JP2691831B2 - Conical multi-blade steel pipe friction pile and its burying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conical multiblade steel pipe friction pile suitable for soft ground and a method for burying it.

[0002]

2. Description of the Related Art Large cities in Japan are concentrated in alluvial plains developed around rivers, and the ground surface has many extremely soft layers that have not been particularly consolidated. Due to consolidation, there is an alluvium that is not a pile support layer but is a little stronger than the ground surface. The support layer that supports alluvial piles extends to more than 60 m deep and was built in the alluvial plain. Economically, the foundation of low-rise buildings in the city
Long support piles are not possible, and over the years, subsidence and deformation have occurred due to uneven subsidence of the ground, etc., and accidents causing building troubles have frequently occurred in alluvial cities.

As a method for improving the surface layer of such soft ground, a pile foundation such as a deformed friction pile, a soil cement improved pile, and a small diameter concrete pile, and a floating foundation construction method commonly called a solid foundation are used.

[0004]

However, these pile foundation methods are mainly used for constructions having a large road width and a large construction site. Construction machinery and equipment and pile materials are
It can not be carried in on narrow roads and narrow sites, and construction and use is difficult. In addition, none of these basic construction methods are not subjected to consolidation of the ground surface, contraction due to water level change, upper load, deformed friction pile with the same diameter from the ground surface of the extremely soft layer, soil cement improved pile , Small-diameter concrete piles, etc. are constructed with pile lengths that extend the same diameter up to a certain depth stratum where soil friction force can be taken. Therefore, these piles have a problem that the pile surface area additionally receives the dense load of the ground that contracts due to the water level change and the upper load of the extremely soft layer on the ground surface other than the building load.

The present invention improves the drawbacks of the conventional construction method, and in particular, it is applied to the alluvial ground in the city, has extra strength and bearing capacity, and can be easily applied to the deep ground without unloading soil. The present invention aims to provide a new conical multi-blade steel pipe friction pile and a burying method therefor.

[0006]

The structure of the present invention for achieving the above object will be described with reference to the drawings corresponding to the embodiments. The conical multiblade steel pipe friction pile according to claim 1 is a steel pipe. A bottom plate and an excavating blade are provided at the lower end of the pile main body, and the outer peripheral surface of the steel pipe pile main body has a diameter equal to or more than twice the outer diameter of the steel pipe pile main body 1 at substantially equal intervals in the length direction. A large number of screwed spiral blades 5a, 5c extending over approximately one turn
The respective spiral blades 5a to 5c are made to protrude, and the outer diameters of the spiral blades 5a to 5c are gradually increased at a constant ratio according to the outer diameter from the lowermost one to the upper one. Of the spiral blade 5a.
The interval of ~ 5c is set to a length that is a multiple of the pitch of the spiral blades 5a-5c.

The conical multi-blade steel pipe friction pile embedding method according to claim 2 uses the conical multi-blade steel pipe friction pile according to claim 1, which is pressed against a soft ground to rotate it, The sand and sand at the bottom are softened by the excavating blades 3 and 4, and spiral wing is screwed into the unexcavated soil on the side of the pile, and the pile body is rotated and propelled using the proof strength of the soil as a reaction force to reach the soil portion. The spiral blades 5a to 5c whose blade diameters are increased in accordance with
While excavating the softened earth and sand to the side of the pile body to consolidate the earth and sand, screw it into the ground without discharging, and then add another wingless upper pile to the upper end of this conical multiblade steel pipe friction pile. The feature is that the conical multi-blade steel pipe friction pile is buried in a stable deep stratum by proceeding with the burying.

[0008]

The present invention is configured as described above, and when burying a conical multiblade steel pipe friction pile (hereinafter referred to as steel pipe pile), a rotary pushing drive device (not shown) is provided at the upper end of the pile body 1. The pile main body 1 is attached and driven, and the pile main body 1 is pressed against the ground while being rotated so as to be screwed in. As a result, the excavating blades 3 and 4 at the lower end excavate and soften the earth and sand at the tip of the pile, and screw-in spiral blades 5a to 5a protruding from the outer peripheral surface of the pile body.
d digs into the excavated earth and sand, rotates and propels it by using the composition of the earth as a reaction force, and does not discharge the earth and sand to the ground, and the steel pipe pile is screwed in and buried.

In this case, the soil excavated and softened at the tip of the pile is entirely pressed against the outside of the pile, and the ground around the pile is compacted. In the buried steel pipe pile, since the spiral blades 5a to 5c that are spaced apart are gradually increasing in diameter as they become the upper ones, a conical spiral blade that spreads upwards is formed as a whole. Because you will
Not only the vertical bearing force by the spiral blades 5a to 5c,
The wedge effect due to the conical shape works, and the supporting force in the oblique direction is also added, so that a large supporting force can be obtained.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a steel pipe pile of the present invention. FIG. 1 shows a pile body made of steel pipe, and a bottom plate 2 is provided at the lower end of the pile body so that the lower end of the pile body is closed. Then, at the lower end of the pile main body 1, an excavation blade 3 protruding downward from the bottom plate 2 and an excavation blade 4 projecting and inclined to the side surface of the pile main body 1 are provided.

Further, a plurality of spiral blades 5a to 5c are formed on the outer periphery of the pile body 1 from the lower end portion thereof to the upper side at substantially equal intervals and continuously formed over almost one turn. The outer diameter of each of the spiral blades 5a to 5c is twice or more the outer diameter of the pile body 1. The pitch 1 of each of the spiral blades 5a to 5c is the same, and moreover, it is a small pitch of about half of the pile main body 1. Furthermore, each spiral blade 5a-5c is the bottom spiral blade 5
From a to the upper ones 5b and 5c, the diameters are successively increased at a constant ratio, and the line a connecting the outer ends of the spiral blades 5a to 5c has an upward-opening conical shape. . The interval between the spiral blades 5a to 5c is set to a length that is a multiple of the pitch 1 of the spiral blade.

In the illustrated embodiment, one pile body 1 is provided with three spiral blades 5a to 5c, but the number of spiral blades can be appropriately increased. When the burying depth of a steel pipe pile becomes long, another pile is connected to this steel pipe pile before use.

The method of the present invention is carried out by using the above-mentioned conical multiblade steel pipe friction pile. First, a rotary pushing drive device (not shown) is attached to the upper end of the pile body 1, and the pile body 1 is pushed into the ground while being rotated by the drive.

As a result, the sand and sand b at the tip of the pile are excavated, softened and fluidized by the action of the digging blades 3 and 4 at the lower end, and the pile sinks easily. Then, the spiral blade 5a having a large wing width and a short pitch protrudingly provided on the outer peripheral surface of the pile body 1 bites into the excavated earth and sand b and the ground A, and the composition of the soil is rotationally propelled as a reaction force and fluidized. The steel pipe pile is twisted into the ground while pushing the soil b toward the side of the pile and compressing it. In this case, the propulsion length per one rotation of the steel pipe pile is almost the same as the length of the pitch 1 of the spiral blade 5a. Spiral piles 5b to 5c provided above as the steel pipe piles are promoted and settled
Will also bite into the ground A one after another and will rotate and propel equally. In this case, since the spiral blades 5b to 5c are on the spiral axis mark c continuous with the spiral blade 5a at the lower end, the ground A
The bite into it is also good, and rotation propulsion is easily performed.

Therefore, in the steel pipe pile of the present invention, since the pile is settled by the rotational propelling of the spiral blades 5a to 5c, the pile is buried without waste and the ground around the pile is consolidated. Become. In the buried steel pipe pile, since the spiral blades 5a to 5c that are spaced apart are gradually increasing in diameter as they become the upper ones, a conical spiral blade that spreads upwards is formed as a whole. The spiral wing 5a
Not only the vertical bearing force due to .about.5c but also the wedge effect due to the conical shape works, and the bearing force in the oblique direction is also added, so that a large supporting force can be obtained.

As described above, according to the present invention, when the burying depth of the steel pipe pile becomes long, another pile, for example, a generally used wingless steel pipe upper pile is added to this steel pipe pile. Connect and continue burial. In order to further enhance the effect, the steel pipe pile of the present invention can avoid the final consolidation ground whose conical other wings are close to the ground surface, and can be buried in a stable deep stratum having a strength of a certain value or more. desirable. By doing so, in addition to the pressure bearing effect of the spiral blades 5a to 5c having large spans, the conical wedge effect of the entire spiral blades 5a to 5c acts on the formation, resulting in greater frictional force and wedge effect. It will be possible to obtain a composite and supportive force.

[0017]

As described above, according to the steel pipe pile of the present invention, a large number of spiral blades are projected along the lengthwise direction on the outer periphery of the pile main body having the drilling blade at the lower end thereof. Since it was installed, excavation of soil and sand by the excavating blade, softening, fluidization, and biting of the spiral wing into the soil and soil, it is possible to bury it without discharging soil by rotating the pile with a slight pressing force. .

In particular, the pitch of each spiral blade is 2 times the diameter of the pile body.
In addition to being a small pitch suitable for rotational propulsion of 1/10 and the interval between the spiral blades being a multiple of the pitch of the spiral blades, in addition to facilitating the penetration of the pile by rotation, Since each spiral blade located above the lowermost part travels along the rotation trajectory of the spiral blade located at the lower part, the bite resistance to the ground is greatly reduced, and the rotation of the pile is reduced with less power. Can be promoted.

Since the spiral blades have a large diameter and a wide width and are provided in large numbers, not only a large vertical supporting force corresponding to the area of the entire spiral blade is obtained, but also each spiral blade is arranged from the bottom to the top. The diameters of the spiral blades are gradually increased at a fixed ratio, and the line connecting the outer ends of the spiral blades is shaped like a cone that expands upward, so the wedge effect in the ground is exerted by the cone shape. Therefore, the supporting force in the oblique direction is also added, and a large supporting force can be obtained as a whole. And since the structure is simple, it can be manufactured at low cost.

The burial can be carried out by simply rotating and pressing the steel pipe pile directly into the ground, and can be carried out extremely deeply with no noise, no vibration, and no soil unloading, especially on soft ground. It is an excellent method for constructing foundation piles for houses, etc.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a steel pipe pile of the present invention.

FIG. 2 is a bottom view of the same.

FIG. 3 is a vertical sectional view of the lower portion.

FIG. 4 is an explanatory diagram of the same embedded state.

[Explanation of symbols]

 1 Pile main body 2 Bottom plate 3,4 Excavating blade 5a-5c Each screw blade for screwing

Claims (2)

(57) [Claims] 1. A bottom plate and a digging blade are provided at the lower end of a steel pipe pile main body, and the outer peripheral surface of the steel pipe pile main body is arranged at substantially equal intervals in the lengthwise direction thereof and has an outer diameter of 2 mm. A large number of screw-type spiral blades with a diameter of more than twice the diameter are projected, and each spiral blade has an outer diameter that varies from the bottom to the top, with a fixed ratio. It is characterized in that the diameter of each of the spiral blades is set to be approximately one half of the diameter of the pile main body, and the interval between the spiral blades is set to a length that is a multiple of the pitch of the spiral blades. Conical multi-blade steel pipe friction pile. 2. A bottom plate and a drilling blade are provided at the lower end of the steel pipe pile main body, and the outer peripheral surface of the steel pipe pile main body is arranged at substantially equal intervals in the length direction thereof, and has an outer diameter of 2 mm. A large number of screw-type spiral blades with a diameter of more than twice the diameter are projected, and each spiral blade has an outer diameter that varies from the bottom to the top, with a fixed ratio. The conical multi-blade steel pipe friction with the diameter gradually increased and the pitch of the spiral blade was set to be approximately half the diameter of the pile body, and the interval between the spiral blades was set to a multiple of the pitch of the spiral blade. The pile is pressed against the soft ground and rotated, the soil at the bottom of the pile body is softened by the excavating blade, the spiral wing is screwed into the unexcavated soil on the side of the pile, and the yield strength of the soil is used as the reaction force. The body is rotated and propelled, and the spiral blades whose diameters are increased as they go to the upper part are successively bitten into the earth and sand, While excavating the softened earth and sand to the side of the pile body to consolidate the earth and sand, screw it into the ground without discharging, and then add another wingless upper pile to the upper end of this conical multiblade steel pipe friction pile. A method for burying a conical multi-blade steel pipe friction pile, characterized by burying the conical multi-blade steel pipe friction pile in a deep stable formation.