JP5975231B2 - Open-ended steel pipe pile and its construction method - Google Patents

Description

  The present invention relates to an open-end steel pipe pile and a construction method therefor, and more specifically, an open-end portion by a solidified body of a root-solidifying liquid inserted into a pile hole excavated in the ground in advance and filled in a bottom portion of the pile hole. It is related with the open-end steel pipe pile which is restrained and its construction method.

  A pile foundation using a steel pipe pile is known as a foundation of a structure. In general, steel pipe piles are used as driven piles, embedded piles or rotary press piles. As construction methods for steel piles of the driven pile method, a hammering method in which a steel pipe pile is driven into the ground by hammering with a hydraulic hammer, etc., and a vibration method in which the pile is installed in the ground while vibrating the pile body with a vibro hammer are known. ing. As a construction method of steel pipe piles of the embedded pile method, the excavation of the hollow part of the pile body while installing the steel pipe piles in the ground, the composite structure of soil cement and steel pipe piles created by the original ground and cement A steel pipe soil cement construction method is known. Moreover, the construction method of the steel pipe pile of a rotation press-fit pile method is the structure which utilized the high torsional strength of the steel pipe pile, and is a construction method in which the steel pipe which attached the blade | wing to the front-end | tip (lower end) is rotated and it penetrates into the ground.

  Steel pipe piles of the embedded pile method and rotary press-fit pile method can be constructed with low vibration and low noise, and the construction soil is relatively small, and it can be reused (recycled) by pulling it out from the ground. This is advantageous. However, the construction of the rotary press-in pile requires a special steel pipe with a tip blade and a special construction machine such as a rotary penetration machine. In addition, the medium excavation pile method and the steel pipe soil cement method are not only relatively difficult to manage, but also require a relatively large amount of work for soil disposal.

  In the pipe pile construction method using the embedded pile method, after drilling a pile hole in the ground and expanding the bottom of the pile hole, the steel pipe pile is inserted into the pile hole and the tip end support is secured. A method for injecting cement milk into the bottom of a pile to form an expanded bottom-solidified portion is described in JP-A-6-316927 (Patent Document 1), JP-A-2002-371548 (Patent Document 2), etc. Yes. In such a steel pipe pile construction method, construction management and soil removal treatment, etc. are relatively easy, and in addition, in this type of steel pipe pile, the bottom-solidified portion has a relatively large cross section, It may be possible to ensure a relatively large supporting force for supporting the vertical load by the expanded bottom solidified portion. Moreover, in the steel pipe pile described in patent documents 1 and 2, protrusion or a rib protrudes on the outer peripheral surface of the front-end | tip part of a steel pipe pile, and a protrusion or a rib is a cement lump and steel pipe pile front-end | tip part which comprise a rooting part. Increase the adhesion of The load of the ground structure or the like is transmitted from the pile tip to the cement lump portion located on the lower side of the pile tip portion, and is transmitted from the protrusions or ribs to the cement lump portion in the outer peripheral region of the steel pipe.

JP-A-6-316927 JP 2002-371548 A

  Since the construction method of the steel pipe pile of the embedded pile method described in patent documents 1 and 2 is a thing of the structure which substantially depended on formation of the bottom-end root consolidation part, the allowable supporting force of a steel pipe pile is such a construction method. However, in order to ensure the desired end clogging effect due to the widened root firming portion, it is necessary to reliably form a relatively large bottomed root solidified portion at the bottom of the pile. However, it is difficult to confirm the state or properties of the deepened root-solidified part formed in the ground easily after construction, and it is practically extremely accurate to grasp the support force etc. exhibited by the widened root-solidified part after construction. Have difficulty.

  On the other hand, when such a deepening root consolidation part is reduced or omitted, the effective cross-sectional area at the tip of the open-end steel pipe pile is relatively reduced compared to the effective cross-sectional area of the closed-end pile, so that the bearing capacity of the steel pipe pile is reduced. The problem of deteriorating arises.

The present invention has been made in view of such circumstances, and an object of the present invention is to make an effective use of the pile tip corresponding to the closed cross-sectional area of the tip of the steel pipe pile without forming the bottomed root solidified portion. It is providing the open end steel pipe pile which can ensure a cross-sectional area, and its construction method.

To achieve the above object, the present invention is pre-excavated in the ground, inserted into a pile hole having substantially the same pile hole diameter over the entire length, and filled with cement milk at the bottom of the pile hole as a rooting liquid. In the open-end steel pipe pile in which the open end portion of the steel pipe is constrained by the solidified liquid of the root hardening liquid,
The steel pipe constituting the open- end steel pipe pile has an outer diameter D in the range of 100 to 270 mm, and an annular tip member and a bottom spacer are integrally attached to the open end part thereof ,
The annular tip member has an annular steel plate fixed to the open end surface of the steel pipe so as to form an annular bottom surface orthogonal to the pile core of the steel pipe,
The outer peripheral edge of the steel plate protrudes radially outward from the outer peripheral surface of the steel pipe, and the inner peripheral edge of the steel plate protrudes radially inward from the inner peripheral surface of the steel pipe,
The outer peripheral edge of the steel sheet protrudes radially outward from the outer peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm, and the inner peripheral edge of the steel sheet has a predetermined dimension within a range of 10 to 60 mm. An annular zone projecting radially inward from the inner peripheral surface, perpendicular to the pile core and having a width set to a predetermined dimension within a range of 50 to 100 mm is formed on the bottom surface of the steel pipe by the steel plate,
The bottom spacer protrudes downward from the steel plate, and separates the bottom surface of the pile hole and the bottom surface of the steel plate by a distance of 100 to 300 mm ,
During the root hardened liquid injected into the bottom of the pile hole during drilling, it is filled from an opening portion of the steel sheet during sinking of the pile into the distal end portion of the steel pipe Tei Rutotomoni, and the steel sheet and the Kuiana bottom during sinking of the pile and it is filled between the outer peripheral surface and Kuiana the pore walls of the steel pipe,
The open end of the steel pipe pile by solidification of the root solidified liquid is restrained, the effective cross-sectional area Ap of the pile tip is provided an open end steel pipe, characterized in that it is set to [pi] D ^2/4.

According to the said structure of this invention, the cyclic | annular collar or expansion bottom board extended in the radial direction outward and radial direction inward of an open end part is formed in the open end part of a steel pipe pile by the said annular steel plate. The annular steel plate not only improves the fixability between the solidified liquid of the root hardening liquid and the open end portion of the steel pipe pile, but also expands the width of the end face of the open end portion and improves the tip support force of the steel pipe pile. According to experiments by the present inventors, when a steel pipe having such a structure, irrespective of whether or not to form a拡底roots consolidated unit, [pi] D ^2/4 of the effective cross-sectional area Ap of the pile tip, i.e. It was found that it can be set equal to the closed cross-sectional area of the tip of the steel pipe pile.

The present invention is also a construction method of an open end steel pipe pile using the steel pipe pile having the above-described configuration,
Inserting the steel pipe pile having an outer diameter D in advance drilled pile hole in the ground, the open ends of the steel pipe pile is restrained by the solid material of the root hardened liquid, the effective cross-sectional area Ap of the pile tip [pi] D ^2/4 Provided is a construction method of an open-ended steel pipe pile characterized by being set.

The present invention further provides an open end in which an open end steel pipe pile having an outer diameter D is set in a pile hole previously excavated in the ground, and the open end portion of the steel pipe pile is constrained by a solidified liquid of a root-solidified liquid filled in the bottom of the pile hole. In the construction method of steel pipe piles,
Excavating a pile hole having substantially the same pile hole diameter over the entire length in the ground, and injecting cement milk as a root hardening liquid into the bottom of the pile hole;
A steel pipe pile with an annular steel plate fixed to the open end surface of the steel pipe is inserted into the pile hole so as to form an annular bottom surface orthogonal to the pile core of the steel pipe pile, and the steel pipe pile is opened from the opening formed at the center of the steel plate. Filling the root-setting liquid into the tip, and filling the root-setting liquid between the steel plate and the pile hole bottom surface and between the outer peripheral surface of the steel pipe and the pile hole wall;
A step of constraining the open end portion of the steel pipe pile by the solidified body of the root-setting liquid by hardening the root-setting liquid,
The open end, in order to set the effective sectional area Ap of the pile tip as [pi] D ^2/4, of the inner peripheral edge steel pipe projecting and the steel plate outer peripheral edge portion from the outer peripheral surface of the steel pipe radially outward of the steel plate It has a structure that protrudes radially inward from the inner peripheral surface,
The outer diameter D of the steel pipe is set to a predetermined dimension within a range of 100 to 270 mm, and the outer peripheral edge of the steel plate protrudes radially outward from the outer peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm. The inner peripheral edge of the steel plate protrudes radially inward from the inner peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm, and is set to a predetermined dimension within a range of 50 to 100 mm perpendicular to the pile core. An annular zone having a width is formed on the bottom surface of the steel pipe by the steel plate,
Provided is a method for constructing an open-ended steel pipe pile, characterized in that a bottom spacer attached to the steel plate and projecting downward from the steel plate separates the bottom surface of the pile hole and the steel plate by a distance of 100 to 300 mm .

  According to the construction method having the above-described configuration, the bottom of the pile hole is not formed, and a pile hole having substantially the same pile hole diameter over the entire length is excavated in the ground. The effective cross-sectional area of the pile tip corresponding to the closed cross-sectional area can be ensured.

According to the above configuration of the present invention, an open-end steel pipe pile that can secure an effective cross-sectional area of a pile tip corresponding to a closed cross-sectional area of a tip part of a steel pipe pile without forming a bottom-floored solidified part and a construction method thereof Can be provided.

  Further, according to the construction method of the present invention using such an open-end steel pipe pile and excavating a pile hole having substantially the same pile hole diameter over the entire length in the ground, the range in which the original ground is disturbed during construction is Since it is limited to the range corresponding to the outer diameter of the excavating device, etc., it is possible to surely prevent the collapse of the pile hole wall and to sufficiently ensure the peripheral frictional force around the pile.

FIG. 1 (A) and FIG. 1 (B) are a longitudinal sectional view and a bottom view showing a tip portion of an open end steel pipe pile according to the present invention. 2A is a longitudinal cross-sectional view of the open-end steel pipe pile shown in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line II in FIG. 2A. FIG. 3 is a perspective view conceptually showing the relationship between the tip of the open-end steel pipe pile and the bottom of the pile hole. FIG. 4 is a longitudinal sectional view schematically showing a construction method of an open end steel pipe pile, and a process of excavating a pile hole for inserting the open end steel pipe pile is shown in FIG. FIG. 5: is a longitudinal cross-sectional view which shows the construction method of an open end steel pipe pile roughly, and the process of building an open end steel pipe pile in a pile hole is shown. FIG. 6 (A) is a longitudinal sectional view showing a state in which the tip of the open-end steel pipe pile is embedded in the solidified liquid of the root hardening liquid at the bottom of the pile hole, and FIG. 6 (B) is a view of FIG. 6 (A). It is sectional drawing in the II-II line.

  In a preferred embodiment of the present invention, the annular tip member has a short pipe disposed in the steel pipe and fixed to the upper surface of the steel plate. The short pipe can be used as positioning means for reinforcing the steel plate and positioning the steel plate at the open end when the steel plate is fixed to the open end.

If desired , a side spacer for separating the outer peripheral surface of the steel pipe and the hole wall of the pile hole is attached to the outer peripheral surface of the steel pipe.

Suitably, the diameter of the said pile hole is set to the dimension larger 100-300 mm than the outer diameter of the said steel pipe. Preferably, the level difference between the upper surface of the support layer of the ground and the steel plate is set to the same dimension as the outer diameter dimension of the steel pipe or a dimension greater than or equal to the outer diameter dimension of the steel pipe . The filling height of the root-setting liquid is set to 400 to 1000 mm, for example, 500 mm, and the liquid level of the root-setting liquid is set to a position higher than the upper surface of the support layer by 100 mm or more.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a longitudinal sectional view and a bottom view showing a tip portion of an open-end steel pipe pile according to the present invention, and FIG. 2 is a longitudinal sectional view and a sectional view taken along line II of the open-end steel pipe pile shown in FIG. FIG. 3 is a perspective view conceptually showing the relationship between the tip of the open-end steel pipe pile and the bottom of the pile hole.

  The structure of the front-end | tip part of the open end steel pipe pile 1 is shown by FIG.1 and FIG.2. The open end steel pipe pile 1 has a structure in which an annular tip member 10 is fixed to the open end portion 3 of the steel pipe 2. The open-end steel pipe pile 1 has a true circular cross section with a pile diameter (outer diameter) D. The pile diameter D is set to 100 to 500 mm, for example, about 270 mm. The pipe wall of the steel pipe 2 has a thickness of 5 to 10 mm, for example, about 7 mm. On the outer peripheral surface of the steel pipe 2, when inserting the open end steel pipe pile 1 into the pile hole, a side spacer 4 (roughly indicated by a one-dot chain line) for reliably separating the pile hole wall and the outer peripheral surface of the open end steel pipe pile 1 is provided. 1) is attached.

  The annular tip member 10 includes a steel plate 11 having a thickness t fixed to the open end 3 by welding means or the like, a short pipe 12 fixed to the upper surface of the steel plate 11 by welding means or the like, and a lower surface of the steel plate 11 by welding means or the like. And a bottom spacer 20 (schematically shown in FIG. 1 by a one-dot chain line). The upper surface and the lower surface of the steel plate 11 are arranged in a horizontal plane orthogonal to the central axis C of the steel pipe 2. The plate thickness t of the steel plate 11 is set to 5 to 30 mm, for example, 9 mm.

  The steel plate 11 has a true circular outer edge 13 and a true circular inner edge 14 having diameters d1 and d2 around the central axis C, and a circular opening 15 is formed in the central portion of the steel plate 11. The steel plate 11 protrudes from the outer peripheral surface of the steel pipe 2 radially outward by a distance d3 = (d1−D) / 2, and the distance d4≈ (D−d2) from the inner peripheral surface of the steel plate 2 radially inward. Projects by / 2. An annular zone having a width W = d1-d2 orthogonal to the central axis C is formed on the bottom surface of the open-end steel pipe pile 1 by the steel plate 11. The width W is set to 50 to 100 mm, for example, about 70 mm, the distance d3 is set to a range of 10 to 60 mm, for example, about 25 mm, and the distance d4 is set to a range of 10 to 60 mm, for example, about 35 mm. Is done.

Short pipe 12 ing from steel pipe of a true circular cross section arranged in a circular opening 15 coaxially. The tube wall of the short tube 12 has a thickness of 5 to 10 mm, for example about 6 mm. The total length (overall height) of the short tube 12 is set to 30 to 100 mm, for example, about 50 mm. The short pipe 12 has an outer diameter slightly smaller than the inner diameter of the steel pipe 2, for example, an outer diameter of about 240 mm. The short pipe 12 reinforces the steel plate 11 and is used as a positioning means for positioning the steel plate 11 to the open end 3 when the steel plate 11 is fixed to the open end 3.

  The bottom spacer 20 is fixed to the lower surface of the steel plate 11 with an angular interval of 120 degrees around the central axis C. Each spacer 20 is made of, for example, a steel piece obtained by cutting a shape steel such as a groove shape or a C-shaped cross section, and the height h of each spacer 20 is set to 50 to 300 mm, for example, 100 mm. The spacer 20 functions to reliably separate the bottom surface of the pile hole and the steel plate 11 when the open-end steel pipe pile 1 is inserted into the pile hole.

  As shown in FIG. 3, the tip end portion of the open-end steel pipe pile 1 is set on the pile bottom portion Bc of the pile hole B into which the root hardening liquid M has been injected. Preferably, as the root hardening liquid M, cement milk prepared by mixing an appropriate amount of water with cement is used. The pile hole B has a uniform diameter R over its entire length, the outer peripheral surface of the steel pipe 2 is spaced apart from the hole wall Ba of the pile hole B by a distance R1, and the outer edge 13 of the steel plate 11 is a pile hole wall. It is separated from Ba by an interval R2. The diameter R is set to 200 to 800 mm, for example, 400 mm, the interval R1 is set to 40 to 160 mm, for example, about 70 mm, and the interval R2 is set to 30 to 100 mm, for example, about 40 mm.

The lower surface of the steel plate 11 is positioned at a distance from the pile hole bottom surface Bb of the pile hole B by a distance corresponding to the height h of the bottom spacer 20. Between the steel plate 11 and the bottom hole Bb of the pile hole, the root-solidifying liquid M is filled, and the root-solidifying liquid M is also present between the outer peripheral surface of the steel pipe 2 located on the upper side of the steel plate 11 and the pile hole wall Ba. Filled. When the root hardening liquid M is solidified, a hardened lump of the root hardening liquid is formed between the steel plate 11 and the supporting ground. Accordingly, the axial force acting vertically downward on the open-end steel pipe pile 1 is transmitted from the lower surface of the steel plate 11 to the supporting ground via the hardened mass of the root hardening liquid M. As will be described later, in the open end steel pipe pile 1 having such annular tip member 10, the effective cross-sectional area Ap of the pile tip [pi] D ^2/4, i.e., can be set equal to the closure sectional area of the pile tip .

  4 and 5 are longitudinal sectional views schematically showing a construction method of the open-end steel pipe pile 1.

  The ground which should construct the pile foundation using the open end steel pipe pile 1 is shown by FIG. As shown in FIGS. 4 (A) and 4 (B), the pile hole B is excavated so that the tip of the open-end steel pipe pile 1 reaches the support layer SL of the ground. The excavation process is carried out by positioning the tip bit of the earth auger 51 at the pile core position on the ground surface GL and rotating the screw portion of the earth auger 51 to drill the ground. During excavation, the earth auger 51 ejects drilling fluid from the tip of the auger to prevent the pile hole wall Ba from collapsing, and after the tip of the auger reaches a predetermined depth, the ground auger 51 is replaced with the drilling fluid. ) From the auger tip. The depth of the pile hole bottom surface Bb is set to a depth deeper than the upper surface of the support layer SL by at least the pile diameter D + 100 mm, for example, a depth of 400 mm below the upper surface of the support layer SL.

  As shown in FIG. 4C, the earth auger 51 is pulled up while injecting a predetermined amount of the root-setting liquid M into the pile bottom Bc and then flowing out the peripheral fixing liquid E in place of the root-setting liquid M. The injection height H of the root hardening liquid M is set to 400 to 1000 mm, for example, 500 mm. Preferably, the injection height H is set so that the upper surface of the root hardening liquid M is positioned at least 100 mm above the upper surface of the support layer SL.

  If the pile hole B which inject | poured the root hardening liquid C into the pile bottom part is formed in this way, the pile construction process shown in FIG. 5 will be implemented. As shown in FIG. 5 (A) and FIG. 5 (B), the pile erection process lifts up an open-end steel pipe pile 1 having a total length of about 6 mm and inserts it into the pile hole B, and the second and subsequent steel pipes 5 are sequentially welded. It is carried out by adding and inserting the open-end steel pipe pile 1 into the pile hole B while rotating as a whole. The open-end steel pipe pile 1 is inserted into the pile hole B until the spacer 20 reaches the bottom of the pile hole as shown in FIG. The root-setting liquid M flows from the circular opening 15 of the annular tip member 10 into the tip of the open-end steel pipe pile 1, and the tip of the open-end steel pipe pile 1 including the annular tip member 10 is embedded in the root-setting liquid M. To do. In order to ensure that the tip of the open-end steel pipe pile 1 is firmly rooted in the liquid M, if desired, a load is applied to the open-end steel pipe pile 1 transiently or temporarily in the final stage of the pile building process. The steel pipe pile 1 may be transiently or temporarily rotationally press-fitted. If the root hardening liquid M hardens | cures after predetermined time progress and expresses the expected intensity | strength, the front-end | tip outer periphery part of the open end steel pipe pile 1 will be restrained by the solidified body K of the root hardening liquid M.

  FIG. 6 is a longitudinal sectional view and a sectional view taken along the line II-II showing a state in which the distal end portion of the open-end steel pipe pile 1 is embedded in the solidified body K of the root hardening liquid M.

  As shown in FIG. 6, the diameter of the solidified body K is substantially the same as the diameter R of the pile hole B. Therefore, the open-end steel pipe pile 1 does not include an expanded bottom consolidation part and corresponds to the pile hole diameter R. It only has a root of diameter. A vertically downward axial force P acting on the open-end steel pipe pile 1 is transmitted from the pipe wall end face of the open-end steel pipe pile 1 to the annular tip member 10, and is transmitted to the solidified body K portion directly below the steel plate 11, thereby supporting layer SL. Supported by the ground.

In general, the long-term allowable bearing capacity Ra of the ground in this type of pile foundation is obtained by the following equation.
Ra = 1/3 {α · N · Ap + (β · Ns · Ls + γ · qu · Lc) · φ} (kN)
α: Bearing coefficient of pile tip β: Friction coefficient of pile surface friction in sandy ground γ: Friction coefficient of pile surface friction in clayey ground N: Average N value of pile tip ground
Ap: Effective cross-sectional area of the pile tip (m ² )
Ns: Average N value of sandy ground around piles
qu: Average uniaxial compressive strength of clayey ground around piles (kN / m ² )
Ls: Effective length in contact with sandy ground around the pile (m)
Lc: Effective length in contact with the clay ground around the pile (m)
φ: Perimeter of pile (m)

According to the experiments by the present inventors, in the pile foundation using the open-end steel pipe pile 1 having the above-described configuration, the tip end portion of the open-end steel pipe pile 1 is used as the effective sectional area Ap of the pile tip for obtaining the long-term allowable bearing capacity Ra closed cross section, i.e., it has been found that may be employed Ap = πD ^2/4. This means that regardless of whether to form a拡底roots hardened portion, the effective cross-sectional area Ap of the pile tip [pi] D ^2/4, i.e., can be set as the closed cross-sectional area of the pile tip.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. It goes without saying that it is possible.

  For example, in the above embodiment, the root-setting liquid is filled only in the bottom of the pile hole. However, the root-solidifying liquid may be filled up to a higher level, and an additional bottom portion by the root-solidifying liquid is added. You may form in.

  Moreover, in the said Example, although the spacer is provided in the side surface and bottom face of the steel pipe pile, this kind of spacer can also be abbreviate | omitted.

  Furthermore, in the above embodiment, the annular tip member has a configuration in which a short tube is fixed to the upper side of the annular steel plate. However, the annular steel plate is positioned at the tip of the steel tube using means such as a stiffener instead of the short tube, and is annular. A steel plate may be reinforced.

  In addition, the outline of the opening of the annular tip member is not limited to a circle, but a square, ellipse or the like is adopted, or a reinforcing member that crosses or partially closes the opening, or a linear member. Etc. may be constructed or stretched on the opening.

The present invention is applied to an open-end steel pipe pile that is inserted into a pile hole that has been excavated in the ground in advance and whose open end portion is constrained by a solidified body of a root hardening liquid that is filled in the bottom of the pile hole, and a construction method thereof. According to the open-end steel pipe pile of the present invention and the construction method thereof, an effective cross-sectional area of the pile tip corresponding to the closed cross-sectional area of the pile tip portion can be ensured without forming a bottom-widened solidified portion. The effect is remarkable.

DESCRIPTION OF SYMBOLS 1 Open end steel pipe pile 2 Steel pipe 3 Open end part 4 Side spacer 10 Annular tip member 11 Annular steel plate 12 Short pipe 13 True circular outer edge 14 True circular inner edge 15 Circular opening 20 Bottom spacer B Pile hole Ba Pile hole wall Bb Pile hole bottom face Bc Pile bottom D Pile diameter M Root-solidifying liquid K Solidified body GL Ground surface SL Support layer

Claims (7)

The steel pipe is preliminarily excavated in the ground, inserted into a pile hole having substantially the same pile hole diameter over its entire length, and filled with cement milk as a root hardening liquid at the bottom of the pile hole. In the open-end steel pipe pile that is restrained the open end of
The steel pipe constituting the open- end steel pipe pile has an outer diameter D in the range of 100 to 270 mm, and an annular tip member and a bottom spacer are integrally attached to the open end part thereof ,
The annular tip member has an annular steel plate fixed to the open end surface of the steel pipe so as to form an annular bottom surface orthogonal to the pile core of the steel pipe,
The outer peripheral edge of the steel plate protrudes radially outward from the outer peripheral surface of the steel pipe, and the inner peripheral edge of the steel plate protrudes radially inward from the inner peripheral surface of the steel pipe,
The outer peripheral edge of the steel sheet protrudes radially outward from the outer peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm, and the inner peripheral edge of the steel sheet has a predetermined dimension within a range of 10 to 60 mm. An annular zone projecting radially inward from the inner peripheral surface, perpendicular to the pile core and having a width set to a predetermined dimension within a range of 50 to 100 mm is formed on the bottom surface of the steel pipe by the steel plate,
The bottom spacer protrudes downward from the steel plate, and separates the bottom surface of the pile hole and the bottom surface of the steel plate by a distance of 100 to 300 mm ,
During the root hardened liquid injected into the bottom of the pile hole during drilling, it is filled from an opening portion of the steel sheet during sinking of the pile into the distal end portion of the steel pipe Tei Rutotomoni, and the steel sheet and the Kuiana bottom during sinking of the pile and it is filled between the outer peripheral surface and Kuiana the pore walls of the steel pipe,
The root open end of the solidified liquid steel pipe pile by solid material is restrained, the open steel pipe piles effective area Ap of the pile tip is characterized in that it is set to [pi] D ^2/4.   The open-ended steel pipe pile according to claim 1, wherein the annular tip member has a short pipe disposed in the steel pipe and fixed to the upper surface of the steel plate. The filling height of the root-setting liquid is set to 400 to 1000 mm, and the liquid level of the root-setting liquid is set to a position higher than the upper surface of the support layer by 100 mm or more. The open end steel pipe pile according to 2. A method for constructing an open end steel pipe pile in which an open end steel pipe pile having an outer diameter D is set in a pile hole excavated in the ground, and the open end portion of the steel pipe pile is constrained by a solidified liquid of a root-solidified liquid filled in the bottom of the pile hole In
Excavating a pile hole having substantially the same pile hole diameter over the entire length in the ground, and injecting cement milk as a root hardening liquid into the bottom of the pile hole;
A steel pipe pile with an annular steel plate fixed to the open end surface of the steel pipe is inserted into the pile hole so as to form an annular bottom surface orthogonal to the pile core of the steel pipe pile, and the steel pipe pile is opened from the opening formed at the center of the steel plate. Filling the root-setting liquid into the tip, and filling the root-setting liquid between the steel plate and the pile hole bottom surface and between the outer peripheral surface of the steel pipe and the pile hole wall;
A step of constraining the open end portion of the steel pipe pile by the solidified body of the root-setting liquid by hardening the root-setting liquid,
The open end, in order to set the effective sectional area Ap of the pile tip as [pi] D ^2/4, of the inner peripheral edge steel pipe projecting and the steel plate outer peripheral edge portion from the outer peripheral surface of the steel pipe radially outward of the steel plate It has a structure that protrudes radially inward from the inner peripheral surface,
The outer diameter D of the steel pipe is set to a predetermined dimension within a range of 100 to 270 mm, and the outer peripheral edge of the steel plate protrudes radially outward from the outer peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm. The inner peripheral edge of the steel plate protrudes radially inward from the inner peripheral surface of the steel pipe by a predetermined dimension within a range of 10 to 60 mm, and is set to a predetermined dimension within a range of 50 to 100 mm perpendicular to the pile core. An annular zone having a width is formed on the bottom surface of the steel pipe by the steel plate,
A construction method for an open-ended steel pipe pile , wherein the bottom surface of the pile hole and the steel plate are separated by a distance of 100 to 300 mm by a bottom spacer attached to the steel plate and projecting downward from the steel plate . The construction method according to claim 4 , wherein side spacers protruding laterally are attached to an outer peripheral surface of the steel pipe pile, and a hole wall of the pile hole and an outer peripheral surface of the steel pipe pile are separated. Filling height of the root firm liquid is set to 400～1000Mm, the liquid surface of the root firm solution, according to claim 4 or 5 is set to 100mm or more higher than the upper surface of the support layer, characterized in Rukoto The construction method described in 1. It is the construction method of the open end steel pipe pile using the steel pipe pile described in Claim 1 thru | or 3 ,
Inserting the steel pipe pile having an outer diameter D in advance drilled pile hole in the ground, the open ends of the steel pipe pile is restrained by the solid material of the root hardened liquid, the effective cross-sectional area Ap of the pile tip [pi] D ^2/4 A construction method of an open end steel pipe pile characterized by being set.

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