JPH05280048A - Method for forming widened bottom part of pile - Google Patents

Abstract

PURPOSE:To form a widened bottom part of a pile presenting a large drawout resistance underground in simple structure and with good performance of executing works. CONSTITUTION:The tops and bottoms of a plurality of reinforcing members 8 consisting of a band, etc., and arranged cylindrically are fixed by ring-form metal pieces 7a, 7b to form a cylindrical reinforcement 6. The metal piece 7a at the over-side of this reinforcement 6 is welded fast to the tip of an existing pile. This pile 1 is driven by pressure into the ground 3, and in the condition that the reinforcement 6 has reached the wide excavated part at the foremost, the pile 1 is further driven to give a thrust force so that the reinforcement 6 deforms into barrel form. In this condition with the reinforcement 6 deformed, a hardening material 4 such as concrete is placed fully, and a widened bottom part 5 is completed with solidifying of this hardening material 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing an expanded pile bottom portion used as a foundation pile.

[0002]

2. Description of the Related Art Construction of prefabricated piles in cities is often performed by various embedded pile construction methods for the purpose of reducing noise and vibration, and reliable load transmission to the ground is performed at the pile tips. Therefore, an expanded bottom portion is often provided.

As for the method of installing the piles, referring to FIG. 5, taking an example of the hollow excavation method, an auger is inserted into the hollow pile 1,
While excavating the ground 3 near the tip of the pile, the pile 1 is press-fitted to increase the diameter of the auger at a predetermined depth to expand the excavation section 2
Is formed. The enlarged excavation part 2 is filled with a hardening material 4 such as concrete or cement milk, and an enlarged bottom part 5 is formed.

Also, for example, Japanese Patent Laid-Open No. 61-122324.
The gazette describes a construction method in which a cloth cylinder is attached to the tip of an existing pile, the pile is installed at a predetermined depth in the ground by the embedded pile method, and then the hardening cylinder is filled into the cloth cylinder. There is. Further, in Japanese Patent Laid-Open No. 61-122323, a rebar cage is attached to the tip of a prefabricated pile, and a bar and a rod provided in the axial direction in the rebar cage are provided with a pin and a movable pin in a rod shape. A pile construction method is described in which a reinforcing material is attached and the core rod hits the bottom of the excavation to rotate the reinforcing material around the pin and spread in the horizontal direction.

[0005]

Since the bottom expansion part is made of concrete, cement milk, soil cement, etc., it has sufficient strength under the action of compressive force for vertical supporting force. Since the tensile strength is low,
No pull-out resistance can be expected.

[0006] In the conventional embedded pile, the pull-out resistance is expected to be the peripheral resistance, but in order to increase the pull-out resistance with the same pile length, it is necessary to increase the pile diameter, which is excessive with respect to the vertical bearing capacity. The pile diameter may be different, which is not always rational.

Further, in the method described in Japanese Patent Laid-Open No. 61-122323, the expanded bottom portion is reinforced by the reinforcing bar that horizontally spreads at the reinforcing bar cage and the enlarged excavation portion, but a large number of reinforcements are expected in order to expect a reinforcing effect. When the material is provided, the number of pin joints becomes extremely large, which is not only difficult to manufacture, but also the respective members interfere with each other, which may make it difficult to operate. In addition, the fracture property when resisting pull-out force at the expanded bottom part is cone fracture in which cracks occur diagonally upward from the tip of the existing pile to the outer periphery, whereas reinforcement with a rod-shaped reinforcement placed horizontally In the form, sufficient pull-out resistance cannot be obtained.

The present invention is intended to solve the above-mentioned problems in the prior art.

[0009]

The outline of the present invention will be described below with reference to the reference numerals in the drawings corresponding to the embodiments.

In the present invention, the prefabricated pile 1 installed in the ground
In order to reinforce the expanded bottom portion 5, a plurality of bar-shaped or strip-shaped reinforcing members 8 extending in the vertical direction are arranged in a cylindrical shape, and the upper and lower sides of each reinforcing member 8 are ring-shaped metal objects 7a, 7 for shape retention.
A cylindrical reinforcing member 6 fixed to b is used. As the reinforcing material 8, for example, a reinforcing bar or a strip plate is used.

When press-fitting the pile 1 into the ground, a cylindrical reinforcing member 6 is fixed to the tip of the pile 1 by welding, bolting or the like and press-fitting into the ground while maintaining a cylindrical shape. When the tip of the pile 1 reaches the expanded bottom portion 5 formation position (enlarged excavation portion 2), an axial compressive force is applied to the cylindrical reinforcing body 6 to deform it into a barrel shape so as to be convex outward in the diameter direction. If there is a possibility that the reinforcing member 8 is deformed inward in the diametrical direction depending on how to apply the axial force, a deformation restraining member may be attached to the inside of the reinforcing member 8 arranged in a cylindrical shape in advance, or the outside may be deformed. This can be dealt with by giving an initial deformation for inducing the deformation to the.

In a state where the cylindrical reinforcing body 6 at the tip of the pile 1 is deformed, the hardening material 4 such as filled concrete or cement milk is solidified, so that the cylindrical reinforcing body 6 deformed into a barrel shape is obtained. The expanded bottom portion 5 has is completed. The hardening material 4 is not limited to being filled after the cylindrical reinforcing member 6 is deformed, but may be filled in advance in the form of soil cement or the like when excavating.

Further, in the present invention, when the pile 1 is press-fitted by the intermediate excavation method, it is necessary to use a hollow pile such as a steel pipe pile or a composite pile, but the present invention is not limited to this, and in various embedded pile construction methods, It can also be applied to precast concrete piles.

[0014]

The present invention is to reinforce the bottom expanding part 5 so that the pulling force can be transmitted from the pile 1 to the bottom expanding part 5, so that the final shape of the cylindrical reinforcing member 6 is barrel-shaped to form a bottom expanding part reinforcing work. By enclosing the hardened material 4 such as concrete, cement milk, or soil cement in the expanded bottom portion 5 and applying a strong constraint, the tensile strength of the expanded bottom portion 5 is increased.

However, if the shape of the bottom expanding reinforcement is barrel-shaped from the beginning, it will be larger than the pile shaft diameter, and the press-fitting process until the pile 1 is installed at a predetermined position will be hindered.
It is necessary to have a cylindrical shape having substantially the same diameter as.

Therefore, when the tip portion of the pile 1 reaches the position where the expanded bottom portion 5 is formed, an axial compressive force is applied to the cylindrical reinforcing member 6 to remove the ring-shaped metal member 7a (or 7b) on one side. By moving in the direction of one ring-shaped metal 7b (or 7a), the reinforcing material 8 whose both ends are fixed to the ring-shaped metal 7a, 7b is forcibly elastically or plastically deformed into a barrel-shaped final shape. Is set.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated embodiment will be described below.

FIGS. 1 (a) to 1 (d) continuously show the construction procedure in one embodiment of the present invention.

In this embodiment, as shown in FIG. 2, a cylindrical reinforcing member is formed by fixing the upper and lower sides of a reinforcing member 8 composed of a plurality of cylindrically arranged strips with ring-shaped metal fittings 7a and 7b for holding a shape. The upper ring-shaped metal 7a is welded to the tip of the steel pipe pile 1 using the body 6.

As shown in FIG. 1 (a), the cylindrical reinforcing member 6 has a cylindrical shape when the pile 1 is press-fitted and has a diameter substantially the same as that of the shaft portion of the pile 1, so an auger should be used. Therefore, the ground resistance is also small. FIG. 1 (b) shows a state in which the cylindrical reinforcing member 6 at the tip has reached a predetermined expanding portion 5 forming position.

Next, as shown in FIG. 1 (c), the steel pipe pile 1
Is further pressed vertically downward, the cylindrical reinforcing member 6 is deformed into a barrel shape by the reaction force from the ground 3. As shown in the figure, the cylindrical reinforcing member 6 forcibly deforms the shape into a barrel shape, and therefore the arrangement shape that effectively reinforces the hardening material 4 in the enlarged excavation portion 2 in which the auger 10 is expanded and excavated. Becomes
In this case, if the reinforcing material 8 made of a strip or the like is initially deformed by a method of making the diameter of the lower ring-shaped metal piece 7b slightly smaller than the diameter of the upper ring-shaped metal piece 7a, The material 8 can be easily deformed outward.

Thereafter, as shown in FIG. 1 (d), a hardened material 4 such as concrete or cement milk is filled in this portion to form an expanded bottom portion 5, and the reinforcing material 8 and the reinforcing material 8 of the cylindrical reinforcing member 6 are formed. The hardened material 4 is strongly reinforced by the ring-shaped hardware 7a, 7b. It is to be noted that the leg portion is attached to the lower ring-shaped hardware 7b in advance, and the clearance between the tip portion and the ground 3 is secured, thereby ensuring the filling property of the hardening material 4,
It is also possible to prevent corrosion of the lower ring-shaped hardware 7b.

In the present embodiment, the hardening material 4 was filled last, but at the time of excavating the enlarged excavation portion 2 in which the expanded bottom portion 5 is formed,
Soil cement obtained by stirring cement milk and soil may be filled as the hardening material 4, and then the cylindrical reinforcing body 6 may be deformed into a barrel shape to form the expanded bottom portion 5 by hardening the soil cement. Further, in this case, it is of course possible to fill concrete or cement milk as the hardening material 4.

FIG. 3 shows another embodiment of the present invention, in which the rod 9 and wires are fixed to the lower ring-shaped metal 7b, and the cylindrical reinforcing member 6 is installed at a predetermined position. After that, the rod 9 or the wire is pulled up from the pile head with a jack or the like to move the lower ring-shaped metal piece 7b upward to deform the cylindrical reinforcing body 6 into a barrel shape.

FIG. 4 shows an example in which the lower ring-shaped metal piece 7b of the cylindrical reinforcing member 6 is fixed to the steel pipe pile 1. By pushing the upper ring-shaped metal piece 7a with the casing pipe 11 and moving it downward, The cylindrical reinforcing body 6 is deformed into a barrel shape.

In these embodiments, since the cylindrical reinforcing member 6 which finally constitutes the expanded bottom portion 5 is a component different from the pile 1, it is easy to handle and the amount of reinforcement required for the expanded bottom portion 5 is increased. It is easy to deal with and mass production is possible.

[0027]

EFFECTS OF THE INVENTION By effectively reinforcing with steel material, the tensile strength of the bottom expanding portion can be improved, and the pulling force acting on the pile can be transmitted to the bottom expanding portion. As a result, due to the weight and shear resistance of the cylindrical ground on the expanded bottom portion, a large pullout resistance can be obtained as compared with the peripheral surface resistance of the pile shaft portion.

By constructing a cylindrical reinforcing body different from the pile body, it is possible to easily manufacture a bottom part reinforcement work corresponding to the load, and since the shape loss of the pile body itself does not occur, the safety of the pile body is also improved. Can be secured.

[Brief description of drawings]

1A to 1D are vertical sectional views showing a construction procedure in an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of a cylindrical reinforcing body.

FIG. 3 is a vertical sectional view showing another embodiment of the present invention.

FIG. 4 is a vertical sectional view showing still another embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view showing an outline of a conventional method of forming a bottom expansion part.

[Explanation of symbols]

1 ... Pile, 2 ... Enlarged excavation part, 3 ... Ground, 4 ... Hardened material, 5 ...
Expanded bottom portion, 6 ... Cylindrical reinforcement, 7a ... Upper ring-shaped metal piece, 7b ... Lower ring-shaped metal piece, 8 ... Reinforcing material, 9 ... Rod, 10 ... Auger, 11 ... Casing pipe

Claims (1)

[Claims] 1. A cylindrical reinforcing body in which a plurality of bar-shaped or strip-shaped reinforcing members extending in the up-and-down direction are arranged in a cylindrical shape, and the upper and lower sides of each reinforcing member are fixed to ring-shaped metal fittings for shape retention, respectively. , Fixed to the tip of the precast pile, after installing the precast pile in the ground, in the enlarged excavation section of the tip, by applying a compressive force in the axial direction to the cylindrical reinforcement, the cylindrical reinforcement A method for forming a pile bottom portion, characterized by deforming into a barrel shape so as to be convex outward in the diametrical direction, and hardening the hardened material filled in the tip portion of the existing pile in that state.