JP6847899B2 - Ring-shaped tip hardware - Google Patents

Description

The present invention relates to a ring-shaped tip metal fitting of a steel pipe (casing pipe) used in the middle digging pile method used for foundation piles such as bridge foundation piles and building foundation piles.

The middle digging method is a pile driving method that is carried out by techniques such as the earth auger method, centering on the relatively soft ground that is often found in urban areas of Japan developed from river basins.

The middle digging method, which is a typical method of the existing technology, is a ready-made pile placed along the leader in an infinite track type base machine (three-point support type pile driver, etc.) as described in Patent Document 1 below. An auger screw having a diameter smaller than the inner diameter of the steel pipe pile was placed in a certain steel pipe pile, and the auger screw was rotated by an auger drive device to excavate the ground at the tip of the steel pipe pile and sunk the steel pipe pile to reach the support layer. By the way, it is a method of forming a pile by performing tip treatment.
Japanese Patent No. 3170604

As the tip treatment, in order to increase the bearing capacity of the pile after subsidence, measures such as driving the pile into the support layer for a predetermined length or injecting cement milk into the support layer to integrate the pile with the pile are taken.

The former is a final striking method in which the hollow part at the tip of the pile is filled with soil by striking to close the tip and penetrate into the support layer to obtain supporting force, and the latter is a mortar inside and outside the pipe at the lower end. Advanced treatment is performed by placing cement-based materials such as cement milk and concrete (in some cases, kneading with the ground).

In the case of advanced treatment in which cement-based materials are placed in this way, the load of superstructures such as bridges or buildings is applied to the foundation piles to be placed in the order of steel pipe piles, anti-slip, concrete inside steel pipe piles, and supporting ground. A tubular pile (inner space) stopper may be provided so that the load can be transmitted smoothly.

As shown in the following non-patent documents, this slip stopper uses a flat steel pipe without ribs at the pile head, and a protrusion ring (flat steel processed into a ring shape) is welded in multiple stages at the lower end of the steel pipe. It was installed by.
Middle digging pile method for steel pipe pile foundations and steel pipe sheet pile foundations for road bridges (cement milk spouting stirring method) Construction guidelines (draft) Published by General Incorporated Association Steel Pipe Pile and Steel Sheet Sheet Technology Association in March 2015 Figure-2 .10 (d)

As shown in FIG. 5, a protrusion ring 2 serving as a shear key is provided at the tip of a steel pipe (casing pipe) 1 filled with concrete at intervals of upper and lower parts.

On the other hand, when the foundation piles are required to be firmly embedded in solid ground such as rock formations, hard ground that cannot be excavated by earth auger or down-the-hole hammer, which has a good reputation for excavation ability of rock, is used. By placing piles in the bedrock or in the bedrock, the placed piles can secure sufficient bearing capacity.

As shown in FIGS. 3 and 4, the down-the-hole hammer 6 is a bit head 8 in which a plurality of button-shaped tips 8a made of a hard material such as cemented carbide are fixed to the tip surface as an excavation tool for excavating the ground or earth and sand. It has a device 7 which is an air hammer that gives a blow to the bit head 8, and a drive shaft 10 is fixedly installed at the upper end of the down-the-hole hammer 6, and the shaft 10 is operably connected to a rotary drive device.

In the figure, reference numeral 9 denotes a projecting portion (device guide portion) for the down-the-hole hammer drilling device to hit and press-fit the steel pipe, and the projecting portion 9 forms a ring-shaped step portion 9a.

Although it is also described in the following patent document, when the down-the-hole hammer 6 is used, a ring-shaped tip metal fitting (casing top) 11 which is a ring-shaped metal fitting is attached to the tip of the steel pipe (casing pipe) 1, and the ring-shaped tip metal fitting 11 is attached. The rear end surface is arranged so as to come into contact with the step portion 9a.
Japanese Unexamined Patent Publication No. 2006-283516

The ring-shaped tip hardware 11 has a thick portion 11b on the tip side (lower side in FIG. 3) and a thin portion 11a on the rear end side (upper side in FIG. 3). A tapered surface portion 11c is formed between the taper surface portion 11a and the taper surface portion 11c. The tip of the casing pipe 1 is welded 12 to the tapered surface portion 11c.

The patent document 2 relates to a so-called diameter-expanding excavator, and when it is rotated and sent in the drilling direction with respect to the excavated material, three bit heads 8 are attached to each mounting shaft due to excavation resistance from the excavated material. Rotating around the axis of the portion, a part of the bit head 8 protrudes from the outer peripheral surface of the device 7, and the diameter of the bit portion is expanded. By excavating in the drilling direction in this state, a drilling hole having a diameter one step larger than the outer diameter of the device 7 is formed.

On the other hand, when rotating in the opposite direction, the three bit heads 8 rotate around the axis of each mounting shaft due to the frictional resistance with the material to be excavated, and all the bit parts are located inside the outer diameter of the device 7. The diameter is reduced so that it does. The down-the-hole hammer 6 can be taken out by moving in this state to the side opposite to the drilling direction.

FIG. 4 shows the relationship between the inner surface of the steel pipe and the clearance of the down-the-hole hammer.

In the middle digging method using middle digging piles, in order to secure the tip blockage as described above, a slip stopper such as a flat bar is attached to the inner surface of the steel pipe tip and placed, and the tip is treated with cement milk and concrete.

In the case of the middle digging method using a down-the-hole hammer, a ring-shaped tip hardware, which is a construction jig, is attached to the tip of the steel pipe, but it is necessary to secure a clearance between the hammer and the ring-shaped tip hardware during construction.

However, as shown in FIG. 4, since the clearance between the inner surface of the steel pipe and the down-the-hole hammer is small, it is difficult to attach the flat bar forming the slip stopper to the ring-shaped tip hardware, and it is troublesome to attach it to the inner wall of the steel pipe. There is a problem that the processing load becomes high.

An object of the present invention is to solve the inconvenience of the above-mentioned conventional example, and when the foundation pile is required to be surely embedded in a solid ground such as a bedrock layer, when the pile is driven into such a hard ground or a bedrock. The down-the-hole hammer, which has a reputation for excavating hard ground and bedrock that cannot be excavated by the earth auger method, is used, and the piles that have been driven can secure sufficient bearing capacity, while ensuring clearance with the down-the-hole hammer. An object of the present invention is to provide a ring-shaped tip metal fitting capable of forming a tip blocking structure.

The present invention according to claim 1 for achieving the above object is a ring-shaped tip metal fitting attached to the tip of a steel pipe, which is used in a middle digging pile method in which a down-the-hole hammer is set in a steel pipe in a middle digging manner and dug. , The upper end of the part that fits into the steel pipe and enters the steel pipe is the down-the-hole hammer hitting part, and in order to close the inside of the steel pipe by filling it with concrete, it is a substantially ring-shaped metal fitting that protrudes inward in the direction perpendicular to the axis. The gist is that a plurality of sheer keys are provided at vertical intervals, and the down-the- hole hammer hit portion is formed in one of the sheer keys and protrudes in a direction perpendicular to the axis of the other sheer keys. Is.

According to the first aspect of the present invention, the striking force of the down-the-hole hammer can be used for the driving force of piles on hard ground or bedrock by using the ring-shaped tip metal fitting, and it can also be used as a slip prevention metal fitting. In down-the-hole hammer construction where a large impact force is frequently applied to piles, high-quality shear keys can be provided to steel pipe piles via ring-shaped hardware, and reliable integration with concrete can be realized, resulting in high-quality pile structures. Can be obtained.

Furthermore, by processing the ring-shaped tip hardware to prevent it from slipping, it is possible to construct a tip blocking structure while ensuring clearance, and when adding a slip stopper to the inner wall of the steel pipe, the ring-shaped tip hardware is also machined. The number of slip prevention steps and the installation section distance from the lower end can be reduced by the amount applied, and the construction load during installation can be reduced.

In addition, the striking force of the down-the-hole hammer is transmitted to the steel pipe pile via the ring-shaped tip metal by projecting the striking surface and guide surface of the ring-shaped tip hardware that the down-the-hole hammer excavation bit directly hits from other misalignment prevention portions. When doing so, wear can be prevented by preventing direct contact with the down-the-hole hammer.

The present invention according to claim 2 is a ring-shaped tip metal fitting attached to the tip of a steel pipe, which is used in a middle digging pile method in which a down-the-hole hammer is set in a steel pipe in a middle digging manner and is dug, and is fitted to the steel pipe. The upper end of the part that enters the steel pipe is the down-the-hole hammer hitting part, and in order to close the inside of the steel pipe by filling it with concrete, a shear key, which is a substantially ring-shaped metal fitting protruding inward in the direction perpendicular to the axis, is spaced vertically. A shaft provided with a plurality of spaces, the down-the-hole hammer hit portion is formed in one of the shear keys, and the lower end side has a clearance that surrounds the side surface of the down-the-hole hammer and allows the movement of the down-the-hole hammer. The gist is that the guide surface parallel to the center direction is hardened by quenching to form the guide surface.

According to the second aspect of the present invention, a guide surface parallel to the axial direction is formed so as to surround the side surface of the down-the-hole hammer and have a clearance that allows the movement of the down-the-hole hammer. By functioning as a stabilizer for the excavation bit, the posture of the down-the-hole hammer is maintained, and the straightness of excavation and pile driving can be ensured.

Moreover, by hardening the guide surface by quenching, it is possible to minimize wear even if the down-the-hole hammer is in direct contact with the hammer. Further, it is more advantageous from the viewpoint of availability and cost to quench only the minimum range than to use wear-resistant steel.

The gist of the present invention according to claim 3 is that the steel pipe is fitted with a wax, and the back surface portion near the shear key installation position is slot welded to the steel pipe to be integrated with the steel pipe .

According to the third aspect of the present invention, since the steel pipe is joined to the steel pipe by inro fitting, a backing metal is not required, and the pile core and the ring core of the ring-shaped tip metal can be easily aligned. Therefore, the production cost can be reduced.

Various evaluation methods have been proposed for the adhesion strength between steel pipes with slip stoppers on the inner surface and solidified bodies. As an example, "Railway Technical Research Institute Design Standards / Explanation Steel and Concrete Composite Structure" Things (January 2016) ”.

In the adhesion strength formula of the standard, it is shown that as the diameter-thickness ratio (steel pipe plate thickness / steel pipe diameter) increases, the adhesion strength increases due to the restraining effect of the steel pipe, and the shear key portion responsible for reliable integration with concrete. By completely fixing the vicinity of the back surface of the concrete (especially the vicinity of the back surface of the lower surface of the shear key where concrete crushing starts) with the steel pipe pile by slot welding, the effective diameter-thickness ratio can be regarded as large, which has a positive effect on the bond strength. At the same time, high quality of integration of ring-shaped tip hardware and steel pipe pile after completion can be ensured.

Further, when the non-striking surface 14 of the ring-shaped tip hardware is struck by the stepped portion 9a of the protruding portion 9, the shear key that also serves as the non-striking portion is bent in the direction of peeling from the steel pipe, and thus also serves as the non-striking portion. Deformation can be suppressed by slot welding the back surface near the shear key installation position.

As described above, the ring-shaped tip metal fitting of the present invention requires reliable penetration of the foundation pile into solid ground such as a bedrock layer, and when driving a pile into such hard ground or bedrock, The down-the-hole hammer, which has a reputation for excavating hard ground and bedrock that cannot be excavated by the earth auger method, is used, and the piles that have been driven can secure sufficient bearing capacity, while ensuring clearance with the down-the-hole hammer. It can form a tip closure structure.

It is a longitudinal side view which shows 1 Embodiment of the ring-shaped tip metal fitting of this invention. It is a longitudinal side view which shows the other embodiment of the ring-shaped tip metal fitting of this invention. It is a vertical sectional side view which shows the conventional example. It is explanatory drawing which shows the relationship between the inner surface of a steel pipe and the clearance of a down-the-hole hammer in a diameter-expanded down-the-hole hammer. It is a longitudinal side view of a steel pipe pile provided with a slip stopper by a flat bar.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows one embodiment of the middle-drilled pile method of the present invention and the slip stopper used therein, and the same components as those in FIG. 3 showing the conventional example are designated by the same reference numerals.

In the figure, 1 is a steel pipe (casing pipe), 6 is a down-the-hole hammer, and 6 is a down-the-hole hammer 6 as an excavation tool for excavating the ground and earth and sand. It has a bit head 8 to which a plurality of chips of the above are fixed and a device 7 which is an air hammer that gives a blow to the bit head 8, and a drive shaft 10 is fixedly installed at the upper end of the down-the-hole hammer 6. It is operably connected to the rotary drive.

In the figure, reference numeral 9 denotes a projecting portion (device guide portion) for the down-the-hole hammer drilling device to hit and press-fit the steel pipe, and the projecting portion 9 forms a ring-shaped step portion 9a.

In the figure, 11 is a ring-shaped tip metal fitting (casing top) attached to the tip of the steel pipe (casing pipe) 1 (the lower end in the axial direction of the tubular pile), and the ring-shaped tip metal fitting 11 is the steel pipe (casing pipe) 1. It has an outer diameter (shape) substantially the same as that of the above, and a down-the-hole hammer hit surface 14 is formed at the upper end.

The ring-shaped tip hardware 11 is welded 12 to the tip of the casing pipe 1, but the tip side (lower side in FIG. 1) is the thick portion 11b and the rear end side (upper side in FIG. 1) is the thin portion 11a. are the tapered surface portion 11c between the thick portion 11b and the thin portion 11a have been formed, the thin portion 11a is viewed write enters the steel (casing pipe) 1, is connected by spigot fitting 16 .. The down-the-hole hammer hit surface 14 is formed at the upper end of a portion that fits into the steel pipe 1 and enters the steel pipe.

The tip of the casing pipe 1 is welded 12 to the tapered surface portion 11c.

Then, in order to close the inside of the steel pipe by filling the inside of the ring-shaped tip metal fitting 11 with concrete, sheer keys 13 protruding in the direction perpendicular to the axis are provided in a plurality of upper and lower stages at intervals, and the ring-shaped tip metal fitting 11 is provided. Was also used as a slip stopper.

When the thin portion 11a enters the steel pipe (casing pipe) 1 and is connected by the inroam fitting 16, the space between the down-the-hole hammer excavator (diameter expansion bit portion) and the inner wall of the steel pipe (clearance) is narrow, and excavation is performed. Since the device has a protruding part (device guide part) for hitting and press-fitting the steel pipe, and the clearance is even smaller, in the device configuration such as a small diameter, the slip stopper should be attached above the device guide with that small clearance. However, the shear key 13 can be formed by grooving the ring-shaped tip hardware 11.

When the device guide and the casing inner diameter are configured with the proportions (ratio) shown in Fig. 4 in the device configuration such as the small diameter, there is no clearing (even if the drill rod outer diameter and casing are as shown in the figure). This is because the outer circumference of the device guide hits the slip stopper at the stage of setting the hammer (even if the inner diameter clearance is large) and cannot be inserted.

The sheer key 13 can be formed as a welded molded protrusion in addition to the grooving. Here, the weld-molded protrusion means a protrusion molded into a predetermined shape while melting the welding material.

The shear key 13 is a substantially ring-shaped convex portion protruding into the inner space of the ring-shaped tip metal fitting 11, which is a substantially ring-shaped metal fitting, and a substantially ring-shaped concave portion is provided adjacent to the substantially ring-shaped convex portion to form a step. Provided, and a plurality of them are formed with at least a vertical interval.

The down-the-hole hammer hit surface 14 of the ring-shaped tip hardware 11 is hit by a part of the excavation bit at the same time as excavation, and is formed so as to project in the direction perpendicular to the axis of the inner space of the ring-shaped tip hardware 11. The hit surface 14 was formed on one of the sheer keys 13.

The impacted surface 14 is formed so as to protect the other shear keys 13 by projecting from the other shear keys 13 in the direction perpendicular to the axis and in close contact with the down-the-hole hammer excavation bit device portion.

Further, the impacted surface 14 has been subjected to a hardening treatment 17 by quenching.

Further, the shear key 13 located at the inro fitting portion and the back surface of the impacted surface 14 are integrated with the steel pipe 1 via the slot weld 18.

Further, on the lower end side of the ring-shaped tip hardware 11, a guide surface 15 parallel to the axial direction is formed so as to surround the side surface of the down-the-hole hammer 6 and have a clearance that allows the movement of the down-the-hole hammer 6. The guide surface 15 is formed on one of the shear keys 13 (at the bottom in the figure).

The guide surface 15 functions as a stabilizer for the excavation bit of the down-the-hole hammer, so that the posture of the down-the-hole hammer is maintained and the straightness of excavation and pile driving can be ensured.

The ring-shaped tip metal fitting 11 can be made of a steel material equivalent to the material of the steel pipe pile, and further, depending on the design conditions such as the combination with the excavator, the soil quality, the use of the structure, etc., all or inside as necessary. A part of the empty part may be made of carbon steel material for machine structure (S35C, S45C, etc.), and the guide surface 15 is hardened on the assumption that (direct) contact with the device occurs like the impacted surface 14. It is formed so as to improve wear resistance by performing a hardening treatment 17 according to.

FIG. 2 shows another embodiment, in which the steel pipe (casing pipe) 1 is provided with a shear key 13 on the inner wall of the tip portion, and the tip of the steel pipe pile of the steel pipe (casing pipe) 1 with such a shear key 13 is provided. A ring-shaped tip hardware 11 was attached to the.

As a result, the ring-shaped tip hardware 11 can be integrated with the concrete more firmly than it is secured by itself, and even when adding anti-slip processing to the steel pipe pile for the purpose of such integration, the ring-shaped tip Since the hardware is processed to prevent slippage, the number of steps to prevent slippage and the installation section distance from the lower end can be reduced.

The middle digging pile method of the present invention performed by using the slip-preventing metal fitting by the ring-shaped tip metal fitting 11 of the present invention comprises a down-the-hole hammer 6 and a drive shaft 10 in a hollow portion of a tubular pile made of a steel pipe (casing pipe) 1. An excavation shaft member is inserted, and the down-the-hole hammer 6 is driven by compressed air to cause a striking motion, and the drive shaft 10 is rotated to promote excavation. Is hit with a part of the down-the-hole hammer 6 to press-fit the steel pipe (casing pipe) 1 into the hole.

As a result, when the impact press-fitting is completed, the lower end of the steel pipe (casing pipe) 1 in the axial direction is grounded to form a pile.

1 ... Steel pipe (casing pipe) 2 ... Protruding ring 6 ... Down the hole hammer 7 ... Device 8 ... Bit head 8a ... Chip 9 ... Protruding part 9a ... Stepped part 10 ... Drive shaft 11 ... Ring-shaped tip hardware 11a ... Thin part 11b ... Meat Thick part 11c ... Tapered surface part 12 ... Welding 13 ... Sheer key 14 ... Hit surface 15 ... Guide surface 16 ... Hammer fitting 17 ... Hardening process by quenching 18 ... Slot welding

Claims (3)

It is used in the middle digging pile method in which the down-the-hole hammer is set in the steel pipe in a middle digging method and is dug, and it is a ring-shaped tip hardware attached to the tip of the steel pipe, and the upper end of the part that fits into the steel pipe and enters the steel pipe is In order to block the inside of the steel pipe by filling it with concrete as the down-the-hole hammer hitting part, a plurality of shear keys, which are substantially ring-shaped metal fittings protruding in the direction perpendicular to the axis, are provided at vertical intervals and described above. The down-the-hole hammer hitting part is formed in one of the sheer keys, and is a ring-shaped tip hardware characterized in that it protrudes in the direction perpendicular to the axis of the other sheer keys. It is used in the middle digging pile method in which a down-the-hole hammer is set in a steel pipe in a middle digging method and is dug, and it is a ring-shaped tip hardware attached to the tip of the steel pipe, and the upper end of the part that fits into the steel pipe and enters the steel pipe is In order to block the inside of the steel pipe by filling it with concrete as the down-the-hole hammer hitting part, a plurality of shear keys, which are substantially ring-shaped hardware protruding in the direction perpendicular to the axis, are provided at intervals above and below, and the above. The hit portion of the down-the-hole hammer is formed in one of the shear keys, and on the lower end side, a guide surface parallel to the axial direction that surrounds the side surface of the down-the-hole hammer and has a clearance that allows the movement of the down-the-hole hammer is hardened. A ring-shaped tip hardware characterized by being hardened by quenching. The ring-shaped tip metal fitting according to claim 1 or 2, wherein the back portion near the shear key installation position is slot welded to the steel pipe and integrated with the steel pipe.

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