe (see patent document 1), and a steel pipe pile in which a plate-like protrusion is fixed along the axial direction of a pile body made of a steel pipe (see patent document 2).

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2017-95880

Patent document 2: japanese unexamined patent publication No. 3-18238

Disclosure of Invention

Problems to be solved by the invention

The steel pipe pile described in patent document 1 improves the drawing load capacity by using the circumferential friction of the helical rib. However, the steel pipe pile described in patent document 1 is uneconomical because it requires spiral ribs to be formed in a spiral shape on the outer peripheral surface of the steel pipe. On the other hand, the steel pipe pile described in patent document 2 increases the drawing load capacity by the circumferential friction or load capacity of the plate-like protruding body. However, the steel pipe pile described in patent document 2 requires a relatively large protrusion to be formed in order to increase the circumferential friction, and therefore it is uneconomical to cost the pile from the viewpoints of material cost and processing cost. In order to exert a sufficient drawing load bearing capacity, it is necessary to penetrate the front end portion of the pile into the load bearing layer more than usual in order to penetrate the entire protrusion into the load bearing layer. Therefore, the construction scale becomes large, and there is a possibility that construction failures such as restrictions in construction space, noise or vibration, poor penetration, and breakage of the pile body may occur.

The present invention has been made in view of the above problems, and an object thereof is to provide a pile, a method of constructing a pile, a structure, a method of constructing a structure, a method of designing a pile, and a method of manufacturing a pile, as follows: the construction does not require huge equipment, is excellent in economical efficiency and environmental aspects, and can exert high drawing bearing capacity and high press-in bearing capacity even under the condition of less penetration into the bearing layer, thereby being capable of inhibiting the occurrence of construction faults.

Means for solving the problems

In the pile according to the present invention, two or more plate-like fins are arranged on the outer peripheral surface of the pile body at the lower end portion 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, and an inclination angle of 0 to 45 degrees with respect to the central axis of the pile body.

The pile of the present invention is inserted into a foundation having a bearing layer, and the upper ends of the fins disposed on the pile are inserted into the bearing layer.

The structure of the present invention is provided with the pile of the present invention.

The construction method of the structure of the present invention includes a step of penetrating the pile of the present invention into a foundation.

The pile design method of the present invention sets the inclination angle based on the required drawing load bearing capacity and pressing load bearing capacity of the pile, and thereafter sets the lower limit value of the vertical length according to the drawing load bearing capacity and the pressing load bearing capacity.

In the method for designing a pile according to the present invention, a pile is designed in which two or more plate-like fins are arranged on the outer peripheral surface of a pile body at the lower end portion of the pile body, and each of the fins is set as follows: 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.

The method for manufacturing a pile according to the present invention is a method for manufacturing a pile in which two or more plate-like fins are arranged on an outer peripheral surface of a pile body at a lower end portion of the pile body, each of the fins being formed as follows: 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.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the pile, the pile construction method, the structure construction method, the pile design method, and the pile manufacturing method of the present invention, the pile construction does not require a huge apparatus, and the pile construction method is excellent in economical efficiency and environmental aspects, and can exhibit a high pull-out load bearing capacity and a high press-in load bearing capacity even under a condition of less penetration into the bearing layer, and can suppress occurrence of construction failure.

Drawings

Fig. 1 is a conceptual diagram illustrating a pile according to an embodiment of the present invention, (a) shows a case where fins are mounted substantially parallel to a central axis of a pile body, and (b) shows a case where fins are mounted obliquely to the central axis of the pile body.

Fig. 2 is a conceptual diagram illustrating the behavior of the drawing load when a drawing load acts on the pile according to the embodiment of the present invention.

Fig. 3 is a diagram showing a relationship between a penetration position of a lower end portion of a pile and a bearing layer according to an embodiment of the present invention.

Fig. 4 is a conceptual diagram of construction in the case where piles according to an embodiment of the present invention are rotatably driven by vertical load.

Fig. 5 is a conceptual diagram showing forces acting on the fins when the pile according to the embodiment of the present invention is rotated and penetrated by a vertical load.

Fig. 6 is a diagram showing a three-dimensional FEM model used for verification of the pullout bearing capacity of the stake in the embodiment.

Fig. 7 is a graph showing a relationship between a load and a pulling amount calculated by analysis of a pile in which fins are attached parallel to a central axis of a pile body.

Fig. 8 is a graph showing a relationship between a load and a pulling amount calculated by analysis of a pile to which fins are attached obliquely to a central axis of a pile body.

Detailed Description

As illustrated in fig. 1, a pile 1 according to an embodiment of the present invention has two or more plate-like fins 5 disposed on the outer peripheral surface of a pile body 3 at the lower end portion of the pile body 3. The vertical length lfv of each fin 5 is 0.5 to 1.75 times the outer diameter D of the pile body 3, and the inclination angle β (see fig. 1 (b)) is 0 to 45 degrees with respect to the central axis of the pile body 3.

Fig. 1 (a) shows a case where the fins 5 are mounted substantially parallel to the central axis of the pile body 3, and fig. 1 (b) shows a case where the fins 5 are mounted obliquely to the central axis of the pile body 3. The term "substantially parallel" as used herein means that the angle with respect to the central axis of the pile body 3 is 0 degrees or more and less than 1 degree.

The pile 1 according to the embodiment of the present invention satisfies one or more of the conditions that the interval between adjacent fins 5 is 1/16 or more of the outer circumferential length of the pile body 3, the interval between adjacent fins 5 is 1/2 or less of the outer circumferential length of the pile body 3, the lower end position of the fins 5 is 50mm or less from the lower end of the pile body 3, the upper end position of the fins 5 is 2 times or less of 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 of 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, as required.

In fig. 1, a distance (50 mm or less) from the lower end of the pile body 3 to the lower end of the fin 5 is not shown. Alpha shows the front end angle of the fin 5. Here, the tip angle α of the fin 5 is a predetermined angle determined according to the relation between the workability and the bearing capacity required for the pile 1. The tip angle α is preferably 60 degrees or less, depending on the effect of reducing the shearing force applied to the fin welded portion by the bearing resistance of the fin plate thickness portion at the time of pile penetration. The fin length lf is a distance between the lower end and the upper end of the fin 5 on the side where the pile body 3 is attached, and the fin horizontal length lfh is a length in the direction perpendicular to the central axis of the pile body 3 at the lower end and the upper end of the fin 5, and is determined at the center of the plate thickness of the fin 5.

Before explaining the reason why the fins 5 are limited in the pile 1 of the present embodiment as described above, the drawing load acts when a drawing load acts on the pile 1 provided with the fins 5.

Fig. 2 is a conceptual diagram showing the behavior of the pulling load when the pulling load acts on the pile 1 shown in fig. 1 (a). In fig. 2, the drawing load bearing capacity exertion foundation 13 represents a foundation that exerts drawing load bearing capacity so as to resist when the stake 1 is drawn. The drawing load capacity exerts the effect that the foundation 13 widens near the upper ends of the fins due to the internal friction angle of the foundation, and when separated by a certain distance, the effect of widening becomes smaller, forming a slip plane in a cylindrical shape. In addition, the stronger the foundation, the higher the widening effect by the internal friction angle of the foundation becomes.

The larger the range of the pulling load capacity against which the pile 1 is pulled out, the larger the pulling load capacity becomes. Therefore, by using the fins 5 having a larger projection amount in the radial direction of the pile 1 from the surface of the pile body 3, the drawing load bearing capacity can be exerted over a wide range, and a higher effect can be exerted, as compared with the helical rib used in the steel pipe pile disclosed in the above-mentioned patent document 1. Further, since the fins 5 are present, not only the drawing load bearing capacity is improved, but also the press-in load bearing capacity is improved by widening the press-in load bearing capacity due to the effect of the internal friction angle of the foundation (not shown) in the vicinity of the lower end of the fins 5 when the pile 1 is press-fitted.

Next, the reason for limiting the fins 5 in the pile 1 according to the present embodiment will be described with reference to fig. 1 to 5. First, the "number of fins (lower limit)", "vertical length", and "inclination angle" as conditions necessary for obtaining the effects of the present invention will be described.

(number of fins (lower limit))

The number of fins 5 is two or more. As shown in fig. 2, the pullout load capacity of the pile 1 is exerted by the pullout load capacity exerting the resistance of the foundation 13. The larger the number of fins 5, the higher the force transmitted from the fins 5 to the foundation, and the higher the drawing load near the upper ends of the fins, the higher the effect of the internal friction angle of the foundation 13, and the higher the drawing load. Further, since the fin 5 is present, not only the drawing load capacity is improved, but also the press-in load capacity is improved at the same time because the press-in load capacity is widened by the effect of the internal friction angle of the foundation in the vicinity of the lower end of the fin 5 when the pile 1 is press-in. Further, since the fins 5 are present (i.e., the fins 5 are one or more), as described above, not only the drawing load bearing capacity but also the press-in load bearing capacity is improved. As described above, the reason is that, when the pile 1 is pressed, the bearing force is pressed near the lower ends of the fins 5 due to the effect of the internal friction angle of the foundation, and the foundation is widened. Therefore, the number of fins 5 is determined according to the workability, drawing load capacity, and press-in load capacity required for the pile 1. In the present embodiment, two or more piles 1 are provided to stably penetrate 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, as shown in fig. 1, the vertical length lfv is a distance between the lower end and the upper end of the fin plate thickness center in the central axis direction of the pile body 3.

The reason why the vertical length lfv satisfies the above range will be described with reference to fig. 3. Fig. 3 is a diagram schematically showing the relationship between the penetration position in the vertical direction of the pile 1 and the bearing layer 15 in the case where the pile 1 penetrates the foundation 11 having the bearing layer 15 below. Fig. 3 (a) shows a case where the upper ends of the fins 5 are located in the carrier layer 15, and fig. 3 (b) shows a case where the upper ends of the fins 5 are not located in the carrier layer 15.

In general, a foundation requiring improvement in the pulling load bearing capacity and the pressing load bearing capacity for piles is a foundation in which a load bearing layer (hard foundation) exists below a soft foundation having a thicker layer thickness. The reason for this is that in a soft foundation, the pulling load capacity and the pressing load capacity due to the circumferential friction between the pile body and the foundation cannot be expected. In the pile 1 of the present embodiment, the fin 5 increases not only the drawing load bearing capacity but also the press-in load bearing capacity. As described above, the reason is that, when the pile 1 is pressed, the bearing force is pressed near the lower ends of the fins 5 due to the effect of the internal friction angle of the foundation, and the foundation is widened. On the other hand, in the pile 1 of the present embodiment, the pullout bearing force is exerted by the pullout bearing force exerting the resistance of the foundation 13. Therefore, in order to exert the drawing bearing force on the foundation 13 in a sufficiently wide range, it is preferable that the upper ends of the fins 5 are positioned in the bearing layer 15, and the bearing layer 15 is a firm foundation having a large internal friction angle. In addition, in order to reliably locate the upper ends of the fins 5 in the carrier layer 15, the fin length lf is preferably short within a range that does not impair performance.

However, when the fin length lf is too short, it is difficult to temporarily fix the fin 5 by a jig when the fin 5 is welded to the pile body 3 of the steel pipe, and workability in mounting the fin 5 is deteriorated. Since the size of the jig varies according to the outer diameter of the pile body 3, in the pile 1 of the present embodiment, the vertical length lfv is set to be 0.5 times or more the outer diameter of the pile body 3 in order to make the fin length lf too short.

On the other hand, when the fin length lf is too long under the same construction conditions, as shown in fig. 3 (b), the upper ends of the fins 5 do not penetrate the bearing layer 15, and a sufficient drawing bearing force cannot be exerted.

In addition, the penetration amount of the pile 1 into the bearing layer 15 can be increased according to the condition of the bearing layer 15. However, there are many cases where the penetration of the driven pile 1 is stopped before reaching the depth expected in practical use, and if the fin length lf is inadvertently increased, there is a high risk that the upper end of the fin 5 is not located in the bearing layer 15. In general, the standard of the penetration amount into the bearing layer in the pile driving method is set to about 2 times the outer diameter of the pile body in consideration of the strength of the construction machine and the pile body. Therefore, in the pile 1 of the present embodiment, in order to stably penetrate the fins 5 into the bearing layer 15, the upper ends of the fins 5 are positioned in the bearing layer 15, the pull-out bearing force is exerted against the foundation 13 with a sufficient pull-out bearing force, and the vertical length lfv is set to 1.75 times or less the outer diameter D of the pile body 3.

(inclination angle)

The inclination angle β is 0 to 45 degrees with respect to the center axis of the pile body 3 (see fig. 1). Here, the inclination angle β is an angle with respect to the center axis of the pile body 3 when the point at the 1/2 position of the fin length lf is the rotation center.

The reason why the inclination angle β is set to the above range is as follows. Fig. 4 shows a construction concept when pile 1 having inclination angle β of 1 to 45 degrees is vertically penetrated into foundation 11.

When the inclination angle β is 0 degrees or more and less than 1 degree (fig. 1 a), the fin 5 (vertical fin) is formed substantially parallel to the central axis of the pile body 3, and thus the vertical penetration is the same as that of a general steel pipe pile. On the other hand, when the inclination angle β is 1 to 45 degrees (fig. 1 b), the fins 5 (inclined fins) inclined with respect to the central axis of the pile body 3 are formed, so that when a vertical load is applied to the pile 1, soil is pushed out between the fins 5 in the ground (black arrow in fig. 4), and the pile 1 is inserted while rotating and is constructed. That is, when a vertical load is applied to the pile 1 to which the fins 5 are attached with respect to the central axis of the pile body 3, the pile body 3 rotates, whereby penetration resistance by the fins 5 can be alleviated.

As shown in fig. 2, the pullout load capacity of the pile 1 is exerted by the pullout load capacity exerting the resistance of the foundation 13. The larger the inclination angle β is, the higher the force transmitted from the fin 5 to the foundation becomes, and the higher the drawing load near the upper end of the fin becomes, the higher the effect of the internal friction angle of the foundation 13 becomes, and the higher the drawing load becomes. On the other hand, when the inclination angle β is large, the resistance at the time of penetration becomes large, and the construction efficiency becomes poor. Therefore, regarding the inclination angle β, not only the drawing bearing capacity but also penetration resistance needs to be considered. The relationship between the inclination angle and penetration resistance will be described below.

Fig. 5 shows forces acting on the fins 5 when the pile 1 is rotated and penetrated into the foundation 11 by vertical load, in the case where the inclination angle β is set to 30 degrees (fig. 5 (a)) and 60 degrees (fig. 5 (b)). In fig. 5, the pile 1 and the pile body 3 are not shown.

When a vertical load is applied to the pile and the pile penetrates the foundation 11, vertical resistance acts on the fins 5 from the foundation 11, and a rotational force (referred to as "fin thrust force") that rotates the pile body 3 about the central axis acts. Specifically, the vertical force component against the fins 5 is defined as the vertical direction of the foundation 11 and the direction perpendicular to the vertical direction. The component force in the direction perpendicular to the vertical direction corresponds to "fin pushing force". In fig. 5, the vertical direction of the foundation 11 coincides with the axial direction of the pile body 3, and the direction orthogonal to the vertical direction of the foundation 11 coincides with the tangential direction with respect to the outer periphery of the pile body 3. Therefore, the fin thrust force becomes a rotational force of the pile body 3.

Here, when the inclination angle β is 30 degrees (fig. 5 (a)) and 60 degrees (fig. 5 (b)) are compared, the fin thrust force is reduced when the inclination angle β is 60 degrees larger. In this way, when the inclination angle β is excessively large, the propulsive force becomes small, and as a result, the penetration resistance becomes large.

Therefore, in the present embodiment, in order to prevent the proportion of fin thrust force (rotational force of the pile body 3) against vertical load from being significantly reduced, the pile 1 can be inserted without losing the rotational force of the pile body 3, and the inclination angle β is set to 45 degrees or less.

In the present embodiment, the lower limit value of the inclination angle β is set to 0 degrees or more, and the inclination angle β is preferably set to 1 degree or more in order to ease penetration resistance while rotating the pile body 3 during construction.

Next, the "fin lower end position", "fin upper end position", "fin width", "number of fins (upper limit)" and "fin interval" as selection conditions will be described. These selection conditions can be set as needed according to the use of the pile, the purpose of the pile construction, the foundation and the bearing layer to be penetrated, and the like.

(position of the lower end of the Fin)

The lower end position of the fin 5 is preferably set so that the distance lt from the lower end of the pile body 3 to the lower end of the fin 5 is 50mm or less (see fig. 1). The closer the mounting position of the fin 5 is to the lower end of the pile body 3, the more preferable this is, taking into consideration workability of the lower end of the pile body 3, for example, weldability when the fin 5 is mounted to the pile body 3 in the pile body 3 made of steel pipe.

(position of the upper end of the Fin)

The upper end position of the fin 5 is preferably 2 times or less the outer diameter D of the pile body 3 from the lower end of the pile body 3 (see fig. 1). As shown in fig. 3 (a), the upper end position of the fin 5 is set from the viewpoint of stably penetrating the fin 5 into the carrier layer 15 and positioning the upper end of the fin 5 in the carrier layer 15.

(Fin width)

The fin width wf is preferably 2 times or more the fin thickness tf. The fin width wf is preferably 1/2 or less of the outer diameter of the pile body 3 (see fig. 1). Here, as shown in fig. 1, the fin width wf refers to the length in the fin circumferential direction at the 1/2 position of the fin length lf. The larger the range of the pulling load capacity against which the pile 1 is pulled out, the larger the pulling load capacity becomes. Therefore, the larger the protruding amount from the surface of the pile body 3, the larger the range of the pullout bearing capacity to exert the foundation 13, and the higher the effect can be exerted.

The lower limit of the fin width wf takes into account the mountability of the fins 5 to the pile body 3. Regarding the upper limit of the fin width wf, when the outer diameter of the virtual circle passing through the outermost edge of the fin 5 is the fin outer diameter Df (see fig. 1), the fin outer diameter Df is preferably up to about 2 times the outer diameter of the pile body 3 from the viewpoint of workability.

(number of fins (upper limit) and interval)

The number of mounting fins 5 is preferably 16 or less. Further, as a lower limit, the interval between adjacent fins 5 is preferably 1/16 or more of the outer diameter D of the pile body 3. The upper limit is preferably 1/2 or less. Here, the interval between adjacent fins 5 is set to be the distance between the plate thickness centers of the fins 5 in the outer circumferential direction of the pile body 3.

The reason why the number of fins 5 and the intervals are set to the above-described range is as follows. In order to stably penetrate the pile 1 in the axial direction, two fins are required at the minimum, and when the two fins 5 are installed at equal intervals in the outer circumferential direction of the pile body 3, the fin interval becomes 1/2 of the outer circumferential length of the pile body 3. On the other hand, in the case where steel pipes are used for the pile body 3, the upper limit of the number of fins 5 to be attached is set to 16 or less in consideration of the required working space, since the fins 5 are generally attached to the pile body 3 by welding or the like. Then, when 16 fins 5 are mounted at equal intervals in the outer circumferential direction of the pile body 3, the interval between adjacent fins 5 becomes 1/16 of the outer circumferential length of the pile body 3. If the number of fins 5 is larger within the above range, the cost is increased, but the load-bearing area of the upper end of the fins 5 is increased, so that the load-transmitting force to the foundation is increased and the pullout load-bearing force is increased.

As described above, according to the pile 1 of the embodiment of the present invention, even under the condition of less penetration into the bearing layer, a high drawing bearing force and a high press-in bearing force can be exhibited. Therefore, the force for penetrating the bearing layer more can be smaller, and the machinery used in the construction can be miniaturized. This can provide a pile which can suppress construction failures such as restrictions in construction space, noise and vibration, poor penetration, and breakage of the pile body, and which is excellent in workability, economy, and environmental aspects.

The pile 1 according to the embodiment of the present invention can be preferably applied to a port structure requiring high drawing load bearing capacity and high pressing load bearing capacity. The harbor structure referred to herein means a wharf, a quay anchor, etc. In addition to port structures, the present invention can be similarly applied to offshore wind foundations, building foundations, pier foundations, anchor-on-rock foundations, and the like. This is because these structures may require a high pulling load bearing capacity and a high pressing load bearing capacity.

As shown in fig. 3, the most preferable mode of use of the pile 1 according to the present embodiment is to penetrate the bearing layer that exhibits the maximum effect of the bearing capacity. The present invention can be applied to friction piles which do not penetrate into the bearing layer or to inclined piles without being limited to this manner of use. Further, the drawing load bearing capacity and the press-in load bearing capacity can be improved with respect to a general steel pipe pile (also referred to as a blank pipe).

The fins 5 may be installed at unequal intervals if the intervals between the fins are within the range described above. The fins 5 are not necessarily installed axisymmetrically with respect to the central axis of the pile body 3, and may be installed asymmetrically by appropriate design and construction management. The fin 5 shown in fig. 1 is 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. Further, although the fins may be attached to the pile head, it is preferable not to attach the fins to the pile head because the rotation of the pile generated during the construction is hindered and the foundation is disturbed. When the fins are substantially parallel, rotation of the pile may occur due to the state of the foundation or the manner of applying the load.

The pile 1 according to the present embodiment is not limited to a steel pipe pile in which steel plate fins are attached to a pile body made of steel pipe, but may be applied to a concrete pile. In the case of concrete piles, the fins may be made of concrete for the forming frame.

In the above description, the pile 1 according to the embodiment of the present invention is used in a construction method in which the upper ends of the fins 5 disposed at the lower end portion of the pile body 3 are located in the bearing layer. With this construction method, the pile 1 according to the present embodiment can be inserted into a foundation in which a bearing layer is present. In this case, the construction method for penetrating the pile 1 to be used into the foundation is not particularly limited. Known, known or unknown methods of construction of piles can be used.

Further, as for the pile 1 according to the embodiment of the present invention, a construction method of penetrating the foundation by a pile driving method or a pile driving method can be applied. The pile 1 according to the present embodiment is also suitable as a pile used in these construction methods. This is based on the following reasons.

In general, the smaller the resistance generated when a load is applied to a pile during construction, the higher the workability. Since the inclination angle β (see fig. 1 (b)) of the pile 1 of the present embodiment is relatively small, the pile has a small resistance to vertical load, and is therefore suitable as a pile driving method or a pile driving method for construction by vertical load. However, in order to minimize the resistance at the time of penetration, care must be taken not to restrict the rotational direction at the time of construction.

Next, an example of construction by a pile driving method and an example of construction by a pressing method will be described with respect to the pile 1 of the present embodiment. First, in the pile driving method, a hammer such as a hammer is dropped to apply a striking load to a pile head or the pile is vibrated, so that the strength of the foundation is temporarily reduced, and a vertical load due to its own weight is relatively increased to penetrate the pile. On the other hand, in the case of the press-in method, the pile is inserted by applying a static press-in load to the pile head in the vertical direction. In the case of using these methods, it is also more preferable to penetrate the pile into the foundation so that the upper ends of the fins 5 disposed at the lower end portion of the pile body 3 are positioned in the bearing layer.

The structure provided with the pile 1 according to the present embodiment may be a structure using the pile 1 according to the present embodiment.

Here, as described above, the pile of the present invention is particularly suitable for a harbor structure, an offshore wind foundation, a building foundation, a pier foundation, a rock anchor, or the like in a structure.

The pile 1 according to the present embodiment can be used in a construction method of a structure including a step of penetrating the pile 1 into a foundation.

The pile 1 according to the present embodiment can also be used in a construction method of a structure including the above-described construction method of the pile 1.

In the above description, the pile 1 according to the present embodiment is designed by the following design method, as an object of the invention. A pile design method for designing a pile in which two or more plate-like fins are arranged on the outer peripheral surface of a pile body at the lower end portion of the pile body, wherein each fin is set as follows: 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.

The order of the constituent elements of the pile design method according to the present invention is not limited to the above-described order. The appropriate ranges of the selection conditions such as the interval between adjacent fins, the lower end position and upper end position of the fins, and the fin width are the same as those described above for the pile 1 according to the present embodiment. Therefore, these selection conditions are preferably set as necessary within the appropriate ranges described for pile 1.

The pile 1 according to the present embodiment is also designed by the following design method. First, the pile 1 of the present embodiment is set as a target drawing load bearing capacity. Next, the inclination angle β and the upper limit of the fin number are set according to the drawing load capacity required for the stake 1. This is because the inclination angle β and the upper limit of the fin number have a large influence on the drawing load capacity. When these conditions are set, the inclination angle β is reduced and the number of fin pieces is increased within an allowable range with priority given to workability. On the other hand, in the case of the priority economy, the inclination angle β is increased within the allowable range, and the number of fin pieces is reduced within the allowable range.

After that, the inclination angle β and the fin number are determined, and then, the lower limit value of the vertical length lfv is set according to the drawing load capacity required for the stake 1. When determining the vertical length lfv, the vertical length lfv is increased within the allowable range in the case of priority workability, and the vertical length lfv is decreased within the allowable range in the case of priority economical efficiency.

In the method of designing the pile 1 according to the present embodiment, it is preferable that the fin width wf is set in accordance with the drawing load capacity required for the pile 1 in addition to the vertical length lfv. When determining the fin width wf, in the case of the workability of the priority 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, in the case of the priority economy, the fin width wf is increased, and the vertical length lfv is reduced within the allowable range.

In the method of designing the pile 1 according to the present embodiment, the "allowable range" may be set in accordance with the drawing load capacity required for the pile 1, or may be set within the range of each condition of the fins 5 described in the pile 1 according to the present embodiment.

The pile 1 of the present embodiment is manufactured by the following manufacturing method. A method for manufacturing a pile, in which two or more plate-like fins are arranged on an outer peripheral surface of a pile body at a lower end portion of the pile body, wherein each of the fins is formed as: 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.

The order of the constituent elements of the pile manufacturing method according to the present invention is not limited to the above-described order. In the method of manufacturing the pile 1 according to the present embodiment, the appropriate ranges of the selection conditions, such as the interval between adjacent fins 5, the lower end position and upper end position of the fins 5, and the fin width, are the same as those described for the pile 1 according to the present embodiment. Therefore, these selection conditions are preferably formed within the appropriate ranges described in pile 1 as required.

Examples (example)

The following description will explain the operation and effect of the present invention by performing analysis. In this analysis, the drawing load capacity of the stake 23 was obtained using the three-dimensional FEM model 21 shown in fig. 6.

The three-dimensional FEM model 21 for verification was set in a state in which the pile 23 (outer diameter (D) 609.6mm of the pile body 25, plate thickness 12mm, length 9.34 m) including the steel pipe pile body 25 and the steel plate fins 27 was disposed in the center of the foundation 31, and the lower end portion side of the pile 23 was buried by 1.22m (2 times the outer diameter of the pile body). The foundation 31 is formed in a cylindrical shape having an outer diameter of 12m and a height of 12m, and a layer boundary dividing the upper layer 33 (N value 20) and the lower layer 35 (N value 50) is provided at a position of a depth of 8.12m, thereby simulating a bearing layer in an actual foundation. The material data of the pile 23 and the foundation 31 are a bilinear elastoplastic model in which the secondary gradient changes at the yield point, and elements capable of taking into consideration interaction behavior such as contact and friction are taken between the pile 23 and the foundation 31.

Then, the relationship between the load applied to the pile 23 in the vertical direction and the pulling amount is calculated, and the pulling load capacity of the pile 23 is obtained. The drawing load capacity of a typical steel pipe pile is a load when the reference drawing amount is set to 0.1 times the outer diameter of the steel pipe or 0.1 times the outer diameter of the fin. Therefore, in the present embodiment, the reference drawing amount is set to 0.1 times the outer diameter of the pile body 25, and the load at the time of the reference drawing amount is reset to the drawing load.

In the present embodiment, the drawing load capacity when changing the shape of the fin 27 in the stake 23 is obtained. The specifications such as the shape of the fins 27 in the pile 23 are shown below (see fig. 1). 8 fins 27 are provided at equal intervals on the outer peripheral surface of the pile body 25. The vertical length lfv is 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 is set to 50mm. The fin width wf is set to 0.25 times the outer diameter of the pile body 25. At this time, the fin outer diameter Df is 1.5 times the outer diameter D of the pile body 25. The inclination angle β is set to 0 degrees or 9.46 degrees. The tip angle α of the fin 27 is set to 60 degrees. The fin thickness tf is 25mm. The standard is within the scope of the present invention except that the vertical length lfv is 2.5 times the outer diameter of the pile body 25.

Fig. 7 shows a relationship between the load and the pulling amount when the vertical length lfv is changed in the pile 23 having the inclination angle β of 0 degrees. Here, the reference drawing amount is also shown in fig. 7.

In general, the standard of the penetration amount into the bearing layer in the pile driving method is set to about 2 times the outer diameter of the pile body in consideration of the strength of the construction machine and the pile body. Therefore, in the present embodiment, considering this point, the penetration amount of the pile into the bearing layer is set to 2 times (i.e., 2D) the outer diameter of the pile body 3. From fig. 7, it can be confirmed that: in the case where the vertical length lfv is as short as 1 time (1D) the outer diameter of the pile body 25, which is within the scope of the present invention, the drawing load capacity is the highest. This is because the vertical length lfv is short, and therefore the upper ends of the fins 27 are located deep in the lower layer 35 (bearing layer), so that the drawing bearing capacity is wider in the foundation, and the drawing bearing capacity is maximized. Even when the vertical length lfv is 1.75D, which is within the scope of the present invention, the upper ends of the fins 27 are positioned in the lower layer 35, so that a drawing load capacity similar to that in the case where the vertical length lfv is 1D is obtained. Since the pull-out load exerts the resistance of the foundation 13, it can be clearly understood that: the longer the distance from the upper end of the fin to the upper surface of the carrier layer, the more effective the fin can be. 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 ends of the fins 27 are not located in the lower layer 35 (bearing layer), so that the pull-out bearing capacity is insufficient to exert the resistance of the foundation 13, and the pull-out bearing capacity is insufficient.

Fig. 8 shows a relationship between the load and the pulling amount when the vertical length lfv is changed in the pile 23 having the inclination angle β of 9.46 degrees. Fig. 8 also shows a reference drawing amount of 0.1 times the outer diameter of the steel pipe, similarly to fig. 7.

From fig. 8, it can be confirmed that: even when the fin 27 is inclined with respect to the center axis of the pile body 25, the pull-out bearing capacity is highest when the vertical length lfv is 1 times (1D) the outer diameter of the pile body 25 within the scope of the present invention, as in the case where the inclination angle β is 0 degrees. Even when the vertical length lfv is 1.75D, which is within the scope of the present invention, the upper ends of the fins 27 are positioned in the lower layer 35, so that a drawing load capacity similar to that in the case where the vertical length lfv is 1D is obtained. In other words, it is possible to confirm: in order to exert the drawing load, it is sufficient according to the present embodiment that the distance from the fin upper end to the upper surface of the bearing layer is 0.25D or more in order to sufficiently expand the drawing load exerted foundation 13 by the effect of the internal friction angle of the foundation in the vicinity of the fin upper end. 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 ends of the fins 27 are not located in the lower layer 35 (bearing layer), and therefore the drawing bearing capacity is insufficient to exert the bearing resistance of the foundation 13, and the drawing bearing capacity is insufficient. Further, it can be confirmed by comparing the results of fig. 7 and 8: when the fin 27 is inclined with respect to the center axis of the pile body 25, the pull-out bearing force exerts the bearing resistance of the foundation 13 and the pull-out bearing force becomes higher. In addition, the push-in load bearing capacity tends to be the same as the pull-out load bearing capacity, and it can be expected to be also high.

Industrial applicability

According to the present invention, a pile construction method, a structure construction method, a pile design method, and a pile manufacturing method, which do not require huge equipment for construction, are excellent in economical efficiency and environmental aspects, and can exhibit high pull-out bearing capacity and high press-in bearing capacity even under a condition of less penetration into a bearing layer, and can suppress occurrence of construction failure, can be provided.

Description of the reference numerals

1. Pile

3. Pile body

5. Fin type

11. Foundation

13. Foundation with drawing bearing capacity

15. Bearing layer

21 three-dimensional FEM model

23. Pile

25. Pile body

27. Fin type

31. Foundation

33. Upper layer

35. Lower layer

Claims (7)

1. A pile having two or more plate-like fins disposed on the outer peripheral surface of a pile body at the lower end portion of the pile body, wherein,

the vertical length of each fin is more than 0.5 times and less than 1.75 times of the outer diameter of the pile body,

the inclination angle of each fin is more than 0 degrees and less than 45 degrees relative to the central axis of the pile body.

2. A method of constructing a pile, wherein the pile according to claim 1 is inserted into a foundation in which a bearing layer exists,

the penetration is performed in such a manner that the upper ends of the fins arranged in the pile are located in the bearing layer.

3. A structure comprising the pile of claim 1.

4. A method of constructing a structure having a pile according to claim 1, wherein,

comprising the step of penetrating the piles into the ground.

5. A pile design method according to claim 1, wherein,

the tilt angle is set based on the required pullout bearing capacity of the stake,

then, a lower limit value of the vertical length is set according to the drawing bearing capacity.

6. A method for designing a pile, wherein two or more plate-like fins are arranged on the outer peripheral surface of a pile body at the lower end portion of the pile body,

each fin is set as follows:

the vertical length is more than 0.5 times and less than 1.75 times of the outer diameter of the pile body,

the inclination angle is 0-45 degrees with respect to the central axis of the pile body.

7. A method for manufacturing a pile, wherein two or more plate-like fins are arranged on the outer peripheral surface of a pile body at the lower end of the pile body,

each of the fins is formed as:

the vertical length is more than 0.5 times and less than 1.75 times of the outer diameter of the pile body,

the inclination angle is 0-45 degrees with respect to the central axis of the pile body.