JPH09170232A - Highly reliable pile and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile of high reliability by filling space between a pre- loaded core pile and a steel tube pile with a viscoelastic material, and transmitting a periphery frictional resistance force to the ground via the viscoelastic material and the steel tube pile, when the core pile is subjected to a load placed thereon. SOLUTION: After installing a steel pipe pile 3 at the required depth, a core pile 2 is installed along a center within the hollow part of the pile 3. The end of the core pile 2 is, then, made to reach a support layer 5 and the prescribed magnitude of a pre-load is applied to the pile 2. With a forward end resistance force so generated on the pile 2, space between the pile 3 and the pile 2 is densely filled with a viscoelastic material 4. In this case, a core pile edge is formed to have a horizontal large diameter, as a means to increase the forward end resistance force as much as possible. Also, an annular projection or the like is formed on the outer surface of the pile 2 and both inner and outer surfaces of the pile 3 in a horizontal direction, as a means to increase a periphery frictional resistance force between the pile 2 and the material 4, and a periphery frictional resistance force among the pile 3, the elastic material 4 and the surrounding subsoil as much as possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly reliable pile mainly used as a support pile which constitutes a foundation of a building, and a manufacturing method (construction method) thereof.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, the method of calculating the static bearing force of a support pile of a building is such that the tip of the pile body a reaches the support layer b and the top load P is applied to the tip resistance force. It is designed and constructed so that it is supported by the resultant force R of Q _P and the frictional resistance Q _F of the peripheral surface. That is, R = Q _P + Q _F, and R _a > P
In the limit design method, the safety factor F
In consideration of the above, it is designed and constructed so as to satisfy the condition of P ≦ 1 / F (Q _P + Q _F ).

[0003]

In the conventional ultimate design method for supporting piles, attention is paid only to the magnitude of the force, and the calculation based on the strain and stress of the ground is not performed, so that the rationality and reliability are improved. Lack. This means that, when verifying the bearing capacity of a long pile from the two aspects of tip resistance and peripheral friction resistance, the pile top load is the peripheral surface caused by ground strain and stress starting from the ground surface. The mechanism that supports most of it by the action of frictional resistance, and the tip resistance hardly acts (see Fig. 3). Specifically, as shown in the stress-strain characteristics in FIG. 3, the peripheral frictional resistance Q _F of the pile rises at a steep slope from the zero point, and the peripheral surface of the pile is irrespective of the diameter of the pile. When the ground displacement is 10 to 20 mm, the maximum value (peak) is reached. On the other hand,
Tip resistance Q _P draws a very gentle rise gradient, finally reaching a maximum fairly large amount of deformation (0.1D~0.25D). Thus, for example, the resistance force R _a when taking a deformation amount 0.1D based the comparison results in that _{R a = Q Fa + Q Pa} , Q Fa as well, Q _Pa is the maximum value Q _F, the Q _P Then it is only a fraction of the size.

Nevertheless, the current design method ensures reliability by multiplying the resultant force R = Q _F + Q _P based on the maximum values Q _F and Q _P by the safety factor 1 / F. The design and construction is very rough and lacks rationality and reliability.
Therefore, an object of the present invention is to provide a pile exhibiting high reliability by making the peripheral frictional resistance and the tip resistance of the pile based on the behavior of stress and strain work as effectively and effectively as possible in superposition, and manufacturing thereof. Is to provide a method.

A further object of the present invention is to provide a highly reliable pile which is effective for a practical load bearing function of the pile and can be economically designed and constructed, and a manufacturing method thereof.

[0006]

As means for solving the above-mentioned problems of the prior art, the highly reliable pile according to the invention described in claim 1 reaches the support layer at the center of the steel pipe pile. A core pile that receives tip resistance is installed with a slight gap between the core pile and the steel pipe pile, and the gap between the preloaded core pile and the steel pipe pile is filled with a viscoelastic body. The frictional force of the peripheral surface when the bearing is loaded is transmitted to the ground through the viscoelastic body and the steel pipe pile.

Further, in the method for manufacturing a highly reliable pile according to the invention of claim 2, the steel pipe pile is built in the ground by the hollow excavation method, and the steel pipe pile is formed in the center of the hollow portion of the steel pipe pile. A step of installing a core pile having a diameter with a slight gap between the core pile and the support layer, preloading the core pile, and filling a viscoelastic body in the gap between the core pile and the steel pipe pile It is characterized by

The viscoelastic body according to claim 1 is characterized in that it is a sealing material, sand, or bentonite.
The core pile described in claim 1 is also characterized in that it is a precast concrete pile, a reinforced concrete structure or a steel frame reinforced concrete structure, or a steel pipe wound cast-in-place concrete pile.

When a preload (overload) is applied to the core pile installed in the steel pipe pile as in the present invention, this preload is directly transmitted to the support layer at the tip through the pile body and received from the support layer. Supported by resistance. Accordingly, the tip resistance _Q'P at this time rises steeply before the peripheral surface frictional resistance force acts as shown in FIG. The preload is applied to a size at which the core pile generates a strain of about 0.03D. After that, because the viscoelastic body is filled in the gap between the steel pipe pile and the core pile, when the core pile receives a top load, the stress generated due to the strain of the viscoelastic body on the peripheral surface as the core pile sinks. The frictional force Q _F on the peripheral surface resulting from the increase in the frictional force increases, and the resultant load (Q ′ _P + Q _F ) of both supports the above-mentioned load. In this case, a tip resistance _Q'P is outstanding contents, the tip resistance in the vicinity of the deformation amount 0.1D as a reference Q
′ _P and the peripheral frictional resistance Q _F reach their peaks, and the resultant force R _a = Q ′ _P + Q _{Fa of both} is exerted as a substantial function, and thus a highly reliable pile is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention shown in the drawings will be described below. In the support pile 1 shown in FIG. 1, before the core pile 2 in the central portion is filled with the viscoelastic body, the pile tip reaches the underground support layer 5 and directly receives the tip resistance force (supported). ) Is installed in the state. The steel pipe pile 3 has an inner diameter that allows a uniform gap of about 20 cm to 30 cm on the outer periphery of the core pile 2, and is installed to a necessary and sufficient depth in the ground. The core pile 2 is given a preload (overlay load) of such a magnitude that it distorts about 0.03D. After the preload is applied, the gap between the core pile 2 and the steel pipe pile 3 is densely filled with a viscoelastic body 4 such as a sealing material, sand or bentonite. Therefore, the outer peripheral surface of the core pile 2, the viscoelastic body 4, and the steel pipe pile 3
A frictional resistance force is generated between them, and the resistance force is transmitted from the viscoelastic body 4 to the surrounding ground through the steel pipe pile 3. The material and performance of the viscoelastic body 4 may be any substance as long as it has the above-mentioned function, and is not particularly limited to those exemplified above. The outer diameter of the core pile 2 constituting the high bearing pile 1 is generally 2.5 m, and the outer diameter of the steel pipe pile 3 is about 3.0 m. As the core pile 2, a precast concrete pile, a cast-in-place pile made of reinforced concrete or steel-framed reinforced concrete, a steel pipe wound cast-in-place concrete pile, or the like is applied. The depth of the steel pipe pile 3 is sufficient as long as it is effective for transmitting the peripheral frictional resistance force of the core pile 2 transmitted through the viscoelastic body 4 to the surrounding ground. It is not necessary to reach the support layer 5.

In the method for manufacturing the highly reliable pile 1, first, the steel pipe pile 3 is built by a medium excavation method using an excavator such as a drilling bucket. After the steel pipe pile 3 is installed at a required depth, the core pile 2 is installed in the center of the hollow part of the steel pipe pile 3 so that the tip of the core pile 2 reaches the support layer 5 and a predetermined amount of preload (upload) is applied. . Thus, after the core pile 2 is brought into a state in which a tip resistance force is generated, a step of densely filling the gap between the core pile 2 and the steel pipe pile 3 with the viscoelastic body 4 is carried out.

As a means for increasing the tip resistance force applied to the tip of the core pile 2 as much as possible, the tip end surface of the core pile is formed as a horizontal large-diameter surface, and the core pile 2 and the viscoelastic body 4 are formed. Between the outer peripheral surface of the core pile 2 and the steel pipe pile as means for increasing the peripheral friction resistance force between the steel pipe pile and the viscoelastic body and the surrounding ground as much as possible. -It is also preferable to form an annular (flange-shaped) convex strip or groove (concave) in the horizontal direction of the outer peripheral surface, or to provide irregularities.

[0013]

EFFECTS OF THE INVENTION According to the highly reliable pile and the manufacturing method thereof according to the present invention, the tip resistance can be expected to have excellent bearing capacity, and the tip resistance and the circumference can be expected based on the strain and stress of the ground. It can be expected that the surface friction resistance force will overlap and work reliably in an overlapping manner, and it can be used as a rational and highly reliable support pile or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view simply showing an embodiment of a highly reliable pile of the present invention.

FIG. 2 is a cross-sectional view showing a conventional pile and its supporting function.

FIG. 3 is a characteristic diagram showing, by stress-deformation, functions of a tip resistance force and a peripheral surface friction resistance force that act on a pile.

[Explanation of symbols]

 1 Highly reliable pile 2 Core pile 3 Steel pipe pile 4 Viscoelastic body 5 Support layer

Claims (4)

[Claims] 1. A core pile provided with a preload, wherein a core pile that reaches a supporting layer and receives a tip resistance force is installed at a central portion of the steel pipe pile with a slight gap between the core pile and the steel pipe pile. A viscoelastic body is filled in the gap with the steel pipe pile, and the frictional resistance of the peripheral surface when the core pile receives a top load is transmitted to the ground through the viscoelastic body and the steel pipe pile. , High reliability pile. 2. A steel pipe pile is laid in the ground by the underground digging method, and a core pile having a diameter with a slight gap between the steel pipe pile and the steel pipe pile reaches the support layer in the center of the hollow portion of the steel pipe pile. A method for producing a highly reliable pile, comprising a step of placing the core pile in a state and preloading the core pile, and then filling a gap between the core pile and the steel pipe pile with a viscoelastic body. 3. The highly reliable pile, wherein the viscoelastic body according to claim 1 is a sealing material, sand, or bentonite. 4. A highly reliable pile, wherein the core pile according to claim 1 is a precast concrete pile, a reinforced concrete construction or a steel reinforced concrete construction pile, or a steel pipe wound cast-in-place concrete pile.