JP2005023671A

JP2005023671A - Structure settlement reduction structure

Info

Publication number: JP2005023671A
Application number: JP2003190993A
Authority: JP
Inventors: Hiroyuki Hotta; 洋之堀田; Yutaka Katsura; 豊桂; Yasuhiro Shamoto; 康広社本
Original assignee: Shimizu Construction Co Ltd; Shimizu Corp
Current assignee: Shimizu Construction Co Ltd; Shimizu Corp
Priority date: 2003-07-03
Filing date: 2003-07-03
Publication date: 2005-01-27

Abstract

【課題】本発明は、簡略な構成で、安価な構造物の沈下低減構造を提供する。
【解決手段】地盤１は、地震の発生に伴い液状化を生じやすい砂層等により構成される表層３と、表層３の直下に位置し、粘性土等の非液状化地盤により構成される中間層２を備えている。また、地盤１の液状化層により構成される表層３には、構造物４の鉛直同軸上に地盤改良体６が構築されている。地盤改良体６の形状は、少なくとも前記構造物４の構築面積を内包する平面視断面を有するとともに、地震等が発生して表層３が一様に液状化し、これに伴い一様な体積ひずみが生じて地盤１全体が表層３の層厚に比例して沈下した際にも、地盤改良体６の構築位置では、地盤１の沈下に伴う構造物４の沈下量を許容範囲内に収めることのできる層厚を有する大きさに成形されている。
【選択図】図１The present invention provides a structure for reducing settlement of an inexpensive structure with a simple configuration.
SOLUTION: The ground 1 includes a surface layer 3 composed of a sand layer or the like that is liable to be liquefied due to the occurrence of an earthquake, and an intermediate layer that is located immediately below the surface layer 3 and is composed of a non-liquefied ground such as viscous soil. 2 is provided. A ground improvement body 6 is constructed on the vertical axis of the structure 4 on the surface layer 3 constituted by the liquefied layer of the ground 1. The shape of the ground improvement body 6 has a plan view cross section including at least the construction area of the structure 4, and an earthquake or the like occurs to cause the surface layer 3 to be liquefied uniformly. Even when the entire ground 1 sinks in proportion to the layer thickness of the surface layer 3, the subsidence amount of the structure 4 accompanying the subsidence of the ground 1 can be kept within an allowable range at the construction position of the ground improvement body 6. It is formed into a size having a possible layer thickness.
[Selection] Figure 1

Description

【０００１】
【発明の属する技術分野】
本発明は、構造物の沈下低減構造に関する。
【０００２】
【従来の技術】
表層、あるいは表層の直下に位置する中間層が砂層等の液状化の可能性がある層により構成されている地盤に、構造物を構築すると、地震等の発生に伴い表層もしくは中間層に液状化が生じ、その後地盤が沈下して構造物に不具合が発生することが考えられる。そこで、例えば、特許文献１に示すように、液状化そのものの発生を防止する対策が取られている。
【０００３】
【特許文献１】
特開平０５−０５９７１７号公報（第２図参照）
【０００４】
【発明が解決しようとする課題】
しかし、上述する構成は、液状化の発生を完全に抑制することが困難な場合もあり、また、構造物の規模や液状化を生じる層の層厚が大きくなるに従い、工期の長期化や工費が膨大になるなど、様々な課題が生じていた。
【０００５】
上記事情に鑑み、本発明は、簡略な構成で、安価な構造物の沈下低減構造を提供することを目的としている。
【０００６】
【課題を解決するための手段】
請求項１記載の構造物の沈下低減構造は、表層、もしくは該表層の直下に位置する中間層の何れかが、地震時に液状化する可能性のある液状化層により構成されている地盤の、上部に構築される構造物の沈下低減構造であって、少なくとも構造物の構築面積を内包する平面視断面と、前記液状化層の液状化後に地盤が沈下した際にも、前記構造物を許容沈下量に抑えることのできる層厚を有する地盤改良体が、前記構造物の鉛直同軸上で、液状化層中に水平に構築されることを特徴としている。
【０００７】
請求項２記載の構造物の沈下低減構造は、前記地盤改良体が、複数層に鉛直分割されて、前記液状化層内で所定の離間間隔をもって層状に構築されることを特徴としている。
【０００８】
【発明の実施の形態】
以下、本発明に係る構造物の沈下低減構造を図１から図７に示す。本発明の構造物の沈下低減構造は、表層、もしくは表層の直下に位置する中間層の何れかが地震時に液状化する可能性のある液状化層により構成されている地盤において、液状化層の内方で、前記構造物の鉛直同軸上に、所定の大きさを有する地盤改良体を構築することにより、液状化による地盤沈下が生じた際にも、構造物が位置する領域における地盤沈下量を、他の領域と比較して低減させ、地盤沈下に伴う構造物の沈下量を許容範囲内に収めるものである。
【０００９】
（第１の実施の形態）
図１に示すように、地盤１は、地震の発生に伴い液状化を生じやすい砂層等の液状化層により構成される表層３と、該表層３の直下に位置し、粘性土等の非液状化地盤により構成される中間層２を備えている。また、このような構成の地盤１の上部に構築されている構造物４は、地盤１に対して基礎５を介して支持されており、本実施の形態では、該基礎５に一般的な構造物の基礎として知られている基礎スラブが用いられているが、基礎５の構造は必ずしもこれにこだわるものではない。
【００１０】
また、前記地盤１の表層３には、前記構造物４の鉛直同軸上に地盤改良体６が構築されており、該地盤改良体６は、地盤改良を行う際に一般に用いられるセメント系の固化材料、または液状化対策として用いられている水ガラス系薬液注入材料等により構成されている。これら地盤改良体６の形状は、少なくとも前記構造物４の構築面積を内包する平面視断面を有するとともに、地震等が発生して表層３が一様に液状化し、これに伴い一様な体積ひずみが生じて地盤１全体が表層３の層厚に比例して沈下した際にも、地盤改良体６の構築位置では、地盤１の沈下に伴う構造物４の沈下量を許容範囲内に収めることのできる層厚を有する大きさに成形されている。
【００１１】
したがって、地盤改良体６を構築する際には、あらかじめ地震等の発生に伴う液状化による地盤１の沈下量を予測しておく必要がある。液状化による地盤１の沈下量の算定には、様々な予測手法が検討されているが、その一事例を、以下に詳述する。なお、液状化による地盤１の沈下量の算定に係る予測手法は、精度良く沈下量を予測できる手法であれば、これに限るものではない。
【００１２】
地震等により生じる液状化の後に発生する液状化層の体積ひずみの大きさ（間隙比の変化）は、液状化時に発生した最大せん断ひずみの大きさγ_ｍａｘに依存することが知られている（図３を参照）。このことから、液状化後の砂要素の残留体積ひずみの最大値（ε_ｖｒ）_ｍａｘは、（１）式で示すことができる。
【００１３】
【数１】

【００１４】
ここで、砂の真の最小間隙比ｅ^＊ _ｍｉｎは（２）式で表すことができる。ここで、砂の最大、最小間隙比ｅ_ｍｉｎ、ｅ_ｍａｘは、最小・最大密度試験より求めることが望ましいが、経験的には、細粒分含有率Ｆ_Ｃより、各々（３）（４）の式を用いて求めることができる。
【００１５】
【数２】

【数３】

【数４】

【００１６】
一方、液状化前の砂の間隙比ｅ_０は、砂の最大、最小間隙比ｅ_ｍｉｎ、ｅ_ｍａｘより（５）式で表すことができる。なお、砂の相対密度Ｄｒは、原位置の砂の密度より求められるが、経験的には（７）式に示す地盤の補正Ｎ値Ｎａを用いて（６）式より計算できる。
【００１７】
【数５】

【数６】

【数７】

【００１８】
ところで、液状化時に発生する最大せん断ひずみは、有効応力解析等の手段により求めることができるが、簡易的には、地震時に地盤の各深さに発生する等価繰り返しせん断力比（τ_ｄ／σ’_ｚ）と補正Ｎ値より、図５に示す液状化時の最大せん断ひずみの予測チャートを用いて求めることができる。ここで、等価繰り返しせん断応力比（τ_ｄ／σ’_ｚ）は、（８）式より計算できる。
【００１９】
【数８】

【００２０】
以上の手順により、液状化後の砂の残留体積ひずみの最大値（ε_ｖｒ）_ｍａｘを求められる。砂の細粒分含有率Ｆ_ｃに応じて、補正Ｎ値Ｎａと等価繰り返しせん断応力比（τ_ｄ／σ’_ｚ）から、容易に液状化後の砂の残留体積ひずみの最大値（ε_ｖｒ）_ｍａｘを読みとれるようにした、液状化後の最大残留体積ひずみの予測チャートを図６に示す。
したがって、液状化後の地盤１の沈下量Ｄ_ｓは、（９）式に示すように、液状化後の砂の残留体積ひずみの最大値（ε_ｖｒ）_ｍａｘに液状化層の層厚Ｈを乗じることにより予測できる。
【００２１】
【数９】

【００２２】
上述する方法により算定された、地震等の発生に伴う液状化により生じる地盤１の予測沈下量を考慮し、地盤１の沈下に伴う構造物４の沈下量を、許容範囲内に収めるように層厚を決定された地盤改良体６は、図１に示すように、前記表層３内で構造物４の直下に構築されている。しかし、その高さ位置は、必ずしもこれにこだわるものではなく、図２（ａ）及び（ｂ）に示すように、前記構造物４と鉛直方向の同軸上に位置し、液状化層より構成される表層３中に配置されていれば、何れの高さ位置に配置されても良い。
【００２３】
さらに、該地盤改良体６は、図２（ｃ）に示すように、これを２層に鉛直分割した上で、所定の離間間隔をもって表層３中に層状に構築する構成としても良い。これらは、必ずしも２層に分割する必要はなく、足し合わせた層厚が、地盤１の沈下に伴う構造物４の沈下量を、許容範囲内に収めることのできる層厚を確保していれば、複数に鉛直分割して構築しても良い。
つまり、液状化層より構成される前記表層３中で、かつ前記構造物４の構築位置に対して鉛直方向で同軸上に位置していれば、地盤改良体６をどのように構築しても良い。
【００２４】
このように、構造物４の沈下低減構造は、構造物４が構築されている地盤１の液状化層よりなる表層３の内方で、構造物４と鉛直方向で同軸上となる位置に、構造物４の構築面積を内包する平面視断面と、前記表層３の液状化後に地盤１が沈下した際にも、前記構造物４の沈下を許容沈下量に抑えることのできる層厚を有する地盤改良体６が、構築される構成である。
【００２５】
これにより、地震等により表層３で一様な液状化が発生して体積ひずみが生じ、表層３の層厚に比例した量の地盤１の沈下が全域にわたり生じた場合にも、構造物４が位置する領域における地盤１の沈下量を、他の領域と比較して低減させることができるため、地盤１の沈下に伴う構造物４の沈下量を許容範囲内に収めることができるものである。
また、液状化層よりなる表層３の内方で、構造物４と鉛直方向で同軸上となる位置に、他の領域と比較して剛性の高い前記地盤改良体６が配置されていることから、該地盤改良体６を介して構造物４の鉛直荷重が均等化されるため、構造物４にとって有害な不同沈下を抑制できるものである。
【００２６】
（第２の実施の形態）
第１の実施の形態では、表層３が液状化層により形成されている場合を例に取り、構造物４の沈下低減構造を詳述したが、本構造を適用する地盤１は、必ずしもこれにこだわるものではない。
例えば、図７（ａ）に示すように、非液状化層よりなる表層３と、該表層３の直下に位置し、地震の発生に伴い液状化を生じやすい砂層等の液状化層により構成される中間層２を備える地盤１上に、構造物４を構築する際にも、前記地盤改良体６を、構造物４の鉛直方向の同軸上で前記中間層２内に構築すればよい。
これら地盤改良体６は、前述した平面視断面及び層厚を満足していれば良く、また、その配置高さも、図７（ａ）から（ｃ）に示すように、中間層２の内方であれば、上端部近傍、中間部、下端部近傍の何れでも良い。さらに図７（ｄ）に示すように、地盤改良体６を複数層に鉛直分割して、所定の離間間隔をもって前記中間層２の内方に層状に配置しても良い。
【００２７】
【発明の効果】
請求項１及び２記載の構造物の沈下低減構造は、表層、もしくは該表層の直下に位置する中間層の何れかが、地震時に液状化する可能性のある液状化層により構成されている地盤の、上部に構築される構造物の沈下低減構造であって、少なくとも構造物の構築面積を内包する平面視断面と、前記液状化層の液状化後に地盤が沈下した際にも、前記構造物を許容沈下量に抑えることのできる層厚を有する地盤改良体が、前記構造物の鉛直同軸上で、液状化層中に水平に構築される。
もしくは、前記地盤改良体が、複数層に鉛直分割されて、前記液状化層内で所定の離間間隔をもって層状に構築される。
これにより、地震等により液状化層に一様な液状化が発生して体積ひずみが生じ、液状化層の層厚に比例した量の地盤の沈下が全域にわたり生じた場合にも、構造物が位置する領域における地盤の沈下量を、他の領域と比較して低減させることができるため、地盤の沈下に伴う構造物の沈下量を許容範囲内に収めることが可能となる。
また、液状化層の内方で、構造物と鉛直方向で同軸上となる位置に、他の領域と比較して剛性の高い前記地盤改良体が配置されていることから、該地盤改良体を介して構造物の鉛直荷重が均等化されるため、構造物にとって有害な不同沈下を抑制することが可能となる。
【図面の簡単な説明】
【図１】本発明に係る地盤の沈下低減工法を示す図である。
【図２】本発明に係る地盤の沈下低減工法の他の事例を示す図である。
【図３】本発明に係る砂の相対圧縮指数の最大せん断ひずみ依存性を示すグラフである。
【図４】本発明に係る細粒分含有率とＮ値の補正係数を示すグラフである。
【図５】本発明に係る液状化時に発生する最大せん断ひずみの予測チャートを示すグラフである。
【図６】本発明に係る液状化後の最大体積ひずみ予測チャートを示す図である。
【図７】本発明に係る地盤の沈下低減工法の他の事例を示す図である。
【符号の説明】
１地盤
２中間層
３表層
４構造物
５基礎
６地盤改良体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure for reducing settlement of a structure.
[0002]
[Prior art]
If a structure is constructed on the ground, or a ground layer that is composed of layers that may be liquefied, such as sand layers, the surface layer or the intermediate layer located immediately below the surface layer will liquefy to the surface layer or intermediate layer due to the occurrence of an earthquake, etc. It is conceivable that the ground will sink and the structure will fail. Therefore, for example, as shown in Patent Document 1, measures are taken to prevent the occurrence of liquefaction itself.
[0003]
[Patent Document 1]
JP 05-059717 A (see FIG. 2)
[0004]
[Problems to be solved by the invention]
However, with the above-described configuration, it may be difficult to completely suppress the occurrence of liquefaction, and as the scale of the structure and the layer thickness of the layer that causes liquefaction increase, the construction period becomes longer and the construction cost increases. Various problems have arisen, such as an enormous volume.
[0005]
In view of the above circumstances, an object of the present invention is to provide an inexpensive structure for reducing settlement of structures with a simple configuration.
[0006]
[Means for Solving the Problems]
The structure for reducing settlement of a structure according to claim 1, wherein the surface layer, or an intermediate layer located immediately below the surface layer, is composed of a liquefied layer that may be liquefied during an earthquake, It is a structure for reducing settlement of a structure built on top, and it allows the structure even when the ground sinks after liquefaction of the liquefied layer, and a cross-sectional view including at least the construction area of the structure A ground improvement body having a layer thickness that can be suppressed to the subsidence amount is constructed horizontally in the liquefied layer on the vertical axis of the structure.
[0007]
The structure subsidence reducing structure according to claim 2 is characterized in that the ground improvement body is vertically divided into a plurality of layers, and is constructed in layers with a predetermined spacing in the liquefied layer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
A structure for reducing settlement of a structure according to the present invention is shown in FIGS. The structure settlement reduction structure of the present invention has a structure in which the surface layer or an intermediate layer located immediately below the surface layer is composed of a liquefied layer that may liquefy during an earthquake. The amount of ground subsidence in the region where the structure is located even when ground subsidence due to liquefaction occurs by constructing a ground improvement body having a predetermined size on the vertical axis of the structure inside In comparison with other regions, the amount of subsidence of the structure accompanying the subsidence falls within an allowable range.
[0009]
(First embodiment)
As shown in FIG. 1, the ground 1 is composed of a surface layer 3 composed of a liquefied layer such as a sand layer that is liable to be liquefied due to the occurrence of an earthquake, and a non-liquid state such as a viscous soil located immediately below the surface layer 3. It has an intermediate layer 2 composed of a chemical ground. Moreover, the structure 4 constructed | assembled on the upper part of the ground 1 of such a structure is supported via the foundation 5 with respect to the ground 1, and in this Embodiment, it is a structure common to this foundation 5 Although the basic slab known as the foundation of a thing is used, the structure of the foundation 5 does not necessarily stick to this.
[0010]
In addition, a ground improvement body 6 is constructed on the surface layer 3 of the ground 1 on the vertical axis of the structure 4. The ground improvement body 6 is a cement-based solidification generally used for ground improvement. It is comprised by the material or the water glass type chemical | medical solution injection material etc. which are used as a countermeasure against liquefaction. The shape of the ground improvement body 6 has a cross-sectional view including at least the construction area of the structure 4, and the surface layer 3 is liquefied uniformly due to an earthquake or the like, resulting in uniform volume strain. Even when the ground 1 sinks in proportion to the layer thickness of the surface layer 3, the subsidence amount of the structure 4 accompanying the subsidence of the ground 1 is within an allowable range at the construction position of the ground improvement body 6. It is formed into a size having a layer thickness that can be obtained.
[0011]
Therefore, when the ground improvement body 6 is constructed, it is necessary to predict the amount of settlement of the ground 1 due to liquefaction accompanying the occurrence of an earthquake or the like in advance. Various prediction methods have been studied for calculating the amount of settlement of the ground 1 due to liquefaction, and one example will be described in detail below. In addition, if the prediction method which concerns on calculation of the subsidence amount of the ground 1 by liquefaction is a method which can predict a subsidence amount accurately, it will not be restricted to this.
[0012]
It is known that the volume strain (change in the gap ratio) of the liquefied layer generated after liquefaction caused by an earthquake or the like depends on the magnitude γ _max of the maximum shear strain generated during liquefaction ( (See FIG. 3). From this, the maximum value (ε _vr ) _max of the residual volume strain of the sand element after liquefaction can be expressed by equation (1).
[0013]
[Expression 1]

[0014]
Here, the true minimum clearance ratio e ^* _{min of} sand Can be expressed by equation (2). Here, sand maximum and minimum gap ratios e _min , e _max Is preferably obtained from the minimum / maximum density test, but empirically, it can be obtained from the fine particle content F _C using the equations (3) and (4), respectively.
[0015]
[Expression 2]

[Equation 3]

[Expression 4]

[0016]
On the other hand, the sand gap ratio e ₀ before liquefaction is the maximum sand sand gap ratio e _min , e _max. (5). The relative density Dr of sand can be obtained from the density of the sand at the original position, but can be calculated from the equation (6) using the ground corrected N value Na shown in the equation (7).
[0017]
[Equation 5]

[Formula 6]

[Expression 7]

[0018]
By the way, the maximum shear strain generated at the time of liquefaction can be obtained by means such as effective stress analysis. However, simply, the equivalent repeated shear force ratio (τ _d / σ generated at each depth of the ground during an earthquake) It can obtain | require from the prediction chart of the maximum shear strain at the time of liquefaction shown in FIG. 5 from ' _z ) and correction | amendment N value. Here, the equivalent repeated shear stress ratio (τ _d / σ ′ _z ) can be calculated from the equation (8).
[0019]
[Equation 8]

[0020]
By the above procedure, the maximum value (ε _vr ) _max of the residual volume strain of the sand after liquefaction is obtained. Depending on the fine grain content F _c of the sand, the maximum value (ε _vr ) of the residual volume strain of the sand after liquefaction is easily obtained from the corrected N value Na and the equivalent repeated shear stress ratio (τ _d / σ ' _z ). FIG. 6 shows a prediction chart of the maximum residual volume strain after liquefaction so that _max can be read.
Therefore, the subsidence amount D _s of the ground 1 after liquefaction is obtained by setting the layer thickness H of the liquefied layer to the maximum value (ε _vr ) _max of the residual volume strain of the sand after liquefaction, as shown in Equation (9). Can be predicted by multiplying.
[0021]
[Equation 9]

[0022]
In consideration of the predicted subsidence amount of the ground 1 caused by liquefaction accompanying the occurrence of an earthquake or the like calculated by the method described above, the subsidence amount of the structure 4 accompanying the subsidence of the ground 1 is set to be within an allowable range. As shown in FIG. 1, the ground improvement body 6 whose thickness is determined is constructed in the surface layer 3 immediately below the structure 4. However, the height position is not necessarily limited to this, and as shown in FIGS. 2 (a) and 2 (b), it is located on the same axis as the structure 4 and is composed of a liquefied layer. As long as it is disposed in the surface layer 3, it may be disposed at any height position.
[0023]
Further, as shown in FIG. 2 (c), the ground improvement body 6 may be configured to be divided into two layers and constructed in layers in the surface layer 3 with a predetermined separation interval. These do not necessarily need to be divided into two layers, so long as the combined layer thickness ensures a layer thickness that can keep the amount of settlement of the structure 4 accompanying the settlement of the ground 1 within an allowable range. Alternatively, it may be constructed by dividing vertically into a plurality.
In other words, the ground improvement body 6 can be constructed in any way as long as it is located in the surface layer 3 composed of a liquefied layer and is coaxial with the construction position of the structure 4 in the vertical direction. good.
[0024]
Thus, the settlement reduction structure of the structure 4 is located on the inner side of the surface layer 3 made of the liquefied layer of the ground 1 on which the structure 4 is constructed, at a position that is coaxial with the structure 4 in the vertical direction. A plan view section including the construction area of the structure 4 and a ground having a layer thickness that can suppress the settlement of the structure 4 to an allowable settlement even when the ground 1 sinks after the surface layer 3 is liquefied. The improved body 6 is constructed.
[0025]
As a result, even when liquefaction occurs uniformly in the surface layer 3 due to an earthquake or the like and volume distortion occurs, and the subsidence of the ground 1 in an amount proportional to the layer thickness of the surface layer 3 occurs over the entire region, the structure 4 Since the subsidence amount of the ground 1 in the located region can be reduced as compared with other regions, the subsidence amount of the structure 4 accompanying the subsidence of the ground 1 can be kept within an allowable range.
In addition, the ground improvement body 6 having a higher rigidity than the other regions is disposed at a position coaxial with the structure 4 in the vertical direction inside the surface layer 3 made of the liquefied layer. Since the vertical load of the structure 4 is equalized through the ground improvement body 6, it is possible to suppress the uneven settlement that is harmful to the structure 4.
[0026]
(Second Embodiment)
In the first embodiment, the case where the surface layer 3 is formed of a liquefied layer is taken as an example, and the settlement reduction structure of the structure 4 is described in detail. However, the ground 1 to which this structure is applied is not necessarily limited to this. It is not particular.
For example, as shown in FIG. 7 (a), a surface layer 3 made of a non-liquefied layer and a liquefied layer such as a sand layer which is located directly under the surface layer 3 and is liable to be liquefied due to the occurrence of an earthquake. When the structure 4 is constructed on the ground 1 having the intermediate layer 2, the ground improvement body 6 may be constructed in the intermediate layer 2 on the same axis in the vertical direction of the structure 4.
These ground improvement bodies 6 need only satisfy the above-mentioned cross-sectional view and layer thickness in plan view, and the arrangement height thereof is also inward of the intermediate layer 2 as shown in FIGS. 7 (a) to (c). If so, any of the vicinity of the upper end portion, the intermediate portion, and the vicinity of the lower end portion may be used. Further, as shown in FIG. 7 (d), the ground improvement body 6 may be vertically divided into a plurality of layers and arranged in layers inside the intermediate layer 2 with a predetermined spacing.
[0027]
【The invention's effect】
3. The structure for reducing settlement of structures according to

claim

1 or 2, wherein either the surface layer or an intermediate layer located immediately below the surface layer is composed of a liquefied layer that may be liquefied during an earthquake. A structure for reducing settlement of a structure constructed at the top, wherein the structure includes a cross-sectional view including at least a construction area of the structure, and when the ground is submerged after liquefaction of the liquefied layer A ground improvement body having a layer thickness that can suppress the allowable subsidence amount is constructed horizontally in the liquefied layer on the vertical axis of the structure.
Alternatively, the ground improvement body is vertically divided into a plurality of layers, and is constructed in layers with a predetermined spacing in the liquefied layer.
As a result, even when liquefaction occurs uniformly in the liquefied layer due to an earthquake or the like, volume distortion occurs, and even when the ground subsidence in an amount proportional to the thickness of the liquefied layer occurs over the entire area, Since the amount of ground subsidence in the located region can be reduced as compared with other regions, the amount of subsidence of the structure accompanying the ground subsidence can be kept within an allowable range.
In addition, since the ground improvement body having higher rigidity compared to other regions is disposed at a position coaxial with the structure in the vertical direction inside the liquefaction layer, the ground improvement body is Accordingly, the vertical load of the structure is equalized, so that it is possible to suppress the uneven settlement that is harmful to the structure.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a ground subsidence reduction method according to the present invention.
FIG. 2 is a diagram showing another example of ground subsidence reduction construction method according to the present invention.
FIG. 3 is a graph showing the maximum shear strain dependence of the relative compression index of sand according to the present invention.
FIG. 4 is a graph showing the fine particle content and N value correction coefficient according to the present invention.
FIG. 5 is a graph showing a prediction chart of maximum shear strain generated during liquefaction according to the present invention.
FIG. 6 is a diagram showing a maximum volume strain prediction chart after liquefaction according to the present invention.
FIG. 7 is a diagram showing another example of ground subsidence reduction construction method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ground 2 Intermediate layer 3 Surface layer 4 Structure 5 Foundation 6 Ground improvement body

Claims

Either the surface layer or the intermediate layer located directly below the surface layer is a structure that reduces the settlement of the structure built on top of the ground that is composed of a liquefied layer that may liquefy during an earthquake. And
A cross-sectional view including at least a construction area of the structure, and a ground improvement body having a layer thickness that can suppress the structure to an allowable subsidence amount even when the ground sinks after liquefaction of the liquefied layer. A structure for reducing settlement of a structure, wherein the structure is constructed horizontally in the liquefied layer on the vertical axis of the structure.

In the structure for reducing settlement of a structure according to claim 1,
The subsidence reduction structure for a structure, wherein the ground improvement body is vertically divided into a plurality of layers and is built in layers with a predetermined spacing in the liquefied layer.