JP6800087B2 - Steel pipe fitting - Google Patents

Description

According to the present invention, a box joint provided at one end of an upper steel pipe and a lower steel pipe, a pin joint provided at the other end and fitable to the box joint, and an outer peripheral edge of the box joint. The box is arranged in a key arrangement portion composed of a box-side notch formed and a pin-side notch formed at a position corresponding to the box-side notch in the outer peripheral edge of the pin joint. Insertion is inserted into a rotation suppression key that prevents the joint and the pin joint from rotating relative to each other around the pipe axis, and through holes formed in the key arrangement portion and the rotation suppression key so that they can communicate with each other in the pipe radial direction. A bolt having an impossible head and a shaft portion that can be inserted into the through hole, and a dropout prevention mechanism that is attached to the tip of the shaft portion that has passed through the through hole in a state that cannot be inserted into the through hole. The bolt relates to a steel pipe joint through which the shaft portion is inserted through the through hole from the inside to the outside in the pipe radial direction.

Steel pipe piles and steel pipe sheet piles are press-fitted into the ground by hitting with a hydraulic hammer, etc., a vibration method that press-fits into the ground while applying vibration with a vibro hammer, etc. However, it is built in the ground by the Nakabori method of press-fitting into the ground, the Nakabori striking method that combines the striking method and the Nakadori method, and the rotary press-fitting method of press-fitting into the ground while rotating the blade attached to the tip. At that time, a plurality of steel pipes are built while being sequentially connected using steel pipe joints.

As steel pipe joints used for such steel pipe piles and steel pipe sheet piles, Patent Document 1 states that a box joint provided at the lower end of the upper steel pipe and a box joint provided at the upper end of the lower steel pipe can be fitted to the box joint. Pin joint, a box-side notch formed on the outer peripheral edge of the box joint, and a pin-side notch formed at a position corresponding to the box-side notch on the outer peripheral edge of the pin joint. A rotation suppression key, which is arranged in a key arrangement portion to prevent the box joint and the pin joint from rotating relative to each other around the pipe axis, and a pipe diameter in each of the key arrangement portion and the rotation suppression key. A bolt having a head that cannot be inserted into the through hole formed so as to be able to communicate in the direction and a shaft portion that can be inserted into the through hole, and a tip portion of the shaft portion that has passed through the through hole, are formed in the through hole. A steel pipe joint is disclosed in which the bolt is provided with a fall-out prevention mechanism that is attached in a non-insertable state, and the shaft portion is inserted into the through hole from the inside to the outside in the pipe radial direction. There is.

In the steel pipe joint, in addition to forming a counterbore that can accommodate a nut around the through hole on the outer surface side of the rotation suppression key, a bolt is also formed around the through hole on the back surface of the key arrangement portion. A counterbore that can accommodate the head is formed.

JP-A-2017-036574

Conventionally, a hexagon socket head cap screw having a nominal diameter of M8 has been used as a bolt for attaching the rotation restraint key. The bolt has a head having a head height of 10 mm and a head diameter of 10 mm. In the steel pipe joint disclosed in Patent Document 1, it is necessary to form a counterbore having a size capable of accommodating the entire head of the bolt around the through hole on the back surface of the key arrangement portion, which requires a lot of labor. It increased and was a factor of cost increase.

On the other hand, it is also conceivable that a counterbore that can accommodate the head of the bolt is not formed around the through hole on the back surface of the key arrangement portion. However, in this case, the head of the bolt protrudes greatly in the pipe radial direction from the back surface of the key arrangement portion in the pipe of the steel pipe pile or the steel pipe sheet pile.

Therefore, for example, when a steel pipe pile or a steel pipe sheet pile is built underground by the striking method, the head of the bolt protruding in the pipe radial direction from the back surface of the key arrangement portion in the pipe of the steel pipe pile receives resistance from the soil. , There was a risk that smooth building would be hindered.

In addition, when using a spiral auger as in the Nakabori method to build a steel pipe pile or steel pipe sheet pile composed of steel pipes with an outer diameter of 800 mm in the ground, a clearance of 2 mm is provided between the inner diameter of the pile and the spiral auger. is required. However, if the head of the bolt protrudes greatly, the clearance becomes narrow, so the workability is not good.

The present invention has been made in view of the above-mentioned problems, and provides a steel pipe joint that enables smooth construction of steel pipe piles and steel pipe sheet piles at low cost.

The characteristic configuration of the steel pipe joint according to the present invention for achieving the above object is a box joint provided at one end of an upper steel pipe and a lower steel pipe, and a box joint provided at the other end. A pin joint that can be fitted to the box joint, a box-side notch formed on the outer peripheral edge of the box joint, and a pin-side notch formed at a position corresponding to the box-side notch on the outer peripheral edge of the pin joint. A rotation suppression key, which is arranged in a key arrangement portion composed of the above and prevents the box joint and the pin joint from rotating relative to each other around the pipe axis, and the key arrangement portion and the rotation suppression key. A head having a head that cannot be inserted into a through hole formed so as to be able to communicate with each other in the pipe radial direction, a bolt having a shaft portion that can be inserted into the through hole, and a tip portion of the shaft portion that has passed through the through hole. A steel pipe joint comprising a drop-out prevention mechanism that is attached to the through hole in a state where it cannot be inserted, and the shaft portion of the bolt is inserted into the through hole from the inside to the outside in the pipe radial direction. The bolt has a head height of 2 mm or more and 6 mm or less.

By setting the head height of the bolt to 2 mm or more and 6 mm or less, the head of the bolt is a steel pipe pile even if a counterbore for accommodating the head of the bolt is not formed around the through hole on the back surface of the key arrangement portion. In the pipe of steel pipe sheet pile or steel pipe sheet pile, it protrudes only slightly in the pipe radial direction from the back surface of the key arrangement part. Therefore, for example, when building a steel pipe pile or steel pipe sheet pile in the ground by the striking method, in the pipe of the steel pipe pile. The resistance that the head of the bolt protruding from the back surface of the key arrangement portion in the pipe radial direction receives from the soil is reduced. It is economically superior because it eliminates the need for processing to form counterbore. Further, for example, when a steel pipe pile or a steel pipe sheet pile is built underground by the Nakabori method, a larger clearance than before can be provided between the head of the bolt and the spiral auger, so that the workability of the building can be improved. Can be improved.

In the present invention, it is preferable that the bolt has a head height of 2 mm or more and 3 mm or less.

According to the above configuration, for example, when a steel pipe pile or a steel pipe sheet pile is built underground by the Nakabori method, a larger clearance than before can be provided between the head of the bolt and the spiral auger. The workability of building can be further improved.

In the present invention, it is preferable that the bolt has a nominal length of 35 mm or more and 45 mm or less.

The inventors have found that the bolt preferably has a nominal length of 35 mm or more and 45 mm or less when the head height is 2 mm or more and 6 mm or less.

In the present invention, the bolt is preferably a low head hexagon socket head cap screw having a nominal diameter of M8.

The inventors have found that a low-head hexagon socket head cap screw having a nominal diameter of M8 is preferable when the head height is 2 mm or more and 6 mm or less.

In the present invention, it is preferable that the bolt has a yield point of 705 N / mm ² or more.

According to the above configuration, the head of the bolt protrudes slightly in the pipe radial direction from the back surface of the key arrangement portion in the pipe of the steel pipe pile or the steel pipe sheet pile, but the steel pipe pile or the steel pipe sheet pile is placed in the ground. It is possible to reduce the risk of damage to the bolt due to the load acting on the head of the bolt during construction.

Schematic diagram of a steel pipe pile with a steel pipe joint Explanatory drawing of steel pipe joint Explanatory drawing of the main part of the steel pipe joint Explanatory drawing of the main part of the steel pipe joint

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals.

FIG. 1 shows a steel pipe pile 1 in which two steel pipes 10 are vertically connected in the pipe axial direction of the steel pipe 10 by a steel pipe joint 2 according to the present invention. The steel pipe 10 located on the upper side is referred to as the upper steel pipe 10A, and the steel pipe 10 located on the relatively lower side is referred to as the lower steel pipe 10B, but they have the same configuration. In the present embodiment, the steel pipe 10 has an outer diameter of 800 mm. The steel pipe 10 preferably has an outer diameter of 400 mm or more and 1600 mm or less. Specifically, the outer diameters are 400 mm, 406.4 mm, 500 mm, 508.0 mm, 600 mm, 609.6 mm, 700 mm, 711.2 mm, 800 mm, 812.8 mm, 900 mm, 1000 mm, 1100 mm, 1200 mm, 1300 mm, 1400 mm, An example is a steel pipe having a diameter of 1500 mm and 1600 mm.

As shown in FIGS. 1 and 2, a female box joint 30 is welded and attached to the lower end of the upper steel pipe 10A at the welded portion 13, and can be fitted to the box joint 30 at the upper end of the lower steel pipe 10B. The male pin joint 20 is welded and attached at the welded portion 12.

The pin joint 20 is a tubular member in which a fitting portion 22A having a diameter smaller than that of the tubular portion 22B is extended continuously to a tubular portion 22B having a diameter substantially the same as the outer diameter of the lower steel pipe 10B. On the outer periphery of the base end portion of the fitting portion 22A, an engaging recess 23 into which the engaging convex portion 33 provided over the entire circumference of the lower end portion of the box joint 30 is inserted is provided over the entire circumference. At the upper end of the fitting portion 22A, an engaging convex portion 24 for inserting into the engaging concave portion 34 provided on the inner circumference of the base end portion of the box joint 30 over the entire circumference is provided. Further, a key groove 21 for fitting the load transmission key 31 arranged in the box joint 30 is provided on the outer circumference of the fitting portion 22A of the pin joint 20 over the entire circumference. The thickness of the load transmission key 31 is set to be larger than the depth of the key groove 21.

The box joint 30 is a tubular member having an outer diameter substantially the same as the outer diameter of the upper steel pipe 10A. The inner circumference of the box joint 30 is a non-fitting portion of the fitting portion 22A of the pin joint 20, and the engaging protrusion of the pin joint 20 is provided in the engaging recess 34 provided on the inner circumference of the base end portion of the box joint 30. The part 24 is inserted. Further, the engaging convex portion 33 is inserted into the engaging concave portion 23 of the pin joint 20. A key groove 35 is formed in the circumferential direction on the inner circumference of the box joint 30. The key groove 35 is provided with an arc-shaped load transmission key 31 that is appropriately divided over the entire circumference.

A plurality of bolt holes 32 communicating with the key groove 35 are perforated on the outer periphery of the box joint 30 at intervals along the circumferential direction. A set bolt 36 composed of a hexagon socket head cap screw or the like is screwed into the bolt hole 32, and the set bolt 36 can be screwed in the pipe diameter direction by a tightening operation from the outside of the box joint 30. Is.

After inserting the pin joint 20 of the lower steel pipe 10B into the box joint 30 of the upper steel pipe 10A, the load transmission key 31 arranged at the tip of the set bolt 36 is keyed by tightening the set bolt 36. It protrudes from 35 in the pipe radial direction and is fitted into the key groove 21 provided in the fitting portion 22A of the pin joint 20. As a result, the load transmission key 31 is arranged so as to straddle both the key groove 35 and the key groove 21, and the pin joint 20 and the box joint 30 cannot be relatively moved in the direction along the pipe axial direction of the steel pipe pile 1. Is connected to.

The load transmission key 31 is not limited to one stage, and may be a plurality of stages of two or more stages, and the number and number of stages, as well as the thickness and width thereof, are required for connecting the upper steel pipe 10A and the lower steel pipe 10B. It is appropriately designed according to the strength of the vertical bond.

The relative rotation of the upper steel pipe 10A and the lower steel pipe 10B around the pipe axis is suppressed by the rotation suppression key 50 arranged so as to straddle the joint 14 on the outer peripheral surface of the pin joint 20 and the box joint 30. The rotation suppression keys 50 are arranged at a plurality of key arrangement portions 40 provided at a plurality of locations at equal intervals along the circumferential direction of the seam 14. The size, number, arrangement location, etc. of the rotation suppression key 50 and the key arrangement portion 40 can be appropriately determined by design based on the diameter of the steel pipe pile 1, the building method, and the like.

As shown in FIGS. 1 to 4, the rotation suppression key 50 is a flat plate-shaped member having a rectangular shape when viewed from the front, and when it is arranged in the key arrangement portion 40, the pin joint 20 and the box joint 30 rotate relative to each other. It is used to prevent. In the present embodiment, the thickness of the rotation suppression key 50 is 13 mm.

The rotation restraint key 50 has a through hole 52 provided on the pin joint 20 side for inserting a bolt 15 for fixing the rotation restraint key 50 to the key arrangement portion 40 in the pipe radial direction of the steel pipe pile 1. It is pierced along. The through hole 52 is formed to have a diameter slightly larger than the diameter of the bolt 15. On the outer surface of the rotation restraint key 50, a counterbore 53 capable of accommodating nuts 60 and 61 screwed with the bolt 15 is formed around the through hole 52. The through hole 52 and the counterbore 53 are provided at positions closer to the pin joint 20 side than the vertical center of the rotation restraint key 50 so that the bolt 15 provided on the pin joint 20 side can be inserted.

As shown in FIGS. 3 and 4, of the nuts 60 and 61, the nut 60 has a convex tapered portion 62 having a tapered shape eccentric with respect to the pipe axis of the bolt 15 in the pipe axis direction of the bolt 15. I have. On the other hand, the nut 61 is provided with a tapered concave tapered portion 63 that faces the convex tapered portion 62 and is concentric with the pipe axis of the bolt 15. Therefore, when the rotation suppression key 50 is arranged in the key arrangement portion 40, when both nuts are tightened so that the convex taper portion 62 and the concave taper portion 63 are in contact with each other, between the facing surfaces of the nuts 60 and 61. Depending on the distance, a force is generated on the nuts 60 and 61 in the direction of the pipe diameter of the bolt 15. The nuts 60 and 61 screwed into the bolt 15 by this force are fixed to the bolt 15 without loosening due to vibration or the like during construction. The nuts 60 and 61 prevent the rotation restraint key 50 from falling off from the key arrangement 40. Therefore, the nuts 60 and 61 constitute the fall-off prevention mechanism provided at the tip of the bolt 15 that has passed through the through holes 25 and 52 of the present invention. The tightening torque of the nuts 60 and 61 with respect to the bolt 15 is preferably 19.7 to 27.7 Nm (axial force 12.3 to 17.3 kN). Within this range, the nuts 60 and 61 can be tightened without damaging the bolt 15. A washer is appropriately provided between the head portion 16 of the bolt 15 and the inner peripheral surface of the pin joint, and between the nut 60 and the counterbore 53.

The key arrangement portion 40 is formed on the outer peripheral edge of the upper joint surface 37 forming the seam 14 on the outer periphery of the engaging convex portion 33 formed on the box joint 30 and on the box side notch 40A and the pin joint 20. Corresponds to the box side notch 40A when the outer peripheral edge of the lower joint surface 27 forming the seam 14 and the pin joint 20 are inserted into the box joint 30 on the outer side of the engaging recess 23. It is composed of a pin-side notch 40B at a position to be used.

The circumferential length of the box-side notch 40A and the circumferential length of the pin-side notch 40B are matched with each other, and the vertical length of the box-side notch 40A and the vertical length of the pin-side notch 40B. The inner dimensions of the key arrangement portion 40 are slightly larger than the outer dimensions of the rotation restraint key 50 arranged inside.

As shown in FIG. 3, a through hole 25 for inserting a bolt 15 for fixing the rotation suppression key 50 to the key arrangement portion 40 is provided in the pin-side notch 40B along the pipe radial direction of the steel pipe pile 1. It is pierced. The through hole 25 is provided with a female screw portion 26 that is screwed with the bolt 15.

The bolt 15 is inserted through the through hole 25 from the inside to the outside of the pin joint 20. At that time, since the bolt 15 is screwed into the female threaded portion 26 in the through hole 25, it can be inserted into the through hole 25 in advance in the state before the upper steel pipe 10A and the lower steel pipe 10B are connected. Subsequent workability is improved. However, the through hole 25 may not be provided with the female screw portion 26.

In the present embodiment, the bolt 15 is a low head hexagon socket head cap screw made of chrome molybdenum steel (SCM435) and having a nominal diameter of M8, a head height of 2 mm, a nominal length of 35 mm, and a shaft portion 17. The pitch of the screws formed in the above is 1.25 mm, and the yield point is 705 N / mm ² or more.

In the present embodiment, since the head height of the bolt 15 is set to 2 mm, it is not necessary to form a counterbore for accommodating the head 16 of the bolt 15 around the through hole 25 on the back surface of the key arrangement portion 40. Since the head portion 16 of the bolt 15 only slightly protrudes from the back surface of the key arrangement portion 40 in the pipe of the steel pipe pile 1 in the pipe radial direction, for example, when the steel pipe pile 1 is built in the ground by the striking method. In the pipe of the steel pipe pile 1, the resistance received from the soil by the head 16 of the bolt 15 protruding in the pipe radial direction from the back surface of the key arrangement portion 40 is reduced.

In other words, when the steel pipe pile 1 is built underground, the head 16 of the bolt 15 slightly protrudes from the back surface of the key arrangement portion 40 in the pipe radial direction in the pipe of the steel pipe pile 1. The load acting on the head 16 of the bolt 15 can reduce the risk of the bolt 15 being damaged.

Further, it is economically excellent by eliminating the need for processing to form a counterbore for accommodating the head portion 16 of the bolt 15. Further, for example, when the steel pipe pile 1 is built underground by the Nakabori method, a larger clearance than before can be provided between the head 16 of the bolt 15 and the spiral auger, so that workability is improved. ..

Regarding the force applied to the head of each bolt when it is used to attach the rotation restraint key 50 of the steel pipe pile 1 having the inner diameter of the pin joint 20 of 720 mm for three types of bolts having different head heights of 2 mm, 6 mm and 10 mm. The analysis was performed. Each bolt has a head diameter of 10 mm. Further, the nominal diameter is M8, the pull-out force is 2200 kN, and therefore the shear strength of the shaft portion is 20460 N.

The bearing area applied to the head of a bolt having a head height of 2 mm is 20 mm ² . The force applied to the head of the bolt is 6111N, assuming that a pulling force is applied to a width of 10 mm in the pin joint 20 having an inner diameter of 720 mm. Since this value is smaller than the shear strength of 20460N of the shaft portion of the bolt and smaller than the shear strength of 20460N of the head portion, there is no risk of the bolt being damaged.

The bearing area applied to the head of a bolt having a head height of 6 mm is 60 mm ² . The force applied to the head of the bolt is 20460 N, assuming that a pulling force is applied to a width of 10 mm in the pin joint 20 having an inner diameter of 720 mm. Since this value is the same as the shear strength of 20460N of the shaft portion of the bolt and smaller than the shear strength of 61379N of the head portion, there is no risk of the bolt being damaged. In this specification, there is a tolerance in the dimensions of the head of the bolt, and the decimal point is not shown. The bolt head height calculated from the value of the shear strength of the actual bolt shaft is allowed up to about 6.69 mm. If the head height of the bolt is less than this, there is no risk of the bolt being damaged, but for safety, the upper limit of the head height of the bolt is set to 6 mm.

The bearing area applied to the head of a bolt having a head height of 10 mm is 100 mm ² . The force applied to the head of the bolt is 30556 N, assuming that a pulling force is applied to a width of 10 mm in the pin joint 20 having an inner diameter of 720 mm. This value is smaller than the shear strength of the head of the bolt, 102298N, but exceeds the shear strength of the shaft of the bolt, 20460N. As described above, a bolt having a head height of 10 mm may be damaged.

From the above, the head height of the bolt 15 was set to 2 mm or more and 6 mm or less. The head height of the bolt 15 is such that, for example, when a steel pipe pile or a steel pipe sheet pile is built underground by the Nakabori method, a larger clearance than before is provided between the head 16 of the bolt 15 and the spiral auger. From the viewpoint, it is particularly preferable that it is 2 mm or more and 3 mm or less. Further, the bolt 15 preferably has a nominal length of 35 mm or more and 45 mm or less. It should be noted that each dimension is a design value and actually has a tolerance.

As described above, by disposing the rotation restraint key 50 in the key arrangement portion 40 formed at the joint 14 between the pin joint 20 and the box joint 30, the pin joint 20 and the box joint 30 are formed, that is, the upper steel pipe 10A. And the lower steel pipes 10B are prevented from rotating relative to each other.

In the present embodiment, the bolt 15 is provided in the pin joint 20 by being inserted through the through hole 25 from the inside to the outside of the steel pipe pile 1, and the nuts 60 and 61 are provided on the rotation restraint key 50 side. Therefore, when the steel pipe pile is built, the nuts 60 and 61 can be operated from the outside of the steel pipe pile 1 after the rotation suppression key 50 is arranged, so that the workability is good.

In the above-described embodiment, the configuration in which the nuts 60 and 61 constituting the dropout prevention mechanism include the convex tapered portion 62 and the concave tapered portion 63 has been described, but the present invention is not limited to this. The dropout prevention member may be composed of two hexagon nuts that do not have a convex tapered portion 62 or a concave tapered portion 63. In this case, when both nuts are tightened so that the two hexagon nuts are in contact with each other, a tensile force is generated between the two hexagon nuts in the direction along the pipe axis direction of the bolt 15. Due to this tensile force, both hexagon nuts are fixed to the bolt 15 without loosening due to vibration or the like during construction. Since the head portion 16 of the bolt 15 and the hexagon nut continue to abut around the through holes 25 and 52, the rotation restraint key 50 is prevented from falling off from the key arrangement portion 40. Further, the fall-off prevention mechanism may be a single hexagon nut, and at that time, it is preferable to provide a washer for preventing the hexagon nut from loosening.

The steel pipe joint 2 according to the present invention is not limited to the steel pipe pile 1 as described above, and can be connected to the steel pipe 10 and the joint provided on the outer peripheral surface of the steel pipe joint 2 along the longitudinal direction in the same manner on the adjacent steel pipe sheet piles. It can also be used for steel pipe sheet piles provided with joints.

The above-described embodiments are all examples of the present invention, and the description does not limit the present invention, and the specific configuration of each part can be appropriately modified and designed within the range in which the effects of the present invention are exhibited. is there.

10: Steel pipe 10A: Upper steel pipe 10B: Lower steel pipe 15: Bolt 16: Head 17: Shaft 20: Pin joint 25: Through hole 26: Female screw part 30: Box joint 40: Key arrangement part 40A: Box side Notch 40B: Pin side notch 50: Rotation suppression key 52: Through hole 60: Nut (fall-off prevention mechanism)
61: Nut (fall prevention mechanism)

Claims (5)

A box joint provided at one end of the upper steel pipe and the lower steel pipe, a pin joint provided at the other end and fitted to the box joint, and a box formed on the outer peripheral edge of the box joint. The box joint and the pin are arranged in a key arrangement portion composed of a side notch and a pin side notch formed at a position corresponding to the box side notch in the outer peripheral edge of the pin joint. A rotation suppression key that prevents the joint from rotating relative to the pipe axis, and a head that cannot be inserted into a through hole formed in each of the key arrangement portion and the rotation suppression key so as to communicate in the pipe radial direction. A bolt having a portion and a shaft portion that can be inserted into the through hole, and a dropout prevention mechanism that is attached to the tip end portion of the shaft portion that has passed through the through hole in a state that cannot be inserted into the through hole. The bolt is a steel pipe joint in which the shaft portion is inserted through the through hole from the inside to the outside in the pipe radial direction.
The bolt is a steel pipe joint having a head height of 2 mm or more and 6 mm or less. The steel pipe joint according to claim 1, wherein the bolt has a head height of 2 mm or more and 3 mm or less. The steel pipe joint according to claim 1 or 2, wherein the bolt has a nominal length of 35 mm or more and 45 mm or less. The steel pipe joint according to any one of claims 1 to 3, wherein the bolt has a nominal diameter of M8. The steel pipe joint according to any one of claims 1 to 4, wherein the bolt has a yield point of 705 N / mm ² or more.

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