JP2015086548A - Foundation structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple foundation structure corresponding to liquefaction of the ground.SOLUTION: A foundation structure comprises: a foundation body 10 which is constructed under the ground and supports a structure 100 installed above the ground; and a lightweight body 20 which is integrated with the foundation body 10 and has a unit weight smaller than the same. A center of buoyancy CB of an integrated body made up of the foundation body 10 and the lightweight body 20 is positioned closer to a ground surface GL than a center of gravity CG of the integrated body. For example, a shape and a position of the lightweight body 20 are decided so that buoyancy acting on the integrated body in the liquefied ground is not less than a total weight of the integrated body.

Description

  The present invention relates to a foundation structure for supporting a structure.

  Conventionally, when a structure is installed on the ground, it is required to take measures against liquefaction so that the structure can withstand the liquefaction phenomenon of the ground. For example, as a conventional countermeasure against liquefaction, a pile foundation structure is known in which a pile is placed on a bedrock where liquefaction does not occur, and even if the ground is liquefied, the structure is prevented from falling. As another liquefaction countermeasure, a countermeasure for improving the ground so that liquefaction does not occur is known. For example, Patent Document 1 below discloses a friction pile foundation structure that uses the improved ground and a pile having a large diameter portion at the lower end.

JP 2012-21346 A

  By the way, in the structure installed on the ground, there are devices, facilities, and the like that are not allowed to be unstable (eg, toppling over) when the ground is liquefied. For this reason, conventionally, countermeasures for liquefaction using a pile foundation structure or an improved ground have been applied to such structures as equipment. Here, looking at such devices and facilities, there are some complicated or large structures, and some simple or lightweight structures mainly composed of columnar objects. However, when the conventional liquefaction countermeasure is considered to support a simple or lightweight structure, a large-scale construction is required.

  Accordingly, an object of the present invention is to improve the disadvantages of the conventional example and to provide a simple basic structure corresponding to the liquefaction of the ground.

In order to solve the above-described problems and achieve the object, in the basic structure according to the present invention,
(1) A basic main body that is placed on the ground and supports a structure installed on the ground, and a lightweight body that is disposed so as to be integrated with the basic main body and has a unit volume weight smaller than the basic main body. , And the buoyancy of the integrated object composed of the structure, the basic main body, and the lightweight body is located on the ground surface side of the center of gravity of the integrated object.

  In the basic structure of (1), it is preferable that the lightweight body has a shape and an arrangement in which buoyancy acting on the integrated object on the liquefied ground is larger than the total weight of the integrated object.

Moreover, in order to solve the above-described problems and achieve the object, in the basic structure according to the present invention,
(2) A foundation main body that is placed on the ground and supports a structure installed on the ground, and a cavity provided inside the foundation main body, the structure and the foundation main body having the cavity The buoyancy of the monolithic body is characterized by being located closer to the ground surface than the center of gravity of the monolithic body.

  In the basic structure of the above (2), it is preferable that the cavity has a shape and an arrangement in which buoyancy acting on the integrated object on the liquefied ground is larger than the total weight of the integrated object.

  Even if the ground is liquefied by configuring such a lightweight body or a foundation provided with a cavity, the foundation structure according to the present invention is an integral structure composed of the foundation and the structure on the liquefied ground. Can prevent falls. For this reason, this foundation structure can avoid the fall of the structure on the liquefied ground when the ground is liquefied.

FIG. 1 is a diagram showing an example of the configuration of the first embodiment of the foundation structure according to the present invention. FIG. 2 is a top view of the foundation of the embodiment as viewed from above with the structure. FIG. 3 is a diagram for explaining an example of the attachment portion between the structure and the foundation main body. FIG. 4 is a diagram showing an example of the configuration of the second embodiment of the foundation structure according to the present invention.

  Embodiments of the basic structure according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

[Example 1]
A first embodiment of a foundation structure according to the present invention will be described with reference to FIGS.

  The foundation structure of the present embodiment is a representation of the foundation structure for supporting a structure installed on the ground. Although the basic structure of a present Example mainly supports a simple or lightweight structure, it is not necessarily limited to this. Examples of the simple or light-weight structure include a columnar object and a structure in which various functional parts are attached mainly using the columnar object. As the structure composed of columnar objects, poles or simple road signs can be considered. In addition, as a structure to which various functional parts and the like are attached, an antenna, a traffic light, an illumination lamp, and the like can be considered.

  This type of structure cannot perform its function if it falls. In particular, wireless antennas such as mobile phones and traffic lights are required to perform their functions only when disasters such as earthquakes occur, as a matter of course during normal times. However, when such a disaster occurs, a ground liquefaction phenomenon may occur, and the structure installed there may be overturned.

  Therefore, such a structure is installed on a foundation buried in the ground. However, the conventional foundation requires a large-scale construction such as hitting a pile on the bedrock, which may lead to an increase in construction period and cost. For this reason, the foundation of a present Example suppresses the fall of the structure on a liquefied ground with the simple structure which does not pile-up to a rock. Reference numeral 1 in FIGS. 1 and 2 indicates the basis of this embodiment.

  The foundation 1 of this embodiment includes a foundation main body 10. The foundation main body 10 forms the basis of the foundation 1 that supports the structure 100. The illustrated basic body 10 is formed by placing concrete on the ground G. The structure 100 is supported by the foundation main body 10 in the lower part thereof. For example, a plurality of anchor bolts 30 are embedded in the foundation main body 10 (FIG. 3). The structure 100 is attached to the foundation main body 10 through the threaded portion of the protruding portion of the anchor bolt 30. In FIG. 3, only a part of the many anchor bolts 30 is shown.

  Here, the foundation that is not held by the bedrock by the piles may fall together with the structure 100 together with the liquefaction of the ground G. Such a fall may occur as the position of the center of gravity CG of the integrated object composed of the foundation 1 and the structure 100 increases. For this reason, a measure for lowering the center of gravity CG of the integral object is taken for the basic main body 10. In addition, the other components which comprise the foundation 1, such as said anchor bolt 30 and a reinforcing bar, are also included in the integrated object.

  In the foundation 1, the center-of-gravity adjusting member is integrated with the inner or outer surface of the foundation main body 10.

  For example, in the integrated object, the position of the center of gravity CG is lowered by providing the weight body at a position deeper than the position of the center of gravity of the foundation main body 10 itself (rock side). The weight body is an object as a gravity center adjusting member having a unit volume weight larger than that of the basic main body 10. If it is assumed that the weight of the weight body is the same, the position of the center of gravity CG decreases as the position of the weight body increases. For this reason, such a foundation 1 makes it difficult for the integral to fall on the liquefied ground. When viewed in more detail, in this monolith, the position of the buoyancy CB rises toward the ground surface GL side as the position of the center of gravity CG decreases. And this one-piece | unit can suppress the fall on the liquefied ground in the state in which the position of the gravity center CG and the floating center CB correspond. In addition, when the buoyancy CB is present on the ground surface GL side with respect to the center of gravity CG, a restoring force centered on the center of gravity CG acts on the liquefied ground on the integrated body. It is possible to avoid a single object from falling.

  Further, as the center-of-gravity adjusting member, a lightweight body 20 having a unit volume weight smaller than that of the basic main body 10 can be used. For the lightweight body 20, for example, a resin material such as polystyrene foam, wood, or the like may be used. In FIG.1 and FIG.2, the thing by which the lightweight body 20 was arrange | positioned inside the foundation main body 10 is illustrated.

  Since the center of gravity CG moves to the ground surface GL side as the light weight body 20 is provided at a deeper position (rock side), the integrated body composed of the foundation 1 and the structure 100 becomes more likely to fall. Moreover, in this integrated object, by providing the lightweight body 20 at a deep position, there is a possibility that the position of the center of gravity CG exists on the ground surface GL side with respect to the position of the buoyancy CB. For this reason, in this case, this monolith is easy to fall on the liquefied ground. In other words, this unitary body has the center of gravity CG lowered by providing the lightweight body 20 at a shallow position (the ground surface GL side), and the position of the buoyancy CB is more than the position of the center of gravity CG. Since it can exist on the GL side, the possibility of falling on the liquefied ground can be reduced. Therefore, the lightweight body 20 is arranged so that the center of gravity CG and the buoyancy CB of the single body are at the same position, and more preferably, the position of the buoyancy CB is present on the ground surface GL side with respect to the position of the center of gravity CG. To do.

  For example, the lightweight body 20 is adjusted to the center of gravity position of an integral body composed of the foundation (the foundation 1 is the base body 1 excluding the lightweight body 20 and the space is filled with concrete) and the structure 100. Deploy. Thereby, in the integrated object which consists of the foundation 1 and the structure 100, the position of the gravity center CG and the floating center CB can be match | combined. Further, the lightweight body 20 is arranged so that the center of gravity position is closer to the ground surface GL side than the center of gravity position of the integrated object composed of the foundation serving as the base and the structure 100. Thereby, in the integrated object which consists of the foundation 1 and the structure 100, the position of the floating center CB can exist on the ground surface GL side rather than the position of the gravity center CG.

  By arranging the lightweight body 20 in this manner, the foundation 1 can suppress the overturn of the integrated body composed of the foundation 1 and the structure 100 on the liquefied ground. Furthermore, even if this foundation 1 is tilted along with the liquefaction of the ground due to shaking or the like at the time of the earthquake by making the position of the buoyancy CB closer to the ground surface GL than the position of the center of gravity CG, Since a restoring force centered on the center of gravity CG can be applied to the integrated object, it is possible to return the integrated object to its original state before liquefaction or to return to a state close to the original state and to be independent. it can. Therefore, when the ground is liquefied, the foundation 1 can avoid the fall of the integrated object on the liquefied ground. That is, this foundation 1 can avoid the fall of the structure 100 on the liquefied ground even if the ground is liquefied.

  Here, the restoring force increases as the center of gravity CG and the buoyancy CB are separated. The distance between the center of gravity CG and the buoyancy CB increases as the lightweight body 20 approaches the ground surface GL side (the shape and material of the lightweight body 20 are unchanged).

  By the way, in this foundation 1, in order to prevent the structure 100 from sinking to the liquefied ground, the center of gravity is adjusted so that the buoyancy acting on the integrated object on the liquefied ground is larger than the total weight of the integrated object. It is desirable to determine the shape and arrangement of the members. At this time, as long as the relationship between the buoyancy and the total weight of the integrated body can be maintained, the center-of-gravity adjusting member may be the lightweight body 20 exemplified here, or the above-described heavy body. May be. The buoyancy acting on the integrated object can be obtained by multiplying the unit volume weight of the liquefied ground by the submerged volume on the liquefied ground in the integrated object.

  As described above, the foundation 1 according to the present embodiment can lower the center of gravity CG of the integrated body including the foundation 1 and the structure 100 by providing the lightweight body 20 to the foundation main body 10. For this reason, this foundation 1 can suppress the fall of the structure 100 on the liquefied ground when the ground is liquefied. Moreover, this foundation 1 can make the floating body CB of the integral thing exist in the ground surface GL side rather than the gravity center CG by providing said lightweight body 20 with respect to the foundation main body 10. FIG. For this reason, even if the structure 100 tilts or leans on the liquefied ground, the foundation 1 can return the structure 100 to its original state and become independent. Thus, the structure 100 can be prevented from overturning. In addition, even if the foundation 1 cannot return the structure 100 to the original standing state on the liquefied ground, the foundation 1 returns the structure 100 to a state in which the function can be exerted by the restoring force and is made independent. be able to. Further, the foundation 1 is configured such that the buoyancy acting on the integrated object on the liquefied ground is larger than the total weight of the integrated object, thereby suppressing the settlement of the structure 100 on the liquefied ground. Can do.

[Example 2]
Reference numeral 2 in FIG. 4 represents the basis of this embodiment.

  In the foundation 1 of the first embodiment, the lightweight body 20 is provided on the foundation main body 10 to prevent the structure 100 from overturning when the ground is liquefied. The foundation 2 of the present embodiment achieves the same purpose as that of the first embodiment by providing a hollow 21 in the foundation main body 11 instead of the lightweight body 20.

  Here, the location of the cavity 21 is determined based on the same idea as the lightweight body 20. For example, the basic main body 11 of the present embodiment is obtained by replacing the lightweight body 20 with the cavity 21 in the basic main body 10 of the first embodiment, and corresponds to the basic main body 10 in which the lightweight body 20 is removed. Therefore, in the integrated body composed of the foundation 2 and the structure 100 of the present embodiment, the center of gravity CG is lowered compared to the case where the cavity 21 is not provided, and the floating center CB is closer to the ground surface GL side than the center of gravity CG. Will exist. For this reason, since this foundation 2 can avoid the fall of the integrated object, the fall of the structure 100 on the liquefied ground can be avoided. Further, the foundation 2 is a structure 100 to the liquefied ground by determining the shape and arrangement of the cavities so that the buoyancy acting on the monolith on the liquefied ground is greater than the total weight of the monolith. Can suppress the settlement of

DESCRIPTION OF SYMBOLS 1, 2 Foundation 10,11 Foundation main body 20 Light body 21 Cavity 30 Anchor bolt 100 Structure CB Floating center CG Center of gravity G Ground GL Ground surface

Claims (4)

A foundation that supports the structure placed on the ground and installed on the ground;
A lightweight body that is arranged so as to be integrated with the basic main body, and has a unit volume weight smaller than that of the basic main body,
With
A foundation structure characterized in that a floating body of an integral body composed of the structure, the foundation main body, and the lightweight body is positioned on the ground surface side of the center of gravity of the integral body.   2. The foundation structure according to claim 1, wherein the lightweight body has a shape and an arrangement in which a buoyancy acting on the integrated object on a liquefied ground is larger than the total weight of the integrated object. A foundation that supports the structure placed on the ground and installed on the ground;
A cavity provided inward of the foundation main body,
With
A foundation structure characterized in that a floating body of an integral body comprising the structure and the foundation main body having the cavity is located on the ground surface side of the center of gravity of the integral body.   The foundation structure according to claim 3, wherein the cavity has a shape and an arrangement in which a buoyancy acting on the monolith on the liquefied ground is larger than the total weight of the monolith.

Images