JP6581846B2 - Steel pipe pile - Google Patents

Description

  The present invention relates to a steel pipe pile driven into the ground by rotary press-fitting.

  Steel pipe piles are used as one of the foundation piles of buildings. As a method of driving this steel pipe pile into the ground, a method of hammering or the like is also known, but this method has a drawback in that there are restrictions on the construction site due to severe vibration and noise. Therefore, a method of gripping the steel pipe pile with a chuck or the like and press-fitting it into the ground while rotating is adopted. Rotational press-fitting is a method of screwing a steel pipe pile into the basement while rotating it with a cutting tool at the tip of the pile. Vibration and noise during construction are small, and ground disturbance can be reduced compared to other methods.

  Here, it is necessary to reduce the resistance of the ground acting on the steel pipe pile in order to improve the construction speed of the rotary press fitting in the sand ground or the like. For this purpose, Patent Document 1 discloses a steel pipe pile in which the outer dimension of the tip of the pile is tapered and a protrusion is provided on the outer peripheral surface thereof. Patent Document 2 discloses a steel pipe pile in which a wedge-shaped friction cutter is provided on the outer surface of the tip of the pile. Patent Document 3 discloses a steel pipe pile provided with a ring-shaped protrusion on the outer surface of the pile. Patent Document 4 discloses a steel pipe pile provided with a ridge extending in the entire longitudinal direction of the outer surface of the pile. Furthermore, Non-Patent Document 1 discloses a steel pipe pile in which a protrusion (shoe) is provided on the inner surface of the tip of the pile to reduce resistance. Non-Patent Document 2 discloses a steel pipe pile in which resistance is reduced by forming a hole penetrating obliquely on the side of the pile, and allowing the earth and sand generated during press-fitting to flow between the outer surface of the pile and the inner surface of the pile through the hole. Has been.

WO2012 / 005187 JP 2003-227134 A JP-A-9-291529 JP 2003-27469 A

5th International Conference on Deep Foundation Practice, Singapore. Pp 199-208 ”PRESS-IN PILING: THE INSTALLATION OF INSTRUMENTED STEEL TUBULAR PILES WITH AND WITHOUT DRIVING SHOES” TCRFinlay, DJWhite, MD Ltd, Japan PRESS-IN ENGINEERING 2011 Proceedingsof 3rd IPA International Workshop in Shanghai IPA PRESS-IN

  However, in the prior art, reduction of press-fit resistance is not sufficient, and there has been a demand for the appearance of a steel pipe pile that can further improve the construction speed of rotary press-fit on the ground. In particular, in the means of Patent Document 1 and Patent Document 2, the effect of reducing the resistance is limited to the tip portion, and there is a problem that the peripheral resistance generated when the steel pipe pile is rotationally press-fitted is not reduced. Moreover, although the steel pipe pile which provided the ring-shaped protrusion like the said patent document 3 is effective in the press-fit which does not rotate, when rotating, an effect may not be enough. Moreover, the steel pipe pile which provided the protruding item | line in the longitudinal direction whole region of the pile outer surface like the said patent document 4 had the subject that the raise of the torque to rotate will become high too much. Further, in Non-Patent Document 1, when a protrusion (shoe) is provided on the inner surface of the pile tip, the cross-sectional area of the pile tip increases, so the influence of the increase in tip resistance is greater than the reduction in peripheral resistance. Is likely to be. In addition, as in Non-Patent Document 2, the hole is formed on the side surface of the pile, which has a problem that the shape is complicated and processing takes cost and time.

  The objective of this invention is providing the steel pipe pile which can reduce press-fit resistance effectively and can improve the construction speed of the rotary press-fit in the ground.

In order to achieve the above object, according to the present invention, a steel pipe pile driven into the ground by rotary press-fitting, from the tip of a cylindrical steel pipe, 1.5 times or more and 3.5 times the outer diameter of the steel pipe A steel pipe pile is provided in which only one or two or more ribs continuous in the longitudinal direction of the steel pipe are attached to the outer peripheral surface of the steel pipe only in the following length range.

  In this steel pipe pile, it is desirable that the height of the rib is 12 mm or less. Further, it is desirable that two or more ribs are attached to the outer peripheral surface of the steel pipe, and no other ribs are present at positions opposite to the arbitrary ribs.

  According to the steel pipe pile of the present invention, when the steel pipe pile is rotationally press-fitted into the sand ground or the like by providing a rib continuous in the longitudinal direction of the steel pipe on the outer peripheral surface of the tip, the rear side of the rib is in contact with the ground. The contact area is reduced and the peripheral resistance is reduced. As a result, the peripheral friction acting on the steel pipe pile is reduced, and an excessive increase in rotational torque can be avoided and the speed of press-fitting can be improved.

It is a front view of the steel pipe pile concerning an embodiment of the invention. It is sectional drawing of the steel pipe pile which concerns on embodiment of this invention, (a) is the XX cross section in FIG. 1, (b) is the state seen in the arrow direction in the YY cross section in FIG. Indicates. It is drawing explaining the influence of the pushing force which acts on the steel pipe by the positional relationship of each rib, (a) shows the case where the other rib exists in the exact opposite position of a rib, (b) is a rib. The case where the other rib does not exist in the exact opposite position of is shown. It is explanatory drawing of the pile with a rib used for the model experiment. It is explanatory drawing of the pile without a rib used for the model experiment. It is a graph which shows the relationship between driving depth (penetration length) and rotational torque about two types of piles with and without a rib in a model experiment. It is a photograph which shows the comparison of the state of the pile before and after a model experiment, (a) shows the state before penetration (before experiment) and (b) shows the state after penetration (after experiment).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIGS. 1 and 2, the steel pipe pile 1 according to the embodiment of the present invention has a configuration in which three ribs 11 are attached to the outer peripheral surface at the tip (lower end in FIG. 1) of a cylindrical steel pipe (pipe) 10. have. A pair of suspension fittings 12 is attached to the other end (upper end in FIG. 1) of the steel pipe 10. The hanging metal fitting 12 is used when the steel pipe pile 1 is suspended and conveyed by a crane or the like.

  Each rib 11 is provided continuously in parallel with the longitudinal direction of the steel pipe 10 so as to extend upward from the tip (lower end) of the steel pipe 10, and the outer diameter D of the steel pipe 10 from the tip (lower end) of the steel pipe 10. Of 1.5 times or more and 3.5 times or less. That is, the length L of each rib 11 is set to 1.5D ≦ L ≦ 3.5D. In addition, according to the “UWA-05 support force estimation method”, the range from the tip of the steel pipe 10 to 2D is considered to receive particularly large peripheral surface resistance from the ground during rotary press-fitting. For this reason, the length L of each rib 11 is desirably 2D or more.

  The number of ribs 11 is arbitrary, and may be 1 or 2 or more. In this embodiment, three ribs 11 are provided. In the case of having two or more ribs 11, there are other ribs 11 at the positions opposite to the ribs 11 (positions where the central angle is 180 ° with respect to the ribs 11) on the outer peripheral surface of the steel pipe 10. It is desirable that they are not in a positional relationship. This embodiment will be described as an example. As shown in FIG. 2B, the three ribs 11 are arranged at the target positions at equal intervals of a central angle of 120 °, and the opposite positions of the ribs 11 are the same. There are no other ribs 11 (positions where the central angle is 180 ° with respect to each rib 11).

  Each rib 11 is provided by, for example, bonding a square bar or a round bar made of steel material to the outer peripheral surface of the tip end of the steel pipe 10 by welding or the like. In addition, each rib 11 is subjected to wear resistance processing by hardening or the like as necessary. The height H of each rib 11 is set to 12 mm or less. According to “Road Bridge Specification p558”, the height H of the rib 11 is in a range where the influence of the reduction in the bearing capacity after the completion of the construction of the steel pipe pile 1 is negligible, when the pile diameter is 800 mm or more and 1000 mm or less Is preferably 12 mm or less, and when the pile diameter is less than 800 mm, it is preferably selected within a range of 9 mm or less.

  The steel pipe pile 1 according to the embodiment of the present invention configured as described above is, for example, a self-propelled press-fitting construction machine disclosed in Japanese Patent Application Laid-Open No. 2003-213684 previously disclosed by the present applicant, It is rotationally pressed into the ground by the gyro press method (registered trademark No. 4794288) shown in http://www.giken.com/ja/). By gripping and rotating the steel pipe pile 1 by the gyro press method, the steel pipe pile 1 is rotationally press-fitted into the ground.

  Here, in the steel pipe pile 1 which concerns on embodiment of this invention, the steel pipe pile 1 is rotated to sand ground etc. by providing the rib 11 continuous in the longitudinal direction of the steel pipe 10 in the front-end | tip outer peripheral surface. When press-fitting, the area where the outer peripheral surface of the steel pipe 10 contacts the ground is reduced (or the contact pressure is weak) in the portion that is behind the rib 11 (opposite to the rotation direction) with respect to the direction of rotation. The peripheral resistance is reduced. As a result, the peripheral friction acting on the steel pipe pile 1 is reduced, and an excessive increase in pressure input can be avoided and the speed of press-fitting work can be improved. In this case, each rib 11 is provided in the range of the length of 1.5 times or more and 3.5 times or less of the outer diameter D of the steel pipe 10 from the tip of the steel pipe 10, and the height of each rib 11 is When the height H is set to 12 mm or less and the number of ribs is set appropriately, the amount of increase in the rotational torque due to the provision of the ribs 11 is within a certain range (for example, 10% of the rotational torque when the ribs 11 are not applied). % Or less).

  Further, in the steel pipe pile 1 according to the embodiment of the present invention, three ribs 11 are arranged at a target position at equal intervals of a central angle of 120 °, and the positions opposite to the ribs 11 (with respect to the ribs 11). Thus, no other rib 11 is present at a position where the central angle is 180 °. Thereby, the peripheral surface friction which acts on the steel pipe pile 1 can be reduced effectively, and it becomes possible to avoid the excessive deformation | transformation of the steel pipe 10 front-end | tip, and the excessive raise of a rotational torque.

  That is, FIG. 3A shows a case where another rib 11 is present at a position opposite to one rib 11 (a position where the central angle is 180 ° with respect to one rib 11). Show. When the steel pipe pile 1 is rotationally press-fitted into the ground, when a particularly large reaction force acts from the ground at the position of a certain rib 11, a force F that pushes the rib 11 into the center of the steel pipe 10 is generated. The rib 11 at a position opposite to the position 11 is pressed against the ground with a force F, and as a result, a large force is applied to both the ribs 11 and 11. Therefore, when the two ribs 11 and 11 are provided at positions opposite to each other, when the steel pipe pile 1 is driven into the ground by rotational press-fitting, a certain rib 11 receives a force F for pushing into the center of the steel pipe 10. As a result, the rotational torque tends to increase.

  On the other hand, FIG. 3B shows a case in which no other rib 11 exists at the opposite position (a position where the central angle is 180 ° with respect to one rib 11) with respect to one rib 11. Is shown. In this case as well, a force F that pushes into the center of the steel pipe 10 acts at the position where the rib 11 is provided, but at the position opposite to the rib 11, the outer peripheral surface of the steel pipe 10 directly contacts the ground excavated by the rib 11. In addition, the pushing force F is not easily transmitted directly to the other ribs 11. For this reason, the force applied to each rib 11 is difficult to increase, and the rotational torque is also difficult to increase.

  In FIG. 3B, the description has been made by describing one rib 11 on the outer peripheral surface of the steel pipe 10 for easy understanding. However, when two or more ribs 11 are provided, other ribs 11 are present on the outer peripheral surface of the steel pipe 10 at positions opposite to the ribs 11 (positions where the central angle is 180 ° with respect to the ribs 11). If the positional relationship is not, as in the case described with reference to FIG. 3B, the force applied to each rib 11 can be made difficult to increase, and as a result, the rotational torque can be made difficult to increase. There is an advantage that can be done.

  From the viewpoint of symmetry, when two or more ribs 11 are provided, each rib is provided in order to ensure a stable construction speed so that the rotation center of the steel pipe pile 1 does not deviate from the center of the steel pipe pile 1 as much as possible. It is desirable that the arrangement of 11 is equally spaced. However, when the number of the ribs 11 is an even number, when the ribs 11 are arranged at equal intervals, there is inevitably a relationship in which the other ribs 11 exist at positions opposite to the one rib 11. On the other hand, when the number of ribs 11 is an odd number, by arranging the ribs 11 at equal intervals, it is possible to realize a positional relationship in which no other ribs 11 are present at positions opposite to the ribs 11. Therefore, it is desirable that the number of ribs 11 is an odd number, and the ribs 11 are arranged at equal intervals on the outer peripheral surface tip of the steel pipe 10.

  As mentioned above, although an example of embodiment of this invention was demonstrated referring an accompanying drawing, this invention is not limited to this example. It is obvious for those skilled in the art that various modifications or modifications can be conceived within the scope of the idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

  For example, FIGS. 1 and 2 show a configuration in which three ribs 11 are provided on the outer peripheral surface of the steel pipe 10, but the number of ribs 11 can be 1 or 2 or more. As described above, it is desirable that the number of ribs 11 is an odd number, and the ribs 11 are arranged at equal intervals on the outer peripheral surface tip of the steel pipe 10. Further, when the number of the ribs 11 is as small as possible, the interval between the adjacent ribs 11 is extended, and the steel pipe 10 is easily elastically deformed. As a result, an increase in rotational torque can be suppressed.

  Next, an Example is shown and this invention is demonstrated concretely. First, a model experiment was performed using two types of piles with ribs shown in FIG. 4 and piles without ribs shown in FIG. In the pile with ribs shown in FIG. 4, a 3 mm × 3 mm square bar in the range from the tip to 250 mm at the tip of the steel pipe pile (steel pipe) having a pile length of 580 mm, a pile diameter of 101.6 mm, and a thickness of 4.2 mm, Three were attached so as to have a central angle of 120 °. On the other hand, the pile without a rib shown in FIG. 5 was a steel pipe pile (steel pipe) having a pile length of 580 mm, a pile diameter of 101.6 mm, and a thickness of 4.2 mm.

  The model test procedure is to rotate the pile head at the same rotational speed (approximately 8.5 rpm) while applying the same pile head load (maximum 100 kg) to these two types of piles with and without ribs. I let you. This method was used to grasp the difference between rotational torque and penetration when each pile was penetrated into dry sand.

  As a result of the model experiment, the torque was almost the same as shown in FIG. This is thought to be because in the pile with ribs, the decrease in friction behind the rib and the increase in resistance to the rib front were offset, and the increase in rotational torque was suppressed. On the other hand, the penetration length was longer with ribs. This is because the peripheral surface resistance in the vertical direction is reduced by the reduced friction behind the ribs, and the load required for penetration is small.

  A white line was formed in a ring shape on the outer peripheral surface of the pile with ribs in advance with an oil-based magic, and the remaining white line was observed after the experiment. FIG. 7A shows the state before penetration (before the experiment), and FIG. 7B shows the state after the ribbed pile is rotationally pressed into the model ground of dry sand and pulled out. As shown in FIG. 7A, the white line written in a ring shape before penetration (before the experiment) is shown in FIG. 7B after the penetration (after the experiment) on the front side of the rib. It was scraped and disappeared, and a white line remained behind the rib. From the remaining white line drawn in advance on the outer peripheral surface of the pile, it can be visually confirmed that the friction with the ground is reduced behind the rib (on the opposite side in the rotational direction).

  Next, a field experiment was conducted comparing the piles without ribs and those with ribs. The pile without a rib arrange | positioned the ring bit at the front-end | tip part of the steel pipe of pile length 15m, pile diameter 1m, and plate | board thickness 12mm. On the other hand, piles with ribs were attached by placing a 9 mm x 9 mm square steel rod on the outer peripheral surface of the pile without ribs in a range from the tip to 2.5 m and welding at equal intervals of 120 ° central angle ( 3 in total).

  In the field experiment procedure, two types of real piles, a ribless pile and a ribbed pile, were rotationally pressed into the gravel ground by the gyro press method, and the time required was compared. As a result of this field experiment, the time required for the penetration of 14 m was 95 minutes when there was no rib and 80 minutes when there was a rib.

  The present invention is useful in the construction field in which a pile is rotationally press-fitted into the ground.

1 Steel pipe pile 10 Steel pipe 11 Rib 12 Suspension fitting

Claims (3)

A steel pipe pile driven into the ground by rotary press fitting,
One or two or more ribs continuous in the longitudinal direction of the steel pipe are provided on the outer periphery of the steel pipe only in a range of 1.5 to 3.5 times the outer diameter of the steel pipe from the tip of the cylindrical steel pipe. Steel pipe pile, characterized in that it is attached to a surface.   The steel pipe pile according to claim 1, wherein a height of the rib is 12 mm or less.   The steel pipe pile according to claim 1 or 2, wherein two or more ribs are attached to the outer peripheral surface of the steel pipe, and no other rib is present at a position opposite to an arbitrary rib.