JP3760695B2

JP3760695B2 - Ground improvement method

Info

Publication number: JP3760695B2
Application number: JP29360499A
Authority: JP
Inventors: 昇一秋田; 敏明原本; 克郎鎌田; 充功岩田; 栄造深沢; 寛林; 道夫冨士田; 宏之山中; 岳峰山田
Original assignee: Kajima Corp
Current assignee: Kajima Corp
Priority date: 1999-10-15
Filing date: 1999-10-15
Publication date: 2006-03-29
Anticipated expiration: 2019-10-15
Also published as: JP2001115444A

Description

【０００１】
【発明の属する技術分野】
この発明は地盤改良工法に関し、特に砂や火山灰などの液状化を起こしやすい表層部の液状地盤と、その下方にある粘土やシルト等の沈下を起こしやすい軟弱地盤とに対して行われるものである。
【０００２】
【従来の技術】
一般に液状化のおそれある砂地盤、長期にわたる圧密沈下を免れない粘性土地盤などの軟弱地盤を構造物の基礎地盤として利用するには、予め安定な地盤に地盤改良する必要がある。
【０００３】
これまで、この種の地盤改良工法としては、例えば地盤中に深部まで石灰・セメントなどの科学的安定材を添加し、掘削土と強制的にかくはん混合する深層混合処理工法などによって軟弱地盤の全体を固結する固結工法、
衝撃または振動を利用して、地盤中に砂杭を打設することにより、よく締まった砂杭群を造成するサンドコンパクションパイル等によって軟弱地盤を締め固める締固め工法、
さらに、地盤中に砂杭などからなるドレーンを複数設置することで、土中水の排水距離を短くして圧密の促進と支持力の向上を図るドレーン工法などが広く知られている。
【０００４】
【発明が解決しようとする課題】
しかし、固結工法は、最も確実な施工は期待できるものの、セメントなどの安定材を大量に消費し、また広範囲にわたって行う必要があるため、コストが相当嵩む等の課題がある。
【０００５】
また、締固め工法は、施工コストは安いものの、レベル２地震のような大地震時には液状化の発生を完全に抑制できないだけでなく、締固め材として自然砂を大量に用いるときは自然環境を保全する上で望ましくない。
【０００６】
そして、ドレーン工法は、対象地盤が透水性の低い粘性土層などの場合、短期間の沈下促進と支持力の向上にも自ずと限界があり、安定な地盤になるまでに相当の期間を要する。また、コスト高、工期の長期化も避けられない。
【０００７】
さらに、わが国の場合、特に臨海部の埋立地や内陸部の地盤は、表層部が砂や火山灰など液状化を引き起こしやすい地盤で、これより下方の深層部が粘性土やシルト等の長期にわたる圧密沈下を免れない軟弱地盤で形成されている場合が多い。
【０００８】
このような地盤に対して、上述したうちの単一の工法で地盤改良をおこなったとしても、一方の地盤に対して有効であっても、他方の地盤に対しては必ずしも有効であるといはいえず、確実で信頼性の高い地盤改良をおこなうことができないという課題があった。
【０００９】
この発明は、以上の課題を解決するためになされたもので、特に表層部の液状化地盤とこれより下方の圧密未了の軟弱地盤に対して有効な地盤改良工法を提供することを課題とするものである。
【００１０】
【課題を解決するための手段】
請求項１記載の地盤改良工法は、表層部の液状化地盤の全体を、当該液状化地盤の液状化を抑止可能な強度を有する低強度固化地盤に、当該低強度固化地盤の下方にある軟弱地盤の一部を、当該軟弱地盤の沈下を抑止し、前記低強度固化地盤からの荷重を支持可能な強度を有する高強度固化体に、１打設でそれぞれ深度ごとに所要強度に地盤改良する地盤改良工法であって、前記低強度固化地盤と前記高強度固化体との境界部に前記低強度固化地盤からの荷重を前記高強度固化体に均等に分散・伝達させる高強度固化版を前記低強度固化地盤および前記高強度固化体と一体かつ前記高強度固化体と同等またはそれ以上の強度に造成する特徴とするものである。
【００１１】
請求項２記載の地盤改良工法は、請求項１記載の地盤改良工法において、高強度固化体を一方向または二方向に連続する壁状または全体に散在する柱状に造成し、当該高強度固化体間に当該高強度固化体どうしをつなぐ版状、はり状、またはブレース状の連結固化体を造成することを特徴とするものである。
【００１２】
請求項３記載の地盤改良工法は、請求項１または２記載の地盤改良工法において、低強度固化地盤、高強度固化体、連結固化体および高強度固化版は、高圧噴射工法、高圧噴射・機械攪拌併用工法、深層混合処理工法または薬液注入工法により施工することを特徴するものである。
【００１４】
【発明の実施の形態】
図１〜図６は、この発明の一例を示し、図において、地盤改良を行う地盤は表層部に砂や火山灰などの液状化を引き起こしやすい地盤（以下「液状化地盤１」という）を有し、この液状化地盤１より下方の深層部に粘性土やシルト等の長期にわたる圧密を免れない地盤（以下「軟弱地盤２」という）を有し、この軟弱地盤２の下方に支持地盤３がある。
【００１５】
液状化地盤１に対しては、液状化の発生を抑止できる程度の強度（目安として一軸圧縮強度が９．８０６６５×１０⁴Ｐａ程度）で、液状化地盤１の全体に対して地盤改良を行う。こうして液状化地盤１を改良してできた地盤を低強度固化地盤４という。
【００１６】
一方、軟弱地盤２に対しては、長期にわたる圧密沈下を抑止でき程度の強度、または低強度固化地盤４から伝わる荷重に耐えうる程度の強度、あるいは長期圧密沈下を抑止し、かつ低強度固化地盤４から伝わる荷重に耐えうる程度の強度を有するように地盤改良を行う。
【００１７】
また、例えば一方向に平行に連続する壁状に（図３，４参照）、または二方向（平面格子状）に平行に連続する壁状に（図１参照）、あるいは全体に均等に散在する柱状に（図５，６参照）、部分的に地盤改良を行う。
【００１８】
さらに下方の支持地盤３に確実に到達するまで（図１，２参照）、または支持地盤３に対して軟弱地盤２から連続して所定深さ（図３，４，５参照）、あるいは支持地盤３と低強度固化地盤４の両方の地盤に対して軟弱地盤２から連続して所定深さ（図６参照）地盤改良を行うことにより、軟弱地盤２の地盤改良部（後述する高強度固化体５）と支持地盤３、または支持地盤３および低強度固化地盤４との一体化を図る。こうして、軟弱地盤２の一部を改良してできた部分を高強度固化体５という。
【００１９】
なお、高強度固化体５の強度、厚さ、径、間隔などの形態については、軟弱地盤２の地質状況などを検討して決定するものとする。
例えば図１と図２は、複数の高強度固化体５が平面格子形の壁状に連続して造成されている例を示し、図３と図４は、複数の高強度固化体５が一方向に平行に壁状に連続し、かつ支持地盤３に対して所定の深さまで、軟弱地盤２から連続して造成されている例を示したものである。
【００２０】
また図５は、高強度固化体５が全体に均等に柱状に散在し、かつ支持地盤３に対して軟弱地盤２から連続して所定の深さまで連続して造成されている例を示したものである。
【００２１】
そして図６は、高強度固化体５が全体に均等に柱状に散在し、かつ支持地盤３と低強度固化地盤４の両方の地盤に対して所定の深さまで、軟弱地盤２から連続して造成されている例を示したものである。
【００２２】
いずれの例においても、高強度固化体５の中間部に隣接する複数の高強度固化体５どうしを一体的につなぐ連結固化体（図省略）を版状、はり状、あるいはブレース状に設けてもよい。
【００２３】
さらに、必要に応じて液状化地盤１と軟弱地盤２との境界部分に低強度固化地盤４からの荷重を高強度固化体５に均等に分散・伝達させる高強度固化版６を低強度固化地盤４および高強度固化体５と一体に造成する。なお、高強度固化版６は高強度固化体５と同等またはそれ以上の強度に形成するものとする。図２（ａ）、（ｂ）はその一例を示したものである。
【００２４】
なお、液状化地盤１を低強度固化地盤４に、軟弱地盤２の一部を高強度固化体５にそれぞれ地盤改良し、また液状化地盤１と軟弱地盤２との境界部に高強度固化盤６を造成する方法としては、高圧噴射工法、高圧噴射・機械攪拌併用工法、深層混合処理工法などによる他に、例えばセメントミルクや水ガラス等の薬液を地中に注入（グラウト）することにより地層を固化させる薬液注入工法などがある。
【００２５】
その際、深層混合処理工法で行う場合は、出現深度ごとに所定の強度に改良できるようにセメント等の添加材（固化材）の添加量を適宜変えて行う。また、柱状改良を適宜ラップさせながら、繰り返し地盤改良を行う。
【００２６】
また特に、高圧噴射・機械攪拌併用工法で行う場合は、例えば図７（ａ）〜（ｅ）に図示するように、噴射水（セメントミルク）の圧力、吐出量、配合、打設速度を変えることにより、あるいは高圧噴射部と機械噴射部のセメントミルクの吐出口の位置、角度などを操作することにより、さらにはセメントミルクの配合を適宜変更することにより、液状化地盤と軟弱地盤の改良に際して、１打設で改良土の径と強度を任意に変更することができ、低コスト施工が可能である。
【００２７】
例えば、図７（ａ）に図示する例では、軟弱地盤２に対して機械攪拌により高強度改良機械攪拌部５ａを形成し、この高強度改良機械攪拌部５ａの外側に高圧噴射により高強度改良高圧噴射部５ｂを形成する。
【００２８】
また、液状化地盤１に対しては、機械攪拌により低強度改良機械攪拌部４ａを高強度改良機械攪拌部５ａから連続して形成し、その外側に高圧噴射により低強度改良高圧噴射部４ｂを形成している。
【００２９】
さらに、液状化地盤１に対して所定の深さまで、高強度改良機械攪拌部５ａから連続して高強度改良機械攪拌部５ｃを形成している。
こうして高強度改良機械攪拌部５ａ，５ｃと高強度高圧噴射部５ｂが１打設ないし数打設、横方向に一体に形成されることで、所定径の柱状をなす高強度固化体５になり、また横方向に連続して形成されることで、所定厚の壁状をなす高強度固化体５になる。
【００３０】
また、低強度改良機械攪拌部４ａと低強度改良高圧噴射部４ｂが四方に連続して形成されることで低強度固化盤４となる。
また、図７（ｂ）に図示する例では、軟弱地盤２に対して機械攪拌により高強度改良機械攪拌部５ａのみを形成し、液状化地盤１に対して低強度改良機械攪拌部４ａと低強度高圧噴射部４ｂを形成し、かつ液状化地盤１に対して所定の深さまで、高強度改良機械攪拌部４ｃを形成している。
【００３１】
さらに図７（ｄ）と図７（ｅ）に図示する例では、液状化地盤１と軟弱地盤２との境部に高圧噴射により高強度改良高圧噴射部６ａを形成し、高強度改良高圧噴射部６ａを四方に連続して形成することで高強度固化版６となる。
【００３２】
【発明の効果】
この発明は以上説明した通りであり、地層の形状・強度を地盤ごとに必要最少限に抑えていることから、低コストで確実に沈下および液状化を防止でき、この点、特に固結方法よりすぐれている。
【００３３】
表層部の液状化地盤に対しては、必要最少限の強度にて全面的に固結させることから、液状化を確実に抑止することができる。
また、改良後の地盤は、表層部の低強度地盤とこれより下方の高強度地盤とからなるため、施工後に発生する軟弱地盤の沈下による液状化地盤あるいはその上に構築される構造物に沈下の心配がなく、この点、特に締固め工法よりすぐれている。
【００３４】
また、固化材ミルクの高圧噴射と攪拌ロッドの回転とにより、固化材ミルクと掘削土とを攪拌・混合する地盤改良を行い、その際、深度ごとに噴射水（セメントミルク）の圧力、吐出量、配合、打設速度などを変え、適宜強度を変えて連続的に改良することにより、施工サイクルが短く、工期の短縮化、経済施工が可能であり、この点、ドレーン工法よりすぐれている。
【００３５】
また、施工後、改良地盤が硬化するまでの所定の養生期間（１週間〜４週間ほど）を経過すれば、供用できて短期間での使用が可能である。
さらに、液状化地盤と軟弱地盤との境界部分に改良土盤を設けることにより、軟弱地盤からの過剰間隙水圧の上昇を確実に遮断できて、低強度地盤の液状化を確実に抑止して、地盤の安定化を図ることができるだけでなく、版状の軟弱地盤を介して複数の高強度体が一体的に剛接合されることで、支持強度のきわめて大きい基礎地盤を提供できる。
【００３６】
特に、わが国の臨海部の埋立地のように、表層部に砂や火山灰などの液状化を起こしやす液状化地盤を、その下方に粘土やシルト等の長期圧密を起こしやすい軟弱地盤を有する地盤の地盤改良に適している。
【図面の簡単な説明】
【図１】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図２】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図３】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図４】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図５】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図６】本工法で改良された地盤を示し、（ａ）はその縦断面図、（ｂ）は（ａ）におけるイ−イ線断面図である。
【図７】（ａ）〜（ｅ）は施工方法を示す縦断面図である。
【符号の説明】
１液状化地盤（液状化を引き起こしやすい地盤）
２軟弱地盤（圧密を免れない地盤）
３支持地盤
４低強度固化地盤（液状化地盤を改良してできた地盤）
４ａ低強度改良機械攪拌部
４ｂ低強度改良高圧噴射部
５高強度固化体（軟弱地盤の一部を改良してできた部分）
５ａ高強度改良機械攪拌部
５ｂ高強度改良高圧噴射部
５ｃ高強度改良機械攪拌部
６高強度固化版
６ａ高強度改良高圧噴射部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground improvement method, and is particularly applied to a liquid ground of a surface layer portion that is liable to cause liquefaction such as sand and volcanic ash, and a soft ground that is liable to cause subsidence of clay, silt, and the like below. .
[0002]
[Prior art]
In general, in order to use a soft ground such as a sand ground that may be liquefied or a viscous ground that cannot avoid consolidation settlement over a long period of time, it is necessary to improve the ground to a stable ground beforehand.
[0003]
So far, this kind of ground improvement method has been, for example, the addition of scientific stabilizers such as lime and cement to the deep part of the ground, and the entire soft ground by a deep mixing treatment method that forcibly mixes with the excavated soil. Consolidation method,
A compaction method in which soft ground is compacted by a sand compaction pile that creates a well-tightened sand pile group by placing sand piles in the ground using impact or vibration,
Furthermore, a drain construction method is widely known in which a plurality of drains made of sand piles or the like are installed in the ground so that the drainage distance of soil water is shortened to promote consolidation and improve bearing capacity.
[0004]
[Problems to be solved by the invention]
However, although the most reliable construction method can be expected, the consolidation method has a problem that the cost is considerably increased because it consumes a large amount of a stabilizing material such as cement and needs to be performed over a wide range.
[0005]
In addition, although the compacting method is low in construction cost, not only can liquefaction be prevented completely during a large earthquake such as a level 2 earthquake, but the natural environment should be reduced when using a large amount of natural sand as a compacting material. It is not desirable for maintenance.
[0006]
In the drain construction method, when the target ground is a viscous soil layer with low water permeability, there is a limit to the promotion of settlement in a short period of time and the improvement of the bearing capacity, and a considerable period is required until the ground becomes stable. In addition, high costs and long construction periods are inevitable.
[0007]
Furthermore, in Japan, especially in coastal landfills and inland areas, the surface layer is prone to liquefaction such as sand and volcanic ash, and the deeper layers below this are long-term consolidations such as viscous soil and silt. It is often formed of soft ground that cannot escape subsidence.
[0008]
For such ground, even if the ground improvement is performed by the single method described above, even if it is effective for one ground, it is not necessarily effective for the other ground. In other words, there was a problem that it was impossible to make reliable and reliable ground improvement.
[0009]
The present invention was made to solve the above problems, and in particular, to provide an effective ground improvement method for the liquefied ground of the surface layer portion and the soft ground that has not been consolidated below. To do.
[0010]
[Means for Solving the Problems]
The ground improvement construction method according to claim 1, wherein the entire liquefied ground of the surface layer portion is changed to a low strength solidified ground having a strength capable of suppressing liquefaction of the liquefied ground, and the softness located below the low strength solidified ground. A part of the ground is suppressed to the settlement of the soft ground, and the ground is improved to the required strength at each depth by one placement into a high strength solidified body having a strength capable of supporting the load from the low strength solidified ground. A ground improvement method, wherein a high-strength solidified plate that uniformly distributes and transmits a load from the low-strength solidified ground to the boundary portion between the low-strength solidified ground and the high-strength solidified body It is characterized in that it is integrated with the low-strength solidified ground and the high-strength solidified body and has a strength equal to or higher than that of the high-strength solidified body.
[0011]
The ground improvement method according to claim 2 is the ground improvement method according to claim 1, wherein the high-strength solidified body is formed into a wall shape continuous in one or two directions or a columnar shape scattered throughout, and the high-strength solidified body. A plate-like, beam-like, or brace-like connected solidified body connecting the high-strength solidified bodies therebetween is formed.
[0012]
The ground improvement method according to claim 3 is the ground improvement method according to claim 1 or 2, wherein the low-strength solidified ground, the high-strength solidified body, the connected solidified body, and the high-strength solidified plate are a high-pressure jet method, a high-pressure jet machine It is characterized in that it is constructed by a combined stirring method, a deep mixing method or a chemical solution injection method.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
1 to 6 show an example of the present invention. In the figure, the ground for ground improvement has a ground (hereinafter referred to as “liquefied ground 1”) that is liable to cause liquefaction such as sand and volcanic ash in the surface layer portion. In the deep part below the liquefied ground 1, there is a ground (hereinafter referred to as “soft ground 2”) such as cohesive soil or silt that cannot escape for a long period of time, and below this soft ground 2 is a supporting ground 3. .
[0015]
For the liquefied ground 1, the ground is improved with respect to the entire liquefied ground 1 with a strength that can prevent the occurrence of liquefaction (as a guide, the uniaxial compressive strength is about 9.80665 × 10 ⁴ Pa). . The ground obtained by improving the liquefied ground 1 is referred to as a low strength solidified ground 4.
[0016]
On the other hand, for the soft ground 2, the strength that can suppress the consolidation settlement for a long time, the strength that can withstand the load transmitted from the low-strength solidified ground 4, or the long-term consolidation settlement, and the low-strength solidified ground The ground will be improved so that it has enough strength to withstand the load transmitted from 4.
[0017]
Further, for example, a wall shape continuous in one direction (see FIGS. 3 and 4), a wall shape continuous in two directions (plane lattice shape) (see FIG. 1), or evenly distributed throughout. In the form of a column (see FIGS. 5 and 6), the ground is partially improved.
[0018]
Furthermore, until it reaches the lower support ground 3 reliably (see FIGS. 1 and 2), or continuously from the soft ground 2 to the support ground 3 (see FIGS. 3, 4 and 5), or the support ground 3 and the low strength solidified ground 4 are continuously improved from the soft ground 2 to a predetermined depth (see FIG. 6), and the ground improvement portion of the soft ground 2 (high strength solidified body described later) 5) and the supporting ground 3, or the supporting ground 3 and the low strength solidified ground 4 are integrated. In this way, a portion obtained by improving a part of the soft ground 2 is referred to as a high strength solidified body 5.
[0019]
In addition, about forms, such as an intensity | strength, thickness, a diameter, a space | interval, of the high-strength solidified body 5, it shall determine by examining the geological condition of the soft ground 2, etc.
For example, FIG. 1 and FIG. 2 show an example in which a plurality of high-strength solidified bodies 5 are continuously formed in a planar lattice-like wall shape, and FIG. 3 and FIG. An example is shown in which a wall is formed parallel to the direction and continuously formed from the soft ground 2 to a predetermined depth with respect to the supporting ground 3.
[0020]
Further, FIG. 5 shows an example in which the high-strength solidified bodies 5 are evenly dispersed in a column shape as a whole and are continuously formed from the soft ground 2 to the supporting ground 3 to a predetermined depth. It is.
[0021]
FIG. 6 shows that the high-strength solidified bodies 5 are continuously distributed from the soft ground 2 to a predetermined depth with respect to both the supporting ground 3 and the low-strength solidified ground 4 in a uniform column shape. An example is shown.
[0022]
In any example, a connection solidified body (not shown) that integrally connects a plurality of high-strength solidified bodies 5 adjacent to an intermediate portion of the high-strength solidified body 5 is provided in a plate shape, a beam shape, or a brace shape. Also good.
[0023]
Further, if necessary, a high-strength solidified plate 6 that disperses and transmits the load from the low-strength solidified ground 4 to the high-strength solidified body 5 evenly at the boundary between the liquefied ground 1 and the soft ground 2 is provided. 4 and the high-strength solidified body 5. The high-strength solidified plate 6 is formed to have a strength equal to or higher than that of the high-strength solidified body 5. FIGS. 2A and 2B show an example.
[0024]
The liquefied ground 1 is improved to the low-strength solidified ground 4 and the soft ground 2 is partially improved to the high-strength solidified body 5, and the high-strength solidified ground is provided at the boundary between the liquefied ground 1 and the soft ground 2. In addition to the high-pressure injection method, the high-pressure injection / mechanical stirring method, the deep-mixing method, etc., for example, a chemical layer such as cement milk or water glass is injected into the ground (grouting). There is a chemical injection method that solidifies.
[0025]
In this case, when the deep layer mixing method is used, the addition amount of an additive (solidification material) such as cement is appropriately changed so that the strength can be improved to a predetermined strength at each appearance depth. Moreover, the ground improvement is repeatedly performed while appropriately wrapping the columnar improvement.
[0026]
In particular, when the high pressure injection / mechanical stirring method is used, for example, as shown in FIGS. 7A to 7E, the pressure, discharge amount, blending, and setting speed of the injection water (cement milk) are changed. By changing the position and angle of the cement milk discharge port of the high-pressure injection unit and the machine injection unit, and by changing the composition of the cement milk as appropriate, the liquefied ground and soft ground can be improved. The diameter and strength of the improved soil can be arbitrarily changed with one placement, and low-cost construction is possible.
[0027]
For example, in the example shown in FIG. 7A, a high strength improved mechanical stirring portion 5a is formed by mechanical stirring on the soft ground 2, and high strength is improved by high pressure injection outside the high strength improved mechanical stirring portion 5a. A high-pressure injection unit 5b is formed.
[0028]
Further, for the liquefied ground 1, a low strength improved mechanical stirring unit 4a is formed continuously from the high strength improved mechanical stirring unit 5a by mechanical stirring, and a low strength improved high pressure spraying unit 4b is formed on the outside by high pressure injection. Forming.
[0029]
Furthermore, the high-strength improved mechanical stirring unit 5c is formed continuously from the high-strength improved mechanical stirring unit 5a up to a predetermined depth with respect to the liquefied ground 1.
Thus, the high-strength improved mechanical stirring parts 5a and 5c and the high-strength high-pressure injection part 5b are integrally formed in one or several places and in the lateral direction, thereby forming a high-strength solidified body 5 having a columnar shape with a predetermined diameter. Further, by forming continuously in the lateral direction, the high-strength solidified body 5 having a wall shape with a predetermined thickness is obtained.
[0030]
Further, the low-strength solidifying board 4 is formed by continuously forming the low-strength improved mechanical stirring section 4a and the low-strength improved high-pressure jet section 4b in all directions.
In the example illustrated in FIG. 7B, only the high strength improved mechanical stirring unit 5 a is formed on the soft ground 2 by mechanical stirring, and the low strength improved mechanical stirring unit 4 a and the low ground are reduced on the liquefied ground 1. The high-strength high-pressure injection unit 4b is formed, and the high-strength improved mechanical stirring unit 4c is formed to a predetermined depth with respect to the liquefied ground 1.
[0031]
Furthermore, in the example illustrated in FIG. 7D and FIG. 7E, a high-strength improved high-pressure jet 6a is formed by high-pressure jet at the boundary between the liquefied ground 1 and the soft ground 2, thereby improving the high-strength high-pressure jet. The high-strength solidified plate 6 is formed by continuously forming the portions 6a in all directions.
[0032]
【The invention's effect】
This invention is as described above, and since the shape and strength of the formation is suppressed to the minimum necessary for each ground, it is possible to reliably prevent subsidence and liquefaction at low cost. It is excellent.
[0033]
Since the liquefied ground of the surface layer portion is solidified entirely with the minimum necessary strength, liquefaction can be reliably suppressed.
In addition, since the improved ground consists of a low-strength ground in the surface layer and a high-strength ground below it, it will sink to the liquefied ground due to the settlement of the soft ground that occurs after construction or to the structure built on it. This is superior to the compaction method.
[0034]
In addition, the ground where the solidified milk and the excavated soil are stirred and mixed is improved by high-pressure injection of the solidified milk and the rotation of the stirring rod. At that time, the pressure and discharge amount of the spray water (cement milk) at each depth It is possible to shorten the construction cycle, shorten the construction period, and economical construction by changing the composition, setting speed, etc., and changing the strength as appropriate, which is superior to the drain method.
[0035]
Moreover, if the predetermined curing period (about 1 week-4 weeks) until the improved ground hardens | cures after construction, it can be used and can be used for a short period of time.
Furthermore, by providing improved soil at the boundary between the liquefied ground and the soft ground, it is possible to reliably block the increase in excess pore water pressure from the soft ground, and to reliably prevent liquefaction of the low-strength ground, Not only can the ground be stabilized, but a plurality of high-strength bodies can be rigidly joined together via a plate-like soft ground, thereby providing a foundation ground with extremely high support strength.
[0036]
In particular, as in landfills in coastal areas in Japan, the ground layer has a liquefied ground that tends to cause liquefaction such as sand and volcanic ash, and a soft ground that tends to cause long-term consolidation such as clay and silt below it. Suitable for ground improvement.
[Brief description of the drawings]
1A and 1B show a ground improved by the present construction method, wherein FIG. 1A is a longitudinal sectional view thereof, and FIG. 1B is a sectional view taken along a line II in FIG.
2A and 2B show a ground improved by the present construction method, wherein FIG. 2A is a longitudinal sectional view thereof, and FIG. 2B is a sectional view taken along the line II in FIG.
FIGS. 3A and 3B show a ground improved by the present construction method, wherein FIG. 3A is a longitudinal sectional view thereof, and FIG. 3B is a sectional view taken along the line II in FIG.
4A and 4B show a ground improved by the present construction method, in which FIG. 4A is a longitudinal sectional view thereof, and FIG. 4B is a sectional view taken along the line II in FIG.
FIGS. 5A and 5B show the ground improved by the present construction method, wherein FIG. 5A is a longitudinal sectional view thereof, and FIG. 5B is a sectional view taken along the line II in FIG.
6A and 6B show a ground improved by the present construction method, wherein FIG. 6A is a longitudinal sectional view thereof, and FIG. 6B is a sectional view taken along the line II in FIG.
FIGS. 7A to 7E are longitudinal sectional views showing a construction method.
[Explanation of symbols]
1 Liquefaction ground (ground that is liable to cause liquefaction)
2 Soft ground (ground that does not escape consolidation)
3 Supporting ground 4 Low strength solidified ground (ground made by improving liquefied ground)
4a Low strength improved mechanical stirring unit 4b Low strength improved high pressure jet unit 5 High strength solidified body (part made by improving a part of soft ground)
5a High-strength improved mechanical stirring section 5b High-strength improved high-pressure jet section 5c High-strength improved mechanical stirring section 6 High-strength solidified plate 6a High-strength improved high-pressure jet section

Claims

表層部の液状化地盤の全体を、当該液状化地盤の液状化を抑止可能な強度を有する低強度固化地盤に、当該低強度固化地盤の下方にある軟弱地盤の一部を、当該軟弱地盤の沈下を抑止し、前記低強度固化地盤からの荷重を支持可能な強度を有する高強度固化体に、１打設でそれぞれ深度ごとに所要強度に地盤改良する地盤改良工法であって、前記低強度固化地盤と前記高強度固化体との境界部に前記低強度固化地盤からの荷重を前記高強度固化体に均等に分散・伝達させる高強度固化版を前記低強度固化地盤および前記高強度固化体と一体かつ前記高強度固化体と同等またはそれ以上の強度に造成することを特徴とする地盤改良工法。The entire liquefied ground of the surface layer portion is made into a low-strength solidified ground having a strength capable of suppressing the liquefaction of the liquefied ground, a part of the soft ground below the low-strength solidified ground, subsidence suppress, the high strength solidification body having a support strength capable of a load from the low intensity solidified soil, a soil improvement method of ground improvement to the required intensity for each in one stroke setting depth, the low intensity A high-strength solidified plate that disperses and transmits a load from the low-strength solidified ground to the high-strength solidified body evenly at the boundary between the solidified ground and the high-strength solidified body. The ground improvement construction method is characterized in that it is formed with a strength equal to or higher than that of the high-strength solidified body .

高強度固化体を一方向または二方向に連続する壁状または全体に散在する柱状に造成し、当該高強度固化体間に当該高強度固化体どうしをつなぐ版状、はり状、またはブレース状の連結固化体を造成することを特徴とする請求項１記載の地盤改良工法。 A high-strength solidified body is formed into a wall shape that is continuous in one or two directions or a column that is scattered throughout, and a plate-like, beam-like, or brace-like shape that connects the high-strength solidified bodies between the high-strength solidified bodies. The ground improvement construction method according to claim 1, wherein a consolidated solid body is formed .

低強度固化地盤、高強度固化体、連結固化体および高強度固化版は、高圧噴射工法、高圧噴射・機械攪拌併用工法、深層混合処理工法または薬液注入工法により施工することを特徴する請求項１または２記載の地盤改良工法。The low-strength solidified ground, the high-strength solidified body, the connected solidified body and the high-strength solidified plate are constructed by a high-pressure injection method, a high-pressure injection / mechanical stirring combined method, a deep mixing treatment method or a chemical solution injection method. Or the ground improvement construction method of 2 description.