JP2882286B2 - Screw joint structure, steel pipe pile and steel sheet pile - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threaded joint structure applicable to a threaded joint capable of supporting a lateral force received from the ground, such as foundation piles, landslide prevention or earth retaining, and the like. It relates to a steel pipe pile and a steel pipe sheet pile.

[0002]

2. Description of the Related Art Steel pipe piles are often used as foundation piles for strengthening the ground on which a building foundation is installed.
Because it is easier to construct than concrete, it has come to be used as a steel pipe sheet pile for landslide prevention or earth retaining with a joint. In these applications, there is a tendency to resist greater bending than conventional foundation piles. In addition, steel pipe piles in urban areas tend to be small-diameter and thick-walled due to restrictions on the pile construction space.

[0003] Hereinafter, a description will be mainly given of a steel pipe pile for landslide prevention, but the present invention is not limited to a landslide prevention steel pipe and is intended for a steel pipe pile for supporting a lateral force from the ground described above. It is also applied to retaining steel pipe piles, foundation piles and steel pipe sheet piles.

For example, in the case of a steel pipe pile for preventing landslides,
It is mainly installed in landslide areas where landslides are likely to occur.
Therefore, the construction site is often a steep slope such as a mountain area, and it is difficult to carry heavy equipment such as a pile driver. Also,
Other special machines are also difficult to use and are uneconomical if used. For this reason, it is generally impossible to drive a pile by hitting, and the ground is drilled in advance (pre-boring), and the pile is built in the hole.

[0005] In addition to the above, such a landslide-preventing steel pipe pile is characterized in that it has a large outer thickness (small diameter thick pile) compared to a general steel pipe pile. In addition, in order to withstand the earth pressure at the time of landslide, the joint part is required to have the same strength (particularly bending strength) as the pile body.

[0006] The total length of the landslide-preventing steel pipe piles varies depending on the geological conditions of the site, but generally reaches 20 to 30 m in many cases. Usually, there are restrictions on transportation, etc., so a plurality of piles are connected at the site (joint piles) while constructing. Since the joint pile operation is performed in an unstable operation environment, it needs to be performed quickly, and at the same time, a reliable operation is required.

[0007] This joint pile operation has been carried out by welding on site, but has various drawbacks. First, it takes a lot of time to work on piles, for example,
Even for welding a steel pipe pile of about 300mm x 30mm in thickness, it takes 2-3 hours for joint pile work. Next, since the weather tends to change in the mountainous area at the site, the quality of the welded portion is greatly affected by the weather, and the strength and the like of the welded portion vary widely. In addition, the work environment at the site is poor, and it is difficult to secure excellent welding technicians.

In the case of steel pipe sheet piles used in urban areas, it is often necessary to construct the piles within a limited space and time, and the distance between the structure to be constructed and the boundary of the adjacent land is often short. For these reasons, it is required that the construction of steel pipe sheet piles be performed in a short period of time, and there is a tendency to use small-diameter and thick steel sheet piles.

[0009] In most cases, steel pipe sheet piles are installed in a city area by a middle excavation method or a first excavation method to prevent noise and vibration. These construction methods have a problem that the construction speed is slower than the impact construction method, and since the joining of steel pipe sheet piles was conventionally limited to welding joining, it occupies about 30 to 50% of the construction time, and construction in rainy weather is difficult. One of the issues is to shorten the time for a certain welding connection. As a solution to this, there is also a method of welding by placing a steel pipe sheet pile aside before embedding it.However, in this case, there is a limit to the length that can be built in construction, and there is a problem that a separate welding yard must be provided. Is not a drastic solution. The dimensions of steel sheet piles used in urban areas usually have an outer diameter of 500 mm or more.
The thickness is about 1000 mm and the thickness is 9 to 14 mm. But,
Due to the problem of the boundary with the adjacent land, there is a tendency that the outer diameter is further reduced and the plate thickness is increased.

Further, in the case of a steel pipe pile used for reinforcing the foundation of an existing structure or a steel pipe pile constructed in a place where the height of the construction space is limited, such as under an underground bridge, the pile is mainly used for construction reasons. Is a small-diameter wall, and each pile that constitutes one set of piles is short. Therefore, reducing the time for joining piles is an important issue. In addition, when the work is performed in a closed place, the working environment deteriorates when welding is performed. Further, when the use of firearms is not permitted, such as in a chemical factory, welding cannot be performed.

In view of the above, instead of the joint work by welding, a technique using a threaded joint for the joint pile has been studied, and several techniques have been disclosed.

FIG. 12 is a sectional view showing a section of a joint of a steel pipe pile described in this publication. In the drawing, 1 indicates a steel pipe pile, 19 indicates a fitting (nipple), 2 indicates a female screw joint, and 3 indicates a male screw joint. Female threaded joints 2, 2 and male threaded joints 3, 3
Are oppositely threaded in the upper half and the lower half in the figure, respectively. The joint pile operation is performed by screwing the joint hardware 19 into the female screw joints 2 and 2 of the upper and lower steel pipe piles 1 and 1 using a machine (not shown).

FIG. 13 is a cross-sectional view showing a cross section of a joint of a steel pipe pile described in this publication. In the drawing, reference numeral 20 denotes a fitting (socket), and other reference numerals are the same as those in FIG. Screw joint part 2,
2 are mutually reverse-threaded. The joint pile operation is performed by connecting the joint hardware 20 to the male screw joint portion 3 of the steel pipe pile 1 above,
It is carried out by screwing into a male screw joint of a steel pipe pile (not shown).

FIG. 14 is a front view showing the appearance of a steel pipe pile joined by a joint according to this technique. In the drawing, reference numeral 9 denotes a joint portion, and other reference numerals are the same as those in FIGS.

FIG. 15 is a front view showing an appearance and a cross section of a joint of a steel pipe pile described in this gazette. The reference numerals in the drawings are the same as those in FIGS. This technology uses a screw joint type steel pipe pile for a foundation pile such as a building. The female screw joint 2 enlarges the pipe end of the steel pipe pile 1 in the upper part of the figure (expanding).
The male screw joint part 3 is machined as it is on the pipe end of the steel pipe pile 1 below in the figure. The joint pile operation is performed by rotating the upper steel pipe pile 1 by a machine (not shown) and screwing it.

FIG. 16 is a front view showing an appearance and a cross section of a joint of a steel pipe pile described in this publication. FIG. 17 is an enlarged cross-sectional view showing a cross section of the joint portion in an enlarged manner. In these figures,
Reference numeral 21 denotes a flange, and other reference numerals are the same as those in FIGS. Female threaded joints 2, 2 and male threaded joints 3, 3
As in the prior art, the upper half and the lower half in the figure are mutually reverse-threaded. The joint pile operation is performed by screwing the joint hardware 19 into the female screw joints 2 and 2 of the upper and lower steel pipe piles 1 and 1 using a machine (not shown).

[0017]

However, these prior arts have the following problems when used in landslide prevention piles, steel pipe piles, and steel pipe sheet piles.

In the prior art, since the outer diameter of the fitting (nipple) is considerably smaller than that of the steel pipe main body, it is difficult to make the section modulus equal to that of the steel pipe main body. In the case of the landslide prevention pile, since the pipe thickness of the steel pipe is usually about 10% of the outer diameter, the outer diameter of the fitting is about 80% of the outer diameter of the steel pipe body. For pipes, the section modulus is 3
Since it is proportional to the power, the section modulus of the fitting is reduced to about 51% of the steel pipe body. In this case, it is not impossible to make the section modulus of the joint fitting equal to that of the steel pipe body by increasing the pipe thickness of the joint fitting by several times, but it is calculated that it is 25% of the outer diameter of the steel pipe body. About thickness is required,
Poor practicality in terms of weight and the like.

Further, it is necessary to rotate the joint hardware by the number of threads from the engagement of the screws to the completion of the screwing. In landslide prevention piles, steel pipe piles, and steel pipe piles for steel pipe sheet piles, the number of screw threads is about 15 to 30. Therefore, it is difficult to rotate the pile many times manually while controlling the suspension load. In the end, a special machine is required for screwing, and it cannot be used for landslide prevention steel pipe piles or steel sheet piles to be installed in narrow lands on mountain slopes or in limited lands in urban areas.

Further, since the screws of the joint fittings are reversely screwed up and down, it is necessary to screw them into the upper and lower steel pipe piles at the same time. If it shifts, even if the steel pipe pile on which screwing started earlier reaches the center of the fitting, the other will not reach and there will be a gap. In order to eliminate this gap and tighten, it is necessary to rotate one of the piles, but this causes a problem that the screw between the pile and the fitting is loosened.

In the prior art, the outer diameter is larger than the outer diameter of the steel pipe pile because the fitting is a socket type. Therefore, it is necessary to make the inside diameter of the hole drilled in the ground larger than the outside diameter of the steel pipe pile, and the construction cost increases. As a result, the overall construction cost is generally higher than the above-mentioned joint pile work by welding, which is not practical. Further, in the case of a steel pipe sheet pile, it is difficult to attach a sheet pile joint member to the joint.

The section modulus of the fitting can be easily made equal to that of the steel pipe main body. However, the male threaded joint of the steel pipe pile is reduced in wall thickness by threading, so that not only the section modulus is lower than that of the main body, but also. Both tensile strength and shear strength decrease.

Further, since the screws of the joint fittings are reversely screwed up and down, it is difficult to match the screwing of the upper and lower steel pipe piles as in the prior art.

In the prior art, the outer diameter of the joint is larger than the outer diameter of the steel pipe main body, as in the prior art. As a result, it is necessary to make the inner diameter of the hole drilled in the ground larger than the outer diameter of the steel pipe main body, so that the construction cost increases.
Further, a sheet pile joint cannot be attached and used as a steel pipe sheet pile.

Further, since the female threaded joint at the end of the steel pipe pile is threaded after the steel pipe pile is used as it is or after the diameter thereof is increased, it is inevitable that the wall thickness is reduced at the root of the screw. for that reason,
The female threaded joint of the steel pipe pile not only has a lower section modulus than the pile body, but also has a lower tensile strength and shear strength.

In the prior art, it is described that the bending strength can be increased by strongly tightening, but the tightening force does not theoretically contribute to an increase in bending strength. In addition, this technology uses a joint of the same type as the conventional technology, and therefore has the same problem that the bending strength of the joint hardware is low, the number of rotations required for screwing in is large, and tightening is difficult due to the reverse screw. is there.

Further, there are some problems common to these prior arts. First, in any of the techniques, torque management is required in the screwing operation. A special machine is required for torque control, and it is not suitable as a joint for steel pipe piles, steel sheet piles, and landslide prevention steel pipe piles to be constructed at narrow sites on mountain slopes.

A bending force acts on the steel pipe pile and the steel sheet pile, which acts on the joint as a compressive force on the inside of the bend and a tensile force on the outside of the bend. At that time, the thread of the screw joint used in the prior art,
A radial component is generated. In the prior art, a large component force is generated because the angle formed by the slope of the thread with respect to the direction of the central axis is not so large (usually 60 degrees). As a result, there is a problem in that the male screw is deformed inward and the female screw is deformed outward, so-called thread relief is increased, the joint pipe is deformed into an elliptical shape, and finally the screw connection state cannot be maintained.

FIGS. 18 to 20 are cross-sectional views showing a cross section of a threaded joint according to the prior art. The thread cross section of the threaded joint shown in FIG. 18 has a normal triangular shape, FIG. 19 shows a trapezoidal shape, and FIG. 20 shows a rectangular shaped screw. Among them, in a threaded joint having a thread having a triangular and trapezoidal cross section, the slope of the thread has an angle of about 60 degrees with respect to the tension / compression direction of the joint. Although the screw having the rectangular cross section in FIG. 20 does not have the above-described problem, the frictional force at the time of screwing is large, and the screwing work becomes difficult.

The present invention solves these problems of the prior art. Therefore, the joint pile operation is facilitated even in an unfavorable construction environment such as an incline or an urban area, and the joint portion comes off due to bending deformation. A steel pipe pile and a steel pipe sheet pile provided with a difficult screw joint structure and a screw joint based thereon.

[0031]

According to the first aspect of the present invention, there is provided a threaded joint structure of a male threaded joint and a female threaded joint provided at an end of a steel pipe main body for connecting a steel pipe pile or a steel pipe sheet pile. ) The thread of this threaded joint is a tapered thread, and (b) of the two slopes of the thread of this threaded joint,
(C) the male threaded joint has a shoulder with a step smaller than the thickness of the steel pipe main body, and (d) the female threaded joint. Is a threaded joint structure characterized in that the outer diameter is equal to the outer diameter of the steel pipe main body.

According to a second aspect of the present invention, there is provided the threaded joint structure according to the first aspect, wherein the taper of the thread of the threaded joint portion is 1/3 to 1/10.

[0033] The invention of claim 3 is the invention of claim 1 or claim 2.
A steel pipe pile or a steel pipe sheet pile, characterized in that a male screw joint or a female screw joint based on the joint structure described above is provided at at least one end of a steel pipe main body.

[0034]

First, since the threaded joint is a tapered thread, it is not necessary to rotate the joint from the beginning of screwing even if the number of threads provided on the threaded joint is large. By simply moving the screw joint in the axial direction, the male screw and the female screw can be overlapped to the extent that a few threads are left. Therefore, screwing is completed by several rotations.

Next, by using a tapered thread, the strength of the joint can be ensured without making the thickness of the threaded joint portion much larger than the thickness of the steel pipe main body to which the threaded joint portion is attached.
Generally, it is known that a threaded joint only needs to have a cross-sectional performance at a root portion (on a steel pipe main body side) of the steel pipe main body or more. Therefore, reducing the thickness of the threaded joint portion toward the end portion, that is, forming a tapered thread, has no problem in strength.

The outer diameter (thread portion) of the male threaded joint portion on the steel pipe main body side is smaller than the outer diameter of the steel pipe main body by the thickness of the end of the female threaded joint portion. You don't have to. Therefore, the section modulus equivalent to that of the steel pipe main body can be obtained only by slightly increasing the thickness of the male screw joint part as compared with the steel pipe main body.

Next, when a tensile force acts on the steel pipe pile or the steel pipe sheet pile, force is applied to the slope facing the steel pipe main body, that is, the slope of the thread slope of both screw joints, that is, the slope on the steel pipe main body side. Acts to generate a radial component force. This component force is reduced by increasing the angle θ between the central axis and the slope, and becomes zero when θ is 90 degrees. In the present invention, the angle θ is set to 75 degrees or more, preferably 80 degrees or more, and more preferably 85 degrees or more.
(Around 60 degrees), the component force in the radial direction can be reduced to about 1/2 or less. As a result, the escape of the threads of the male screw and the female screw is reduced with respect to the tensile force of the same magnitude, so that it is easy to maintain the connected state of the screws, and it is difficult for the screws to come off outside the bend.

Further, since the male screw joint has a shoulder, the end of the female screw joint and the shoulder are processed so as to be in close contact with each other. Can receive part of the compressive force acting on the Therefore, it is possible to prevent the threads of the threaded joint portion from coming off inside the bend.

Further, when screwing in the joint portion, when the two screw joint portions are screwed in, the end portion (tip) of the female screw joint portion finally comes into contact with the shoulder portion, and any further force is applied. Screwing can be prevented, and breakage of the screw thread can be avoided. If the dimension of the shoulder of the shoulder part is larger than the plate thickness of the steel pipe main body, since the section modulus of the male screw joint part becomes small,
Make it smaller than the thickness of the steel pipe body.

Finally, by making the outer diameter of the female screw joint portion equal to that of the steel pipe main body to which the female screw joint portion is attached, the outer diameter of the entire steel pipe pile or the entire steel pipe sheet pile including the screw joint portion becomes the same.

Regarding the second aspect of the present invention, the reason for limiting the size of the taper of the threaded joint will be described. First, 1 / of the upper limit
Numeral 3 is a numerical limitation for securing the joint strength. If the taper size exceeds 1/3, the length of the thread portion in the central axis direction becomes short, and the number of necessary threads cannot be secured. Strength cannot be secured.

With respect to the lower limit of 1/10, if it is less than this, it will be close to a normal parallel thread, and the difference (clearance) between the outer diameter of the end of the male threaded joint and the inner diameter of the end of the female threaded joint will be small. As a result, it becomes difficult to align the screw joints of the leading pile and the trailing pile in the joint pile operation. Further, when the taper is small, the number of rotations of the steel pipe pile or the steel pipe sheet pile required for screwing increases, and the ease of screwing by the taper screw is impaired.
From the above, regarding the size of the taper of the threaded joint, 1 /
10 or more and 1/3 or less.

The third aspect of the present invention is the first or second aspect.
Since the threaded joint structure of the invention is applied to a steel pipe pile or a steel pipe sheet pile, the number of rotations of the steel pipe main body required for screwing the threaded joint portion can be reduced. Therefore, the joint pile work for connecting the steel pipe pile or the steel pipe sheet pile is facilitated. In addition, since the strength of the threaded joint is equal to or higher than that of the steel pipe main body, the same performance as that obtained when a long steel pipe pile or a steel pipe sheet pile is used can be obtained with respect to the strength against bending deformation and the like.

[0044]

FIG. 1 is a front view showing an external appearance and a cross section of an embodiment of the present invention. In the figure, 1 indicates a steel pipe main body, 1c indicates an outer surface of the steel pipe main body, 1d indicates an inner surface of the steel pipe main body, 2 indicates a female screw joint, and 3 indicates a male screw joint. FIG. 2 is a cross-sectional view showing a cross section of the threaded joint of the above embodiment. In the figure, 2
a indicates the tip of the female screw joint, 8 indicates a shoulder, and other reference numerals are the same as those in FIG.

FIG. 3 is a cross-sectional view showing a cross-sectional shape of a screw thread in a state where the screw joint portion is connected. In the drawing, R is the direction in which the threaded joint is screwed, 14 is the slope on the end side of the thread, 1
Reference numeral 6 denotes an inclined surface on the body side of the screw thread, and other reference numerals are the same as those in FIG. The screwing direction R is also a direction on the end side of the joint.

FIG. 4 is a cross-sectional view showing a thread contact state of the threaded joint portion during the joining operation of the steel pipe pile according to the present invention. In the figure, 15 is a contact portion, 17 is a gap,
Other reference numerals are the same as in FIGS. 1 and 3. Contact part 15
Since the screw is a tapered screw, even if the cross-sectional shape of the screw thread is straight, the screw stays only partially in contact with the slope, and the frictional force at the time of screwing can be reduced as compared with the parallel screw.

Further, among the slopes of the thread, the slope formed on the end side of the steel pipe pile is preferably formed at an angle of 45 to 85 °, more preferably 60 to 85 °, with the central axis. Below the lower limit, the normal reaction acting on the contact surface (slope of the screw thread) during screwing becomes large, and the frictional force acting on this contact surface becomes large accordingly, making screwing work difficult.

The upper limit of the angle formed by the slope on the end side of the steel pipe pile and the central axis is a limit for securing the gap 17 between the slopes of the thread shown in FIG. If this upper limit is exceeded, gap 1
7 becomes too small and the two slopes of the thread come into contact on both sides during the screwing process, as in the case of the rectangular screw. As a result, the frictional force increases and the screwing operation becomes difficult.

If a part of the cross section of the slope on the end side of the steel pipe pile, preferably the entire cross section of the slope on the end side is processed into a curve, the contact portion shown in FIG. 15 is basically in line contact, and the frictional force at the time of screwing can be greatly reduced.

FIG. 5 is an explanatory view showing a stress state when bending stress is applied to the steel pipe pile. In the figure, 1 indicates a steel pipe pile, 9 indicates a threaded joint, and 18 indicates a central axis. Around the central axis 18,
The stress state is tension outside the bend and compression inside.

FIG. 6 is an explanatory view showing the deformation behavior of the threaded joint part in bending deformation when there is no shoulder part in the joint part. In the figure, reference numeral 2a denotes a tip of the female screw joint. When compressed inside the bend, if there is a shoulder portion, the tip portion 2a is in close contact with the shoulder portion, so that the compression force can be reduced. However, in the case of this figure, since there is no shoulder portion, it is necessary to receive the compressive force on the slope on the thread end side of the threaded joint. Since the angle formed by the slope with the central axis is not so large, a component force in the radial direction is generated with a magnitude that cannot be ignored, and the screw will eventually come off.

FIG. 7 is a cross-sectional view showing a cross section when the two steel pipe piles are joined together. In the drawing, reference numeral 4 denotes a welded portion, 9 denotes a screw joint portion, and 10 denotes a screw joint portion, and other reference numerals are the same as those in FIG.

The pile body has an outer diameter of 318.5 mm and a thickness of 25 mm.
Was used. Two steel pipe bodies are prepared, and a tapered female screw joint is provided at the end of one steel pipe.
An external threaded joint having a tapered shape was welded to the end of another steel pipe at a factory. Material is pile body 1, 1,
Used was 65 kg-class steel, and 80 kg-class steel having a material strength higher than that of the screw joint portion.

For the threaded joint, the magnitude of the taper (the amount of change in outer diameter or inner diameter with respect to the distance in the center axis direction) is determined.
1/6, screw pitch 8.5mm, screw height 2.4 ~ 2.
Processed as 5 mm. The angle of the slope of the thread was 60 degrees on the end side and 87 degrees on the main body side with respect to the center axis.

Here, the strength of the threaded joint is made equal to or greater than the strength of the steel pipe main body by making the thickness of the male screw joint at least at a portion close to the shoulder part equal to or greater than that of the steel pipe main body. it can. In general, the force acting on the threaded joint has the same size on the steel pipe main body side as the steel pipe main body, and decreases as it approaches the end. Therefore, as long as the thickness is secured at least at the shoulder portion, there is no problem in terms of the joint strength even if the thickness is reduced as approaching the end portion.

Next, the bending strength of the threaded joint was examined. FIG. 9 is an explanatory view showing an outline of a four-point loading pure bending test for examining the bending strength of the threaded joint. In the figure, 11 indicates a fulcrum, 12 indicates a loading point, and P indicates a test load. The test conditions are as follows: the distance between the fulcrums 11, 11 is 5400 mm,
The interval between the loading points 12, 12 is 1500 mm. For the test material, a screw joint was arranged at the center of the bend, and for the comparative material, a steel pipe having the same material and dimensions as the pile body of the test material was used.

FIG. 9 is a load / displacement diagram showing the results of the bending test. In the figure, the vertical axis shows the load (tf: ton weight), the horizontal axis shows the displacement at the center (central displacement: mm), the curve A shows the results for the test material, and the curve B shows the results for the comparative material. From the figure, it can be seen that in the test material (screw joint), the load for the same displacement is equal to or slightly larger than the comparative material (pile body).

The edge yield load (86.15 tf) and the total section yield load (118.45 tf) in the figure are values theoretically estimated from the yield strength of steel. Here, the former is a load when a portion where stress in bending deformation becomes maximum (generally, an outer edge of the pile) starts to yield, and the latter is a load when the entire pile yields (bends and breaks). In the test in this figure, there is a load / displacement curve that returns to a load of 0 near the center displacement of 50 to 100 mm. This is because the load was once unloaded and loaded again during the bending test. As can be seen from the figure, it is known that after loading, the state returns to the state before unloading, and that the bending test has the same result as the case where the test is continuously performed without interruption.

Similarly, the outer diameter of the pile body is 406.4 mm × thickness
The steel pipe with the dimensions of 25mm is used, and the material is the pile body 1,
A bending test was performed using a steel of 65 kg class 1 and a steel of 80 kg class having a material strength higher than that of the screw joint part.

For the threaded joint, the size of the taper
1/4, the pitch of the screw was 8.7mm, and the height of the screw thread was 3.0mm. The angle of the slope of the thread was 80 degrees on the end side and 87 degrees on the steel pipe main body side with respect to the central axis.
The bending strength of this threaded joint was examined. The test method and test conditions are the same as those in the embodiment shown in FIG.

FIG. 10 is a load / displacement diagram showing the results of the bending test. In the figure, the vertical axis, horizontal axis, curve A and curve B are
This is the same as FIG. As shown in the figure, in the test material (screw joint part), the load for the same displacement is compared with the comparative material (pile body).
It turns out that it is equal to or slightly larger than.

As described above, according to the present invention, the bending strength of the threaded joint can be made equal to or slightly larger than the bending strength of the steel pipe pile main body. As a result, it is understood that the steel pipe pile of the present invention has substantially the same bending strength as the pile main body, that is, the bending strength, over the entire length including the threaded joint portion in the spliced state.

Regarding the dimensions of the screw, except for the special steel pipe pile having a large diameter, the pitch is 5 mm or more and 15 mm or less, and the height of the screw thread is 2 mm or more and 5 m in the normal outer diameter range (outer diameter 300 to 800).
m or less. The reason is as follows.

First, if the pitch is less than 5 mm, the screw becomes too fine, the number of rotations for screwing increases, and the efficiency of the joint pile operation decreases. Further, since the number of screw threads is increased, the frictional force at the time of screwing is increased, and it becomes difficult to manually screw the screw. If the pitch exceeds 15 mm, the number of threads decreases, and the joint strength decreases. In addition, the force borne by one thread is large, and the stress on the side surface of the thread is too high.

If the height of the thread is less than 2 mm, it is too low, and the thread is easily removed by deformation of the threaded joint due to bending load. If the height of the screw thread exceeds 5mm, the bottom of the screw will be insufficiently thick. Further, the contact area of the slope of the screw thread increases, and the frictional force increases. As a result, it becomes difficult to manually screw in the screws.

Although the above embodiment has mainly been described with respect to a steel pipe pile, it is basically applicable to a steel pipe sheet pile.

Next, a joint pile operation was performed on the steel pipe pile of the present invention. FIG. 11 is an explanatory diagram illustrating a state of the joint pile operation. In the figure, 5 is a wire, 6 is a temporary scaffold, 7 is a worker, 13 is a hole, 22 is a mountain slope, and the other symbols are the same as in FIGS.

First, a winch or crane (not shown)
, The trailing pile 1b was suspended, and the center axis was aligned with the leading pile 1a. Then, the wire 5 was fed out and the trailing pile 1b was gradually lowered. Further, the tip of the male threaded joint 3 of the trailing pile 1b was lowered into the female threaded joint 2 of the preceding pile 1a, and when it could no longer descend, the feeding of the wire 5 was stopped.

At this time, the wire 5 was placed in a semi-suspended state so that the wire 5 was not completely loosened and a part of the weight of the trailing pile 1b was borne by the wire 5. In this state, the worker 7 on the temporary scaffold 6
However, the trailing pile 1b was manually rotated about two turns to screw the threaded joint. Although the threads of both threaded joints are in contact, the weight of the trailing pile 1b is only partially applied,
It is easily rotatable. Next, the chain tongue was hung around the trailing pile 1b, and further tightened about 1.5 turns until the tip of the female screw joint portion 2 hit the shoulder portion of the male screw joint portion 3.

As described above, in the steel pipe pile of the present invention, no special machine is required for the joint pile operation, so that there is no need to carry in a machine for tightening a screw joint or controlling torque. This is very meaningful on sites such as mountain slopes where roads are not well maintained. Also, as shown in the figure, the work floor may be a temporary scaffold 6 as long as the work can be performed by an operator, and there is no need to construct a full-scale work deck for installing a machine. Therefore, by using the steel pipe pile of the present invention, the incidental work for the joint pile work can be significantly reduced.

The results of an investigation on the workability at the site are as follows. Investigation is 350mm outside diameter, 20m thickness
A 7 m long steel pipe pile was used. The dimensions of the threaded joint are
The taper is 1/6, the thread height is 2.5 mm, and the pitch is 8.7 mm.

The on-site construction was carried out in a mountainous area in Nagano Prefecture. Of the 50 steel pipe piles described above, five were piled together, and ten landslide-preventing steel pipe piles having a total length of 35 m were built on the sloping ground. Therefore, the number of joints is four in each case for slip prevention steel pipe piles, for a total of 40 joints. Screwing of the succeeding pile in the joint pile work was performed by two workers.

As a result, the joint pile operation time was 18 minutes on average per one joint, and the time required for screwing was only 4 minutes. As for the workability, two workers could easily screw in. For comparison, a joint pile operation by welding, which has been performed before, was performed on a steel pipe pile in which the above-described steel pipe main body was grooved. In the joint pile work by welding,
It took 90 minutes on average for each joint to work.

[0074]

According to the present invention, a tapered screw is used in a screw joint structure applied to a screw joint of a steel pipe pile and a steel pipe sheet pile, so that the number of rotations required for screwing is greatly reduced, and the screw can be easily screwed by manpower. Can be included. As a result, it is not necessary to use a tightening machine, and it is possible to greatly reduce the construction period and cost of the entire operation including preparation of the joint pile operation.

Further, by appropriately defining the shape of the threaded joint, such as the angle of the slope of the thread, the strength of the threaded joint can be made equal to or less than that of the steel pipe main body without increasing the outer diameter of the threaded joint. It can be more.

[Brief description of the drawings]

FIG. 1 is a front view showing an appearance and a cross section of an embodiment of the present invention.

FIG. 2 is a sectional view showing a section of the threaded joint part of the embodiment.

FIG. 3 is a cross-sectional view showing a cross-sectional shape of a screw thread in a state where a screw joint portion is connected.

FIG. 4 is a cross-sectional view showing a contact state of a thread of a threaded joint portion during a joint pile operation.

FIG. 5 is an explanatory diagram showing a stress state when bending stress is applied to a steel pipe pile.

FIG. 6 is an explanatory diagram showing a deformation behavior of the threaded joint when there is no shoulder.

FIG. 7 is an explanatory view showing a state of a joint pile operation.

FIG. 8 is a sectional view showing a section when a steel pipe pile is joined.

FIG. 9 is an explanatory diagram showing an outline of a four-point loading pure bending test.

FIG. 10 is a load / displacement diagram showing the results of a bending test.

FIG. 11 is a load / displacement diagram showing a result of a bending test.

FIG. 12 is a sectional view showing a section of a joint of a conventional steel pipe pile.

FIG. 13 is a sectional view showing a section of a joint of a conventional steel pipe pile.

FIG. 14 is a front view showing the appearance of a joint of a conventional steel pipe pile.

FIG. 15 is a front view showing the appearance of a joint of a conventional steel pipe pile.

FIG. 16 is a front view showing the appearance of a joint of a conventional steel pipe pile.

FIG. 17 is a sectional view showing a section of a joint of a conventional steel pipe pile.

FIG. 18 is a cross-sectional view (triangular screw) showing a cross-section of a threaded joint in a conventional technique.

FIG. 19 is a cross-sectional view (trapezoidal screw) showing a cross-section of a threaded joint in the prior art.

FIG. 20 is a cross-sectional view (rectangular screw) showing a cross-section of a threaded joint in a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel pipe main body 2 Female screw joint part 3 Male screw joint part 8 Shoulder part 9 Screw joint part 16 Slope of steel pipe main body side of thread

Continuation of the front page (72) Inventor Gen Mori, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Hiroyuki Maeno 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-6-193054 (JP, A) Patent 2827845 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 5/24 E02D 5/04

Claims (3)

(57) [Claims] In a threaded joint structure of a male threaded joint portion and a female threaded joint portion provided at an end of a steel pipe main body for connecting a steel pipe pile or a steel pipe sheet pile, (a) the screw of the threaded joint portion is a tapered screw. (B) Of the two slopes of the thread of the threaded joint portion, the angle between the slope on the steel pipe main body side and the central axis is at least 75 degrees, and (c) the male threaded joint portion is a plate of the steel pipe main body. It has a shoulder with a step smaller than the thickness.
A screw joint structure, wherein an outer diameter of the female screw joint is equal to an outer diameter of the steel pipe main body. 2. The taper size of a screw of a threaded joint part is
The screw joint structure according to claim 1, wherein the ratio is 1/3 to 1/10. 3. A steel pipe pile or steel pipe provided with a male screw joint or a female screw joint based on the joint structure according to claim 1 at at least one end of a steel pipe main body. Sheet pile.