JP4189078B2 - Construction method of underground structure in liquefied ground - Google Patents

Construction method of underground structure in liquefied ground Download PDF

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Publication number
JP4189078B2
JP4189078B2 JP10798199A JP10798199A JP4189078B2 JP 4189078 B2 JP4189078 B2 JP 4189078B2 JP 10798199 A JP10798199 A JP 10798199A JP 10798199 A JP10798199 A JP 10798199A JP 4189078 B2 JP4189078 B2 JP 4189078B2
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Prior art keywords
ground
underground structure
liquefied
improved
retaining walls
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Expired - Lifetime
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JP10798199A
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Japanese (ja)
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JP2000297441A (en
Inventor
増雄 船引
岳郎 西嶋
昭彦 石黒
正哉 三原
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株式会社間組
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【0001】
【発明の属する技術分野】
本発明は、液状化する可能性のある地盤において地下構造物を構築する方法、及び基礎構造に関する。
【0002】
【従来の技術】
液状化する可能性のある地盤、すなわち砂やシラス等を多く含む地盤では、地震時の振動や衝撃によって間隙水に高い圧力が発生し、それにつれて地盤の有効応力が減少して液状化し、この液状化した土砂が所定方向に振動して地下構造物には動液圧が作用する。このような動液圧に対しては、例えば、締固め工法又は固結工法によって地下構造物下方の地盤を改良するか、あるいは、地下構造物下方の地盤に杭基礎を形成することが提案されている。
【0003】
ここで、締固め工法とは、地盤改良箇所に粗砂などを圧入して砂状柱を構築し、この砂状柱の周辺地盤を締め固める工法である。また固結工法としては、深層混合処理工法やセメント注入工法があり、これは、地盤改良箇所に液状セメント等の安定材を圧入し攪拌翼で混合して強度を有するパイルを造成したり、液状セメントを圧入し地盤を固化するものである。
【0004】
【発明が解決しようとする課題】
上記従来の締固め工法は、地下構造物直下の地盤のみならず、主働崩壊角以内の広範囲にわたって地盤改良を行う必要があるものの、施工環境によっては広範囲の地盤改良が不可能な場合がある。また従来の固結工法は、改良体の安定を図るために大きな改良体を形成する必要があり、締固め工法と比較して数倍の施工コストが掛かる。さらに、従来の杭基礎において、水平方向の耐力を向上させるためには、大径で剛性の高い杭を高密度で打設する必要があり、やはり締固め工法と比較すると数倍の施工コストが掛かる。
【0005】
本発明は上記従来技術の欠点に着目し、これを解決せんとしたものであり、その課題は、施工コストの安い締固め工法により地下構造物直下を地盤改良するだけで、液状化による動液圧に対抗することができる地下構造物の基礎構造及び構築方法を提供することにある。
【0006】
【課題を解決するための手段】
上記課題を解決するために、本発明では、液状化する可能性のある地盤において地下構造物を構築する方法であって、構築予定の地下構造物の底版範囲における地盤の所定深さから下方の非液状化層の少なくとも上面までの区間を締固めて地盤改良する工程と、前記地盤改良工程の後に前記底版範囲の対向する両面で前記非液状化層に貫入するまで山止め壁を鋼矢板、鋼管矢板又は軽量鋼矢板から形成する工程と、改良された地盤まで前記山止め壁間を掘削する工程と、前記改良された地盤上において両側壁が山止め壁に当接して定着具により固定されるように地下構造物を構築する工程とを含む地下構造物の構築方法を提供する。
【0007】
本発明の地下構造物の構築方法において、地盤の締固め工程は、従来の締固め工法と同じものであって、地盤改良箇所に粗砂などを圧入して砂状柱を構築し、この砂状柱の周辺地盤を締め固める工法である。
【0009】
前記改良地盤の上には、表面の凹凸を平らにするために、コンクリートやモルタル等の均し材を敷設して、この均し材の上に前記地下構造物を載置しても良い。
【0010】
【実施例】
以下、添付図面に基づいて実施例を説明するが、本発明はこれに限定されるものではない。図1は液状化地盤30における基礎構造10の一実施例を示す断面図であり、この基礎構造10は、非液状化層15の表面から所定高さHまで地盤改良されてなる改良地盤14と、この改良地盤14の両側に打設された山止め壁11a,11bと、この山止め壁11a,11b間における改良地盤14上に敷き均されたコンクリート層13と、このコンクリート層13の上に構築された地下構造物としてのピット又はカルバート12とを含む。
【0011】
ここで、前記カルバート12は、電気ケーブル等を通すための電気洞道、発電所の取放水路、あるいは道路等に用いられるものであり、したがって、基礎構造10は所定幅で所定の距離にわたり延長するものである。また前記カルバート12は、両側壁12a,12bの少なくとも下端、好ましくは上下方向の全長が山止め壁11a,11bに当接するように形成され、図2に示したように、ジベル等の定着具17により山止め壁11a,11bとの定着が補強されている。また前記改良地盤14は、地盤改良範囲(改良幅W、改良深さH)に粗砂などを圧入して砂状柱14aを構築し、この砂状柱14aの周辺地盤を締め固めて形成したものである。さらに前記山止め壁11a,11bは、下端11a',11b'が非液状化層15に根入れされ、少なくとも上端がカルバート12の側壁12a,12bに当接する高さまで延ばされている。
【0012】
図3は山止め壁11a,11bの外側の地盤が液状化して、同じ方向に向かう動液圧21a,21bが生じた場合に、山止め壁11a,11bに生じる変形を簡略に示した概念図である。ここで、山止め壁11aは動液圧21aを受けると、点線20aで示したように矢印R方向に曲がり、改良地盤14に圧縮力を伝達する。一方、山止め壁11bは動液圧21bを受けると、点線20bで示したように、カルバート12の上方部分が矢印R方向に曲がり、山止め壁20bの下方部分が矢印L方向に曲がり、改良地盤14には圧縮力が伝達される。つまり、山止め壁11a,11bがカルバート12に当接するように配置されて固定されたので、これらカルバート12と山止め壁11a,11bとは一体化された構造物としての変形特性を示し、カルバート12の下方地盤には引張力は作用せず、圧縮力のみが作用する。したがって、この部分の地盤改良が締固め工法による簡略なものであっても、また山止め壁が、例えば一枚物の鋼矢板を連設してなる簡略なものであっても、これら締固めによる改良地盤14と山止め壁11a,11bとの相互作用により、液状化の際の動液圧21a,21bに対抗することが可能になった。
【0013】
次に、液状化地盤における地下構造物の構築方法について説明する。最初に、地盤の非液状化層15の上面から高さHまでを締め固めて改良し、改良地盤14を形成する。なお、この地盤改良は複数の砂状柱14aを用いた従来工法により行い、さらに、改良幅Wは構築する地下構造物としてのカルバート12の底版12cの幅に合わせて定める。次に、改良幅Wの両側で非液状化層15に貫入するまで山止め壁11a,11bを構築し、この山止め壁11a,11b間に腹起しや切梁(図示せず)を設けながら改良地盤14に達するまで掘削する。所定深さまで掘削した後、掘削底面にコンクリートを平らに敷き均して、コンクリート層13を形成する。そして、コンクリート層13が硬化したら、山止め壁11a,11b間にはカルバート12を構築する。なお、山止め壁11a,11bの表面には予めジベル等の定着具17を固定しておき、カルバート12は、この定着具17を側壁12a,12bに埋設するように形成する。
【0014】
【発明の効果】
本発明では、地下構造物と山止め壁とが当接して一体化され、地下構造物直下の地盤が両側から山止め壁で囲まれているので、山止め壁の両側に同じ方向の動液圧が作用した場合であっても、地下構造物直下の山止め壁で囲まれた箇所には引張力が作用せず、圧縮応力のみが作用し、これにより、地盤改良部分は締固め工法等の簡略な工法で形成し、且つ比較的軽量な山止め壁で囲んでも、充分な抵抗力を持つ基礎を構築することが可能になった。
【図面の簡単な説明】
【図1】発明の基礎構造の一実施例を示した断面図である。
【図2】図1の基礎構造を部分的に拡大して示した断面図である。
【図3】図1の基礎構造における矢板の変形状態を簡略に示した図である。
【符号の説明】
11a,11b 山止め壁
12 カルバート(地下構造物)
12c 底版
14 改良地盤
15 非液状化層
W 底版範囲
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for constructing an underground structure in a ground that may be liquefied, and a foundation structure.
[0002]
[Prior art]
In the ground that may be liquefied, that is, the ground that contains a lot of sand, shirasu, etc., high pressure is generated in the pore water due to the vibration and impact at the time of the earthquake, and the effective stress of the ground decreases accordingly and liquefies. The liquefied earth and sand vibrate in a predetermined direction, and hydrodynamic pressure acts on the underground structure. For such hydrodynamic pressure, it is proposed to improve the ground below the underground structure by, for example, compaction method or consolidation method, or to form a pile foundation on the ground below the underground structure. ing.
[0003]
Here, the compacting method is a method of constructing sandy pillars by pressing coarse sand or the like into the ground improvement place and compacting the surrounding ground of the sandy pillars. In addition, the consolidation method includes a deep mixing method and a cement injection method, in which a stabilizer such as liquid cement is pressed into the ground improvement site and mixed with a stirring blade to form a pile having strength, Cement is injected to solidify the ground.
[0004]
[Problems to be solved by the invention]
Although the above conventional compaction method needs to improve the ground not only under the underground structure but also over a wide range within the main collapse angle, it may not be possible to improve the ground over a wide range depending on the construction environment. . Moreover, the conventional caking method needs to form a large improved body in order to stabilize the improved body, and requires several times the construction cost as compared with the compacting method. Furthermore, in order to improve the horizontal bearing strength in conventional pile foundations, it is necessary to drive high-diameter, high-rigidity piles at a high density, which is several times more expensive than the compaction method. It takes.
[0005]
The present invention focuses on the drawbacks of the prior art described above, and is intended to solve this problem. The problem is that the hydraulic fluid by liquefaction can be improved by simply improving the ground directly under the underground structure by a compacting method with a low construction cost. An object of the present invention is to provide a foundation structure and a construction method for an underground structure that can resist pressure.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is a method for constructing an underground structure in a ground that may be liquefied, and is below a predetermined depth of the ground in the bottom plate range of the underground structure to be constructed a step of ground improvement the section up to at least the upper surface of the non-liquefied layer compacting, the steel Yamadome wall to penetrate into the non-liquid layer on both sides face to face of the bottom plate range after the soil improvement process sheet piles, forming a steel pipe sheet piles or lightweight steel sheet piles, a step of excavating the Yamadome walls to ground improved, the side walls on the improved ground is by contact with the fixing member to Yamadome wall A method for constructing an underground structure including the step of constructing the underground structure to be fixed.
[0007]
In the underground structure construction method of the present invention, the ground compaction process is the same as the conventional compaction method, and a sand-like column is constructed by pressing coarse sand or the like into the ground improvement location. This is a method of compacting the ground around the column.
[0009]
On the improved ground, a leveling material such as concrete or mortar may be laid to flatten the surface irregularities, and the underground structure may be placed on the leveling material.
[0010]
【Example】
Hereinafter, although an example is described based on an accompanying drawing, the present invention is not limited to this. FIG. 1 is a cross-sectional view showing an embodiment of a foundation structure 10 in a liquefied ground 30. The mountain retaining walls 11 a and 11 b placed on both sides of the improved ground 14, the concrete layer 13 spread on the improved ground 14 between the mountain retaining walls 11 a and 11 b, and the concrete layer 13 It includes a pit or culvert 12 as a built underground structure.
[0011]
Here, the culvert 12 is used for an electric cave for passing an electric cable or the like, an intake / discharge channel of a power plant, a road or the like. Therefore, the foundation structure 10 is extended over a predetermined distance with a predetermined width. To do. The culvert 12 is formed such that at least the lower ends of both side walls 12a and 12b, preferably the entire length in the vertical direction, abuts against the mountain retaining walls 11a and 11b. As shown in FIG. This reinforces fixing with the mountain retaining walls 11a and 11b. Further, the improved ground 14 is formed by pressing sand into the ground improvement range (improvement width W, improvement depth H) to construct a sand column 14a, and compacting the surrounding ground of the sand column 14a. Is. Further, the mountain retaining walls 11 a and 11 b have lower ends 11 a ′ and 11 b ′ embedded in the non-liquefaction layer 15, and at least the upper ends are extended to a height at which they abut against the side walls 12 a and 12 b of the culvert 12.
[0012]
FIG. 3 is a conceptual diagram simply showing the deformation that occurs in the retaining walls 11a and 11b when the ground outside the retaining walls 11a and 11b is liquefied and dynamic fluid pressures 21a and 21b are generated in the same direction. It is. Here, when receiving the hydraulic fluid pressure 21 a, the mountain retaining wall 11 a bends in the direction of arrow R as indicated by the dotted line 20 a and transmits the compressive force to the improved ground 14. On the other hand, when the mountain retaining wall 11b receives the hydrodynamic pressure 21b, the upper part of the culvert 12 bends in the direction of arrow R and the lower part of the mountain retaining wall 20b bends in the direction of arrow L as shown by the dotted line 20b. A compressive force is transmitted to the ground 14. In other words, since the mountain retaining walls 11a and 11b are arranged and fixed so as to contact the culvert 12, the culvert 12 and the mountain retaining walls 11a and 11b exhibit deformation characteristics as an integrated structure, No tensile force acts on the lower ground of 12 and only compressive force acts. Therefore, even if the ground improvement of this part is simple by the compaction method, and even if the retaining wall is a simple one formed by connecting, for example, a single steel sheet pile, these compaction Due to the interaction between the improved ground 14 and the mountain retaining walls 11a and 11b, it becomes possible to counteract the dynamic fluid pressures 21a and 21b during liquefaction.
[0013]
Next, the construction method of the underground structure in the liquefied ground will be described. First, the ground from the upper surface of the non-liquefied layer 15 to the height H is compacted and improved to form the improved ground 14. This ground improvement is performed by a conventional method using a plurality of sand columns 14a, and the improvement width W is determined in accordance with the width of the bottom slab 12c of the culvert 12 as an underground structure to be constructed. Next, the retaining walls 11a and 11b are constructed on both sides of the improved width W until they penetrate into the non-liquefied layer 15, and abdomen or a beam (not shown) is provided between the retaining walls 11a and 11b. Excavating until the improved ground 14 is reached. After excavating to a predetermined depth, concrete is laid flat on the bottom surface of the excavation and the concrete layer 13 is formed. And if the concrete layer 13 hardens | cures, the culvert 12 will be constructed | assembled between the mountain retaining walls 11a and 11b. A fixing tool 17 such as a diver is fixed in advance on the surfaces of the mountain retaining walls 11a and 11b, and the culvert 12 is formed so as to be embedded in the side walls 12a and 12b.
[0014]
【The invention's effect】
In the present invention, the underground structure and the mountain retaining wall are in contact with each other and integrated, and the ground directly under the underground structure is surrounded by the mountain retaining wall from both sides. Even if the pressure is applied, the tensile force does not act on the part surrounded by the mountain retaining wall directly under the underground structure, but only the compressive stress acts. It is possible to construct a foundation with sufficient resistance even if it is formed by the simple construction method described above and surrounded by a relatively lightweight mountain retaining wall.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a basic structure of the invention.
2 is a cross-sectional view showing a partially enlarged view of the basic structure of FIG. 1;
FIG. 3 is a diagram simply showing a deformation state of a sheet pile in the basic structure of FIG. 1;
[Explanation of symbols]
11a, 11b Mountain retaining wall 12 Calvert (underground structure)
12c Bottom plate 14 Improved ground 15 Non-liquefied layer W Bottom plate range

Claims (1)

液状化する可能性のある地盤において地下構造物を構築する方法であって、構築予定の地下構造物の底版範囲における地盤の所定深さから下方の非液状化層の少なくとも上面までの区間を締固めて地盤改良する工程と、前記地盤改良工程の後に前記底版範囲の対向する両側面で前記非液状化層に貫入するまで山止め壁を鋼矢板、鋼管矢板又は軽量鋼矢板から形成する工程と、改良された地盤まで前記山止め壁間を掘削する工程と、前記改良された地盤上において両側壁が山止め壁に当接して定着具により固定されるように地下構造物を構築する工程とを含む地下構造物の構築方法。  A method of constructing an underground structure on the ground that may be liquefied, and tightening a section from a predetermined depth of the ground to at least the upper surface of the lower non-liquefied layer in the bottom plate range of the underground structure to be constructed. A step of solidifying and improving the ground, and a step of forming a retaining wall from a steel sheet pile, a steel pipe sheet pile or a lightweight steel sheet pile until it penetrates into the non-liquefied layer on the opposite side surfaces of the bottom plate range after the ground improvement step. Excavating between the retaining walls to an improved ground; and constructing an underground structure so that both side walls abut against the retaining walls and are fixed by a fixing tool on the improved ground; Of building underground structures including
JP10798199A 1999-04-15 1999-04-15 Construction method of underground structure in liquefied ground Expired - Lifetime JP4189078B2 (en)

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JP5975726B2 (en) * 2012-05-15 2016-08-23 西松建設株式会社 Ground structure and ground improvement method
JP2014031706A (en) * 2012-07-11 2014-02-20 Jfe Metal Products & Engineering Inc Structure and method for inhibiting liquefaction damage
CN111576487B (en) * 2020-06-01 2021-02-09 广东佰业泰建设工程有限公司 Underground engineering foundation bottom plate structure and construction method thereof

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