JP4605856B2

JP4605856B2 - Simplified calculation method of lattice spacing to prevent liquefaction in lattice improved ground by deep mixing method.

Info

Publication number: JP4605856B2
Application number: JP2000176354A
Authority: JP
Inventors: 亮一馬場崎; 明彦内田; 清山下; 忠彦塩見; 睦博吉澤; 貞友鬼丸; 正一津國; 裕司田屋
Original assignee: Takenaka Corp; Takenaka Civil Engineering and Construction Co Ltd
Current assignee: Takenaka Corp; Takenaka Civil Engineering and Construction Co Ltd
Priority date: 2000-06-13
Filing date: 2000-06-13
Publication date: 2011-01-05
Anticipated expiration: 2020-06-13
Also published as: JP2001355229A

Description

【０００１】
【発明の属する技術分野】
この発明は、地震時に液状化し易い地盤（砂質地盤）の液状化防止のため、深層混合処理工法を用いて格子状に地盤改良する場合に適正な格子間隔を簡易に算定する格子間隔簡易算定法の技術分野に属する。
【０００２】
【従来の技術】
地震時に液状化し易い地盤（砂質地盤）中に固化改良壁を格子状に形成して地盤の液状化を防止する技術は、例えば、特許第１９３０１６４号、特許第２１３１０７０号公報等に種々開示されている。
【０００３】
しかし、寸法的にどのような格子が有効かつ経済的であるかについて研究、開発された技術は、特許第２５６８１１５号に開示されている程度である。
【０００４】
ところで、地盤の液状化簡易判定法については、液状化発生に対する安全率としてＦι値を用いたものが既に公知である（建築基礎構造設計指針）。
【０００５】
【本発明が解決しようとする課題】
前記Ｆι値を用いた液状化簡易判定法をベースにして適正な格子間隔を算定する技術は、前記従来の算定方法より精度的に更なる飛躍が期待できるものの、未だ開発されていないのが実状である。
【０００６】
本発明の目的は、Ｆι値を用いた液状化簡易判定法をベースに、改良体の剛性、液状化層厚を加味して適正な格子間隔を簡易に精度良く算定することができる、深層混合処理工法による格子状改良地盤における液状化防止のための格子間隔簡易算定法を提供することにある。
【０００７】
【課題を解決するための手段】
上記従来技術の課題を解決するための手段として、請求項１に記載した発明に係る、深層混合処理工法による格子状改良地盤における液状化防止のための格子間隔を簡易算定法は、
地震時に液状化し易い地盤に深層混合処理工法により格子状の改良地盤を造成する場合に液状化防止に適正な格子間隔を簡易算定する方法であって、
地盤内の検討深さの液状化抵抗比（τｌ／σｚ’）を求めると共に地震時に加わる繰返しせん断応力比（τｄ／σｚ’）を求め、両者の比（τｌ／σｚ’）／（τｄ／σｚ’）をとって液状化に対する安全率Ｆι値を求める液状化簡易判定法において、
前記繰返しせん断応力比（τｄ／σｚ’）について、地震応答解析に基づく格子間隔（Ｌ）の影響度を表す補正係数Ｆ（Ｌ）、改良体の剛性（Ｇ）の影響度を表す補正係数Ｆ（Ｇ）、及び液状化層厚（Ｈ）の影響度を表す補正係数Ｆ（Ｈ）をそれぞれ乗じて補正する式を変形し格子間隔（Ｌ）について解くことより、前記格子状改良地盤の適正な格子間隔（Ｌ）を算定することを特徴とする。
【０００８】
【発明の実施の形態、及び実施例】
請求項１に記載した発明は、地震時に液状化し易い地盤に深層混合処理工法により格子状の改良地盤を造成する場合に液状化防止に適正な格子間隔を簡易に算定する方法である。
地盤内の検討深さの液状化抵抗比（τｌ／σｚ’）を求めると共に地震時に加わる繰返しせん断応力比（τｄ／σｚ’）を求め、両者の比（τｌ／σｚ’）／（τｄ／σｚ’）をとって液状化に対する安全率Ｆι値を求める液状化簡易判定法において、
前記繰返しせん断応力比について、地震応答解析に基づく格子間隔（Ｌ）の影響度を表す補正係数Ｆ（Ｌ）、改良体の剛性（Ｇ）の影響度を表す補正係数Ｆ（Ｇ）、及び液状化層厚（Ｈ）の影響度を表す補正係数Ｆ（Ｈ）を乗じて補正する式を変形し格子間隔（Ｌ）について解くことより、前記格子状改良地盤の適正な格子間隔（Ｌ）を算定する。
【０００９】
前記建築基礎構造設計指針によれば、Ｆι値を用いた液状化簡易判定の概要は以下に説明する通りである。
【００１０】
（１）繰返しせん断応力比（τｄ／σｚ’）を下記の［数１］のように求める。
［数１］
τｄ／σｚ’＝γｎ・αｍａｘ／ｇ・σｚ／σｚ’・γｄ
上記［数１］について、各符号の意味は下記の通り。
τｄ：水平面に生じる等価な一定繰返しせん断応力振幅（t/m²）
σｚ’：検討深さにおける有効土被り圧（鉛直有効応力）（t/m²）
γｎ：等価な繰返し回数に関する補正係数で、γｎ＝０．１（Ｍ−１）。
但し、Ｍは地震のマグニチュード
αｍａｘ：地表面における設計用水平加速度（Gal）
ｇ：重力加速度（980Gal）
σｚ：検討深さにおける全土被り圧（鉛直全応力）（t/m²）
γｄ：地盤が剛体でないことによる低減係数で（１−０．０１５ｚ）。
ｚはメートル単位で表した地表面からの深さを表す。
【００１１】
（２）液状化抵抗比（τｌ／σｚ’）を求める。
但し、上記のτｌは、水平断面における液状化抵抗である。
この液状化抵抗比（τｌ／σｚ’）は、下記［数２］と、図１Ａ、Ｂに基づいて求められる。
［数２］
Ｎ_ａ＝Ｎ_１＋ΔＮ_ｆ
Ｎ_１＝Ｃ_Ｎ・Ｎ
Ｃ_Ｎ＝√１０／σｚ’
上記［数２］における各符号の意味は以下の通り。
Ｎ_ａ：補正Ｎ値
Ｎ_１：換算Ｎ値
ΔＮ_ｆ：細粒土含有率に応じた補正Ｎ値増分で、図１Ａによる。
Ｃ_Ｎ：換算Ｎ値の係数
Ｎ：とんび法または自動落下法による実測Ｎ値
【００１２】
図１Ｂ中のせん断ひずみ振幅５％曲線を用いて、補正Ｎ値（Ｎ_ａ）に対する液状化抵抗比（τｌ／σｚ’）を求める。
そして、安全率（Ｆι）を、液状化抵抗比（τｌ／σｚ’）／繰返しせん断応力比（τｄ／σｚ’）で求め、この安全率（Ｆι）の値が１以下であれば液状化し、１より大きければ液状化しないと判定する（以上がＦι値を用いた液状化簡易判定の概要である。）。
【００１３】
ところで、本発明者は、請求項１に記載した発明において、地震時に液状化し易い地盤に深層混合処理工法により格子状の改良地盤を造成する場合に、格子間の原地盤内に発生する等価な繰返しせん断応力比は、格子間隔（Ｌ）、改良体の剛性（Ｇ）、液状化層厚（Ｈ）、および入力地震波により影響を受けると考え、これらを解析パラメータとして地震応答解析（動的解析パラメトリックスタディ）を行った（図２Ａ、Ｂ、Ｃ参照）。
【００１４】
その結果、格子間の原地盤内に発生する等価な繰返しせん断応力比（τｄ／σｚ’）は、建築基礎構造設計指針の外力評価式に基づく算定式に、格子間隔（Ｌ）の影響度、改良体の剛性（Ｇ）の影響度、液状化層厚（Ｈ）の影響度をそれぞれ、前記図２Ａ〜Ｃに基づき計算され補正係数として乗じた式［数３］で表されることが明らかになった。
［数３］
等価な繰返しせん断応力比（τｄ／σｚ’）
＝γｎ・αｍａｘ／ｇ・σｚ／σｚ’・γｄ・Ｆ（Ｌ）・Ｆ（Ｇ）・Ｆ（Ｈ）
【００１５】
上記［数３］について、各符号のγｎ、αｍａｘ、ｇ、σｚ、σｚ’は上述の［数１］と同じであるが、γｄは地盤が剛体でないことによる低減係数ではあるものの、その低減係数は、上記地震応答解析により（１−０．０３３Ｚ）（Ｚ：深度）となる。そして、Ｆ（Ｌ）は図２Ａに基づき、格子間隔（Ｌ）の影響度を表した補正係数を表す。
Ｆ（Ｇ）は図２Ｂに基づき、改良体の剛性（Ｇ）の影響度を表した補正係数を表す。
Ｆ（Ｈ）は図２Ｃに基づき、液状化層厚（Ｈ）の影響度を表した補正係数を表す。
【００１６】
図３Ａは、液状化層厚（Ｈ）＝１０ｍについて、前記［数３］により求めた格子間の原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布と、地震応答解析により求めた格子間の原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布とを比較したグラフを示している。
【００１７】
図３Ｂは、液状化層厚（Ｈ）＝１５ｍについて、前記［数３］により求めた格子間の原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布と、地震応答解析により求めた格子間の原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布とを比較したグラフを示している。
【００１８】
図３Ａ、Ｂから分かるとおり、両者はほど良い一致を示している。よって、格子間隔（Ｌ）の影響度、改良体の剛性（Ｇ）の影響度、液状化層厚（Ｈ）の影響度を考慮した上記［数３］は、格子間の原地盤に発生する最大せん断応力（τ_ＸＹ(max)）を精度良く算出していることが分かる。
【００１９】
即ち、請求項１に記載した発明に係る、深層混合処理工法による格子状改良地盤における液状化防止のための適正な格子間隔簡易算定法によれば、Ｎ値、細粒土含有率（％）など、上述した建築基礎構造設計指針による液状化発生に対する安全率Ｆι値を用いた液状化簡易判定法に必要な定数として、図２Ｂ、Ｃで明らかにされた改良体の剛性の補正係数Ｆ（Ｇ）と、液状化層厚の補正係数Ｆ（Ｈ）、及び格子間隔の補正係数Ｆ（Ｌ）を乗じて補正する上記[数３]を変形して、格子間隔（Ｌ）について解くことにより、格子状改良地盤の適正な格子間隔（Ｌ）を簡易に算定することができる。
【００２０】
以上のように、液状化防止のための格子状改良地盤の格子間隔（Ｌ）は、既知の建築基礎構造設計指針のＦι値を用いた液状化簡易判定法をベースに、地震応答解析結果により求めた改良体の格子間隔（Ｌ）と剛性（Ｇ）及び液状化層厚（Ｈ）の補正係数Ｆ（Ｌ）、Ｆ（Ｇ）及びＦ（Ｈ）を乗じて得られる上記[数３]を変形し、格子間隔（Ｌ）について解いた式により簡易に求めることができる。
【００２１】
ちなみに、格子状改良地盤の適正な格子間隔（Ｌ）ｍを求める際に必要な定数は、以下の９つである。
１）地震動のマグニチュード
２）地表面水平加速度
３）土の単位体積重量
４）Ｎ値
５）地下水位
６）細粒土含有率
７）液状化発生に対する安全率
８）改良体の剛性
９）液状化層厚
【００２２】
図４Ａ、Ｂはそれぞれ、液状化防止のために格子状改良地盤が適用された２つの建物について、請求項１の発明に係る格子間隔簡易算定法を用いた試算結果を示している。設計上の安全性を考慮して試算結果の最小値に着目すると、格子間隔は略８ｍである。動的解析に基づいた実施工もやはり８ｍであり、請求項１の発明による格子間隔簡易算定法の妥当性は明らかである。
【００２３】
【本発明の奏する効果】
請求項１に記載した発明に係る、深層混合処理工法による格子状改良地盤における液状化防止のための格子間隔簡易算定法によれば、建築基礎構造設計指針の安全率Ｆι値を用いた液状化簡易判定法をベースに、改良体の剛性（Ｇ）、液状化層厚（Ｈ）を加味した式を変形し、格子間隔（Ｌ）について解くことにより、液状化防止に適正な格子間隔（Ｌ）を簡易に精度良く算定することができる。
【００２４】
すなわち、本発明の格子間隔簡易算定法によれば、既知のＦι値を用いた液状化簡易判定法に必要な定数と、図２Ｂ、Ｃから今般明らかになった補正係数Ｆ（Ｇ），Ｆ（Ｈ）及びＦ（Ｌ）を乗ずる上記[数３]を変形し、格子間隔（Ｌ）について解くことにより、液状化防止に適正な格子間隔（Ｌ）を簡易に求めることができるので、特別の土質試験を行う必要は一切無く、高精度に格子間隔を求めることができる。
【図面の簡単な説明】
【図１】Ａは細粒土含有率と補正Ｎ値増分ΔＮ_ｆとの関係を表したグラフであり、Ｂは補正Ｎ値（Ｎ_ａ）と飽和土層の液状化抵抗比（τｌ／σｚ’）との関係を表したグラフである。
【図２】Ａは格子間隔（Ｌ）とその補正係数Ｆ（Ｌ）との関係を表したグラフであり、Ｂは改良体の剛性（Ｇ）とその補正係数Ｆ（Ｇ）との関係を表したグラフであり、Ｃは液状化層厚（Ｈ）とその補正係数Ｆ（Ｈ）との関係を表したグラフである。
【図３】Ａは液状化層厚（Ｈ）＝１０ｍについて、本発明に係る格子間隔簡易算定法により求めた格子間原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布と、地震応答解析により求めた格子間原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布とを比較したグラフを示している。
Ｂは液状化層厚（Ｈ）＝１５ｍについて、本発明に係る格子間隔簡易算定法により求めた格子間原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布と、地震応答解析により求めた格子間原地盤に発生する最大せん断応力（τ_ＸＹ(max)）の深度方向分布とを比較したグラフを示している。
【図４】Ａ、Ｂはそれぞれ、液状化防止のために格子状改良地盤が適用された２つの建物について、本発明に係る格子間隔簡易算定法を用いた試算結果を示している。[0001]
BACKGROUND OF THE INVENTION
In order to prevent liquefaction of ground (sandy ground) that is easily liquefied during an earthquake, this invention is a simple calculation of the lattice spacing that is used to easily calculate the appropriate lattice spacing when the ground is improved into a lattice using the deep mixing method. It belongs to the technical field of law.
[0002]
[Prior art]
Various techniques for preventing the liquefaction of the ground by forming solidified improvement walls in a grid shape in the ground (sandy ground) that easily liquefies during an earthquake are disclosed in, for example, Japanese Patent No. 1930164, Japanese Patent No. 2131070, etc. ing.
[0003]
However, the technology that has been researched and developed on what kind of lattice is effective and economical in size is disclosed in Japanese Patent No. 2568115.
[0004]
By the way, as a method for easily determining the liquefaction of the ground, a method using an Fι value as a safety factor against occurrence of liquefaction is already known (Guideline for Designing Building Foundations).
[0005]
[Problems to be solved by the present invention]
Although the technology for calculating the appropriate lattice spacing based on the simple liquefaction determination method using the Fι value can be expected to make a further leap forward with higher accuracy than the conventional calculation method, it has not been developed yet. It is.
[0006]
The object of the present invention is to provide a deep mixing method that can easily and accurately calculate the appropriate lattice spacing based on the liquefaction simple determination method using the Fι value and taking into account the rigidity of the improved body and the liquefied layer thickness. The object is to provide a simple method for calculating the lattice spacing to prevent liquefaction in the improved ground with a treatment method.
[0007]
[Means for Solving the Problems]
As a means for solving the problems of the prior art, according to the invention described in claim 1, a simple calculation method of a lattice interval for preventing liquefaction in a lattice improved ground by a deep mixing treatment method is as follows:
A method for simple calculate the proper lattice spacing liquefaction prevention when construct a lattice-like ground improved by Deep Mixing Method liquefaction easily ground during an earthquake,
Study depth liquefaction resistance ratio in the earth board (τl / σz ') a cyclic shear stress ratio applied during an earthquake along with the finding (τd / σz') the determined, the ratio of the two (τl / σz ') / ( τd / in liquefaction simple determination method for determining a safety factor Fι values for liquefaction taking σz '),
The repeated shear stress ratio for (τd / σz '), the correction factor F representing the degree of influence of the correction coefficient representing the degree of influence of the lattice interval based on the seismic response analysis (L) F (L), the rigidity of the improvement body (G) (G), and from solving a modified lattice distance correction coefficient F (H) to correct by multiplying each equation representing the degree of influence of the liquid layer thickness (H) (L), appropriateness of the lattice-shaped improved ground It is characterized in that a simple lattice interval (L) is calculated.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention described in claim 1 is a method to calculate the proper lattice spacing liquefaction prevention when construct a more grid improved ground in Deep Mixing Method liquefaction easily ground during an earthquake easily.
Study depth liquefaction resistance ratio in the earth board (τl / σz ') a cyclic shear stress ratio applied during an earthquake along with the finding (τd / σz') the determined, the ratio of the two (τl / σz ') / ( τd / In the simple liquefaction determination method for obtaining the safety factor Fι value for liquefaction by taking σz ′)
Regarding the repeated shear stress ratio, a correction coefficient F (L) representing the influence of the lattice spacing (L) based on the seismic response analysis, a correction coefficient F (G) representing the influence of the rigidity (G) of the improved body, and liquid The appropriate lattice interval (L) of the grid-like improved ground is obtained by modifying the equation for correction by multiplying the correction coefficient F (H) representing the influence of the layer thickness (H) and solving for the lattice interval (L) . Calculate.
[00 09 ]
According to the architectural foundation structure design guideline, the outline of the liquefaction simple determination using the Fι value is as described below.
[00 10 ]
(1) The repeated shear stress ratio (τd / σz ′) is obtained as in the following [ Equation 1] .
[Equation 1]
τd / σz ′ = γn · αmax / g · σz / σz ′ · γd
Regarding the above [Equation 1], the meaning of each symbol is as follows.
τd: Equivalent constant cyclic shear stress amplitude (t / m ² ) generated in the horizontal plane
σz ': Effective earth cover pressure at the examination depth (vertical effective stress) (t / m ² )
γn: correction coefficient for the equivalent number of repetitions, γn = 0.1 (M−1).
Where M is the magnitude of the earthquake αmax: horizontal acceleration for design on the ground surface (Gal)
g: Gravity acceleration (980Gal)
σz: Total soil covering pressure (vertical total stress) at study depth (t / m ² )
γd: a reduction factor due to the fact that the ground is not rigid (1-0.015z).
z represents the depth from the ground surface expressed in meters .
[00 11 ]
(2) The liquefaction resistance ratio (τl / σz ′) is obtained.
Where τl is the liquefaction resistance in the horizontal section.
The liquefaction resistance ratio (τl / σz ′) is obtained based on the following [ Equation 2] and FIGS. 1A and 1B.
[Equation 2]
N _a = N ₁ + ΔN _f
N ₁ = C _N · N
C _N = √10 / σz ′
Each code meanings are as follows for definitive in the [Equation 2].
N _a : Correction N value N ₁ : Conversion N value ΔN _f : Correction N value increment according to fine grain soil content, according to FIG. 1A.
C _N : Coefficient of converted N value N: Measured N value by the tomb method or automatic drop method [00 12 ]
The liquefaction resistance ratio (τl / σz ′) with respect to the corrected N value (N _a ) is obtained using the 5% shear strain amplitude curve in FIG. 1B.
Then, the safety factor (Fι) is obtained by the liquefaction resistance ratio (τl / σz ′) / repeated shear stress ratio (τd / σz ′). If the value of the safety factor (Fι) is 1 or less, it is liquefied. determines not to liquefaction greater than 1 (above is the outline of the liquefaction simple determination using the Fι value.).
[00 13 ]
Incidentally, the present inventors, in the invention described in claim 1, when construct a liquefaction easily ground Ri by the Deep Mixing Method lattice improved ground during an earthquake, occur in the original ground interstitial The equivalent cyclic shear stress ratio is considered to be affected by the lattice spacing (L), the rigidity of the improved body (G), the liquefaction layer thickness (H), and the input seismic wave. Analysis parametric study) (see FIGS. 2A, B, C).
[00 14 ]
As a result, the equivalent cyclic shear stress ratio (τd / σz ′) generated in the original ground between the lattices is calculated based on the external force evaluation formula of the building foundation structure design guideline. It is clear that the degree of influence of the improved body rigidity (G) and the degree of influence of the liquefied layer thickness (H) are expressed by the formula [Equation 3] calculated based on FIGS. Became.
[Equation 3]
Equivalent cyclic shear stress ratio (τd / σz ′)
= Γn · αmax / g · σz / σz '· γd · F (L) · F (G) · F (H)
[00 15 ]
For the equation (3), each code of γn, αmax, g, σz, σz ' is the same as Expression 1 described above, although γd is the reduction factor due to ground is not rigid, the reduction factor Is (1-0.033Z) (Z: depth) by the earthquake response analysis. Then, F (L) is based on FIG. 2A, represents the correction coefficient representing the degree of influence of the lattice spacing (L).
F (G) is based on Figure 2B, it represents a correction coefficient representing the degree of influence of the stiffness of the improved body (G).
F (H) is based on Figure 2C, represents a correction coefficient representing the influence of the liquid layer thickness (H).
[00 16 ]
FIG. 3A shows the depth direction distribution of the maximum shear stress (τ _{XY (max)} ) generated in the original ground between the lattices obtained by [Equation 3] and the seismic response analysis for the liquefied layer thickness (H) = 10 m. The graph which compared with the depth direction distribution of the maximum shear stress ((tau _{) XY (max)} ) which generate | occur | produces in the raw ground between the grating | lattices calculated | required by ₍₃₎ is shown.
[00 17 ]
3B shows the depth direction distribution of the maximum shear stress (τ _{XY (max)} ) generated in the original ground between the lattices obtained by [Equation 3] and the seismic response analysis for the liquefied layer thickness (H) = 15 m. The graph which compared with the depth direction distribution of the maximum shear stress ((tau _{) XY (max)} ) which generate | occur | produces in the raw ground between the grating | lattices calculated | required by ₍₃₎ is shown.
[00 18 ]
As can be seen from FIGS. 3A and 3B, both show a good match . Thus, the influence of the lattice spacing (L), the influence of the stiffness of the improved body (G), SL on considering the influence of the liquid layer thickness (H) [Equation 3] is generated in the original ground interstitial It can be seen that the maximum shear stress (τ _{XY (max)} ) to be calculated is accurately calculated.
[00 19 ]
That is, according to the invention described in claim 1, according to the appropriate simple lattice spacing calculation method for preventing liquefaction in the lattice improved ground by the deep mixing method, N value, fine soil content (%) etc., as a constant necessary for the liquefaction simplified determination method using the safety factor Fι values for liquefaction caused by building infrastructure design guidelines described above, FIG. 2B, the correction coefficient of stiffness of the revealed improved body C F ( G) is multiplied by the correction coefficient F (H) of the liquefied layer thickness and the correction coefficient F (L) of the lattice spacing, and the above [Equation 3] is modified to solve the lattice spacing (L). It is possible to easily calculate an appropriate lattice interval ( L) of the lattice-shaped improved ground.
[00 20 ]
As described above, the lattice spacing of the lattice-shaped improved ground for liquefaction prevention (L) is liquefaction simplified determination method using Fι values of known building substructure design guideline to base, the seismic response analysis results The above-mentioned [Equation 3] obtained by multiplying the correction factor F (L) , F (G), and F (H) of the lattice spacing (L), rigidity (G), and liquefied layer thickness (H) of the improved body obtained more. ] Can be easily obtained by the equation solved for the lattice spacing (L) .
[00 21 ]
By the way, the following nine constants are necessary for obtaining an appropriate lattice interval (L) m of the lattice-shaped improved ground.
1) Magnitude of ground motion 2) Ground surface acceleration 3) Unit volume weight of soil 4) N value 5) Groundwater level 6) Fine soil content 7) Safety factor against liquefaction occurrence 8) Stiffness of improved body 9) Liquid Layer thickness [00 22 ]
4A and 4B respectively show the trial calculation results using the lattice interval simple calculation method according to the invention of claim 1 for two buildings to which a grid-like improved ground is applied to prevent liquefaction. When attention is paid to the minimum value of the trial calculation result in consideration of design safety, the lattice spacing is about 8 m. Actual construction based on dynamic analysis is also still 8m, it is clear the validity of the lattice spacing Simple Calculation Method according to the invention of claim 1.
[00 23 ]
[Effects of the present invention]
According to the invention described in claim 1, liquefaction using the safety factor Fι value of the building foundation structure design guideline according to the grid interval simple calculation method for preventing liquefaction in the grid improvement ground by the deep mixed processing method based on simple determination method, a modification of the rigidity of the improvement body (G), in consideration liquefied layer thickness a (H) wherein, by solving the lattice spacing (L), the proper lattice spacing liquefaction prevention ( L) can be easily and accurately calculated.
[00 24 ]
That is, according to the simple lattice spacing calculation method of the present invention, the constants necessary for the simple liquefaction determination method using the known Fι value and the correction coefficients F (G), F that have now been clarified from FIGS. Since the above [Equation 3] multiplied by (H) and F (L) is modified and the lattice spacing (L) is solved , an appropriate lattice spacing (L) for preventing liquefaction can be easily obtained. There is no need to perform any soil tests, and the lattice spacing can be obtained with high accuracy.
[Brief description of the drawings]
FIG. 1A is a graph showing the relationship between fine grain content and corrected N value increment ΔN _{f, and} B is corrected N value (N _a ) and liquefaction resistance ratio of saturated soil layer (τl / σz). It is a graph showing the relationship with ').
FIG. 2A is a graph showing the relationship between the lattice spacing (L) and its correction coefficient F (L), and B is the relationship between the rigidity (G) of the improved body and its correction coefficient F (G). C is a graph showing the relationship between the liquefied layer thickness (H) and its correction coefficient F (H).
FIG. 3A shows the depth distribution of the maximum shear stress (τ _{XY (max)} ) generated in the interstitial ground obtained by the simple method for calculating the lattice spacing according to the present invention for liquefaction layer thickness (H) = 10 m. And a graph comparing the depth direction distribution of the maximum shear stress (τ _{XY (max)} ) generated in the interstitial ground obtained by seismic response analysis.
B shows the depth direction distribution of the maximum shear stress (τ _{XY (max)} ) generated in the interstitial ground obtained by the simple method for calculating the lattice spacing according to the present invention and the seismic response for the liquefied layer thickness (H) = 15 m. The graph which compared with the depth direction distribution of the maximum shear stress (τXY _(max) ) which generate | occur | produces in the interstitial raw ground calculated | required by analysis is shown.
FIGS. 4A and 4B show the results of trial calculations using the grid interval simple calculation method according to the present invention for two buildings to which a grid-like improved ground is applied in order to prevent liquefaction.

Claims

A method for simple calculate the proper lattice spacing liquefaction prevention when construct a lattice-like ground improved by Deep Mixing Method liquefaction easily ground during an earthquake,
Study depth liquefaction resistance ratio in the earth board (τl / σz ') a cyclic shear stress ratio applied during an earthquake along with the finding (τd / σz') the determined, the ratio of the two (τl / σz ') / ( τd / in liquefaction simple determination method for determining a safety factor Fι values for liquefaction taking σz '),
The repeated shear stress ratio for (τd / σz '), the correction factor F representing the degree of influence of the correction coefficient representing the degree of influence of the lattice interval based on the seismic response analysis (L) F (L), the rigidity of the improvement body (G) (G), and from solving a modified lattice distance correction coefficient F (H) to correct by multiplying each equation representing the degree of influence of the liquid layer thickness (H) (L), appropriateness of the lattice-shaped improved ground A simple lattice spacing calculation method for preventing liquefaction in a grid-like improved ground by a deep mixing treatment method, characterized by calculating a simple lattice spacing (L) .