JP4712456B2 - Foundation reinforcement method - Google Patents

Foundation reinforcement method Download PDF

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JP4712456B2
JP4712456B2 JP2005191089A JP2005191089A JP4712456B2 JP 4712456 B2 JP4712456 B2 JP 4712456B2 JP 2005191089 A JP2005191089 A JP 2005191089A JP 2005191089 A JP2005191089 A JP 2005191089A JP 4712456 B2 JP4712456 B2 JP 4712456B2
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foundation
reinforcing
pile
steel pipe
grout
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JP2007009505A (en
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金次 今井
孝芳 伊藤
孝栄 山本
浩二 八代
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太洋基礎工業株式会社
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Description

本発明は、既設構造物の基礎を補強する基礎補強工法に関する。   The present invention relates to a foundation reinforcing method for reinforcing a foundation of an existing structure.

既存の構造物などの基礎を補強する補強方法として、既設基礎の外周部からボーリングマシンで注入孔を掘削し、注入管を設置して水ガラス系などの薬液を注入することで既設杭周辺の地盤を強化する薬液注入工法や、部分的に高圧噴射攪拌工法により既設杭の周辺に拘束固化体を構築する方法などが知られている（例えば、特許文献１など）。   As a reinforcement method to reinforce the foundations of existing structures, etc., drilling the injection hole from the outer periphery of the existing foundation with a boring machine, installing the injection pipe and injecting chemicals such as water glass system around the existing pile A chemical solution injection method for strengthening the ground, a method for constructing a constrained solidified body around an existing pile by a high-pressure jet agitation method, etc. are known (for example, Patent Document 1).

しかし、上記の薬液注入工法では地盤の強化しか実現できず、信頼性の高い均一な地盤強化は期待できなかった。また、既設杭の周辺に拘束固化体を構築する方法では、既設基礎周辺のスペースや地形などの施工条件によっては有効な拘束固化体を構築できない場合があるといった問題があった。
特開２００３−１５５７５２号公報 However, the chemical solution injection method described above can only strengthen the ground, and a reliable and uniform ground reinforcement could not be expected. Moreover, in the method of constructing a constrained solidified body around an existing pile, there is a problem that an effective confined solidified body may not be constructed depending on construction conditions such as the space around the existing foundation and the topography.
JP 2003-155752 A

本発明は、上記従来の問題点を解決するためになされたものであって、その課題は、既設構造物の基礎の耐力増強と液状化防止とを同時に達成できる基礎補強工法を提供することである。   The present invention has been made in order to solve the above-described conventional problems, and the problem is to provide a foundation reinforcing method capable of simultaneously achieving the strength improvement of the foundation of the existing structure and the prevention of liquefaction. is there.

本発明の基礎補強工法は、既設基礎の直下にグラウトを注入する注入管兼用の鋼管杭を既設基礎を支圧体として圧入設置する工法であり、以下の工程に沿って施工する。   The foundation reinforcement construction method of the present invention is a construction method in which a steel pipe pile that also serves as an injection pipe for injecting grout directly under an existing foundation is press-fitted and installed using the existing foundation as a supporting body, and is constructed according to the following steps.

すなわち、本発明の基礎補強工法は、既設基礎の直下に鋼管からなる補強杭を土中に圧入する作業空間を掘削形成する掘削工程と、既設基礎の底面を支圧面として補強杭を圧入する補強杭圧入工程と、補強杭の中空部を介して地盤中にグラウトを注入するグラウト注入工程と、既設基礎の底面を支持する支持部材を補強杭に接合する支持部材接合工程と、掘削した作業空間に既設基礎を補強する補強基礎を形成して埋め戻す埋戻し工程とからなる。そして補強杭は、グラウトを周辺地盤へ注入するグラウト注入孔を備える注入鋼管と一般鋼管とが継ぎ足されてなり、グラウト注入孔には注入鋼管の中空部に挿設され補強杭の外部で開口するグラウト注入路が連通されていることを特徴とする。 That is, the foundation reinforcing method of the present invention includes a excavation process for excavating and forming a work space in which a reinforcing pile made of a steel pipe is press-fitted into the soil immediately below the existing foundation, and a reinforcement in which the reinforcing pile is press-fitted with the bottom surface of the existing foundation as a bearing surface. Pile press-in process, grout injection process for injecting grout into the ground through the hollow part of the reinforcing pile, support member joining process for joining the support member supporting the bottom of the existing foundation to the reinforcement pile, and excavated work space And a backfilling process in which a reinforcing foundation for reinforcing an existing foundation is formed and backfilled. The reinforcing pile is made is foot joint and the injection steel pipe generally steel pipe with a grouting hole for injecting grout into the surrounding ground, the grout injection hole is inserted into the hollow portion of the injection steel pipe opening outside the reinforcing pile grout injection path which is characterized that you have communicated.

また、本発明の基礎補強工法において、グラウト注入孔は、鋼管の側部に軸心から放射状に穿設されていることが望ましく、また、注入鋼管の先端部外周にはパッカーリングが固着されていることが好ましい。 Further, in the basic reinforcing method of the present invention, it is desirable that the grout injection holes are formed radially from the axial center in the side portion of the steel pipe, and the packer ring is fixed to the outer periphery of the tip end portion of the injection steel pipe. Preferably it is.

本発明の基礎補強工法においては、既設杭に隣接して補強杭を設置することができる。   In the foundation reinforcing method of the present invention, the reinforcing pile can be installed adjacent to the existing pile.

本発明の基礎補強工法によれば、既設基礎の直下に補強杭を設置することができるので、既設基礎の支持力を増大することができる。また、補強杭は、グラウトの注入孔を穿設した注入鋼管と注入孔のない一般鋼管とが適宜に継ぎ足されてなるので、地盤の任意の深度に効果的にグラウトを注入することができる。さらに、グラウト注入孔には注入鋼管の中空部に挿設され補強杭の外部で開口するグラウト注入路が連通されているので、注入路毎にグラウト材の種類を変更することが可能であり、各グラウト注入孔の周辺地盤の性状によって好適なグラウト材を選択することができる。そして、的確に補強杭の周辺地盤にグラウトの注入固結部を形成することができる。従って、補強杭の周辺地盤を強化できるとともに、補強杭の摩擦抵抗を増大して補強杭の既設基礎に対する支持力をより大きなものとすることができる。 According to the foundation reinforcing method of the present invention, the reinforcing pile can be installed directly under the existing foundation, so that the supporting force of the existing foundation can be increased. In addition, the reinforcing pile is formed by appropriately adding an injection steel pipe having a grout injection hole and a general steel pipe without an injection hole, so that the grout can be effectively injected at an arbitrary depth of the ground. Furthermore, since the grout injection hole is inserted into the hollow portion of the injection steel pipe and communicated with the grout injection path opened outside the reinforcing pile, the type of grout material can be changed for each injection path. A suitable grout material can be selected depending on the properties of the ground around each grout injection hole. And it is possible to accurately form an injection-consolidated portion of grout on the ground surrounding the reinforcing pile. Therefore, the ground around the reinforcing pile can be strengthened, and the frictional resistance of the reinforcing pile can be increased, so that the supporting force for the existing foundation of the reinforcing pile can be increased.

また、このような補強杭は既設基礎を支圧体として所定長さの鋼管を継ぎ足しながら圧入することで形成できる。従って、掘削形成する作業空間は小規模なものでよく、工期短縮とコスト低減が可能となる。 In addition, such a reinforcing pile can be formed by press-fitting a steel pipe having a predetermined length with the existing foundation as a supporting body. Therefore, the work space for excavation formation may be small, and the construction period can be shortened and the cost can be reduced .

さらに、補強杭を既設杭に隣接して設置することで、既設杭の周辺地盤を改良強化することができ、既設杭の座屈防止（耐震強化）を図るとともに既設杭の支持力を増大することが可能となる。   Furthermore, by installing the reinforcing pile adjacent to the existing pile, the surrounding ground of the existing pile can be improved and strengthened, preventing buckling of the existing pile (seismic strengthening) and increasing the bearing capacity of the existing pile. It becomes possible.

本発明の基礎強化工法によれば、杭のない既設基礎の直下に補強杭を設置して耐震性の高い杭基礎を構築することができる。   According to the foundation strengthening method of the present invention, a pile foundation having high earthquake resistance can be constructed by installing a reinforcement pile immediately below an existing foundation without piles.

本発明の基礎補強工法は、上記のように既設基礎の直下にグラウトを注入する注入管兼用の鋼管杭を既設基礎を支圧体として圧入設置する工法であり、（１）掘削工程、（２）補強杭圧入工程、（３）グラウト注入工程、（４）支持部材接合工程、（５）埋め戻し工程の５工程からなっている。これらの工程を補強対象の既設基礎の要補強箇所に順次施すことで既設基礎を効果的に補強することができる。 本発明の基礎補強工法の好適な態様を図１に示す橋脚のフーチング基礎１０の補強を例に説明する。図１（ａ）は橋脚の基礎１０を側方からみた概要図であり、（ｂ）は対応する平面概要図である。図１において、地盤Ｆ１は例えば沖積砂層や細粒土が混じった砂層などを含む軟弱地盤であり、所定の深さに岩盤などの支持層Ｆ２が存在している。橋脚１２はこのような地盤Ｆ１上に構築され、地盤Ｆ１内には図１（ｂ）の平面図で示すように４本の杭１６がフーチング基礎１４から支持層Ｆ２に達するように打設されている。   The foundation reinforcement construction method of the present invention is a construction method in which a steel pipe pile also serving as an injection pipe for injecting grout directly under an existing foundation as described above is press-fitted and installed using the existing foundation as a supporting body, (1) excavation process, (2 ) Reinforcement pile press-in step, (3) Grout injection step, (4) Support member joining step, (5) Backfill step. The existing foundation can be effectively reinforced by sequentially performing these steps on the reinforced portions of the existing foundation to be reinforced. A preferred embodiment of the foundation reinforcing method of the present invention will be described by taking the reinforcement of the footing foundation 10 of the pier shown in FIG. 1 as an example. Fig.1 (a) is the schematic diagram which looked at the foundation 10 of the pier from the side, (b) is a corresponding plane schematic diagram. In FIG. 1, the ground F1 is a soft ground including, for example, an alluvial sand layer or a sand layer mixed with fine-grained soil, and a support layer F2 such as a rock is present at a predetermined depth. The pier 12 is constructed on such ground F1, and in the ground F1, four piles 16 are driven so as to reach the support layer F2 from the footing foundation 14 as shown in the plan view of FIG. ing.

本実施の形態では上記のような橋脚の基礎１０の要補強部Ａ〜Ｄを補強する補強工法を図２〜図６に示す各工程に沿って説明する。なお、各図において、（ａ）は橋脚の基礎１０を側方からみた右半分の概要図であり、（ｂ）は対応する右半分の平面概要図である。   In the present embodiment, a reinforcing method for reinforcing the reinforcing portions A to D of the bridge pier foundation 10 as described above will be described along the steps shown in FIGS. In each figure, (a) is a schematic diagram of the right half when the pier foundation 10 is viewed from the side, and (b) is a schematic plan view of the corresponding right half.

（１）掘削工程（図２参照）
まず、フーチング基礎１４の隣り合う既設杭１６、１６の間の一次掘削部Ａをパワーシャベルなどの掘削機械を使用して掘り下げ、フーチング基礎１４の底面が露出するように作業空間Ａ’を掘削形成する。なお、この時、フーチング基礎１４の底面１４ａと作業空間Ａ’の底面１８までの深さｄは、後述する鋼管の長さよりも深く、かつこの鋼管を圧入する油圧ジャッキなどの押圧手段が設置できる深さに掘削する。 (1) Excavation process (see Fig. 2)
First, a primary excavation portion A between adjacent existing piles 16 and 16 of the footing foundation 14 is dug using a drilling machine such as a power shovel, and a work space A ′ is excavated so that the bottom surface of the footing foundation 14 is exposed. To do. At this time, the depth d from the bottom surface 14a of the footing foundation 14 to the bottom surface 18 of the work space A ′ is deeper than the length of the steel pipe described later, and pressing means such as a hydraulic jack for press-fitting the steel pipe can be installed. Drill to depth.

（２）補強杭圧入工程（図３参照）
次に、補強杭２０をフーチング基礎１４を支圧体として地盤Ｆ１中に圧入する。補強杭２０は所定長さの複数の鋼管２２を適宜に継ぎ足すことで形成する。鋼管２２は、所望の強度を有するものであればその材質や太さなどに制約はないが、例えば、ＳＴＫ４００の外径が５０〜３００ｍｍ、厚さが３〜１５ｍｍの鋼管などを好適に用いることができる。また、鋼管２２の長さについても特に限定はないが、既設基礎を支圧体として鋼管を圧入する押圧手段や圧入作業の作業性を考慮すると概ね３００〜２０００ｍｍとすることが好ましい。 (2) Reinforcement pile press-in process (see Fig. 3)
Next, the reinforcing pile 20 is press-fitted into the ground F1 using the footing foundation 14 as a supporting body. The reinforcing pile 20 is formed by appropriately adding a plurality of steel pipes 22 having a predetermined length. The material and thickness of the steel pipe 22 are not limited as long as they have a desired strength. For example, a steel pipe having an outer diameter of STK400 of 50 to 300 mm and a thickness of 3 to 15 mm is preferably used. Can do. Further, the length of the steel pipe 22 is not particularly limited, but is preferably about 300 to 2000 mm in consideration of pressing means for press-fitting the steel pipe with the existing foundation as a supporting body and workability of press-fitting work.

鋼管２２は図８（ａ）、（ｂ）にそれぞれの断面を模式的に示すように、一般鋼管２２ａと注入鋼管２２ｂとからなる。一般鋼管２２ａは、外管２４の先端に内管２６を突出部２６ａを設けて嵌着したものであり、突出部２６ａを他の鋼管２２の他端側に挿入して接続することができる。   The steel pipe 22 is composed of a general steel pipe 22a and an injected steel pipe 22b as schematically shown in FIGS. 8 (a) and 8 (b). The general steel pipe 22 a is formed by fitting an inner pipe 26 with a protruding part 26 a at the tip of the outer pipe 24, and the protruding part 26 a can be inserted and connected to the other end side of the other steel pipe 22.

また、図８（ｂ）に示す注入鋼管２２ｂは、前記の一般鋼管２２ａと同様に外管２４と内管２６とからなり、さらに外管２４の側部に軸心から放射状に穿設された複数のグラウト注入孔２８を備えている。各グラウト注入孔２８には鋼管２２の中空部３０に設けたホースなどの注入路３２が連通しており、圧入された補強杭２０の外部からこの注入路３２を介してミルクセメントなどのグラウトＧを注入することができる。なお、ビニールシートやゴムシートなどのシール材３６を注入孔２８を封止するように巻回して、グラウト注入前の地下水や土砂などの侵入による注入孔２８の閉塞を防止するとよい。   In addition, the injected steel pipe 22b shown in FIG. 8 (b) is composed of an outer pipe 24 and an inner pipe 26 in the same manner as the general steel pipe 22a, and is further drilled radially from the axial center in the side portion of the outer pipe 24. A plurality of grout injection holes 28 are provided. Each grout injection hole 28 communicates with an injection path 32 such as a hose provided in the hollow portion 30 of the steel pipe 22, and grout G such as milk cement is passed through the injection path 32 from the outside of the press-fitted reinforcement pile 20. Can be injected. Note that a sealing material 36 such as a vinyl sheet or a rubber sheet may be wound so as to seal the injection hole 28 to prevent the injection hole 28 from being blocked by intrusion of ground water or earth and sand before the injection of grout.

注入鋼管２２ｂの外管２４の先端部外周には鉄棒などからなるパッカーリング３４が固着されており、注入鋼管２２ｂを圧入することで外管４の外周周りに隙間ｅを形成することができる。この隙間ｅにより注入鋼管２２ｂの圧入時の上記シール材３６の位置ズレや破損の生じることを防止できる。   A packer ring 34 made of an iron bar or the like is fixed to the outer periphery of the outer end of the outer tube 24 of the injected steel tube 22b, and a gap e can be formed around the outer periphery of the outer tube 4 by press-fitting the injected steel tube 22b. Due to the gap e, it is possible to prevent the positional deviation or breakage of the sealing material 36 when the injected steel pipe 22b is press-fitted.

以上のように構成される鋼管２２を既設基礎１４の直下の所定の位置（図３（ｂ）では既設杭１６、１６の中間部）に順次圧入して補強杭２０を形成する。まず、注入鋼管２２ｂの上端部に油圧ジャッキやポストハンマーあるいはバイブルハンマーなどの押圧手段Ｐを設置し、フーチング基礎１４の底面１４ａを支圧面として作業空間Ａ’の底面１８から地盤Ｆ１中へ注入鋼管２２ｂを圧入する。なお、最初に圧入される注入鋼管２２の先端部（内管突出部２６ａの開口部）は適宜の方法で封止されている。所定深さまで注入管２２ｂを圧入したら、一旦押圧手段Ｐを取り外し、注入鋼管２２ｂの上端部に一般鋼管２２ａの内管突出部２６ａを挿入して嵌合し、かつ嵌着部を溶接など適宜の方法で接合して、注入鋼管２２ｂと一般鋼管２２ａとを連結する。続いて一般鋼管２２ａの上端部に再度押圧手段Ｐを設置して連結された鋼管２２を圧入する。   The steel pipe 22 configured as described above is sequentially press-fitted into a predetermined position directly below the existing foundation 14 (in the middle portion of the existing piles 16 and 16 in FIG. 3B) to form the reinforcing pile 20. First, pressing means P such as a hydraulic jack, a post hammer or a bible hammer is installed at the upper end of the injected steel pipe 22b, and the injected steel pipe is introduced from the bottom surface 18 of the work space A 'into the ground F1 with the bottom surface 14a of the footing foundation 14 as a bearing surface. 22b is press-fitted. In addition, the front-end | tip part (opening part of the inner pipe | tube protrusion part 26a) of the injection | pouring steel pipe 22 initially press-fit is sealed by the appropriate method. Once the injection tube 22b is press-fitted to a predetermined depth, the pressing means P is once removed, the inner tube protrusion 26a of the general steel tube 22a is inserted into the upper end portion of the injection steel tube 22b, and the fitting portion is welded appropriately. The injection steel pipe 22b and the general steel pipe 22a are connected by the method. Subsequently, the pressing means P is again installed on the upper end of the general steel pipe 22a and the connected steel pipe 22 is press-fitted.

以上のように一般鋼管２２ａと注入鋼管２２ｂとを適宜に継ぎ足して所望の深度、例えば支持層Ｆ２まで順々に圧入して補強杭２０を形成する。   As described above, the general steel pipe 22a and the injected steel pipe 22b are appropriately added, and the reinforcing pile 20 is formed by press-fitting in sequence to a desired depth, for example, the support layer F2.

（３）グラウト注入工程（図４参照）
この工程では、所定本数の鋼管２２を継ぎ足して圧入を完了した補強杭２０に、外部から注入路３２を介して補強杭２０の周辺地盤へグラウトＧを注入する。グラウト材としては、特に限定はないが、シリカコロイド、微粒子スラグ、微粒子セメントなどを主材として適宜の硬化剤や硬化促進剤などを混合した組成物や、セメントミルクなどを例示することができる。このようなグラウト材は補強杭２０を構成する注入鋼管２２ｂに穿設した各注入孔２８から周辺の地盤内へ注入される。 (3) Grout injection process (see Fig. 4)
In this step, grout G is injected into the surrounding ground of the reinforcing pile 20 from the outside through the injection path 32 to the reinforcing pile 20 that has been press-fitted by adding a predetermined number of steel pipes 22. The grout material is not particularly limited, and examples thereof include a composition in which silica colloid, fine particle slag, fine particle cement and the like are mixed as a main material and an appropriate hardening agent and hardening accelerator are mixed, and cement milk. Such a grout material is injected into the surrounding ground from each injection hole 28 formed in the injection steel pipe 22b constituting the reinforcing pile 20.

外部から注入路３２を介して注入孔２８に到達したグラウトＧは、巻回されているシール材３６を押圧して注入孔２８から噴出し隙間ｅに充満する。その後外部からの加圧力により半径方向に周辺の地盤へ侵入する。例えば、パッカーリングＲ１とＲ２との間に形成された隙間ｅ１では、補強杭２０の先端側に注入されたグラウトｇ１が注入孔２８から噴出すると、グラウトｇ１は隙間ｅ１内を矢印ｙに沿ってパッカーリングＲ２に遮られるまで上昇して隙間ｅ１に充満する。その後、加圧力によって矢印ｘのように放射状に周辺地盤へ侵入するので、隙間ｅ１の周辺を確実にグラウトｇ１で補強することができる。なお、このようなグラウト注入方法によれば、例えばグラウトｇ３の固結を待ってからグラウトｇ２を注入するなど地盤の性状によって、グラウトＧの種類のみならず注入のタイミングをも適宜調整することができる。   The grout G that has reached the injection hole 28 from the outside via the injection path 32 presses the wound sealing material 36 and fills the ejection gap e from the injection hole 28. After that, it penetrates into the surrounding ground in the radial direction by external pressure. For example, in the gap e1 formed between the packer rings R1 and R2, when the grout g1 injected into the distal end side of the reinforcing pile 20 is ejected from the injection hole 28, the grout g1 passes through the gap e1 along the arrow y. It rises until it is blocked by the packer ring R2 and fills the gap e1. Then, since it penetrates into the surrounding ground radially as indicated by an arrow x by the applied pressure, the periphery of the gap e1 can be reliably reinforced with the grout g1. According to such a grout injection method, not only the type of grout G but also the injection timing can be appropriately adjusted depending on the properties of the ground, such as injecting grout g2 after waiting for consolidation of grout g3. it can.

グラウトＧは、隣接する既設杭１６、１６を包含するように広範囲に注入することが好ましい。このように既設杭１６周辺の地盤を強化することで既設杭１６の支持力を増大して、耐震性を強化することができる。また、地下水の有無や土壌の性状に合わせて注入孔２８ごと（あるいは、注入鋼管２２ｂごと）に好適なグラウト材を選択することが望ましい。例えば、粘性土等の土壌では、懸濁型や溶液型の瞬結性のグラウト材ｇ１が好適であり、砂質土等の地盤には、超微粒子のセメントを懸濁させ優れた浸透性を有する長結性のグラウト材ｇ２を注入するとよい。   The grout G is preferably injected over a wide range so as to include the adjacent existing piles 16 and 16. Thus, by strengthening the ground around the existing pile 16, the supporting force of the existing pile 16 can be increased and the earthquake resistance can be enhanced. In addition, it is desirable to select a suitable grout material for each injection hole 28 (or for each injection steel pipe 22b) in accordance with the presence or absence of groundwater and the properties of the soil. For example, in soil such as clay soil, suspension type or solution type quick setting grout material g1 is suitable, and in soil such as sandy soil, ultrafine cement is suspended to provide excellent permeability. It is preferable to inject a long-grown grout material g2 having the same.

（４）支持部材接合工程（図５参照）
上記のようにしてグラウトの注入を完了した補強杭２０の上端部と、フーチング基礎１４の底面１４ａとは、ほぼ押圧手段Ｐの長さ分だけ隔てられており、この状態では補強杭２０はフーチング基礎１４を支持していない。そこで補強杭２０の上端部に支持部材３８を接合し、支持部材３８をフーチング基礎１４の底面１４ａに密着させて補強杭２０でフーチング基礎１４を支持するようにする。支持部材３８は圧入した補強杭２０とフーチング基礎の底面１４ａとの空隙を充填できる鋼管２２と同等程度の強度を有するものであれば特に限定はないが、鋼管２２の外管２４と同一の鋼管を支持部材とし、この鋼管を補強杭２０の上端部に溶接などで固着することでフーチング基礎１４を支持することができる。 (4) Support member joining step (see FIG. 5)
The upper end portion of the reinforcing pile 20 in which the grout injection has been completed as described above and the bottom surface 14a of the footing foundation 14 are substantially separated by the length of the pressing means P. In this state, the reinforcing pile 20 is footed. Does not support the foundation 14. Therefore, the supporting member 38 is joined to the upper end portion of the reinforcing pile 20, and the supporting member 38 is brought into close contact with the bottom surface 14 a of the footing foundation 14 to support the footing foundation 14 with the reinforcing pile 20. The support member 38 is not particularly limited as long as it has the same strength as the steel pipe 22 that can fill the gap between the press-fitted reinforcement pile 20 and the bottom surface 14a of the footing foundation, but the same steel pipe as the outer pipe 24 of the steel pipe 22 is used. The footing foundation 14 can be supported by fixing the steel pipe to the upper end of the reinforcing pile 20 by welding or the like.

（５）埋め戻し工程（図６参照）
次に、作業空間Ａ’を埋め戻して一次掘削部Ａをもとの状態に戻すが、フーチング基礎１４を補強する補強基礎を形成してから埋め戻す。例えば、発泡モルタルやモルタル等の補強材を補強杭２０を包含し、かつフーチング基礎１４の一部を埋没させるように流し込んで固結させ補強基礎４０とする。なお、作業空間Ａ’の適宜の領域に鉄筋籠やアングルなどを組み込んで補強基礎４０としてもよい。 (5) Backfill process (see Fig. 6)
Next, the work space A ′ is backfilled to return the primary excavation part A to the original state. However, after the reinforcing foundation for reinforcing the footing foundation 14 is formed, the work is refilled. For example, a reinforcing material such as foamed mortar or mortar includes the reinforcing pile 20 and is poured and consolidated so as to bury part of the footing foundation 14 to obtain the reinforcing foundation 40. In addition, a reinforcing bar 40 or an angle may be incorporated in an appropriate region of the work space A ′ to form the reinforcing foundation 40.

以上の（１）〜（５）の各工程を各既設杭１６、１６の間の要補強領域Ａ〜Ｄについて繰り返し、図７の平面図に示すように４本の補強杭２０Ａ〜２０Ｄを設置し、その周辺地盤をグラウトＧで強化することで橋脚１２の既設基礎１０全体を補強することができる。   The steps (1) to (5) described above are repeated for the reinforcing areas A to D between the existing piles 16 and 16, and four reinforcing piles 20A to 20D are installed as shown in the plan view of FIG. And the existing foundation 10 whole of the pier 12 can be reinforced by strengthening the surrounding ground with grout G.

このように補強された橋脚の基礎１０では、既設杭１６の中間位置に既設杭１６と同一深度（支持地盤Ｆ２に達する）まで補強杭２０が圧入形成されており、さらにグラウトＧを既設杭１６と補強杭２０とを一体的に包含するように注入して周辺地盤を固結強化した態様であるので、従来の薬液注入工法や高圧噴射攪拌工法などに比べてはるかに信頼性の高い均一な補強効果を得ることができる。   In the pier foundation 10 reinforced in this way, the reinforcing pile 20 is press-fitted and formed in the middle position of the existing pile 16 to the same depth as the existing pile 16 (which reaches the supporting ground F2). And the reinforcing pile 20 are integrally injected so that the surrounding ground is consolidated and strengthened, so that it is much more reliable and uniform than the conventional chemical injection method or high-pressure jet agitation method. A reinforcing effect can be obtained.

本発明は上記の実施の形態に限定されるものではなく、本発明の主旨を逸脱しない範囲で変更することができる。   The present invention is not limited to the above-described embodiment, and can be modified without departing from the gist of the present invention.

例えば、上記の実施の形態では、既設杭１６を有するフーチング基礎１４の補強について説明したが、図９（ａ）に示すように既設杭１６を有しないフーチング基礎１４のみの場合にも、（ｂ）に示すように本発明の基礎補強工法を適用して補強杭２０を有する杭基礎４２とすることができる。   For example, in the above embodiment, the reinforcement of the footing foundation 14 having the existing pile 16 has been described. However, as shown in FIG. The pile foundation 42 having the reinforcing pile 20 can be obtained by applying the foundation reinforcing method of the present invention as shown in FIG.

また、図１０のように軟弱地盤Ｆ３が基礎構築地盤Ｆ１と支持地盤Ｆ２との間に存在する場合には、既設杭１６に隣接して補強杭２０を圧入し、軟弱地盤Ｆ３にグラウトＧを注入することで、補強杭２０の増し杭効果と、既設杭１６と補強杭２０の支持力増大とを図ることができる。   In addition, when the soft ground F3 exists between the foundation construction ground F1 and the support ground F2 as shown in FIG. 10, the reinforcing pile 20 is press-fitted adjacent to the existing pile 16, and the grout G is put into the soft ground F3. By injecting, it is possible to increase the pile effect of the reinforcing pile 20 and increase the supporting force of the existing pile 16 and the reinforcing pile 20.

以上、フーチング基礎を例に実施の態様を説明したが、本発明の基礎補強工法はフーチング基礎など基礎の態様に限定されることなく、鋼管を圧入する際の支圧体として十分耐えうるものであれば、既設基礎がどのような種類の構造物や構築物を支持する態様の基礎（例えば、布基礎、ケーソン基礎など）であっても適用することができる。   As mentioned above, although the aspect of embodiment was demonstrated to the example of the footing foundation, the foundation reinforcement construction method of the present invention is not limited to the aspect of the foundation such as the footing foundation, and can sufficiently withstand as a bearing body when press-fitting a steel pipe. If so, the present invention can be applied to any type of foundation (for example, cloth foundation, caisson foundation, etc.) that supports any type of structure or structure.

本発明の基礎補強工法ば、軟弱地盤上に構築された構造物の基礎を補強する基礎補強工法として極めて有用であり、補強杭による既設基礎の支持力増強と、グラウト注入による地震発生時の地盤の液状化防止とを同時に達成することができる。本発明の基礎補強工法は、どのような種類の構造部や構築物を支持する態様の基礎であっても適用することができる。中でも橋脚のフーチング基礎や建物の基礎の補強には好適に用いることができる。   The foundation reinforcement method of the present invention is extremely useful as a foundation reinforcement method to reinforce the foundation of a structure built on soft ground, increasing the bearing capacity of existing foundations with reinforcement piles, and the ground when an earthquake occurs due to grouting. The prevention of liquefaction can be achieved at the same time. The foundation reinforcing method of the present invention can be applied to any type of foundation that supports a structure portion or a structure. Among them, it can be suitably used for reinforcing a footing foundation of a pier or a foundation of a building.

一実施の形態である橋脚の基礎の構成を説明する概要図である。（ａ）は側面図、（ｂ）は平面図である。It is a schematic diagram explaining the structure of the foundation of the pier which is one embodiment. (A) is a side view, (b) is a plan view. 図１の橋脚の基礎を補強する補強工法の掘削工程を示す説明図であり、（ａ）は側面模式図（片側のみ）、（ｂ）は平面模式図である。It is explanatory drawing which shows the excavation process of the reinforcement construction method which reinforces the foundation of the pier of FIG. 1, (a) is a side surface schematic diagram (only one side), (b) is a plane schematic diagram. 図２に続く補強杭圧入工程を示す説明図である。It is explanatory drawing which shows the reinforcement pile press-in process following FIG. 図３に続くグラウト注入工程を示す説明図である。FIG. 4 is an explanatory view showing a grout injection process following FIG. 3. 図４に続く支持部材接合工程を示す説明図である。It is explanatory drawing which shows the supporting member joining process following FIG. 図５に続く埋め戻し工程を示す説明図である。It is explanatory drawing which shows the backfilling process following FIG. 補強完了後の橋脚の基礎の平面模式図である。It is a plane schematic diagram of the foundation of the bridge pier after reinforcement completion. 補強杭の構成を説明する概要図である。（ａ）は一般鋼管の形状を説明する断面図、（ｂ）は注入鋼管の形状を説明する断面図である。It is a schematic diagram explaining the structure of a reinforcement pile. (A) is sectional drawing explaining the shape of a general steel pipe, (b) is sectional drawing explaining the shape of an injection steel pipe. その他の態様であり、既設杭を有しないフーチング基礎のみを補強する場合である。（ａ）は補強前を示す側面概要図であり、（ｂ）は補強後を示す側面概要図である。This is another embodiment, in which only the footing foundation having no existing pile is reinforced. (A) is the side surface schematic diagram which shows before reinforcement, (b) is the side surface schematic diagram which shows after reinforcement. その他の態様であり、部分的に軟弱地盤Ｆ３が存在する場合の補強の一例を示す。（ａ）は補強前を示す側面概要図であり、（ｂ）は補強後を示す側面概要図である。It is another aspect, and shows an example of reinforcement when soft ground F3 exists partially. (A) is the side surface schematic diagram which shows before reinforcement, (b) is the side surface schematic diagram which shows after reinforcement.

符号の説明Explanation of symbols

１０：橋脚の基礎 １２：橋脚 １４：フーチング基礎 １６：既設杭 １８：作業空間底面 ２０：補強杭 ２２：鋼管 ２２ａ：一般鋼管 ２２ｂ：注入鋼管 ２４：外管 ２６：内管 ２８：注入孔 ３２：注入路 ３４：パッカーリング ３６：シール ３８：支持部材 ４０：補強基礎 ４２：杭基礎
Ａ：一次掘削部 Ａ’：一次作業空間 Ｇ：グラウト（グラウト固結部） Ｆ１：基礎構築地盤 Ｆ２：支持地盤 Ｆ３：軟弱地盤 10: Foundation of bridge pier 12: Pier pier 14: Footing foundation 16: Existing pile 18: Bottom of work space 20: Reinforcement pile 22: Steel pipe 22a: General steel pipe 22b: Injection steel pipe 24: Outer pipe 26: Inner pipe 28: Injection hole 32: Injection path 34: Packer ring 36: Seal 38: Support member 40: Reinforcement foundation 42: Pile foundation A: Primary excavation part A ': Primary work space G: Grout (grout consolidation part) F1: Foundation construction ground F2: Support ground F3: Soft ground

Claims (4)

既設基礎の直下に鋼管からなる補強杭を土中に圧入する作業空間を掘削形成する掘削工程と、
前記既設基礎の底面を支圧面として前記補強杭を圧入する補強杭圧入工程と、
前記補強杭の中空部を介して地盤中にグラウトを注入するグラウト注入工程と、
前記既設基礎の底面を支持する支持部材を前記補強杭に接合する支持部材接合工程と、
掘削した前記作業空間に前記既設基礎を補強する補強基礎を形成して埋め戻す埋戻し工程とを有し、
前記補強杭は、前記グラウトを周辺地盤へ注入するグラウト注入孔を備える注入鋼管と一般鋼管とが継ぎ足されてなり、
前記グラウト注入孔には前記注入鋼管の中空部に挿設され前記補強杭の外部で開口するグラウト注入路が連通されていることを特徴とする基礎補強工法。 An excavation process for excavating and forming a work space in which a reinforcing pile made of steel pipe is press-fitted into the soil directly under the existing foundation;
Reinforcement pile press-in process for press-fitting the reinforcement pile with the bottom surface of the existing foundation as a bearing surface;
A grout injection step of injecting grout into the ground through the hollow portion of the reinforcing pile;
A support member joining step of joining a support member supporting the bottom surface of the existing foundation to the reinforcing pile;
A backfilling step for forming and reinforcing a reinforcing foundation for reinforcing the existing foundation in the excavated working space;
The reinforcing pile is made is injected steel and general steel pipe and the joint legs including a grout injection hole for injecting the grout into the surrounding ground,
Basic Retrofit grout injection path wherein the grouting holes opening outside of the reinforcing pile is inserted into the hollow portion of the injection steel pipe characterized that you have communicated. 前記グラウト注入孔は前記注入鋼管の側部に軸心から放射状に穿設されている請求項１に記載の基礎補強工法。 2. The foundation reinforcing method according to claim 1, wherein the grout injection holes are formed radially from an axial center in a side portion of the injected steel pipe. 前記注入鋼管の先端部外周にはパッカーリングが固着されている請求項１又は２のいずれかに記載の基礎補強工法。The foundation reinforcement construction method according to claim 1 or 2, wherein a packer ring is fixed to the outer periphery of the tip end portion of the injected steel pipe. 既設杭に隣接して前記補強杭を設置する請求項１〜３のいずれか１項に記載の基礎補強工法。 Basic Retrofit according to any one of claims 1 to 3, installing the reinforcing piles adjacent to existing pile.
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CN110130427A (en) * 2019-06-13 2019-08-16 国网江苏省电力有限公司连云港供电分公司 The reinforcement means and organizational pile foundation of precast hollow tubular pole

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JP6544566B2 (en) * 2015-05-01 2019-07-17 清水建設株式会社 Countermeasures against liquefaction of existing structures
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CN109555173A (en) * 2017-09-26 2019-04-02 安徽皖通高速公路股份有限公司 A kind of separate type bridge integrally lifts stake reinforcement means
CN110130427A (en) * 2019-06-13 2019-08-16 国网江苏省电力有限公司连云港供电分公司 The reinforcement means and organizational pile foundation of precast hollow tubular pole

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