JP5499335B2 - Steel pipe pile and support structure and construction method using the steel pipe pile - Google Patents

Description

  The present invention relates to a steel pipe pile and a support structure and construction method for a steel pipe pile that penetrates the steel pipe pile, and particularly relates to a steel pipe pile having a high tip support force and good workability, and its support structure and construction method. .

As a structure of a foundation pile used for a foundation of a structure or the like, Patent Document 1 proposes a construction method for embedding a steel pipe pile by an action as a wood screw of a wing attached to the outer periphery of the tip of the steel pipe pile. This construction method for foundation piles is generally referred to as an underground excavation rotary penetration method.
As shown in FIG. 12, this foundation pile construction method is a construction method in which the pile body 10 and the auger head 22 are rotated in opposite directions by the double auger rotation motor 32 and penetrated into the ground. During the rotation of the pile body 10, the support layer or a desired section including the support layer is ejected from the auger head 22 from the auger head 22 (solidifying liquid such as cement milk), and the blade 10A and the auger head 22 are ejected. By stirring and mixing the earth and sand and the curable fluid 23, after the stirring and mixing to a predetermined depth, the auger 20 is withdrawn leaving the pile, and the softened earth and sand is solidified over time. is there.

In FIG. 12, reference numeral 41 denotes a hose, and the hose 41 communicates with a through hole 21 provided in the auger 20. 70 is a mixture of earth and sand and curable fluid 23 (solidifying liquid such as cement milk), and the solidified root hardening column and the pile body 10 are integrated.
However, in order to obtain the tip support force required as a foundation pile, a steel pipe pile with a wing having a diameter of about 1.5 to 2 times the pile diameter is attached to the outer periphery of the pile tip. There is a disadvantage that the processing cost to be attached to 10 becomes high and the cost of the foundation pile is inevitably increased. In addition, a steel pipe pile with a large area wing 10A attached to the outer periphery of the tip of the pile will cause stress concentration at the joint between the wing 10A and the pile body 10. It tends to be a weak spot.

In addition, steel pipe piles with a large area of wing 10A attached to the outer periphery of the tip of the pile are particularly hard when ground is rotated into the ground by the wood screw action of the wing 10A provided at the tip of the pile body 10. There is a problem that the penetration resistance is large and the workability is inferior.
In addition, as a foundation pile, Patent Document 2 describes a steel pipe pile in which a spiral protrusion having a height of 20 mm or less is provided on the outer periphery of the pile.

  When this steel pipe pile is used and penetrated by a drill rotary penetration method to make a foundation pile, when the pile diameter is 600mm or less, the tip support force is reduced by the soil closure lid generated at the tip of the pile when rotating. Although it is expressed, the cross-sectional area of the closing lid and the closing area of the pile are the same, and there is a problem that the tip support force at the tip of the pile is insufficient, but if the pile diameter exceeds 600 mm, the tip closing There was a problem that the effect was reduced and the tip supporting force was insufficient.

  Furthermore, as the structure of the foundation pile used for the foundation of the structure, etc., if the support capacity at the tip of the pile is further improved, the effect of reducing the number of piles buried per ground area can be expected. There is a strong demand for further improvement.

Japanese Unexamined Patent Publication No. 2000-144728 Japanese Patent No. 2512503

  An object of the present invention is to provide a steel pipe pile capable of obtaining a high tip support force and a support structure thereof without providing a large wing, and to provide a steel pipe pile construction method capable of easily constructing the support structure. And

The present inventors have been intensive studies, 10% of the height of 6mm or more and the steel pipe pile diameter D ₁ at the tip outer periphery less, the ratio P / t of the pitch P is winding at 7.7 to 33 angle θ is 45 The present invention has been completed based on the knowledge that the above problems can be solved by using a steel pipe pile provided with projections of less than or equal to °.
That is, the present invention is as follows.

1. A steel pipe pile penetrating into a solidified column, wherein the height t is 6 mm or more and 10% or less of the steel pipe pile diameter D _{1 at} the outer periphery of the tip of the steel pipe pile, and the ratio P / t with the pitch P is 7.7 to 33 wrap angle θ is have a helical projection of 45 ° or less, the bonding strength between the protrusion and the steel pipe pile is greater than tau _c × p against splitting strength tau _c of concrete forming the root compaction column A steel pipe pile characterized by that.
2. The steel pipe pile according to 1 above, wherein the spiral protrusion is provided in 1 to 6 stages.
3. The steel pipe pile according to 1 or 2 above, and a solidified column formed in a support layer in the ground or a section including the support layer and embedded with a spiral protrusion provided on an outer periphery of a tip portion of the steel pipe pile And a excavation hole that is excavated in the ground and is in contact with the portion excluding the tip of the steel pipe pile, either directly or via fixed soil.

4). Wherein 1-5 times the height H of the steel pipe pile diameter D ₁ of the root firm pillar, the diameter D ₂ and 1.2 to 2.0 times the steel pipe pile diameter D _1, the distal end portion of the steel pipe pile at the root compaction in column 4. The steel pipe pile support structure according to 3 above, wherein the insertion length S is 0.6 to 0.9 times the height H.
5. An auger is inserted into the hollow portion of the steel pipe pile described in 1 or 2 above, and the ground is excavated by the auger and the steel pipe pile is rotated and penetrated to construct a solidified column including the support layer or the support layer in the ground. When the auger head reaches the section where the auger head reaches, the excavating diameter of the auger head is expanded to be equivalent to the diameter of the consolidation column and excavated by the height of the consolidation column, and the solidified liquid is ejected from the auger head, The steel pipe pile is rotated and penetrated into the root hardening column, and after the rotation penetration is finished, the auger is pulled out leaving the tip of the steel pipe pile at the root hardening column, and the solidified liquid is solidified. Steel pipe pile construction method.

  6). Prior to penetrating the steel pipe pile described in 1 or 2 above, when the auger head reaches a section in which the ground is excavated by an auger and a solidified column including the supporting layer or the supporting layer is constructed in the ground. The excavation diameter of the auger head is expanded to be equivalent to the diameter of the consolidation column, and the solidification liquid is ejected from the auger head after excavation by the height of the consolidation column. A method for constructing a steel pipe pile, characterized in that a drilling hole excavated by the auger and the root hardening column are rotationally inserted to embed the tip of the steel pipe pile in the root hardening column and further solidify the solidified liquid.

7). Wherein 1-5 times the height H of the steel pipe pile diameter D ₁ of the root firm pillar, the diameter D ₂ and 1.2 to 2.0 times the steel pipe pile diameter D _1, the distal end portion of the steel pipe pile at the root compaction in column The construction method of the steel pipe pile according to 5 or 6, wherein the insertion length S is 0.6 to 0.9 times the height H.
8). The construction method of a steel pipe pile according to any one of 5 to 7 above, wherein the auger head has a wing expansion mechanism, and the root pillar is excavated by expanding the auger head. .

  9. The auger head has a high-pressure injection mechanism capable of injecting the solidified liquid, and excavating the root hardening column by injecting the solidified liquid at a high pressure from the auger head. The construction method of the steel pipe pile as described in one.

  According to the steel pipe pile support structure of the present invention, the steel pipe pile provided with protrusions at the tip and the root hardening column are integrated, and a high tip support force is obtained. Moreover, according to the construction method of the steel pipe pile of this invention, the construction of the steel pipe pile which has a high tip support force is attained, ensuring favorable workability. Furthermore, a sufficient peripheral friction force with the surrounding ground can be secured.

(A) is a longitudinal cross-sectional schematic diagram which shows the structure of the steel pipe pile of this invention, (b) is XX sectional drawing of FIG. It is principal part sectional drawing of the steel pipe pile used for this invention, (a), (b), (c), and (d) differ in a projection member. It is a schematic diagram which shows propagation | transmission of the force with respect to a solidification pillar, (a) shows the case where a protrusion is in a steel pipe pile front-end | tip (this invention), (b) shows the case where there is no protrusion in a steel pipe pile front-end | tip. It is a mimetic diagram showing propagation of force to a solidification pillar. It is a mimetic diagram showing propagation of force to a solidification pillar. It is explanatory drawing which shows the construction method of the foundation pile which concerns on the 1st Embodiment of this invention. It is principal part sectional drawing which shows the auger used for the construction method of this invention, (a) and (b) differ in the shape of the stirring member of an auger. It is a schematic sectional drawing which shows a double auger rotary motor. It is a schematic sectional drawing which shows the rotation motor which rotates a pile and an auger, respectively. It is explanatory drawing which shows the construction method of the foundation pile which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the other auger example used for this invention. It is explanatory drawing which shows the construction method of the conventional foundation pile, (a) is a state in the initial stage of penetration, (b) is a state in which the tip of the pile body has reached a desired depth in the support layer, and (c) is pulling up the auger It is in the state. It is a perspective view which shows the shape of the wing | blade attached to the front-end | tip part of the conventional steel pipe pile. It is a graph which shows the effect of the foundation pile of the present invention. It is principal part sectional drawing explaining the front-end | tip support effect in the foundation pile of this invention.

First, the structure of the foundation pile of this invention is demonstrated in detail using figures.
Fig.1 (a) is a longitudinal cross-sectional schematic diagram which shows the structure of the foundation pile of this invention, FIG.1 (b) is XX sectional drawing of FIG.
In FIG. 1, reference numeral 1 is a steel pipe pile (hereinafter also simply referred to as a pile), and 11A is a protrusion provided on the outer periphery of the tip of the steel pipe pile 1. Reference numeral 2 denotes a root consolidation column. In this case, the root consolidation column 2 is formed in the support layer, and the tip of the steel pipe pile 1 is inserted into the root consolidation column 2, and the root consolidation column 2 and the steel pipe pile are inserted. 1 tip portion is integrated. In the figure, 3 is the ground, 3A is the upper end of the support layer, and 3B is the ground surface. D ₁ is the pile diameter, D ₂ is the diameter of the consolidation column, S is the insertion length of the pile tip in the consolidation column, and H is the height of the consolidation column. D _t is D _t = D ₁ + 2 × t (see FIG. 2), where _t is the diameter of the tip of the pile including the protrusion, that is, the protrusion height.

  Moreover, FIG. 2 is principal part sectional drawing of the steel pipe pile used for this invention, In FIG. 2, a projection member differs in FIG. 2 (a), (b), (c). That is, 11A, 11B, and 11C are a round bar, a square bar, and a triangular bar, respectively, and these projecting members are spirally wound around the outer periphery of the tip end portion of the steel pipe pile 1 and fixed. Moreover, FIG.2 (d) showed the steel pipe pile 1 which made the round bar 11D wind circularly around the front-end | tip part outer periphery, and was fixed. θ is the protrusion winding angle between the winding direction of the protruding member and the circumferential direction of the pile, and L is the length from the tip of the pile provided with the protrusion. In addition, the slip stopper for hold | maintaining front-end | tip obstruction | occlusion is attached to a steel pipe inner surface like a general digging deepening pile.

In this invention, the support structure of the foundation pile which uses the steel pipe pile 1 which provided the processus | protrusion with a height of 6 mm or more on the outer periphery of the front-end | tip part, and the front-end | tip part of this steel pipe pile 1 is inserted in the consolidation column and integrated. It is the feature.
Hereinafter, 11 is a generic name of protrusions having a height of 6 mm or more provided on the outer periphery of the tip of the steel pipe pile 1. In addition, it is preferable that the height t of the protrusion 11 provided on the steel pipe pile 1 used in the present invention is 10% or less of the pile diameter D ₁ from the viewpoint of construction described later. In the present invention, the member forming the protrusion 11 is not particularly limited, and may be a plate material or the like. However, compared to the plate material, it is easier to process the round bar or square bar into a spiral or ring shape, and it is easier to attach to the steel pipe pile, so the processing cost is relatively low. Have advantages. In the present invention, the protrusion 11 can be intermittently provided in the circumferential direction of the steel pipe pile (like a screw of a ship or the like). However, in consideration of rotating the pile into the ground during construction, the protrusion is spiral. It is preferable that it is attached to the shape. In order to fix the protrusion 11 on the outer periphery of the tip of the steel pipe pile 1, the steel pipe pile and the protrusion can be integrally formed by rolling or casting in addition to welding. The strength of the joint between the steel pipe pile 1 and the projection 11 fixed in this way is the breaking strength at which the consolidation column between the projections 11 breaks due to compression (that is, the compression strength that is the strength of the concrete forming the consolidation column). Σ _c , or τ _c × p when the splitting strength is τ _c (see FIG. 15B)) is preferable in order to ensure the effect of improving the tip support force by providing the protrusions. .

In the present invention, as described above, the height of the protrusion 11 provided on the outer periphery of the tip of the steel pipe pile 1 is 6 mm or more, and the root hardening column 2 is larger than the diameter D _{t of the} steel pipe pile including the height of the protrusion 11. It has a larger diameter D _2, as shown in FIG. 1 (a), (b) , is inserted pile tip to root compaction column 2, roots consolidate pillar 2 as pile tip can not be pulled out from the roots compaction column Since the steel pipe pile 1 has a support structure in which the tip portion is integrated, a high tip support force can be obtained.

  The principle that a high tip support force can be obtained by the support structure of the present invention can be explained as follows. In the present invention, since the protrusions 11 are provided on the outer periphery of the pile front end portion, as shown in FIG. 3A, downward force F acting on the piles is applied to a large number of locations of the consolidation column 2 by the protrusions 11. Further, the force propagates in the radial direction of the root hardening column 2 (broken arrows in FIG. 3 (a)), so that cracking of the root hardening column 2 is less likely to occur, while FIG. 3 (b). As shown in Fig. 3, when there is no protrusion at the tip of the steel pipe pile 1, force propagates only to the lower end of the pile (broken line arrow in Fig. 3 (b)), and stress concentration occurs at the lower end of the pile. Cracks are likely to occur with the same force F as above.

  Thus, in the present invention, since the downward force acting on the pile is dispersed by the protrusion 11 completely embedded in the consolidation column, a large force is applied to the pile tip without increasing the height of the protrusion 11 so much. Supportive power is developed. At that time, if the protrusion 11 provided on the outer peripheral surface of the pile tip is too small, earth or sand adheres to the recess of the protrusion, or wear of the protrusion convex due to friction with the ground at the time of rotation penetration or corrosion of the protrusion convex When the height of the protrusion is lowered, there is a fear that the effect of integrating the pile and the root-clamping column and the effect of dispersing the force to the root-clamping column are lowered. For this reason, the height t of the protrusion is set to 6 mm or more.

Also, the dispersion effect of the force from the pile tip to the ground depends on the shape of the protrusions, but generally spreads at an angle of β with respect to the pile axis direction as shown in FIG. (Β ≦ 45 °). Thus, pile diameter Dt including projections, it is preferable to satisfy the following equation and the diameter D ₂ of the roots hardened column.
D _t + 2 · h · tan β ≦ D ₂
Here, h is the length from the uppermost protrusion embedded in the root consolidation pillar to the bottom of the root consolidation pillar. In order to efficiently propagate the downward force F acting on the steel pipe pile 1 in the radial direction in the root hardening column 2, the protrusion 11 shown in FIGS. 2 (a) and 2 (d) is constituted by a round bar 11A. As shown in FIG. 2C, or when the projection 11 is formed of a triangular bar 11C, it is preferable that the projection 11 has a surface inclined so as to face downward. Further, as shown in FIG. 5, if the height of the protrusion 11 is increased toward the upper part of the root hardening column 11, the force can be effectively distributed to the root hardening column 2.

  Further, in the present invention, when the steel pipe pile is penetrated into the support layer in the ground or the section including the support layer by rotational penetration, a propulsive force is generated in the steel pipe pile by a function as a wood screw at the tip of the pile. In order to ensure workability, the protrusion is preferably spiral. Furthermore, when the protrusion is spiral, the soil near the tip of the pile is carried to the upper side of the pile circumferential surface at the time of rotation penetration, so that the ground around the pile is compacted and the circumferential frictional support force is improved. At this time, if the height of the protrusion is 6 mm or more, the propulsive force at the time of rotation penetration becomes high, and the penetration of the pile is improved.

Moreover, when attaching a protrusion by spirally winding around a pile, it is preferable that protrusion protrusion angle (theta) shown in FIG. 2 shall be 45 degrees or less. This is because if the protrusion winding angle θ is too large, the downward force acting on the pile cannot be efficiently transmitted from the protrusion to the root pillar. When the protrusion has a large area such as a flat wing, that is, when the height t of the protrusion with respect to D ₁ is large, the penetration resistance at the time of rotation penetration of the pile increases, and the workability deteriorates. Therefore, considering the workability at the time of penetration of the pile, the height of the projection is preferably small to some extent, it is preferably not more than 10% of the pile diameter D _1. If the protrusion is spirally or annularly wound, the supporting force is improved as compared with the case where there is no protrusion. In order to sufficiently obtain the effect of dispersing the force acting on the above-mentioned pile, it is preferable to have a plurality of turns in a spiral shape or an annular shape. When a plurality of protrusions are wound, it is preferable to provide a protrusion interval in the axial direction of the pile so that all the protrusions are covered with the root hardening pillar.

By the way, in FIG. 1A, it is shown that the entire section in the height direction of the consolidation column 2 is located in the support layer of the ground 3, but depending on the ground 3, the height direction of the consolidation column 2 is shown. It is also possible to position the lower part in the support layer from a part of the section or from the middle of the height direction section of the solidified column.
Here, the size of the root compaction column 2, one or more times the pile diameter D ₁ dimension of the steel pipe pile 1 the height H of the root compaction column 2, it is preferably 5 times or less. The reason for this is that when the height H of the consolidation column 2 is less than 1 times the pile diameter D ₁ of the steel pipe pile 1, the pile tip insertion length S in the consolidation column 2 is shortened, and the tip supporting force is insufficient, whereas, if you exceed five times the pile diameter D ₁ dimension of the steel pipe pile 1 the height H of the root compaction column 2, the construction cost for the root firm pillar construction is increased End up. For this reason, the height H of the consolidation column 2 is set to the above range, and the pile tip insertion length S in the consolidation column 2 can be made appropriate. A sufficient fixing force can be given between them. At that time, the pile tip insertion length S in the consolidation column 2 is set to 0.6 to 0.9 times the height H of the consolidation column 2, so that the distal end is within the limited range of the consolidation column 2 height. It is more preferable because the supporting force can be effectively increased.

The diameter D ₂ of the root compaction column 2 is more than 1.2 times the pile diameter D ₁ of the steel pipe pile 1, it is preferable to 2.0 times or less. The reason for limiting in this way is as follows. The diameter D ₂ of the root compaction column 2 comes to more than 2.0 times, auger head and construction machine will be described later becomes large-scale. On the other hand, the diameter D ₂ of the root compaction column 2 is less than 1.2 times the pile diameter D ₁ of the steel pipe pile 1, there is a case where the tip supporting force improving effect may not be obtained disadvantageously required is generated. Therefore, it is preferable that the diameter D ₂ of the root compaction column 2 and 1.2 to 2.0 times the pile diameter D ₁ of the steel pipe pile 1.

In the support structure of the foundation pile of the present invention, pile diameter D ₁ is particularly suitable for steel pipe piles 100 to 2000 mm. In the support structure of the foundation pile of this invention demonstrated above, in FIG.1 (a), the part except the front-end | tip part of the steel pipe pile 1 currently fixed to the root hardening pillar 2 is directly contacting with the surrounding ground. Although it showed, in the support structure of the foundation pile of this invention, it was made for the part except the front-end | tip part of the steel pipe pile 1 to contact with the surrounding ground through the earth and sand fixed using solidification liquid, such as cement milk. Also good.

Next, the construction method of the foundation pile of this invention which obtains the support structure of the foundation pile mentioned above is demonstrated.
First, 1st Embodiment of the construction method which obtains the structure of the foundation pile shown to Fig.1 (a) and FIG.1 (b) is described using FIGS.
FIG. 6 is a schematic longitudinal sectional view showing the construction process of the foundation pile of the present invention, and FIG. 7 is a sectional view of the principal part showing the auger used in the construction method of the present invention. 7A shows an auger 5 using the screw 5A as a stirring member, and FIG. 7B shows an auger 5 using the rod 5B as a stirring member. FIG. 8 is a schematic sectional view showing a double auger rotation motor 32 for rotating the pile 1 and the auger 5. 6 and 7, 6 is an auger head, 51 is a through hole, in FIG. 8, 33 is an outer shaft, 34 is an inner shaft, and 41 is a hose connected to a through hole 51 provided in the auger 5. is there.

  In this embodiment, for example, as shown in FIG. 8, the steel pipe pile 1 and the auger 5 are connected to a double auger rotation motor 32 to rotate the auger head 6 capable of expanding the blade disposed at the tip of the steel pipe pile 1. The steel pipe pile 1 is rotated in the direction opposite to the rotation of the auger 5, and the steel pipe pile 1 is sequentially penetrated into the ground 3 from the surface 3 </ b> B of the ground 3 together with the auger head 6. At that time, the steel pipe pile 1 provided with a spiral projection having a height of 6 mm or more on the outer periphery of the tip is used, and the rotation of the pile is caused by the action of the wood screw by the projection and the excavation softening action of the ground by the auger 5. Time workability can be secured. Then, as shown in FIG. 6B, the auger head 6 is expanded when the auger head 6 reaches a predetermined position above the support layer or the support layer for constructing the root hardening column, and the auger head 6 A solidification material liquid such as milk is ejected, and a solidification liquid such as cement milk and earth and sand are stirred and mixed to construct a solidified pillar.

The excavation diameter by the auger head 6 after the wing expansion is larger than the diameter D _t of the steel pipe pile 1 including the protrusion, and is equivalent to the diameter D _{2 of the} solidified column to be constructed. Further, the excavation length by the auger head 6 after expanding the blades is equivalent to the height H of the solidified pillar to be constructed. In this way, after the rotation penetration of the section of the solidified pillar to be constructed is finished, the tip of the steel pipe pile 1 is expanded and left in the excavated section, and the auger 5 is pulled out, and the solidified liquid is removed over time. Solidify to build the root pillar 2.

By constructing in this way, a support structure for a foundation pile as shown in FIGS. 1A and 1B can be obtained.
At this time, more than 1 times the pile diameter D ₁ dimension of the steel pipe pile height H of the root compaction column 2 of building, it is preferable to be 5 times or less, still further, the pile tip insertion length in roots compaction in column More preferably, S is 0.6 to 0.9 times the height H of the solidified column. Since these reasons have been described above, they will be omitted.

In addition, when the diameter D ₂ of the solidified pillar 2 to be constructed exceeds twice the pile diameter D ₁ , the auger head 6 has a larger excavation diameter after expanding the blade, and the auger head and the construction machine are enlarged. since such as the need to have arise, preferably to less than twice the pile diameter D _1, on the other hand, when the diameter D ₂ of the roots compacted column less than 1.2 of pile diameter D ₁ of the steel pipe pile, necessary the tip supporting force improving effect can not be obtained inconvenience may occur, preferably the diameter D ₂ of the roots compacted column 1.2 times or more of the pile diameter D ₁ of the steel pipe pile.

  Here, in order to rotate the steel pipe pile 1 and the auger 5, as shown in FIG. 9, a pile rotation motor 35 and an auger rotation motor 36 may be used instead of the double auger rotation motor 32. Moreover, the rotation direction of an auger and a steel pipe pile can also be made into the same direction. Further, in the above example, the auger head 6 having a blade expansion mechanism is used. However, the auger head used in the present invention is not limited to this. For example, as shown in FIG. May be excavated in the section of the solidified column constructed by high pressure injection of the solidified liquid from the auger head 6.

  In the foundation pile construction method according to the first embodiment of the present invention described above, the spiral protrusion as described in FIGS. 2A, 2B, and 2C is provided on the outer periphery of the tip. Use the steel pipe pile 1 until the auger head 6 reaches the upper end of the section where the solidification column is to be constructed, and drill without expanding the excavating diameter of the auger head 6 and rotate the steel pipe pile 1 to rotate. Therefore, the rotational torque during construction can be reduced, the workability can be improved, and the ground around the pile is not significantly disturbed, so the peripheral friction between the pile after construction and the surrounding ground The force and the horizontal ground reaction force can be made sufficiently large, and the tip portion provided with the protrusion is rooted and fixed to the root fix portion, so that a high tip support force can be obtained. Moreover, the construction method of the foundation pile which concerns on the 1st Embodiment of this invention is suitable for the deep construction of soft ground.

Next, a foundation pile construction method according to the second embodiment will be described with reference to FIGS. 10 (a) to 10 (c). According to the construction method of 2nd Embodiment, the support structure of a foundation pile as shown in FIG.10 (c) can be obtained.
The construction method of the second embodiment does not start excavation by inserting the auger into the hollow portion of the steel pipe pile, but excavates the pile hole in advance by rotating only the auger into the ground.

As the auger 5, an auger head 6 having a wing expansion mechanism is used, and the digging diameter when the wing is expanded is larger than the diameter D _t of the steel pipe pile 1 including the protrusion, and the diameter D of the solidification column to be constructed ₂ equivalent. Further, the excavation length by the auger head 6 after expanding the blades is equivalent to the height H of the solidified pillar to be constructed. In addition, until it reaches the upper end of the section of the consolidation column to be constructed by the auger head 6, excavation is performed without expanding the auger head 6, and when the upper end of the section of the consolidation column to be constructed is reached. As shown in FIG. 10B, the auger head 6 is expanded to perform excavation. Further, when excavating this section, the solidifying material liquid such as cement milk is continuously ejected, and the solidified liquid such as cement milk and earth and sand are stirred and mixed to construct the root hardening column 7. For the purpose of improving the supporting force of the root hardening column, sand, gravel, etc. may be mixed into the solidified liquid. Then, when the auger head 6 reaches the lower end of the rooting portion 2 to be constructed, the auger 5 is pulled out by terminating the rotational penetration of the auger. The size of the root hardening portion 2 to be constructed is preferably the same as that of the first embodiment described above.

Next, before the solidification column 7 is solidified, the steel pipe pile 1 provided with a projection having a height of 6 mm or more is inserted into the outer periphery of the tip described in FIG. 2, and the tip of the steel pipe pile 1 is expanded and excavated. It inserts into the root consolidation pillar 7 of a section, the earth and sand softened with progress of time are solidified, and a pile front-end | tip part and the consolidation pillar 2 are integrated.
In addition, in the construction method of the foundation pile which concerns on 2nd Embodiment, since a steel pipe pile will be penetrated into the pile hole excavated with the auger, it is not necessarily necessary to rotate and penetrate the steel pipe pile which provided the helical protrusion. A steel pipe pile provided with an annular protrusion as shown in FIG. 2 (d) may be used. Also, in order to obtain the peripheral friction force and horizontal ground reaction force between the pile and the surrounding ground, a solidified liquid such as soil cement is injected before the auger head reaches the section where the root hardening column is to be constructed. You may do it. Needless to say, an auger head having a high-pressure injection mechanism for a solidified liquid such as cement milk shown in FIG. 11 may be used.

  The construction method of the foundation pile which concerns on such a 2nd Embodiment of this invention is a steel pipe pile 1 after excavating a pile hole beforehand and constructing the consolidation pillar 7 before solidifying the pillar 7 solidifies. Therefore, the workability when the steel pipe pile 1 is penetrated is improved. This construction method for excavating a pile hole in advance is suitable for a relatively hard ground generally shallower than 30 m.

  In order to confirm the effect of the support structure of the foundation pile according to the present invention described above, a steel pipe pile provided with a projection having a height of 6 mm or more on the outer periphery of the tip portion is used, and a frame is formed around the tip portion of the steel pipe pile. Then, concrete in which sand, gravel, etc. were mixed in cement milk was poured into the frame body, a test body in which the tip of the pile and the solidified pillar were integrated, and a loading test was performed indoors. At that time, as shown in Table 1, steel pipe piles provided with protrusions having a height of 6 mm or more on the outer periphery of the tip portion were used as invention examples (test bodies 2 to 11). In this case, a round bar having a different diameter was spirally wound around the outer periphery of the tip of the steel pipe pile 1, and the protrusion and the steel pipe pile were joined by welding. The number of wrapping steps of the protrusions was 1-6.

Moreover, it was set as the comparative example (test body 1) using the steel pipe pile which does not provide protrusion on the front-end | tip outer periphery.
In the loading test, the load is placed on a rigid floor with the root column side down, and the load loaded on the upper part of the steel tube pile until the failure occurs between the steel tube pile and the root column (same as in Fig. 3). The maximum support load at the time when a fracture occurred between the steel pipe pile and the solidified column was determined.

  Table 1 and FIG. 14 show the maximum tip support load obtained by the loading test.

From the results shown in Table 1 and FIG. 14, it can be seen that the invention examples (test bodies 2 to 11) have a higher tip supporting force than the comparative example (test body 1).
In addition, in the case of the invention example (test bodies 2 to 11), since the protrusion is provided on the outer periphery of the tip of the pile, the downward force F acting on the pile 1 is applied as described in FIG. Protrusions 11 are distributed and transmitted to a number of locations in the consolidation column 2, and further, force is transmitted in the radial direction of the consolidation column 2, and as a result, the angle α is 25 to 50 ° within the consolidation column 2. A fracture surface (broken line in FIG. 15A) was generated. On the other hand, in the case of the comparative example (test body 1), no protrusion is provided on the outer periphery of the tip of the steel pipe pile 1, so that the force propagates only to the lower end of the pile as shown in FIG. Stress concentration occurred, and cracking occurred at a lower tip support load than in the case of the above inventive examples (test bodies 2 to 11).

  Further, in the case of the inventive examples (test bodies 2 to 11), the length of b shown in FIG. 15A was examined, and as a result, b / t = 2 to 5 (t is the height of the protrusion). In the case of the inventive examples (test bodies 2 to 11), the interval p (pitch p) between the protrusions is set to be five times or more the protrusion height t (p / t = 7.7 to 33 in Table 1). It is considered that a fracture surface having an angle α of 25 to 50 ° schematically shown in FIG.

The measured intensity of the root consolidated pillar (concrete strength to form roots compaction column), compressive strength sigma _c is 25 N / mm ^2, in splitting strength tau _c is _{^{2.5 N / mm 2, σ c}} / τ c = It was 10. The concrete compressive strength under the protrusion is expressed as t × σ _c , and the concrete shear strength between the protrusions is expressed as p × τ _c (see FIG. 15 (b)). In the relational expression k × (t × σ _c ) = p × τ _c , if the proportionality constant k≈0.77 to 3.3, p / t = 7.7 to 33 in the example of the invention is almost obtained. Match results.

  Since it is possible to construct a foundation pile having a high tip support force while ensuring good workability, there is a remarkable industrial effect.

1 Steel pipe pile (pile)
11, 11A, 11B, 11C, 11D protrusion
12 In-pipe prevention t Protrusion height L Length from the tip of the pile provided with protrusions 2 Root-clamping pillar 3 Ground
3A Upper end of support layer
3B ground D ₁ pile diameter D _t pile tip diameter D ₂ roots firm pillars of diameter S root compaction column in height θ projections pile tip insertion length H roots consolidated pillar in wrap angle 5 augers including projections
51 Through hole
5A, 5B Stirring member 6 Auger head 7 Mixture of earth and sand and solidification material liquid
32 double auger rotary motor
33 Outer shaft
34 Inner shaft
35 pile rotation motor
36 auger rotary motor

Claims (9)

A steel pipe pile penetrating into a solidified column, wherein the height t is 6 mm or more and 10% or less of the steel pipe pile diameter D _{1 at} the outer periphery of the tip of the steel pipe pile, and the ratio P / t with the pitch P is 7.7 to 33 wrap angle θ is have a helical projection of 45 ° or less, the bonding strength between the protrusion and the steel pipe pile is greater than tau _c × p against splitting strength tau _c of concrete forming the root compaction column A steel pipe pile characterized by that.   The steel pipe pile according to claim 1, wherein the spiral protrusion is provided in 1 to 6 stages.   The steel pipe pile according to claim 1 or 2, and a solidified column formed in a support layer in the ground or a section including the support layer and embedded with a spiral protrusion provided on an outer periphery of a tip portion of the steel pipe pile. And a excavation hole that is excavated in the ground and is in contact with the portion excluding the tip of the steel pipe pile, either directly or via fixed soil. Wherein 1-5 times the height H of the steel pipe pile diameter D ₁ of the root firm pillar, the diameter D ₂ and 1.2 to 2.0 times the steel pipe pile diameter D _1, the distal end portion of the steel pipe pile at the root compaction in column 4. The steel pipe pile support structure according to claim 3, wherein an insertion length S is 0.6 to 0.9 times the height H.   An auger is inserted into the hollow portion of the steel pipe pile according to claim 1 or 2, and the ground is excavated by the auger and the steel pipe pile is rotated and penetrated to construct a solidified column including a support layer or a support layer in the ground. When the auger head reaches the section where the auger head reaches, the excavating diameter of the auger head is expanded to be equivalent to the diameter of the consolidation column and excavated by the height of the consolidation column, and the solidified liquid is ejected from the auger head, The steel pipe pile is rotated and penetrated into the root hardening column, and after the rotation penetration is finished, the auger is pulled out leaving the tip of the steel pipe pile at the root hardening column, and the solidified liquid is solidified. Steel pipe pile construction method.   Prior to penetrating the steel pipe pile according to claim 1 or 2, when the auger head reaches a section in which a ground is excavated by an auger and a solidified column including the support layer or the support layer is constructed in the ground. The excavation diameter of the auger head is expanded to be equivalent to the diameter of the consolidation column, and the solidification liquid is ejected from the auger head after excavation by the height of the consolidation column. A method for constructing a steel pipe pile, characterized in that a drilling hole excavated by the auger and the root hardening column are rotationally inserted to embed the tip of the steel pipe pile in the root hardening column and further solidify the solidified liquid. Wherein 1-5 times the height H of the steel pipe pile diameter D ₁ of the root firm pillar, the diameter D ₂ and 1.2 to 2.0 times the steel pipe pile diameter D _1, the distal end portion of the steel pipe pile at the root compaction in column The construction method of the steel pipe pile according to claim 5 or 6, wherein an insertion length S is 0.6 to 0.9 times the height H.   The construction of the steel pipe pile according to any one of claims 5 to 7, wherein the auger head has a wing expansion mechanism, and the root pillar is excavated by expanding the auger head. Method.   8. The auger head has a high-pressure injection mechanism capable of injecting the solidified liquid, and excavating the root hardening column by injecting the solidified liquid at a high pressure from the auger head. The construction method of the steel pipe pile as described in any one.

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