JP2011117279A - Foundation base isolation structure using soft ground - Google Patents

Foundation base isolation structure using soft ground Download PDF

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JP2011117279A
JP2011117279A JP2011024094A JP2011024094A JP2011117279A JP 2011117279 A JP2011117279 A JP 2011117279A JP 2011024094 A JP2011024094 A JP 2011024094A JP 2011024094 A JP2011024094 A JP 2011024094A JP 2011117279 A JP2011117279 A JP 2011117279A
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ground
improvement body
soft
ground improvement
soft ground
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Takeyoshi Fukutake
毅芳 福武
Akira Seki
晃 関
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Shimizu Construction Co Ltd
Shimizu Corp
Kyowa Engineering Consultants Co Ltd
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Shimizu Construction Co Ltd
Shimizu Corp
Kyowa Engineering Consultants Co Ltd
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  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a foundation base isolation structure using a soft ground capable of reducing an acceleration input into a structure while suppressing direct damage to the foundation structure due to the high nonlinearization or the liquefaction of the ground. <P>SOLUTION: In this foundation base isolation structure using a soft ground, a soft ground improved using a ground improvement body 4 is used on the foundation of a structure 3 on the ground constituted of a lower layer by a hard ground 1 and an upper layer formed by the soft ground 2 which may be liquefied while leaving an unimproved layer h1 on the soft ground in the thickness direction. The ground improvement body includes a flat plate part 6 on the upper surface of which a structure is disposed and a bottom-less framework 7 which is attached to the lower surface of the flat plate part and constituted of leg plates vertically attached to the sides of the flat plate part, respectively. The unimproved layer is interposed between the ground improvement body and the lower layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、地盤の強非線形化や液状化による直接基礎構造物の被害を抑制しつつ、構造物に入力する加速度を低減する軟弱地盤を利用した地盤免震構造に関する。   The present invention relates to a ground-isolated structure using soft ground that reduces acceleration input to a structure while suppressing damage to a direct foundation structure due to strong nonlinearity or liquefaction of the ground.

従来より、地盤が液状化したり、超軟弱地盤が大きな地震力を受けると、地盤からの大きな強制変形により、構造物の基礎などに被害をもたらす。そこで、このような軟弱地盤の地盤に直接基礎の構造物を構築する場合、地盤改良を行い地盤の強非線形化や液状化を防止していた。これらの対策は、沈下や傾斜などの被害を軽減するものである。   Conventionally, when the ground is liquefied or the super soft ground is subjected to a large seismic force, the foundation of the structure is damaged due to a large forced deformation from the ground. Therefore, when constructing the foundation structure directly on the ground of such soft ground, the ground was improved to prevent strong non-linearization or liquefaction of the ground. These measures reduce damage such as subsidence and inclination.

しかし一方で、地盤剛性が強くなることにより、構造物に入力する地震加速度は大きくなり、地盤改良したためにかえって構造物が慣性力で被害を生じる場合がある。   On the other hand, however, since the ground rigidity is increased, the earthquake acceleration input to the structure is increased, and the structure may be damaged by inertial force because the ground is improved.

上記事情に鑑み、本発明は軟弱地盤を全深度にわたり改良するのではなく、未改良部分を残す地盤免震構造において、コスト縮減、工期短縮が可能であるとともに、安定性の高い地盤免震構造を実現することを目的とするものである。   In view of the above circumstances, the present invention does not improve the soft ground over the entire depth, but in the ground-isolated structure that leaves an unimproved portion, the cost can be reduced, the work period can be shortened, and the ground-isolated structure with high stability It aims at realizing.

請求項1記載の軟弱地盤を利用した地盤免震構造は、硬質地盤による下層と、液状化地盤である軟弱地盤による上層とにより構成される地盤上の構造物の基礎に対して、前記軟弱地盤に未改良層を厚さ方向に残しつつ、地盤改良体を用いて改良する軟弱地盤を利用した地盤免震構造において、前記地盤改良体は、上面に構造物が配置される平板部と、該平板部の下面に取り付けられて平板部の各辺に垂直に設けられた脚板からなる底面がない枠組みとを有し、前記地盤改良体と前記硬質地盤による下層との間に前記未改良層が介在していることを特徴としている。   The ground seismic isolation structure using the soft ground according to claim 1 is characterized in that the soft ground is based on a structure on the ground composed of a lower layer made of hard ground and an upper layer made of soft ground which is liquefied ground. In the ground seismic isolation structure using the soft ground that is improved using the ground improvement body while leaving the unimproved layer in the thickness direction, the ground improvement body includes a flat plate portion on which the structure is disposed on the upper surface, A non-bottom frame composed of leg plates attached to the lower surface of the flat plate portion and provided perpendicular to each side of the flat plate portion, and the unimproved layer between the ground improvement body and the lower layer of the hard ground It is characterized by interposition.

請求項2記載の軟弱地盤を利用した地盤免震構造は、前記地盤改良体における枠組みの内部には、前記平板部の下面で格子状に垂直に取り付けられた格子板を有し、該格子板と前記硬質地盤による下層との間に前記未改良層が介在していることを特徴としている。   The ground seismic isolation structure using the soft ground according to claim 2, wherein a lattice plate vertically attached in a lattice shape on the lower surface of the flat plate portion is provided inside the framework of the ground improvement body, and the lattice plate And the lower layer formed by the hard ground is characterized in that the unimproved layer is interposed.

請求項3記載の軟弱地盤を利用した地盤免震構造は、前記地盤改良体が、RC床版と他の地盤改良体を併用することを特徴としている。   The ground seismic isolation structure using the soft ground according to claim 3 is characterized in that the ground improvement body uses an RC floor slab and another ground improvement body in combination.

請求項4記載の軟弱地盤を利用した地盤免震構造は、前記RC床版の上面に、重心が中心になるとともに、分散的に配置された構造物群を設けることを特徴としている。   The ground seismic isolation structure using the soft ground according to claim 4 is characterized in that on the upper surface of the RC floor slab, a group of structures are arranged in a distributed manner with the center of gravity as the center.

請求項5記載の軟弱地盤を利用した地盤免震構造は、前記構造物群を立設する際に生じる前記地盤改良体の排土重量と、前記構造物群の重量とを等しくすることを特徴としている。   The ground seismic isolation structure using the soft ground according to claim 5 is characterized in that the soil removal weight of the ground improvement body generated when the structure group is erected is equal to the weight of the structure group. It is said.

請求項1記載の軟弱地盤を利用した地盤免震構造は、硬質地盤による下層と、液状化地盤である軟弱地盤による上層とにより構成される地盤上の構造物の基礎に対して、前記軟弱地盤に未改良層を厚さ方向に残しつつ、地盤改良体を用いて改良する地盤免震構造において、前記地盤改良体は、上面に構造物が配置される平板部と、該平板部の下端に取り付けられて平板部の各辺に垂直に設けられた脚板からなる底面のない枠組みとを有することから、地盤改良体としての剛性や安定性を十分に維持したままで、地盤改良体自身の体積を減少できるため、物量の減少に伴うコスト削減や工期短縮等、施工性のよい構造とすることが可能となる。   The ground seismic isolation structure using the soft ground according to claim 1 is characterized in that the soft ground is based on a structure on the ground composed of a lower layer made of hard ground and an upper layer made of soft ground which is liquefied ground. In the ground-isolated structure that is improved by using the ground improvement body while leaving the unimproved layer in the thickness direction, the ground improvement body includes a flat plate portion on which the structure is disposed on the upper surface, and a lower end of the flat plate portion. Since it has a frame with no bottom consisting of leg plates attached and perpendicular to each side of the flat plate part, the volume of the ground improvement body itself is maintained while maintaining sufficient rigidity and stability as the ground improvement body. Therefore, it becomes possible to make a structure with good workability such as cost reduction and shortening of construction period due to a decrease in quantity.

請求項2記載の軟弱地盤を利用した地盤免震構造は、前記地盤改良体における枠組みの内部には、前記平板部の下面で格子状に垂直に取り付けられた格子板を有することから、上記と同様に地盤改良体としての剛性や安定性を十分に維持したままで、地盤改良体自身の体積を減少できるため、物量の減少に伴うコスト削減や工期短縮等、施工性のよい構造とすることが可能となる。   The ground seismic isolation structure using the soft ground according to claim 2 has a lattice plate vertically attached in a lattice shape on the lower surface of the flat plate portion inside the framework of the ground improvement body. Similarly, since the volume of the ground improvement body itself can be reduced while maintaining sufficient rigidity and stability as the ground improvement body, a structure with good workability such as cost reduction and shortening the construction period due to a decrease in the amount of material shall be adopted. Is possible.

請求項3記載の軟弱地盤を利用した地盤免震構造は、前記地盤改良体が、RC床版と他の地盤改良体を併用することから、基礎の沈下が一様でなく、場所により異なった沈下を起こすといった不同沈下を抑制する効果を有するとともに、全体が沈下した際にはRC床版の下面にジャッキアップや薬液注入を行う等の修復作業を施すことが可能である。   The ground seismic isolation structure using the soft ground according to claim 3, wherein the ground improvement body uses an RC floor slab and another ground improvement body together. In addition to having the effect of suppressing uneven settlement such as causing subsidence, it is possible to perform repair work such as jacking up or injecting chemicals on the bottom surface of the RC floor slab when the entire subsidence occurs.

請求項4記載の軟弱地盤を利用した地盤免震構造は、前記RC床版の上面に、重心が中心になるとともに、分散的に配置された構造物群や橋脚群を設けることから、地盤の強非線形化や液状化が起こった場合にも局所的な不同沈下を抑制することが可能となり、配管や橋桁等の相対変位がなく、構造物や配管施設等への被害を最小限に押さえることを可能にするものである。   The ground seismic isolation structure using the soft ground according to claim 4 is provided with a structure group and a bridge pier group arranged in a distributed manner on the upper surface of the RC floor slab, with the center of gravity being the center. Even when strong nonlinearity or liquefaction occurs, local uneven settlement can be suppressed, and there is no relative displacement of piping and bridge girders, minimizing damage to structures and piping facilities. Is possible.

請求項5記載の軟弱地盤を利用した地盤免震構造は、前記構造物群を立設する際に生じる前記地盤改良体の排土重量と、前記構造物群の重量とを等しくすることから、構造物群と地盤改良体を併せた重量が、構造物群を配置しない場合の地盤改良体の重量に等しくなるため、地盤改良体の安定性は一層増すこととなる。   Since the ground seismic isolation structure using the soft ground according to claim 5 makes the soil removal weight of the ground improvement body generated when the structure group is erected and the weight of the structure group equal, Since the combined weight of the structure group and the ground improvement body is equal to the weight of the ground improvement body when the structure group is not disposed, the stability of the ground improvement body is further increased.

本発明の基本構成である地盤免震構造を示す図である。It is a figure which shows the ground seismic isolation structure which is the basic composition of this invention. 本発明に係る剛性の高い地盤改良材を用いた地盤改良体の構造の変形例を示した図である(第1の実施の形態)。It is the figure which showed the modification of the structure of the ground improvement body using the highly rigid ground improvement material which concerns on this invention (1st Embodiment). 本発明に係るRC床版と他の地盤改良材を用いた地盤改良体の構造を示す図である(第2の実施の形態)。It is a figure which shows the structure of the ground improvement body using the RC floor slab and other ground improvement material which concern on this invention (2nd Embodiment). 本発明に係るRC床版を用いた地盤免震構造を示した図である(第3の実施の形態)。It is the figure which showed the ground seismic isolation structure using the RC floor slab which concerns on this invention (3rd Embodiment). 地盤改良体の形状の変形例を示した図である(第4、第5の実施の形態)。It is the figure which showed the modification of the shape of a ground improvement body (4th, 5th embodiment). 本発明に係る地盤改良体の補助工法を示した図である(第1、第2の参考例)。It is the figure which showed the auxiliary construction method of the ground improvement object which concerns on this invention (1st, 2nd reference example).

図1に、本発明に係る軟弱地盤を利用した地盤構造の基本構成を示す。図1より明らかなように、硬質地盤1よりなる下層と、軟弱地盤2よりなる上層とより構成される地盤上に設けられた構造物3は、その基礎部が地盤改良体4により改良されているが、前記軟弱地盤2の下方には一部の深度に対して未改良部分h1を残している。   In FIG. 1, the basic composition of the ground structure using the soft ground which concerns on this invention is shown. As is clear from FIG. 1, the structure 3 provided on the ground composed of the lower layer composed of the hard ground 1 and the upper layer composed of the soft ground 2 has its foundation improved by the ground improvement body 4. However, an unimproved portion h1 is left below the soft ground 2 with respect to some depth.

地盤における軟弱地盤2が液状化すると、地震加速度の振幅が小さくなるため、剛性低下及び履歴減衰を引き起こすこととなり、該軟弱地盤2の上面に位置する構造物3にとっては、免震効果を発揮するものである。本発明の基本構成となる地盤免震構造は、この原理を活用し、軟弱地盤2の全深度H1のうち、下方に未改良部分h1を残すことにより、未改良部分h1が、強非線形化または液状化することにより、構造物3への地震入力加速度を低減するものである。   When the soft ground 2 in the ground is liquefied, the amplitude of the earthquake acceleration is reduced, leading to a decrease in rigidity and a history attenuation. For the structure 3 located on the upper surface of the soft ground 2, the seismic isolation effect is exhibited. Is. The ground seismic isolation structure, which is the basic configuration of the present invention, utilizes this principle and leaves the unimproved portion h1 below the total depth H1 of the soft ground 2 so that the unimproved portion h1 becomes strongly nonlinear or By liquefying, the earthquake input acceleration to the structure 3 is reduced.

なお、本発明の基本構成となる地盤免震構造における必要条件としては、地盤改良体4が軟弱地盤2に比べて十分な剛性を有していること、硬質地盤1よりなる下層も十分な剛性を有していることが挙げられる。また、前記未改良部分h1の厚さは、要求される耐震性能に応じて自由に設定することが可能である。   In addition, as a necessary condition in the ground seismic isolation structure which is the basic configuration of the present invention, the ground improvement body 4 has sufficient rigidity compared to the soft ground 2, and the lower layer made of the hard ground 1 also has sufficient rigidity. It is mentioned that it has. Further, the thickness of the unimproved portion h1 can be freely set according to the required seismic performance.

基本構成となる地盤免震構造は、直接基礎の構造物でアスペクト比があまり大きくなく、慣性力に対して泥弱な建築物に適した構造である。   The base seismic isolation structure, which is the basic structure, is a direct foundation structure that does not have a very large aspect ratio and is suitable for buildings that are mud against inertia.

ここで用いられる地盤改良体4は、締固めた砂(サンドコンパクションパイル工法等による)、ソイルセメント系(深層混合処理)改良体、発泡スチロール、土嚢(ソイルパックバッグ)、RC床版5等が考えられるが、これにこだわるものではなく、液状化や強比線形化を防止することの出来る地盤改良材であれば、いずれでもよい。   The ground improvement body 4 used here may be compacted sand (by sand compaction pile method, etc.), soil cement type (deep mixing treatment) improvement body, styrofoam, sandbag (soil pack bag), RC floor slab 5, etc. However, it is not particularly limited to this, and any ground improvement material that can prevent liquefaction and strong ratio linearization may be used.

ただし、このような地盤改良体4は、コストが高く設計条件に合わない場合が多い。このため、特にソイルセメント系(深層混合処理)改良体やRC床版5等、剛性を有する地盤改良材であれば、図2に示すように該地盤改良体4の構造を工夫し、体積を減少させて適用させればよい。   However, such a ground improvement body 4 is expensive and often does not meet the design conditions. For this reason, in particular, if it is a ground improvement material having rigidity, such as a soil cement-based (deep mixing treatment) improvement body or an RC floor slab 5, the structure of the ground improvement body 4 is devised as shown in FIG. What is necessary is just to reduce and apply.

(第1の実施の形態)
図2(a)に示す地盤改良体4は、上面に構造物3が配置された平板部6と、該平板部6の下面に取り付けられて、平板部の各辺に垂直に設けられた脚板からなる枠組み7とを有している。
(First embodiment)
The ground improvement body 4 shown to Fig.2 (a) is the flat plate part 6 with which the structure 3 was arrange | positioned on the upper surface, and the leg plate attached to the lower surface of this flat plate part 6, and provided perpendicular | vertical to each edge | side of a flat plate part. And a framework 7 consisting of

これら、枠組み7とその上面に設けられた平板部6による箱体は、底面がなく、内部7aは空洞であり、軟弱地盤2が充填されている。これら該枠組み7に囲まれた軟弱地盤2は、非線形化しづらいため、従来より用いられている長方体の地盤改良体4と同じ効果を有することとなる。   The box made up of the frame 7 and the flat plate portion 6 provided on the upper surface thereof has no bottom surface, the inside 7a is hollow, and the soft ground 2 is filled. Since the soft ground 2 surrounded by the frame 7 is difficult to be non-linear, it has the same effect as the rectangular ground improvement body 4 that has been conventionally used.

また、図2(b)に示すように、前記内部7aにさらに枠組み7と同様の厚さおよび長さを有する格子板8を用いて格子を設けることにより、前記地盤改良体4の平板部6は、前記構造物3の荷重によるたわみ等の変形に対する強度を増し、基礎構造としての強度、及び安定性が高まることとなる。   Further, as shown in FIG. 2B, a flat plate portion 6 of the ground improvement body 4 is provided by providing a lattice in the interior 7a using a lattice plate 8 having the same thickness and length as the frame 7. Increases the strength against deformation such as deflection caused by the load of the structure 3, and the strength and stability of the foundation structure are increased.

上述する構成により、地盤改良体4としての剛性や安定性を十分に維持したままで、地盤改良体4自身の体積を減少できるため、物量の縮減に伴うコスト縮減や工期短縮等、施工性のよい構造とすることが可能となる。   With the configuration described above, the volume of the ground improvement body 4 itself can be reduced while maintaining the rigidity and stability as the ground improvement body 4 sufficiently. A good structure can be obtained.

なお、前記平板部6と前記枠組み7に、同一の地盤改良材を用いてもよいが、平板部6に前記RC床版5、枠組み7に他の地盤改良材を用いる、といったように複数の地盤改良材を併用してもよい。   The same ground improvement material may be used for the flat plate portion 6 and the frame 7, but a plurality of ground improvement materials such as the RC floor slab 5 for the flat plate portion 6 and another ground improvement material for the frame 7 may be used. A ground improvement material may be used in combination.

(第2の実施の形態)
その他の地盤改良体4の構造においても、前記地盤改良体4に複数の地盤改良材を組み合わせて併用することが可能である。一例として図3に、前記RC床版5の上面に構造物3を配置し、前記RC床版5の周囲には他の地盤改良材を併用するような地盤改良体4の構造を示す。
(Second Embodiment)
Also in the structure of the other ground improvement body 4, it is possible to use a combination of a plurality of ground improvement materials in combination with the ground improvement body 4. As an example, FIG. 3 shows a structure of the ground improvement body 4 in which the structure 3 is disposed on the upper surface of the RC floor slab 5 and another ground improvement material is used around the RC floor slab 5.

RC床版5を用いる地盤改良体4の構造による効果は、RC床版5に構造物3を立設することにより、基礎の沈下が一様でなく、場所により異なった沈下を起こすといった現象である不同沈下を抑制する効果を有するとともに、全体が沈下した際にはRC床版5の下面にジャッキアップや薬液注入を行う等の修復作業を施すことが可能である。   The effect of the structure of the ground improvement body 4 using the RC floor slab 5 is a phenomenon in which the foundation subsidence is not uniform due to the erection of the structure 3 on the RC floor slab 5, and the subsidence varies depending on the location. In addition to having the effect of suppressing certain uneven settlement, it is possible to perform repair work such as jacking up or injecting chemicals on the lower surface of the RC floor slab 5 when the entire body sinks.

(第3の実施の形態)
前記RC床版5を適用した地盤免震構造の一例として、RC床版5の上面に配置する構造物3には、図4に示すように、工場施設群のような広い構造物群11や橋脚群を適用することが可能である。ただし、これらの構造物群11や橋脚群は、全体としてアスペクト比が小さいことが必要条件であり、前記地盤改良体4に対して荷重が偏心してかからないよう、前記構造物群11や橋脚群の荷重の重心を地盤改良体4の中心に位置させる必要がある。
(Third embodiment)
As an example of the ground seismic isolation structure to which the RC floor slab 5 is applied, the structure 3 arranged on the upper surface of the RC floor slab 5 includes a wide structure group 11 such as a factory facility group as shown in FIG. It is possible to apply a pier group. However, the structure group 11 and the pier group are required to have a small aspect ratio as a whole, and the structure group 11 and the pier group of the structure group 11 and the pier group so that the load is not decentered with respect to the ground improvement body 4. It is necessary to position the center of gravity of the load at the center of the ground improvement body 4.

これら地盤免震構造の効果は、構造物3どうしが配管や橋桁等により連結されるような広い構造物群11全体を前記RC床版5上に配置することによって、地盤の強非線形化や液状化が起こった場合にも局所的な不同沈下を抑制することが可能となり、配管や橋桁等の相対変位がなく、構造物や配管施設等への被害を最小限に押さえることを可能にするものである。   The effect of these seismic isolation structures is that the entire structure group 11 in which the structures 3 are connected to each other by pipes, bridge girders, etc. is arranged on the RC floor slab 5 to make the ground strongly nonlinear or liquid. It is possible to suppress local unsettled subsidence even in the event of commutation, and there is no relative displacement of piping and bridge girders, etc., and it is possible to minimize damage to structures and piping facilities etc. It is.

なお、前記構造物群11や橋脚群を地盤改良体4に配置する際に、構造物群11や橋脚群の荷重と等しい重量だけ地盤改良体4を掘削し、構造物群11と地盤改良体4を併せた重量が、構造物群11や橋脚群を配置しない場合の地盤改良体4の重量に等しくなるように施工すると、地盤改良体4の安定性は一層増すこととなる。   When the structure group 11 and the pier group are arranged on the ground improvement body 4, the ground improvement body 4 is excavated by a weight equal to the load of the structure group 11 and the pier group, so that the structure group 11 and the ground improvement body are excavated. When construction is performed so that the combined weight of 4 is equal to the weight of the ground improvement body 4 when the structure group 11 and the pier group are not arranged, the stability of the ground improvement body 4 is further increased.

(第4の実施の形態)
ところで、本実施の形態のように構造物3の基礎に地盤改良体4を用いた場合には、先にも述べた不同沈下が起こりやすい。特に、前記地盤改良体4の上面に立設された構造物3について、地盤改良体4の中心部に荷重の重心がかからないような偏心荷重の構造物3に地盤改良体4による基礎を設ける場合には、不同沈下や傾斜が起こりやすい。このような場合には、図5(a)に示すように、重心の偏っている側の前記地盤改良体4を他の側より厚くし、重心の偏っている側の未改良部分h12をその他の側の未改良部分h11より薄くすればよい。
(Fourth embodiment)
By the way, when the ground improvement body 4 is used for the foundation of the structure 3 as in the present embodiment, the above-described uneven settlement is likely to occur. In particular, in the case of providing the foundation by the ground improvement body 4 to the structure 3 having an eccentric load so that the center of gravity of the load is not applied to the center of the ground improvement body 4 with respect to the structure 3 standing on the upper surface of the ground improvement body 4 There is a tendency for uneven settlement and inclination. In such a case, as shown in FIG. 5 (a), the ground improvement body 4 on the side where the center of gravity is biased is made thicker than the other side, and the unimproved portion h12 on the side where the center of gravity is biased is made other. What is necessary is just to make it thinner than the unimproved part h11 of the side.

(第5の実施の形態)
図5(b)に示すように、前記構造物3は偏心荷重ではないが、地盤の硬質地盤1よりなる下層が不整形地盤の場合にも、前記地盤改良体4の下面において未改良部分h1の厚さが部分的に異なることにより、地震時の加速度振幅に差が生じ、不同沈下を生じる原因となりやすい。このため、未改良部分h1の厚さが均一となるよう、前記地盤改良体4の下面を硬質地盤1よりなる下層と平行になるように設ければよい。
(Fifth embodiment)
As shown in FIG. 5 (b), the structure 3 is not an eccentric load, but the unmodified portion h1 on the lower surface of the ground improvement body 4 even when the lower layer made of the hard ground 1 of the ground is irregular ground. Due to the partial differences in thickness, the difference in acceleration amplitude during an earthquake is likely to cause uneven subsidence. For this reason, what is necessary is just to provide the lower surface of the said ground improvement body 4 so that it may become in parallel with the lower layer which consists of the hard ground 1 so that the thickness of the unimproved part h1 may become uniform.

これにより、地盤改良体4の下面全域に対して未改良部分h1が同じ厚さを保つため、入力される地震加速度の低減量が一定となり、これら地盤改良体4の安定性が一層増すこととなる。   Thereby, since the unimproved portion h1 maintains the same thickness with respect to the entire lower surface of the ground improvement body 4, the reduction amount of the input earthquake acceleration becomes constant, and the stability of the ground improvement body 4 is further increased. Become.

(第1の参考例)
また、地盤改良体4に係る補助工法としては、不同沈下を防止することを目的とした工法として、図6に示すように、前記地盤改良体4と硬質地盤1よりなる下層とを複数の棒材9を介して連結すればよい。前記地盤改良体4と硬質地盤1よりなる下層とそれぞれに対して垂直に前記棒材9を設けることにより、前記地盤改良体4が不同沈下を起こそうとして生じる圧縮力に対して、前記棒材9が逆らうことにより、不同沈下を防ぐものである。
(First reference example)
Moreover, as an auxiliary construction method related to the ground improvement body 4, as shown in FIG. 6, as a construction method aimed at preventing uneven settlement, the ground improvement body 4 and the lower layer made of the hard ground 1 are made of a plurality of bars. What is necessary is just to connect through the material 9. By providing the bar 9 perpendicular to the ground improvement body 4 and the lower layer composed of the hard ground 1, the bar material against the compressive force generated when the ground improvement body 4 tends to cause uneven settlement. 9 counters to prevent uneven settlement.

(第2の参考例)
さらに、前記地盤改良体4の側面からの地震加速度の入力を低減することを目的とした場合には、図6に示すように、地盤改良体4の側面に粘性材やクッション材などの側面入力低減材10を設ける。該側面入力低減材10としては、アスファルトやエラストマー(ゴム)等の部材が考えられるが、粘性を有する材料であればこれにこだわるものではない。
(Second reference example)
Further, in the case of aiming to reduce the input of earthquake acceleration from the side surface of the ground improvement body 4, as shown in FIG. 6, side input such as a viscous material or a cushion material is provided on the side surface of the ground improvement body 4. A reducing material 10 is provided. The side input reducing material 10 may be a member such as asphalt or elastomer (rubber), but is not particularly limited as long as it is a viscous material.

上述するような補助工法を実施することにより、前記地盤改良体4を安定させて、不同沈下や傾斜などの被害を抑制しつつ、構造物3に入力される地震加速度を低減することが可能となる。   By implementing the auxiliary method as described above, it is possible to stabilize the ground improvement body 4 and reduce the earthquake acceleration input to the structure 3 while suppressing damage such as uneven settlement and inclination. Become.

なお、これまでに示したすべての実施の形態について、前記地盤改良体4は、単一の地盤改良材を用いてもよいし、複数の地盤改良材を併用して用いてもかまわない。   In addition, about all embodiment shown so far, the said ground improvement body 4 may use a single ground improvement material, and may use it using a some ground improvement material together.

このように、本実施の形態はあくまでも一部の事例であり、本発明の趣旨を逸脱しない限り、本実施の形態に減退されずにいかなる形態をも採用しうることは、言うまでもない。   Thus, this embodiment is only a part of examples, and it goes without saying that any form can be adopted without deteriorating to this embodiment without departing from the gist of the present invention.

1…硬質地盤 2…軟弱地盤 3…構造物 4…地盤改良体 5…RC床版 6…平板部 7…枠組み 7a…内部 8…格子板 9…棒材 10…側面入力低減材 11…構造物群 h1…未改良部分(未改良層)   DESCRIPTION OF SYMBOLS 1 ... Hard ground 2 ... Soft ground 3 ... Structure 4 ... Ground improvement body 5 ... RC floor slab 6 ... Flat plate part 7 ... Framework 7a ... Inside 8 ... Grid board 9 ... Bar material 10 ... Side surface input reduction material 11 ... Structure Group h1 ... Unmodified part (unmodified layer)

Claims (5)

硬質地盤による下層と、液状化地盤である軟弱地盤による上層とにより構成される地盤上の構造物の基礎に対して、前記軟弱地盤に未改良層を厚さ方向に残しつつ、地盤改良体を用いて改良する軟弱地盤を利用した地盤免震構造において、前記地盤改良体は、上面に構造物が配置される平板部と、該平板部の下面に取り付けられて平板部の各辺に垂直に設けられた脚板からなる底面がない枠組みとを有し、前記地盤改良体と前記硬質地盤による下層との間に前記未改良層が介在していることを特徴とする軟弱地盤を利用した地盤免震構造。   For the foundation of the structure on the ground composed of the lower layer by the hard ground and the upper layer by the soft ground which is the liquefied ground, the ground improvement body is left in the thickness direction while leaving the unmodified layer on the soft ground. In the ground-isolated structure using the soft ground that is improved by using the ground improvement body, the ground improvement body is attached to the lower surface of the flat plate portion with the structure disposed on the upper surface and perpendicular to each side of the flat plate portion. A ground-free structure using a soft ground, characterized in that it has a frame made of leg plates and has no bottom surface, and the unimproved layer is interposed between the ground improved body and the lower layer of the hard ground. Seismic structure. 請求項1記載の軟弱地盤を利用した地盤免震構造において、前記地盤改良体における枠組みの内部には、前記平板部の下面で格子状に垂直に取り付けられた格子板を有し、該格子板と前記硬質地盤による下層との間に前記未改良層が介在していることを特徴とする軟弱地盤を利用した地盤免震構造。   The ground seismic isolation structure using the soft ground according to claim 1, wherein a lattice plate vertically attached in a lattice shape on the lower surface of the flat plate portion is provided inside the framework of the ground improvement body, and the lattice plate A ground-isolated structure using soft ground, wherein the unimproved layer is interposed between the ground and the lower layer of the hard ground. 請求項1または2に記載の軟弱地盤を利用した地盤免震構造において、前記地盤改良体は、RC床版と他の地盤改良体を併用することを特徴とする軟弱地盤を利用した地盤免震構造。   The ground seismic isolation structure using the soft ground according to claim 1 or 2, wherein the ground improvement body uses an RC floor slab and another ground improvement body in combination. Construction. 請求項3記載の軟弱地盤を利用した地盤免震構造であって、前記RC床版の上面には、重心が中心になるとともに、分散的に配置された構造物群を設けることを特徴とする軟弱地盤を利用した地盤免震構造。   It is a ground seismic isolation structure using the soft ground according to claim 3, wherein the RC floor slab is provided with a group of structures arranged in a distributed manner with the center of gravity at the center. A ground-isolated structure using soft ground. 請求項4記載の地盤免震構造であって、前記構造物群を立設する際に生じる前記地盤改良体の排土重量と、前記構造物群の重量とを等しくすることを特徴とする軟弱地盤を利用した地盤免震構造。   5. The ground seismic isolation structure according to claim 4, wherein the soil removal weight of the ground improvement body generated when the structure group is erected is made equal to the weight of the structure group. Ground-isolated structure using the ground.
JP2011024094A 2011-02-07 2011-02-07 Foundation base isolation structure using soft ground Pending JP2011117279A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62215727A (en) * 1986-03-17 1987-09-22 Fudo Constr Co Ltd Foundation work for structure
JPH04323413A (en) * 1991-04-23 1992-11-12 Shimizu Corp Liquefaction preventive construction method for sand ground
JPH10280433A (en) * 1997-04-08 1998-10-20 Tenox Corp Foundation structure
JPH1113069A (en) * 1997-06-23 1999-01-19 Fujita Chishitsu:Kk Settlement preventing foundation structure and foundation work method
JPH11181755A (en) * 1997-12-17 1999-07-06 Ohbayashi Corp Base isolation structure in soft ground
JP2000336669A (en) * 1999-06-02 2000-12-05 Takenaka Komuten Co Ltd Liquefaction countermeasure construction method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62215727A (en) * 1986-03-17 1987-09-22 Fudo Constr Co Ltd Foundation work for structure
JPH04323413A (en) * 1991-04-23 1992-11-12 Shimizu Corp Liquefaction preventive construction method for sand ground
JPH10280433A (en) * 1997-04-08 1998-10-20 Tenox Corp Foundation structure
JPH1113069A (en) * 1997-06-23 1999-01-19 Fujita Chishitsu:Kk Settlement preventing foundation structure and foundation work method
JPH11181755A (en) * 1997-12-17 1999-07-06 Ohbayashi Corp Base isolation structure in soft ground
JP2000336669A (en) * 1999-06-02 2000-12-05 Takenaka Komuten Co Ltd Liquefaction countermeasure construction method

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