JP2005171496A - Screwing type steel pipe pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tip closed screwing type steel pipe pile having a pile body capable of sufficiently withstanding a large soil pressure acting thereon in installation without increasing the plate thickness of a steel pipe, having an excellent intrusion performance, and capable of providing a large tip supporting force. <P>SOLUTION: In this tip closed screwing type steel pipe pile 1, a blade 3 is installed at or near the tip part of the steel pipe 2 and intruded and buried in a ground by providing a rotating force to the steel pipe 2. A buckling prevention member 10 formed of a steel material is installed on the inner wall of the steel pipe 2 at or near the portion thereof receiving a large soil pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a screw-type steel pipe pile of a closed end type that is buried in the ground by a wood screw action of a wing by applying a rotational force to a steel pipe with a wing attached to or near the tip.

  Various types of screw-in steel pipe piles have been proposed in the past by attaching wings to the tip of the steel pipe and its vicinity and applying rotational force with construction machines installed on the ground to penetrate and embed the wing into the ground by the wood screw action. Since it can be constructed with low vibration, low noise, and no soil removal, it can be put into practical use in the field of civil engineering and construction because it can provide a large tip support force by utilizing the area of the wing after embedding.

  Such screw-type steel pipe piles can be broadly divided, and the pile tip is opened. In construction, the excavated earth and sand is taken into the pile body (tip-opened screw-type steel pipe pile), and the pile tip is In the construction, there is one that moves the excavated earth and sand to the side of the pile body (tip closed type screwed steel pipe pile).

  As an example of the screwed steel pipe pile as described above, a steel pipe pile provided with a screw-like closed blade plate on the inner wall of the upper position 2 to 4 times the inner diameter of the steel pipe from the tip of the steel pipe Press-fit while rotating, and after the tip of the steel pipe pile reaches the vicinity of the support layer of the ground, press-fit the steel pipe pile while reversing it, and construct it to form a compacted soil inside the tip of the steel pipe pile. There is one in which the effect is promoted to increase the supporting force (see, for example, Patent Document 1).

In addition, a spiral blade is provided on the outer periphery of the tip of the steel pipe, and an opening rib is provided in the steel pipe above the tip of the steel pipe to promote blockage of earth and sand when embedding the steel pipe pile. There is one in which an effective cylindrical portion is formed by the inner periphery of the steel pipe and the opening rib.
According to this screw-in type steel pipe pile, since the lower end is opened, the penetration resistance and the torque for penetration can be reduced, and the clogging of the earth and sand is promoted in the effective cylindrical portion by the open rib, The support bottom can be formed (see, for example, Patent Document 2).

  Further, there is a steel pipe with a spiral blade having an outer diameter almost twice as large as the outer diameter of the steel pipe projecting over one turn on the outer peripheral surface of the steel pipe and closed by attaching a bottom plate to the front end opening of the steel pipe. . This screw-in type steel pipe pile can be easily and efficiently laid without draining and has a large tip support force (see, for example, Patent Document 3).

Japanese Patent No. 2516475 (page 2, Fig. 1-3) JP-A-8-226124 (page 3, FIG. 1) Japanese Examined Patent Publication No. 2-62648 (page 2, Fig. 1)

  Since the screw-in type steel pipe pile of patent document 1 has only a screw-like obstruction blade board inside a steel pipe, even if it rotates a pile body, it cannot obtain sufficient propulsive force to set. In particular, when earth and sand enter the pile body and become closed, the closed blades are buried in the earth and no propulsive force can be obtained, so that it is impossible to penetrate into the ground.

  The screw-in type steel pipe pile of Patent Document 2 can reduce the penetration resistance and torque because the tip of the pile body is open, but the earth and sand are closed in the effective cylindrical part because the tip is open. Even if it does, a big tip supporting force cannot be obtained. For this reason, in order to obtain a sufficient tip support force, it is necessary to penetrate a solid support layer several times as long as the pile diameter, which is extremely uneconomical. In addition, in a large-diameter steel pipe pile having an open end, it is generally difficult to obtain a blocking effect on the end opening even if earth and sand are taken into the steel pipe pile during construction.

  Furthermore, the screw-type steel pipe pile of Patent Document 3 can obtain a large tip support force because the tip opening of the steel pipe is closed with a bottom plate, but since the pile body is hollow, earth pressure is applied to the pile body during construction. The thickness of the steel pipe must be increased because it may act and cause local buckling.

  The present invention has been made in order to solve the above problems, and has a pile body that can sufficiently withstand a large earth pressure acting during construction without increasing the thickness of the steel pipe, has good penetration performance, and has a large tip. An object of the present invention is to provide a screw-type steel pipe pile of a closed end type that can obtain a supporting force.

  The present invention relates to a screw-type steel pipe pile of a closed end type in which a blade is attached at or near the tip of a steel pipe and penetrates into the ground by applying a rotational force to the steel pipe. A buckling prevention member made of a steel material is provided on a portion where pressure acts or an inner wall in the vicinity thereof.

The above buckling prevention member was formed in a ring shape.
Moreover, it formed in the disk shape.
Furthermore, the steel materials were formed by combining in a cross shape, a triangular shape, or a Y shape.
A plurality of the buckling prevention members are provided in the longitudinal direction in the steel pipe.

  Further, the present invention provides a closed-end screw-type steel pipe in which a plurality of steel pipes are welded and joined, and a blade is attached at or near the front end portion to provide a rotational force to the steel pipe so as to penetrate into the ground. In the pile, any of the above buckling prevention members is used for the backing metal of the welded joint portion of the steel pipe.

  According to the present invention, since the buckling prevention member is provided on the site where the large earth pressure acts on the screw-type steel pipe pile or the inner wall in the vicinity thereof, local buckling does not occur in the pile body due to earth pressure during construction. It is possible to obtain a highly reliable closed-end screwed steel pipe pile.

As mentioned above, in the screw-type steel pipe pile of the closed end type, not only a large tip support force can be obtained, but also the ground support force due to circumferential friction can be increased. Since it moves to the side, very large earth pressure (passive earth pressure) acts on a hollow (hollow) pile body (steel pipe). For example, if a tip-closed screw-type steel pipe pile with a pile diameter of 1000 mm is constructed in a sand layer with a depth of 30 m and an N value of 30 in the vicinity of the tip, the analysis using the cavity expansion theory is about 4 times the static earth pressure. Earth pressure will act. For this reason, when a hollow steel pipe pile is constructed in a large earth pressure, local buckling may occur.
In order to avoid such local buckling, it is effective to increase the thickness of the steel pipe, but in order to construct a screwed steel pipe pile, the thickness of the steel pipe required at the time of design (for example, It is not economical to make it thicker than the plate thickness necessary to support the structure.

Therefore, in the present invention, in order to prevent local buckling from occurring in the steel pipe due to a large earth pressure, a buckling preventing member is provided on the inner wall of the steel pipe. According to the buckling theory of cylindrical shells, it is known that a short pipe with a circular end has a larger buckling load than a long pipe. As a result, the buckling strength of the entire steel pipe is increased, and local buckling does not occur even when a large earth pressure is applied without increasing the plate thickness of the steel pipe. In addition, since this steel buckling member should just hold | maintain circular, this buckling prevention member does not need to use a very rigid thing.
Hereinafter, embodiments of the present invention will be described in detail.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view and a plan view of a screw-in type steel pipe pile according to Embodiment 1 of the present invention.
In the figure, 2 is a steel pipe, 3 is a steel wing which is attached to the tip of the steel pipe 2 so as to be inclined and covers and closes the tip opening of the steel pipe 2. 10 is a ring-shaped buckling-preventing member made of a steel material that is attached by welding or the like to a portion where the large earth pressure acts on the steel pipe in the longitudinal direction (vertical direction) of the steel pipe 2 or the inner wall in the vicinity thereof. A tip-closed screw-type steel pipe pile 1 (hereinafter simply referred to as a steel pipe pile) according to the present invention is configured.

  The steel wing 3 constituting the steel pipe pile 1 is provided with two L-shaped attachments at the tip of the steel pipe 2 in the figure and a diameter larger than the outer diameter of the steel pipe 2 (for example, the outer diameter of the steel pipe 2). A semi-circular wing plate is formed by dividing a steel disk of about 2 times) into a semicircular blade plate, and this blade plate is formed by attaching it to the mounting portion of the steel pipe 2 at an angle by welding while covering the opening at the tip. For example, instead of the tip of the steel pipe, a blade plate or a spiral steel blade obtained by dividing a donut-shaped steel plate into a plurality of outer peripheries in the vicinity of the tip of the steel pipe is attached and the tip of the steel pipe is opened. In the present invention, the shape, structure, mounting position, etc. of the steel blade 3 are not particularly limited and can be appropriately selected.

  Further, the buckling prevention member 10 is made of, for example, a ring-shaped steel material having a square cross section, a rebar bar or a shape steel bent into a circular shape, and has a rigidity higher than the strength. It is desirable to use materials. The size and shape of the cross-sectional area of the ring-shaped steel material and the outer diameter of the reinforcing bar differ depending on the outer diameter of the steel pipe to which they are attached, the plate thickness, the condition of the ground to be constructed, etc., and are determined at the time of design. (The same applies to the following embodiments).

Next, the mounting position of the buckling prevention member 10 will be described.
The earth pressure acting on the steel pipe pile (hereinafter, sometimes referred to as a pile body) changes according to the N value of the ground, and a pile body having a large buckling strength is required at a place where the N value is large. This earth pressure can be reduced to some extent by moving the pile body up and down during construction, etc., by softening and moving the earth and sand on the peripheral surface of the pile body, but it takes construction time, Depending on the ground, the softened state may quickly recover and there may be no effect at all, the earth and sand will be discharged from the periphery of the pile body, making it impossible to perform construction without draining, and the operator operating the construction machine Since there are many uncertain factors, such as affecting the skill level of the construction, reduction of earth pressure by this construction method cannot be expected.

  FIG. 2 shows an example of the ground for constructing a steel pipe pile 1 having a pile diameter of 1000 mm and a pile length of 30 m, for example, the soil quality and its depth on the vertical axis, and the N value on the horizontal axis. As shown in the figure, the N value is extremely small in the range of about 17 to 18 m from the topsoil layer to the clay layer, the N value is drastically increased in the sand layer at a depth of about 18 m or more, and N in the vicinity of the depth of 20 to 22 m. The value is 50, and the N value is reduced to about 10 in the silt layer near the depth of 23 to 24 m, but the N value is increased again, and the N value is 50 in the sand layer (support layer) deeper than 27 m.

When steel pipe piles 1 are penetrated into such ground, steel pipe piles 1 have a large N value in the vicinity of a depth of 20 to 22 m (intermediate layer) and a depth of about 27 m or more (support layer). Corresponding to this, it will receive a large earth pressure. In this case, according to the analysis using the cavity expansion theory, an earth pressure of about 2 N / mm ² acts on the steel pipe pile 1 in the intermediate layer and the support layer.

  Therefore, the position where the earth pressure acting on the steel pipe pile 1 is high, that is, the position corresponding to the support layer and the intermediate layer, in other words, the inner wall of the vicinity of the tip portion of the steel pipe pile 1 and the position approximately 10 m above the tip portion. If the prevention member 10 is provided, the steel pipe pile 1 has high rigidity and can maintain a circular shape without causing local buckling due to earth pressure. Thus, in the ground having the intermediate layer, the pile body passes through the intermediate layer until the tip of the pile reaches the support layer, and therefore one or a plurality of buckling prevention members 10 are provided in the section. Avoid local buckling. Moreover, what is necessary is just to install the space | interval of the member 10 for buckling prevention short when a big earth pressure acts continuously. However, since the steel blade 3 is provided at the tip and has high rigidity, there is no risk of local buckling in the vicinity due to earth pressure, and the tip has the same effect as the buckling prevention member. You may think that you have.

FIG. 3 is a diagram showing the relationship between the plate thickness and the earth pressure of the steel pipe pile 1 having a pile diameter of 1000 mm provided with the buckling prevention member 10 and the mounting positions (intervals, m) of the plurality of buckling prevention members 10. The vertical axis shows earth pressure (N / mm ² ), and the horizontal axis shows the plate thickness (mm).
Now, for example, when an external pressure of ² N / mm ² is applied to the steel pipe pile 1, if the spacing between the buckling prevention members 10 is 10 m, the steel pipe needs a plate thickness of 18 mm or more, and the spacing is 7 m. In this case, when the plate thickness is about 16 mm and the interval is 5 m, it is understood that the plate thickness may be about 14 mm (see FIG. 2).

FIG. 4 is a diagram showing how much earth pressure the plate thickness can withstand in the case of a steel pipe pile 1 having a pile diameter of 1500 mm provided with a buckling prevention member 10, and the vertical axis represents earth pressure (N / Mm ² ), and the horizontal axis indicates the plate thickness (mm). If the thickness of the steel pipe was set to 20 mm, in the case of about 2N / mm ^2, 5m case of when the interval between the buckling prevention member 10 is 10m to about 1.5N / mm ^2, 7m about 3N / mm ² It can be understood that it can withstand the earth pressure.

3 and 4, if the steel pipe pile 1 is provided with a buckling prevention member 10 at an interval of 5 m, it is ² N / mm ² with a plate thickness of 14 mm, not only for a small diameter but also for a large diameter steel pipe pile 1. It was found that it can withstand enough earth pressure.

  From the above description, when the steel pipe pile 1 having a pile diameter of 1000 mm is constructed on the ground shown in FIG. 2, the plate thickness at the time of sharing is 14 mm, but in order to prevent buckling due to earth pressure, 20 mm It is uneconomical because it requires plate thickness. In addition, it is conceivable to increase the plate thickness only in a section where local buckling occurs in design, but the design and manufacturing become complicated, and the cost rise is inevitable.

Therefore, in the present embodiment, the ring-shaped first buckling prevention member 10 is provided on the inner wall at a position 10 m above (L _{1 in} FIG. ₁ ) from the tip of the steel pipe pile 1, and further, Depending on the state, the second buckling prevention member 10 was provided 5 m above the first buckling prevention member 10 (L _{2 in} FIG. 1). Hereinafter, the buckling prevention member 10 may be provided at intervals of 5 m according to this. As shown in FIG. 2, the buckling prevention member 10 may be provided at a position 5 m above the tip of the steel pipe pile 1, and the buckling prevention member 10 may be provided thereabove at an interval of 5 m. As described above, since the steel blade 3 is attached to the tip of the steel pipe pile 1 to provide great rigidity, the buckling prevention member 10 5 m above the tip may be omitted.

The steel pipe pile 1 configured as described above is rotated by a pile head connected to a construction machine provided on the ground (head rotation method), and the ground near the tip of the pile is softened by excavation by the steel blade 3. However, it is penetrated into the ground and buried by the wood screw action of the steel wing 3. At this time, the earth and sand near the tip of the pile moves to the outer periphery of the steel pipe pile 1 and does not enter the pipe.
In the construction, a large earth pressure acts on the pile body due to the earth and sand moved to the outer periphery. However, since the buckling prevention member 10 is provided on the inner wall of the pile body, local buckling does not occur.

  Further, the body of the steel pipe pile 1 may be chucked and rotated (body rotation method), and in this case, since the buckling prevention member 10 is provided, the deformation of the pile body is prevented. Can do. In addition, since large earth pressure may be applied by the construction of the adjacent steel pipe pile 1 after construction, construction residual soil, concrete, soil cement, etc. are put into the pile body and synthesized to make it difficult to buckle. Also good.

According to the present embodiment, since the buckling prevention member 10 is provided on the site where the large earth pressure acts on the steel pipe pile 1 or the inner wall in the vicinity thereof, local buckling occurs in the pile body due to earth pressure during construction. Can be prevented and can be constructed efficiently.
Moreover, although torque and pushing force act on the steel pipe pile 1 at the time of construction, since the buckling prevention member 10 has a stiffening effect against these external forces, deformation and breakage of the steel pipe pile 1 are caused. Can be prevented.
Further, since the steel pipe pile 1 is closed at the tip opening portion, it is possible to obtain a large tip support force in combination with the steel blade 3, and the peripheral surface by the earth and sand moved to the outer peripheral portion of the steel pipe pile 1 Since the frictional force increases, a highly reliable screwed steel pipe pile 1 can be provided.

[Embodiment 2]
FIG. 5 is a schematic cross-sectional view and a plan view of a screw-in type steel pipe pile according to Embodiment 2 of the present invention, and FIG. 6 is a plan explanatory view of another example of the present embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In Embodiment 1, although the case where the ring-shaped buckling prevention member 10 was provided in the site | part which the big earth pressure acts on a pile body at the time of construction or the inner wall of the vicinity was shown, this Embodiment is a ring shape. Instead of the buckling prevention member 10, a rib-like buckling prevention member 10 made of a steel bar or the like is provided.

FIG. 5 shows a buckling prevention member 10 composed of a cross-shaped rib 11 formed of a polygonal steel bar such as a square cross section, a reinforcing bar, a shaped steel or the like attached to the inner wall of the steel pipe pile 1 by welding.
6 (a) shows a structure in which a buckling prevention member 10 made of triangular ribs 12 is attached to the inner wall of the steel pipe pile 1 with the same steel material as in FIG. 5, and FIG. 6 (b) shows the same material. The buckling prevention member 10 composed of the formed Y-shaped ribs 13 is attached to the inner wall of the steel pipe pile 1.

  The attachment position of the buckling prevention member 10 according to the present embodiment is the same as that in the first embodiment, and substantially the same effect as in the first embodiment can be obtained.

[Embodiment 3]
FIG. 7 is a schematic cross-sectional view and a plan view of a screw-in type steel pipe pile according to Embodiment 3 of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In the present embodiment, instead of the ring-shaped buckling prevention member 10 of the first embodiment, the buckling prevention member 10 is formed of a circular steel plate 14 having an outer diameter substantially equal to the inner diameter of the steel pipe pile 1, and the steel pipe It is attached to the inner wall of the pile 1 and its attachment position is the same as in the first embodiment.
Even in the present embodiment, substantially the same effect as in the first embodiment can be obtained, but the present invention is particularly effective when applied to a steel pipe pile having a relatively small pile diameter.

[Embodiment 4]
When the steel pipe pile 1 becomes long, welding work for joining the steel pipe is surely generated at the site. For example, if the pile length is 36 m, three piles of 12 m are joined by welding. At this time, there are two welds on site. And when joining a pile and a pile by welding, the ring-shaped backing metal is normally used.
In the present embodiment, the buckling strength of the pile body is increased by using the ring-shaped buckling preventing member 10 according to the first embodiment for the backing metal.

  When a backing metal made of a ring-shaped buckling prevention member 10 having high rigidity is used for joining the piles, the first joint is about 10 to 12 m from the tip of the pile, and the distance to the next joint is 10 to 10 m. The buckling strength of the pile body is slightly reduced compared to the case where the buckling prevention member 10 is provided at intervals of 5 m as in the case of the first embodiment because the opening is about 12 m. Since it is always used at the time of welding joining, an increase in cost can be suppressed by this.

In the above description, the case where the ring-shaped buckling prevention member 10 is used as the backing metal at the time of joining the piles is shown, but instead, the buckling made of the circular steel plate 14 according to the third embodiment. The prevention member 10 may be used.
Moreover, you may attach the member 10 for buckling prevention which concerns on any of Embodiment 1-3 to the intermediate part of the joint part (joint part) of a pile by the state of the ground and other conditions.
According to the present embodiment, substantially the same effect as in the first embodiment can be obtained.
Further, as a joining method other than welding, there is a threaded joint or the like. If the rigidity of such a joint is increased, the same effect as the buckling prevention member 10 can be obtained.

[Comparative example]
Next, a comparative example between the conventional screw-type steel pipe pile and the screw-type steel pipe pile according to Embodiment 1 of the present invention will be described.
The steel pipe pile has a pile diameter of 1000 mm, a plate thickness of 14 mm, and a length of 30 m. The conventional steel pipe pile uses this steel pipe pile as it is, and the steel pipe pile 1 according to the present invention is formed on the steel pipe pile having the same structure as described above from the tip. A ring-shaped buckling-preventing member 10 having a side of 19 mm and a quadrangular section was welded to the inner wall 5 m above and the inner wall 5 m above. In addition, construction was performed on the same ground as the soil shown in FIG.

When a conventional steel pipe pile is rotated by a construction machine and penetrates into the ground until it reaches the support layer, then the steel pipe pile is rotated in the opposite direction and pulled up, and is inspected. Local buckling occurred.
Similarly, after the steel pipe pile 1 according to the present invention was penetrated into the ground until reaching the support layer, the steel pipe pile 1 was rotated in the opposite direction and pulled up, and no abnormality was observed in the pile body.
In the above description, the steel pipe pile that has penetrated to the support layer has been described as being inspected by rotating it in the opposite direction. A camera may be inserted and observed to inspect for the occurrence of local buckling.

It is a typical sectional view and a top view of a screwed-type steel pipe pile concerning Embodiment 1 of the present invention. It is explanatory drawing which shows the relationship between an example of the ground which constructs the screwed-type steel pipe pile which concerns on this Embodiment, and the conventional screwed-type steel pipe pile corresponding to this, and the screwed-type steel pipe pile which concerns on this Embodiment. It is a diagram which shows the relationship between the plate | board thickness and earth pressure of a screwed-type steel pipe pile with a pile diameter of 1000 mm, and the attachment position of the several member for buckling prevention. It is a diagram showing how much earth pressure can withstand the plate thickness of a threaded steel pipe pile with a pile diameter of 1500 mm. It is the typical sectional view and top view of the screwed-type steel pipe pile concerning Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram of another example of the second embodiment. It is a typical sectional view and a top view of a screwed-type steel pipe pile concerning Embodiment 3 of the present invention.

Explanation of symbols

1 Screwed steel pipe pile, 2 steel pipe, 3 steel blades, 10 buckling prevention member.

Claims (6)

In a screw-type steel pipe pile of a closed end type that has a blade attached to the tip of the steel pipe or in the vicinity thereof and is embedded in the ground by giving a rotational force to the steel pipe,
A screw-type steel pipe pile, wherein a member for preventing buckling made of steel is provided on a portion of the steel pipe where a large earth pressure acts or an inner wall in the vicinity thereof.   The screw-type steel pipe pile according to claim 1, wherein the buckling prevention member has a ring shape.   The screwed steel pipe pile according to claim 1, wherein the buckling prevention member has a disk shape.   The screwed-type steel pipe pile according to claim 1, wherein the buckling prevention member is formed by combining steel materials in a cross shape, a triangular shape, or a Y shape.   The screwed steel pipe pile according to any one of claims 1 to 4, wherein a plurality of the buckling prevention members are provided in a longitudinal direction in the steel pipe. A plurality of steel pipes are welded and joined, and a tip closed type screwed steel pipe pile that is embedded in the ground by attaching a blade at or near the tip and applying a rotational force to the steel pipe,
A screw-type steel pipe pile, wherein the buckling prevention member according to any one of claims 1 to 3 is used for a backing metal of a welded joint portion of the steel pipe.

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