JP2003064673A - Foundation pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foundation pile which can offer great bearing capacity by using a thin-walled steel pipe. SOLUTION: A bottom plate 12, which is provided with a pair of excavating blades 11, is fixed, by welding, etc., to an end face of an opening at an end (lower end) of a pile body 10 which is composed of the thin-walled steel pipe, so as to block up the end face of the opening; a single turn of a spiral blade 14, which has an outside diameter approximately three times larger than a pile diameter, is fixed to an outer peripheral face on the side of the end by the welding, etc.; an auxiliary spiral blade 15, which has an outside diameter larger than that of the spiral blade 14, is fixed, by the welding, etc., to a place away from the spiral blade 14 by a distance T which is at least one and a half times (approximately two and a half times in Fig. 1) larger than the outside diameter of the spiral blade 14; and the spiral blades 14 and 15 wholly bear subgrade reactions, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a foundation pile that can be buried in soft ground without vibration and can obtain a sufficient supporting force.

[0002]

As a foundation pile which is buried in soft ground with no soil, noise, and vibration, for example, a plurality of spiral blades are welded to a peripheral surface of a steel pipe at predetermined intervals. It is known that it is fixed and configured. In this type of foundation pile, an auger device is used, and while the steel pipe is replenished, the top pile body provided with a plurality of spiral blades is rotatably propelled until it reaches a predetermined depth in the ground and is embedded in the ground. After burial,
A structure is constructed on the foundation pile, and the load of the structure acts on the upper end of the foundation pile, while the ground reaction force acts on each spiral wing, so that the structure does not sink. I support you.

In the above foundation pile, each spiral blade exerts a supporting force by receiving the ground reaction force. Therefore, it was considered that the larger the number of spiral blades, the larger the supporting force can be obtained. Actually, there is almost no correlation between the number of spiral blades and the supporting force, and it was found that the supporting force does not increase so much even if the number of spiral blades is increased.

For example, it has been found that when the outer diameters of a plurality of spiral blades are the same, the spiral blade at the tip receives the ground reaction force, and the other spiral blades hardly receive the ground reaction force. If the outer diameter is gradually increased from the spiral blade at the tip to the spiral blade located at the upper side, the ground reaction force of the spiral blade located at the lower side and the spiral blade located at the upper side may be received. It was found that the spiral blade located above receives the ground reaction force only in the area corresponding to the difference in area. That is, it was found that the spiral wing located above does not receive the ground reaction force at the portion overlapping the spiral wing located below, but receives the ground reaction force only at the portion protruding from the spiral wing located below.

Further, in the above foundation pile, the wall thickness of the steel pipe to be used is set in consideration of both the vertical load and the rotating torque applied to the pile head, but a large rotation applied when reaching the hard ground. It is unnecessary for vertical load to prevent deformation and failure due to torque,
At present, it was unavoidable to use thick steel pipes.

[0006] The requirement for the foundation pile is to use a thin-walled steel pipe to obtain a large supporting force, but the foundation piles proposed so far sufficiently satisfy this requirement. There was nothing.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a foundation pile that can obtain a large supporting force by using a thin-walled steel pipe.

[0008]

Means for Solving the Problems When a plurality of spiral blades are provided, the inventors of the present invention have conducted diligent research to find out the reason why the ground reaction force cannot be sufficiently received by each spiral blade. When the distance between the blades is set to be at least 1.5 times the outer diameter of the one spiral blade located on the lower side, between the one spiral blade located on the lower side and the other spiral blade located on the upper side. It has been found that the soil is sufficiently filled in and is compressed between the spiral blades, and the ground reaction force acts on the entire bottom surface of the other spiral blade located on the upper side, thereby generating a supporting force.

That is, the foundation pile of the present invention which achieves the above object is a foundation pile in which a plurality of spiral blades are arranged at a predetermined interval on the outer peripheral surface of the pile body, and the plurality of spiral blades are provided. The interval between the spiral blades in is set to be at least 1.5 times the outer diameter of the lower spiral blade so that each spiral blade receives the ground reaction force over the entire blade. Characterize.

When the outer diameters of the plurality of spiral blades do not change, the spacing between the spiral blades does not change, but when the outer diameters of the spiral blades gradually increase, the spacing between the spiral blades sequentially increases. When the outer diameter of the spiral blade increases, the supporting area also increases because the area that receives the ground reaction force increases, but the rotational torque that propels the pile body into the ground also increases.

In the above-mentioned foundation pile of the present invention, in order to promote the rotational propulsion of the pile body in the ground, for example, a drilling blade is provided at the tip of the pile body, and the tip of the pile body among the plurality of spiral blades is provided. A sand digging blade is provided on the lower surface of the start end of the spiral wing as a propulsion wing located on the side.

Further, the lower half of the thick and short pipe member having the inner diameter substantially equal to the outer diameter of the pile body and the rotation transmitting convex piece provided on the outer peripheral surface is provided on the pile head of the pile body. By inserting and fixing the pipe member as a deformation prevention pipe that also functions as a joint, even if a large rotational torque acts, deformation of the pile head is prevented without using a thick steel pipe. You can
Further, by providing the rotation transmitting convex piece on the outer peripheral surface of the pile head of the pile main body and providing the deformation preventing disk inside the pile head, it is possible to prevent the deformation of the pile head without using a thick steel pipe.

Further, another foundation pile of the present invention which achieves the above-mentioned object is provided with an excavating blade at the tip and a rotation transmitting convex portion on the outer peripheral surface of the pile head, the outer peripheral surface on the tip side of the pile main body, A spiral blade serving as a propulsive blade having a sand and sand cutting blade provided on the lower surface of the start end is provided outside the spiral blade on the outer peripheral surface of the intermediate portion of the pile main body separated by a distance of at least 1.5 times the outer diameter of the spiral blade. It is characterized in that a sub-spiral blade having a large diameter is provided, and the whole of each of the spiral blade and the sub-helical blade receives the ground reaction force.

In the above-mentioned another foundation pile of the present invention, the pile head of the pile main body is provided with a joint recess also for preventing deformation, and an upper pile body having a diameter larger than the diameter of the pile main body is provided through the joint recess. Connecting, providing a cross-shaped reinforcing rib inside the lower end of the upper pile body, providing a joint convex portion to be inserted into the joint concave portion at the lower end of the upper pile body, the joint concave portion and the joint convex portion in a screw type or spline type. Can be formed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partially omitted and partially cutaway side view showing a first embodiment of a foundation pile of the present invention, FIG. 2 is a bottom view of the foundation pile of FIG. 1, and FIG. 3 is a spiral wing. Fig. 4 is a perspective view of the earth and sand cutting blade provided on the lower surface of the starting end of Fig. 4, Fig. 4 is a sectional view of the pipe member provided on the pile head portion of the foundation pile of Fig. 1, and Fig. 5 is provided on the pile head portion of the foundation pile of Fig. 1. FIG. 6 is a sectional view of a deformation preventing disk, FIG. 6 is a partially omitted side view showing a second embodiment of the foundation pile of the present invention, and a partially cutaway side view thereof. FIG. 7 is an upper pile body connected to the foundation pile of FIG. FIG. 8 is a partial sectional view, FIG. 8 is a plan view of a reinforcing piece provided in the bottom portion of the upper pile body of FIG. 7, and FIGS. 9 and 10 are joint recesses of the foundation pile of FIG.
It is the side view which abbreviate | omitted and partially cut out which shows a joint convex part.

First, a first embodiment of the foundation pile of the present invention will be described with reference to FIGS. In the foundation pile of the present embodiment, a bottom plate 12 provided with a pair of excavating blades 11 is fixed to an opening end surface of a tip (lower end) of a pile body 10 made of a thin steel pipe by welding or the like, and the opening end surface is fixed. A spiral blade 14 as a single-rotation propulsion blade having an outer diameter approximately three times the pile diameter is fixed by welding or the like on the outer peripheral surface on the tip side, and further, from the spiral blade 15 at least 1. 5 times or more (almost 2.
A sub-spiral blade 15 having an outer diameter larger than that of the spiral blade 14 is fixed by welding or the like at a position of a distance T apart from the spiral blade 14.

On the lower surface of the starting end of the spiral wing 14, the pile main body 10 is
In order to promote the excavation, the earth and sand cutting blades 13a and 13b are provided so as to project downward at a predetermined inclination angle, as shown in detail in FIGS.

The pair of excavating blades 11 described above extend in the radial direction on the bottom plate 12, are formed in steps so that the height is high at the central portion of the bottom plate 12 and low at the peripheral portion, and the earth and sand on the lower end side of the pile body 10 are excavated. Soften. As shown in FIGS. 1 and 2, the pair of excavating blades 11 do not hang down with respect to the bottom plate 12, but are slightly inclined in mutually opposite directions.

Further, the above-mentioned earth and sand cutting blades 13a, 1
In 3b, the earth and sand cutting blade 13a having a longer blade length is arranged closer to the pile body 10, and the earth and sand cutting blade 13b having a shorter blade length is located away from the pile body 10 (spiral blade 14
Is arranged on the peripheral edge side of the pile) to assist the excavation by the spiral blades 14 and promote the rotational propulsion of the pile body 10 into the ground.

The spiral blade 14 and the sub-spiral blade 15 described above are also included.
The pitch angle of is changed depending on the N value of the ground and the like, but is set to 5 to 7 degrees, for example. Pitch angle 5 degrees to 7
If it is set larger than the degree, the amount of propulsion in one revolution becomes large in soft ground, but the spiral blade 14 and the auxiliary spiral blade 15 bite too much into the ground, and the auger device (propulsion device) is attached to the pile body 10. Extra torque acts from. In contrast,
When the pitch angle is set to be smaller than 5 to 7 degrees, the pile main body 10 does not receive an excessive torque and is smoothly propelled into the ground. However, when the ground becomes hard, the spiral blades 14 and the auxiliary spiral blades 15 are grounded. Sliding occurs without propelling inside. When the pitch angle is set to 5 degrees to 7 degrees, the pile body 10 does not bite too much in the soft ground, and does not slip even if the pile body 10 is propelled from the soft ground to the hard ground, and cuts into the hard ground. The earth and sand cutting blades 13a and 13b described above promote the cutting into the hard ground.

A pipe member 20 is fixed to the pile head of the pile main body 10, which functions as a joint pipe for adding a steel pipe and also functions as a deformation prevention pipe for preventing deformation of the pile head of the pile main body 10. It The pipe member 20 has an inner diameter substantially equal to the outer diameter of the pile body 10 and is made of a thick short steel pipe. The pile head of the pile body 10 is inserted into the lower half of the steel pipe and fixed by welding or the like. An auger device (not shown) is provided on the outer peripheral surface of the pipe member 20.
A pair of rotation transmitting convex portions 21 for transmitting a rotational force from the rotation driving unit of the above to the pile body 10 is provided. The lower end of the steel pipe 10a (see FIG. 4) that is added to the pile body 10 is fitted into the upper half of the pipe member 20 and fixed by welding or the like. A pipe member 20 is similarly provided on the upper end portion of the steel pipe 10a to be replenished, and the steel pipes are sequentially replenished through the pipe member 20.
Fixed.

According to the foundation pile of the present embodiment, like the conventional foundation pile, it is rotationally propelled into the ground by the auger device, and the excavating blade 11 and the earth and sand cutting blades 13a, 13b promote the rotational propulsion. At the time of this rotational propulsion, since the pipe member 20 is fixed to the pile head of the pile body 10 or the pile head of the steel pipe 10a that has been added, the pile member 10 or the like is approached from the soft ground to the hard ground by the auger device. Even when a large torque is applied, the pipe member 20 prevents the pile head from being deformed or broken, and therefore, the thick pile body 10 and the steel pipe 10a are not used so as to cope with the large torque that acts temporarily. It's done and it's economical. Pile body 10, steel pipe 10
The thickness of a is set based on the vertical load and the normal rotation torque. Further, when the steel pipe 10a is replenished, the work efficiency can be improved by using the pipe member 20.

In the course of rotationally propelling the foundation pile into the ground, the spiral blade 14 located on the tip side of the pile body 10 has a low boring N value of 1 to 2 and has a high water content in the stratum of clay or silt cohesive soil. Even if the sub-spiral blade 15 is in the idling state after entering, when the sub-helical blade 15 is harder than this formation and is in another stratum, the sub-helical blade 15 can obtain propulsive force to rotate and propel in the ground.

After the foundation pile is buried, a vertical load is applied to the pile body 10 and a ground reaction force is applied to the spiral blade 14 and the auxiliary spiral blade 15. That is, the distance T between the spiral blade 14 and the auxiliary spiral blade 15 is approximately 2.5 times the outer diameter of the spiral blade 14, and sufficient sand and sand enter between the spiral blade 14 and the auxiliary spiral blade 15 to load vertically. Compressed by the spiral wing 14 and the auxiliary spiral wing 15
Ground reaction force acts on each of them, and the spiral wing 14 and the sub spiral wing 1
5 provides a supporting force that is approximately equal to the vertical load.
The bottom plate 12 also receives the ground reaction force and exerts a supporting force.

Instead of the pipe member 20, a deformation preventing disk 22 may be fixed inside the pile head as shown in FIG. 5 to prevent deformation and breakage of the pile head. Next, Fig. 6
A second embodiment of the foundation pile of the present invention will be described with reference to FIGS.

6 to 8, the same parts as those in FIGS. 1 to 5 are designated by the same reference numerals and the description thereof will be omitted. When the number of floors of the building supported by the foundation piles is 4 or more, horizontal loads as well as vertical loads act on the upper ends of the foundation piles due to the influence of wind, etc. It has been pointed out that a large bending moment, which cannot be ignored, acts on a portion of 4, 5 m below the fixed portion (see JP 2001-64966 A).

The present embodiment is made in consideration of this point, and the pile body 10 and the steel pipe 10 supplemented to the upper end of the pile main body 10 or the upper end of the steel pipe 10a added to the pile main body 10 are provided.
A steel pipe 30 as an upper pile having an outer diameter 1.3 to 1.5 times the outer diameter of a is connected. As shown in FIGS. 7 and 8, a bottom plate 32 having a cross-shaped reinforcing rib 31 welded therein is fixed to the lower end opening of the steel pipe 30. A joint protrusion 33 is provided in the center of the bottom surface of the bottom plate 32.
The steel pipe 30 is connected by engaging 3 with the joint main body 10 or the joint recess 34 provided at the upper end of the steel pipe 10a which is replenished. For example, as shown in FIG.
The spline 33a is formed as shown in FIG. 3 or the male screw 33b is formed as shown in FIG. A vertical groove is formed on the inner peripheral surface of the joint recess 34 when the spline 33a is formed on the joint protrusion 33, and a female screw is formed when the male screw 33b is formed on the joint recess 33. On the outer peripheral surface of the joint concave portion 34, a pair of rotation transmitting convex portions 35 for transmitting the rotational force from the rotary driving portion of the auger device (not shown) to the pile body 10 or the like is provided. The joint recess 33 functions to prevent the pile main body 10 or the pile head of the steel pipe to which the pile main body 10 is added from being deformed or destroyed by the rotational torque.

According to the foundation pile of the above-mentioned embodiment, in addition to the same effect as the foundation pile of the above-mentioned first embodiment, it has sufficient strength against bending moment.

[0029]

As described above, according to the foundation pile of the present invention, the interval between the spiral blades is set to be at least 1.5 times the outer diameter of the spiral blades located below, and Since the wing is configured to receive the ground reaction force on the entire wing, sufficient supporting force can be obtained.

Further, the pile head of the pile main body has an inner diameter substantially equal to the outer diameter of the pile main body, and a rotation transmitting convex portion is provided on the outer peripheral surface,
If the lower half of the thick and short pipe member is inserted and fixed, it is possible to prevent the pile head from being deformed or damaged due to the rotating torque, and also when adding steel pipes to the pile body. The pipe member functions as a joint, and the efficiency of burying the foundation pile can be improved.

If the upper pile body having an outer diameter larger than the outer diameters of the pile body and the steel pipes connected to the pile body is connected to the upper end of the pile body or the steel pipe added to the pile body,
Even if the number of floors of the structure supported by the foundation pile increases and a bending moment acts on the foundation pile, there is no problem.
Moreover, since the upper pile body having a large diameter is provided only in the portion where a large bending moment acts, and the diameter of the entire foundation pile is not increased, there is no fear that the material cost will rise.

[Brief description of drawings]

FIG. 1 is a partially omitted and partially cutaway side view showing an embodiment of a foundation pile of the present invention.

FIG. 2 is a bottom view of the foundation pile of FIG.

3 is a perspective view of a sand and sand cutting blade provided on a lower surface of a starting end of the spiral blade shown in FIG. 1. FIG.

FIG. 4 is a cross-sectional view of a pipe member provided in a pile head portion of the foundation pile of FIG.

FIG. 5 is a cross-sectional view of a deformation prevention disk provided in the pile head portion of the foundation pile of FIG.

FIG. 6 is a partially omitted view showing another embodiment of the foundation pile of the present invention,
It is the side view which notched one part.

FIG. 7 is a partial cross-sectional view of an upper pile body connected to the foundation pile of FIG.

8 is a plan view of a reinforcing piece provided in the bottom portion of the upper pile body in FIG. 7. FIG.

FIG. 9 is a side view, partly omitted and partly cut, showing a joint recess and a joint protrusion of the foundation pile of FIG. 6;

10 is a partially omitted and partially cutaway side view showing a joint recess and a joint protrusion of the foundation pile of FIG.

[Explanation of symbols]

10 Pile Main Body 11 Excavation Blade 12 Bottom Plate 13a, 1
3b earth and sand cutting blade 14 spiral blade 15 secondary spiral blade 20 pipe member 21 rotation transmission convex portion 22 deformation preventing disk 30 steel pipe (upper pile body) 31 reinforcing rib 32 bottom plate 33 joint convex portion 33a spline 33b male screw 34 joint concave portion

Claims (6)

[Claims] 1. A foundation pile comprising a plurality of spiral blades arranged at a predetermined interval on the outer peripheral surface of a pile body, wherein the spacing between the spiral blades in the plurality of spiral blades is set to the lower side. A foundation pile, characterized in that at least 1.5 times the outer diameter of the positioned spiral blade is configured so that each spiral blade receives the ground reaction force as a whole. 2. The foundation pile according to claim 1, wherein an excavation blade is provided at a tip of the pile body, and a start end of a spiral blade located on the tip side of the pile body among the plurality of spiral blades. A foundation pile, characterized in that a bottom surface of the pile body is provided with a sand and sand cutting blade, and a rotation transmitting convex piece is provided on an outer peripheral surface of the pile head of the pile body. 3. The foundation pile according to claim 2, wherein the pile head of the pile main body has an inner diameter substantially equal to the outer diameter of the pile main body, and the rotation transmitting convex piece is provided on the outer peripheral surface thereof. The lower half of a thick and short pipe member is fitted and fixed, and the pipe member is used as a deformation preventing pipe which also serves as a joint.
Foundation pile. 4. The foundation pile according to claim 2, wherein a rotation transmitting convex piece is provided on an outer peripheral surface of the pile head of the pile main body, and a deformation preventing disk is provided inside the pile head. Pile. 5. An excavation blade having an excavating blade at the tip and a rotation transmitting convex portion on the outer peripheral surface of the pile head, and an outer peripheral surface on the distal end side of the pile main body provided with a sand biting blade on the lower surface of the starting end. A spiral blade is provided, and a sub-spiral blade having an outer diameter larger than that of the spiral blade is provided on the outer peripheral surface of the pile main body, which is separated upward by a distance of at least 1.5 times the outer diameter of the spiral blade. A foundation pile, characterized in that it is constructed so as to receive the ground reaction force over each wing of the foundation pile. 6. The foundation pile according to claim 5, wherein the pile head of the pile main body is provided with a joint recess also serving as deformation prevention.
An upper pile body having a diameter larger than the diameter of the pile body is connected through the joint recess, a cross-shaped reinforcing rib is provided inside the lower end of the upper pile body, and the upper pile body is fitted into the joint recess at the lower end. A foundation pile, characterized in that a joint convex portion is provided, and the joint concave portion and the joint convex portion are formed in a screw type or a spline type.