JP2006207320A - Structure of steel pipe pile end for pile installation by inner excavation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved simple structure of steel pipe pile lead end used for pile installation by inner excavation, the structure being simple and smoothly transmitting upper loads to a foundation consolidation bulb. <P>SOLUTION: Regarding a steel pipe pile for forming a foundation consolidation bulb 7 by injecting cement milk into the pile lead end having reached the support layer 2 of ground 5 in pile installation by inner excavation, in the lead end of a steel pipe pile 11, the pile lead end protrusion 14 protruding inwardly and outwardly from the pipe wall is formed in a circumferential direction. Also the steel pipe pile 11 has a plurality of circumferentially extending inner protrusion steps 101 from its inner pipe wall surface over an area from its leading end upward, having the upper part 7a of foundation consolidation bulb formed there, to constitute the transmission of loads 12 from the pile body to the foundation consolidation bulb 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a tip shape of a steel pipe pile applied to a highly supported intermediate excavation method used in the building foundation field. More specifically, an auger screw is inserted into the steel pipe pile and rotated, and the pile is supported by the pushing device using the pile driver's own weight as a reaction force while continuously excavating and discharging the soil at the tip of the pile. It is related to a pile tip structure for increasing the bearing capacity of a steel pipe pile in a construction method in which cement milk is injected at a high pressure of 20 to 24 MPa or more at a high pressure of 20 to 24 MPa, and then a root solidified expanded bulb is created. .

  Steel pipe pile foundation is a foundation method with excellent properties such as bearing capacity, deformation performance and workability, and is a general method used in a wide range of fields. The steel pipe pile construction methods include the driving pile method and the excavation method, and the excavation methods include the pre-boring pile method and the intermediate excavation method.

  In the mid-pile method, the auger screw inserted into the hollow part of the pile is rotated to excavate and evacuate the ground at the tip of the pile. It is a construction method. The digging pile method is generally a method for large-diameter piles and does not cause noise and vibration such as the driving pile method. However, the loosening of the pile tip and the surrounding soil due to excavation is a problem in terms of bearing capacity. Sufficient construction management is necessary, such as ensuring the quality of root bulbs. In particular, the tip of the steel pipe pile is inserted into the enlarged root bulb with cement milk (soil cement) built at the tip of the pile, only to a depth corresponding to the diameter of the pile, but the adhesion to the soil cement is weak. There is a problem that the supporting force of the period cannot be expressed, and the present invention relates to the improvement of this point.

  A general Nakabori method will be described in the following first to eighth steps (in addition, the fifth to seventh steps are shown in FIGS. 6A, 6B, and 6C).

(1) Insert an auger screw into the hollow part of the steel pipe pile and build it with a crane.
(2) Join the auger device and the auger screw to ensure verticality.
(3) The auger screw is rotated and the press-fitting device is operated to press-fit the pile while excavating and discharging the soil at the tip of the pile. Air is jetted from the auger head as needed.
(4) The upper pile is built and the two upper and lower auger screws are joined, and the joint plate portion is welded.

(5) The same work as the lower pile is repeated to press-fit the steel pipe pile 1 to the support layer 2 of the ground 5 (see FIG. 6a).
(6) After the tip of the pile reaches the support layer 2, high pressure water is sprayed while rotating the auger screw 3, and the consolidation range 4 is preliminarily excavated to a predetermined depth. (See Figure 6b)
(7) As soon as the auger screw 3 reaches a predetermined depth, the auger screw 3 is switched to a root-setting liquid (cement milk 6), sprayed at a high pressure of 20 to 24 MPa or more, and pulled up while rotating the auger screw 3. (See Figure 6c)
(8) The injection is completed to a predetermined position inside the pile. Then pull out the auger screw.

  FIGS. 7 (a) and 7 (b) are detailed views of the process of building the rooted bulbs of FIGS. 6 (b) and 6 (c). 7 (a) and 7 (b), [1] While rotating the auger screw 3, water is injected to preliminarily clean the inner surface of the steel pipe. [2] The auger screw 3 is lowered to a predetermined depth while performing water injection on the support layer 2 as well. [3] When the auger screw 3 reaches a predetermined depth, the auger screw 3 is switched from water to the cement milk 6, and the auger screw 3 is pulled up at a constant speed while rotating to make the enlarged tip rooted bulb 7. [4] Cement milk 6 is jetted into the steel pipe pile 1 at a high pressure, the inner surface of the pipe is sufficiently cleaned, and poured to a predetermined position.

  The root-setting method is a method of constructing a root-setting step using an auger screw and head for Nakahori as they are, but there are the following three types of the root-setting step. (1) After completion of the Nakabori process, pull out the auger screw, rotate the leader 90 °, and insert the rooting rod. (2) After completion of the Nakabori process, pull out the auger screw and insert the root with a boring machine. (4) After completion of the Nakabori process, pull out the auger screw and insert the rooting rod with a dedicated pile driving machine. The present invention is a tip structure of a steel pipe pile that can be used for any of the above-mentioned root-solidifying methods.

  Patent documents relating to the rooting method include JP-A No. 2002-322644, JP-A No. 2002-18462, JP-A No. 5-140929, and the like.

  In the technique disclosed in Japanese Patent Laid-Open No. 2002-322644, a perforated bottom plate is fixed to the tip of a steel pipe pile, and a tip cylindrical tube having a diameter larger than that of the steel pipe pile is fixed to the perforated bottom plate. By filling the enclosed portion with a rooting material such as concrete or mortar, the tip is closed, and the embedded pile has a supporting force corresponding to the diameter of the tip cylindrical tube.

  The technique disclosed in Japanese Patent Laid-Open No. 2002-180462 excavates a hole having a diameter less than or equal to the outer diameter of the pile body to a predetermined depth by a pre-auger method, expands the vicinity of the tip of the excavation hole, and injects cement milk to form a soil cement After that, a pile having a plurality of spiral blades near the tip of the pile is rotationally pressed into the excavation hole.

The technique disclosed in Japanese Patent Laid-Open No. 5-140929 is a pile foundation in which protrusions are attached to the inner and outer surfaces of a steel pipe column.
JP 2002-322644 A JP 2002-180462 A Japanese Patent Laid-Open No. 5-140929

  In the technique disclosed in Japanese Patent Application Laid-Open No. 2002-322644, the protrusions inside and outside the steel pipe increase the resistance when buried in the ground, and the construction efficiency decreases. In the technique disclosed in Japanese Patent Application Laid-Open No. 2002-180462, the processing cost and the manufacturing cost become high and the manufacturing period becomes long. Since the technique disclosed in Japanese Patent Laid-Open No. 5-140929 has a structure in which the protrusion is attached by welding, it is necessary to perform quality control by an ultrasonic flaw detection test or a radiation transmission test, which is expensive and labor intensive.

  In the Nakabori method, there is a problem that if the adhesive strength between the soil cement rooting bulb and the steel pipe pile is weak, the steel pipe pile cannot express the desired bearing force. The conventional method for solving this problem has a complicated structure at the tip of the pile, which is expensive and costly. Therefore, the present invention improves the conventional defect, and has a simple structure and smoothly roots the upper load. It aims at providing the tip part structure of the steel pipe pile which can be transmitted to a bulb.

  In order to achieve the above object, the present invention is configured as follows.

  1st invention is the steel pipe pile which inject | pours cement milk into the pile front-end | tip part which reached the support layer of the ground by the digging method, and builds up the rooting bulb, The pile front-end | tip protrusion which protrudes in and out of a steel pipe is made into the circumferential direction. In addition to providing a steel tube inner surface protrusion or multiple steps extending in the circumferential direction over the range where the upper part of the root consolidation bulb is provided upward from the tip of the steel pipe, it is rooted from the pile body by the pile tip protrusion and the inner surface protrusion. It is characterized in that a load transmission portion for transmitting a load to the bulb is configured.

  The second invention is characterized in that, in the first invention, one or more outer surface protrusions are provided on the outer surface of the steel pipe pile corresponding to the inner surface protrusions.

  According to a third invention, in the first or second invention, the pile tip protrusion has a downward projecting shape for earth pressure reduction at the time of pile embedding.

  According to a fourth aspect of the present invention, in the first to third aspects, the inner surface protrusion has a rectangular cross-sectional shape perpendicular to the circumferential direction or a tapered or stepped shape having an enlarged diameter on the lower side.

According to the present invention, the support pressure effect with the root compaction bulb is improved by the tip projection of the steel tube pile, and the bearing effect is improved even when the inner surface projection bites into the upper part of the root consolidation bulb in the steel pipe. The upper load can be divided and transmitted by the inner surface protrusion, and a large load can be smoothly transmitted to the soil cement rooting bulb. Furthermore, by providing a downward protruding portion shape on the pile tip protrusion, the earth pressure at the time of pile embedding can be reduced, and the press fitting of the steel pipe pile can be smoothly performed. In addition, by adopting a structure in which the protrusions on the inner and outer surfaces of the steel pipe are expanded in diameter on the lower side, the resistance when buried in the ground can be reduced, and the steel pipe pile can be smoothly press-fitted.

  Embodiments of the present invention will be described below with reference to the drawings.

  Fig.1 (a) shows the outline | summary of the steel pipe pile applied to the intermediate excavation method of this invention in the steel pipe pile used for the foundation of a structure. (B) is a detail drawing of the A section of Drawing (a).

  In the present invention, in a steel pipe pile 11 in which a rooted bulb 7 is constructed by cement milk (soil cement) 6 in order to transmit the upper load to the pile tip that has reached the support layer 2 of the ground 5 by the intermediate excavation method. A pile tip projection 8 projecting inward and outward of the pipe wall is provided at the tip of the steel pipe pile 11 in the circumferential direction, and an inner surface projection 10 extending in the circumferential direction over a predetermined range (L) from the tip portion of the steel pipe pile 11 is provided. One or a plurality of steps are provided, and the pile tip protrusion 8 and the inner surface protrusion 10 constitute a high load transmission portion 12 that can transmit a high load from the pile body to the root consolidation bulb 7. The range (L) means the height at which the cement milk 6 constituting the root-clamping bulb 7 goes around the steel pipe pile 11 (that is, the height of the root-clamping bulb upper portion 7a). The protrusion height to the inner side of the inner surface protrusion 10 is set to a height that does not interfere with the blades of the auger screw during the construction of the intermediate excavation method.

  FIG.1 (c) is a modification of figure (a), (b), and the outer surface protrusion 13 extended in the circumferential direction is provided in the upper predetermined range (L) from the front-end | tip part of a pile body. In this modification, the high load transmission portion 12 is configured by the pile tip protrusion 8, the inner surface protrusion 10, and the outer surface protrusion 13. In the figure, the outer protrusion 13 is provided with the same height as the inner protrusion 10 for balance. However, the outer protrusion 13 digs into the surrounding ground and exhibits a frictional resistance, so even if it is provided up to a position higher than the inner protrusion 10. Good.

  A conical downward projection 14 for reducing earth pressure when embedding the steel pipe pile 11 is provided on the lower surface of the pile tip protrusion 8, thereby facilitating construction when embedding the steel pipe pile 11. Moreover, although the cross section of the inner surface protrusion 10 and the outer surface protrusion 13 is formed in a rectangular shape in the drawing, other shapes may be used.

  The steel pipe pile 11 is embedded in the ground in the same manner as before. That is, an auger screw is erected on the ground 5 on which the pile is to be built, and the auger screw is rotated and the press-fitting device is operated to press-fit the steel pipe pile 11 to the support layer 2 while excavating and discharging the soil at the tip of the pile. (Air is ejected from the auger head as necessary). After the pile tip reaches the support layer 2, the auger screw is rotated while spraying water on the support layer and lowered to the depth. When the auger screw reaches a predetermined depth, the water is switched to cement milk, and the screw rod is rotated and pulled up at a constant speed to form a root-fixing bulb 7. Also, the cement milk 6 is poured into the steel pipe pile 11 to a predetermined position.

  In the lower end support structure of the steel pipe pile 11 constructed by the Nakabori method, in FIGS. 1 (a) and 1 (b), the upper portion of the root-solidifying bulb 7 formed to bulge and form a larger diameter than the pile body at the lower portion of the lower end of the pile. The pile tip protrusion 8 is firmly locked so as to grab and the inner surface protrusion 10 bites into the root hardening bulb upper portion 7a that has turned into the steel pipe. As a result, the upper load acting on the steel pipe pile 11 can be divided by the pile tip protrusion 8 and the inner surface protrusion 10 and transmitted to the root consolidation bulb 7, and the large load acting on the steel pipe pile 11 can be smoothly applied to the soil cement root consolidation bulb 7. Can communicate.

  Furthermore, the downward projection 14 provided on the pile tip projection 8 can reduce the earth pressure when the steel pipe pile 11 is embedded, and can smoothly press the pile body. Further, by providing the outer surface protrusion 13 as shown in FIG. 1 (b), the outer surface protrusion 13 bites into the ground 5 so that the upper load can be divided on both the inner and outer surfaces of the steel pipe pile 11, and the root bulb 7 can be solidified from the pile body. Load transmission to the is even more reliable.

  There are various specific examples of the cross-sectional shapes of the pile tip protrusion 8, the inner protrusion 10, and the outer protrusion 13. 2 to 5 show specific structural examples 1 to 8 of the pile tip protrusion 8, the inner protrusion 10, and the outer protrusion 13. This will be described in order below.

  2A and 2B show first and second specific examples. In Fig.2 (a), the pile front-end | tip protrusion 8 is comprised from the outer side rectangular protrusion part 8a, the downward part rectangular protrusion part 14a, and the inner side rectangular protrusion part 8b. The inner surface protrusion 10 has a plurality of rectangular concave portions and convex portions at equal intervals and at the same height, and is provided up to a height (range L) around which the upper portion 7a of the root cemented bulb 7 made of soil cement turns. . With such a configuration, the protrusions 8a, 14b, 8c and the inner surface protrusion 10 in the pile tip protrusion 8 firmly bite into the soil cement of the root bulb 7, and the load on the pile body is shared by the cooperation of each part. Can be transmitted to the root-fixing bulb 7. Moreover, the resistance of the soil received at the time of construction which embeds the steel pipe pile 11 by the lower part rectangular protrusion part 14b can be reduced.

  In the second specific example shown in FIG. 2B, the pile tip protrusion 8 is composed of an outer rectangular protrusion 8a, a lower tapered protrusion 14b, and an inner rectangular protrusion 8b. The inner surface protrusion 10 of the steel pipe is provided with a plurality of rectangular concave portions and convex portions at equal intervals and at the same height, and is provided up to a height (range L) around which the upper portion 7a of the root hardening bulb 7 is turned. Even in such a configuration, as in FIG. 2a, the protrusions 8a, 8b, 14b and the inner surface protrusion 10 of the pile tip protrusion 8 bite into the rooted bulb 7 to share the load applied to the pile body. It can be transmitted to the compacted bulb 7. Moreover, the resistance of the soil received at the time of the construction which embeds the steel pipe pile 11 by the downward part taper protrusion part 14b can be reduced.

  FIGS. 3A and 3B show third and fourth specific examples. In Fig.3 (a), (b), the outer surface protrusion 13 is provided in the position corresponding to the inner surface protrusion 10 in the outer surface of a pile body, FIG.3 (a) is FIG. 3A is the same as the first specific example of FIG. 2A, and FIG. 3B is the same as the second specific example of FIG. In the third and fourth specific examples, the steel pipe outer surface protrusions 13 are provided, respectively, so that the load applied to the pile body is distributed and solidified by more protrusions than in the first and second specific examples. It can be reliably transmitted to the bulb 7.

  4A and 4B show fifth and sixth specific examples. 4A will be described in comparison with FIG. 2A. In FIG. 4A, a taper 8d whose lower side is reduced in diameter is formed on the outer surface of the outer rectangular protrusion 8a of the pile tip protrusion 8. Has been. Other configurations are the same as those of the first specific example of FIG. According to the fifth specific example, since the outer rectangular protrusion 8a is formed with a taper 8d, an acute-angled protrusion is formed in the lower portion, so that the resistance of the soil received when embedding the steel pipe pile 11 is the first specific example. This can be further reduced as compared with the above.

  4B will be described in comparison with FIG. 2B. In FIG. 4B, the upper surface of the inner surface protrusion 10 provided on the inner surface of the pile body has a large protrusion on the lower side. By forming a stepped portion 10a having a small protrusion on the side, the inner protrusion 10 is viewed as a whole so that the diameter of the lower part is increased. Other configurations are the same as those of the second specific example of FIG. According to the sixth specific example, since the inner surface protrusion 10 is configured so that the diameter of the lower portion is increased, the resistance when buried in the ground can be reduced, and the steel pipe pile 11 can be smoothly press-fitted.

  FIGS. 5A and 5B show seventh and eighth specific examples. Referring to FIG. 5 (a) in comparison with FIG. 2 (a), in FIG. 5 (a), the cross-sectional shape of the inner surface projection 10 provided on the inner surface of the pile body is such that the upper side is a large projection and the lower side has a larger diameter. An inner taper 10b is formed on the inner surface. Other configurations are the same as those of the first specific example of FIG. According to the seventh specific example, since the lower side of the inner surface protrusion 10 is configured to have a larger diameter, the resistance at the time of underground embedding can be reduced, and the steel pipe pile 11 can be smoothly press-fitted.

  The eighth example of FIG. 5B will be described in comparison with FIG. 2B. In FIG. 5B, the inner surface protrusion 10 provided on the inner surface of the pile body as in FIG. 5A. The inner surface taper 10b is formed so that the upper side has a large protrusion and the lower side has a larger diameter. Other configurations are the same as those of the second specific example of FIG. According to the eighth specific example, since the inner surface protrusion 10 is configured so that the diameter of the lower portion is increased, the resistance when buried in the ground can be reduced, and the steel pipe pile 11 can be smoothly press-fitted.

According to specific examples 1 to 8 in FIG. 2 to FIG. 5, in the tip structure of the steel pipe pile 11 applied to the intermediate excavation method, the pile head is formed by the high load transmission portion 12 composed of the pile tip projection 8 and the inner surface projection 10. The axial force from the part can be reliably transmitted to the tip root bulb 7. The pile tip protrusion 8 and the inner surface protrusion 10 can be configured using any means such as casting, forging, and welding with respect to the steel pipe body. Moreover, the steel pipe pile structure which concerns on this invention is applicable also to a pre-boring pile construction method, and it uses it by the meaning including the pre-boring pile construction method in a claim in a claim.

(A) is a schematic explanatory diagram of the structure of the tip of the steel pipe pile used in the intermediate excavation method as the foundation of the structure, (b) is a detailed view of part A in FIG. 1 (a), (c) is a diagram It is detail drawing which shows the modification of 1 (b). (A), (b) is a longitudinal cross-sectional explanatory drawing of the 1st, 2nd specific example of the front-end | tip part structure of a steel pipe pile. (A), (b) is a longitudinal cross-sectional explanatory drawing of the 3rd, 4th specific example of the front-end | tip part structure of a steel pipe pile. (A), (b) is a longitudinal cross-sectional explanatory drawing of the 5th, 6th specific example of the front-end | tip part structure of a steel pipe pile. (A), (b) is a longitudinal cross-sectional explanatory drawing of the 7th, 8th example of the front-end | tip part structure of a steel pipe pile. (A), (b), (c) is explanatory drawing which divides and shows a part of process of a digging method to 3 processes. (A), (b), FIG. 6 (b), It is explanatory drawing which divides and shows the construction process of the root-fixing bulb shown as a detailed view of (c) into two processes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel pipe pile 2 Support layer 3 Auger screw 4 Rooting range 5 Ground 6 Cement milk 7 Rooting bulb 7a Bulb upper part 8 Inner protrusion 8a Outer rectangular protrusion 8b Inner rectangular protrusion 8c Taper 10 Inner protrusion 10a Stepped part 10b Inner taper 11 Steel pipe pile
12 High load transmission part 13 Outer surface protrusion 14 Downward protrusion 14a Lower part rectangular protrusion part
14b Lower part taper protrusion

Claims (4)

In steel pipe piles, in which cement milk is injected into the pile tip that has reached the ground support layer by the Nakabori method, the roots of the steel pipe are provided in the circumferential direction, and the pile tip protrusions projecting in and out of the steel pipe are provided in the circumferential direction. One or more steel pipe inner surface protrusions extending in the circumferential direction are provided over the range where the upper part of the root consolidation bulb is provided from the top to the upper part, and the load is transmitted from the pile body to the root consolidation bulb by the pile tip protrusion and the inner surface protrusion. The tip structure of a steel pipe pile used for the digging method characterized by constituting a load transmission part. The tip structure of the steel pipe pile used for the inside digging method according to claim 1, wherein one or more outer surface protrusions are provided on the outer surface of the steel pipe pile corresponding to the inner surface protrusion. The tip structure of the steel pipe pile used for the intermediate digging method according to claim 1 or 2, wherein the pile tip protrusion has a downward projecting shape for earth pressure reduction at the time of pile embedding. The inside digging method according to any one of claims 1 to 3, wherein the inner surface protrusion has a rectangular cross-sectional shape perpendicular to the circumferential direction or a tapered or stepped shape having an enlarged diameter on the lower side. Tip structure of steel pipe pile used for

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