JP2003155752A - Pile footing reinforcing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a support pile reinforcing structure, constructed by smaller- scale execution of work as compared with the conventional footing reinforcing structure, and capable of holding down the construction cost. SOLUTION: In a plurality of piles 14 driven in the ground 12 for supporting a structure 11, a reinforcing body 20 for reducing the stress generated in case of an earthquake is provided in the middle part of the pile isolated from the structure. The reinforcing body can be formed to include the piles of the plurality of the piles that are disposed in the outer periphery and not include the pile disposed in the center, or it can be formed to surround the plurality of piles from the outer periphery and not to come into contact with the piles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile foundation reinforcing structure for reducing stress generated in a plurality of piles due to horizontal load such as an earthquake.

[0002]

2. Description of the Related Art In order to construct a structure on soft ground, there is a structure in which a plurality of piles reaching a support layer are driven into the ground and a foundation structure is constituted by the plurality of piles. However,
If the ground consists of alluvial sand layers or sand layers mixed with fine-grained soil, liquefaction of the ground may occur in the event of an earthquake, and extremely high stress and deformation will occur in each pile. It may reach. Therefore, in such soft ground, the footing plane will be made larger than usual and the number of piles will be made larger than usual in the new structure, and in the existing structure, the footing widening, additional piles etc. Although it is considered to reinforce the foundation, there is a problem that large-scale construction is required and the construction cost becomes high.

[0003]

The present invention has been made to solve the above-mentioned conventional problems, and the problem is that it can be constructed by a small-scale construction as compared with the conventional pile foundation reinforcing structure. It is to provide a pile foundation reinforcement structure that can reduce the construction cost.

[0004]

According to the present invention, a reinforcing body for reducing stress generated in an earthquake in a plurality of piles driven in the ground for supporting a structure is arranged on the outer periphery. There is provided a pile foundation reinforcement structure, characterized in that it is provided in the middle part of the piles spaced from the structure so as to include the piles that are arranged and not to include the centrally arranged piles. In such a support pile reinforcing structure, the reinforcing body is formed so as to include, among a plurality of piles, a pile arranged on the outer periphery and not a pile arranged at the center, and the pile arranged at the center. The reinforcement is not directly bonded to the. However, earth and sand are present between this reinforcement and each pile in the central region, and the restraining force of the reinforcement is also transmitted to each pile in the central region via this sediment. In this way, the plurality of piles are all constrained by the reinforcing body, and the foundation structure including the plurality of piles and the reinforcing body becomes the same as the two-layered rigid frame structure. That is, from the pile tip to the reinforcement part in the plurality of piles corresponds to the first layer of the rigid frame structure, and from the reinforcement part to the structure corresponds to the second layer of the rigid frame structure, which increases the rigidity of the multiple piles. Therefore, even if a liquefaction phenomenon occurs in the ground due to, for example, an earthquake, the maximum bending strain generated at the joint between the pile and the structure is significantly suppressed. Further, in the support pile reinforcing structure, the weight of the plurality of piles is reduced due to the absence of the reinforcing body in the central region, and the vertical load of the plurality of piles is reduced. Further, since the movement of groundwater between the upper and lower sides of the reinforcing body is not blocked, the effect of reducing the buoyancy generated during liquefaction can be obtained.

Further, according to the present invention, a reinforcing body for reducing stress generated at the time of an earthquake in a plurality of piles driven in the ground for supporting a structure is provided around the plurality of piles from the outer circumference. A support pile reinforcing structure is provided which is provided at an intermediate portion of a pile separated from a structure so as not to contact the pile. In such a support pile reinforcing structure, a reinforcing body is provided so as to surround the plurality of piles on the outer periphery in the middle portion of the pile, and although the plurality of piles and the reinforcing body are not directly connected to each other at all, Earth and sand are intervening between the reinforcement body, and the restraining force from the reinforcement body is indirectly transmitted to the plurality of piles through the earth and sand, and the foundation structure composed of the plurality of piles and the reinforcement body is formed. It is similar to a two-layered ramen structure. That is, even if a liquefaction phenomenon occurs in the ground due to an earthquake or the like, the restraining force from the reinforcing body acts on multiple piles through the earth and sand, so the rigidity of the multiple piles is maintained and the bending strain Suppression becomes possible. The effect of suppressing the bending strain is particularly effective at the joint portion between the pile and the structure and the contact portion between the pile and the support layer.

In the present invention, the reinforcing body may be arranged so as to restrain a plurality of piles collectively and suppress the maximum bending moment generated at the joint between the plurality of piles and the structure. . Further, the reinforcing body may be arranged at any height as long as it is an intermediate portion from the lower end to the upper end of the pile, but it is preferable that the stress generated in the pile against the horizontal load during an earthquake is the smallest. It is installed at such a height.

[0007]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a side view of the support pile reinforcing structure of the present invention. In FIG. 1, the ground 1
Reference numeral 2 is a soft ground including an alluvial sand layer, a sand layer in which fine-grained soil is mixed, and the like, and a supporting layer 13 is present at a predetermined depth. The structure 11 is constructed on the ground 12, and a plurality of piles 14 are laid in the ground 12 so as to reach the support layer 13 from the structure 11 or its footing (not shown).
The reinforcement body 20 is separated from the structure 11 downward by a length H1 and is separated from the support layer 13 upward by a length H3.
Is provided in the middle part of. Reinforcing body 20 is H1, H3
Can be placed in the center in the height direction so that they have the same length, but this position in the height direction preferably has the smallest stress generated in the pile against a horizontal load such as an earthquake. It is determined as appropriate.

2A to 2C are cross-sectional views showing different forms, which correspond to the cross section taken along the line AA in FIG. Each of the reinforcing bodies 20 is the same when viewed from the side as shown in FIG. 1, but the cross section can be configured in a different form as shown in FIG. The reinforcing body 20A in FIG.
4 is formed so as to include the pile 14 arranged on the outer circumference and not include the pile 14 arranged at the center, and the reinforcing body 20A further includes a central region 22A that does not include the pile 14. It may be smaller than this. For example, as in the reinforcing body 20B of FIG. 2B, the outer peripheral region 21B including the pile 14 is made relatively large, and the central region 22B.
It is also possible to make the size relatively small. See also FIG.
20C of reinforcement bodies in (c) are several piles 14 from the outer periphery.
And is formed so as not to contact any of the piles 14. These reinforcements 20A, 20B, 20C
Of these, the horizontal plane is the reinforcement body 20B that can be made the widest so that strength is easily obtained, and therefore the vertical width H2
On the other hand, since the horizontal plane of the reinforcing body 20C becomes the narrowest, it is necessary to make the vertical width H2 relatively large to secure the strength. Reinforcement body 20
A, 20B, and 20C are, for example, silica colloid-based water glass as a curing agent, and a main material such as fine particle slag and a curing accelerator such as alkali calcium are mixed,
It can be formed by pouring this mixture into the ground to solidify the earth and sand. Therefore, the reinforcing body 20
A, 20B, and 20C are applicable not only to a newly constructed structure but also to an existing structure. The method of injecting the mixture into the ground can be carried out by applying a conventional technique, and a further description will be omitted here.

Next, the operation of the support pile reinforcing structure of the present invention will be described. Reinforcement bodies 20A and 20 shown in FIGS.
B is joined only to the piles 14 arranged in the outer peripheral areas 21A and 21B, and the piles 14 arranged in the central areas 22A and 22B
Are not directly joined to the reinforcing members 20A, 20
The restraint force of B is also transmitted to the piles 14 in the central regions 22A and 22B through the earth and sand in the central regions 22A and 22B. Therefore, the lower end of the pile 14 is fixed by the support layer 13, the middle portion is restrained by the reinforcing bodies 20A and 20B, and the upper end of the pile 14 is fixed to the structure 11, so that the plurality of piles 14 and the reinforcing bodies 20A, 20A, The basic structure composed of 20B has the same rigidity as the two-layer rigid frame structure. That is, the rigidity of the plurality of piles 14 depends on the reinforcement body 20.
Compared to the case without A and 20B at all, it is much higher,
Even when the liquefaction phenomenon occurs in the ground, the maximum bending strain generated in the fixed portion of the pile 11 in the structure 11 and the support layer 13 is significantly suppressed. In addition, the reinforcing body 20 of FIG.
C is not directly connected to any of the plurality of piles 14, but the restraining force of the reinforcing body 20C is transmitted to each pile 14 through the earth and sand in the inner region 22C, The rigidity of the plurality of piles 14 is increased in the same manner as described above, and the maximum bending strain generated in the fixed portion of the piles 14 in the structure 11 and the support layer 13 is also suppressed.

An experiment was conducted to verify the bending strain suppressing effect in the support pile reinforcing structure of the present invention, and the results are shown in FIG. (Experimental outline) In order to understand the behavior of the pile foundation during liquefaction, this experiment was carried out by installing the model of the support pile reinforcing structure of the present invention on a 1G field shaking table using a shear soil layer. .
On the shaking table, the shear soil layer is 1.5m wide x 0.4 depth
m × height 0.6 m, and the ground used silica sand No. 2
The horizontal ground consisting of the relative densities of the upper layer and the upper layer is 50% and the relative density of the lower layer is 90%. For the ground preparation, a sand sprinkling device that can evenly scatter sand was used, and a soil layer was created every 5 cm by the underwater drop method, and a predetermined relative density was confirmed. Water was used as the pore water. The pile model uses four steel pipes with an outer diameter of 19.1 mm, a wall thickness of 1.2 mm, and a length of 600 mm, and these four steel pipes are arranged in two columns and two rows at equal intervals of 150 mm (7.8 D). He supported footing. The top of the pile was rigidly connected to the footing, and the bottom of the pile was fixed to the bottom plate of the shaking table. In all three cases shown in FIG. 3, the ground is saturated sand, the case is not reinforced, the case is reinforced corresponding to FIG. 2 (c), and the case is shown in FIG. 2 (a) (b). It has been reinforced correspondingly. The input waveform in each case was the same.

(Experimental Results) FIG. 3 shows the distribution. The occurrence of bending strain increased with the progress of liquefaction and decreased sharply after complete liquefaction. 2 (a) to (c)
The maximum bending strain at the upper and lower ends of the pile in the case of reinforcement corresponding to the above was reduced by about 40 to 50% as compared with the case of no reinforcement. In addition, the case has a two-layer ramen-like structure because the pile middle portions of the outer circumference are integrally connected by the reinforcement body 20A or the reinforcement body 20B, and the plurality of piles are constrained more strongly than the case and become rigid. The bending strain was slightly smaller than that of the case.

[0012]

EFFECT OF THE INVENTION The support pile reinforcing structure of the present invention is constituted so that the reinforcement body includes the piles arranged on the outer periphery among the plurality of piles and the reinforcement body does not include the pile arranged in the center. Therefore, the plurality of piles are connected by the reinforcing body to increase the rigidity, and even when the liquefaction phenomenon occurs, the maximum bending strain generated at the joint portion between the pile and the structure is significantly suppressed. Further, in the present invention, a reinforcing body is provided so as to surround the plurality of piles on the outer periphery of the middle portion of the pile, and the restraining force from the reinforcing body is indirectly transmitted to the plurality of piles through the earth and sand. alike,
It is possible to suppress the maximum bending strain generated at the joint between the pile and the structure. Further, in the supporting pile reinforcing structure of the present invention, since the effect of suppressing the maximum bending strain as described above can be obtained only by providing the reinforcing body in the middle portion of the pile, it is possible to carry out a small-scale construction as compared with the conventional foundation reinforcing structure. It has become possible to reduce the construction cost.

[Brief description of drawings]

FIG. 1 is a side view of a support pile reinforcing structure of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, in which (a) to (c) show different embodiments.

FIG. 3 is a graph showing the results of an experiment conducted to verify the effects of the present invention.

[Explanation of symbols]

11 structures 12 ground 14 piles 20,20A, 20B, 20C Reinforcement body

Continued front page    (72) Inventor Yuji Adachi             2-5-8 Kita-Aoyama, Minato-ku, Tokyo Stock market             Within the company group (72) Inventor Masaya Mihara             2-5-8 Kita-Aoyama, Minato-ku, Tokyo Stock market             Within the company group F term (reference) 2D040 AB01 AC02 BD06 CA02 CA03                       CA04                 2D046 CA01 DA11

Claims (3)

[Claims] 1. A reinforcing body for reducing stress generated during an earthquake in a plurality of piles driven in the ground to support a structure, including the piles arranged on the outer periphery and arranged in the center. A pile foundation reinforcing structure, characterized in that it is provided in the middle part of the piles separated from the structure so as not to include the piles. 2. A reinforcement body for reducing stress generated at the time of an earthquake in a plurality of piles driven in the ground to support a structure so as to surround the plurality of piles from the outer periphery and not to contact the piles. In addition, a pile foundation reinforcement structure characterized in that it is provided at an intermediate portion in the depth direction of the pile separated from the structure. 3. The pile foundation reinforcing structure according to claim 1, wherein the reinforcing body is formed by pouring a solidifying agent into the ground to solidify the earth and sand.