JP6600775B2

JP6600775B2 - Ground improvement body and liquefaction damage reduction method using it

Info

Publication number: JP6600775B2
Application number: JP2015109612A
Authority: JP
Inventors: 矢野間敬男
Original assignee: 矢野間敬男
Priority date: 2015-05-29
Filing date: 2015-05-29
Publication date: 2019-11-06
Anticipated expiration: 2035-05-29
Also published as: JP2016223139A

Description

本発明は、小規模建築物（日本建築学会：(1)地上3階以下、(2)建物高さ13ｍ以下、(3)軒高9ｍ以下、(4)延べ面積500ｍ2以下）を対象として、地盤の液状化による被害の低減を目的とする地盤改良体構築を通じた液状化被害低減工法に関するものである。 The present invention is intended for small-scale buildings (The Architectural Institute of Japan: (1) 3 floors or below, (2) Building heights of 13 m or less, (3) Eaves height of 9 m or less, (4) Total area of 500 m2 or less) The present invention relates to a liquefaction damage reduction method through construction of a ground improvement body aimed at reducing damage caused by liquefaction of the ground.

地盤の液状化とは、地震動などの揺れを繰り返して受けることにより、地盤が液状化したように振る舞う現象である。海岸部や埋め立て地、大規模河川下流域周辺の住宅地等に代表される、地下水位が高く、加えて緩く締まった砂質地盤の地域で、地震が引き金となり発生する。そして地盤の大規模な液状化現象が発生すると、住宅地等では建物が沈下・傾倒する被害が多発する。 The liquefaction of the ground is a phenomenon in which the ground behaves as if it is liquefied by repeatedly receiving shaking such as earthquake motion. Earthquakes are triggered in sandy ground areas with high groundwater levels, such as coastal areas, landfills, and residential areas around the downstream of large rivers. If a large-scale liquefaction phenomenon occurs in the ground, buildings will sink and tilt frequently in residential areas.

液状化被害のメカニズムを図１〜図２に基づいて以下に説明する。 The mechanism of liquefaction damage will be described below with reference to FIGS.

図１は、液状化発生前における小規模建築物の基礎地盤を模式的に表した図である。
小規模建築物1の基礎地盤2が砂粒子3を主体としており、この砂粒子3の間隙が水粒子4で満たされたことで地下水位5が高い場合には、地震により地盤の液状化が生じる危険を有する。一方で液状化の危険があるものの、液状化発生前では、一般的に小規模建築物1の建設に必要な地盤支持力8は十分であることから、基礎コンクリート1a（ベタ基礎や布基礎）をベースに建物1bの構築は容易に行える。 FIG. 1 is a diagram schematically showing the foundation ground of a small-scale building before liquefaction occurs.
If the foundation ground 2 of the small-scale building 1 is mainly composed of sand particles 3, and the gap between the sand particles 3 is filled with water particles 4, and the groundwater level 5 is high, the ground liquefies due to the earthquake. There is a danger that arises. On the other hand, although there is a risk of liquefaction, before the liquefaction occurs, since the ground bearing capacity 8 generally required for the construction of small-scale buildings 1 is sufficient, foundation concrete 1a (solid foundation and cloth foundation) Building 1b can be easily constructed based on the above.

図２は、液状化発生後における液状化被害予防策が講じられていない小規模建築物1の液状化被害を模式的に示す図である。
まず、図１に示す様な液状化が生じる危険を有する基礎地盤2において、地震動などの揺れが加わると、地中における砂粒子3の間の接点が離れ、砂粒子3が水中にバラバラで浮いた様な状態になる。そして地震の揺れがそのまま続くと、バラバラで浮いた様な砂粒子3は水より重いため、次第に液状化層9の深層10に向かって密な状態で沈殿を始める。同時に砂より軽い水粒子4は地表に向かって浮き上がり、地表面6では噴水・噴砂13が生じて水浸しとなる。このような液状化メカニズムの中で小規模建築物1を支えていた地盤支持力8は急激に低下し、地上にある小規模建築物1は、砂粒子3と同様に水粒子4より比重が重いために、ゆっくりと土中に沈下14や傾倒15する。これが小規模建築物1における液状化被害である。 FIG. 2 is a diagram schematically showing the liquefaction damage of the small-scale building 1 for which liquefaction damage prevention measures have not been taken after the occurrence of liquefaction.
First, in the foundation ground 2 where there is a risk of liquefaction as shown in Fig. 1, when shaking such as seismic motion is applied, the contact between the sand particles 3 in the ground is released, and the sand particles 3 float apart in the water. It will be like a state. Then, if the shaking of the earthquake continues as it is, the sand particles 3 that seem to float apart are heavier than water, and therefore gradually begin to settle toward the deep layer 10 of the liquefied layer 9 in a dense state. At the same time, the water particles 4 that are lighter than the sand float up toward the surface of the earth, and fountains and sand blasts 13 are generated on the ground surface 6 and become submerged. In such a liquefaction mechanism, the ground bearing capacity 8 that supported the small-scale building 1 rapidly declined, and the small-scale building 1 on the ground has a specific gravity higher than the water particles 4 as well as the sand particles 3. Slowly sink 14 or tilt 15 in the soil due to its heavy weight. This is liquefaction damage in small-scale building 1.

以上のような地盤の液状化による住宅等の被害の低減や防止を目的として様々な工法が提案されている。 Various construction methods have been proposed for the purpose of reducing or preventing damage to houses due to liquefaction of the ground as described above.

例えば、地上建物の底面に連結させた基礎杭や鋼製矢板等を地下深部に挿入して液状化時における建物の沈下や傾倒の低減・防止を図る杭工法や矢板工法が存在する。（特許文献１）（特許文献２） For example, there are a pile method and a sheet pile method for inserting a foundation pile or a steel sheet pile connected to the bottom of an aboveground building into a deep underground to reduce or prevent the settlement and tilting of the building during liquefaction. (Patent Document 1) (Patent Document 2)

例えば、地上建物の直下地盤に透水性を有する採石杭や排水ドレーンを設置して液状化発生時に排水を促し液状化の発生を抑制する地下水排除工法が存在する。（特許文献３） For example, there is a groundwater draining method that installs permeable quarry piles and drainage drains on the ground floor of an aboveground building to promote drainage and suppress the occurrence of liquefaction when liquefaction occurs. (Patent Document 3)

例えば、地上建物の直下地盤に砂柱等を振動・圧入構築して周辺地盤を締め固めて液状化しにくくする締め固め工法が存在する。（特許文献４） For example, there is a compaction method in which a sand column or the like is vibrated and press-fitted on a direct ground base of a ground building to consolidate the surrounding ground and make it difficult to liquefy. (Patent Document 4)

例えば、地上建物の直下地盤を地盤改良材などで固化させて建物の沈下や傾倒の低減を図る地盤改良工法が存在する。（特許文献５）（特許文献６） For example, there is a ground improvement method for reducing the sinking and tilting of a building by solidifying a direct ground base of a ground building with a ground improvement material or the like. (Patent Document 5) (Patent Document 6)

しかし上述に代表される、液状対策の工法は、工事が大がかりで非常に高価な傾向にあり、一般的な住宅等の小規模建築物の建設において採用されることは多くない。 However, the liquid countermeasure methods represented by the above are tending to be very expensive due to the large construction, and are not often employed in the construction of small-scale buildings such as ordinary houses.

特開2014−125730JP 2014-125730 特開2014−31706JP 2014-31706 特開2013−155558JP2013-155558 特開2015−59350JP2015-59350 特開2013−204405JP2013-204405 特開2014−47565JP 2014-47565

本発明が解決しようとする課題は、小規模建築物を対象として、地盤の液状化による被害の低減を目的とする、施工が容易で環境に優しく低コストな地盤改良体の構築を通じた液状化被害低減工法の創造である。 The problem to be solved by the present invention is to liquefy through the construction of a ground improvement body that is easy to construct, environmentally friendly and low-cost, aimed at reducing damage caused by liquefaction of the ground for small-scale buildings. The creation of damage reduction methods.

本発明は、現地発生土を主要な材料とする施工が容易で環境に優しく低コストな地盤改良体を、小規模建築物の直下地盤内に構築し、液状化発生時における地上の小規模建築物の沈下被害や傾倒被害の発生を軽減することを特徴とする液状化被害低減工法である。 The present invention constructs a ground improvement body that is easy to construct, mainly environmentally friendly and low-cost in the direct foundation board of a small-scale building, and uses small-scale buildings on the ground when liquefaction occurs. This liquefaction damage reduction method is characterized by reducing the occurrence of subsidence damage and tilt damage.

上記に記述する地盤改良体とは、小規模建築物の直下地盤に穴を掘削し、その穴の底面に梯子胴木を設置し、この上に大型土嚢の集合体を層状に積み重ねて構築される、梯子胴木と大型土嚢の集合体とが一体と成す構造である。 The ground improvement body described above is constructed by excavating a hole in the direct foundation board of a small-scale building, installing a ladder shell on the bottom of the hole, and stacking large sandbags in layers on this. The ladder shell and the large sandbag assembly are integrated.

上記に記述する梯子胴木とは、地盤を掘削した穴の底面を均して設置する格子状の支えである。液状化発生時の生じる急激な地盤支持力の低下で、大型土嚢の集合体が不同沈下を起こし、その形を崩すことを防止することを目的とする。 The ladder trunk described above is a grid-like support in which the bottoms of holes excavated in the ground are leveled. The purpose is to prevent the large sandbag aggregate from causing a subsidence due to the sudden decrease in ground bearing capacity that occurs when liquefaction occurs, and to prevent its shape from collapsing.

上記に記述する大型土嚢の集合体とは、液状化発生時でも大型土嚢（φ1.0m×H1.0ｍほどのポリプロピレン性）がバラバラにならないよう、土木シート（化学繊維系の高強度のシート）で大型土嚢を強く巻く作業を層状に繰り返して構築される集合体である。液状化発生時でも変形しづらい土の塊を造ることを目的とする。 The large sandbag aggregate described above is a civil engineering sheet (chemical fiber high-strength sheet) so that the large sandbag (polypropylene of φ1.0m x H1.0m) does not fall apart even when liquefaction occurs It is an assembly constructed by repeating the process of winding a large sandbag strongly in layers. The purpose is to create a lump of soil that is difficult to deform even when liquefaction occurs.

本発明である液状化被害低減工法の実施により構築される地盤改良体は、その比重が、液状化で地上に噴出する水よりは重いが沈殿する砂よりは軽い或いは同等質量であり、また砕石系やセメント系の地盤改良工法と比べて軽い。このため、液状化の発生により地盤支持力が急減しても地盤改良体の上に構築される小規模建築物は沈下しにくい。 The ground improvement body constructed by the implementation of the liquefaction damage reducing method according to the present invention has a specific gravity that is heavier than water squirted on the ground by liquefaction, but lighter or equivalent in weight than sedimented sand, and crushed stone It is lighter than the ground improvement method of cement and cement. For this reason, even if the ground supporting force decreases rapidly due to the occurrence of liquefaction, a small-scale building constructed on the ground improvement body is unlikely to sink.

本発明である液状化被害低減工法の実施により構築される地盤改良体は、地震による揺れが続いても中詰め土は液状化により形を崩すことなくおおむね形を維持し、地上の小規模建築物を支えつづける。 The ground improvement body constructed by the implementation of the liquefaction damage reduction method according to the present invention is that the padded soil maintains a general shape without losing its shape due to liquefaction even if shaking due to an earthquake continues, and a small-scale building on the ground Continue to support things.

本発明である液状化被害低減工法は、現地発生土砂を主要な材料とする地盤改良体を基礎として、この上に小規模建築物を構築することで、液状化による地上の小規模建築物の沈下や傾倒の被害は軽減される。 The liquefaction damage reduction method according to the present invention is based on a ground improvement body that uses locally generated sediment as the main material, and a small-scale building is constructed on top of this. The damage of sinking and tilting is reduced.

本発明である液状化被害低減工法は、小規模建築物の基礎地盤を掘り込み、そこに地盤改良体を構築するだけの工事であり、比較的に簡単な工事である利点ある。 The liquefaction damage reducing method according to the present invention is an operation that only involves digging the foundation ground of a small-scale building and constructing a ground improvement body there, and has the advantage of being a relatively simple construction.

本発明である液状化被害低減工法の実施により構築される地盤改良体の材料は、土砂を詰める大型土嚢や土木シート、梯子胴木など安価であり、また大型土嚢の中詰め材に現地発生土砂をほぼ全て使い果たすことから建設廃材となる残土はほぼ無く、他工法と比較して低コストの利点がある。 The material of the ground improvement body constructed by the implementation of the liquefaction damage reduction method according to the present invention is inexpensive, such as large sandbags, civil engineering sheets, ladder shells, etc., which are filled with earth and sand. Since there is almost no remaining soil as construction waste, there is an advantage of low cost compared to other construction methods.

本発明である液状化被害低減工法は、地下水の抜き取りや、土中への地盤改良剤の圧力注入、振動による地盤の締め固め等の周辺環境を変化させるような作業を必要とせず、環境に優しい利点がある。 The liquefaction damage reduction method according to the present invention does not require work that changes the surrounding environment, such as extraction of groundwater, pressure injection of ground improver into the soil, and compaction of the ground due to vibration. There is a gentle advantage.

液状化発生前における小規模建築物の基礎地盤を模式的に表した図である。It is the figure which represented typically the foundation ground of the small-scale building before liquefaction generation | occurrence | production. 液状化発生後における液状化被害予防策が講じられていない小規模建築物の液状化被害を模式的に示す図である。It is a figure which shows typically the liquefaction damage of the small-scale building in which the liquefaction damage prevention measure is not taken after liquefaction generation | occurrence | production. 本発明である液状化被害低減工法の規模・構造を決める根拠となった小規模建築物における液状化被害の分析結果を示す図である。It is a figure which shows the analysis result of the liquefaction damage in the small-scale building used as the basis which determines the scale and structure of the liquefaction damage reduction construction method which is this invention. 本発明である液状化被害低減工法の概要を示す図である。It is a figure which shows the outline | summary of the liquefaction damage reduction construction method which is this invention. 本発明に含まれる梯子胴木の構築方法について模式的に示す図である。It is a figure which shows typically about the construction method of the ladder trunk | drum included in this invention. 本発明に含まれる梯子胴木の構造について模式的に示す図である。It is a figure showing typically about the structure of a ladder shell included in the present invention. 本発明に含まれる大型土嚢の集合体の概要を模式的に示す図である。It is a figure which shows typically the outline | summary of the aggregate | assembly of the large sandbag included in this invention. 本発明の資材の一つである大型土嚢の詳細を模式的に示す図である。It is a figure which shows typically the detail of the large sandbag which is one of the materials of this invention. 土木シートで複数の大型土嚢を強く巻き、大型土嚢の集合体を構築する方法について模式的に示す図である。It is a figure showing typically about a method of winding up a plurality of large sandbags with a civil engineering sheet, and constructing an aggregate of large sandbags. 梯子胴木の上に、土木シートで複数の大型土嚢を強く巻く作業を層状に繰り返して大型土嚢の集合体を構築する、その工程の全容を模式的に示した図である。It is the figure which showed typically the whole process of constructing the aggregate | assembly of a large sandbag by repeating the operation | work which winds several large sandbags strongly with a civil engineering sheet in a layer form on a ladder trunk.

本発明を図３〜図１０に基づいて以下に説明する。 The present invention will be described below with reference to FIGS.

図３は、本発明である液状化被害低減工法の規模・構造を決める根拠となった、小規模建築物1における液状化被害の分析結果を示す図である。
小規模建築物1の液状化被害の事例を調べると、小規模建築物1の沈下深16は1.0〜2.5ｍ程の事例が多い。このことは1.0〜2.5ｍ程が小規模建築物1の沈下14や傾倒15が止まるおおよその深さということであり、その深さ付近には小規模建築物1の沈下14や傾倒15を軽減するだけの地盤支持力8が残っていると分析する。 FIG. 3 is a diagram showing an analysis result of the liquefaction damage in the small-scale building 1, which is the basis for determining the scale and structure of the liquefaction damage reduction method according to the present invention.
Examining the case of liquefaction damage of small building 1, there are many cases of subsidence depth 16 of small building 1 of about 1.0-2.5m. This means that about 1.0 to 2.5m is the approximate depth at which the settlement 14 and tilt 15 of the small-scale building 1 stop, and the settlement 14 and tilt 15 of the small-scale building 1 are reduced near that depth. Analyze that there is enough ground support capacity 8 to do.

図４は、図３の分析の結果を基にして開発した、本発明である液状化被害低減工法の概要を示す図である。
この液状化被害低減工法とは、図３に示す液状化発生時に1.0〜2.5ｍ程の深さに残留する地盤支持力8でも、小規模建築物1の沈下14や傾倒15が生じづらい特徴を有した、図４に示す地盤改良体17を構築するものである。ちなみに地盤改良体17とは、掘削した穴18の底面に設置した梯子胴木19と、この上に設置する現地発生土を詰めた大型土嚢の集合体20とが一体を成し、小規模建築物1の液状化被害低減の効果を発揮するものである。
このうち梯子胴木19とは格子状の支えであり、液状化発生時の生じる急激な地盤支持力8の低下で、大型土嚢の集合体20が不同沈下を起こし、その形を崩すことを防止することを目的とする。
このうち大型土嚢の集合体20とは、現地発生土砂を入れて突き固めた水密性のある大型土嚢が液状化発生時でもバラバラにならないよう、土木シートで複数の大型土嚢を強く巻く作業を層状に繰り返して構築する集合体である。液状化発生時でも変形しづらい土の塊を造ることを目的とする。 FIG. 4 is a diagram showing an outline of the liquefaction damage reducing method according to the present invention, which was developed based on the analysis result of FIG.
This liquefaction damage reduction method is characterized in that subsidence 14 and tilting 15 of small-scale buildings 1 are difficult to occur even with ground bearing capacity 8 remaining at a depth of about 1.0 to 2.5 m when liquefaction occurs as shown in FIG. The ground improvement body 17 shown in FIG. 4 is constructed. By the way, the ground improvement body 17 is a small-scale building consisting of a ladder shell 19 installed on the bottom of the excavated hole 18 and a large sandbag assembly 20 filled with locally generated soil installed on top of this. Demonstrates the effect of reducing the liquefaction damage of object 1.
Of these, the ladder trunk 19 is a grid-like support that prevents the large sandbag aggregate 20 from causing subsidence due to the sudden drop in the ground support force 8 that occurs when liquefaction occurs, thereby preventing the collapse of its shape. The purpose is to do.
Of these, large sandbag aggregate 20 is a layered work that strongly winds multiple large sandbags with civil engineering sheets so that the watertight large sandbags that have been squeezed and solidified with locally generated sand and sand do not break apart even when liquefaction occurs It is an aggregate that is built repeatedly. The purpose is to create a lump of soil that is difficult to deform even when liquefaction occurs.

図５は、本発明に含まれる梯子胴木19の構築方法について模式的に示す図である。
施工では、まず図４に示す小規模建築物1の基礎地盤2に、図５で示すような穴18を掘削する。穴18の深さは2〜3m程を標準とする。掘削の広さは、小規模建築物1の底面積より広くすることを原則として、小規模建築物1の底面の四方向に、最小でも掘削深と同じ長さ以上を確保する。広いほど良い。次いで、掘削した穴18の底面に梯子胴木19を設置し、梯子胴木19の隙間には現地で採取した土砂21を充填して平らに均す。 FIG. 5 is a diagram schematically showing a construction method of the ladder trunk 19 included in the present invention.
In construction, a hole 18 as shown in FIG. 5 is first excavated in the foundation ground 2 of the small-scale building 1 shown in FIG. The standard depth of the hole 18 is about 2 to 3 m. As a general rule, the area of excavation should be larger than the bottom area of the small-scale building 1, and at least the same length as the excavation depth should be secured in the four directions on the bottom of the small-scale building 1. The wider the better. Next, a ladder trunk 19 is installed on the bottom of the excavated hole 18, and the gap between the ladder trunks 19 is filled with earth and sand 21 collected at the site and leveled.

図６は、本発明に含まれる梯子胴木19の構造について模式的に示す図である。
梯子胴木19の材質は、軽量なものが望ましく、図６では角形断面の木材19aを利用する例を示す。角形断面の木材19aは一般的に長さ4ｍものの販売が主流であるため、おのおのの木材19aは縦方向にボルト・ナット19bで結合する。また縦方向にボルト・ナット19bで結合した木材19aは、さらに横方向にもボルト・ナット19bにより結合する。
その他、梯子胴木19の材質としては、中空の鋼製角パイプやH型鋼も有効と考える。
以上の様な構造の梯子胴木19の設置を通じて、この上に構築する大型土嚢の集合体20を支えられるようにする。 FIG. 6 is a diagram schematically showing the structure of the ladder trunk 19 included in the present invention.
The material of the ladder trunk 19 is preferably lightweight, and FIG. 6 shows an example in which a wood 19a having a square cross section is used. Since the wood 19a having a square cross section is generally sold with a length of 4 m, each wood 19a is joined in the longitudinal direction with bolts and nuts 19b. Further, the wood 19a joined in the vertical direction with the bolts and nuts 19b is further joined in the lateral direction with the bolts and nuts 19b.
In addition, as the material of the ladder trunk 19, a hollow steel square pipe or H-shaped steel is also considered effective.
Through the installation of the ladder trunk 19 having the above-described structure, the large sandbag assembly 20 constructed thereon can be supported.

図７は、本発明に含まれる大型土嚢の集合体20の概要を模式的に示す図である。
大型土嚢の集合体20とは、現地発生土砂を入れて突き固めた水密性のある大型土嚢が液状化発生時でもバラバラにならないよう、土木シート20aで大型土嚢20bを強く巻く作業を層状に繰り返して構築する集合体である。
各層の構築では、まず梯子胴木19の上に透水性を有した高強度の土木シート20aを広げる。次いでこの上に現地発生土を中詰材とする大型土嚢20bを密に並べて、土木シート20aで強く巻く。続いて層状にこの作業を繰り返す。なお各層の大型土嚢の集合体20は一体性を確保するために異形棒鋼などの金具20cを挿して連結させる。これにより厚みのある層状を呈した大型土嚢の集合体20が構築される。
土砂は地震による揺れが加わると容易に形を崩してしまうが、以上、土砂を大型土嚢に詰めてから集合体として構築することで、液状化発生時でも変形しづらい土の塊を造ることが可能となる。
最後に、梯子胴木19の設置と大型土嚢の集合体20で一体を成す地盤改良体17の周囲は、現地で採取した土砂21にて埋め戻す。
以上の作業を通じて構築した地盤改良体17の上に、小規模建築物1を構築する。 FIG. 7 is a diagram schematically showing an outline of a large sandbag assembly 20 included in the present invention.
The large sandbag aggregate 20 is a layered process in which the large sandbag 20b is strongly wound with the civil engineering sheet 20a in a layered manner so that the watertight sandbag that has been solidified with the locally generated sand and sand does not fall apart even when liquefaction occurs This is an aggregate constructed.
In the construction of each layer, first, a high-strength civil engineering sheet 20 a having water permeability is spread on the ladder trunk 19. Next, large sandbags 20b using locally generated soil as a filling material are arranged closely on top of each other, and are strongly wound with a civil engineering sheet 20a. Subsequently, this operation is repeated in layers. The large sandbag aggregate 20 of each layer is connected by inserting a metal fitting 20c such as a deformed steel bar in order to ensure unity. Thus, a large sandbag aggregate 20 having a thick layer shape is constructed.
Sediment easily loses its shape when shaken by an earthquake, but as described above, it is possible to create a lump of soil that is difficult to deform even when liquefaction occurs by constructing it as an aggregate after packing it in a large sandbag. It becomes possible.
Finally, the surroundings of the ground improvement body 17 that are integrated with the installation of the ladder trunk 19 and the large sandbag aggregate 20 are backfilled with earth and sand 21 collected locally.
The small-scale building 1 is constructed on the ground improvement body 17 constructed through the above operations.

図８は、本発明の資材の一つである大型土嚢20bの詳細を模式的に示す図である。
大型土嚢20bの中詰め材には、小規模建築物1の基礎地盤2に穴18を掘削した際に発生する現地で採取した土砂21を利用することとする。なお大型土嚢20bの材質は、地震時における揺れで、大型土嚢20bの内部に過剰な水が入り込み、大型土嚢20bに中詰めした土砂21が液状化を起こして緩まないよう、透水性が低いものとする。ただし透水性の低さは厳密なものではなく、一般的に市販されている大型土嚢20bの材質で十分である。逆に漏水も許さない材質の大型土嚢20bは、液状化発生時において、大型土嚢20bに土砂21を中詰めする祭に混入する空気が逃げ場を失い強い浮力を生じさせるため、採用してはならない。
なお大型土嚢20bの軽量化を目的に、中詰めする土砂21の土質強度が著しく低下しない範囲で、中詰めする土砂21に木質チップ等を混入させてもよい。 FIG. 8 is a diagram schematically showing details of a large sandbag 20b which is one of the materials of the present invention.
As the filling material for the large sandbag 20b, the earth and sand 21 collected when the hole 18 is excavated in the foundation ground 2 of the small-scale building 1 is used. The material of the large sandbag 20b is low permeability so that excessive water will enter the large sandbag 20b due to shaking during the earthquake, and the earth and sand 21 packed in the large sandbag 20b will not liquefy and loosen And However, the low water permeability is not strict, and the material of the large sandbag 20b that is generally commercially available is sufficient. On the other hand, large sandbags 20b that do not allow water leakage should not be used when liquefaction occurs because the air mixed into the festival that fills the sand and sand 21 into the large sandbags 20b loses escape and creates strong buoyancy. .
For the purpose of reducing the weight of the large sandbag 20b, wood chips or the like may be mixed in the earth and sand 21 to be packed in the range in which the soil strength of the earth and sand 21 to be packed is not significantly reduced.

図９は、土木シート20aで大型土嚢20bを強く巻き、大型土嚢の集合体20を構築する方法について模式的に示す図である。
まず、梯子胴木19の上に、透水性を有した高強度の土木シート20aを広げる。なお土木シート20aは、大型土嚢20bを強く巻くことが可能な高強度のものとし、また液状化発生時において、大型土嚢の土砂中詰め時に混入した空気が逃げ場を失い強い浮力を生じないよう透水性のあるものとする。なお土木シート20aは、幅2ｍ程度のロール状での入手が一般的であるため、おのおのの土木シート20aの間は十分にオーバーラップ或いは結合させて一体性を確保する。
次いで土木シート20aの上に大型土嚢20bを置くが、大型土嚢20bの置き方は、まず設置面の中心には大型土嚢20bを置かずに空けて、設置面の外周のみに大型土嚢20bを密に並べる。そして梯子胴木19の上に広げてあった土木シート20aにて、設置面の外周に並べた大型土嚢20bを包み込むように、設置面の中心の凹みに向かって巻く。その際、設置面の中心の凹み部の土木シート20aは、端部を固定して張らせておく。
土木シート20aで大型土嚢20bを強く巻くには、大型土嚢20bの重さを利用することとする。すなわちその方法は、大型土嚢20bの設置面の中心の凹み部に張らせた土木シート20aの上に、大型土嚢20bを下ろし、その重さで緊迫させることとする。
以上の工程を通じて、大型土嚢の集合体20の最下層を構築するものとする。 FIG. 9 is a diagram schematically showing a method of constructing a large sandbag aggregate 20 by strongly winding a large sandbag 20b with a civil engineering sheet 20a.
First, a high-strength civil engineering sheet 20 a having water permeability is spread on the ladder trunk 19. The civil engineering sheet 20a should be of a high strength that allows the large sandbag 20b to be wound strongly, and in the event of liquefaction, the air mixed in when the large sandbag is filled in the sand will lose its escape and generate strong buoyancy. It shall be a sex. Since the civil engineering sheet 20a is generally obtained in a roll shape having a width of about 2 m, the civil engineering sheets 20a are sufficiently overlapped or joined together to ensure unity.
Next, the large sandbag 20b is placed on the civil engineering sheet 20a. The large sandbag 20b is placed in the center of the installation surface without placing the large sandbag 20b, and the large sandbag 20b is densely placed only on the outer periphery of the installation surface. Line up. Then, the civil engineering sheet 20a spread on the ladder trunk 19 is wound toward the dent at the center of the installation surface so as to wrap the large sandbag 20b arranged on the outer periphery of the installation surface. At that time, the civil engineering sheet 20a in the recessed portion at the center of the installation surface is stretched with its ends fixed.
In order to wind the large sandbag 20b strongly with the civil engineering sheet 20a, the weight of the large sandbag 20b is used. That is, in this method, the large sandbag 20b is lowered on the civil engineering sheet 20a stretched in the central recess of the installation surface of the large sandbag 20b, and is tightened by its weight.
It is assumed that the lowermost layer of the large sandbag aggregate 20 is constructed through the above steps.

図１０は、梯子胴木19の上に、土木シート20aで大型土嚢20bを強く巻く作業を層状に繰り返して大型土嚢の集合体20を構築する、その工程の全容を模式的に示した図である。
まず（A）の通り、小規模建築物1を建設予定の基礎地盤2に穴18を掘削する。そして穴18の底面に梯子胴木19を設置する。次いで梯子胴木19の上に、土木シート20aを広げ、この上に大型土嚢20bを置いて、これを土木シート20aで強く巻く。
すると（B）の通り、最下層の大型土嚢の集合体20が構築される。
次いで（C）から（E）の通り、土木シート20aで大型土嚢20bを強く巻く作業を層状に繰り返して、大型土嚢の集合体20の厚みを増幅させる。その祭、各段の大型土嚢の集合体20は一体性を確保するために異形棒鋼などの金具20cを挿して連結させる。
最後に（F）の通り、梯子胴木19の設置と大型土嚢の集合体20で一体を成す地盤改良体17が構築されるが、その周囲は現地で採取した土砂21で埋め戻す。
以上の作業で構築した地盤改良体17の上に、小規模建築物1を建設する。 FIG. 10 is a diagram schematically showing the entire process of constructing a large sandbag aggregate 20 by repeatedly stratifying a large sandbag 20b with a civil engineering sheet 20a on a ladder trunk 19 in a layered manner. is there.
First, as shown in (A), a hole 18 is drilled in the foundation ground 2 where the small-scale building 1 is scheduled to be constructed. Then, a ladder trunk 19 is installed on the bottom of the hole 18. Next, the civil engineering sheet 20a is spread on the ladder trunk 19, and a large sandbag 20b is placed thereon, and this is strongly wound with the civil engineering sheet 20a.
Then, as shown in (B), the aggregate 20 of large sandbags in the lowermost layer is constructed.
Next, as shown in (C) to (E), the operation of strongly winding the large sandbag 20b with the civil engineering sheet 20a is repeated in layers to amplify the thickness of the large sandbag aggregate 20. At that festival, the large sandbag assembly 20 of each step is connected by inserting a metal fitting 20c such as a deformed steel bar in order to ensure unity.
Finally, as shown in (F), a ground improvement body 17 is constructed, which is composed of the ladder trunk 19 and the large sandbag assembly 20, but the surrounding area is backfilled with the earth and sand 21 collected locally.
The small-scale building 1 is constructed on the ground improvement body 17 constructed by the above operations.

1 小規模建築物
1a 基礎コンクリート
1b 建物
2 基礎地盤
3 砂粒子
4 水粒子
5 地下水位
6 地表面
7 堅地盤
8 地盤支持力
9 液状化層
10 深層
11 表層
12 水面
13 噴砂・噴水
14 沈下
15 傾倒
16 沈下深
17 地盤改良体
18 穴
19 梯子胴木
19a 木材
19b ボルト・ナット
20 大型土嚢の集合体
20a 土木シート
20b 大型土嚢
20c 金具
21 土砂
1 Small building
1a Foundation concrete
1b building
2 Foundation ground
3 Sand particles
4 water particles
5 Groundwater level
6 Ground surface
7 Solid ground
8 Ground bearing capacity
9 Liquefaction layer
10 deep
11 Surface
12 Water surface
13 Sand blowing / fountain
14 Settlement
15 Tilt
16 Settlement depth
17 Ground improvement body
18 holes
19 Ladder shell
19a wood
19b Bolt / Nut
20 Large sandbag assembly
20a Civil engineering sheet
20b large sandbag
20c bracket
21 earth and sand

Claims

基礎地盤を深さ２ｍから３ｍ掘削した穴の底面に設置する梯子胴木と、当該現場掘削により生じる建設廃材なり得る掘削土砂を詰めた大型土嚢と、前記の大型土嚢を複数用意しこれを土木シートで巻き固めて作る前記の梯子胴木の上に乗せることを前提とする大型土嚢の集合体と、或いは、前記の大型土嚢を複数用意しこれを土木シートで巻き固めて作る前記の梯子胴木の上に乗せることを前提とする大型土嚢の集合体が２段積から４段積である場合には、各層を金具を用いて連結させて作る複数層の大型土嚢の集合体とが、一体構造となった液状化被害低減のための地盤改良体。
Prepare ladder ladders installed at the bottom of holes drilled from 2m to 3m deep in the foundation ground, large sandbags filled with excavated earth and sand that can be construction waste generated by the site excavation, and multiple large sandbags. An assembly of large sandbags that are presupposed to be placed on the ladder trunks that are rolled and consolidated with a sheet , or the ladder trunks that are prepared by winding a plurality of the large sandbags and winding them with a civil engineering sheet When the large sandbag assembly on the assumption that it is placed on the tree is a two-tiered to four-tiered product, there are multiple layers of large sandbags made by connecting each layer using metal fittings, Ground improvement body to reduce liquefaction damage that has an integrated structure .

前記の大型土嚢は、サイズを直径１．０ｍ×高さ１．０ｍ程を有することを特徴とする、また、前記の大型土嚢に詰める掘削土砂に追加で混入させる木質チップおよび木質チップ以外の他の物質は、地盤液状化時に地上に噴出する水よりは重いが地中に沈む砂よりは軽い或いは同等質量であることを特徴とする、請求項１に記載の液状化被害低減のための地盤改良体。
The large sandbag has a size of about 1.0 m in diameter and 1.0 m in height, and other than the wood chip and the wood chip to be additionally mixed in the excavated sand filled in the large sandbag. 2. The ground for reducing liquefaction damage according to claim 1, wherein the material is heavier than the water ejected to the ground during ground liquefaction but lighter than sand sinking in the ground or has an equivalent mass. Improved body.

前記の梯子胴木が、液状化発生時に前記の大型土嚢の集合体から離れて地中深部に向かって沈まぬよう砂よりは軽い或いは同等質量の角形断面の木材や中空の鋼材角パイプを用いることを特徴とする、或いは前記の大型土嚢の集合体と連結させて前記の大型土嚢の集合体から離れて地中深部に向かって沈まぬようにしたH型鋼材を用いることを特徴とする、請求項１に記載の液状化被害低減のための地盤改良体。
The ladder shell is made of a square steel or hollow steel square pipe having a square cross section that is lighter than or equal to the sand so as not to sink away from the large sandbag aggregate when liquefaction occurs and sink into the deep underground. It is characterized by using an H-shaped steel material that is connected to the large sandbag assembly and is not separated from the large sandbag assembly and sinks toward the deep underground, The ground improvement object for liquefaction damage reduction of Claim 1 .

前記の大型土嚢を複数用意しこれを土木シートで巻き固めて作る前記の梯子胴木の上に乗せることを前提とする大型土嚢の集合体が、２段積から４段積である場合には、各層の境に異形棒鋼の金具を挿すなどして連結させることを特徴とする、請求項１に記載の液状化被害低減のための地盤改良体。
When the large sandbag assembly is prepared by placing a plurality of the large sandbags and winding them on a civil engineering sheet on the ladder trunk, the large sandbag is a two-tier product to a four-tier product. 2. The ground improvement body for reducing liquefaction damage according to claim 1, wherein a metal bar of a deformed steel bar is inserted and connected to the boundary of each layer .

基礎地盤を掘削し形成した穴の底面に格子状の支保的な構造体である梯子胴木を設置し、前記の梯子胴木の上に土木シートを広げ、前記の土木シートの上に中詰め材を詰めた大型土嚢を複数個並べ、前記の大型土嚢を前記の土木シートで強く巻き固めることにより大型土嚢の集合体を形成し、前記の大型土嚢の集合体を層状に積み重ねて、前記の大型土嚢の集合体の各層を連結し一体化させることを通じて形成する、請求項１に記載の地盤改良体の上に、小規模建築物を建設する液状化被害低減工法。
Ladder bridges, which are lattice-like supporting structures, are installed on the bottom of the holes formed by excavating the foundation ground, and a civil engineering sheet is spread on the ladder trunks, and the padding is placed on the civil engineering sheet. Arranging a plurality of large sandbags filled with materials, forming a large sandbag aggregate by strongly winding and solidifying the large sandbag with the civil engineering sheet, stacking the large sandbag aggregates in layers, The liquefaction damage reduction construction method for constructing a small-scale building on the ground improvement body according to claim 1, which is formed by connecting and integrating the layers of the large sandbag aggregate.