JP7482817B2 - How to build a foundation for a new building - Google Patents

How to build a foundation for a new building Download PDF

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JP7482817B2
JP7482817B2 JP2021042976A JP2021042976A JP7482817B2 JP 7482817 B2 JP7482817 B2 JP 7482817B2 JP 2021042976 A JP2021042976 A JP 2021042976A JP 2021042976 A JP2021042976 A JP 2021042976A JP 7482817 B2 JP7482817 B2 JP 7482817B2
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treated soil
slab
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JP2022142687A (en
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亮太 高橋
晃輔 川田
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Taisei Corp
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Description

本発明は、既存躯体の上に新設建物の基礎を構築する方法に関する。 This invention relates to a method for constructing a foundation for a new building on an existing structure.

従来より、既存建物の基礎を残した状態で、新設建物を構築することが提案されている（特許文献１、２参照）。
特許文献１では、既存建物の地下が地下外壁と基礎スラブを残して解体されており、その基礎スラブ上に流動化処理土が打設され、その流動化処理土の上に土砂が埋め戻されて、地下外壁で囲まれた内部に新規地盤が造成され、その新規地盤に流動化処理土まで到達するソイルセメントコラムが造成されている。
特許文献２には、地盤沈下により支持杭で支持された既存のフーチング底面と地盤との間に生じた空隙部に流動化処理土を充填する工法が示されている。具体的には、フーチング上面からフーチングを貫通して空隙部へ到達する注入孔をコアボーリングにより１カ所穿設し、流動化処理土を、前記注入孔を通して空隙部に注入して充填する。 It has been proposed to construct a new building while leaving the foundation of an existing building in place (see Patent Documents 1 and 2).
In Patent Document 1, the basement of an existing building is demolished leaving only the basement exterior walls and foundation slab, and liquefied treated soil is poured on top of the foundation slab. Then, soil and sand are backfilled on top of the liquefied treated soil to create new ground within the area surrounded by the basement exterior walls, and a soil cement column is constructed in the new ground, reaching the liquefied treated soil.
Patent Document 2 shows a method of filling liquefied treated soil into a gap that has arisen between the ground and the bottom surface of an existing footing supported by support piles due to ground subsidence. Specifically, an injection hole is drilled by core boring in one place, penetrating the footing from the top surface of the footing to reach the gap, and liquefied treated soil is injected through the injection hole into the gap to fill it.

特開２００３－１４７７８２号公報JP 2003-147782 A 特開２０１０－１８０６３３号公報JP 2010-180633 A

本発明は、既存建物を解体した後に新設建物の基礎を構築する際に、新設建物の地盤を短工期で形成できる、新設建物の基礎の構築方法を提供することを課題とする。 The objective of the present invention is to provide a method for constructing a foundation for a new building that can form the foundation for the new building in a short construction period when constructing the foundation for the new building after demolishing an existing building.

第１の発明の新設建物の基礎の構築方法は、既存躯体（例えば、後述の既存地下躯体２）の上に新設建物の基礎（例えば、後述の新設建物の基礎１）を構築する方法であって、前記既存躯体は、下側スラブ（例えば、後述の耐圧盤１１、地下２階床スラブ１３）と、当該下側スラブの上に内部空間（例えば、後述のピット１４、内部空間Ｓ）を設けて構築された上側スラブ（例えば、後述の地下２階床スラブ１３、地下１階床スラブ２３）と、を備え、前記上側スラブに、流動化処理土を投入するための投入口（例えば、後述の投入口４０）および空気抜き孔（例えば、後述の空気抜き孔４１）を形成する工程（例えば、後述のステップＳ２、Ｓ４）と、前記投入口を通して前記下側スラブと前記上側スラブとの間に流動化処理土（例えば、後述の流動化処理土Ｍ）を複数回に分けて投入し、前記下側スラブと前記上側スラブとの間の内部空間に流動化処理土を充填する工程（例えば、後述のステップＳ３、Ｓ５）と、前記上側スラブの上に型枠材（例えば、後述の型枠材４２）を建て込んで、当該型枠材の内側にコンクリートを打設することで、新設建物の基礎を構築する工程（例えば、後述のステップＳ８）と、を備えることを特徴とする。 The method for constructing a foundation for a new building of the first invention is a method for constructing a foundation for a new building (e.g., foundation 1 for a new building, described below) on an existing structure (e.g., existing underground structure 2, described below), in which the existing structure comprises a lower slab (e.g., pressure-resistant plate 11, second basement floor slab 13, described below) and an upper slab (e.g., second basement floor slab 13, first basement floor slab 23, described below) constructed with an internal space (e.g., pit 14, internal space S, described below) on the lower slab, and an inlet (e.g., inlet 40, described below) for injecting liquefied treated soil and an air vent (e.g., The method includes a process of forming an air vent hole 41 in the lower slab (e.g., steps S2 and S4 described below), a process of pouring liquefied treated soil (e.g., liquefied treated soil M described below) in multiple batches between the lower slab and the upper slab through the inlet to fill the internal space between the lower slab and the upper slab with liquefied treated soil (e.g., steps S3 and S5 described below), and a process of erecting formwork material (e.g., formwork material 42 described below) on the upper slab and pouring concrete inside the formwork material to construct the foundation of a new building (e.g., step S8 described below).

この発明によれば、上側スラブに投入口および空気抜き孔を形成し、投入口を通して下側スラブと上側スラブとの間の内部空間に流動化処理土を充填したので、上側スラブや下側スラブを撤去しなくても、既存躯体の下側スラブ、上側スラブ、および流動化処理土が一体となって、新設地盤となる。よって、既存建物を解体した後に新設建物の基礎を構築する場合に、この既存躯体の一部を存置した状態で、その既存躯体内部のスラブで区切られた内部空間に流動化処理土を充填することで、既存躯体の解体範囲を最小限にできるから、新設建物の地盤を短工期で形成できる。 According to this invention, an inlet and air vent holes are formed in the upper slab, and liquefied treated soil is filled into the internal space between the lower and upper slabs through the inlet, so that the lower and upper slabs of the existing structure and the liquefied treated soil become one body and form the new ground without the need to remove the upper or lower slabs. Therefore, when constructing the foundation for a new building after demolishing an existing building, by filling the internal space separated by the slabs inside the existing structure with liquefied treated soil while leaving part of the existing structure in place, the extent of demolition of the existing structure can be minimized, and the ground for the new building can be formed in a short construction period.

第２の発明の新設建物の基礎の構築方法は、前記上側スラブに投入口および空気抜き孔を形成する工程の前に、前記下側スラブと周辺地盤（例えば、後述の周辺地盤３）との間に流動化処理土を充填する工程（例えば、後述のステップＳ１）をさらに備えることを特徴とする。 The second invention of the method for constructing the foundation of a new building is characterized in that it further includes a step (e.g., step S1 described below) of filling the space between the lower slab and the surrounding ground (e.g., surrounding ground 3 described below) with liquefied treated soil before the step of forming an inlet and an air vent in the upper slab.

この発明によれば、下側スラブと周辺地盤との間に流動化処理土を充填したので、流動化処理土を介して下側スラブと周辺地盤とを一体化でき、新設地盤がより強固となる。 According to this invention, the space between the lower slab and the surrounding ground is filled with liquefied treated soil, which allows the lower slab and the surrounding ground to be integrated through the liquefied treated soil, making the newly constructed ground stronger.

第３の発明の新設建物の基礎構造は、既存躯体（例えば、後述の既存地下躯体２）の上に構築される新設建物の基礎（例えば、後述の新設建物の基礎１）の構造であって、前記既存躯体は、下側スラブ（例えば、後述の耐圧盤１１、地下２階床スラブ１３）と、当該下側スラブの上に内部空間（例えば、後述のピット１４、内部空間Ｓ）を設けて構築された上側スラブ（例えば、後述の地下２階床スラブ１３、地下１階床スラブ２３）と、を備え、前記下側スラブと前記上側スラブとの間の内部空間には、流動化処理土（例えば、後述の流動化処理土Ｍ）が充填されることを特徴とする。 The foundation structure of a new building of the third invention is a structure of a foundation of a new building (e.g., foundation 1 of a new building described below) constructed on an existing structure (e.g., existing underground structure 2 described below), characterized in that the existing structure comprises a lower slab (e.g., pressure-resistant plate 11, second basement floor slab 13 described below) and an upper slab (e.g., second basement floor slab 13, first basement floor slab 23 described below) constructed with an internal space (e.g., pit 14, internal space S described below) on the lower slab, and the internal space between the lower slab and the upper slab is filled with liquefied treated soil (e.g., liquefied treated soil M described below).

この発明によれば、既存躯体の下側スラブと上側スラブとで区切られた内部空間に流動化処理土を充填したので、上側スラブや下側スラブを撤去しなくても、既存躯体の下側スラブ、上側スラブ、および流動化処理土が一体となって、新設地盤となる。よって、既存建物を解体した後に新設建物の基礎を構築する場合に、この既存躯体の一部を存置した状態で、その既存躯体内部のスラブで区切られた内部空間に流動化処理土を充填することで、既存躯体の解体範囲を最小限にできるから、新設建物の地盤を短工期で形成できる。 According to this invention, the internal space separated by the lower and upper slabs of the existing structure is filled with liquefied treated soil, so the lower and upper slabs of the existing structure and the liquefied treated soil become one body and form the new ground without the need to remove the upper or lower slabs. Therefore, when constructing the foundation for a new building after demolishing an existing building, by filling the internal space separated by the slabs inside the existing structure with liquefied treated soil while leaving part of the existing structure in place, the extent of demolition of the existing structure can be minimized, and the ground for the new building can be formed in a short construction period.

本発明によれば、既存建物を解体した後に新設建物の基礎を構築する際に、新設建物の地盤を短工期で形成できる、新設建物の基礎の構築方法を提供できる。 The present invention provides a method for constructing a foundation for a new building that can form the foundation for the new building in a short construction period when constructing the foundation for the new building after demolishing an existing building.

本発明の一実施形態に係る新設建物の基礎が構築される既存地下躯体の縦断面図である。1 is a vertical cross-sectional view of an existing underground structure on which the foundation of a new building in accordance with one embodiment of the present invention is constructed. 実施形態に係る新設建物の基礎の縦断面図である。FIG. 2 is a vertical cross-sectional view of the foundation of a newly constructed building according to an embodiment of the present invention. 実施形態に係る流動化処理土の使用材料を示す図である。FIG. 2 is a diagram showing materials used in the liquefied treated soil according to the embodiment. 実施形態に係る新設建物の基礎の構築手順のフローチャートである。1 is a flowchart of a procedure for constructing a foundation for a new building according to an embodiment. 実施形態に係る新設建物の基礎の構築手順の説明図（その１：既存建物を解体した状態を示す図）である。FIG. 1 is an explanatory diagram of the construction procedure for the foundation of a new building according to an embodiment (part 1: a diagram showing the state after the existing building has been demolished). 実施形態に係る新設建物の基礎の構築手順の説明図（その２：地下２階床スラブの投入口および空気抜き孔の配置を示す図）である。FIG. 2 is an explanatory diagram of the construction procedure for the foundation of a new building according to an embodiment (part 2: a diagram showing the arrangement of the input port and air vent holes of the second basement floor slab). 実施形態に係る新設建物の基礎の構築手順の説明図（その３：ピット内に流動化処理土を投入した状態を示す図）である。This is an explanatory diagram of the construction procedure for the foundation of a new building according to the embodiment (Part 3: A diagram showing the state in which liquefied treated soil has been poured into the pit). 実施形態に係る新設建物の基礎の構築手順の説明図（その４：地下２階部分に流動化処理土を投入した状態を示す図）である。This is an explanatory diagram of the construction procedure for the foundation of a new building according to the embodiment (Part 4: A diagram showing the state in which liquefied treated soil has been poured into the second basement floor). 実施形態に係る新設建物の基礎の構築手順の説明図（その４：新設建物の基礎を構築した状態を示す図）である。FIG. 4 is an explanatory diagram of the procedure for constructing the foundation of a new building according to the embodiment (part 4: diagram showing the state after the foundation of the new building has been constructed).

以下、本発明の一実施形態について、図面を参照しながら説明する。
図１は、本発明の一実施形態に係る新設建物の基礎１が構築される既存地下躯体２の縦断面図である。
新設建物の基礎１は、既存躯体としての既存地下躯体２の上に構築される。
既存地下躯体２は、基礎１０と、基礎１０の上に設けられた地下２階躯体２０と、地下２階躯体２０の上に設けられた地下１階躯体３０と、を備える。
基礎１０は、耐圧盤１１、基礎梁１２、および、地下２階床スラブ１３を備えている。耐圧盤１１、基礎梁１２、地下２階床スラブ１３で囲まれた空間は、ピット１４となっており、これにより、基礎１０には、複数のピット１４が設けられている。つまり、各ピット１４において、下側スラブとしての耐圧盤１１と上側スラブとしての地下２階床スラブ１３との間は、内部空間Ｓとなっている。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical cross-sectional view of an existing underground structure 2 on which a foundation 1 for a new building according to one embodiment of the present invention is constructed.
The foundation 1 of the new building is constructed on the existing underground structure 2 as the existing structure.
The existing underground structure 2 comprises a foundation 10, a second-floor underground structure 20 built on the foundation 10, and a first-floor underground structure 30 built on the second-floor underground structure 20.
The foundation 10 includes a pressure-resistant plate 11, foundation beams 12, and a second basement floor slab 13. The space surrounded by the pressure-resistant plate 11, foundation beams 12, and second basement floor slab 13 is a pit 14, and thus a plurality of pits 14 are provided in the foundation 10. In other words, in each pit 14, an internal space S is formed between the pressure-resistant plate 11 as the lower slab and the second basement floor slab 13 as the upper slab.

地下２階躯体２０は、地下外壁２１、地下１階床梁２２、および地下１階床スラブ２３を備えている。下側スラブとしての地下２階床スラブ１３と上側スラブとしての地下１階床スラブ２３との間には、内部空間Ｓが設けられている。地下１階躯体３０は、地下外壁３１、１階床梁３２、および１階床スラブ３３を備えている。 The second basement floor structure 20 includes a basement exterior wall 21, a first basement floor beam 22, and a first basement floor slab 23. An internal space S is provided between the second basement floor slab 13 as the lower slab and the first basement floor slab 23 as the upper slab. The first basement floor structure 30 includes a basement exterior wall 31, a first floor floor beam 32, and a first floor floor slab 33.

図２は、新設建物の基礎１の縦断面図である。
既存地下躯体２の各ピット１４（内部空間Ｓ）には、流動化処理土Ｍが充填されている。また、地下２階床スラブ１３と地下１階床スラブ２３との間の内部空間Ｓにも、流動化処理土Ｍが充填されている。これにより、既存地下躯体２と流動化処理土Ｍとが一体となって、新設地盤となっている。また、地下１階躯体３０は、地下外壁３１を残して撤去されており、新設建物の基礎１は、新設地盤の地下１階床スラブ２３の上面に構築されている。 FIG. 2 is a vertical cross-sectional view of the foundation 1 of a new building.
Each pit 14 (internal space S) of the existing underground structure 2 is filled with liquefied treated soil M. The internal space S between the second basement floor slab 13 and the first basement floor slab 23 is also filled with liquefied treated soil M. As a result, the existing underground structure 2 and the liquefied treated soil M are integrated to form the new construction ground. The first basement floor structure 30 has been removed leaving only the underground outer wall 31, and the foundation 1 of the new building is constructed on the upper surface of the first basement floor slab 23 of the new construction ground.

流動化処理土Ｍは、例えば、図３に示す材料を用いて作製する。具体的には、建設発生土に水を加えて泥水を作製し、この泥水にセメント系固化材および密度調整材を添加することで、流動化処理土Ｍを作製する。このとき、泥水および流動化処理土Ｍについて、濃度を調整しながら比重を管理する。この流動化処理土Ｍの品質基準は、以下のようになる。
フロー値 ：１１０ｍｍ以上
ブリージング率：１．０％未満
密度 ：１．６０ｔ／ｍ３以上
一軸圧縮強さ ：設計基準強度以上 Ｆｃ＝９００ｋＮ／ｃｍ２ The liquefied treated soil M is prepared, for example, using the materials shown in Fig. 3. Specifically, water is added to construction waste soil to prepare muddy water, and a cement-based solidification material and density adjusting material are added to this muddy water to prepare the liquefied treated soil M. At this time, the specific gravity of the muddy water and the liquefied treated soil M is controlled while adjusting the concentration. The quality standards for this liquefied treated soil M are as follows:
Flow value: 110 mm or more Breathing rate: less than 1.0% Density: 1.60 t/ m3 or more Unconfined compressive strength: design standard strength or more Fc = 900 kN/ cm2

以下、既存地下躯体２の上に新設建物の基礎１を構築する手順について、図４のフローチャートを参照しながら説明する。
ステップＳ１では、図５に示すように、既存建物の地上躯体を解体して撤去する。また、既存地下躯体２と周辺地盤３との間に隙間（内部空間）がある場合には、流動化処理土Ｍを充填する。
ステップＳ２では、図５に示すように、各ピット１４の上側スラブである地下２階床スラブ１３に、人通孔１５、流動化処理土Ｍを投入するための投入口４０、および空気抜き孔４１を形成する。具体的には、図６に示すように、ピット１４の中央部に人通孔１５を設け、この人通孔１５の周囲の４箇所に投入口４０を形成し、さらに、ピット１４の四隅に空気抜き孔４１を形成する。 The procedure for constructing the foundation 1 of a new building on the existing underground structure 2 will be described below with reference to the flow chart of FIG.
In step S1, the above-ground structure of the existing building is dismantled and removed, as shown in Fig. 5. If there is a gap (internal space) between the existing underground structure 2 and the surrounding ground 3, it is filled with liquefied treated soil M.
In step S2, as shown in Fig. 5, a manhole 15, an inlet 40 for introducing liquefied treated soil M, and an air vent hole 41 are formed in the second basement floor slab 13, which is the upper slab of each pit 14. Specifically, as shown in Fig. 6, the manhole 15 is provided in the center of the pit 14, and inlets 40 are formed in four places around the manhole 15. Furthermore, air vent holes 41 are formed in the four corners of the pit 14.

ステップＳ３では、図７に示すように、投入口４０を通して各ピット１４に流動化処理土Ｍを投入する。具体的には、各ピット１４の耐圧盤１１と地下２階床スラブ１３との間に、複数回に分けて流動化処理土Ｍを投入し、各ピット１４内に流動化処理土Ｍを充填する。この流動化処理土Ｍの投入は、投入口４０および空気抜き孔４１から流動化処理土Ｍが溢れるまで行う。なお、図７中の破線は、一回で投入する流動化処理土Ｍの上端面の高さ位置を示す。
ステップＳ４では、図８に示すように、上側スラブである地下１階床スラブ２３に、流動化処理土Ｍを投入するための投入口４０を形成する。具体的には、例えば、地下１階床スラブ２３の１スパンにつき、投入口４０を１つ形成する。なお、地下１階床スラブ２３には、図示しない階段や設備スペースなどの開口があるため、これらの開口を空気抜き孔として用いる。 In step S3, as shown in Fig. 7, liquefied treated soil M is poured into each pit 14 through the pouring inlet 40. Specifically, the liquefied treated soil M is poured in multiple batches between the pressure plate 11 of each pit 14 and the second basement floor slab 13, filling each pit 14 with the liquefied treated soil M. The pouring of the liquefied treated soil M is continued until it overflows from the pouring inlet 40 and the air vent hole 41. The dashed line in Fig. 7 indicates the height position of the upper end surface of the liquefied treated soil M poured in one batch.
In step S4, as shown in Fig. 8, an inlet 40 for injecting the liquefied treated soil M is formed in the first basement floor slab 23, which is the upper slab. Specifically, for example, one inlet 40 is formed for each span of the first basement floor slab 23. Note that, since the first basement floor slab 23 has openings for stairs, equipment spaces, etc. (not shown), these openings are used as air vents.

ステップＳ５では、図８に示すように、投入口４０を通して地下２階部分に流動化処理土Ｍを投入する。具体的には、投入口４０を通して地下２階躯体２０の地下２階床スラブ１３と地下１階床スラブ２３との間に、高さ１ｍ毎に複数回に分けて流動化処理土Ｍを投入し、地下２階躯体２０内の内部空間Ｓに流動化処理土Ｍを充填する。この流動化処理土Ｍの投入は、投入口４０および空気抜き孔から流動化処理土Ｍが溢れるまで行う。なお、図８中の破線は、一回で投入する流動化処理土Ｍの上端面の高さ位置を示す。
ステップＳ６では、図９に示すように、地下１階部分に流動化処理土Ｍを投入する。具体的には、地下２階躯体２０の地下１階床スラブ２３の上に、高さ１ｍ毎に複数回に分けて流動化処理土Ｍを投入する。なお、図９中の破線は、一回で投入する流動化処理土Ｍの上端面の高さ位置を示す。また、図示しないが、この投入した流動化処理土Ｍの上に、墨出し用のコンクリート（ｔ＝１００ｍｍ程度）を打設する。
ステップＳ７では、図９に示すように、１階床躯体（１階床梁３２および１階床スラブ３３）を解体する。
ステップＳ８では、図９に示すように、地下２階躯体２０の上に新設建物の基礎１を構築する。具体的には、ステップＳ６で投入した流動化処理土Ｍの上に型枠材４２を建て込んで、この型枠材４２の内側にコンクリートを打設することで、新設建物の基礎１を構築する。 In step S5, as shown in Fig. 8, liquefied treated soil M is poured into the second basement floor portion through the pouring inlet 40. Specifically, the liquefied treated soil M is poured into the space between the second basement floor slab 13 and the first basement floor slab 23 of the second basement floor structure 20 through the pouring inlet 40 in multiple batches at a height of 1 m each, filling the internal space S in the second basement floor structure 20. The pouring of the liquefied treated soil M is continued until it overflows from the pouring inlet 40 and the air vent holes. The dashed line in Fig. 8 indicates the height position of the upper end surface of the liquefied treated soil M poured in one batch.
In step S6, as shown in Fig. 9, liquefied treated soil M is poured into the first basement floor portion. Specifically, the liquefied treated soil M is poured in multiple batches at heights of 1 m each onto the first basement floor slab 23 of the second basement floor structure 20. The dashed lines in Fig. 9 indicate the height position of the upper end surface of the liquefied treated soil M poured in one batch. In addition, although not shown, concrete (t = about 100 mm) for marking is poured on top of the poured liquefied treated soil M.
In step S7, as shown in FIG. 9, the first floor floor framework (first floor floor beams 32 and first floor floor slab 33) is dismantled.
In step S8, as shown in Fig. 9, the foundation 1 of the new building is constructed on the second basement floor structure 20. Specifically, formwork materials 42 are erected on the liquefied treated soil M poured in step S6, and concrete is poured inside the formwork materials 42, thereby constructing the foundation 1 of the new building.

なお、上述のステップＳ２、Ｓ４において、例えば、投入口４０は、φ３００ｍｍのコア抜きにより形成し、空気抜き孔４１は、φ１００ｍｍのコア抜きにより形成する。
また、ステップＳ３、Ｓ５、Ｓ６において、流動化処理土Ｍの投入前に、投入箇所に水が溜まっている場合には、この溜まっている水を水中ポンプなどで除去する。また、流動化処理土Ｍの投入時に、投入口４０からバイブレータを挿入して流動化処理土Ｍに振動を加えて、投入した流動化処理土Ｍの表面が極力水平となるようにする。
また、流動化処理土Ｍについては、充填する前に、１配合ごとに１回フロー値と比重を測定し、上述の流動化処理土の品質基準を満足しているか否かの合否判定を行い、合格したものを充填した。ブリージング率については、１配合ごとに３本の試験体を採取し、試験体採取２４時間後に、各試験体の平均値が品質基準値以上であることを確認した。また、一軸圧縮強さについては、１配合ごとに３本の試験体を採取し、試験体作成後２８日後に、各試験体の平均値が品質基準値以上であることを確認した。
また、上側スラブ１３、２３に接する流動化処理土Ｍ（つまり最上層の流動化処理土Ｍ）については、充填後の流動化処理土Ｍの沈下を防止する目的で、充填済みの下層の流動化処理土Ｍと比べて、セメント系固化材を図３に示す配合量３.０５ｇ／ｃｍ３を上回る配合とした。また、流動化処理土Ｍを使用した新設建物の基礎の品質管理として、下側スラブと上側スラブとの間に流動化処理土Ｍを充填した後、投入口４０、人通孔１５、および空気抜き孔４１（図６参照）の他に、新たな貫通孔を上側スラブに設けて、この新たな貫通孔を通して下側スラブと流動化処理土Ｍとの間に隙間が発生していないことを目視で再確認した。 In the above steps S2 and S4, for example, the input port 40 is formed by punching a core having a diameter of 300 mm, and the air vent hole 41 is formed by punching a core having a diameter of 100 mm.
Furthermore, in steps S3, S5, and S6, if water has accumulated at the point where the liquefied treated soil M is poured before the soil is poured, the accumulated water is removed using a submersible pump, etc. Furthermore, when pouring the liquefied treated soil M, a vibrator is inserted from the pouring inlet 40 to vibrate the liquefied treated soil M so that the surface of the poured liquefied treated soil M is as horizontal as possible.
In addition, for the liquefied treated soil M, the flow value and specific gravity were measured once for each mix before filling, and a pass/fail judgment was made as to whether or not the quality standards for the liquefied treated soil were met, and those that passed were filled. For the bleeding rate, three test specimens were taken for each mix, and it was confirmed that the average value of each test specimen was equal to or greater than the quality standard value 24 hours after the test specimens were taken. For the unconfined compressive strength, three test specimens were taken for each mix, and it was confirmed that the average value of each test specimen was equal to or greater than the quality standard value 28 days after the test specimens were made.
In addition, for the fluidized treated soil M in contact with the upper slabs 13, 23 (i.e., the top layer of the fluidized treated soil M), the cement-based solidification material was mixed at a higher ratio than the mixed amount of 3.05 g/ cm3 shown in Figure 3, compared to the fluidized treated soil M in the lower layers that had already been filled, in order to prevent the fluidized treated soil M from settling after filling. In addition, as quality control for the foundations of new buildings using fluidized treated soil M, after filling the space between the lower and upper slabs with fluidized treated soil M, a new through-hole was made in the upper slab in addition to the inlet 40, manhole 15, and air vent 41 (see Figure 6), and it was visually reconfirmed through this new through-hole that no gaps had occurred between the lower slab and the fluidized treated soil M.

本実施形態によれば、以下のような効果がある。
（１）既存地下躯体２の耐圧盤１１と地下２階床スラブ１３との内部空間Ｓ、および、地下２階床スラブ１３と地下１階床スラブ２３との内部空間Ｓに流動化処理土Ｍを充填した。よって、既存地下躯体２を全て撤去しなくても、既存地下躯体２と流動化処理土Ｍとが一体となって、新設地盤となる。よって、既存建物を解体した後に新設建物の基礎１を構築する場合に、新設建物の地盤を短工期で形成できる。
（２）ステップＳ１において、既存地下躯体２と周辺地盤３との間に流動化処理土Ｍを充填したので、流動化処理土Ｍを介して既存地下躯体２と周辺地盤３とを一体化でき、新設地盤がより強固となる。 According to this embodiment, the following effects are obtained.
(1) The internal space S between the pressure plate 11 of the existing underground structure 2 and the second basement floor slab 13, and the internal space S between the second basement floor slab 13 and the first basement floor slab 23 are filled with liquefied treated soil M. Thus, even if the entire existing underground structure 2 is not removed, the existing underground structure 2 and the liquefied treated soil M are integrated to form the new ground. Therefore, when constructing the foundation 1 of a new building after demolishing the existing building, the ground for the new building can be formed in a short construction period.
(2) In step S1, liquefied treated soil M is filled between the existing underground structure 2 and the surrounding ground 3, so that the existing underground structure 2 and the surrounding ground 3 can be integrated through the liquefied treated soil M, making the new ground stronger.

なお、本発明は前記実施形態に限定されるものではなく、本発明の目的を達成できる範囲での変形、改良等は本発明に含まれるものである。
また、上述の実施形態では、上側スラブに接する最上層の流動化処理土についてのみ、下層の流動化処理土と異なり、セメント系固化材を図３に示す配合量よりも増量したが、これに限らず、全ての層について、セメント系固化材を図３に示す配合量よりも増量してもよい。 The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention.
In addition, in the above-described embodiment, only in the top layer of liquefied treated soil in contact with the upper slab, the amount of cement-based solidification material is increased from the mixing amount shown in Figure 3, unlike the liquefied treated soil in the lower layers. However, this is not limited to the above, and the amount of cement-based solidification material may be increased from the mixing amount shown in Figure 3 for all layers.

１…新設建物の基礎 ２…既存地下躯体（既存躯体） ３…周辺地盤
１０…基礎 １１…耐圧盤（下側スラブ） １２…基礎梁
１３…地下２階床スラブ（上側スラブ、下側スラブ） １４…ピット １５…人通孔
２０…地下２階躯体 ２１…地下外壁 ２２…地下１階床梁
２３…地下１階床スラブ（上側スラブ）
３０…地下１階躯体 ３１…地下外壁 ３２…１階床梁 ３３…１階床スラブ
４０…投入口 ４１…空気抜き孔 ４２…型枠材
Ｍ…流動化処理土 Ｓ…内部空間 1... Foundation of new building 2... Existing underground structure (existing structure) 3... Surrounding ground 10... Foundation 11... Pressure plate (lower slab) 12... Foundation beam 13... Second basement floor slab (upper slab, lower slab) 14... Pit 15... Manhole 20... Second basement floor structure 21... Basement exterior wall 22... First basement floor beam 23... First basement floor slab (upper slab)
30...1st basement floor structure 31...Basement exterior wall 32...1st floor floor beam 33...1st floor floor slab 40...Inlet 41...Air vent 42...Formwork material M...Liquidized treated soil S...Inner space

Claims (2)

既存躯体の上に新設建物の基礎を構築する方法であって、
前記既存躯体は、下側スラブと、当該下側スラブの上に内部空間を設けて構築された上側スラブと、を備え、
前記上側スラブに、流動化処理土を投入するための投入口および空気抜き孔を形成する工程と、
前記投入口を通して前記下側スラブと前記上側スラブとの間に流動化処理土を約１ｍ毎に複数回に分けて投入し、前記下側スラブと前記上側スラブとの間の内部空間に流動化処理土を充填する工程と、
前記上側スラブの上に型枠材を建て込んで、当該型枠材の内側にコンクリートを打設することで、新設建物の基礎を構築する工程と、を備え、
前記流動化処理土は、建設発生土に水を加えて泥水を作成し、前記泥水にセメント系固化材および密度調整材を添加して作製され、
前記流動化処理土を充填する工程では、フロー値が１１０ｍｍ以上、ブリージング率が１．０％未満、密度が１．６０ｔ／ｍ ３ 以上、一軸圧縮強さが９００ｋＮ／ｃｍ ２ 以上を前記流動化処理土の品質基準として、１配合毎に前記品質基準を満たすか否かを判定して、前記品質基準を満たすものを充填するとともに、前記上側スラブに接する最上層の流動化処理土については、充填済みの下層の流動化処理土に比べて、セメント系固化材を増量することを特徴とする新設建物の基礎の構築方法。 A method for constructing a foundation for a new building on an existing structure, comprising the steps of:
The existing structure includes a lower slab and an upper slab constructed on the lower slab with an internal space provided thereon,
A step of forming an inlet for injecting liquefied treated soil and an air vent hole in the upper slab;
A step of injecting liquefied treated soil into the space between the lower slab and the upper slab through the inlet in multiple instalments at intervals of approximately 1 m , thereby filling the space between the lower slab and the upper slab with the liquefied treated soil;
and a step of constructing a foundation for a new building by erecting formwork materials on the upper slab and pouring concrete inside the formwork materials .
The liquefied soil is prepared by adding water to construction waste soil to produce muddy water, and then adding a cement-based solidification material and a density adjusting material to the muddy water.
In the process of filling the liquefied treated soil, the quality standards for the liquefied treated soil are a flow value of 110 mm or more, a bleeding rate of less than 1.0%, a density of 1.60 t/m3 or more, and a uniaxial compressive strength of 900 kN/cm2 or more, and each mix is judged to see if it meets these quality standards, and only those that meet the quality standards are filled, and the amount of cement-based solidification material is increased for the top layer of liquefied treated soil in contact with the upper slab compared to the liquefied treated soil in the lower layers that have already been filled.This is a method for constructing the foundation of a newly constructed building, characterized in that 前記上側スラブに投入口および空気抜き孔を形成する工程の前に、前記下側スラブと周辺地盤との間に流動化処理土を充填する工程をさらに備えることを特徴とする請求項１に記載の新設建物の基礎の構築方法。 The method for constructing a foundation for a new building according to claim 1, further comprising the step of filling the space between the lower slab and the surrounding ground with liquefied treated soil before the step of forming an inlet and an air vent in the upper slab.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003147782A (en) 2001-11-09 2003-05-21 Tenox Corp Foundation structure for constructing new building on existing basement and its construction method
JP2007170070A (en) 2005-12-22 2007-07-05 Takenaka Komuten Co Ltd Method for rebuilding building
JP2015034436A (en) 2013-08-09 2015-02-19 株式会社竹中工務店 Rebuilding method for new building, and new building
JP2015161125A (en) 2014-02-27 2015-09-07 大成建設株式会社 Plumbing adjustment method and building

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003147782A (en) 2001-11-09 2003-05-21 Tenox Corp Foundation structure for constructing new building on existing basement and its construction method
JP2007170070A (en) 2005-12-22 2007-07-05 Takenaka Komuten Co Ltd Method for rebuilding building
JP2015034436A (en) 2013-08-09 2015-02-19 株式会社竹中工務店 Rebuilding method for new building, and new building
JP2015161125A (en) 2014-02-27 2015-09-07 大成建設株式会社 Plumbing adjustment method and building

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