JP2024052063A - Pile driving method - Google Patents

Abstract

To provide a pile driving method which can reinforce a pile head part of a pile driven into a ground, and can improve driving of a pile when the pile is retained at a high level.SOLUTION: A pile driving method incudes: a first driving step S2 of driving a steel pipe pile 1 into a ground 30 up to a position where a spiral blade 13 reaches a ground surface 31 while driving the steel pipe pile 1 into the ground while rotating a connection jig 10 in one direction by a driving machine 20; and a second driving step S3 of further driving the steel pipe pile 1 until a pile head part 1b in an exposed state is stored in a recessed part 32, while forming the recessed part 32 on the ground surface by compacting the ground by the spiral blade 13 while rotating the connection jig 10 in one direction by the driving machine 20, after the first driving step.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method for driving piles to support buildings, etc., and in particular to a method for reinforcing the heads of piles driven into the ground.

Conventionally, this type of pile driving method includes the steps of removing the peripheral area of the buried pile to expose the pile, forming a reinforcing layer at the bottom of the removed area, and attaching a flange member that abuts against the reinforcing layer to the exposed pile (see, for example, Patent Document 1).

JP 2011-69187 A

However, the pile driving method described above requires the removal of soil from the pile head, which incurs costs for disposal of the soil. In addition, the ground around the pile head (directly below the foundation) is backfilled, which creates problems with horizontal bearing capacity.

Furthermore, for example, when driving a steel pipe pile into the ground, the ground may be so hard that the driving machine is unable to drive the pile into the ground, and the steel pipe pile may not be driven to the required depth, resulting in the steel pipe pile being cut off at a high depth and the work ending there.

The present invention was made in consideration of these problems, and provides a pile driving method that can reinforce the head of a pile driven into the ground and improve the driving of the pile when the pile remains high.

In view of the above problems, the pile driving method of the present invention is a pile driving method in which a pile is driven into the ground by a driving machine, the driving machine having a connection jig connected to the upper end of the pile, the connection jig having a lower opening for inserting the upper end of the pile, a cylindrical jig body closed at the top, and a helical blade protruding outward from the outer periphery of the jig body, which pushes soil on the outer periphery of the jig body downward when rotated in one direction around the axis of the pile, and scrapes out soil on the outer periphery of the jig body upward when rotated in the opposite direction to the one direction.

The casting method includes a first casting step in which the casting machine drives the pile into the ground to a position where the helical blade reaches the ground surface, and a second casting step in which, after the first casting step, the casting machine rotates the connection jig in the one direction while compacting the ground with the helical blade to form a depression in the ground surface, and further drives the pile until the pile head is contained in the depression with the pile head exposed.

In the pile driving method of the present invention configured as described above, in the first driving step, the helical blade can reach the ground surface while driving the pile into the ground. Then, in the second driving step, the driving machine rotates the connection jig in one direction while compacting the ground with the helical blade and driving the pile further, so that the density of the ground around the pile increases, increasing the frictional force around the pile and increasing the pull-out force of the pile. The part of the pile buried in the ground adjacent to the pile head is supported by the compacted ground, so that the support force of the pile against the ground can be increased. As a result, the vertical support force of the pile can be increased and horizontal movement can be suppressed compared to a pile that is driven while removing soil. In the first driving step, when the driving machine drives the pile into the ground, the connection jig may be rotated in one direction according to the type of pile.

Furthermore, since the depression is formed on the ground surface by compacting the ground with the helical blade, even if rainwater or the like accumulates in the depression, it is difficult for it to seep into the ground and does not loosen, so the support state of the pile can be stably maintained. Note that, before the first casting step, a mounting step of erecting the pile vertically in the ground, inserting the upper end of the pile into the lower opening of the jig body, and mounting the pile to the connecting jig may be included, or this mounting step may be included during the first casting step. Therefore, "driving the pile into the ground with the driving machine to a position where the helical blade reaches the ground surface" includes the case where the pile is driven into the ground in the first casting step without the connecting jig being mounted, and means a driving operation that specifies the driving amount of the pile (the height of the part of the pile protruding from the ground surface).

In a more preferred embodiment, in the second driving step, when the driving force of the pile reaches or exceeds a predetermined value, the driving machine rotates the connection jig in the reverse direction, thereby driving the pile into the ground while applying a downward thrust force to the pile generated by the spiral shape of the helical blade against the compacted ground.

According to this aspect, in the pile driving method described above, when the connecting jig is rotated in one direction while driving the pile, it is assumed that the ground is compacted, so that the resistance to driving the pile increases and the pile cannot be driven any further. Therefore, when the driving force of the pile reaches or exceeds a predetermined value, the connecting jig is rotated in the opposite direction, so that the pile can be driven further into the ground while applying a driving force caused by the helical shape of the helical blade (i.e., the screw effect) to the ground below the pile. After the pile has been driven, the connecting jig may be rotated in the same direction again, and the soil scooped out at that time may be dumped into the depression. This reverse rotation scoops out some of the soil from the ground that was compacted by the helical blade.

In a more preferred embodiment, after the second driving step, the pile head is buried in the recess to provide a reinforcing member that reinforces the support of the pile against the ground.

According to this aspect, by providing a reinforcing member, the movement of the pile in the vertical and horizontal directions can be restrained by the reinforcing member, and the support of the pile on the ground can be reinforced. Such a reinforcing member can be formed by filling the depression with crushed stone and compacting the crushed stone, or by pouring concrete into the depression and allowing it to harden.

The connection jig used in the pile driving method of the present invention is used in the pile driving method described above, the pile is a wooden pile or a concrete pile, the jig body is provided with an abutment member that abuts against the end face of the upper end of the pile when the upper end is inserted, and the abutment member is rotatably attached to the jig body via a bearing.

According to this aspect, by using the connection jig, even if the connection jig is rotated in one direction in the second casting step, the wooden pile or concrete pile driven in the first casting step can be driven into the ground in the second casting step without rotating.

As mentioned above, the wooden or concrete pile is driven (penetrated) into the ground without being rotated. For this reason, in the second casting step, the compacted soil of the ground may prevent the pile from being driven any further (i.e., the pile may stop at a high level). In such cases, the wooden or concrete pile that has stopped at a high level may have to be cut off. However, even in such cases, if the connecting jig is rotated in the reverse direction, the helical blade can impart a driving force to the pile together with the connecting jig in the driving direction of the pile due to the helical shape of the helical blade (i.e., due to the screw effect), so that the wooden or concrete pile that has stopped at a high level can be pushed further into the ground.

A preferred embodiment of the connection jig is a connection jig used in the pile driving method described above, in which the pile is a steel pipe pile with a tip wing formed thereon, an engagement groove portion is formed in the jig body that engages with a protrusion formed in the steel pipe pile, and the helical wing is formed so that the one direction coincides with the rotation direction in which the tip wing penetrates the pile.

According to this aspect, by using the connection jig, in the first driving step, the steel pipe pile engaged with the engagement groove of the connection jig rotates in one direction together with the connection jig. As a result, the tip blade rotates the pile in the direction of penetration (i.e., in one direction), and the penetration of the steel pipe pile is promoted by the tip blade.

Furthermore, in the second driving step, the ground is tightened by the connection jig rotated in one direction (the direction in which the pile penetrates), and the tip blades promote the penetration of the steel pipe pile. Here, even if the steel pipe pile becomes stuck high, by rotating the connection jig in the opposite direction, the screw effect caused by the helical shape of the helical blades can impart a driving force to the connection jig and the pile in the driving direction of the pile, so that the stuck steel pipe pile can be pushed further into the ground. In this case, the tip blades apply a driving force to the steel pipe pile in the direction of pulling it out, but since a driving force is being applied to the steel pipe pile, it will not come out, and by repeating forward and reverse rotation, the steel pipe pile can be driven further into the ground without hindrance.

The pile driving method of the present invention can increase the frictional force around the pile head of a pile driven into the ground, improving and reinforcing the vertical and horizontal bearing capacity of the pile.

1A and 1B show a steel pipe pile used in a first embodiment of a pile driving method according to the present invention, in which (a) is a front view and (b) is a cross-sectional view taken along line A-A of (a). 2A and 2B show a connection jig to be connected to a driving machine for driving the steel pipe pile shown in FIG. 1, in which FIG. 2A is a front view and FIG. 2B is a central longitudinal sectional view. 13A and 13B are front views of modified examples of the connecting jig. 1A and 1B show a pile driving machine used in the pile driving method according to the present invention, in which FIG. 1 is a schematic diagram showing each step of a first embodiment of a pile driving method according to the present invention. FIG. 6A to 6C are schematic diagrams showing steps subsequent to the steps shown in FIG. 5 . 7A to 7C are schematic diagrams showing steps subsequent to the steps shown in FIG. 6 . 5 is a schematic diagram showing each step of a second embodiment of the pile driving method according to the present invention. FIG. 9A to 9C are schematic diagrams showing steps subsequent to the steps shown in FIG. 8 . 10A to 10C are schematic diagrams showing steps subsequent to the steps shown in FIG. 9 .

The first embodiment of the pile driving method according to the present invention will be described in detail below with reference to the drawings. Figure 1 shows a steel pipe pile used in the pile driving method according to this embodiment, where (a) is a front view and (b) is a cross-sectional view taken along line A-A in (a).

First, the steel pipe pile 1 used in the pile driving method according to this embodiment will be described in detail with reference to FIG. 1. The steel pipe pile 1 is formed of a steel pipe material 2 and is driven vertically into the ground to support the foundation of a building or the like. Both ends of the pipe material 2 are closed by welding or the like, but may be left open. A spiral tip wing 3 made of a steel plate is fixed to one end (lower end) of the steel pipe pile 1 by welding or the like. However, the tip wing 3 is not limited to a spiral shape and may be a wing with a pair of inclined semicircular plates fixed to the tip of the steel pipe pile, and the shape of the tip wing 3 is not particularly limited as long as it has a shape that promotes the penetration of the steel pipe pile 1.

The spiral tip wing 3 is fixed so that it rises while rotating along the outer periphery of the pipe material 2. Specifically, it is a positive spiral wing that drives the steel pipe pile 1 into the ground when the steel pipe pile 1 is rotated in one direction by a driving machine. For example, when the steel pipe pile 1 is set vertically and rotated in one direction (clockwise) in a plan view, the steel pipe pile 1 is inclined spirally so that the tip wing 3 penetrates the ground. The tip wing 3 is formed for approximately one revolution, but may be formed for multiple revolutions.

The pile head 1b at the top of the steel pipe pile 1 has a convex portion 4 that protrudes outward from the outer periphery. The convex portion 4 is made of a rectangular steel plate and is fixed to the outer periphery of the pile head 1b along the axial direction by welding or the like. The convex portion 4 is adapted to engage with an engagement groove portion 14 formed in the jig body of the connection jig 10 described later. The engagement convex portions 4 may be formed at multiple locations on the outer periphery. For example, when there are two convex portions 4, it is preferable that they are formed at diagonal positions on the axis when viewed from above. The convex portion 4 may be provided on the inner periphery of the steel pipe pile 1, and a part of the connection jig 10 may be inserted inside the steel pipe pile 1, and the engagement groove portion 14 may be provided in the inserted portion. In this way, the position of the convex portion 4 of the steel pipe pile 1 and the engagement groove portion 14 of the connection jig 10 is not limited as long as they engage in the rotational direction.

Next, the connection jig 10 for connecting to a driving machine for driving the steel pipe pile 1 into the ground will be described with reference to FIG. 2. In FIG. 2, the connection jig 10 has a lower opening 11 for inserting the upper end 1a of the steel pipe pile 1, and a cylindrical jig body 12 with a closed upper end. Furthermore, the connection jig 10 has a helical blade 13 that protrudes outward from the outer periphery of the jig body 12 and pushes the soil on the outer periphery of the jig body 12 downward when rotated in one direction around the axis of the steel pipe pile 1, and scrapes the soil on the outer periphery of the jig body 12 upward when rotated in the opposite direction. The helical blade 13 of the jig body 12 is in the opposite spiral direction to the tip blade 3 of the steel pipe pile 1.

That is, the helical blade 13 of the jig body 12 is formed of, for example, a steel plate, and has a shape that rises while circling the outer periphery of the cylindrical jig body 12 in a clockwise direction (one direction), and is fixed to the jig body 12 by welding or the like. Here, the helical blade 13 has a shape in which the wing width along the normal direction of the outer periphery of the cylindrical jig body 12 becomes wider as it proceeds from the tip side to the base side of the jig body 12. This allows the recess 32 formed by the helical blade 13 to have a shape with a space in the shape of a rhombus (wedge shape or cone shape). Note that the shape of the helical blade 13 is not limited to this, and for example, the shape of the helical blade 13 may be a shape in which the wing width is the same. When such a jig body 12 is rotated clockwise, the soil on the outer periphery of the jig body 12 is pushed downward, and when rotated counterclockwise (reverse rotation), the soil on the outer periphery of the jig body 12 is scraped upward, and this reverse rotation applies a driving force due to the spiral shape of the helical blade downward to the pile against the compacted ground. The connecting jig 10 has a small-diameter connecting part 12a on the upper part of the jig body 12 for connecting to a driving machine 20 described later.

The connecting jig 10 has an engagement groove 14 that opens downward formed in the outer peripheral wall that constitutes the cylindrical jig body 12. The engagement groove 14 is formed so that the width of the lower entrance portion is small and the width of the upper inner portion is large, and the protrusion 4 of the steel pipe pile 1 is inserted and the engagement groove 14 engages with the protrusion 4. The engagement groove 14 is formed upward from the part of the outer peripheral wall before the start of the helical blade 13 of the jig body 12, and is formed up to the outer peripheral wall below where the helical blade 13 ends.

The jig body 12 of the connection jig 10 is provided with an abutment member 15 at the top of the lower opening 11, which abuts against the end surface of the upper end 1a of the steel pipe pile 1 when the upper end 1a is inserted. The abutment member 15 is rotatably attached to the jig body 12 by rotating a bearing (not shown) and a thrust bearing 17. Specifically, the abutment member 15 is formed of a disk with an outer diameter slightly smaller than the inner diameter of the lower opening 11 of the jig body 12, and the center of the disk is rotatably supported by a central shaft 16 that constitutes a bearing. In addition, a thrust bearing 17 is installed between the upper surface of the abutment member 15 and the lower surface of the jig body 12. Furthermore, an O-ring (packing) 18 is located between the outer peripheral surface of the abutment member 15 and the inner peripheral surface of the jig body 12 to prevent dust from entering the thrust bearing 17.

A modified example of the above-mentioned connection jig 10 will be described with reference to FIG. 3. FIG. 3 is a front view of a modified connection jig. The connection jig 10A shown in FIG. 3(a) has two engagement grooves 14A, 14B. The jig body 12A constituting the connection jig 10A has two engagement grooves at its lower end, so the helical blade 13 is formed in a position moved upward. This connection jig 10A has the advantage that the connection state with the steel pipe pile 1 is stable because it has two engagement grooves.

The connection jig 10B shown in FIG. 3(b) has a large vertical length of the jig body 12B. In this connection jig 10B, the upper part of the helical blade 13 is long, so the soil can be compacted from the ground surface to a deep position, forming a depression, which can be filled with reinforcing materials such as crushed stone to more strongly and stably reinforce the support of the steel pipe pile 1 to the ground. Note that, although the helical blade 13 is formed around the jig body 12, 12A, 12B once in FIG. 2 and FIG. 3, it may be formed around two or more times.

Next, the driving machine 20 for driving the steel pipe pile 1 into the ground will be described with reference to FIG. 4. FIG. 4 shows a front view and a left side view of a heavy machine as the driving machine 20 for driving the steel pipe pile 1 into the ground.

In FIG. 4, the driving machine 20 is equipped with a driver's room and an engine room on the chassis 20A. The chassis 20A holds an arm 21 in a vertical position, and the arm 21 is configured to be able to change its angle to an inclined or horizontal state by a hydraulic cylinder. The lifting head 22 is attached to the arm 21 so that it can move up and down. The lifting head 22 has a connecting jig 10 for connecting the steel pipe pile 1 connected and fixed to the lower part, and a drive unit (not shown) such as a hydraulic motor for rotating the jig body 12 is built in. The connecting jig 10 is attached below the lifting head 22, and the upper end 1a of the steel pipe pile 1 is inserted and held in the lower opening 11 of the jig body 12. The lifting head 22 is raised and lowered up and down to apply a driving force downward to the connecting jig 10, and the jig body 12 is rotated as necessary to drive the steel pipe pile 1 into the ground.

The pile driving method of the first embodiment, in which the steel pipe pile 1 configured as described above is driven using a connection jig 10, will be described below with reference to Figures 5 to 7. Note that the pile driving method of the first embodiment is applied to a steel pipe pile (penetrating steel pipe pile) 1 having a tip wing 3, while the pile driving method of the second embodiment described below is applied to a wooden pile or concrete pile without a tip wing.

As shown in Figures 5(a) and (b), the method of driving the steel pipe pile 1 involves vertically erecting the steel pipe pile 1 on the ground 30, inserting the upper end 1a of the steel pipe pile 1 into the lower opening 11 of the jig body 12 of the connecting jig 10, and attaching the steel pipe pile 1 to the connecting jig 10 (attaching step S1). In this attachment step S1, the convex portion 4 formed on the outer peripheral surface of the upper part of the steel pipe pile 1 is inserted into and engaged with the engagement groove portion 14 of the connecting jig 10, and for example, by rotating the steel pipe pile 1, the convex portion 4 can be moved from the entrance portion of the engagement groove portion 14 to the inner portion, and the steel pipe pile 1 can be hung on the connecting jig 10. In addition, in the case of wooden piles or concrete piles, since the convex portion 4 is not provided on the wooden piles and concrete piles, the lower opening 11 of the connecting jig 10 is lowered with the wooden piles and concrete piles erected, and the connecting jig 10 is attached to the connecting jig 10 from above. In addition, if the pile is a wooden pile or a concrete pile, the wooden pile or the concrete pile does not have a protrusion 4, so the wooden pile or the concrete pile does not engage with the engagement groove 14 of the connection jig 10. In addition, by applying tension again to the wire that suspends the pile, it is possible to fine-tune the casting position.

After this attachment step S1, as shown in Figures 5(b) and (c), the first driving step S2 is carried out, in which the driving machine 20 drives the steel pipe pile 1 into the ground 30 while the helical blade 13 of the connection jig 10 reaches the ground surface 31. However, if the steel pipe pile 1 can be driven into the ground 30 to a position where the helical blade 13 reaches the ground surface, for example, the driving machine 20 may be used to drive the steel pipe pile 1 to that position with another general connection jig attached (without the connection jig 10 attached), and then the connection jig 10 may be attached and the second driving step S3 may be carried out before carrying out the second driving step S3. Furthermore, the steel pipe pile 1 may be driven into the ground 30 using the driving machine 20 with another general connection jig attached (without the connection jig 10) until halfway through the first driving step S2, and then the above-mentioned attachment step may be carried out on the driven steel pipe pile 1, driving the steel pipe pile 1 into the ground 30 until the helical blade 13 reaches the ground surface.

In addition, in this first casting process S2, if the pile is a steel pipe pile 1, the connection jig 10 is rotated in one direction while the process is carried out. The soil 30a of the ground 30 excavated by the tip blade 3 is in a soft state. The lifting head 22 of the casting machine 20 applies a downward driving force F1 to the steel pipe pile 1 via the connection jig 10, causing it to penetrate into the ground 30.

When the piles are wooden or concrete, the wooden and concrete piles do not have the protrusions 4, and therefore the wooden and concrete piles do not engage with the engagement grooves 14 of the connection jig 10, so the connection jig 10 may be performed without rotating. However, even if the connection jig 10 is rotated, the wooden and concrete piles will not rotate because the connection jig 10 is provided with the abutment members 15 rotatably attached to the jig body 12 (see FIG. 2(b)).

In the subsequent second casting step S3, as shown in FIG. 6(a), after the first casting step S2, the driving machine 20 further rotates the connection jig 10 in one direction (CW) while compacting the ground 30 with the helical blades 13 to form a depression 32 in the ground surface 31, and further drives the steel pipe pile 1 into the depression 32 until the pile head is contained in an exposed state.

In the second casting step S3, the steel pipe pile 1, whose upper end has been inserted into the lower opening 11 of the jig body 12 of the connection jig 10, abuts against the abutment member 15 attached so as to be freely rotatable. However, the protrusion 4 of the steel pipe pile 1 engages with the engagement groove 14 of the connection jig 10, and the steel pipe pile 1 rotates together with the connection jig 10, so the rotatable function of the abutment member 15 is unnecessary. Therefore, when only the steel pipe pile 1 is used as the pile, the abutment member 15, thrust bearing 17, and O-ring 18 located inside the lower opening 11 of the connection jig 10 are unnecessary.

In the second driving step S3, as shown in FIG. 6(b), the driving force F1 of the steel pipe pile 1 remains high when it reaches or exceeds a predetermined value. In such a case, the driving machine 20 rotates the connection jig 10 in the reverse direction (CCW), so that the driving force F2 generated by the spiral shape of the helical blade 13 against the compacted ground is applied to the lower part of the steel pipe pile 1, and the steel pipe pile 1 can be driven into the ground 30. The driving force F1 of the steel pipe pile 1 is the force required to drive the steel pipe pile 1 into the ground 30, and may be measured, for example, by a load meter. Therefore, when the driving force F1 of the steel pipe pile 1 reaches or exceeds a predetermined value, for example, when the tip blade 3 at the lower end of the steel pipe pile 1 hits a foreign object 33 in the ground 30, making it difficult to penetrate the steel pipe pile 1, or when the ground 30 is over-compacted by the helical blade 13, causing the resistance of the steel pipe pile 1 to the ground 30 to become too large.

In such a case, the lifting head 22 of the driving machine 20 applies a driving force F1 to the connection jig 10, and the connection jig 10 is rotated in reverse, and the reverse-rotating helical blade 13 applies a downward propulsive force F2 to the steel pipe pile 1, crushing or moving the foreign object 33, preventing the steel pipe pile 1 from becoming stuck at a high level and allowing penetration to continue. As a result, the steel pipe pile 1 can be penetrated deeper into the ground, and the penetration state of the steel pipe pile 1 becomes stable.

In the second casting step S3, as shown in FIG. 6(c), the spiral blade 13 compacts the ground to form a depression 32, and the pile head 1b is accommodated in the depression 32 in an exposed state. The ground around the depression 32 that accommodates the pile head 1b becomes a compacted ground 30b. After the second casting step S3, as shown in FIG. 7(a), a filler 34 such as crushed stone is filled in the depression 32, and as shown in FIG. 7(b), the filler 34 is compacted by a tapping rammer 40 to form a reinforcing member 35 (reinforcing step S4). The reinforcing member 35 is formed by burying the pile head 1b in the depression 32. The reinforcing member 35 reinforces the support of the steel pipe pile 1 to the ground 30. Here, burying the pile head 1b does not only mean burying the entire pile head 1b, but also means that, for example, a part of the pile head 1b (for example, the end face) is exposed and the other part is buried. The compacted ground forms a reinforcement area 36 around the depression 32, and the provision of a reinforcing member 35 increases the vertical bearing capacity of the steel pipe pile 1 and suppresses horizontal movement.

After the reinforcing step S4, as shown in FIG. 7(c), a foundation 45 is constructed in a stable state on the reinforcing member 35 (S5). When constructing the foundation 45, the space in the recess 32 is backfilled with soil. The reinforcing member 35 with the pile head 1b reinforced and what is constructed on the pile head 1b are not limited to foundations, but may be steel columns or structures that serve as the framework of a building.

Next, a pile driving method according to a second embodiment, in which a wooden pile or concrete pile without tip wings is driven using a connection jig 10, will be described below with reference to Figures 8 to 10. Note that unlike the steel pipe pile 1 shown in Figure 1, wooden piles and concrete piles have a wooden shaft portion and a concrete shaft portion, and are formed with a shaft body without a convex portion 4 at the pile head 1b and without tip wings 3. Driving a wooden pile 1A will be described below.

As shown in Figures 8(a) and (b), the method of driving the wooden pile 1A involves setting the wooden pile 1A vertically in the ground 30, inserting the upper end of the wooden pile 1A into the lower opening 11 of the jig body 12 of the connecting jig 10, and attaching the wooden pile 1A to the connecting jig 10 (attaching step S11). In this attaching step S11, the connecting jig 10 is placed over the top of the wooden pile 1A.

After this attachment step S11, as shown in Fig. 8 (b) and (c), in the first casting step S12, the wooden pile 1A is driven into the ground 30 by the casting machine 20 while the spiral blade 13 of the connection jig 10 reaches the ground surface 31. This first casting step S12 is performed without rotating the connection jig 10 because the pile is a wooden pile 1A. In the case of a wooden or concrete pile, the wooden pile 1A is directly penetrated into the ground 30 from the ground surface 31 because the connection jig 10 is not rotated. In the first casting step S12, as described above, the steel pipe pile 1 may be cast using the casting machine 20 with another general connection jig attached (without the connection jig 10 attached), or this may be performed halfway and then the connection jig 10 may be attached to perform the first casting step S12.

In the subsequent second casting step S13, as shown in FIG. 9(a), after the first casting step S12, the casting machine 20 further rotates the connection jig 10 in one direction (CW) while compacting the ground 30 with the helical blades 13 to form a depression 32 in the ground surface 31, and further drives the steel pipe pile 1 into the depression 32 until the pile head 1b is contained in an exposed state in the depression 32.

In the second casting step S13, the wooden pile 1A is firmly inserted into the ground 30 and is therefore unable to rotate. However, in the connection jig 10, the wooden pile 1A, whose upper end has been inserted into the lower opening 11 of the jig body 12, is in contact with the abutment member 15, which is attached so as to be freely rotatable, so the connection jig 10 can rotate freely relative to the wooden pile 1A. In other words, the connection jig 10 can rotate freely forward and backward around the wooden pile 1A. Note that if only wooden piles 1A or concrete piles are used as piles, the engagement groove 14 formed in the jig body 12 of the connection jig 10 is not necessary.

In the second casting process S13, as shown in FIG. 9(b), when the driving force F1 of the wooden pile 1A reaches or exceeds a predetermined value, the driving machine 20 rotates the connection jig 10 in the reverse direction (CCW), so that the compacted soil of the ground is scraped out by the helical blade 13, while the driving force F2 generated by the helical shape of the helical blade 13 is applied to the bottom of the wooden pile 1A, and the wooden pile is driven into the ground 30. The driving force F1 of the wooden pile 1A is the force required to drive the wooden pile 1A into the ground 30. Therefore, when the driving force F1 of the wooden pile 1A reaches or exceeds a predetermined value, for example, when the bottom end of the wooden pile 1A hits a foreign object 33 in the ground 30, making it difficult to penetrate the wooden pile 1A, or when the ground 30 is over-compacted by the helical blade 13, causing the resistance of the wooden pile 1A to the ground 30 to become too large.

In such a case, the lifting head 22 of the driving machine 20 applies a driving force F1 to the connection jig 10, and the connection jig 10 is rotated in reverse, and the reverse-rotating helical blade 13 applies a downward driving force F2 to the wooden pile 1A, moving the foreign object 33 and preventing the wooden pile 1A from becoming stuck at a high level, allowing the penetration to continue. As a result, the wooden pile 1A can be penetrated deeper into the ground, and the penetration state of the wooden pile 1A becomes stable.

In the second casting step S13, as shown in FIG. 9(c), the spiral blade 13 compacts the ground to form a depression 32, and the pile head 1b is housed in the depression 32 in an exposed state. The ground around the depression 32 that houses the pile head 1b becomes compacted ground 30b. After the second casting step S13, as shown in FIG. 10(a), a filler 34 such as crushed stone is filled into the depression 32, and as shown in FIG. 10(b), the filler 34 is compacted by a tapping rammer 40 to form a reinforcing member 35 (reinforcing step S14). The compacted ground forms a reinforcing area 36 around the depression 32, and the provision of the reinforcing member 35 increases the vertical bearing capacity of the steel pipe pile 1 and suppresses horizontal movement.

After the reinforcing step S14, as shown in FIG. 10(c), a foundation 45 is constructed in a stable state on the reinforcing member 35 (S15). When constructing the foundation 45, the space in the recess 32 is backfilled with soil. The reinforcing member 35 with the pile head 1b reinforced and what is constructed on the pile head 1b are not limited to foundations, but may be steel columns or structures that serve as the framework of a building.

As described above, according to the pile driving method of the present invention, a depression 32 is formed in the compacted ground 30b to match the pile head 1b of the pile, and a reinforcing member 35 is provided within the depression 32 to reinforce the pile head 1b, thereby increasing the vertical bearing capacity of the pile and suppressing horizontal movement. In addition, when the pile becomes stuck at a high level, the penetration of the pile into the ground can be improved and the penetration state can be stabilized. Furthermore, because the depression 32 is formed by compaction, the amount of waste soil discharged can be reduced, and the cost of disposing of the waste soil can be reduced.

Furthermore, according to the connection jig of the present invention, the protrusion 4 of the steel pipe pile 1 is engaged with the engagement groove 14 of the connection jig 10, and the steel pipe pile 1 is rotated together with the connection jig 10, so that the tip blade 3 promotes the penetration of the steel pipe pile 1 and improves the high-level retention. In addition, in the case of wooden piles 1A and concrete piles, even if high-level retention occurs, the connection jig 10 can be rotated in the reverse direction and the screw effect of the helical blade can be used to drive the wooden pile 1A into the ground without rotating it.

Thus, according to the embodiment, in both the first and second embodiments, in the second driving step, the connection jig 10 is further rotated in one direction while the helical blade 13 compacts the ground 30 and the steel pipe pile 1 (wooden pile 1A) is further driven in, so that the frictional force around the pile is increased by the increased density of the ground around the pile, and the pull-out force of the pile can be increased. The part of the steel pipe pile 1 (wooden pile 1A) buried in the ground adjacent to the pile head 1b is supported by the compacted ground 30, so the bearing force of the steel pipe pile 1 (wooden pile 1A) against the ground 30 can be increased. As a result, the vertical bearing force of the steel pipe pile 1 (wooden pile 1A) can be increased and horizontal movement can be suppressed compared to when the steel pipe pile 1 (wooden pile 1A) is driven in while removing soil. In addition, the depression 32 is formed on the ground surface 31 by compacting the ground 30 with the helical blade 13. Therefore, even if rainwater or the like accumulates in the depression 32, the rainwater or the like is unlikely to seep into the ground 30 and will not loosen, so the support state of the steel pipe pile 1 (wooden pile 1A) can be stably maintained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various design modifications can be made without departing from the spirit of the present invention described in the claims. The present invention allows the configuration of one embodiment to be added to the configuration of another embodiment, the configuration of one embodiment to be replaced with another embodiment, or part of the configuration of one embodiment to be deleted.

For example, in the example shown, the pile head is buried in crushed stone in the recess 32 to provide a reinforcing member for reinforcing the support of the pile against the ground, but the reinforcing member is not limited to crushed stone, and ready-mixed concrete, mortar, etc. may be used to provide the reinforcing member. For example, precast materials such as concrete blocks may be placed as reinforcing members.

1: Steel pipe pile (pile), 1A: Wooden pile (pile), Concrete pile (pile), 1a: Upper end, 1b: Pile head, 3: Tip wing, 4: Convex part, 10: Connection jig, 11: Lower opening, 12: Jig body, 13: Spiral wing, 14: Engagement groove, 15: Contact member, 17: Thrust bearing, 20: Casting machine, 30: Ground, 31: Ground surface, 32: Depression, 33: Foreign object, 34: Filling material (crushed stone), 35: Reinforcing member, 36: Reinforcing area, F1: Driving force, F2: Driving force

Claims (5)

A pile driving method in which piles are driven into the ground using a driving machine,
The driving machine has a connection jig connected to the upper end of the pile,
The connection jig is
A cylindrical jig body having a lower opening for inserting the upper end of the pile and a closed upper portion;
A helical blade protruding outward from the outer peripheral surface of the jig body, which pushes the soil on the outer periphery of the jig body downward when rotated in one direction around the axis of the pile, and scrapes the soil on the outer periphery of the jig body upward when rotated in the opposite direction to the one direction,
The casting method is as follows:
A first driving step of driving the pile into the ground to a position where the helical blade reaches the ground surface by the driving machine;
a second driving step in which, after the first driving step, the driving machine rotates the connecting jig in the one direction while compacting the ground with the helical blade to form a depression in the ground surface, and further drives the pile until the pile head is contained in the depression with an exposed head. The pile driving method according to claim 1, characterized in that, in the second driving step, when the driving force of the pile reaches or exceeds a predetermined value, the driving machine rotates the connection jig in the reverse direction, thereby driving the pile into the ground while applying a driving force generated by the spiral shape of the spiral blade to the bottom of the pile against the compacted ground. The pile driving method according to claim 1, characterized in that after the second driving step, a reinforcing member is provided to reinforce the support of the pile against the ground by burying the pile head in the recess. The connection jig used in the pile driving method according to any one of claims 1 to 3,
The pile is a wooden pile or a concrete pile,
The jig body is provided with an abutment member that abuts against an end surface of the upper end portion when the upper end portion of the pile is inserted,
The connecting jig, wherein the abutment member is rotatably attached to the jig body via a bearing. The connection jig used in the pile driving method according to any one of claims 1 to 3,
The pile is a steel pipe pile having a tip wing formed thereon,
The jig body has an engagement groove portion that engages with a convex portion formed on the steel pipe pile,
A connection jig, characterized in that the helical wing is formed so that the one direction coincides with the rotational direction in which the tip wing penetrates the pile.

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