JP2012241499A - Ground for fighting subsidence due to shaking by travelable inclination, and method for creating the same - Google Patents

Ground for fighting subsidence due to shaking by travelable inclination, and method for creating the same Download PDF

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JP2012241499A
JP2012241499A JP2011115744A JP2011115744A JP2012241499A JP 2012241499 A JP2012241499 A JP 2012241499A JP 2011115744 A JP2011115744 A JP 2011115744A JP 2011115744 A JP2011115744 A JP 2011115744A JP 2012241499 A JP2012241499 A JP 2012241499A
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subsidence
ground
pile
layer
improvement
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Katsutoshi Fujisaki
勝利 藤崎
Takemine Yamada
岳峰 山田
Kazuo Yoshizako
和生 吉迫
Kenichi Kawano
健一 川野
Takashi Obara
隆志 小原
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Kajima Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a ground for fighting subsidence due to shaking by a travelable inclination, which can effectively suppress such subsidence in the peripheral area of a non-liquefied layer structure and the surrounding ground thereof while suppressing the consumption of solidification material milk; and a method for creating the same.SOLUTION: A plurality of pile type improving bodies 1 are installed in a non-liquefied layer S12 of a ground S1 for fighting ground surface subsidence. The plurality of pile type improving bodies 1 are arranged in a zigzag shape, or at a vertex of a square. The pile type improving bodies 1 are adjusted to have a BL ratio of 0.2-0.4. Thus the arrangement of the plurality of pile type improving bodies 1 is the arrangement for suppressing ground surface subsidence to prevent ground surface subsidence of the ground S1 for fighting ground surface subsidence.

Description

地下水位以浅の地中構造物の周辺等における非液状化層構造物周辺領域を備える地盤に揺すり込み沈下対策を施して造成する揺すり込み沈下対策地盤およびその造成方法に関する。   The present invention relates to a subsidence subsidence ground created by applying a subsidence subsidence measure to a ground having a non-liquefied layer structure peripheral region in the vicinity of an underground structure below a groundwater level and the like, and a construction method thereof.

地下水位が高く飽和状態にある液状化層では、地震時に地盤が繰り返し変形を受けることによって水圧が上昇し、地盤におけるせん断抵抗力が失われることによって液状化現象が発生する。その一方、地下水位が低く、地下水位以浅にある緩い砂地盤では、地盤の間隙中に水分が存在するものの、不飽和状態となっているため、地震時に繰り返し変形が与えられたとしても、水圧が上昇しにくくなっている。水圧が上昇しなければ、土圧が有効応力として作用することから、地盤のせん断抵抗力が保たれるので、液状化現象は発生しない。したがって、地下水位よりも浅い位置における砂地盤は、非液状化層となっている。   In the liquefied layer where the groundwater level is high and saturated, liquefaction occurs when the ground is repeatedly deformed during an earthquake, resulting in increased water pressure and loss of shear resistance in the ground. On the other hand, in the case of loose sand ground with low groundwater level and shallower than the groundwater level, although water exists in the gap between the ground, it is in an unsaturated state. Is difficult to rise. If the water pressure does not increase, the earth pressure acts as an effective stress, so that the shear resistance of the ground is maintained, so that the liquefaction phenomenon does not occur. Therefore, the sand ground at a position shallower than the groundwater level is a non-liquefied layer.

このような非液状化層では、液状化現象は発生しないものの、地中構造物や建屋の周辺の領域(以下「非液状化層構造物周辺領域」という)では、揺すり込み沈下の発生が問題となっている。非液状化層構造物周辺領域における沈下の原因は主に2つに大別される。その1つは、地震によって地盤に繰り返しせん断力が生じることによる地盤の体積収縮であり、もう1つは、地盤と地中構造物との相対水平変位によるすべり沈下である。揺すり込み沈下は、構造物の周囲においてその現象が確認されており、上記2つの原因が複合して生じる沈下現象である。   In such a non-liquefied layer, liquefaction does not occur, but in subsurface structures and areas surrounding buildings (hereinafter referred to as “non-liquefied layer structure peripheral areas”), the occurrence of shaking subsidence is a problem. It has become. The causes of subsidence in the area around the non-liquefied layer structure are mainly divided into two main categories. One is the volumetric shrinkage of the ground due to repeated shear forces generated by the earthquake, and the other is slip settlement due to the relative horizontal displacement between the ground and the underground structure. The phenomenon of shaking subsidence has been confirmed around the structure, and is a subsidence phenomenon caused by a combination of the above two causes.

揺すり込み沈下の発生メカニズムは、液状化による地盤沈下とは明らかに異なる。このため、揺すり込み沈下対策としては、地震時に累積ひずみによる体積収縮を生じさせないように地盤のせん断剛性を高めるとともに、地盤と近接する構造物との応答差をなくし、相対水平変位を抑制するように非液状化層構造物周辺領域を改良することが必要と考えられる(非特許文献1参照)。   The generation mechanism of rock subsidence is clearly different from land subsidence due to liquefaction. For this reason, as countermeasures against sag subsidence, the shear rigidity of the ground is increased so as not to cause volume shrinkage due to accumulated strain during an earthquake, and the response difference between the ground and the adjacent structure is eliminated to suppress relative horizontal displacement. It is considered necessary to improve the peripheral region of the non-liquefied layer structure (see Non-Patent Document 1).

地下水位以浅の非液状化層構造物周辺領域(以下「改良対象領域」ともいう)の改良形式として特化した技術は特に開示されていないが、揺すり込み沈下の発生メカニズムを考慮すると、たとえば改良対象領域の全体をセメントなどの固化材によって固化させて改良体を造成する方法がある。揺すり込み沈下が発生する主な理由は、地震発生前の初期剛性が、地震後における載荷と除荷を繰り返し受ける繰り返し荷重により低下し、地盤が軟化することで地盤の変形量が大きくなり、土粒子の再配列が生じやすくなることと考えられる。また、地盤の変形量が大きくなることにより、構造物と地盤との間の相対水平変位が大きくなって構造物と地盤との間に生じた隙間に土が滑り込むことによりさらに沈下量が増大する。そこで、地盤を全面改良して初期剛性を高めることにより、繰り返し荷重を受けた後の地盤の剛性の低下量を小さくすることができ、沈下の抑制を図ることができる。   Although there is no specific technology specifically disclosed as an improved form of the area around the non-liquefied layer structure below the groundwater level (hereinafter also referred to as the “target area for improvement”), for example, if the mechanism of the occurrence of subsidence is taken into account There is a method of creating an improved body by solidifying the entire target area with a solidifying material such as cement. The main reason for the rock subsidence is that the initial stiffness before the earthquake decreases due to repeated loads that are repeatedly subjected to loading and unloading after the earthquake, and the ground softens, resulting in a large amount of ground deformation. It is thought that the rearrangement of particles is likely to occur. Also, as the amount of deformation of the ground increases, the relative horizontal displacement between the structure and the ground increases, and the amount of settlement increases further as the soil slides into the gap formed between the structure and the ground. . Therefore, by improving the entire surface of the ground and increasing the initial rigidity, the amount of decrease in the rigidity of the ground after receiving a repeated load can be reduced, and settlement can be suppressed.

ところが、改良領域の全体を固化させる工法では、固化材を大量に必要としたり、工期の長期化を招いたりするなどの問題がある。また、改良領域の全体を改良する全面改良に対して、改良領域の一部を効率的に改良する部分固化を行うことも考えられる。この部分固化では、改良領域の一部に地盤改良体を造成する工法がある。この工法では、地盤の一部を固化させるのみであるので、固化材の使用量を少なくするとともに、工期の短縮を図ることができる。   However, the method of solidifying the entire improved region has problems such as requiring a large amount of solidification material and prolonging the construction period. It is also conceivable to perform partial solidification that efficiently improves a part of the improved region in contrast to the entire surface improvement that improves the entire improved region. In this partial solidification, there is a method of creating a ground improvement body in a part of the improved region. In this construction method, only a part of the ground is solidified, so the amount of solidification material used can be reduced and the construction period can be shortened.

地盤改良体を造成する際には、深層混合処理工法や薬液注入工法が用いられる。このうち、薬液注入工法は、一般的には土中水を薬液に置換する工法であるため、地下水位以浅にある改良対象領域に適用することは適切でない。したがって、地盤改良体を造成する際には、深層混合処理工法を用いることが考えられる。   When creating a ground improvement body, a deep mixing method or a chemical injection method is used. Of these methods, the chemical solution injection method is generally a method of replacing soil water with a chemical solution, and therefore it is not appropriate to apply the method to an improvement target region that is shallower than the groundwater level. Therefore, when creating a ground improvement body, it is possible to use a deep layer processing method.

深層混合処理工法には、撹拌用の重機を用いて撹拌を行う機械式撹拌工法や固化材ミルクを地盤内で高圧噴射して撹拌を行う高圧噴射撹拌工法などがある。また、地盤の一部を深層混合処理工法によって固化させる工法として、従来、次のものが知られている。たとえば、固化材ミルクを地盤と混合撹拌して地盤改良体を平面格子状に配置して造成する。この平面格子状の地盤改良体は、側面視して壁状に形成される。この地盤改良体によって地震時における地盤のせん断変形を抑制し、地下水および土の移動を抑制する(たとえば、特許文献1、特許文献2参照)。さらには、格子状地盤改良体を単独で造成するだけでなく、杭基礎構造と併用して用いる工法も知られている(たとえば、特許文献3参照)。   The deep mixing treatment method includes a mechanical stirring method in which stirring is performed using a heavy machine for stirring, and a high-pressure jet stirring method in which solidified milk is injected at high pressure in the ground to perform stirring. Conventionally, the following is known as a method of solidifying a part of the ground by a deep mixing treatment method. For example, the solidified milk is mixed and agitated with the ground, and the ground improvement body is arranged in a plane lattice shape. This planar grid-like ground improvement body is formed in a wall shape when viewed from the side. This ground improvement body suppresses the shear deformation of the ground during an earthquake and suppresses the movement of groundwater and soil (for example, see Patent Document 1 and Patent Document 2). Furthermore, a construction method is also known in which not only a lattice-like ground improvement body is created alone but also used in combination with a pile foundation structure (for example, see Patent Document 3).

特開2000−265455号公報JP 2000-265455 A 特開2008−50787号公報JP 2008-50787 A 特開2001−342637号公報JP 2001-342637 A

石丸真,河井正:重力場模型振動台実験による底面が固定された剛な構造物近傍地盤の地震時沈下メカニズムの把握,地盤工学ジャーナル,Vol.4,No.4,369-380.Makoto Ishimaru, Tadashi Kawai: Gravity field model shaking table experiment to understand the subsidence mechanism during earthquake of a rigid structure near the bottom with a fixed bottom, Geotechnical Journal, Vol.4, No.4, 369-380.

揺すり込み沈下対策地盤を造成するにあたり、改良対象領域の全体を固化させる工法は、揺すり込み沈下を防止する対策として最も確実な工法ではある。ところが、改良対象領域の全体の固化材ミルクを注入して改良対象領域の全体を固化させていることから、大量の固化材ミルクを要するという問題があった。また、施工の際には、地盤内に注入する固化材ミルクの量と同量以下のスライムが地上に排出されるため、排出されたスライムの処理や運搬の手間が掛かるという問題もあった。   In creating ground for countermeasures against subsidence, the method of solidifying the entire area to be improved is the most reliable method to prevent subsidence. However, since the entire solidified material milk in the improvement target region is injected to solidify the entire improvement target region, there is a problem that a large amount of solidified material milk is required. In addition, when the construction is performed, slime equal to or less than the amount of the solidified milk to be injected into the ground is discharged to the ground, so that there is a problem that it takes time to process and transport the discharged slime.

一方、上記特許文献1〜3に開示された地盤の一部に格子状地盤改良体を造成する工法では、固化材ミルクや薬剤の使用量を抑制できる。さらには、固化材ミルクの使用量が少なくなるため、排出されるスライムの量も少なくなり、スライムの処理や運搬に掛かる手間を軽減することができる。   On the other hand, in the construction method for creating a grid-like ground improvement body on a part of the ground disclosed in Patent Documents 1 to 3, it is possible to suppress the use amount of the solidifying material milk and the medicine. Furthermore, since the amount of solidified milk used is reduced, the amount of slime to be discharged is also reduced, and the labor required for processing and transporting the slime can be reduced.

しかし、上記特許文献1〜3に開示された格子状地盤改良体を造成する工法においては、地盤改良体をラップさせて連続的に造成することで壁体を構築している。このため、固化材ミルクのロスが生じるという問題は依然として残されているので、さらに固化材ミルクの消費量の抑制を図る余地がある。   However, in the construction method for creating the grid-like ground improvement body disclosed in Patent Documents 1 to 3, the wall body is constructed by continuously building the ground improvement body by wrapping it. For this reason, since the problem that the loss of solidification material milk arises still remains, there is room for further suppression of the consumption of solidification material milk.

他方、改良対象領域の全体を固化させて全体改良体を造成する場合、構造物と全体改良体との剛性の差は小さくなるものの、未改良地盤と全体改良体との剛性の差は非常に大きくなっている。このため、全体改良体に対して地震動が壁の垂直方向に入力された場合、全体改良体と未改良地盤との揺れ方が大きく異なり、相対水平変位が大きく異なってしまう。したがって、全体改良体と未改良地盤との間に隙間が生じるなどして、沈下の進行を進めてしまう可能性があるという問題があった。   On the other hand, when the whole improvement object area is solidified and the whole improvement body is created, the difference in rigidity between the structure and the whole improvement body becomes small, but the difference in rigidity between the unimproved ground and the whole improvement body is very large. It is getting bigger. For this reason, when seismic motion is input to the whole improved body in the vertical direction of the wall, the way of shaking between the whole improved body and the unimproved ground is greatly different, and the relative horizontal displacement is greatly different. Therefore, there has been a problem that there is a possibility that the settlement proceeds due to a gap between the overall improved body and the unimproved ground.

そこで、本発明の課題は、固化材ミルクの消費量を抑制するとともに、非液状化層構造物周辺領域やその周囲の地盤における揺すり込み沈下を効果的に抑制することができる揺すり込み沈下対策地盤およびその造成方法を提供することにある。   Therefore, the problem of the present invention is to reduce the consumption of the solidified milk and to prevent the subsidence in the area around the non-liquefied layer structure and the surrounding subsidence effectively. And to provide a method for producing the same.

上記課題を解決した本発明に係る揺すり込み沈下対策地盤は、基盤層と、基盤層の上層における地下水位以浅の非液状化層に含まれ、地中構造物の周辺における非液状化層構造物周辺領域とを備える地盤に揺すり込み沈下対策が施された揺すり込み沈下対策地盤であって、非液状化層に複数の杭式改良体が打設されており、複数の杭式改良体は、揺すり込み沈下抑制配置とされていることを特徴とする。   The ground for subsidence subsidence according to the present invention that solves the above problems is included in the base layer and the non-liquefied layer shallower than the groundwater level in the upper layer of the base layer, and the non-liquefied layer structure around the underground structure The ground with the surrounding area is a rock subsidence countermeasure ground with a countermeasure for rock subsidence, and a plurality of pile-type improvement bodies are placed in the non-liquefaction layer, It is characterized by an arrangement that suppresses subsidence.

本発明に係る揺すり込み沈下対策地盤においては、非液状化層に複数の杭式改良体が打設されており、複数の杭式改良体は、揺すり込み沈下抑制配置とされている。揺すり込み沈下抑制配置は、揺すり込み沈下の抑制に効果的な配置であるため、地震による繰り返し変形が生じても、地表面沈下を抑制することができるので、地表面沈下による補修の必要がなくなる。したがって、非液状化層構造物周辺領域やその周囲の地盤における揺すり込み沈下を効果的に抑制することができる。また、杭式改良体が揺すり込み沈下抑制配置とされて揺すり込み沈下を抑制しているので、非液状化層構造物周辺領域の全体を固化させる場合よりも、杭式改良体形成するための固化材ミルクの消費量を抑制することができる。したがって、固化材ミルクの消費量を抑制するとともに、非液状化層構造物周辺領域やその周囲の地盤における揺すり込み沈下を効果的に抑制することができる。   In the rock subsidence countermeasure ground according to the present invention, a plurality of pile-type improvement bodies are placed in the non-liquefaction layer, and the plurality of pile-type improvement bodies are arranged to suppress the rock-in subsidence. The sunk subsidence placement is an effective way to control the squeeze subsidence, so even if it is repeatedly deformed by an earthquake, the ground subsidence can be suppressed, eliminating the need for repairs due to ground subsidence. . Therefore, it is possible to effectively suppress shaking subsidence in the non-liquefied layer structure peripheral region and the surrounding ground. In addition, since the pile type improved body is arranged to suppress the squeeze subsidence and suppress the squeeze subsidence, it is necessary to form the pile type improved body rather than solidifying the whole area around the non-liquefied layer structure. The consumption of the solidified milk can be suppressed. Therefore, it is possible to suppress the consumption of the solidified milk, and to effectively suppress the sinking and sinking in the area around the non-liquefied layer structure and the surrounding ground.

ここで、揺すり込み沈下抑制配置は、非液状化層を平面視して、複数の杭式改良体が千鳥とされた配置である態様とすることができる。   Here, the shaking subsidence suppressing arrangement can be an aspect in which a plurality of pile-type improved bodies are arranged in a staggered manner in a plan view of the non-liquefied layer.

このように、液状化層を平面視して、複数の杭式改良体が千鳥とされた配置に杭式改良体を打設することより、地表面沈下抑制に効果的となる配置である揺すり込み沈下抑制配置を好適に生成することができる。   In this way, when the liquefied layer is viewed in plan, the pile type improved body is placed in a staggered arrangement, and the rocking is an arrangement that is effective in suppressing land subsidence. A sinking suppression arrangement can be suitably generated.

また、杭式改良体同士の距離関係が、杭間スパンと打設ピッチとの比が0.2〜0.4とされている態様とすることができる。   Moreover, the distance relationship between pile type improvement bodies can be set as the aspect by which the ratio of the span between piles and the placement pitch is 0.2-0.4.

このように、杭式改良体同士の距離関係が、杭間スパンB/打設ピッチL=0.2〜0.4とされていることにより、地盤の平面的な改良率を抑制しながら、好適に揺すり込み沈下抑制配置を生成することができる。   Thus, while the distance relationship between the pile-type improved bodies is the span B between piles / the placement pitch L = 0.2 to 0.4, while suppressing the planar improvement rate of the ground, It is possible to suitably generate the sag subsidence arrangement.

さらに、揺すり込み沈下抑制配置は、非液状化層を平面視して、複数の杭式改良体が正方形の頂点にそれぞれ位置する配置である態様とすることができる。   Furthermore, the squeeze settlement suppression arrangement can be an aspect in which a plurality of pile-type improved bodies are respectively located at the vertices of a square in a plan view of the non-liquefied layer.

このように、液状化層を平面視して、複数の杭式改良体が正方形の頂点にそれぞれ位置する配置に杭式改良体を打設することによっても、揺すり込み沈下抑制配置を好適に生成することができる。   In this way, when the liquefied layer is viewed in plan, a pile-type improvement body is preferably generated by placing a pile-type improvement body in an arrangement in which a plurality of pile-type improvement bodies are respectively located at the vertices of a square. can do.

また、正方形の対角に位置する杭式改良体同士の間の杭間スパンと打設ピッチとの比が0.2〜0.4とされている態様とすることができる。   Moreover, it can be set as the aspect by which the ratio of the span between piles between pile type improved bodies located in the diagonal of a square, and a placement pitch is 0.2-0.4.

このように、正方形の対角に位置する杭式改良体同士の間の杭間スパンBS/打設ピッチL=0.2〜0.4とされていることにより、地盤の平面的な改良率を抑制しながら、好適に揺すり込み沈下抑制配置を生成することができる。   Thus, by making it the span span between piles between the pile type improvement bodies located in the diagonal of a square / setting pitch L = 0.2-0.4, the planar improvement rate of the ground It is possible to suitably generate the sag subsidence arrangement while suppressing the above.

さらに、杭式改良体が、高圧噴射撹拌によって構築されている態様とすることができる。   Furthermore, the pile type improvement body can be set as the aspect constructed | assembled by the high pressure jet stirring.

このように、杭式改良体が高圧噴射撹拌によって構築されていることにより、杭式改良体の側面に凹凸を形成することができる。   Thus, an unevenness | corrugation can be formed in the side surface of a pile type improved body by the pile type improved body being constructed | assembled by the high pressure jet stirring.

他方、上記課題を解決した本発明に係る揺すり込み沈下対策地盤の造成方法は、基盤層と、基盤層の上層における地下水位以浅の非液状化層に含まれ、地中構造物の周辺における非液状化層構造物周辺領域とを備える地盤に揺すり込み沈下対策が施された揺すり込み沈下対策を施すにあたり、複数の杭式改良体を揺すり込み沈下抑制配置として、非液状化層に複数の杭式改良体を打設することを特徴とする。   On the other hand, the method for constructing the ground for subsidence subsidence according to the present invention, which has solved the above-mentioned problems, is included in the basement layer and the non-liquefaction layer shallower than the groundwater level in the upper layer of the basement layer. When taking measures against sunk subsidence, where the ground with the surrounding area of the liquefied layer structure is subjected to sunk subsidence measures, multiple pile-type improved bodies are placed in a non-liquefied layer as a squeeze subsidence arrangement. It is characterized by placing a formula improvement body.

本発明に係る揺すり込み沈下対策地盤およびその造成方法によれば、固化材ミルクの消費量を抑制するとともに、非液状化層構造物周辺領域やその周囲の地盤における揺すり込み沈下を効果的に抑制することができる。   According to the rock subsidence countermeasure ground and its creation method according to the present invention, the consumption of the solidified milk is suppressed, and the rock subsidence in the region around the non-liquefied layer structure and the surrounding ground is effectively suppressed. can do.

第1の実施形態に係る揺すり込み沈下対策地盤の側断面図である。It is a sectional side view of the rock subsidence countermeasure ground which concerns on 1st Embodiment. 揺すり込み沈下対策地盤の平面図である。It is a top view of the rock subsidence settlement ground. 杭式改良体の拡大側断面図である。It is an expanded sectional side view of a pile type improved body. 揺すり込み沈下対策地盤の造成工程を示す工程図である。It is process drawing which shows the creation process of the sway subsidence countermeasure ground. 杭式改良体の位置関係を示す平面図である。It is a top view which shows the positional relationship of a pile type improved body. 振動実験の結果における沈下率とB/L比との関係を示すグラフである。It is a graph which shows the relationship between the settlement rate and B / L ratio in the result of a vibration experiment. 地盤の改良率とB/L比との関係を示すグラフである。It is a graph which shows the relationship between the improvement rate of a ground, and B / L ratio. 好適なB/L比の最大値を説明するためのグラフである。It is a graph for demonstrating the maximum value of suitable B / L ratio. 好適なB/L比の最小値を説明するためのグラフである。It is a graph for demonstrating the minimum value of suitable B / L ratio. 好適なB/L比と改良率との範囲を説明するためのグラフである。It is a graph for demonstrating the range of suitable B / L ratio and improvement rate. 杭式改良体の位置関係の他の例を示す平面図である。It is a top view which shows the other example of the positional relationship of a pile type improved body.

以下、図面を参照して、本発明の好適な実施形態について説明する。なお、各実施形態において、同一の機能を有する部分については同一の符号を付し、重複する説明は省略することがある。   Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each embodiment, portions having the same function are denoted by the same reference numerals, and redundant description may be omitted.

図1は、本発明の第1の実施形態に係る地表面沈下対策地盤の側断面図、図2は、その平面図である。図1および図2に示すように、本実施形態に係る揺すり込み沈下対策地盤である地表面沈下対策地盤S1は、基盤層S11を備えており、基盤層S11の上層には、地下水位以浅の非液状化層S12が存在している。基盤層S11は、地中構造物の支持層ともなり、地震が発生した際にも変形が起こり難い堅固な地盤である。また、非液状化層S12は、緩い砂質土などからなり、地震が発生した際に揺すり込み沈下が発生しやすい地盤である。   FIG. 1 is a side sectional view of the ground surface settlement countermeasure ground according to the first embodiment of the present invention, and FIG. 2 is a plan view thereof. As shown in FIG. 1 and FIG. 2, the ground surface settlement countermeasure ground S1 which is a ground subsidence countermeasure ground according to the present embodiment includes a basement layer S11, and the upper layer of the basement layer S11 has a shallow groundwater level. A non-liquefaction layer S12 is present. The base layer S11 also serves as a support layer for underground structures, and is a solid ground that hardly deforms even when an earthquake occurs. Further, the non-liquefied layer S12 is made of loose sandy soil and the like, and is a ground that is liable to stagnate and sink when an earthquake occurs.

また、非液状化層S12に形成された共同溝等の重要な地中構造物Mの周辺における非液状化層構造物周辺領域Rには、複数の杭式改良体1が打設されている。杭式改良体1は、非液状化層S12を超えて、その下層における基盤層S11まで到達している。杭式改良体1は、基盤層S11に根入れされているのが好ましいが、その根入れ深さは、わずかでも問題ない。また、地表面沈下対策地盤S1には、図2に示すように、複数の杭式改良体1が打設されており、そのうちの4本は、平面視して正方形の角部となる位置に配置されている。   In addition, a plurality of pile-type improved bodies 1 are placed in the non-liquefied layer structure peripheral region R in the vicinity of an important underground structure M such as a common groove formed in the non-liquefied layer S12. . The pile improvement body 1 has reached the base layer S11 in the lower layer beyond the non-liquefaction layer S12. The pile-type improved body 1 is preferably rooted in the base layer S11, but the depth of rooting is not a problem. In addition, as shown in FIG. 2, a plurality of pile-type improved bodies 1 are placed on the ground surface settlement countermeasure ground S1, and four of them are located at square corners in plan view. Has been placed.

杭式改良体1を平面視した際の径は、たとえば高圧噴射撹拌工法による場合、φ1〜5m程度である。また、複数の杭式改良体1の配置は、地表面沈下対策地盤S1の揺すり込み沈下による地表面沈下を防止する揺すり込み沈下抑制に効果的な配置である揺すり込み沈下抑制配置とされている。揺すり込み沈下抑制配置は、杭式改良体1の杭径(改良径)、杭間スパン、打設ピッチなどによって決定されている。これらの詳細については後に説明する。   The diameter when the pile-type improved body 1 is viewed in plan is, for example, about φ1 to 5 m in the case of the high-pressure jet stirring method. In addition, the arrangement of the plurality of pile-type improved bodies 1 is a sunk subsidence suppression arrangement which is an effective arrangement for suppressing sunk subsidence that prevents ground subsidence due to subsidence subsidence of the ground subsidence countermeasure ground S1. . The shaking subsidence suppression arrangement is determined by the pile diameter (improved diameter) of the pile-type improved body 1, the span between piles, the placement pitch, and the like. Details of these will be described later.

杭式改良体1は、高圧噴射撹拌や機械式撹拌によって形成することができるが、高圧撹拌噴射によって形成する場合には、図3に示すように、杭式改良体1の側面に微細な凹凸形状が付与される。図3における一点鎖線は、杭式改良体1における改良径を計測する部分を示している。   The pile-type improved body 1 can be formed by high-pressure jet agitation or mechanical agitation, but when formed by high-pressure agitation jet, fine irregularities are formed on the side surface of the pile-type improved body 1 as shown in FIG. Shape is added. The dashed-dotted line in FIG. 3 has shown the part which measures the improvement diameter in the pile type improvement body 1. FIG.

次に、本実施形態に係る地表面沈下対策地盤の造成手順について説明する。図4は地表面沈下対策地盤の造成工程を示す工程図である。図4(a)に示すように、地表面沈下対策地盤を造成する際には、まず、地中構造物Mの周辺に非液状化層S12を貫通して基盤層S11に到達する杭式改良体1を順次造成していく。図4(a)には、一部の杭式改良体1の造成が完了し、その側方における杭式改良体1を造成する状態を示している。   Next, the creation procedure of the ground surface settlement countermeasure ground according to the present embodiment will be described. FIG. 4 is a process diagram showing a process of creating a ground for subsidence. As shown in FIG. 4 (a), when constructing the ground for subsidence, first the pile type improvement that penetrates the non-liquefied layer S12 around the underground structure M and reaches the base layer S11. Build body 1 sequentially. FIG. 4A shows a state in which the creation of some of the pile-type improved bodies 1 is completed and the pile-type improved bodies 1 are created on the sides thereof.

杭式改良体1は、たとえば深層混合処理工法によって造成することができ、ここではいわゆる高圧噴射撹拌工法によって造成する。高圧噴射撹拌工法では、図4(a)に示すように、杭式改良体1を造成する位置に噴射ロッド10を挿入する。噴射ロッド10の先端部には、固化材ミルクの噴射口が形成されている。噴射ロッド10を挿入したら、図4(b)に示すように、噴射ロッド10の側方から固化材ミルクを高圧で噴射するとともに、噴射ロッド10を回転させながら徐々に引き上げていく。なお、噴射ロッド10からは固化材ミルクと圧縮空気とを噴射すると効果的である。こうして、噴射ロッド10を地表面沈下対策地盤S1の最上部まで引き上げていき、杭式改良体1の打設が完了する。以後、地表面沈下抑制配置となる各位置に杭式改良体1を打設することにより、地表面沈下対策地盤S1が造成される。   The pile-type improved body 1 can be formed by, for example, a deep mixing treatment method, and here is formed by a so-called high-pressure jet stirring method. In the high-pressure jet agitation method, as shown in FIG. 4A, the injection rod 10 is inserted at a position where the pile type improved body 1 is formed. An injection port for the solidified milk is formed at the tip of the injection rod 10. When the injection rod 10 is inserted, as shown in FIG. 4 (b), the solidified milk is injected from the side of the injection rod 10 at a high pressure and is gradually pulled up while rotating the injection rod 10. It is effective to inject solidified material milk and compressed air from the injection rod 10. In this way, the injection rod 10 is pulled up to the top of the ground surface settlement countermeasure ground S1, and the placement of the pile-type improved body 1 is completed. Thereafter, by placing the pile-type improved body 1 at each position where the ground surface settlement suppression arrangement is provided, the ground surface settlement countermeasure ground S1 is created.

このように、上記の手順で造成された地表面沈下対策地盤S1においては、非液状化層S12に複数の杭式改良体1が打設されており、複数の杭式改良体1は、地表面沈下抑制配置とされている。このため、杭式改良体1を形成するのみで表面沈下を抑制することができるので、メンテナンスの必要性を小さくしながら地表面沈下自体を抑制することができる。さらには、杭式改良体1は重複させて壁状に構築されることもないので、改良材の使用量に対する平均的な改良率を高めることができる。また、複数の杭式改良体1が地表面沈下抑制配置されていることによって、改良によるスライム排出処理を低減することができる。   In this way, in the ground subsidence countermeasure ground S1 created by the above procedure, a plurality of pile-type improvement bodies 1 are placed in the non-liquefaction layer S12. It is a surface settlement suppression arrangement. For this reason, since surface subsidence can be suppressed only by forming pile type improvement object 1, ground surface subsidence itself can be controlled, reducing the need for maintenance. Furthermore, since the pile-type improved body 1 is not overlapped and built in a wall shape, the average improvement rate with respect to the usage amount of the improved material can be increased. Moreover, the slime discharge process by improvement can be reduced by the several pile-type improvement body 1 being arrange | positioned by ground subsidence suppression arrangement | positioning.

以下、揺すり込み沈下抑制配置について説明する。本実施形態に係る地表面沈下対策地盤では、揺すり込み沈下が生じるほどの地震動が生じた場合、複数の杭式改良体1の配置によって、複数の杭式改良体1間における地表面の沈下を抑制するものである。本実施形態では、揺すり込み沈下による地表面の沈下を抑制するために、杭式改良体1の距離関係を所定の杭間スパンで構築している。ここでは、杭式改良体1における杭間スパンに着目している。   Hereinafter, the arrangement for suppressing the subsidence will be described. In the ground subsidence countermeasure ground according to the present embodiment, when an earthquake motion that causes sunk subsidence occurs, the subsidence of the ground surface between the plurality of pile improvement bodies 1 is caused by the arrangement of the plurality of pile improvement bodies 1. It is to suppress. In this embodiment, in order to suppress subsidence of the ground surface due to rock subsidence, the distance relationship of the pile-type improved body 1 is constructed with a predetermined span between piles. Here, attention is paid to the span between piles in the pile-type improved body 1.

本発明者らは、杭間スパンと地表面の沈下率との関係を調べるための模型実験を行った。実験では、図5に示すように、杭式改良体1を千鳥に配置した地表面沈下対策地盤のモデルである対策地盤モデルを作製した。この対策地盤モデルでは、実施例として、杭式改良体1の改良径Dをすべて統一した条件下で杭間スパンBを調整し、杭間スパンBと打設ピッチLとの比(以下「B/L比」という)を調整して、地表面沈下率を測定した。   The present inventors conducted a model experiment for examining the relationship between the span between piles and the settlement rate of the ground surface. In the experiment, as shown in FIG. 5, a countermeasure ground model, which is a model of the ground subsidence countermeasure ground in which the pile-type improved bodies 1 are arranged in a staggered manner, was prepared. In this countermeasure ground model, as an example, the span B between the piles is adjusted under the condition that all the improved diameters D of the pile-type improved body 1 are unified, and the ratio between the span B between the piles and the placement pitch L (hereinafter, “B / L ratio ”) was adjusted, and the land surface settlement rate was measured.

また、比較例として、従来の一般的な格子状改良における平面視した際の改良率(以下単に「改良率」という)が50%である地表面沈下率も、同条件の元で計測した。ただし、一般的な格子状改良では、60%程度まで改良率が高められる場合もある。その結果を図6に示す。図6において、実施例の結果を丸印で示し、比較例の結果を四角印で示している。また、実施例の結果に基づいて定めたB/L比に対する地表面沈下率の割合を示す第1ラインL1を求めた。   In addition, as a comparative example, a ground subsidence rate in which an improvement rate when viewed in plan in a conventional general grid improvement (hereinafter simply referred to as “improvement rate”) is 50% was also measured under the same conditions. However, in a general lattice improvement, the improvement rate may be increased to about 60%. The result is shown in FIG. In FIG. 6, the results of the examples are indicated by circles, and the results of the comparative examples are indicated by squares. Moreover, the 1st line L1 which shows the ratio of the ground surface settlement rate with respect to B / L ratio defined based on the result of the Example was calculated | required.

図6に示すように、実施例における杭式改良体1では、B/L比が小さくなるほど地表面沈下率が小さくなる傾向が見られた。このことから、地表面沈下率を低くするためには、B/L比を小さくすることが求められることがわかる。ここで、比較例としての格子状改良では、B/L比はおよそ0.7であり、この場合の地表面沈下率は、およそ0.4程度であった。   As shown in FIG. 6, in the pile type improvement body 1 in an Example, the tendency for the ground surface settlement rate to become small was seen, so that B / L ratio became small. From this, it can be seen that in order to reduce the land surface settlement rate, it is required to reduce the B / L ratio. Here, in the lattice improvement as a comparative example, the B / L ratio was about 0.7, and the ground surface settlement rate in this case was about 0.4.

次に、改良率とB/L比との関係について図7を参照して説明する。図7は、改良率とB/L比との関係を示すグラフであり、従来の格子状改良の例を第2ラインL2で示し、実施例の杭式改良の例を第3ラインL3で示している。図7に示すように、従来の格子状改良に対して、実施例の杭式改良では、同じ改良率の場合にB/L比が小さくなることがわかる。具体的に、従来の格子状改良における改良率が50%の際のB/L比が0.7程度であるのに対して、実施例の杭式改良では、改良率が50%の際のB/L比は0.2程度となる。   Next, the relationship between the improvement rate and the B / L ratio will be described with reference to FIG. FIG. 7 is a graph showing the relationship between the improvement rate and the B / L ratio. An example of conventional lattice improvement is shown by the second line L2, and an example of the pile type improvement of the embodiment is shown by the third line L3. ing. As shown in FIG. 7, it can be seen that the B / L ratio becomes smaller when the pile improvement of the example is the same improvement rate as compared with the conventional lattice improvement. Specifically, the B / L ratio when the improvement rate in the conventional lattice-like improvement is 50% is about 0.7, while the pile type improvement of the example has an improvement rate of 50%. The B / L ratio is about 0.2.

実施例に係る杭式改良では、地表面沈下率として、従来の格子状改良よりも低いかあるいはそれと同等の値を得ることができる一方で、改良率の低減を図ることが求められる。従来の格子状改良における地表面沈下率は0.4程度であることから、実施例に係る杭式改良においても地表面沈下率を0.4以下とすることが求められる。地表面沈下率が0.4となるB/L比が、杭式改良体1におけるB/L比の最大値となる。杭式改良体1におけるB/L比の最大値は、図8に示すように、0.4となる。   In the pile type improvement according to the embodiment, the ground surface settlement rate can be lower than or equivalent to the conventional grid-like improvement, but it is required to reduce the improvement rate. Since the ground surface settlement rate in the conventional lattice improvement is about 0.4, the ground surface settlement rate is required to be 0.4 or less also in the pile type improvement according to the embodiment. The B / L ratio at which the ground surface settlement rate is 0.4 is the maximum value of the B / L ratio in the pile-type improved body 1. The maximum value of the B / L ratio in the pile type improved body 1 is 0.4 as shown in FIG.

一方、従来の格子状改良における改良率は60%程度であり、杭式改良体1におけるB/L比の最小値は、この改良率60%に相当する数値である。このため、杭式改良体1におけるB/L比の最小値は、図9に示すように、0.2以上となる。したがって、実施例に係る杭式改良体1におけるB/L比は、0.2〜0.4の範囲とすることが好適となり、B/L比=0.2〜0.4の範囲に杭式改良体1を配置することにより、格子状改良よりも低い改良率で有りながら、高い沈下抑制効果を得ることができることとなる。また、図10に示すように、杭式改良体1におけるB/L比が0.2〜0.4の場合、改良率は30%〜60%程度となる。この範囲Xが、杭式改良体1を造成するための好適な条件を示す範囲となる。   On the other hand, the improvement rate in the conventional lattice improvement is about 60%, and the minimum value of the B / L ratio in the pile-type improvement body 1 is a numerical value corresponding to this improvement rate of 60%. For this reason, the minimum value of the B / L ratio in the pile-type improved body 1 is 0.2 or more as shown in FIG. Accordingly, the B / L ratio in the pile-type improved body 1 according to the embodiment is preferably in the range of 0.2 to 0.4, and the pile is in the range of B / L ratio = 0.2 to 0.4. By disposing the formula improvement body 1, a high settlement suppression effect can be obtained while the improvement rate is lower than that of the lattice improvement. Moreover, as shown in FIG. 10, when the B / L ratio in the pile-type improved body 1 is 0.2 to 0.4, the improvement rate is about 30% to 60%. This range X becomes a range which shows the suitable conditions for creating the pile type improved body 1.

以上、本発明の好適な実施形態について説明したが、本発明は上記実施形態に限定されるものではない。たとえば、上記実施形態においては、複数の杭式改良体1を正方形の頂点に配置しているが、千鳥に配置することもできる。   The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the said embodiment, although the several pile type improvement body 1 is arrange | positioned at the vertex of a square, it can also arrange | position in a staggered manner.

杭式改良体1を正方形の頂点に配置する場合には、図11に示すように、杭間スパンBSについては、正方形の対角に位置する杭式改良体同士の間の距離とする。杭間スパンBSをこの距離とすることにより、杭間スパンBS/打設ピッチL=0.2〜0.4の範囲に杭式改良体1を配置するで、格子状改良よりも低い改良率で有りながら、高い沈下抑制効果を得ることができる。   When the pile type improved body 1 is arranged at the apex of the square, as shown in FIG. 11, the inter-pile span BS is a distance between the pile type improved bodies located at the diagonal of the square. By setting the span span between piles as this distance, the pile-type improved body 1 is disposed in the range of span span BS / pile pitch L = 0.2 to 0.4, and the improvement rate is lower than that of the grid-like improvement. However, a high settlement suppression effect can be obtained.

1…杭式改良体
1A…凹凸
10…噴射ロッド
D…改良径
L…打設ピッチ
S1…地表面沈下対策地盤
S11…基盤層
S12…非液状化層
DESCRIPTION OF SYMBOLS 1 ... Pile type improvement body 1A ... Concavity and convexity 10 ... Injection rod D ... Improvement diameter L ... Placing pitch S1 ... Ground surface settlement countermeasure ground S11 ... Base layer S12 ... Non-liquefaction layer

Claims (7)

基盤層と、前記基盤層の上層における地下水位以浅の非液状化層に含まれ、地中構造物の周辺における非液状化層構造物周辺領域とを備える地盤に揺すり込み沈下対策が施された揺すり込み沈下対策地盤であって、
前記非液状化層に複数の杭式改良体が打設されており、
前記複数の杭式改良体は、揺すり込み沈下抑制配置とされていることを特徴とする揺すり込み沈下対策地盤。
A ground subsidence included in the non-liquefiable layer below the groundwater level in the upper layer of the basement layer and the surrounding area of the non-liquefied layer structure in the vicinity of the underground structure was subjected to a sunk subsidence measure It is a ground to prevent subsidence,
A plurality of pile-type improvements are placed in the non-liquefaction layer,
The plurality of pile-type improved bodies have a sunk subsidence suppression ground, wherein the sunk subsidence ground is provided.
前記揺すり込み沈下抑制配置は、前記非液状化層を平面視して、複数の前記杭式改良体が千鳥とされた配置である請求項1に記載の揺すり込み沈下対策地盤。   2. The rock subsidence countermeasure ground according to claim 1, wherein the rock subsidence suppression arrangement is an arrangement in which the non-liquefied layer is viewed in plan and a plurality of the pile-type improved bodies are arranged in a staggered manner. 前記杭式改良体同士の距離関係が、杭間スパンと打設ピッチとの比が0.2〜0.4とされている請求項2に記載の揺すり込み沈下対策地盤。   The ground subsidence countermeasure ground according to claim 2, wherein the distance relationship between the pile-type improved bodies is such that the ratio between the span between piles and the placement pitch is 0.2 to 0.4. 前記揺すり込み沈下抑制配置は、前記非液状化層を平面視して、前記複数の杭式改良体が正方形の頂点にそれぞれ位置する配置である請求項1に記載の揺すり込み沈下対策地盤。   2. The rock subsidence subsidence ground according to claim 1, wherein the rock subsidence suppression arrangement is an arrangement in which the plurality of pile-type improved bodies are respectively located at the vertices of a square in a plan view of the non-liquefied layer. 前記正方形の対角に位置する杭式改良体同士の間の杭間スパンと打設ピッチとの比が0.2〜0.4とされている請求項3に記載の揺すり込み沈下対策地盤。   The rock subsidence countermeasure ground according to claim 3, wherein a ratio of a span between piles and a placement pitch between pile-type improved bodies located on the diagonal of the square is 0.2 to 0.4. 前記杭式改良体が、高圧噴射撹拌によって構築されている請求項1〜請求項5のうちのいずれか1項に記載に揺すり込み沈下対策地盤。   The rock subsidence countermeasure ground according to any one of claims 1 to 5, wherein the pile-type improved body is constructed by high-pressure jet stirring. 基盤層と、前記基盤層の上層における地下水位以浅の非液状化層に含まれ、地中構造物の周辺における非液状化層構造物周辺領域とを備える地盤に揺すり込み沈下対策が施された揺すり込み沈下対策を施すにあたり、
前記複数の杭式改良体を揺すり込み沈下抑制配置として、前記非液状化層に前記複数の杭式改良体を打設することを特徴とする揺すり込み沈下対策地盤の造成方法。
A ground subsidence included in the non-liquefiable layer below the groundwater level in the upper layer of the basement layer and the surrounding area of the non-liquefied layer structure in the vicinity of the underground structure was subjected to a sunk subsidence measure In taking measures against stagnation and subsidence,
A method for creating a ground for countermeasures against sunk subsidence, wherein the plurality of stake type improved bodies are placed in the non-liquefied layer as a sunk subsidence restraining arrangement.
JP2011115744A 2011-05-24 2011-05-24 Ground for fighting subsidence due to shaking by travelable inclination, and method for creating the same Pending JP2012241499A (en)

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JP2020180454A (en) * 2019-04-24 2020-11-05 積水化学工業株式会社 Ground improvement foundation structure

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JPH0586617A (en) * 1991-09-27 1993-04-06 Fujita Corp Measure for liquefaction for underground structure
JPH06306847A (en) * 1993-04-27 1994-11-01 Fujita Corp Countermeasure against liquefaction of underground structure
JPH10183592A (en) * 1996-12-25 1998-07-14 Ohbayashi Corp Design method for sand compaction pile
JP2010216186A (en) * 2009-03-18 2010-09-30 Ohbayashi Corp Ground deformation restraining structure, ground deformation restraining method, and aseismatic reinforcing method

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JPH0586617A (en) * 1991-09-27 1993-04-06 Fujita Corp Measure for liquefaction for underground structure
JPH06306847A (en) * 1993-04-27 1994-11-01 Fujita Corp Countermeasure against liquefaction of underground structure
JPH10183592A (en) * 1996-12-25 1998-07-14 Ohbayashi Corp Design method for sand compaction pile
JP2010216186A (en) * 2009-03-18 2010-09-30 Ohbayashi Corp Ground deformation restraining structure, ground deformation restraining method, and aseismatic reinforcing method

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* Cited by examiner, † Cited by third party
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JP2020180454A (en) * 2019-04-24 2020-11-05 積水化学工業株式会社 Ground improvement foundation structure
JP7235579B2 (en) 2019-04-24 2023-03-08 積水化学工業株式会社 Ground improvement foundation structure

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