JP6886717B2 - Construction method of steel pipe pile - Google Patents

Description

The present invention relates to a construction method suitable for building a steel pipe pile having a large diameter at a large depth, for example, forming an outer peripheral portion of a bridge foundation with a steel pipe sheet pile.

Generally, when constructing a retaining wall facing a water area such as a bridge foundation, a quay, or a shore using a large-diameter steel pipe sheet pile, the vibration of driving the steel pipe sheet pile into the ground by the vibrating force of a vibro hammer suspended by a crane. Construction method, Nakadori method, hydraulic hammer, diesel hammer, in which the steel pipe sheet pile is sunk in the ground by its own weight and press-fitting or light tapping while excavating the tip side with an auger screw or drilling bucket that is inserted and placed inside the steel pipe sheet pile. A striking method in which the head of a steel pipe sheet pile is struck with a drop hammer or the like to drive it into the ground, a press-fitting method in which a static pressure of hydraulic pressure is applied to the steel pipe sheet pile and the steel pipe sheet pile is press-fitted into the ground, etc. ).

However, if a hard support layer consisting of a gravel layer, bedrock, etc. exists at a large depth of 50 m or more from the pipe head, and it is necessary to penetrate the tip side of the steel pipe sheet pile into the support layer, the tip can be used by any construction method. It was possible to build the steel pipe sheet pile while adding it until it reached the support layer, but it was extremely difficult to root it in the support layer thereafter. This is because in the vibration method, striking method, press-fitting method, etc., the length of the steel pipe sheet pile increases the frictional resistance against the ground, and the rigidity of the steel pipe sheet pile as a whole decreases. This is because the force, the striking force in the striking method, and the press-in input in the press-fitting method do not work sufficiently to penetrate the support layer. On the other hand, in the middle digging method using an auger screw, excavation is performed while adding the auger screw corresponding to a large depth, but the longer the auger screw itself, the lower the rigidity of the auger screw itself, which makes it difficult to excavate a hard support layer. Further, in the middle digging method using a drilling bucket, the drilling bucket is attached to the lower end of a kelly bar that is held up and down and rotatably by a crane, and excavates while adding the kelly bar corresponding to a large depth, but the thin kelly bar is long. As a result, the rigidity is lost and bending, twisting, and runout occur, so that the rotational force and pressing force applied to the drilling bucket are insufficient, and a hard support layer cannot be excavated.

Internet / Web / General Incorporated Association Steel Pipe Pile / Steel Pipe Sheet Sheet Technology Association What is Steel Pipe Sheet Sheet? Search date: July 31, 2017, http://www.jaspp.com/koukanyaita/construction.html Internet / Web / Bridge Design Training-Planning and Design of Pile Foundations- (Types of Pile Foundations) August 30, 2011 Yonden Consultants Co., Ltd. Yutaka Ikeda Search Date: July 31, 2017, http // www .kenji.net/kensyu_jisseki/h23/images/kuikiso_syurui.pdf

In view of the above circumstances, the present invention is a method for constructing a steel pipe pile including a steel pipe sheet pile, even when a hard support layer exists at a large depth of 50 m or more from the pile head, the tip of the steel pipe pile is contained in the support layer. The purpose is to provide a means for easily penetrating the side to ensure rooting, thereby enabling high-depth construction with high support strength and high yield strength.

If the means for achieving the above object is shown with reference numerals in the drawings, the method for constructing a steel pipe pile according to the invention of claim 1 reaches the hard support layer Gh at the tip of the steel pipe pile (steel pipe sheet pile 1). The first step of discharging the earth and sand in the steel pipe pile by rotating and raising and lowering the drilling bucket 3 attached to the lower end of the kelly bar 2 held by the earth drill excavator M while embedding it in the ground until it is completed. After discharging substantially the entire amount of earth and sand in the steel pipe pile, a down-the-hole hammer 5 provided with a diameter-expanding hammer bit 51 is attached to the lower end of the kelly bar 2 from which the drilling bucket 3 has been removed via an air swivel mechanism 4, and the air swivel mechanism is attached. The second step of connecting the air hose 7 for operating the down-the-hole hammer between 4 and the compressed air supply source (air compressor 6), and the down-the-hole hammer 5 attached to the keriba 2 are inserted into the steel pipe pile and landed on the bottom. The third step of expanding the diameter of the hard support layer Gh to a predetermined depth by operating the down-the-hole hammer 5 and fitting the tip end side of the steel pipe pile into the hard support layer Gh by its own weight along with the expanded diameter excavation. After the tip end side of the steel pipe pile reaches a predetermined depth in the hard support layer Gh, a fourth step of placing concrete C in the steel pipe pile from which the down-the-hole hammer 5 is extracted is sequentially performed.

The invention of claim 2 is the method of constructing a steel pipe pile according to claim 1, wherein the air swivel mechanism 4 has an air hose connection port 41 on the outer periphery of the shaft body 4a for concentrically connecting the upper and lower ends to the kelly bar 2 and the down-the-hole hammer 5. The tubular body 4b having the above is airtightly fitted so as to be relatively rotatable, and the air supply port 41 and the air supply on the shaft body 4b side are supplied to the annular flow path 40 formed between the shaft body 4a and the tubular body 4b. In addition to communicating with the road 42, the tensioning tools 43 that move in and out in the radial direction are provided at a plurality of locations that are evenly distributed on the outer side of the tubular body 4b in the circumferential direction.

The invention of claim 3 is characterized in that, in the method for constructing a steel pipe pile according to claim 1 or 2, the hard support layer Gh is at a depth d of 50 m or more from the pile head position.

The invention of claim 4 is the method of constructing a steel pipe pile according to any one of claims 1 to 3, wherein in the first step, the steel pipe pile is driven into the ground by the vibrating force of the vibro hammer V, and then inside the steel pipe pile. It is characterized in that the earth and sand of the above is discharged by the drilling bucket 3.

The invention according to claim 5 is a steel pipe sheet pile 1 in which a plurality of steel pipe piles are sequentially driven in parallel while being connected to each other via a joint 1a in the method for constructing a steel pipe pile according to any one of claims 1 to 4. It is supposed to be.

The invention of claim 6 is the method of constructing a steel pipe pile according to claim 5, wherein a plurality of steel pipe sheet piles 1 are sequentially driven from the water to the bottom ground so as to be arranged in a ring shape to form an outer wall body 10a of the bridge foundation 10. It is supposed to be formed.

Hereinafter, the effects of the present invention will be specifically described with reference to the drawings. In the method for constructing a steel pipe pile according to the present invention, in the first step, the steel pipe pile (steel pipe sheet pile 1) is built in the ground until the tip reaches the hard support layer Gh, and the earth and sand in the steel pipe pile is laid in the keriba 2. It is discharged by the drilling bucket 3 attached to the lower end, and in the next second step, a down-the-hole hammer 5 provided with a diameter-expanding hammer bit 51 is attached to the kelly bar 2 via the air swivel mechanism 4 instead of the drilling bucket 3. .. Then, in the third step, by operating the down-the-hole hammer 5, the hard support layer Gh is excavated to a predetermined depth, and the tip end side of the steel pipe pile is fitted into the support layer Gh by its own weight. It is possible to efficiently, easily and surely root the steel pipe pile into the hard support layer Gh, which has been difficult in the past. Then, in the fourth step, a high-strength pile can be constructed by placing concrete C in the steel pipe pile from which the down-the-hole hammer 5 has been pulled out. Although the down-the-hole hammer 5 is operated with rotation, it is attached to the lower end of the kelly bar via the air swivel mechanism 4, so that the down-the-hole hammer 5 is supplied from the compressed air supply source (air compressor 6) through the air hose 7. Compressed air for operation can be introduced without any trouble.

According to the invention of claim 2, in the air swivel mechanism 4, a tubular body 4b having an air hose connection port 41 on the outer periphery thereof is airtightly externally rotatably attached to a shaft body 4a which is concentrically connected to the kelly bar 2 and the down-the-hole hammer 5. Although it has a structure to be fitted, the tubular body 4a is provided with a plurality of tensioning tools 43 that move in and out in the radial direction, and these tensioning tools 43 are stretched so as to abut or approach the inner peripheral surface of the steel pipe pile. By pulling it out, the down-the-hole hammer 5 can be held in a stable posture that does not swing in the steel pipe pile, so that high excavation efficiency by the down-the-hole hammer 5 can be ensured.

According to the invention of claim 3, in the deep construction where the hard support layer Gh is at a depth d of 50 m or more from the pile head position, it is extremely difficult in the past to root the steel pipe pile into the hard support layer Gh. It can be done efficiently, easily and surely.

According to the invention of claim 4, in the first step, after the steel pipe pile is driven into the ground by the vibrating force of the vibro hammer V, the earth and sand in the steel pipe pile is discharged by the drilling bucket 3, so that the construction efficiency is high. Is obtained.

According to the invention of claim 5, the steel pipe sheet pile 1 is a steel pipe sheet pile 1 in which a plurality of steel pipe piles are sequentially driven in parallel while being connected to each other via a joint 1a. It can be easily and surely rooted to build a high-strength wall body.

According to the invention of claim 6, when a plurality of steel pipe sheet piles 1 are sequentially driven into the bottom ground from the water so as to be arranged in an annular shape to form the outer peripheral wall body 10a of the bridge foundation 10, the hard support layer Gh is formed. Even if it is located at a large depth, it can be reliably rooted to construct an outer wall body 10a having a high yield strength.

It is a longitudinal side view which shows the driving state of the steel pipe sheet pile by the vibro hammer of the 1st process in one Embodiment which applied the construction method of the steel pipe pile which concerns on this invention to the bridge foundation construction. It is a vertical sectional side view which shows the discharge state of earth and sand in a steel pipe sheet pile by the drilling bucket of the 1st process. It is a longitudinal side view which shows the excavation state of the hard support layer by the down-the-hole hammer of the 3rd process in the 1st Embodiment. The air swivel mechanism interposed in the attachment portion of the down-the-hole hammer to the keriba is shown, (a) is a plan view, and (b) is a vertical sectional front view of a main part. It is a developed perspective view which shows the connection part of a keriba and a down-the-hole hammer via the air swivel mechanism. It is a longitudinal side view which shows the excavation situation of the hard support layer by the down-the-hole hammer loaded in the steel pipe sheet pile in an enlarged manner. The bridge foundation construction is shown, (a) is a vertical sectional side view showing a state in which concrete is poured into the steel pipe sheet pile in the fourth step, and (b) is a row of steel pipe sheet piles constituting the outer peripheral wall of the bridge foundation. (C) is a front view showing a state in which a pier is constructed on a bridge foundation.

As described above, the method for constructing a steel pipe pile according to the present invention is characterized in that the following first steps to fourth steps are sequentially performed.
[First step] ... The steel pipe pile is embedded in the ground until the tip reaches the hard support layer, and the drilling bucket attached to the lower end of the keriba held by the earth drill excavator is rotated and raised and lowered. , The earth and sand in the steel pipe pile is discharged.
[Second step] ... After discharging almost all of the earth and sand in the steel pipe pile, a down-the-hole hammer equipped with a diameter-expanding hammer bit is attached to the lower end of the keriba from which the drilling bucket has been removed via an air swivel mechanism. An air hose for operating the down-the-hole hammer is connected between the air swivel mechanism and the compressed air supply source.
[Third step] ... The down-the-hole hammer attached to the keriba is inserted into the steel pipe pile to land on the bottom, and the hard support layer is excavated to a predetermined depth by the operation of the down-the-hole hammer, and the diameter is expanded. Along with this, the tip side of the steel pipe pile is fitted into the hard support layer by its own weight.
[Fourth step] ... After the tip end side of the steel pipe pile reaches a predetermined depth in the hard support layer, concrete is poured into the steel pipe pile from which the down-the-hole hammer has been pulled out.

Hereinafter, an embodiment in which the method of constructing a steel pipe pile of the present invention is applied to bridge foundation construction will be specifically described with reference to the drawings. In this bridge foundation construction, as shown in FIG. 1, a plurality of steel pipe sheet piles 1 are sequentially built in parallel on the bottom ground as steel pipe piles from above the water surface at the construction position in the water area, thereby forming the outer peripheral wall of the bridge foundation. It builds the body. The submerged ground G is composed of a mud layer Gm, a sedimentary layer Gs of sand and gravel, a hard support layer Gh composed of a coarse gravel layer and a bedrock, and a pile head position of the hard support layer Gh. The depth d from is at a large depth of 50 m or more. The diameter of the steel pipe sheet pile 1 is about 1 to 2 m. W in the figure indicates an aqueous layer.

In the construction method of this embodiment, in the first step, as shown in FIG. 1, an earth drill excavator equipped with a boom B and a front frame F is mounted on a flatbed ship S having a load of about 300 tons floating on water. A 60-65 ton class crawler crane M that can be configured is mounted, the top of the steel pipe sheet pile 1 is gripped by the vibro hammer V suspended by the boom B, and the steel pipe sheet pile 1 is held on the bottom of the water by the vibrating force of the vibro hammer V. Drive into the ground G. At this time, a plurality of steel pipe sheet piles 1 are concentrically connected and added by welding until the tip reaches the hard support layer Gh. Then, when the tip of the steel pipe sheet pile 1 reaches the hard support layer Gh, the vibro hammer V is separated from the steel pipe sheet pile 1 and lowered onto the flatbed ship S, and as shown in FIG. 2, forward of the crawler crane M. A yoke Y is attached to the tip of the overhanging front frame F to make it an earth drill excavator specification. The yoke Y is composed of a keriba drive device KD and a rotary table RT below which a pair of hose reels Hr are installed. The rotary table RT has rotary couplings for hydraulic and electrical wiring (not shown). ) Is provided.

Next, in the crawler crane M having the specifications of the earth drill excavator, the square tubular kelly bar 2 is suspended by the boom B via the swivel joint J and inserted into the yoke Y so as to be vertically movable. The drilling bucket 3 is attached to the lower end of the pipe, and as shown in FIG. 2, the drilling bucket 3 is inserted into the steel pipe sheet pile 1 which has reached the hard support layer Gh first. Then, by repeating the rotation and raising / lowering operations of the drilling bucket 3 via the kelly bar 2, the earth and sand in the steel pipe sheet pile 1 is scraped into the drilling bucket 3 and discharged to the outside, but the scraping position becomes deep. While adding the Keriba 2 in response to the above, the soil is discharged to the lowest part in the steel pipe sheet pile 1.

When the soil removal in the steel pipe sheet pile 1 that has reached the hard support layer Gh is completed, as a second step, the drilling bucket 3 extracted from the steel pipe sheet pile 1 is removed from the kelly bar 2, and the lower end of the kelly bar 2 is shown. As shown in 3, the down-the-hole hammer 5 is attached via the air swivel mechanism 4, and the hose reel 8 is interposed between the air compressor 6 of the compressed air supply source mounted on the flatbed vessel S and the air swivel mechanism 4. Then connect the air hose 7 for operating the down-the-hole hammer.

Here, in the air swivel mechanism 4, as shown in FIGS. 4A and 4B, a substantially round shaft-shaped shaft body 4a has a substantially short cylindrical cylinder 4b via upper and lower bearings 44 and a seal ring 45. It is relatively rotatable and airtightly fitted. An annular flow path 40 is formed between the shaft body 4a and the cylinder body 4b, and an air hose connection port 41 that opens on the peripheral surface of the cylinder body 4b communicates with the annular flow path 40 and is on the shaft body 4b side. An air supply path 42 along the axial direction of the above means communicating with the annular flow path 40 via a vent hole 42a in the radial direction.

The shaft body 4a of the air swivel mechanism 4 has a square tubular portion 47 on the upper end side, and pin insertion holes 47a are formed in the middle portions of the facing walls thereof, and the lower end side constitutes a connecting tubular portion 48 having a circular outer circumference. The inside of the connecting cylinder 48 is a hexagonal hole 48a that is open downward, and the air supply path 42 communicates with the inner bottom of the hexagonal hole 48a. A pair of pin insertion holes 48b are formed in parallel in the connecting cylinder portion 48, and each pin insertion hole 48b faces a semicircular groove portion 48c provided on the opposite inner side surface of the hexagonal hole 48a. Further, a flange portion 46 is formed at the upper end of the tubular body 4b, and a tensioning tool 43 that moves in and out in the radial direction by a hydraulic cylinder 43a is provided at both radial positions on the flange portion 46. .. The tensioning tool 43 has a substantially rectangular plate shape, and the outer surface side is an arc surface along the circumferential direction of the tubular body 4b.

As shown in FIG. 5, in the air swivel mechanism 4 having the above configuration, the lower end portion of the kelly bar 2 having the pin insertion hole 2a is inserted into the square tube portion 47, and the connecting pin 21 is connected to the kelly bar 2 and the square tube portion from the side. By penetrating through both pin insertion holes 2a and 47a of 47, they are coaxially and non-rotatably connected to the keriba 2. A flange portion 47b for positioning is formed near the upper end of the square cylinder portion 47, and when the lower end portion of the kelly bar 2 is inserted into the square cylinder portion 47, the flange portion 47b is fitted with the flange on the kelly bar 2 side. When the portions (not shown) come into contact with each other, the pin insertion holes 2a and 47a of the keriba 2 and the square cylinder portion 47 are set to match.

On the other hand, the air swivel mechanism 4 inserts the hexagonal shaft portion 52 projecting from the top surface of the upper end shaft portion 5a into the hexagonal hole 48a of the connecting cylinder portion 48 with respect to the down-the-hole hammer 5, and a pair from the side. By penetrating the connecting pins 22 into the insertion holes 48b and 48b of both pins of the connecting cylinder portion 48, the connecting pins 22 are coaxially and non-rotatably connected. The hexagonal shaft portion 52 of the down-the-hole hammer 5 is formed with a semicircular groove portion 52a in the lateral direction on the opposite side surface thereof, and when the hexagonal shaft portion 52 is inserted into the hexagonal hole 48a of the air swivel mechanism 4. The semicircular groove portions 48c and 52a of both are combined to form a circular hole, and the connecting pin 22 is inserted into the circular hole so that the hexagonal shaft portion 52 cannot be pulled out from the hexagonal hole 48a.

The lower end side of the air hose 7 is connected to the air hose connection port 41 of the air swivel mechanism 4. As shown in FIG. 5, the elbow pipe 71 is first screwed and fixed to the air hose connection port 41, and the adapter is fixed to the lower end of the hose. 72 is screwed and connected to the elbow tube 71. A compressed air introduction port 50 is opened at the end surface of the hexagonal shaft portion 52 of the down-the-hole hammer 5, and the compressed air supplied through the air hose 7 passes through the annular flow path 40 and the air supply path 42 of the air swivel mechanism 4. After that, it is supplied to the down-the-hole hammer 5 from the compressed air introduction port 50.

As described above, the down-the-hole hammer 5 is attached to the keriba 2 via the air swivel mechanism 4 in the second step, and then the down-the-hole hammer 5 is inserted into the steel pipe sheet pile 1 as shown in FIG. 3 as the third step. The bottom is landed on the hard support layer Gh, and the hard support layer Gh is excavated by the operation of the down-the-hole hammer 5. As shown in FIG. 6, the down-the-hole hammer 5 has a diameter-expanding hammer bit 51 mounted on the lower end side of the hammer casing 50, and the hammer bit 51 is reduced in diameter and is below the lower end of the steel pipe sheet pile 1. By projecting and rotating in the excavation direction, the plurality of bid heads 51a of the hammer bit 51 are automatically displaced to the enlarged diameter state due to frictional resistance with the ground. Therefore, along with the expanded diameter excavation, the steel pipe sheet pile 1 enters the hard support layer Gh on the tip side by its own weight and is rooted.

In excavation of the hard support layer Gh by the down-the-hole hammer 5, the compressed air is supplied into the hammer casing 50 while rotating integrally with the keriba 2, and the internal piston (not shown) hits the top end of the hammer bid 51. The gravel and bedrock of the hard support layer Gh are crushed by the rotational impact action of the bid head 51a accompanying this. Therefore, in deep construction, the thin keriba 2 becomes long and easily swings, but as shown in FIG. 6, the pair of tensioning tools 43, 43 attached to the air swivel mechanism 4 is extended to operate the steel pipe sheet pile 1. Since the Keriba 2 is prevented from swinging by being stretched inside, the down-the-hole hammer 5 is held in a stable posture by the steel pipe sheet pile 1, so that the hard support layer Gh can be excavated efficiently and quickly. Further, since the down-the-hole hammer 5 is attached to the lower end of the kelly bar 2 via the air swivel mechanism 4, the air hose 7 is connected to the cylinder 4b on the non-rotating side of the air swivel mechanism 4 and supplied from the air compressor 6. Compressed air for operation can be introduced through the air hose 7 without any trouble.

When the embedding of the steel pipe sheet pile 1 with respect to the hard support layer Gh at a predetermined depth (usually about 1 to 2 m) is completed by excavation with the down-the-hole hammer 5, the down-the-hole hammer 5 is extracted from the steel pipe sheet pile 1, and as a fourth step, As shown in FIG. 7A, concrete C is cast and hardened in the steel pipe sheet pile 1. The concrete C may be cast to a height exceeding at least the embedding portion (the portion penetrating into the hard support layer Gh) of the steel pipe sheet pile 1, and earth and sand Sa may be filled above the casting layer of the concrete C. In addition, as the earth and sand Sa, the earth and sand excavated by the drilling bucket 3 in the first step may be backfilled.

In the bridge foundation construction, as shown in FIG. 7 (b), a plurality of steel pipe sheet piles 1 are connected to each other by a joint 1a, and they are sequentially built in parallel through the above-mentioned first to fourth steps. After forming the outer peripheral wall body 10a of the bridge foundation 10 by arranging it in the well, the inside of the outer peripheral wall body 10a is discharged to a predetermined depth, and the reinforcing bars are arranged inside the discharged soil to form the bottom concrete. Is placed, and a reinforced concrete bridge pier is constructed on this bottom plate as shown in FIG. 7 (c). As a result, the outer peripheral wall body 10a has extremely high yield strength as a bridge foundation because the steel pipe sheet piles 1 connected to each other are rooted in the hard support layer Gh.

Although detailed illustration of the joint 1a of the steel pipe sheet pile 1 is omitted, joint portions provided in advance along the longitudinal direction on both outer peripheral sides of each steel pipe sheet pile 1 are engaged with each other by the adjacent steel pipe sheet piles 1 and 1. It is integrated together, and various conventionally known joint forms can be adopted. As a typical joint form, a PP type that engages joint portions made of steel pipes with vertical cuts, and a joint portion made of similar steel pipes and a joint portion made of T-shaped steel are engaged. There are PT type, LT type that engages a joint portion made of a pair of angle steels arranged opposite to each other and a joint portion made of T-shaped steel. Further, the well cylinder arrangement of the steel pipe sheet pile 1 for constructing the outer peripheral wall body 10a is not limited to the oval shape illustrated in FIG. 7B, and various other annular shapes such as a circle and a rectangle can be adopted.

As the down-the-hole hammer 5, any existing down-the-hole hammer 5 can be used as long as it includes a diameter-expanding hammer bit 51 without any particular limitation. There are no particular restrictions on the number and form of the bid heads 51a in the enlarged diameter hammer bit 51. Further, the tensioning tools 43 in the air swivel mechanism 4 may be three or four evenly arranged in the circumferential direction, in addition to the pair on both sides in the radial direction as in the embodiment, and the shapes of the tensioning tools 43 are also various. Can be set.

The present invention is not limited to the vibration method using the vibrating force of the vibro hammer V exemplified in the embodiment as a means for embedding the steel pipe sheet pile 1 in the ground until the tip reaches the hard support layer Gh in the first step. For example, an underground digging method in which the steel pipe sheet pile 1 is submerged in the ground by its own weight and press-fitting or light tapping while excavating the tip side with an auger screw or drilling bucket inserted and arranged inside the steel pipe sheet pile 1, hydraulic hammer, It is also possible to adopt a striking method in which the head of the steel pipe sheet pile 1 is hit with a diesel hammer, a drop hammer or the like to drive it into the ground, or a press-fitting method in which the steel pipe sheet pile 1 is press-fitted into the ground by applying static pressure by flood control. However, from the viewpoint of construction efficiency, the vibration method using the illustrated Vibrohammer V is recommended. In the embodiment, a crawler crane M serving as an earth drill excavator is used for driving the steel pipe sheet pile 1 by the vibro hammer V in the first process, but the driving work by the vibro hammer V is performed by a crawler crane different from the earth drill excavator. You may go at.

The construction method of the steel pipe pile of the present invention is not limited to the bridge foundation construction exemplified in the embodiment, but also the construction of quays, jetties, breakwaters, river revetments, road retaining walls, etc. using steel pipe sheet piles, and ordinary steel pipe piles (single pipe). It can also be applied to the construction of pile foundations of various buildings according to the form), and is particularly suitable for large-depth construction that requires rooting in the hard support layer Gh at a depth of 50 m or more from the pile head position.

1 Steel pipe sheet pile (steel pipe pile)
1a Fittings 2 Keriba 3 Drilling bucket 4 Air swivel mechanism 4a Shaft body 4b Cylinder body 40 Circular flow path 41 Air hose connection port 42 Air supply path 43 Strut tool 5 Down the hole hammer 51 Expanded diameter hammer bit 6 Air compressor (compressed air supply source)
10 Bridge foundation 10a Outer wall body C Concrete d Depth of hard support layer from pile head position Gh Hard support layer M Crawler crane (earth drill excavator)
V Vibro Hammer

Claims (6)

The steel pipe pile is embedded in the ground until the tip reaches the hard support layer, and the earth and sand in the steel pipe pile is removed by rotating and raising and lowering the drilling bucket attached to the lower end of the keriba held by the earth drill excavator. The first process of discharging and
After discharging almost all of the earth and sand in the steel pipe pile, a down-the-hole hammer equipped with a diameter-expanding hammer bit is attached to the lower end of the Keriba from which the drilling bucket has been removed via an air swivel mechanism, and the air swivel mechanism and compressed air are supplied. The second process of connecting the air hose for operating the down-the-hole hammer between the source and
The down-the-hole hammer attached to the keriba is inserted into the steel pipe pile to land on the bottom, and the hard support layer is excavated to a predetermined depth by the operation of the down-the-hole hammer, and the tip of the steel pipe pile is excavated along with the enlarged excavation. The third step of fitting the side into the hard support layer by its own weight,
After the tip end side of the steel pipe pile reaches a predetermined depth in the hard support layer, the fourth step of placing concrete in the steel pipe pile from which the down-the-hole hammer is extracted, and
A method of constructing steel pipe piles, which is characterized by sequentially passing through. In the air swivel mechanism, a cylinder having an air hose connection port on the outer periphery is airtightly fitted to a shaft body that concentrically connects the upper and lower ends to a keriva and a down-the-hole hammer so that the shaft body and the cylinder body can be connected to each other. The air hose connection port and the air supply path on the shaft body side communicate with each other through the annular flow path formed between them, and the tensions that move in and out in the radial direction at a plurality of locations evenly distributed in the circumferential direction on the outside of the cylinder. The method for constructing a steel pipe pile according to claim 1, wherein the tool is provided. The method for constructing a steel pipe pile according to claim 1 or 2, wherein the hard support layer is at a depth of 50 m or more from the pile head position. The steel pipe pile according to any one of claims 1 to 3, wherein in the first step, a steel pipe pile is driven into the ground by a vibrating force of a vibro hammer, and then the earth and sand in the steel pipe pile is discharged by the bucket. Construction method. The method for constructing a steel pipe pile according to any one of claims 1 to 4, wherein the steel pipe piles are steel pipe sheet piles in which a plurality of steel pipe piles are sequentially driven in parallel while being connected via mutual joints. The method for constructing a steel pipe pile according to claim 5, wherein a plurality of steel pipe sheet piles are sequentially driven from the water into the bottom ground so as to be arranged in a ring shape to form an outer wall body of a bridge foundation.

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