JPH05331848A - Construction method of pile strengthened in its horizontal resistance - Google Patents

Abstract

PURPOSE:To increase horizontal resistance, by setting, in a vertical hole, an inverted-truncated-conical pile, whose diameter is increasing gradually from a position close to the ground surface toward the upper part. CONSTITUTION:An upper pile 3 is enlarged in its diameter and its horizontal projected area near the ground surface is made large to effectively increase the horizontal resistance against bending moment. The upper pile 3 is made to resist against shearing force increasing in any position near the ground surface, by forming the upper pile 3 to be large in its diameter and its cross section area. Stress subsequent to the shearing force and the bending moment is smoothly transmitted owing to the fact that the upper pile 3 is inverted-truncated- conical and its diameter is changed smoothly. Moreover, the stress can be transmitted more smoothly by regulating the quantity of reinforcement and the thickness of concrete. In this way, the horizontal resistance can be increased without increasing the number of the piles and the size of them, and consequently, the design can be performed economically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile construction method for constructing foundations for construction and civil engineering structures, which has a strengthened horizontal resistance.

[0002]

2. Description of the Related Art A pile forming a foundation of a structure is designed so as to be capable of resisting a horizontal load such as an earthquake and a wind force as well as a vertical load of the structure. However, when designing the structure, it is unlikely that it will be a problem for vertical loads, but since horizontal resistance per pile is weak against horizontal force, it is necessary to counter horizontal force. We have responded by increasing the number of piles and by using large piles.

[0003]

Therefore, in general, the pile forming the foundation of the structure has a significant margin in the vertical load as compared with the horizontal force, which is, so to speak, uneconomical structure.

The present invention has been made to solve this problem, and an object of the present invention is to provide a horizontal resistance strengthening pile construction method capable of eliminating an uneconomical structure resulting from a large margin for a vertical load.

[0005]

In order to achieve the above object, the present invention provides a pile in which the diameter is gradually increased from a position close to the surface of the earth toward the upper side so that the diameter of the upper end is larger than the diameter of the lower end. , Is installed in the vertical hole.

[0006]

[Operation] The pile is displaced more horizontally in a position closer to the ground surface. The horizontal resistance is roughly proportional to the horizontal displacement, and increases as the horizontal projected area of the pile increases. Therefore, by gradually increasing the diameter of the pile from a position close to the surface of the ground upward, it is possible to make the uppermost portion of the pile into an inverted trapezoid, so that the horizontal resistance can be effectively increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view of a pile according to this embodiment.
The stake is vertically divided into two parts. First, the lower pile 1 is a general reinforced concrete pile or a PC pile.
A tip reinforcing portion 2 is provided at the lower end of the lower pile 1. A joint 4 with the upper pile 3 is provided at the upper end of the lower pile 1. A joint 5 is provided at the lower end of the upper pile 3 so that it can be welded to the joint 4 of the lower pile 1 on the welding surface 6 and is reinforced. The upper pile 3 has a larger diameter at the upper end than at the lower end, and the whole is a truncated cone. As a result, the diameter of the pile is formed so as to gradually increase from a position close to the ground surface upward.

The vertical hole in which the pile is installed is excavated by the pile hole drilling machine 7 shown in FIG. Main body 8 of pile drilling machine 7
On the other hand, a drilling screw auger 10 is provided via an auger rotating machine 9 so as to be rotatable about its axis. At the center of the drilling screw auger 10, a pipe 11 extends to the tip and is connected to a hose 12 at the rear end. The pipe 11 and the hose 12 are used for feeding mud and filling mortar for filling.

Next, FIG. 3 shows an outline of a procedure for installing piles in this embodiment. First, the vertical hole 13 is excavated by the drilling screw auger 10 (). After the excavation is completed, the mud water 14 is sent by the pipe 11 and the hose 12 to protect the hole wall. Further, a predetermined amount of the filling mortar 15 is fed ().

Next, the pile (FIG. 1) of this embodiment is built in the vertical hole 13 (). As the pile 16 enters the vertical hole 13, the muddy water 14 overflows and is temporarily stored in the drainage pit 17 formed on the surface of the ground in communication with the upper portion of the vertical hole 13. Then, it is collected in a muddy water storage layer (not shown) by the drainage hose 18. The collected mud water is sent again to the vertical hole to be drilled next.

In this way, the pile 16 is installed (). At this time, the filling mortar 15 (), which has been fed to the bottom of the vertical hole 13 by a predetermined amount, is pushed out by the tip of the pile 16 and is filled in the gap between the pile 16 and the vertical hole 13.

Depending on the condition of the ground where the piles 16 are to be installed, the vertical holes 13 may not be excavated in advance, and the piles 16 may be installed from the beginning.
May be driven with a pile driver. As in the above-described embodiment, the upper pile 3 is an inverted truncated cone, and the diameter of the pile 16 is gradually increased upward from a position close to the ground surface, thereby effectively increasing the horizontal resistance of the pile 16. be able to. Generally, a shear force as shown in FIG. 4A is generated with respect to the horizontal force P applied to the head of the pile 16. That is, the shearing force is the horizontal force P applied to the head of the pile minus the horizontal resistance force ω due to the ground.

At the same time, since the bending moment Mo acts on the head of the pile 16, the total bending moment is as shown in FIG.
It becomes like (B). That is, the bending moment is largest at the uppermost end of the pile, gradually decreases as it enters the ground, and becomes zero at a relatively shallow position in the case of a long pile. The horizontal displacement of the pile 16 can be obtained from the distribution of the bending moment.

This displacement becomes large near the head of the pile, that is, near the ground surface. Then, it is considered that horizontal resistance is generated in each part of the pile approximately in proportion to the displacement in the horizontal direction. Further, this horizontal resistance becomes larger as the horizontal projected area of the pile becomes larger. Therefore, the horizontal resistance can be effectively increased by increasing the diameter of the upper pile 3 and increasing the horizontal projected area of the pile at a position close to the ground surface.

Further, the shearing force also becomes large at a position close to the surface of the earth (FIG. 4 (A)), but the upper pile 3 is affected by this large shearing force.
By enlarging the diameter of, the cross section can be enlarged and it can oppose.

Furthermore, since the shape of the upper pile 3 is an inverted cone and the diameter thereof changes smoothly, it can be expected that the stress associated with the shearing force and the bending moment is smoothly transmitted. Also,
By adjusting the amount of internal reinforcing bars and the thickness of concrete so that the stress can be transmitted more smoothly, it is possible to more effectively cope with the horizontal force.

The piles in the above embodiments are the lower pile 1 and the upper pile 3.
It was divided into two parts (Fig. 1), but Fig. 5
The middle pile 19 may be provided between the lower pile 1 and the upper pile 3 as in the second embodiment shown in FIG. The middle pile 19 has a shape of an inverted circular truncated cone that is continuous with the upper pile 3, and is welded to the lower pile 1 by the joint 20 at the lower end and is welded to the upper pile 3 by the joint 21 at the upper end. By doing so, the portion of the pile 16 having a large horizontal projected area can be lengthened, and the horizontal resistance can be further increased.

It should be noted that, unlike the second embodiment shown in FIG. 6, the pile 16 may be manufactured integrally without being divided into a plurality of parts in the vertical direction. That is, only the upper portion of the integrally manufactured pile 16 is an inverted truncated cone. When the depth to the subgrade is shallow, a short pile is sufficient, and in this case, the pile shown in Fig. 6 is used.

[0019]

As described above, according to the horizontal resistance reinforced pile construction method of the present invention, the diameter of the pile is increased upward from the position close to the ground surface, so that the horizontal projected area of the pile is close to the ground surface. growing. The horizontal displacement of the pile is large near the ground surface. The horizontal resistance of the pile increases as the horizontal projection area increases, and is substantially proportional to the horizontal displacement, so that the horizontal resistance of the pile can be effectively increased.

Therefore, it is possible to increase the horizontal resistance and to carry out an economical design without increasing the number of piles or increasing the size as in the conventional case.

[Brief description of drawings]

FIG. 1 is a perspective view of a pile according to a first embodiment of the present invention.

FIG. 2 is a schematic side view of a pile hole drilling machine for excavating a vertical hole in which the pile of FIG. 1 is installed.

FIG. 3 is a schematic view of a procedure for installing the pile of FIG.

FIG. 4A is a shear force distribution diagram of a pile generated by horizontal force. (B) is a distribution diagram of the bending moment of the pile generated by the horizontal force.

FIG. 5 is a perspective view of a pile according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a pile according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Lower Pile 3 Upper Pile 4,5 Joint 10 Drilling Screw Auger 11 Pipe 12 Hose 13 Vertical Hole 14 Mud Water 15 Filling Mortar 17 Draining Pit 18 Draining Hose 19 Medium Pile

Claims (1)

[Claims] 1. A horizontal resistance strengthening pile construction method, wherein a pile having a diameter gradually increasing upward from a position close to the surface of the earth and having a diameter at an upper end larger than a diameter at a lower end is installed in a vertical hole.