JP5177064B2 - Foundation pile and its construction method - Google Patents

Description

  The present invention relates to a foundation pile used in a civil engineering / architecture field, such as a harbor structure or a bridge foundation or a building foundation, and a construction method thereof.

Conventionally, it is a friction pile that expects the frictional force of the outer peripheral surface of the pile, and as a means to increase the peripheral frictional force of the pile, the outer peripheral surface of the pile tip is a tapered outer peripheral surface, or the outer peripheral surface of the entire pile length is It is known to have a tapered outer peripheral surface (see, for example, Patent Documents 1 and 2).
It is also known that tapered piles having a tapered outer peripheral surface are driven into a lattice shape and the ground surface layer portion is compacted to prevent liquefaction (see, for example, Patent Document 3).
It is also known to allow a tapered pile to penetrate into the ground in order to remove the negative circumferential frictional force (see, for example, Patent Document 4).

  In addition, a closed-end pile in which a conical cone is provided at the tip of the pile to close the tip and a tapered outer peripheral surface is also known (see, for example, Patent Document 5).

  In addition, in order to embed cast-in-place reinforced concrete piles and prefabricated concrete piles, it is also known to use a casing having a tapered outer peripheral surface and a tapered inner peripheral surface on the tip side (see, for example, Patent Documents 6 and 7). .

  In addition, in order to smoothly transfer the load between the solidified part formed at the tip of the straight steel pipe pile and the steel pipe pile, the steel pipe pile inner peripheral surface or It is also known to increase the integration with the root-fixing part by attaching it to the tip part or by providing a friction cutter on the outer peripheral surface of the steel pipe pile tip part (see Non-Patent Document 1, for example).

Japanese Patent Laid-Open No. 2003-3465 JP 2007-327280 A JP 2008-190116 A JP-A-57-81526 JP-A-8-284160 JP 2008-2977752 A JP 2005-248439 A

Steel pipe pile Nakaborori pile construction method (cemented milk jet stirring method) construction guidelines Page 6, pages 10-13 July 2008 Steel Pipe Pile Association

  The pile having a tapered portion at the conventional tip end is intended to obtain a high frictional force on the circumferential surface of the pile, and is intended to be integrated with a root consolidation portion (enlarged root consolidation bulb) provided at the tip end portion of the pile. It is not a thing. Moreover, it is not known to embed the tapered portion and the root-solidified portion by embedding the tapered portion at the tip of the pile in the root-solidified portion.

By the way, the foundation pile using the steel pipe pile includes a foundation pile using a closed end pile in which the tip of the steel pipe pile is closed, and a foundation pile using an open end pile having an open end. Belongs to a foundation pile using an open-ended pile whose tip is opened.
Moreover, in the foundation pile using a steel pipe pile, there exists a foundation pile which does not provide a root solidification part, and a foundation pile which provides a root consolidation part, and this invention belongs to the foundation pile which provides a root consolidation part.

In order to obtain a large bearing capacity with steel pipe piles with open ends, it is necessary to close the opening, and for that purpose, it is necessary to deeply embed the steel pipe pile in the support layer. This leads to an increase in cost. Therefore, in order to easily obtain a high bearing capacity, a technique is known in which a root-solidified portion is formed, the bottom area of the pile is increased, and the opening of the steel pipe pile is reliably closed.
At the time of pile construction, in order to carry out construction while maintaining the construction speed, it is necessary to drain most of the earth and sand that intrudes into the steel pipe pile. However, since the earth and sand discharged are treated as construction generated residual soil, not only is the treatment expensive, but the environmental load for the treatment is also large.
As a result of studying a combination of a pile having a tapered portion at the tip of the pile and a root consolidation portion, the present inventor, as a result of embedding part or all of the tapered portion in the root consolidation portion, pushing in which acts on the pile For force, the load can be transmitted from the outer peripheral surface of the tapered part to the root consolidation part. However, it has been found that some or all of these stoppers can be omitted.
In addition, by providing a tapered portion at the tip of the steel pipe pile, the opening area of the opening at the tip of the pile can be reduced, so that the amount of soil entering the steel pipe pile can be suppressed, and the required amount of soil removed The present invention was completed by obtaining the knowledge that the construction method of digging and pressing while rotating the steel pipe pile can reduce the resistance at the tip of the pile, etc., and is effective. It was.
This invention can provide the foundation pile which can eliminate the said subject, and can aim at integration of the pile which has a taper-shaped part in a pile front-end | tip part, and a root-solidification part reliably, and its construction method. Objective.

The foundation pile of the first invention is a foundation pile using a steel pipe pile, and the steel pipe pile has a tapered outer peripheral surface and a tapered inner peripheral surface that gradually reduce in diameter toward the distal end. Ratio (H1 / D1) between the length (H1) in the pile longitudinal direction of the tapered portion and the pile outer diameter (D1) of the steady portion where the outer diameter of the steel pipe pile is constant Is a steel pipe pile that is in the range of 0.1 to 2.0, characterized in that the tapered portion is embedded in a rooting portion that is formed so as to embed the tip portion of the steel pipe pile. .
The foundation pile of the second invention is characterized in that in the foundation pile of the first invention, a part of the tapered part or the whole of the tapered part is embedded in the root hardening part.
The foundation pile of the third invention is the ratio of the outer diameter (D2) of the tip of the tapered portion and the outer diameter of the steel pipe pile (D1) above the tapered portion in the foundation pile of the first or second invention (D2 The diameter reduction rate of the tapered portion which is / D1) is in the range of 0.80 to 0.95.
The construction method of the foundation pile of the 4th invention is a construction method of the foundation pile which excavates and constructs by a medium digging using a steel pipe pile, and the said steel pipe pile is a taper which gradually reduces diameter toward the front-end | tip part. A pile having a tapered portion having a tapered outer peripheral surface and a tapered inner peripheral surface and having an opening at the tip, a pile longitudinal length of the tapered portion (H1), and a steel pipe pile having a constant outer diameter It is a steel pipe pile in which the ratio (H1 / D1) to the outer diameter (D1) is in the range of 0.1 to 2.0, and the rooted portion is embedded so as to embed the tapered portion at the tip of the steel pipe pile. It is characterized by creating.
The foundation pile construction method of the fifth invention is characterized in that, in the foundation pile construction method of the fourth invention, a rooted portion is formed so as to embed a part of the tapered portion or the entire tapered portion in the steel pipe pile. And
The foundation pile construction method of the sixth invention is the foundation pile construction method of the fourth invention or the fifth invention, characterized in that the steel pipe pile is rotationally press-fitted simultaneously with the inside digging.
The foundation pile construction method of the seventh invention is characterized in that, in the foundation pile construction method of the fourth invention or the fifth invention, at the same time as the medium digging, the lower part further than the tip of the steel pipe pile is excavated.
The foundation pile construction method of the eighth invention is the foundation pile construction method of the fourth invention or the fifth invention, wherein the steel pipe pile is rotationally press-fitted simultaneously with the inside digging and further below the tip of the steel pipe pile is excavated. It is characterized by that.
The construction method of the foundation pile of the ninth invention is the construction method of the foundation pile of any one of the fourth invention to the eighth invention, from the outer diameter (D2) of the tip of the tapered portion in the steel pipe pile and the tapered portion. The reduction ratio of the tapered portion, which is the ratio (D2 / D1) to the outer diameter of the steel pipe pile (D1), is in the range of 0.80 to 0.95.

In the first invention, the steel pile is a foundation pile using a steel pipe pile, and the steel pipe pile includes a tapered outer surface having a tapered outer peripheral surface and a tapered inner peripheral surface that gradually decrease in diameter toward the distal end. The steel pipe in which the tip is opened and the ratio of the length of the tapered portion in the pile longitudinal direction to the pile outer diameter of the steady portion where the outer diameter of the steel pipe pile is constant is in the range of 0.1 to 2.0 . Since it is a pile and it is not necessary to provide a tapered part over the entire length of the pile, it can be an economical steel pipe pile with a tapered part at the tip, and the taper part and the solidified part are reliably attached. The effect which can be used as the foundation pile which can be obtained is acquired. In addition, since the tapered portion is embedded in the root consolidation portion formed so as to embed the steel pipe pile front end portion, for the pushing force acting on the pile, the root consolidation portion from the tapered portion outer peripheral surface In this way, when securing adhesion with the rooting part, the steel pipe pile has been provided with a detent such as a reinforcing bar on the inside or outside, but part of these detents, or The effect that all can be omitted is obtained.
In the second invention, in the foundation pile of the first invention, a part of the tapered portion or the entire tapered portion is embedded in the root-solidified portion. Therefore, the length embedded in the root-solidified portion in consideration of the support layer is set. The effect which can be suitably selected by design and can be used as an economical foundation pile is acquired.
In the third invention, in the foundation pile of the first invention or the second invention, the contraction of the tapered part which is a ratio of the outer diameter (D2) of the steel pipe pile tip to the outer diameter (D1) of the steel pipe pile above the tapered part. Since the diameter ratio is in the range of 0.80 to 0.95, it is possible to reduce the earth and sand that enters the steel pipe pile, and it can be used in combination with an earth auger equipped with an expanded excavation jig. It is also possible, and it can be set as the steel pipe pile which can aim at the reliable integration with a root hardening part.
According to a fourth aspect of the present invention, there is provided a method for constructing a foundation pile that is excavated and constructed by using a steel pipe pile, and the steel pipe pile has a tapered outer peripheral surface and a taper that are gradually reduced in diameter toward the tip. Pile outer diameter (D1) of a stationary part with a taper-shaped part provided with a cylindrical inner peripheral surface and having an open end , the length of the taper-shaped part in the pile longitudinal direction (H1), and the outer diameter of the steel pipe pile is constant Steel pipe pile with a ratio (H1 / D1) in the range of 0.1 to 2.0, and it is not necessary to provide a tapered portion over the entire length of the pile, so an economical steel pipe with a tapered portion at the tip The effect which can be set as a pile and can construct easily the foundation pile which can aim at adhesion of a taper-shaped part and a root solidification part reliably is acquired. In addition, since the rooted portion is formed so as to embed the tapered portion of the steel pipe pile front end portion, the steel pipe pile front end portion is reduced in diameter by the tapered portion tip, so that the earth and sand are surrounded by the tapered portion. Since the amount of earth and sand flowing into the steel pipe pile is reduced by the reduced diameter, the required amount of soil removal can be reduced, and the taper-shaped part is used for the root consolidation part. Adhesion with a locking effect increases, and the adhesion effect increases. With the intermediate excavation root consolidation method, part or all of the locking jig required to remove adhesion with the root consolidation part can be omitted. An effect is obtained.
In the fifth invention, in the construction method of the foundation pile according to the fourth invention, since the root-clamping portion is formed so as to embed a part of the tapered portion or the entire tapered portion in the steel pipe pile, the root is taken into consideration by taking the support layer into consideration. It is possible to obtain an effect that an economical foundation pile can be constructed by appropriately selecting the length embedded in the hardened portion by design.
In the sixth invention, in the foundation pile construction method of the fourth invention or the fifth invention, since the steel pipe pile is rotationally pressed simultaneously with the digging, the circumference of the steel pipe pile with a tapered portion including a tapered portion is included. The effect that it can construct by reducing a surface frictional force is acquired.
In the seventh invention, in the construction method of the foundation pile of the fourth invention or the fifth invention, the lower part further than the tip of the steel pipe pile is excavated at the same time as the excavation, compared with the case of excavating only the inside of the pile. The construction efficiency can be increased, construction can be performed in a short time, and the construction cost can be reduced.
In the 8th invention, in the construction method of the foundation pile of the 4th invention or the 5th invention, since the steel pipe pile is rotationally press-fitted at the same time as the inside digging, and further below the tip of the steel pipe pile is excavated, the tapered portion is formed. The steel pipe pile with a tapered portion including the tip can be constructed with reduced peripheral frictional force, and the construction efficiency can be increased.
In 9th invention, in the construction method of the foundation pile in any one of 4th invention- 8th invention, the outer diameter (D2) of the taper-shaped part front-end | tip in the said steel pipe pile, and the steel pipe pile outer diameter above a taper-shaped part ( Since the diameter reduction ratio of the tapered portion, which is the ratio (D2 / D1) to D1), is in the range of 0.80 to 0.95, it is intended to reduce earth and sand entering the steel pipe pile. Can also be used together with an earth auger equipped with an expanded excavation jig, and can also be used with a foundation pile that can be reliably integrated with the root consolidation part. Furthermore, the effect that the foundation pile which can acquire the said effect can be built easily is acquired.

(A) is a partially longitudinal front view showing an operational relationship between a tapered portion and a root-solidified portion when a root-solidified portion is constructed at the distal end portion of a steel pipe pile with a distal-end tapered portion according to an embodiment of the present invention, (B) is a projection view of a tapered portion. It is explanatory drawing which shows the flow of the soil in the case of carrying out rotation press-fitting to the ground using the steel pipe pile with a front-end | tip taper-shaped part of this invention. The penetration ratio (H3 / D1) to the ground and the height ratio of the soil in the pipe (H4 / D1) will be described in the case where the steel pipe pile with a tapered end portion of one embodiment of the present invention is penetrated into the ground. It is explanatory drawing for. It is a graph at the time of changing a diameter reduction rate (D2 / D1) about the penetration ratio (H3 / D1) to the ground and the height ratio (H4 / D1) of soil in the pipe. It is explanatory drawing for demonstrating the 1st example of the construction method of the foundation pile of this invention, (a) is the state which has set excavation jigs, such as an earth auger, (b) has started excavation. The state, (c) is a state where excavation is carried out together with the soil removal, and (d) is a state where a rooted portion is built. It is explanatory drawing for demonstrating the 1st example of the construction method of the foundation pile of this invention, (a) is the state which press-fits the steel pipe pile with a front-end | tip taper-shaped part in the ground, (b). Is a state in which a steel pipe pile with a tapered portion at the tip is being pressed into the ground while further drilling, (c) is a diameter excavation jig when the tip of the steel pipe pile with a tapered portion at the tip reaches the support layer Is a state where the steel pipe pile protrudes downward from the steel pipe pile with the tapered portion at the tip, (d) is a state where the diameter-expanding excavation jig is expanded and excavated, (e) is a cement milk sprayed and mixed with earth and sand And (f) is a state where a steel pipe pile with a tapered end is pressed into the root consolidation part and the earth auger screw is suspended. It is. It is explanatory drawing for demonstrating the 2nd example of the construction method of the foundation pile of this invention, (a) is the state which has set excavation jigs, such as an earth auger screw, (b) has started excavation. (C) is a state where excavation is carried out together with the soil removal, and (d) is a state where a rooted portion is being built. It is explanatory drawing for demonstrating the 2nd example of the construction method of the foundation pile of this invention, (a) is the state which press-fits the steel pipe pile with a front-end | tip taper-shaped part in the ground, (b). Is the state where the steel pipe pile with the tip tapered portion is press-fitted into the ground while rotating the steel pipe pile with the tip tapered portion, and (c) is supported by the tip of the steel pipe pile with the tip tapered portion. When reaching the layer, the expanded drilling jig protrudes downward from the steel pipe pile with the tip tapered part, (d) stops the rotation of the steel pipe pile with the tapered part and expands the drilling (E) is a state where drilling is performed by expanding the diameter of the tool, (e) is a state in which cement milk is sprayed and mixed with earth and sand, and an expanded bulb-like root-solidified portion is constructed by soil cement, (f) is a tapered end A steel pipe pile with a shaped part and press it into the root Then, is a state in which the lifting of the auger screw. It is explanatory drawing for demonstrating the 3rd example of the construction method of the foundation pile of this invention, (a) is the state which is press-fitting the steel pipe pile with a front-end | tip taper-shaped part into the ground, excavating (b) ) Is a state in which a steel pipe pile with a tapered portion at the tip is pressed into the ground while further drilling, (c) is a state in which the tip of the steel pipe pile with a tapered portion at the tip reaches the support layer, (d) (E) is a state of drilling with an enlarged diameter excavating jig, (e) is a state in which cement milk is sprayed and mixed with earth and sand, and an expanded bulb-shaped solidified part made of soil cement is constructed. f) is a state in which a steel pipe pile with a tapered portion at the tip is press-fitted and penetrated into the rooted portion, and the earth auger screw is lifted. It is explanatory drawing for demonstrating the 4th example of the construction method of the foundation pile of this invention, (a) is the state which is pressingly injecting the steel pipe pile with a front-end | tip taper-shaped part into the ground, (b) ) Is a state where the steel pipe pile with the tip tapered portion is rotated and further drilled to press the steel pipe pile with the tip tapered portion into the ground. (C) is the tip of the steel pipe pile with the tip tapered portion. The state where the part has reached the support layer, (d) is the state where the rotation of the steel pipe pile with the tapered portion at the tip is stopped, the state where the diameter expanding excavation jig is expanded and excavated, (e) is the cement milk Sprayed and mixed with earth and sand to build an enlarged bulb-shaped root-solidified part with soil cement. (F) is a steel pipe pile with a tapered tip and is inserted into the root-solidified part. The screw is in a suspended state. It shows the steel pipe pile with a tip taper-shaped part of one form used for the foundation pile of the present invention, (a) is a front view, (b) is a longitudinal front view, (c) is aa sectional view, (D) is a bottom view. It shows a straight steel pipe pile as a comparative example, and (a) is a front view, (b) a longitudinal front view, and (c) a transverse plan view.

    Next, the present invention will be described in detail based on the illustrated embodiment.

  First, with reference to Fig.11 (a)-(d), the steel pipe pile 1 with a front-end | tip taper-shaped part used in the foundation pile of this invention is demonstrated.

  A steel pipe pile 1 having a tapered end portion used in a foundation pile according to the present invention is a steel pipe pile that is driven by a vibration method, other methods, a press-fitting method, preferably a rotary press-fitting method, and a steel pipe whose tip is opened. A tapered outer peripheral surface 2 and a tapered inner peripheral surface 3 are provided on the outer peripheral surface and the inner peripheral surface of the tip portion, respectively, and gradually reduce in diameter in the longitudinal direction of the pile toward the tip.

  As the cross-sectional form of the tapered outer peripheral surface 2 and the tapered inner peripheral surface 3 in the pile longitudinal direction, the outer side and the inner side may be linear as shown in the figure as a cross-sectional form on one side in the pile longitudinal direction. Although not shown, a curved shape may be used. As a cross-sectional configuration of the taper outer peripheral surface 2 and the taper inner peripheral surface 3 in the longitudinal direction of the pile, even if it protrudes outward in the radial direction (concave inward in the radial direction), it protrudes inward in the radial direction (Concave toward the outside in the radial direction).

  As described above, by providing the tapered portion 4 whose diameter is reduced at the tip of the pile, as shown by the arrow in FIG. 2, the soil is actively allowed to flow to the outside of the pile, thereby flowing into the pipe. It becomes possible to reduce soil, and by reducing the opening area of the tip of the pile, it becomes possible to reduce the soil flowing into the pipe, thereby suppressing the occurrence of blockage of the pile tip by the soil in the pipe, It reduces friction between the pipe soil and the inner peripheral surface of the pile, making it possible to reduce pile pressure input.

  By providing the tapered portion 4 at the tip of the pile, the resistance of the soil acting on the tapered outer peripheral surface 3 is increased, but by adopting a method of rotary press-fitting, it is due to adhesion with the sand (or soil) 11 The advantage that it is possible to suppress the increase in friction on the pile peripheral surface is also utilized. A pile outer peripheral surface 9 having a constant outer diameter D1 is connected above the tapered portion 4.

  The ratio (H1 / D1) between the length H1 of the tapered outer peripheral surface 2 (tapered portion) in the pile longitudinal direction and the pile outer diameter D1 of the stationary portion having a constant outer diameter is 0.1-2. Similarly, the ratio (H1 / D1) between the length H1 of the inner side of the taper-shaped inner peripheral surface 3 (tapered portion) in the pile longitudinal direction and the pile outer diameter D1 of the stationary part having a constant outer diameter. Is 0.1 to 2.0 (corresponding to 3 to 22 ° in the taper angle θ). Moreover, the pile outer diameter D2 of the steel pipe pile front-end | tip was represented by the diameter reduction ratio (D2 / D1) which is a ratio with the pile outer diameter D1 of the steady part with the constant outer diameter of the steel pipe pile above the taper-shaped part 4. In some cases, the diameter is reduced to an outer diameter D2 in the range of 0.80 to 0.95. The diameter reduction rate (D2 / D1) is the diameter reduction rate of the steel pipe pile tip. In the present invention, the length H1 of the tapered portion 4 in the pile longitudinal direction (same as the pile axis direction), the outer diameter D2 of the tip of the tapered portion 4 and the outer portion of the steady portion having a constant outer diameter. There is a relationship of tan θ = (D1−D2) / 2H1 between the diameter D1 and the taper angle θ.

  As described above, the ratio of the length H1 in the longitudinal direction of the pile of the tapered outer peripheral surface 2 and the tapered inner peripheral surface 3 (tapered portion) to the pile outer diameter D1 of the stationary portion having a constant outer diameter (H1 / D1) is set to 0.1 to 2.0, and the pile outer diameter D2 at the tip of the steel pipe pile is connected to the tapered portion 4 so that the outer diameter of the steel pipe pile above the tapered portion 4 is constant. The reason why the ratio is in the range of 0.80 to 0.95 when expressed in terms of the diameter reduction ratio (D2 / D1), which is the ratio (D2 / D1) to the outer diameter D1 of the pile, will be described.

First, about the case where the steel pipe pile 1 with a taper-shaped tip part as shown in FIG. 3 is penetrated into the ground 15, FIG. 4 shows a steady state in which the penetration amount H 3 into the ground and the outer diameter of the steel pipe pile are constant. About the ratio (H3 / D1) with the pile outer diameter D1 of the part, the height H4 of the soil in the pipe, and the ratio (H4 / D1) with the pile outer diameter D1 of the steady part where the outer diameter of the steel pipe pile is constant, When the diameter reduction ratio (D2 / D1) is changed to 0.70, 0.80, 0.90, 0.95 and when the diameter reduction ratio (D2 / D1) is 1.00 (as a comparative example, FIG. 12 is equivalent to a straight steel pipe pile 10 having a constant outer diameter D1 having no tapered portion as shown in FIG. As shown in FIG. 4, when the diameter reduction ratio (D2 / D1) is reduced, the ratio (H4 / D1) between the soil height H4 in the pipe and the pile outer diameter D1 of the steady portion where the outer diameter of the steel pipe pile is constant. ) Is small, the soil height H4 in the pipe is low, the soil entering the pipe is small, the height H4 of the pipe soil 14 is low, and the steel pipe pile inner peripheral surface 12 and the pipe soil 14 adhere to each other. Can be reduced.
It can be seen that when the diameter reduction ratio (D2 / D1) is smaller than 0.95, the soil entering the pipe can be reduced by about 10% compared to the straight steel pipe pile 10 having no tapered portion. Therefore, the upper limit of the diameter reduction ratio (D2 / D1) is set to 0.95.

Next, the diameter reduction rate will be specifically examined.
The maximum value of the ultimate bearing capacity (kN / m ² ) at the tip of the digging pile method specified in the road bridge specifications is shown in the table below. However, the table below is applicable when the processing method for constructing the root consolidation portion 5 at the tip of the pile is a cement milk jet stirring method.

As the uniaxial compressive strength Fc of the root hardening part 5, 15 N / mm ² is adopted as a general value.

As shown in FIG. 1, the projected area As (m ² ) of the tapered portion 4 is D1 as the outer diameter of the fixed portion having a constant outer diameter above the tapered portion 4 and the outer diameter of the tip of the tapered portion. When D2, As = ((D1) ^2- (D2) ² ) · π / 4.
Further, the bearing strength P (kN), which is a force exerted as a resistance force when the steel pipe pile that can be expected in the tapered portion 4 is pushed into the root consolidation portion, is assumed that the projected area of the tapered portion 4 is As. , P = As · Fc · α. Although it is a value confirmed through experiments, α = 4 is obtained.
Further, the ultimate tip supporting force Pu (kN) at the tip of the pile is Pu = 7500 · (D1 ² · π) / 4 in the sand layer, and Pu = 10000 · (D1 ² · π) / 4 in the sand layer. .
In order to surely develop the supporting force of the steel pipe pile 1 with the tip tapered portion, the bearing strength P that can be expected from the tapered portion 4 is equal to or greater than the ultimate tip supporting force Pu at the tip of the pile. Since the portion 4 and the rooted portion 5 will not be displaced, it is desirable that P ≧ Pu from the viewpoint of omitting the displacement prevention of the steel pipe pile, and these values are substituted into P = As · Fc · α. Then, the relationship between D2 and D1 is as follows for the sand layer and the gravel layer.
Sand layer: D2 = D1 ・ 0.92
Gravel layer: D2 = D1 · 0.94
If D2 is equal to or smaller than the value of the above formula, no detent is necessary.
Therefore, the most desirable diameter reduction ratio (D2 / D1) value is 0.92 or less for a sand layer and 0.94 or less for a gravel layer.
The lower limit value of the diameter reduction ratio (D2 / D1) is preferably a value that does not interfere with the passage of the screw rod or auger head through the steel pipe pile. If it is about 0.8, construction is possible, and about 0.9 is more desirable. Therefore, regarding the diameter reduction ratio (D2 / D1), a desirable value is 0.80 to 0.95, and the most desirable value is 0.9 to 0.92 when the support layer is a sand layer, and the support layer is a gravel layer. Then 0.9
0 to 0.94.
In addition, if the angle θ of the tapered portion 4 is within 45 °, it is considered that the flow out of the soil is not hindered. 0.1, which is the minimum value of the ratio (H1 / D1) of the taper-shaped portion with respect to the pile outer diameter D1 to the length H1 in the pile longitudinal direction, is a value when the diameter reduction ratio is 0.8 and 45 °. .

  The range of the ratio (H1 / D1) of the length H1 of the tapered portion in the longitudinal direction of the pile and the pile outer diameter D1 of the steady portion where the outer diameter of the steel pipe pile is constant is usually the tip taper to the root consolidation portion 5 Insertion of steel pipe pile 1 with a shape-like part is often about H2 / D1 = 0.5 to 2.0 when the insertion depth to root consolidation part 5 is H2 (see FIG. 1). Therefore, in order for the tapered portion 4 to be completely embedded in the rooting portion 5, H1 / D1 = 0.1 to 2.0 is desirable.

  Next, the construction method of the foundation pile 6 using the steel pipe pile 1 with a front-end | tip taper-shaped part as mentioned above is demonstrated.

5 and 6 are explanatory views of a first example of a construction method in the case of constructing the foundation pile 6 of the present invention using the pile construction device 23. In the construction method of the present invention, the tip tapered shape is used. The construction method of the foundation pile which excavates and constructs the earth and sand which penetrate | invade in the steel pipe pile 1 with a taper-shaped part with a tip using the steel pipe pile 1 with a part is carried out.
5A shows a state in which an excavating jig such as an earth auger screw 16 is set, FIG. 5B shows a state in which excavation has started, and FIG. 5C shows a state in which excavation is performed together with soil removal. , (D) is a state in which the root hardening part 5 is built.
6 (a) shows a state where a steel pipe pile with a tapered end portion is being pressed into the ground while digging, and FIG. 6 (b) shows a state where the steel pipe pile with a tapered end portion is further ground. (C) shows a state where the tip of the steel pipe pile with the tapered end portion reaches the support layer, and the diameter expanding excavation jig is protruded downward from the steel pipe pile with the tapered end portion. Fig. (D) shows a state where the diameter-expanding excavation jig is expanded, and Fig. (E) shows a state where the cemented milk is sprayed and mixed with the earth and sand, and an expanded bulb-shaped solidified with soil cement. (F) is a state in which the steel pipe pile 1 with the tip tapered portion is press-fitted and penetrated into the root hardening portion 5 and the earth auger screw is lifted. The range of the arrow on the left side in FIGS. 9A to 9C is a construction process until reaching the support layer 8, and the range of the arrow on the right side in FIGS. This is a construction process for creating the part 5 (the same applies to FIGS. 8 to 10 below).

The Nakabori method is a method of maintaining high workability by inserting the pile body into the ground and draining the soil flowing into the pile body one after another. In addition to processing costs and transportation costs, CO ₂ generated at that time is also a burden on the environment. Therefore, in the present invention, the tip is tapered to reduce the amount of soil discharged. By using the steel pipe pile 1 with a taper-shaped part, the earth and sand are pushed outside by a taper-shaped part, the circumference | surroundings of a pile are consolidated, and the quantity of the earth and sand discharged | emitted is reduced.
In the case shown in FIGS. 5 and 6, the earth auger screw 16 and the tip tapered shape are lowered by lowering the single-axis earth auger driving device 17 capable of rotating only the earth auger screw 16 along the leader 18. The steel pipe pile 1 with a part is press-fitted into the ground (the state of Fig. 5 (c) and Fig. 6 (a)). Moreover, when the steel pipe pile 1 with the tip tapered portion reaches the support layer 8 (the state shown in FIGS. 6 (c) and 6 (d)), the tip of the earth auger screw 16 from the tip portion of the steel pipe pile 1 with the tip tapered portion. The large diameter excavation jig 19 is protruded and rotationally driven together with the earth auger screw 16, and cement milk is injected at a high pressure from the large diameter excavation jig 19 (state of FIG. 6). In this case, the enlarged diameter excavating jig 19 is lowered or raised so that the enlarged diameter excavating jig 19 provided at the distal end of the earth auger screw 16 is positioned below the distal end of the steel pipe pile 1 with the tapered end portion. Then, the excavating arm 20 is extended and expanded in diameter, and in this state, the earth auger screw 16 is driven, and cement milk is sprayed from the expanded excavation jig 19 so that the taper-shaped portion 4 has an inner peripheral surface. While the adhering soil is washed, earth and sand and cement milk are mixed, and the root-solidified portion 5 made of the soil cement 21 is formed (built) so as to embed part or all of the tapered portion 4. ), The steel pipe pile 1 with a tapered portion at the tip is press-fitted into the root-clamping portion 5, the earth auger screw 16 is pulled up, and the soil cement 21 is hardened. The firm unit 5.
In addition, when the diameter-extended excavation jig 19 is located inside the tapered portion, the inner peripheral surface of the tapered portion can be cleaned by spraying cement milk at a high pressure. In addition, there is an effect of cleaning the inner peripheral surface 3 or the outer peripheral surface 2 of the tapered portion 4 by the stirring flow of cement milk and earth and sand at the stage where the root hardening portion 5 is formed.

  When the tapered portion 4 at the tip end of the steel pipe pile 1 with the tip tapered portion is inserted into the root consolidation portion 5, the tapered portion 4 has a length H1 in the longitudinal direction of the pile and the outer diameter of the steel pipe pile is constant. Since the ratio of the steady portion to the pile outer diameter D1 is in the range of 0.1 to 2.0, if the necessary support force can be obtained, the strength of the support layer 8 is taken into consideration and embedded in the solidified portion. The length may be appropriately selected according to the design, and the root consolidation portion 5 may be built so as to embed a part of the tapered portion 4, or the root consolidation portion 5 may be embedded so as to embed the entire tapered portion 4. You may build it.

In such a case, as shown in FIGS. 7 and 8, a two-axis coaxial earth auger drive device 22 capable of simultaneously rotating and driving both the earth auger screw 16 and the steel pipe pile 1 with a tapered portion at the tip is provided. Thus, the steel pipe pile 1 with a tapered end portion may be rotationally press-fitted at the same time as digging. By rotating the steel pipe pile 1 with the tip tapered portion , the construction efficiency can be improved by reducing the resistance caused by the adhesion between the pile peripheral surface including the tapered portion 4 and the surrounding ground 15.
7A shows a state in which an excavating jig such as an earth auger screw 16 is set, FIG. 7B shows a state in which excavation has started, and FIG. 7C shows a state in which excavation is performed together with soil removal. , (D) is a state in which the root hardening part 5 is built.
In such a construction method, as shown in FIGS. 8 (c) and 8 (d), the steel pipe pile 1 with the tip tapered portion is in a state where the tip portion of the steel pipe pile 1 with the tip tapered portion has reached the support layer 8. The rotation is stopped, the diameter-extended drilling jig 19 is projected from the tip of the steel pipe pile 1 with a tapered end, the drilling arm 20 is widened, and the diameter-extended drilling jig 19 is rotated together with the earth auger screw 16 to make cement. By spraying low-pressure or high-pressure milk from the diameter-expanding drilling jig 19, the earth and sand and cement milk are stirred and mixed, and as shown in FIG. The steel pipe pile 1 with the taper-shaped part is penetrated into the root hardening part 5. In addition, although not shown, it is also possible to form the rooted portion 5 by spraying cement milk at a high pressure from the tip of a generally used excavation auger head without using the diameter-expanding excavation jig 19.

In the case of the Nakabori method, as shown in FIGS. 9 (a) to 9 (c), with the excavation arm 20 in the enlarged diameter excavation jig 19 being opened about the pile diameter, the tip is tapered at the same time as the intermediate excavation. By excavating and excavating the lower part of the steel pipe pile 1 with a part, the construction efficiency of the pile can be improved and construction can be performed in a short time.
Further, in such a construction method, as shown in FIG. 9 (d), the excavating arm 20 is further expanded in diameter, and cement milk is sprayed from the expanded excavation jig 19, so that the solidified portion 5 made of soil cement is used. And the tip of the steel pipe pile 1 with a tapered end portion may be inserted into the root hardening portion 5.

Furthermore, as shown in FIG. 10, at the same time as the middle digging, by further drilling ahead below the steel pipe pile tip with rotating press-fitting the distal tapered portion with Kino steel pipe pile 1, possible to further improve the workability Can do.
Moreover, in the said case, the ratio of the length H1 of the taper-shaped part 4 in the pile longitudinal direction and the outer diameter D1 of the stationary part where the outer diameter of the steel pipe pile is constant is in the range of 0.1 to 2.0. And since it should just penetrate with respect to the root hardening part 5 like a normal pile, since it can construct similarly to the construction method of a conventionally well-known pile, construction becomes easy.

  In the construction method described above, the diameter reduction ratio (D2 / D1) of the tapered portion, which is the ratio of the outer diameter D2 at the tip of the tapered portion and the outer diameter D1 of the steel pipe pile above the tapered portion 4, is 0. When it is set to 80-0.95, the earth and sand which penetrate | invade in a pile can be reduced. In addition, the steel pipe pile 1 with the tip tapered portion and the root consolidation portion 5 are reliably integrated, and the taper portion 4 of the steel pipe pile 1 with the tip tapered portion is tapered against the pushing force and the pulling force. It is possible to easily construct a pile foundation that can effectively transmit the load to the rooted portion 5 by effectively using the outer peripheral surface 2 and the tapered inner peripheral surface 3.

  As a manufacturing method of the steel pipe pile which has a taper-shaped part in the front-end | tip part used in order to construct the foundation pile 6 of this invention, it forms so that the front-end | tip part of one steel pipe may form a taper-shaped part by cold bending forming. It may be manufactured, or it may be manufactured so as to form a tapered portion by cold press molding, or a fan-shaped strip is processed into a cold bending taper shape, and both side edges are joined by welding. Then, a tapered short tube having the same outer diameter as the steel pipe to which the large outer diameter portion is to be connected is manufactured, and the upper end portion of the tapered short tube is fixed to the tip portion of one steel pipe by welding. A steel pipe pile having a tapered portion may be manufactured. Moreover, you may manufacture the steel pipe pile which has a taper-shaped part in the front-end | tip part by carrying out plastic working of the front-end | tip part of one steel pipe.

  When carrying out the present invention, as a means for expanding the excavation arm 20 in the diameter expansion excavation jig 19, a conventionally known mechanical diameter expansion means or a hydraulic diameter expansion means incorporating a hydraulic jack is employed. You may do it.

DESCRIPTION OF SYMBOLS 1 Steel pipe pile with a taper-shaped tip part 2 Tapered outer peripheral surface 3 Tapered inner peripheral surface 4 Tapered part 5 Rooting part 6 Foundation pile 8 Support layer 9 Pile outer peripheral surface 10 with constant outer diameter D1 Straight steel pipe pile 11 Sand (or soil)
DESCRIPTION OF SYMBOLS 12 Steel pipe pile inner peripheral surface 14 Pipe soil 15 Ground 16 Earth auger screw 17 Single axis earth auger drive device 18 Leader 19 Large diameter excavation jig 20 Excavation arm 21 Soil cement 22 Two-axis coaxial earth auger drive device 23 Pile construction device

Claims (9)

A foundation pile using steel pipe piles,
The steel pipe pile has a tapered outer peripheral surface and a tapered inner peripheral surface that gradually decrease in diameter toward the distal end at the distal end, and the distal end is opened, and the length of the tapered portion in the longitudinal direction of the pile is (H1) is a steel pipe pile in which the ratio (H1 / D1) between the pile outer diameter (D1) of the stationary part where the outer diameter of the steel pipe pile is constant is in the range of 0.1 to 2.0 ,
The foundation pile characterized by the said taper-shaped part being embedded in the root hardening part built so that the said steel pipe pile front-end | tip part might be embedded.   The foundation pile according to claim 1, wherein a part of the taper-like portion or the whole taper-like portion is embedded in the root consolidation portion. The diameter reduction rate of the tapered portion, which is the ratio (D2 / D1) of the outer diameter (D2) of the tip of the tapered portion and the outer diameter (D1) of the steel pipe pile above the tapered portion, is 0.80-0. foundation pile according to claim 1 or 2, characterized in that there is a range of 95. It is a construction method of a foundation pile that is excavated and constructed by medium digging using steel pipe piles,
The steel pipe pile has a tapered outer peripheral surface and a tapered inner peripheral surface that gradually decrease in diameter toward the distal end at the distal end, and the distal end is opened, and the length of the tapered portion in the longitudinal direction of the pile is (H1) is a steel pipe pile in which the ratio (H1 / D1) between the pile outer diameter (D1) of the stationary part where the outer diameter of the steel pipe pile is constant is in the range of 0.1 to 2.0 ,
A construction method for a foundation pile, wherein a rooting portion is formed so as to embed the tapered portion of the tip portion of the steel pipe pile. The foundation pile construction method according to claim 4 , wherein the rooting portion is formed so as to embed a part of the tapered portion or the entire tapered portion in the steel pipe pile. At the same time with the in digging, the construction method of the foundation pile according to claim 4 or 5, characterized in that the rotating press-fitting the steel pipe pile. The foundation pile construction method according to claim 4 or 5 , wherein a lower portion further than the tip of the steel pipe pile is excavated simultaneously with the middle excavation. The construction method of a foundation pile according to claim 4 or 5 , wherein a steel pipe pile is rotationally press-fitted at the same time as the inside digging, and a lower portion is further excavated from the tip of the steel pipe pile. The diameter reduction rate of the tapered portion, which is the ratio (D2 / D1) of the outer diameter (D2) of the tip of the tapered portion in the steel pipe pile and the outer diameter (D1) of the steel pipe pile above the tapered portion, is 0.00. It is set as the range of 80-0.95, The construction method of the foundation pile of any one of Claims 4-8 characterized by the above-mentioned.

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