JPS58127823A

JPS58127823A - Liquefaction preventive structure of foundation ground

Info

Publication number: JPS58127823A
Application number: JP1048782A
Authority: JP
Inventors: Sadao Yabuuchi; 薮内　貞男; Kingo Asayama; 浅山　金吾
Original assignee: Takechi Koumusho KK
Current assignee: Takechi Koumusho KK
Priority date: 1982-01-25
Filing date: 1982-01-25
Publication date: 1983-07-30

Abstract

PURPOSE:To prevent the liquefaction of foundation ground by avoiding the generation of excessive void water pressures at the time of earthquake by driving a given number of drain pillars consisting of a reinforced water-permeable concrete pipe and a water-permeable wall into the foundation ground. CONSTITUTION:In a foundation ground B to support a structure A on the earth's surface, pits 11 are drilled in given places surround foundation piles 4 and then water-permeable concrete pipes 1 reinforced with iron bars 5 are set. Then, water-permeable wall-forming materials 12, e.g., gravel, fine stones, slags, etc., are charged into the apertures between the reinforced water-permeable concrete pipes 1 and the pits 11 to form a water-permeable wall 2 in order to build drain pillars 3. By this, excessive void water pressures to be generated at the time of earthquake are dissipated into the foundation ground B and the liquefaction of the foundation ground B and the surrounding ground of the foundation piles 4 can be prevented.

Description

【発明の詳細な説明】本発明は液状化し易い砂地盤を改良し、地震時にも安全
な基礎地盤を造築するための基礎地盤の液状化防止構造
に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquefaction prevention structure for foundation ground for improving sandy ground that is easily liquefied and for constructing a foundation ground that is safe even in the event of an earthquake.

地震時に砂地盤が液状化し、地盤としての支持力を失な
・い、構築物が沈下、倒壊した例は既に多く知られてい
る。上記液状化の原因は、地震時に砂地盤に過剰間隙水
圧が発生して地盤の支持力を失わしめるものとされてお
り、一般には砂地盤の相対密度を上げること（Ｎ値を上
げること）あるいは液状化し鰐い粒径の砂に置き換える
ことの目的から、コンボーザー工法、バイブロ工法等に
より砂杭を打設し、地盤を改良する方法が一般に行なわ
れている。There are already many known cases where sandy ground liquefies during an earthquake and loses its supporting capacity, resulting in buildings sinking and collapsing. The cause of the liquefaction mentioned above is said to be that excessive pore water pressure is generated in the sandy ground during an earthquake, causing the ground to lose its bearing capacity.In general, it is said that increasing the relative density of the sandy ground (increasing the N value) or For the purpose of replacing sand with liquefied sand having a large grain size, sand piles are driven using the convoser method, vibro method, etc. to improve the ground.

本発明では、液状化の主因である過剰間隙水圧の発生に
着目し、この発生を防止することにより砂地盤の液状化
を防止しようとするもので、液状化の虞れのある砂地盤
に透水コンクリート柱と砂利、細石、鉱滓等による透水
壁とからなる透水性のよいドレーン柱を打設し、該ドレ
ーン柱の透水性の高いことを利用して地震時の過剰間隙
水圧の発生を防止し、消散しようとする基礎）であれ杭
基礎であれ、基礎地盤による支持方により支えられてい
るが、地震時には液状化の虞れのある砂地盤では同地盤
が液状化し、基礎地盤の支持力、基礎杭の支持力を失わ
しめることになる。The present invention focuses on the generation of excess pore water pressure, which is the main cause of liquefaction, and attempts to prevent liquefaction of sandy ground by preventing this generation. A highly permeable drain pillar consisting of a concrete pillar and a permeable wall made of gravel, fine stone, slag, etc. is installed, and the high permeability of the drain pillar is used to prevent the generation of excessive pore water pressure during an earthquake. Whether it is a foundation that is about to dissipate) or a pile foundation, it is supported by the support method of the foundation ground, but in the case of sandy ground that is likely to liquefy in the event of an earthquake, the same ground will liquefy, and the bearing capacity of the foundation ground, This will cause the foundation piles to lose their bearing capacity.

そこで、本発明では、構築物を支える基礎地盤を液状化
から防止するために、ポーラスな透水コンクリート柱の
周囲ｌこ砂利、細石、鉱滓その他による透水壁を設けて
なるドレーン柱を基礎地盤内に所定数打設し、地震時に
発生する過剰間隙水圧を消散させることｌこより基礎地
盤の液状化及び基礎杭周囲地盤の液状化を防止し、構築
物の安全を図るようにしたことを特徴とするものである
。Therefore, in the present invention, in order to prevent the foundation ground supporting the structure from liquefaction, a drain pillar is provided in the foundation ground, which is made of a porous water-permeable concrete pillar with a water-permeable wall made of gravel, fine stone, slag, etc. It is characterized by the fact that it is designed to dissipate excess pore water pressure that occurs during an earthquake by placing several piles, thereby preventing liquefaction of the foundation ground and the ground around the foundation piles, thereby ensuring the safety of the structure. be.

なお、透水コンクリート柱とは、例えば骨材の粒度配列
を一定にし骨材の表面にうすいセメントペーストの膜を
つくり骨材と骨材を直接結合させ、全体的に各紙の微小
な空隙を作り固めたポーラスなコンクリート柱をいう。In addition, permeable concrete columns are made by, for example, making the particle size arrangement of the aggregate constant, creating a thin film of cement paste on the surface of the aggregate, directly bonding the aggregates, and creating minute voids in each paper throughout to harden it. A porous concrete column.

次に本発明の具体的実施態様を図面に基き説明する。Next, specific embodiments of the present invention will be described based on the drawings.

実施例（Ｉ）第１図および第２図は、基礎型式が杭を用いる杭基礎に
おける実施例を示しており、地上構築物（Ａ）を支える
基礎地盤（Ｂ）内において、透水コンクリート柱（１）
とその周囲の砂利、細石、鉱滓等による透水壁（２）と
からなるドレーン柱（３）を基礎杭（４）を囲むように
基礎杭周辺に打設している。このドレーン柱（３）は地
表もしくは地表近傍から液状化層（Ｂ′）内の低部にま
で達するように打設しである。この実施例において、ド
レーン柱（３）を基礎杭（４）の打設部分を除いて散在
状に打設することもできる。Example (I) Figures 1 and 2 show examples of pile foundations in which the foundation type is piles, in which permeable concrete columns (1 )
A drain column (3) consisting of a permeable wall (2) made of surrounding gravel, fine stones, slag, etc., is driven around the foundation pile so as to surround the foundation pile (4). This drain pillar (3) is installed so as to reach from the ground surface or near the ground surface to the lower part of the liquefaction layer (B'). In this embodiment, the drain columns (3) can also be driven in a scattered manner except for the areas where the foundation piles (4) are driven.

実施例［、ｎ）第３図および第４図は、基礎型式が杭を用いない直接基
礎における実施例を示し、構築物（Ａ）を支える基礎地
盤（Ｂ）内において、上記実施例ＣＩ）と同様のドレー
ン柱（３）を謔ｉ隔の散在状もしくは列状に配して打設
している。Example [, n) Figures 3 and 4 show an example in which the foundation type is a direct foundation that does not use piles, and in the foundation ground (B) that supports the structure (A), the above Example CI) and Similar drain pillars (3) are installed in a scattered manner or in rows at even intervals.

上記ドレーン柱（３）の造成は、第５図〜第７図に示す
ようにして行な、う。先ず、構築物を構築する基礎地盤
内において、液状化の虞れのある砂地盤をアースオーガ
ー〇〇等により後述する透水コンクリート柱（１）の径
より数１００１１程度大きい所定径で掘孔する（第５図
）。そして前記掘孔ａ１１内に透水コンクリート柱（１
）を吊下、設置する（第６図）。この透水コンクリート
柱（１）は長さ方向に一体（一本もの）でなくてもよく
、単体の場合は順次継足して吊下、設置すればよい。The drain pillar (3) is constructed as shown in FIGS. 5 to 7. First, in the foundation ground on which the structure will be constructed, a hole is dug in the sandy ground that is at risk of liquefaction using an earth auger 〇〇, etc., to a predetermined diameter approximately several 10011 times larger than the diameter of the permeable concrete column (1), which will be described later. Figure 5). Then, a permeable concrete column (1
) is hung and installed (Figure 6). This permeable concrete column (1) does not have to be integral (one piece) in the length direction; in the case of a single piece, it is sufficient to add them one by one and suspend and install them.

こうして設置された透水コンクリート柱（１）と孔壁つ
まりその周囲地盤との間隙に砂利、細石、鉱滓その他の
透水壁造成用の材料０りを投入充填し、透水コンクリー
ト柱（１）の周囲に透水壁（２）を造成する（第７図）
。The gap between the permeable concrete column (1) installed in this way and the hole wall, that is, the surrounding ground, is filled with gravel, fine stones, slag, and other materials for constructing a permeable wall, and the area around the permeable concrete column (1) is filled. Create a permeable wall (2) (Figure 7)
.

上記ドレーン柱（３）の造成における砂利等の投入方法
としては、第８図に示すように一重もしくは二重のケー
シング口３を透水コンクリート柱（１）を包囲するよう
にバイブロＩａ（Ｉ４１等で吊下、設置し、ケーシング
（１３１の引上げ時にケーシングＯＪ上部に設けた投入
口０５）より砂利、細石、鉱滓等を投入し、透水コンク
リ、−ト柱（１）の周囲に透水壁（２）を造成すること
ができる。As shown in Fig. 8, the method of introducing gravel, etc. in constructing the drain pillar (3) is as shown in Fig. 8. After suspending and installing the casing, pour gravel, fine stones, slag, etc. into the casing (input port 05 provided at the top of the casing OJ when pulling up 131), and fill with permeable concrete and create a permeable wall (2) around the column (1). can be created.

本発明は、上記の構成によりなるものであって、構築物
を支える基礎地盤内に透水コンクリート柱とその周囲の
砂利等による透水壁とからなる透水性のよいドレーン柱
か打設されているため、急上昇する過剰間隙水圧の発生
そのものを防止でき、基礎地盤の液状化を防止できる等
、下記のごとき優れた作用効果を奏することかできる。The present invention has the above-mentioned configuration, and a drain pillar with good water permeability consisting of a water-permeable concrete pillar and a water-permeable wall made of gravel, etc. around the pillar is cast in the foundation ground supporting the structure. It is possible to prevent the generation of excessive pore water pressure that increases rapidly, and to prevent liquefaction of the foundation ground, and the following excellent effects can be achieved.

■　従来方法における砂地盤の締め固めあるいは置き換
えによる液状化防止の方法では、地震の強度により液状
化の危惧を残すが、本奢関門では、間隙水圧の上昇つま
り過剰間隙水圧の発生を防止する工法によるものである
から、地震時においても、その強弱に拘らず液状化の虞
れが全くなく、構築物は全く安全である。■ Conventional methods of preventing liquefaction by compacting or replacing sandy ground leave a risk of liquefaction due to the strength of an earthquake, but Honju Kanmon uses a construction method that prevents the rise in pore water pressure, that is, the generation of excessive pore water pressure. Therefore, even in the event of an earthquake, regardless of its strength, there is no risk of liquefaction, and the structure is completely safe.

■　上記過剰間隙水圧の発生を防止する方法として、砂
利、細石等のみによりドレーン柱を基礎地盤に造成する
方法もあるが、これに比べ、本発明では、芯材に透水コ
ンクリート柱を用い、その周囲に砂利、細石、鉱滓等に
よる透水壁を造成したドレーン柱よりなるものであるか
ら、施工不備による砂利柱不連続がなく、均一な透水層
を透水コンクリート柱で確保でき、特に繰返し地震を受
けた場合、砂利柱のみでは型が崩れる虞れがあるが、本
発明ではドレーン柱としての型及び透水層を良好に保持
でき、地震による液状化を長期に亘り防止する構造とし
て最適である。なお、透て補強すれば、前記保持効果が
より良好である。■ As a method for preventing the generation of excessive pore water pressure, there is a method of constructing drain columns on the foundation ground using only gravel, fine stones, etc. However, in contrast to this, in the present invention, a permeable concrete column is used as the core material. Since the drain pillar is constructed with a permeable wall made of gravel, fine stone, ore slag, etc. around the drain pillar, there is no discontinuity of the gravel pillar due to construction defects, and a uniform permeable layer can be ensured with the permeable concrete pillar, which is especially effective against repeated earthquakes. In such a case, there is a risk that the shape of the gravel column will collapse if only the gravel column is used, but the present invention can maintain the shape of the drain column and the water permeable layer well, making it an optimal structure for preventing liquefaction caused by earthquakes over a long period of time. In addition, the above-mentioned holding effect will be better if the reinforcement is transparent.

■　透水コンクリート柱の持つ均一性、耐久性および強
靭な透水性と、砂利、細石等の良好な透水性とを併せ持
つドレーン柱が造成でき、地震時にも構築物を安全強固
に支える基礎地盤が造成できる。■ Drain columns can be created that combine the uniformity, durability, and strong water permeability of permeable concrete columns with the good water permeability of gravel, fine stones, etc., and the foundation ground can be created to safely and firmly support structures even in the event of an earthquake. .

【図面の簡単な説明】[Brief explanation of the drawing]

図は本発明の実施例を示すものであり、第１図は杭基礎
におけるｌ実施例を示す略示平面図、第２図は前回■−
■線における縦断面図、第３図は杭を用いない直接基礎
における実施例を示す略示平面図、第４図は前回ＩＶ−
ＩＶ線における縦断面図、第５図〜第７．図［ａ）はド
レーン柱の造成方法を例示する縦断面図、第７図（ｂｌ
は造成されたドレーン柱の平面図、第８図は砂利、細石
等の投入方法を例示する縦断面図である。（Ａ）・・・構築物、（Ｂ）・・・基礎地盤、（Ｂ′）
・・・液状化層、（１）・・・透水コンクリート柱、釦
・・・透水壁、Ｌ３）・・・ドレーン柱、（４）・・・
基礎杭。特許出願人　株式会社武智工務所第２図第１図／第４図ご □□ 第：３図、／第７図（１））（ａ）第８４／Ｊ′５フ一、１３ −７７１ｌ１２図The figures show an embodiment of the present invention. Fig. 1 is a schematic plan view showing an embodiment of the present invention in a pile foundation, and Fig. 2 is a schematic plan view showing an embodiment of the present invention.
■Longitudinal cross-sectional view along the line, Figure 3 is a schematic plan view showing an example of a direct foundation without using piles, Figure 4 is the previous IV-
Longitudinal cross-sectional views along line IV, FIGS. 5 to 7. Figure [a] is a vertical cross-sectional view illustrating the method of constructing a drain pillar, and Figure 7 (bl
8 is a plan view of the constructed drain pillar, and FIG. 8 is a vertical cross-sectional view illustrating a method of introducing gravel, fine stones, etc. (A)...Structure, (B)...Foundation ground, (B')
...Liquification layer, (1)...Water-permeable concrete column, button...Water-permeable wall, L3)...Drain column, (4)...
Foundation pile. Patent Applicant: Takechi Construction Co., Ltd. Figure 2 Figure 1 / Figure 4 □□ Figure 3, / Figure 7 (1)) (a) No. 8 4 /J'5 Fuichi, 13-771 l 12 Figure

Claims

【特許請求の範囲】１、構築物を支える基礎地盤内に、透水コンクリート柱
の周囲に砂利、細石、鉱滓その他の材料による透水壁を
造成したドレーン柱を所定数打設してなることを特徴と
する基礎地盤の液状化防止構造。２、　ドレーン柱が基礎杭を囲むように基礎杭周辺に打
設された特許請求の範囲第１項記載の基礎地盤の液状化
防止構造。[Scope of Claims] 1. A predetermined number of drain pillars with permeable walls made of gravel, fine stone, slag, or other materials are cast around permeable concrete pillars in the foundation ground that supports the structure. A structure to prevent liquefaction of the foundation ground. 2. The foundation ground liquefaction prevention structure according to claim 1, wherein the drain pillar is driven around the foundation pile so as to surround the foundation pile.