JPH07189249A - Method of burying construction of inverted conical-shaped multi-blade steel pipe pile - Google Patents

Abstract

PURPOSE:To increase bearing power, and to enable non-earth removing execution. CONSTITUTION:An inverted conical-shaped multi-blade steel pipe, in which spiral blades 6a-6c having large diameters extending over approximately one winding are mounted separately on the outer circumference of a pile body 1, in which a bottom plate 2, excavating edges 3, 4 and a ground exhaust nozzle 5 are installed at a lower end, and the outside diameters of these spiral blades 6a-6c are increased at a fixed ratio toward an upper section, is used, the multi- blade steel pipe is pushed against the ground and soil and sand are excavated by turning, the spiral blades are intruded so as to be screwed, cement milk is impregnated while rotating and propelling the multi-blade steel pipe as using the yield strength of soil as reaction, and the multi-blade steel pipe is screwed and buried in non-earth removing. A bearing layer 7 by the mixing of soil and sand and cement milk is formed spirally on the side face of a pile.

Description

Detailed Description of the Invention

[0001]

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

[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, there have been conventionally used modified friction piles, soil cement improved piles,
Pile foundations such as small-diameter concrete piles and floating foundation construction methods, commonly known as solid foundations, 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 have received the consolidation of the ground surface, and the deformed friction piles and soil cement improved piles with the same diameter from the ground surface of the extremely soft layer that contracts due to water level change and upper load , 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 in that the surface area of the piles 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. It is an object of the present invention to provide a burying method using a novel conical multi-blade steel pipe friction pile that can be used.

[0006]

The structure of the present invention for achieving the above object will be described with reference to the drawings corresponding to the embodiments. , Bottom plate 2, digging blades 3, 4 and grout jet holes 5, 5
In addition, the spiral wing 6a-6c for screwing is provided on the outer circumference of the pile main body 1 at substantially equal intervals in the lengthwise direction thereof and having a diameter that is at least twice the outer diameter of the pile main body 1 and extends over approximately one turn. An inverted conical multi-blade steel pipe pile, in which the outer diameters of the protruding and spaced apart spiral blades 6a to 6c are increased at a constant ratio according to the upward direction, is pressed and rotated on the soft ground to rotate the grout. Cement milk is injected from the ejection holes 5 and 5, and the soil and sand in the lower part of the pile body 1 are mixed to consolidate the side surface of the pile, and the spiral blades 6a to 6c are bitten into the ground so as to be bitten, It is characterized in that the pile body 1 is rotatably propelled and buried by using the yield strength of soil as a reaction force, and the peripheral support layer 7 is formed on the side surface of the pile body 1 by mixing spiral soil and sand and cement milk.

Further, according to the burying method of claim 2, the bottom plate 2, the excavating blades 3, 4 and the grout jet holes 5, 5 are provided at the lower end of the pile body 1.
In addition, the screw main blades 6a to 6c are provided on the outer circumference of the pile main body 1 at substantially equal intervals in the lengthwise direction thereof, and the screwing spiral blades 6a to 6c having a diameter not less than twice the outer diameter of the pile main body. The outer diameters of the spiral blades 6a to 6c that are installed and are separated from each other,
Inverse conical multi-blade steel pipe piles with a large diameter at a constant ratio according to the upper part are pressed and rotated on soft ground, cement milk is injected from the grout injection holes 5, 5, and the soil at the bottom of the pile body 1 While mixing cement milk and consolidating it on the side surface of the pile, the spiral blades 6a to 6c are bitten into the ground so as to be screwed, and the pile body 1 is rotatably propelled to be buried by using the proof strength of the soil as a reaction force, and the steel pipe pile is installed. After the penetration into the predetermined depth of, while moving the steel pipe pile up and down while pouring cement milk,
A peripheral support layer 7 is formed on the side surface of the pile body 1 by mixing earth and sand and cement milk, and a soil cement mass 8 having a substantially inverted conical shape is formed between the spiral blade 6c and the lower end portion of the pile. It is a thing.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show an embodiment of a steel pipe pile used in the present invention, and FIG. 3 shows a state of the buried construction.

1 and 2, reference numeral 1 denotes a steel pipe pile main body, and a bottom plate 2 is fixed to the lower end of the pile main body.
At the lower end with a digging blade 3 which protrudes downward from the bottom plate 2
And a digging blade 4 protruding and inclined to the side surface of the pile body 1, and further, the bottom plate 2 is provided with grout jet holes 5 and 5 projecting downward.

Further, a plurality of spiral blades 6a to 6c 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 6a to 6c is at least twice the outer diameter of the pile body 1. Moreover, the pitch L of each spiral blade 6a-6c is the same, and, for example, it is a small pitch of 1/2 of the pile main body 1. Furthermore, the spiral blades 6a to 6c are the lowermost spiral blades 5 respectively.
From a to the upper ones 6a and 6c, the diameters of the spiral blades 6a to 6c are successively increased at a fixed ratio, and the line a connecting the outer ends of the spiral blades 6a to 6c is formed into an upward conical inverted cone shape. There is. In addition, the interval between the spiral blades 6a to 6c is preferably set to a length that is a multiple of the pitch 1 of the spiral blades.

In the illustrated embodiment, one pile body 1 is provided with three spiral blades 6a to 6c, but the number of spiral blades can be appropriately increased or decreased. 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 multi-blade steel pipe pile. First, a rotary pushing drive device (not shown) is attached to the upper end of the pile body 1, and the steel pipe pile is driven to rotate so that it is screwed into the ground, and cement milk is injected from the grout jet holes 5 and 5 while pushing it in. I will go there.

As a result, the soil at the tip of the pile is excavated, softened and fluidized by the action of the excavating blades 3 and 4 at the lower end, and the penetration of the pile becomes easy. Then, the spiral blades 6a protrudingly provided on the outer peripheral surface of the pile body 1 are made to bite into the excavated earth and sand and the ground, and the composition of the soil is used as a reaction force to be rotationally propelled. in this case,
The propulsion length for each rotation of the steel pipe pile is the pitch L of the spiral blade 6a.
Is almost equal to the length of.

Further, in this case, since cement milk is injected from the grout jet holes 5 and 5, the excavated and softened earth and sand and cement milk are mixed by the excavating blades 3 and 4, and the mixed earth and sand are penetrated by the penetration of the pile body. The mixed volume of piles will be compressed to the side of the piles, and therefore the piles will penetrate the ground surface without discharging soil, and as shown in FIG. 1 periphery and spiral wing 6
Cement milk is mixed with the excavated soil, compacted and filled in the rotation trajectory of a, and the spiral peripheral support layer 7 is continuously formed.

As the steel pipe pile is advanced and penetrated, the spiral blades 6b and 6c provided above also bite into the ground one after another and are rotationally promoted in the same manner as above. in this case,
Since these spiral blades 6b and 6c are on the spiral locus b which is continuous with the spiral blade 6a at the lower end, the bite into the ground is good and the rotational propulsion is facilitated.

As described above, in the steel pipe pile burying of the present invention,
Since the pile is penetrated by the rotation and propelling of the spiral blades 6a to 6c, the burying of the pile is carried out without soil discharge and the cement milk is injected while the pile is rotated and propelled, so that the ground around the pile is consolidated. Not only that, but the peripheral supporting layer 7 is continuously formed in a spiral shape by mixing the earth and sand and the cement milk. In the buried steel pipe pile, since the spiral blades 6a to 6c that are spaced apart are gradually increased in diameter as they become the upper ones, the spiral cone blades having an inverted conical shape that spreads upward as a whole. Therefore, not only the pressure in the vertical direction by the spiral blades 6a to 6b but also the wedge effect by the inverse cone shape works, and the effect of the bearing pressure and the cement milk in the diagonal direction further causes the effect of adhesion to the ground. Will be added, and a large bearing capacity will be obtained.

Next, another embodiment of the method of the present invention will be described. In this embodiment, after the steel pipe pile has penetrated to a predetermined depth by the above-described construction method, the steel pipe pile is rotated while injecting cement milk, if necessary, as shown in FIG.
For example, the steel pipe pile is repeatedly moved up and down while repeating normal rotation and reverse rotation. As a result, cement milk and earth and sand are agitated by the spiral blades 6a to 6c to become soil cement, and a soil cement mass 8 having a substantially inverted conical columnar shape is formed from the lower end of the steel pipe pile to above the upper spiral blade 6c. By hardening the soil cement, the effect of adhering to the soil on the side surface is developed, and in addition to the wedge effect of the inverted conical column shape, stronger friction supporting force and pullout resistance force are exhibited.

As described above, according to the present invention, when the burying depth of the steel pipe pile becomes long, other piles, for example, the generally used wingless steel pipe upper piles are added to this steel pipe pile. Connect and continue burial. In the present invention, in order to further improve the effect, the steel pipe pile can be buried in a stable deep stratum having a strength of a certain value or more, avoiding the end consolidation ground whose conical multi-blade portion is close to the ground surface. desirable. By doing so, in addition to the pressure bearing effect of the spiral blades 6a to 6c having a large span, the conical wedge effect of each spiral blade 6a to 6c acts on the stratum, and the composite friction and wedge effect are combined and supported. Power will be obtained.

[0019]

As described above, according to the present invention, a large-diameter screw-in spiral blade is provided on the outer periphery of a pile main body having an excavating blade and a grout injection hole at the lower end thereof. Using a steel pipe pile with a large diameter as it goes to the upper part, it was twisted into the ground by rotary pushing and cement milk was injected from the grout injection hole, so the pile was rotated with a slight pressing force. Just burying can be done efficiently and without soil.

Further, the steel pipe pile has a bearing capacity of each spiral blade, a wedge effect in the ground due to the inverted conical shape of each spiral blade, and in addition to the entire circumference of the pile and the periphery by mixing spiral sand and cement milk. By forming a support layer, a great supporting force can be obtained, and it is particularly excellent as a foundation pile construction method for a house or the like constructed on soft ground.

In addition to the above effects, in the method of claim 2, an inverted conical pillar-shaped soil cement lump is formed integrally with the steel pipe pile by mixing cement milk and earth and sand around the steel pipe pile. The adhesion effect with the wedge and the wedge effect are synergistic to add more cooperative friction supporting force and pullout resistance force.

[Brief description of drawings]

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

FIG. 2 is a bottom view of the same.

FIG. 3 is an explanatory view of the same buried state.

[Explanation of symbols]

 1 Pile main body 2 Bottom plate 3,4 Excavation blade 5 Grout ejection hole 6a-6c Spiral blade 7 Peripheral support layer 8 Soil cement block

[Procedure amendment]

[Submission date] June 16, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

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

FIG. 2 is a bottom view of the same.

FIG. 3 is a side sectional view showing an example of construction of the method of the present invention.

FIG. 4 is a side sectional view showing another construction example.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Next, another embodiment of the method of the present invention will be described. In this embodiment, after the steel pipe pile has penetrated to a predetermined depth by the above-mentioned construction method, the steel pipe pile is rotated while injecting cement milk, if necessary, as shown in FIG.
For example, the steel pipe pile is repeatedly moved up and down while repeating normal rotation and reverse rotation. As a result, cement milk and earth and sand are agitated by the spiral blades 6a to 6c to become soil cement, and a soil cement mass 8 having a substantially inverted conical columnar shape is formed from the lower end of the steel pipe pile to above the upper spiral blade 6c. By hardening the soil cement, the effect of adhering to the soil on the side surface is developed, and in addition to the wedge effect of the inverted conical column shape, stronger friction supporting force and pullout resistance force are exhibited.

Claims (2)

[Claims] 1. A bottom plate, a digging blade, and a grout jet hole are provided at the lower end of the pile body, and the outer circumference of the pile body is approximately twice or more the outer diameter of the pile body at substantially equal intervals in the length direction. A spiral blade for screwing that spans almost one turn with the diameter of
And, the outer diameter of the spiral blades separated from each other, a multi-blade steel pipe pile of an inverted cone shape in which the outer diameter of the spiral blades is increased at a constant ratio as it goes to the upper part,
Press and rotate on soft ground, inject cement milk from the grout injection hole, mix the soil and sand at the bottom of the pile body and cement milk on the side of the pile, while screwing the spiral blade into the ground. , Reverse cone-shaped multi-blade, characterized in that the pile body is rotatably propelled and buried by using the yield strength of soil as a reaction force, and a peripheral support layer is formed on the side surface of the pile body by mixing spiral soil and sand and cement milk. Method of burying steel pipe piles. 2. A bottom plate, an excavating blade, and a grout jet hole are provided at the lower end of the pile body, and the outer circumference of the pile body is approximately twice the outer diameter of the pile body at substantially equal intervals in the length direction. A spiral blade for screwing that spans almost one turn with the diameter of
And, the outer diameter of the spiral blades separated from each other, a multi-blade steel pipe pile of an inverted cone shape in which the outer diameter of the spiral blades is increased at a constant ratio as it goes to the upper part,
Press and rotate on soft ground, inject cement milk from the grout injection hole, mix the soil and sand at the bottom of the pile body and cement milk on the side of the pile, while screwing the spiral blade into the ground. , The pile body is rotatably propelled and buried by using the yield strength of the soil as a reaction force, and after the steel pipe pile has penetrated to a predetermined depth, the steel pipe pile is vertically moved while pouring cement milk, Inverse cone-shaped multi-concentrate is characterized by forming a peripheral support layer by mixing soil and cement milk on the side of the body, and forming a substantially reverse cone-shaped soil cement mass between the spiral blade and the lower end of the pile. Method for burying wing steel pipe piles.