JP2020070687A - Construction method for steel pipe pile - Google Patents

Abstract

To provide a construction method for steel pipe piles that can easily insert and reliably embed the tip of a steel pipe piles even when there are hard support layers at a great depth of 50 meters or more from the pile head.SOLUTION: The construction method for steel pipe piles performs the following steps in order: a first step for embedding a steel pipe sheet pile 1 underground to reach a hard support layer Gh together with discharging earth and rocks in the steel pipe sheet pile 1 using a drilling bucket with a kelly-bar 2; a second step for attaching a down-the-hole hammer 5, to the lower end of the kelly-bar 2 instead of the drilling bucket, that includes a diameter expandable hammer pit 51 via an air swivel mechanism 4, and connecting an air hose 7 between the air swivel mechanism 4 and an air compressor 6; a third step for inserting the down-the-hole hammer 5 into a steel pipe pile firmly, excavating the hard support layer Gh to a predetermined depth while enlarging the hole diameter, and fitting the tip of the steel pipe sheet pile 1 into the hard support layer Gh; and a fourth step for installing concrete in the steel pipe sheet pile 1 from which the down-the-hole hammer 5 has been removed.SELECTED DRAWING: Figure 3

Description

  TECHNICAL FIELD The present invention relates to a construction method suitable for, for example, forming an outer peripheral portion of a bridge foundation with a steel pipe sheet pile, particularly when a large-diameter steel pipe pile is built in at a large depth.

  Generally, when building a retaining wall facing a water area such as a bridge foundation, a quay, or a seawall using a large-diameter steel pipe sheet pile, the vibration that drives the steel pipe sheet pile into the ground by the vibrating force of a vibro hammer suspended by a crane. Construction method, while excavating the tip side with an auger screw or drilling bucket that is placed inside the steel pipe sheet pile, the steel pipe sheet pile is submerged in the ground by its own weight and press-fitting or tapping, a hydraulic hammer, a diesel hammer, A hitting method for hitting the head of a steel pipe sheet pile with a drop hammer or the like to drive it into the ground, and a press-fitting method for applying a static pressure by hydraulic pressure to the steel pipe sheet pile to press it into the ground are adopted (Non-Patent Documents 1 and 2). ).

  However, if there is a hard support layer consisting of gravel layer or bedrock at a large depth of 50 m or more from the pipe head and it is necessary to insert the tip side of the steel pipe sheet pile into the support layer, the tip of any method Although the steel pipe sheet piles can be built up while reaching the support layer, it is extremely difficult to insert the steel pipe sheet pile into the support layer thereafter. This is because in the vibration method, impact method, press-fitting method, etc., the length of the steel pipe sheet pile increases, the friction resistance against the ground increases, and the rigidity of the steel pipe sheet pile as a whole decreases, so This is because the force, the striking force in the striking method, and the pressing force in the press-fitting method do not act sufficiently to penetrate the support layer. On the other hand, in the middle excavation method using an auger screw, the auger screw is additionally drilled in correspondence with a large depth, but the rigidity of the auger screw itself decreases as the length increases, so that it becomes difficult to dig a hard support layer. Further, in the method of drilling with a drilling bucket, the drilling bucket is attached to the lower end of a kerry bar that is held by a crane so that it can be raised and lowered and rotated, and it excavates while adding the kerry bar in response to a large depth. As a result, the rigidity is lost, and bending, twisting, or vibration occurs, so that the rotating force and the pressing force applied to the drilling bucket are insufficient, and the hard support layer cannot be excavated.

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

  In view of the above-mentioned circumstances, the present invention provides a method for constructing a steel pipe pile including a steel pipe sheet pile, in which even if 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 present in the support layer. It is an object of the present invention to provide a means for allowing a side to be easily penetrated and to be firmly rooted, thereby enabling high-bearing strength and high-yield large-depth erection construction.

  The method for constructing a steel pipe pile according to the invention of claim 1 shows a steel pipe pile (steel pipe sheet pile 1) with its tip reaching the hard support layer Gh if the means for achieving the above object is indicated by the reference symbols in the drawings. The first step of discharging the earth and sand in the steel pipe pile by rotating and moving up and down the drilling bucket 3 attached to the lower end of the kelly bar 2 held by the earth drill excavator M while being buried in the ground until After discharging almost all the amount of earth and sand in the steel pipe pile, a down-the-hole hammer 5 equipped 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, and the air swivel mechanism 5 is attached. 4 and the compressed air supply source (air compressor 6) between the second step of connecting the down-the-hole hammer operating air hose 7, and attach to the kerry bar 2. The down-the-hole hammer 5 is inserted into the steel pipe pile to reach the bottom, and the hard support layer Gh is expanded to a predetermined depth by the operation of the down-the-hole hammer 5, and the tip side of the steel pipe pile is hardened along with the expanded diameter drilling. Third step of inserting the steel pipe pile into the support layer Gh by its own weight, and after the tip side of the steel pipe pile reaches a predetermined depth in the hard support layer Gh, the concrete C is placed in the steel pipe pile from which the down-the-hole hammer 5 is pulled out. It is characterized by sequentially performing four steps.

  According to the invention of claim 2, in the method for constructing a steel pipe pile according to claim 1, the air swivel mechanism 4 is provided with a shaft body 4a for concentrically connecting the upper and lower ends to the kerry bar 2 and the down the hole hammer 5, and an air hose connection port 41 on the outer periphery. A cylindrical body 4b having a cylindrical shape is fitted in a relatively rotatable manner in an airtight manner, and an air hose connection port 41 and an air supply on the shaft body 4b side are supplied to an annular flow passage 40 formed between the shaft body 4a and the cylindrical body 4b. In addition to communicating with the passage 42, a plurality of struts 43 are provided on the outer side of the cylindrical body 4b, which are equally arranged in the circumferential direction, so as to extend and retract in the radial direction.

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

  The invention of claim 4 is the method for 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 It is characterized in that the earth and sand are discharged by the drilling bucket 3.

  The invention of claim 5 is the method for constructing a steel pipe pile according to any one of claims 1 to 4, wherein the steel pipe pile 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. I am trying.

  According to the invention of claim 6, in the method for constructing a steel pipe pile according to claim 5, the plurality of steel pipe sheet piles 1 are sequentially driven from above water to the bottom of the sea to form the outer peripheral wall 10a of the bridge foundation 10. It is supposed to be formed.

  The effects of the present invention will be specifically described below 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 of the kerry bar 2 is used. Although it is discharged by the drilling bucket 3 attached to the lower end, in the next second step, instead of the drilling bucket 3, a down-the-hole hammer 5 provided with a diameter-expanding hammer bit 51 is attached to the kerry bar 2 via the air swivel mechanism 4. .. Then, in the third step, by operating the down-the-hole hammer 5, the diameter of the hard support layer Gh is excavated to a predetermined depth, and accordingly, the tip side of the steel pipe pile is fitted into the support layer Gh by its own weight. It is possible to efficiently and easily and reliably insert the steel pipe pile into the hard support layer Gh, which has been difficult in the past. Then, in the fourth step, by placing concrete C in the steel pipe pile from which the down-the-hole hammer 5 has been pulled out, a high-strength pile can be constructed. The down-the-hole hammer 5 is rotated by the operation, but is attached to the lower end of the kelly bar via the air swivel mechanism 4, so that it is fed 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 second aspect of the invention, in the air swivel mechanism 4, the cylindrical body 4b having the air hose connection port 41 on the outer periphery is airtightly and rotatably externally attached to the shaft body 4a concentrically connected to the kerry bar 2 and the down the hole hammer 5. The tubular body 4a is provided with a plurality of bracing members 43 that move in and out in the radial direction. The bracing members 43 are stretched so as to abut or come close to the inner peripheral surface of the steel pipe pile. By letting it out, the down-the-hole hammer 5 can be held in a stable posture in which the down-the-hole hammer 5 does not swing in the steel pipe pile, so a high excavation efficiency by the down-the-hole hammer 5 can be secured.

  According to the invention of claim 3, in the deep-depth construction in which the hard supporting layer Gh is at a depth d of 50 m or more from the pile head position, it is extremely difficult to insert the steel pipe pile into the hard supporting layer Gh, which has been extremely difficult in the past. It can be performed efficiently, easily and surely.

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

  According to the invention of claim 5, the steel pipe 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 joints 1a. It can be easily and surely rooted to construct a wall with high yield strength.

  According to the invention of claim 6, when the plurality of steel pipe sheet piles 1 are sequentially driven from above water to the bottom of the sea to form the outer peripheral wall body 10a of the bridge foundation 10, the hard support layer Gh is Even if it is located at a large depth, the outer peripheral wall body 10a having a high yield strength can be reliably built in and constructed.

It is a longitudinal side view showing the driving situation 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 concerning the present invention to bridge foundation construction. It is a vertical side view which shows the discharge condition of the sand in the steel pipe sheet pile by the drilling bucket of the same 1st process. It is a vertical side view which shows the excavation condition of the hard support layer by the down the hole hammer of the 3rd process in the same 1st embodiment. The air swivel mechanism which interposes in the attachment part with respect to the kerry bar of the same down the hole hammer is shown, (a) is a top view, (b) is a principal part vertical front view. It is a development perspective view which shows the connection part of a kerry bar and a down the hole hammer via the same air swivel mechanism. It is a vertical side view which expands and shows the excavation condition of the hard support layer by the down the hole hammer loaded in the steel pipe sheet pile. The same bridge foundation construction is shown, (a) is a vertical cross-sectional side view showing the state of placing concrete in the steel pipe sheet pile in the fourth step, and (b) is the Izutsu paradigm of steel pipe sheet piles that form the outer peripheral wall of the bridge foundation. And (c) is a front view showing a state where bridge piers are constructed on the bridge foundation.

As described above, the method for constructing a steel pipe pile according to the present invention is characterized by sequentially performing the following first to fourth steps.
[First step] -By embedding the steel pipe pile in the ground until the tip reaches the hard support layer, and by rotating and raising / lowering the drilling bucket attached to the lower end of the kelly bar held by the earth drill excavator. , Discharge the earth and sand in the steel pipe pile.
(Second step) ... After discharging substantially all the amount of 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 kelly bar 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 kelly bar is inserted into the steel pipe pile to reach the bottom, and the hard support layer is expanded and drilled to a predetermined depth by the operation of the down-the-hole hammer. 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 side of the steel pipe pile reaches a predetermined depth in the hard support layer, concrete is placed in the steel pipe pile from which the down-the-hole hammer has been removed.

  Below, one embodiment which applied the construction method of the steel pipe pile of the present invention to bridge foundation construction is explained concretely with reference to drawings. In this bridge foundation construction, as shown in Fig. 1, at the construction position in the water area, a plurality of steel pipe sheet piles 1 as steel pipe piles are sequentially built in parallel from the water surface to the water bottom ground, whereby the outer peripheral wall of the bridge foundation is constructed. It is what builds the body. Then, the water bottom ground G is composed of a mud layer Gm, a sediment layer Gs of sand and gravel, and a hard support layer Gh composed of coarse gravel layer and bedrock in order from the top, and the pile head position of the hard support layer Gh. The depth d from is at a large depth of 50 m or more. In addition, the diameter of the steel pipe in the steel pipe sheet pile 1 is about 1 to 2 m. In addition, W in a figure shows a water layer.

  In the construction method of this embodiment, in the first step, as shown in FIG. 1, first, as shown in FIG. 1, an earth drill excavator equipped with a boom B and a front frame F is mounted on a flat carrier S of about 300 tons floating on the water. A crawler crane M of 60 to 65t class that can be configured is mounted, and the top of the steel pipe sheet pile 1 is gripped by a vibro hammer V suspended by a boom B thereof, and the steel pipe sheet pile 1 is vibrated at the bottom of the water by 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 by welding and replenished 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 detached from the steel pipe sheet pile 1 and lowered onto the flat carrier S, 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 an earth drill excavator. The yoke Y is composed of a kelly bar driving device KD and a rotary table RT below which a pair of hose reels Hr are installed. The rotary table RT has a rotary coupling for hydraulic pressure and electric wiring (not shown). ) Is provided.

  Next, in the crawler crane M of this earth drill excavator specification, the square tube-shaped kelly bar 2 is suspended and supported by the boom B through the swivel joint J and is vertically slidably inserted into the yoke Y. The drilling bucket 3 is attached to the lower end of the steel pipe sheet pile 1, and the drilling bucket 3 is inserted into the steel pipe sheet pile 1 that has reached the hard support layer Gh as shown in FIG. Then, by repeating the rotation and lifting operation 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 deeper. Corresponding to the above, the kerry bar 2 is replenished and the soil is discharged to the lowest part in the steel pipe sheet pile 1.

  When the soil in the steel pipe sheet pile 1 that has reached the hard support layer Gh is completed in this way, as a second step, the drilling bucket 3 extracted from the steel pipe sheet pile 1 is removed from the kerry bar 2 and the lower end of the kerry bar 2 is 3, the down-the-hole hammer 5 is attached via the air swivel mechanism 4, and a hose reel 8 is interposed between the air compressor 6 of the compressed air supply source mounted on the flat carrier S and the air swivel mechanism 4. And 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 is provided with a substantially short cylinder-shaped cylinder body 4b via upper and lower bearings 44 and a seal ring 45. Relatively rotatable and fitted in an airtight manner. An annular flow passage 40 is formed between the shaft body 4a and the cylindrical body 4b, and an air hose connection port 41 opening on the peripheral surface of the cylindrical body 4b communicates with the annular flow passage 40 and the shaft body 4b side. An air feed passage 42 extending along the axial direction of the above is communicated with the annular flow passage 40 via a ventilation hole 42a in the radial direction.

  The shaft body 4a of the air swivel mechanism 4 has a rectangular tubular portion 47 on the upper end side, and pin insertion holes 47a are formed in the middle portions of the opposing walls thereof, and a lower end side constitutes a connecting tubular portion 48 having a circular outer periphery. The inside of the connecting tubular portion 48 becomes a hexagonal hole 48a opened downward, and the air feeding 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 inner surface of the hexagonal hole 48a facing each other. Further, a flange portion 46 is formed at the upper end of the cylindrical body 4b, and a bracing tool 43 is provided on both sides of the flange portion 46 in the radial direction so as to move in and out by the hydraulic cylinders 43a in the radial direction. .. The bracing tool 43 has a substantially rectangular plate shape, and its 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-described configuration, the lower end portion of the kelly bar 2 having the pin insertion hole 2a is fitted into the square tube portion 47, and the connecting pin 21 is laterally attached to the kelly bar 2 and the square tube portion. By being inserted through both pin insertion holes 2a, 47a of 47, they are coaxially connected to the kelly bar 2 so as not to rotate relative to each other. A flange portion 47b for positioning is formed near the upper end of the square tube portion 47, and when the lower end portion of the kelly bar 2 is inserted into the square tube portion 47, the flange portion 47b is provided with a flange on the side of the kelly bar 2. The pin insertion holes 2a and 47a of the kelly bar 2 and the rectangular tube portion 47 are set to be aligned with each other by abutting the portions (not shown).

  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 of the down the hole hammer 5 into the hexagonal hole 48a of the connecting tubular portion 48, and a pair of sideways is provided. By inserting the connecting pin 22 into both the pin insertion holes 48b, 48b of the connecting cylinder portion 48, the connecting pin 22 is coaxially connected so as to be relatively non-rotatable. It should be noted that the hexagonal shaft portion 52 of the down the hole hammer 5 is formed with lateral semicircular groove portions 52a on opposite side surfaces thereof, and when the hexagonal shaft portion 52 is inserted into the hexagonal hole 48a of the air swivel mechanism 4. The semi-circular 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, but as shown in FIG. 5, first, the elbow pipe 71 is 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 to the elbow pipe 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 flows through the annular flow passage 40 and the air feed passage 42 of the air swivel mechanism 4. Then, the compressed air is introduced into the down the hole hammer 5 through the inlet 50.

  After the down the hole hammer 5 is attached to the kelly bar 2 via the air swivel mechanism 4 in the second step as described above, the down the hole hammer 5 is inserted into the steel pipe sheet pile 1 as the third step as shown in FIG. The hard support layer Gh is bottomed, 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 hammer casing 50 with a diameter-expanding hammer bit 51 mounted on the lower end side thereof. The hammer bit 51 is below the lower end of the steel pipe sheet pile 1 in a reduced diameter state. By protruding and rotating in the excavating direction, the plurality of bid heads 51a of the hammer bit 51 are automatically displaced to the expanded diameter state due to frictional resistance with the ground. Therefore, the steel pipe sheet pile 1 enters the hard support layer Gh on the tip side by its own weight along with the diameter expansion excavation and is embedded therein.

  In excavating the hard support layer Gh by the down the hole hammer 5, compressed air is supplied into the hammer casing 50 while rotating integrally with the kerry bar 2, so that an internal piston (not shown) strikes the top end of the hammer bid 51. Then, the gravel and the bedrock of the hard support layer Gh are crushed by the rotation hitting action of the bid head 51a accompanying this. In the deep-sea construction, however, the thin kelly bar 2 becomes long and easily swings. However, as shown in FIG. 6, the pair of bracing tools 43, 43 attached to the air swivel mechanism 4 are extended to operate the steel pipe sheet pile 1. Since the kerry bar 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, and thus the hard support layer Gh can be efficiently and quickly excavated. 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 cylindrical body 4b, which is the non-rotating side of the air swivel mechanism 4, to supply from the air compressor 6. The compressed air for operation can be introduced through the air hose 7 without any trouble.

  When excavation with the down-the-hole hammer 5 completes the rooting of the hard support layer Gh of the steel pipe sheet pile 1 to a predetermined depth (usually about 1 to 2 m), the down-the-hole hammer 5 is pulled out from the steel pipe sheet pile 1, and as a fourth step, As shown in FIG. 7A, concrete C is poured into the steel pipe sheet pile 1 and hardened. The concrete C may be cast to a height exceeding at least the root insertion portion (penetration portion into the hard support layer Gh) of the steel pipe sheet pile 1, and the earth Sa and sand may be filled above the casting layer of the concrete C. As the earth and sand Sa, the earth excavated and discharged 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 with a joint 1a, and 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 them in a well, the inner side of the outer peripheral wall body 10a is discharged to a predetermined depth, and the reinforcing bars are arranged on the inner side of the excavated earth to form the bottom concrete. Then, a reinforced concrete bridge pier is constructed on this bottom plate as shown in Fig. 7 (c). Since the steel pipe sheet piles 1 connected to each other are embedded in the hard supporting layer Gh, the outer peripheral wall 10a has an extremely high yield strength as a bridge foundation.

  Although the joint 1a of the steel pipe sheet pile 1 is not shown in detail, the joint portions provided in advance on both sides of the outer periphery of each steel pipe sheet pile 1 along the longitudinal direction are engaged with each other between the adjacent steel pipe sheet piles 1, 1. They are integrated and integrated, and various conventionally known joint configurations can be adopted. As a typical joint form thereof, a P-P type in which joints made of steel pipes having longitudinal cuts are engaged with each other, and a joint made of similar steel pipes and a joint made of T-shaped steel are engaged. There are a P-T type, an L-T type and the like in which a joint portion made of a pair of chevron steel and a joint portion made of a T-shaped steel are engaged with each other. Further, the well pipe arrangement of the steel pipe sheet piles 1 that construct 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, an existing one can be used without particular limitation as long as it has the diameter-expanding hammer bit 51. There is also no particular limitation on the number and form of the bid heads 51a in the expanded hammer bit 51. Further, the bracing tool 43 in the air swivel mechanism 4 may be three or four equally distributed in the circumferential direction other than the pair of the bracing tools on both sides in the radial direction as in the embodiment, and the bracing tool 43 may have various shapes. Can be set.

  In the present invention, the means for burying the steel pipe sheet pile 1 in the ground until the tip reaches the hard support layer Gh in the first step is not limited to the vibrating method using the vibrating force of the vibro hammer V exemplified in the embodiment. For example, while excavating the tip side with an auger screw or a drilling bucket that is inserted and arranged inside the steel pipe sheet pile 1, the steel pipe sheet pile 1 is submerged in the ground by its own weight and press-fitting or tapping, a hydraulic hammer, A hitting method of hitting the head of the steel pipe sheet pile 1 by hitting it into the ground with a diesel hammer, a drop hammer, or the like, or a press-fitting method of pressurizing the steel pipe sheet pile 1 into the ground by applying a static pressure to the steel pipe sheet pile 1 can also be adopted. However, from the viewpoint of construction efficiency, the vibration method using the illustrated vibro hammer V is recommended. In the embodiment, the crawler crane M, which is an earth drill excavator, is used for driving the steel pipe sheet pile 1 by the vibro hammer V in the first step, but the driving construction by the vibro hammer V is different from the earth drill excavator. You may go to.

  The construction method of the steel pipe pile of the present invention is not limited to the bridge foundation construction exemplified in the embodiment, and construction of a quay wall, a jetty, a breakwater, a river bank, a road retaining wall, etc. by a steel pipe sheet pile, and a normal steel pipe pile (single pipe It is also applicable to the construction of pile foundations of various structures according to the form), and is particularly suitable for large-depth construction that requires rooting into 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 Joint 2 Kelly bar 3 Drilling bucket 4 Air swivel mechanism 4a Shaft body 4b Cylindrical body 40 Annular flow passage 41 Air hose connection port 42 Air feed passage 43 Stretching tool 5 Down the hole hammer 51 Expanding type hammer bit 6 Air compressor (compressed air supply source)
10 Bridge foundation 10a Outer peripheral wall C Concrete d Depth of hard supporting layer from the pile head position Gh Hard supporting layer M Crawler crane (earth drill excavator)
V vibro hammer

Claims (6)

While embedding the steel pipe pile in the ground until the tip reaches the hard support layer, by rotating and elevating the drilling bucket attached to the lower end of the kerry bar held by the earth drill excavator, the soil in the steel pipe pile is removed. The first step of discharging,
After discharging almost all the amount of earth and sand in the steel pipe pile, through the air swivel mechanism at the lower end of the kelly bar from which the drilling bucket was removed, a down-the-hole hammer equipped with a diameter-expanding hammer bit was attached, and the air swivel mechanism and compressed air supply A second step of connecting an air hose for down the hole hammer operation with the source,
The down-the-hole hammer attached to the kelly bar is inserted into the steel pipe pile to reach the bottom, and the hard support layer is expanded to a predetermined depth by the operation of the down-the-hole hammer, and the tip of the steel pipe pile is accompanied by the expanded diameter drilling. A third step of fitting the side into the hard support layer by its own weight,
After the tip side of the steel pipe pile reaches a predetermined depth in the hard support layer, a fourth step of placing concrete in the steel pipe pile from which the down-the-hole hammer is extracted,
A method for constructing a steel pipe pile, characterized by sequentially undergoing the steps.   The air swivel mechanism is such that a cylinder having an air hose connection port on the outer periphery is fitted to the shaft body that concentrically connects the upper and lower ends to the kelly bar and the down the hole hammer in an airtight manner so that the shaft body and the cylinder body are relatively rotatable. The annular hose connected between the air hose connection port and the shaft-side air supply path communicates with each other. The method for constructing a steel pipe pile according to claim 1, wherein a 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 the first step is to drive the steel pipe pile into the ground by vibrating force of a vibro hammer and then discharge the earth and sand in the steel pipe pile by the bucket. Construction method.   The method for constructing a steel pipe pile according to claim 1, wherein the steel pipe pile is a steel pipe sheet pile in which a plurality of steel pipe piles are sequentially driven in parallel while being connected to each other through 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 above the water to the bottom of the sea to form an outer peripheral wall of the bridge foundation.

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