JP3653083B2

JP3653083B2 - Road construction method

Info

Publication number: JP3653083B2
Application number: JP2003014547A
Authority: JP
Inventors: 哲彦三浦; 和之藤川; 章浜武; 英樹田中; 茂吉田; 功小林
Original assignee: Mitsubishi Materials Corp; Tenox Corp; Tenox Kyusyu Corp
Current assignee: Mitsubishi Materials Corp; Tenox Corp; Tenox Kyusyu Corp
Priority date: 2003-01-23
Filing date: 2003-01-23
Publication date: 2005-05-25
Anticipated expiration: 2017-05-19
Also published as: JP2003239276A

Description

【０００１】
【発明の属する技術分野】
本発明は、軟弱地盤上に盛土により道路を構築する際の構築工法に関する。また軟弱地盤上に設けられた暗渠などの地下構造物の上を横断する道路を盛土により構築する工法に関するものである。
【０００２】
【従来の技術】
埋土層や沖積層の層厚が厚い軟弱地盤の上に盛土により道路を構築する場合には次の工法が採られている。先ず図９に示すように軟弱地盤１の浅層部分にセメント系固化材を乾式混合した後固化して浅層改良土層２ａを形成することにより、浅層の剛性を高めた改良地盤２とするか、或いは図１０に示すように軟弱地盤１の浅層部分に生石灰を乾式混合した後固化して浅層改良土層２ｂを形成し、更にこの浅層改良土層２ｂの上にＦｅ石灰を乾式混合した後固化して浅層改良土層２ｃを形成することにより、浅層の剛性を高めた改良地盤２とする。次いで図９及び図１０に示すように、この改良地盤２を路床として、この上にクラッシャーラン層３ａ及び粒度調整用砕石層３ｂからなる盛土を設けて路盤３とした後、路盤３の上にアスファルト・コンクリート層４を設けて舗装している。
なお、本明細書では、路盤と舗装とを分離せずに両者を合せて道路舗装という。
【０００３】
また図１１又は図１２に示すように、埋土層や沖積層の層厚が厚い軟弱地盤１の浅層部分に沈下を抑制された暗渠などの地下構造物６を設け、この地下構造物６を横断する道路をこの地下構造物６及び地下構造物以外の軟弱地盤１の上を道路舗装することにより構築する場合には、先ず軟弱地盤１の深層部分に軟弱地盤の下方の支持層７に到達する支持杭８で地下構造物６を支持した後、地下構造物以外の軟弱地盤１の浅層部分に、図９又は図１０と同様に改良地盤２及び路盤３を形成した後、路盤３の上にアスファルト・コンクリート層４を設けて舗装している。橋梁の取付部においては、橋台の埋戻し土層或いは盛土層の沈下による橋台付近での段差防止策として、踏掛版工法が用いられている。
【０００４】
【発明が解決しようとする課題】
道路の路床には盛土による静的荷重とともに自動車の走行による動的荷重が加わり、これらの荷重が路床に伝達される。動的荷重の大きさは、盛土厚さが１．０ｍ程度と薄い場合には、静的荷重に匹敵し、かつ、長期間繰り返し作用する性質がある。そのため、地盤の改良の程度が十分でない場合、静的荷重による圧密沈下には十分に耐えられても、その数倍の動的荷重には耐えられず、道路が動的荷重により圧密沈下し続けることになる。一方、地盤を十分に改良すれば、動的荷重による圧密沈下を抑制することは可能であるが、地盤改良の程度と動的荷重による圧密沈下の抑制効果との関連が十分に把握されていないため、圧密沈下を抑制しようとするあまり、過剰に地盤改良を行って無用に工期が長引かせ、無駄な工費の支出を招くことが多かった。
【０００５】
また地下構造物及び地下構造物以外の軟弱地盤の上を道路舗装することにより構築する場合には、地下構造物は支持杭で支持されているため、沈下することはなく、沈下してもごく僅かである。この殆ど沈下しない地下構造物を横断して構築した道路に上述した静的荷重と動的荷重が加わると、図１１又は図１２の破線で示すように道路の地下構造物６の上の部分とそれに隣接する部分との境界に段差Ａを生じ、自動車の円滑な走行を阻害していた。このような段差は、補修しても繰り返し生じる。
【０００６】
本発明の目的は、比較的短い工期で安価に構築でき、軟弱地盤上に盛土により構築された道路が使用された際に、動的荷重による圧密沈下を抑制する道路の構築工法を提供することにある。
本発明の別の目的は、比較的短い工期で安価に構築でき、軟弱地盤上に設けられた暗渠などの地下構造物の上を横断する道路が使用された際に、道路の地下構造物の上の部分とそれに隣接する部分との境界に段差を生じさせない道路の構築工法を提供することにある。
【０００７】
【課題を解決するための手段】
請求項１に係る発明は、図１に示すように、道路基礎の軟弱地盤１１に複数本の柱状体２０を軟弱地盤下方の支持層に到達しない長さでかつ１０〜５０％の改良率で構築し、これら複数本の柱状体２０の上に補強用網状体２１を敷設し、この補強用網状体２１の上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設し、この浅層改良土層１３の上に道路舗装１８を構築することを特徴とする道路の構築工法である。
柱状体２０の上に補強用網状体２１を敷設し、この上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設し、更に道路舗装１８を行うことにより、図９及び図１０に示したクラッシャーラン層３ａの厚さを小さくして、道路の動的荷重による圧密沈下をより一層抑制することができる。また柱状体２０は軟弱地盤１１の下方の支持層に到達しない長さであるため、工期の短縮と工費の節減につながる。
【０００８】
請求項２に係る発明は、図２に示すように、道路基礎の軟弱地盤１１に埋設され沈下を抑制された地下構造物１２の近傍の軟弱地盤１１に複数本の柱状体２０を軟弱地盤下方の支持層１６に到達しない長さで地下構造物１２から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、これら複数本の柱状体２０の上に補強用網状体２１を敷設し、地下構造物１２及び補強用網状体２１の上に道路舗装１８を構築することを特徴とする道路の構築工法である。
柱状体２０の上に補強用網状体２１を介して道路舗装１８を行うことにより、図１１及び図１２に示した改良地盤２を省略して、道路の動的荷重による圧密沈下を抑制することができ、また複数本の柱状体２０を地下構造物１２から遠ざかるに従って段々に短くなるようにしたので、道路が使用された際に、地下構造物１２の近傍では圧密沈下を極力抑制し、離れるに従って徐々にある程度の圧密沈下を許容するようにする。これにより、道路の地下構造物１２の上の部分とそれに隣接する部分との境界に発生する段差を抑制することができる。また柱状体２０は軟弱地盤１１の下方の支持層１６に到達しない長さであるため、工期の短縮と工費の節減につながる。
【０００９】
請求項３に係る発明は、図３に示すように、道路基礎の軟弱地盤１１に埋設され沈下を抑制された地下構造物１２の近傍の軟弱地盤１１に複数本の柱状体２０を軟弱地盤下方の支持層１６に到達しない長さで地下構造物１２から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、これら複数本の柱状体２０の上に土砂と固化材を混合して固化することにより浅層改良土層１３を敷設し、この地下構造物１２及び浅層改良土層１３の上に道路舗装１８を構築することを特徴とする道路の構築工法である。
請求項４に係る発明は、請求項３に係る発明であって、土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設する道路の構築工法である。
柱状体２０の上に、土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設し、この上に道路舗装１８を行うことにより、図１１及び図１２に示したクラッシャーラン層３ａの厚さを小さくして、道路の動的荷重による圧密沈下を抑制することができ、また複数本の柱状体２０を地下構造物１２から遠ざかるに従って段々に短くなるようにしたので、請求項２に係る発明と同様に、道路が使用された際に、道路の地下構造物１２の上の部分とそれに隣接する部分との境界に段差を生じさせない。また柱状体２０は軟弱地盤１１の下方の支持層１６に到達しない長さであるため、工期の短縮と工費の節減につながる。
【００１０】
請求項５に係る発明は、図４に示すように、道路基礎の軟弱地盤１１に埋設され沈下を抑制された地下構造物１２の近傍の軟弱地盤１１に複数本の柱状体２０を軟弱地盤下方の支持層１６に到達しない長さで地下構造物１２から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、これら複数本の柱状体２０の上に補強用網状体２１を敷設し、この補強用網状体２１の上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設し、地下構造物１２及び浅層改良土層１３の上に道路舗装１８を構築することを特徴とする道路の構築工法である。
柱状体２０の上に補強用網状体２１を敷設し、この上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層１３を敷設し、更に道路舗装１８を行うことにより、図１１及び図１２に示したクラッシャーラン層３ａの厚さを小さくして、道路の動的荷重による圧密沈下をより一層抑制することができ、また複数本の柱状体２０を地下構造物１２から遠ざかるに従って段々に短くなるようにしたので、請求項２に係る発明と同様に、道路が使用された際に、道路の地下構造物１２の上の部分とそれに隣接する部分との境界に発生する段差を抑制することができる。また柱状体２０は軟弱地盤１１の下方の支持層１６に到達しない長さであるため、工期の短縮と工費の節減につながる。
【００１１】
請求項６に係る発明は、請求項１、４又は５に係る発明であって、土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて湿式混合して固化することにより浅層改良土層１３を敷設する道路の構築工法である。
湿式混合することにより、施工現場における粉体による発塵が抑制され、現場近隣の環境を粉体で汚染することがなくなる。また湿式混合方式では締め固めを必要とせず、品質のばらつきも少なくできる。
【００１２】
請求項７に係る発明は、請求項１、４、５又は６に係る発明であって、添加材が発泡ビーズ又は籾殻からなり、添加剤が気泡発生体からなり、添加材又は添加剤のいずれか一方又は双方が発泡ビーズ、籾殻及び気泡発生体からなる群より選ばれた１種又は２種以上の低密度体である道路の構築工法である。
添加材又は添加剤として低密度体を加えることにより、浅層改良土層１３を軽量化でき、浅層改良土層による静的荷重を低減することができる。また低密度体が動的荷重による振動を吸収するため、動的圧密沈下量を低減することができる。
【００１３】
請求項８に係る発明は、請求項１、４、５又は６に係る発明であって、添加材が産業廃棄物の焼却により形成されたクリンカである道路の構築工法である。
この工法によれば、産業廃棄物の焼却により形成された、処分に困窮しているクリンカを有効利用することができる。
【００１４】
請求項９に係る発明は、請求項１、４、５又は６に係る発明であって、添加材が無機繊維又は合成繊維である道路の構築工法である。
添加材として上記繊維を加えることにより、浅層改良土層１３が補強され、交通荷重による改良地盤の割れを防止し、改良地盤の耐久性が向上する。また繊維を含まない浅層改良土層より層厚を薄くしても繊維を含まない浅層改良土層と同等の耐久性が得られる。
【００１５】
請求項１０に係る発明は、請求項１ないし３又は５いずれか１項に係る発明であって、柱状体２０が既製杭又は地盤改良柱状体である道路の構築工法である。柱状体に既製杭を用いることにより、より短い工期で安価に施工でき、地盤改良柱状体を用いることにより、道路の圧密沈下をより確実に防止できる。
【００１６】
請求項１１に係る発明は、図５に示すように、請求項１ないし３又は５いずれか１項に係る発明であって、柱状体２０が地盤改良柱状体であって、この柱状体２０の胴部２０ａに節部２０ｂを有する道路の構築工法である。
地盤改良柱状体の胴部に節部２０ｂを設けることにより、地盤改良柱状体の沈下抵抗力が高まり、道路の圧密沈下を更により確実に防止できる。
【００１７】
請求項１２に係る発明は、図６に示すように、請求項１ないし３、５又は１１いずれか１項に係る発明であって、柱状体２０が地盤改良柱状体であって、この柱状体２０の先端が胴部２０ａより大径の拡大部２０ｃを有する道路の構築工法である。
地盤改良柱状体の先端に胴部より大径の拡大部２０ｃを設けることにより、地盤改良柱状体の沈下抵抗力が高まり、道路の圧密沈下を更により確実に防止できる。
【００１８】
請求項１３に係る発明は、請求項１ないし３、５、１１又は１２いずれか１項に係る発明であって、柱状体２０が地盤改良柱状体であって、柱状体２０が無機繊維又は合成繊維を含む道路の構築工法である。
柱状体に上記繊維を含ませることにより、軟弱地盤の側方流動により柱状体に亀裂が生じても、柱状体の曲げ抵抗力が発揮されて、その後の側方流動を抑えることができる。
【００１９】
請求項１４に係る発明は、請求項１ないし３、５又は１１ないし１３いずれか１項に係る発明であって、柱状体２０が地盤改良柱状体であって、この柱状体２０を機械撹拌法又は高圧噴射撹拌法により構築する道路の構築工法である。
地盤改良柱状体を機械撹拌法により構築することにより、安価でかつ土質にかかわらず改良体の外径を一定に築造することができる。また地盤改良柱状体を高圧噴射撹拌法により構築することにより、施工機械を小型化、軽量化することができるようになり、狭い場所や既設の踏掛版の下にも施工することができる。
【００２０】
【発明の実施の形態】
本発明は、軟弱地盤にこの軟弱地盤下方の支持層に到達しない柱状体を構築し、柱状体の上に補強用網状体又は浅層改良土層或いは補強用網状体と浅層改良土層の双方を敷設したものである。上記組合せを採用する際には、柱状体の長さと道路舗装の厚さに、浅層改良土層の厚さを加えた値Ｌが交通荷重、即ち動的荷重による圧密沈下を抑制するための大きな条件である。柱状体の改良率を１０〜５０％の範囲に構築し、かつこの値Ｌを４ｍ以上にすれば、動的荷重による圧密沈下を実質的に解消することができる。ここで、柱状体の改良率とは、図７及び図８に示すように柱状体を上方から視たときの改良地盤の単位面積に占める柱状体断面積の百分率をいう。柱状体の改良率が１０％未満では圧密沈下を十分に抑制することができず、５０％を越えた場合、かえって工期及び工費がかさむ不具合がある。好ましくはこの改良率は１５〜３０％である。
【００２１】
上記値Ｌは４ｍ以上必要ではあるが、大きくしてもそれ程動的圧密沈下の抑制効果は大きくならない。しかし、値Ｌが大きくなればそれに応じて静的圧密沈下の抑制効果は大きくなる。本発明では、過剰な地盤改良を避けるために、図２〜図４に示すように柱状体の下端は軟弱地盤１１の下方の支持層１６にまで到達しない。図１には支持層を示していないが、同様に柱状体２０は支持層まで到達しない。軟弱地盤の層厚及びその軟弱程度、荷重条件、経済性などを考慮して、この値Ｌの最大値は適宜決められる。図２に示すように浅層改良土層を設けずに、補強用網状体２１の上に直接道路舗装１８が施される場合には、柱状体２０の改良率を大きくする必要がある。
図２〜図４に示すように、地下構造物の近傍には長い柱状体を構築し、この地下構造物から離れるに従って段々に短い柱状体を構築する場合の段差解消工法では、効率的かつ経済的に行う必要から、地下構造物近傍の地盤改良の諸条件は、図１に示す道路全長にわたって改良する場合と同じ条件が適用され、地下構造物から離れるに従って柱状体の長さが段々に短くなり、最後にはゼロになる点が異なる。
【００２２】
図１、図２及び図４に示す、本発明の補強用網状体２１は無機繊維、合成繊維、合成樹脂、スチールなどの材料から形成された網状体である。無機繊維又は合成繊維からなる網状体は、この繊維から紐状体を作り、これを製網したものである。無機繊維にはガラス繊維が、また合成繊維にはポリアミド系のナイロン繊維、ポリオレフィン系のポリエチレン繊維、ポリプロピレン繊維等が例示される。合成樹脂にはポリエチレンやポリプロピレン樹脂等が例示される。スチールからなる網状体は、板状のスチールに周縁を残して多数本の切れ目を平行に入れた後、切れ目と直交する方向に板状のスチールの両縁を引張ることにより形成される。上記網状体の網目の間隔は１０〜２００ｍｍであり、要求される補強程度により、補強用網状体を１枚で使用するか、或いは複数枚重ね合せて使用する。
【００２３】
図１、図３及び図４に示す、本発明の浅層改良土層１３は土砂と、粉体又はスラリー状のセメント、セメント系固化材、生石灰等の固化材と、添加材又は添加剤のいずれか一方又は双方とを均一に混合して固化することにより敷設される。対象地盤の含水状態により、混合して締め固めて浅層改良土層を形成する場合と、締め固めずに形成する場合がある。対象地盤の含水率が少ない場合で、スラリー状の固化材を用いて、この固化材と土砂に添加材又は添加剤のいずれか一方又は双方を更に加えて湿式混合すれば、施工現場における粉体による発塵が抑制され、現場近隣の環境を粉体で汚染することがなくなる。
【００２４】
本発明の添加材には、発泡ビーズ、籾殻等の低密度体や、産業廃棄物の焼却により形成されたクリンカや、無機繊維又は合成繊維等が挙げられる。また本発明の添加剤には気泡発生体が挙げられる。上記添加材又は添加剤は１種類でも、２種以上混合して添加してもよい。添加材と添加剤とを混合してもよい。発泡ビーズは浅層改良土層を形成する材料１００体積％に対して２０〜５０体積％添加する。２０体積％未満では添加目的を達成できず、５０体積％を越えると固化したときの浅層改良土層の強度が低下する。上記低密度体を加えることによって、浅層改良土層が軽量化され、静的圧密沈下量を小さくできるとともに、浅層改良土層の弾性係数が小さくなり、交通荷重による動的荷重を吸収する。これに伴って柱状体の長さを短くしても圧密沈下を防止することができる。
【００２５】
低密度体の気泡発生体としてはポリオキシエチレンアルキルエーテル系化合物や高級アルコール硫酸エステル系化合物等が例示される。この気泡発生体は混合前は液体であるが、浅層改良土層を造成するときに層中に気泡を連行させる物質である。籾殻を低密度体とした場合、籾殻はＳｉＯ₂分を多く含むため、耐食性が大きく、かつその形状から長期にわたって浅層改良土層の剪断強度を増大させるために交通荷重に対して抵抗力が大きい。
産業廃棄物の焼却により形成された直径が５ｍｍ以下のクリンカを添加材とする場合、この処分に困窮しているクリンカを有効利用することができる。
【００２６】
無機繊維又は合成繊維を添加材とする場合、好ましくは長さ２〜４ｃｍ程度のスチール繊維等の無機繊維、又は長さ４〜７ｃｍ程度のポリアミド系のナイロン繊維、ポリオレフィン系のポリエチレン繊維、ポリプロピレン繊維からなる合成繊維が用いられる。長さが上記下限値未満では補強効果に乏しく、上記上限値を越えると、他の材料との混合時に取扱いにくくなる。添加材として上記繊維を加えることにより、浅層改良土層が補強され、交通荷重による改良地盤の割れを防止し、改良地盤の耐久性が向上する。また繊維を含まない浅層改良土層より層厚を薄くしても繊維を含まない浅層改良土層と同等の耐久性が得られる。
上記目的を達成するために、浅層改良土層を形成する材料１００体積％に対して、籾殻、無機繊維又は合成繊維等は０．１〜５．０体積％、好ましくは０．２〜２．０体積％添加し、クリンカは３０体積％以下で添加する。また気泡発生体は浅層改良土層を形成する材料１００重量％に対して０．０１〜１．０重量％、好ましくは０．１〜０．５重量％添加する。
【００２７】
柱状体の構築工法には、木杭、既製コンクリート杭、鋼杭等のような既製杭を深層地盤に打込む工法と、地盤改良柱状体を構築する工法がある。柱状体に既製杭を用いることにより、より短い工期で安価に施工でき、地盤改良柱状体を用いることにより、道路の圧密沈下をより確実に防止できる。この地盤改良柱状体を構築工法には機械撹拌法と高圧噴射撹拌法があるが、機械撹拌法により地盤改良柱状体を構築すると、安価でかつ土質にかかわらず改良体の外径を一定に築造することができる。また高圧噴射撹拌法により構築することにより、施工機械を小型化、軽量化することができるようになり、狭い場所や既設の踏掛版の下にも施工することができる。この地盤改良柱状体を構築する場合、図５に示すように地盤改良柱状体２０の胴部２０ａに節部２０ｂを形成することもできる。これにより地盤改良柱状体の周面の摩擦力が大きくなり、沈下抵抗力が高まって道路の圧密沈下を更により確実に防止できる。また軟弱地盤の側方流動を発生しにくくする利点もある。また地盤改良柱状体を構築する場合に、図６に示すように地盤改良柱状体２０の先端に胴部２０ａより大径の拡大部２０ｃを形成することもできる。これにより、地盤改良柱状体の沈下抵抗力がより高まり、道路の圧密沈下を更により確実に防止できる。
【００２８】
更に地盤改良柱状体２０に無機繊維又は合成繊維を含ませることもできる。この場合、好ましくは、無機繊維に長さ２〜４ｃｍ程度のスチール繊維が、また合成繊維に長さ４〜７ｃｍ程度のポリアミド系のナイロン繊維、ポリオレフィン系のポリエチレン繊維、ポリプロピレン繊維が用いられる。長さが上記下限値未満では補強効果に乏しく、上記上限値を越えると、他の材料との混合時に取扱いにくくなる。この繊維は地盤改良柱状体を形成する全ての材料に対して０．２〜２．０体積％程度含有する。柱状体に上記繊維を含ませることにより、軟弱地盤の側方流動により柱状体に亀裂が生じても、柱状体の曲げ抵抗力が発揮されて、その後の側方流動を抑えることができる。
【００２９】
柱状体を構築することにより、動的荷重による地盤の側方流動を防止することができる。上方から視た場合の柱状体の構築の仕方を図７及び図８に基づいて説明する。工事の効率及び経済性を考慮して、柱状体の平面配置は図７に示すような格子状配置にするか、或いは図８に示すような非接触形千鳥配置にして、改良率をできるだけ低く抑えるのが好ましい。改良率を１０〜５０％の範囲にして図７に示す格子状配置にした場合には、格子間隔ｄ₁（但し、格子間隔ｄ₁≧格子間隔ｄ₂）が柱状体の上端から道路舗装面までの高さの２倍以下であれば、また同様に改良率を１０〜５０％の範囲にして図８に示す非接触形千鳥配置にした場合にも、道路の方向をＤとしたときに、柱状体間隔ｄ₃（但し、柱状体間隔ｄ₃≧柱状体間隔ｄ₄）が柱状体の上端から道路舗装面までの高さの２倍以下であれば、それぞれ静的荷重、動的荷重は柱状体に確実に伝達され、十分地盤の側方流動を防止することができる。
【００３０】
図１〜図４に示すように、本発明の道路舗装１８はクラッシャーラン層１８ａ、粒度調整砕石層１８ｂ及びアスファルト・コンクリート１８ｃからなる。図１〜図４において、クラッシャーラン層１８ａは５〜１５ｃｍの厚さに、粒度調整砕石層１８ｂは１０〜３０ｃｍの厚さに、またアスファルト・コンクリート１８ｃは１０〜４０ｃｍの厚さにそれぞれ敷設される。
【００３１】
【実施例】
次に本発明の実施例を比較例とともに図面に基づいて説明する。
＜実施例１＞
図１に示すように、対象軟弱地盤１１に機械撹拌法により地盤改良柱状体２０を軟弱地盤１１の下方の支持層に到達しない長さで構築した。このとき柱状体はそれぞれ直径ａが８０ｃｍ、長さＬ₄が４００ｃｍであって、図８に示す間隔ｄ₃，ｄ₄がそれぞれ１２５ｃｍ、改良率２５．７％で、非接触形千鳥配置に構築した。
地盤改良柱状体２０の上に、ガラス繊維からなる補強用網状体２１を敷設し、この上に、掘削土及び別に用意した土砂にセメント粉を加え、更に添加材として低密度体である籾殻を材料全体の２０重量％加えて、乾式混合した後、締め固めることにより浅層改良土層１３をＬ₅＝６０ｃｍの厚さに敷設した。この上にクラッシャーラン層１８ａを３０ｃｍの厚さに敷設し、更にこの上に粒度調整砕石層１８ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート１８ｂで舗装した。図１に示す総合長さＬは５０５ｃｍであった。
＜比較例１＞
図９に示すように、実施例１と同一の対象軟弱地盤１を掘削し、この掘削土及び別に用意した土砂にセメント系固化材を加えて、乾式混合した後、締め固めることにより浅層改良土層２ａを６０ｃｍの厚さに敷設した。この上にクラッシャーラン層３ａを３０ｃｍの厚さに設けた後、更にこの上に粒度調整用砕石層３ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート４で舗装した。図９に示す総合長さＬは１０５ｃｍであった。
＜比較例２＞
図１０に示すように、実施例１と同一の対象軟弱地盤１を掘削し、この掘削土及び別に用意した土砂に生石灰を固化材として加えて、乾式混合した後、締め固めることにより浅層改良土層２ｂを１５０ｃｍの厚さに敷設した。この浅層改良土層２ｂの上にＦｅ石灰を乾式混合した後固化して浅層改良土層２ｃを３０ｃｍの厚さに形成した。この浅層改良土層２ｃの上にクラッシャーラン層３ａを３０ｃｍの厚さに設けた後、更にこの上に粒度調整用砕石層３ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート４で舗装した。図１０に示す総合長さＬは２２５ｃｍであった。
＜実施例２＞
図２に示すように、実施例１と同一の軟弱地盤１１を掘削し、地下構造物１２である暗渠を支持杭１７を介して支持層１６に支持した後、この暗渠の近傍の対象軟弱地盤１１に機械撹拌法によりそれぞれ直径ａが８０ｃｍの地盤改良柱状体２０を軟弱地盤１１の下方の支持層１６に到達しない長さで構築した。このとき柱状体が暗渠から遠ざかるに従って段々に短くなるように地盤改良柱状体２０を構築した。暗渠に最も近い柱状体の長さＬ₇は４００ｃｍであって、柱状体は図８に示す間隔ｄ₁，ｄ₂がそれぞれ１２５ｃｍ、改良率２５．７％で、非接触形千鳥配置に構築した。
地盤改良柱状体２０の上にガラス繊維からなる補強用網状体２１を敷設し、この上にクラッシャーラン層１８ａを３０ｃｍの厚さに敷設し、更にこの上に粒度調整砕石層１８ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート１８ｃで舗装した。図２に示す最長の地盤改良柱状体の下端から支持層１６までの深さＬ₆は２０ｍであり、総合長さＬは４４５ｃｍであった。
＜実施例３＞
図３に示すように、実施例１と同一の軟弱地盤１１を掘削し、実施例２と同様にして暗渠１２を支持層１６に支持した後、この暗渠の近傍の軟弱地盤１１に機械撹拌法によりそれぞれ直径ａが８０ｃｍの地盤改良柱状体２０を実施例２と同様に柱状体が暗渠から遠ざかるに従って段々に短くなるようにかつ軟弱地盤１１の下方の支持層１６に到達しない長さで構築した。暗渠に最も近い柱状体の長さＬ₉は４００ｃｍであって、柱状体は図８に示す間隔ｄ₃，ｄ₄がそれぞれ１２５ｃｍ、改良率２５．７％で、非接触形千鳥配置に構築した。
地盤改良柱状体２０の上に、掘削土及び別に用意した土砂にスラリー状のセメント系固化材を加え、更に添加材として低密度体である発泡ビーズを材料全体の３０体積％加えて、湿式混合し浅層改良土層１３をＬ₁₀＝３０ｃｍの厚さに敷設した。この上にクラッシャーラン層１８ａを３０ｃｍの厚さに敷設し、更にこの上に粒度調整砕石層１８ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート１８ｃで舗装した。図３に示す最長の地盤改良柱状体の下端から支持層１６までの深さＬ₈は２０ｍであり、総合長さＬは４７５ｃｍであった。
＜実施例４＞
図４に示すように、実施例１と同一の軟弱地盤１１を掘削し、実施例２と同様にして暗渠１２を支持層１６に支持した後、この暗渠の近傍の軟弱地盤１１に機械撹拌法によりそれぞれ直径ａが８０ｃｍの地盤改良柱状体２０を実施例２と同様に柱状体が暗渠から遠ざかるに従って段々に短くなるようにかつ軟弱地盤１１の下方の支持層１６に到達しない長さで構築した。暗渠に最も近い柱状体の長さＬ₁₂は４００ｃｍであって、柱状体は図８に示す間隔ｄ₃，ｄ₄がそれぞれ１２５ｃｍ、改良率２５．７％で、非接触形千鳥配置に構築した。
地盤改良柱状体２０の上に、ガラス繊維からなる補強用網状体２１を敷設し、この上に、掘削土及び別に用意した土砂にセメント粉を加え、更に添加材として低密度体である籾殻を材料全体の２０体積％加えて、乾式混合した後、締め固めることにより浅層改良土層１３をＬ₁₃＝３０ｃｍの厚さに敷設した。この上にクラッシャーラン層１８ａを３０ｃｍの厚さに敷設し、更にこの上に粒度調整砕石層１８ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート１８ｃで舗装した。図４に示す最長の地盤改良柱状体の下端から支持層１６までの深さＬ₁₁は２０ｍであり、総合長さＬは４７５ｃｍであった。
＜比較例３＞
図１１に示すように、実施例１と同一の軟弱地盤１を掘削し、実施例２と同様にして暗渠６を支持杭８を介して支持層７に支持した後、この暗渠の近傍の軟弱地盤１を掘削し、この掘削土及び別に用意した土砂にセメント系固化材を加えて、乾式混合した後、締め固めることにより浅層改良土層２ａを６０ｃｍの厚さに敷設した。この上にクラッシャーラン層３ａを３０ｃｍの厚さに設けた後、更にこの上に粒度調整用砕石層３ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート４で舗装した。図１１に示す総合長さＬは１０５ｃｍであった。
＜比較例４＞
図１２に示すように、実施例１と同一の軟弱地盤１を掘削し、実施例２と同様にして暗渠６を支持杭８を介して支持層７に支持した後、この暗渠の近傍の軟弱地盤１を掘削し、この掘削土及び別に用意した土砂に生石灰を固化材として加えて、乾式混合した後、締め固めることにより浅層改良土層２ｂを１５０ｃｍの厚さに敷設した。この浅層改良土層２ｂの上にＦｅ石灰を乾式混合した後固化して浅層改良土層２ｃを３０ｃｍの厚さに形成した。この浅層改良土層２ｃの上にクラッシャーラン層３ａを３０ｃｍの厚さに設けた後、更にこの上に粒度調整用砕石層３ｂを１０ｃｍの厚さに敷設し、その上を５ｃｍの厚さのアスファルト・コンクリート４で舗装した。図１２に示す総合長さＬは２２５ｃｍであった。
＜比較例５＞
図３に示した地盤改良柱状体２０を長くして、その柱状体の下端を軟弱地盤の下部の支持層１６に埋設するようにした（図示せず）以外は、実施例３と同様にして地盤を改良した。
＜比較試験とその結果＞
実施例１〜実施例４及び比較例１〜比較例５の各種工法で構築された道路の沈下量及び段差の発生状況について、構築してから使用開始されるまでの間と、使用開始してから７２０日経過するまでの間を測定した。また道路構築に要した工費について、実施例１を１００としたときの他の実施例及び比較例の概算値について調べた。これらの結果を表１に示す。
【００３２】
【表１】

【００３３】
(a) 沈下量及び段差の発生状況について：
表１から明らかなように、実施例１の工法により構築された道路も、比較例１及び２の工法により構築された道路も、使用が開始されるまでの静的荷重による沈下量はいずれも小さく、実施例１の工法と比較例１及び２の工法との間に有意差は認められなかった。しかし、道路が使用されてからは動的荷重に起因して、比較例１，２の工法による道路の沈下量が大きかったのに対して、実施例１の工法による道路の沈下量は小さかった。
【００３４】
また地下構造物である暗渠の近傍に柱状体を構築した場合、実施例２〜４の工法により構築された道路も、比較例５の工法により構築された道路も、使用が開始されるまでの静的荷重による沈下量はいずれも小さく、図１１及び図１２に示される段差Ａは見られず、実施例２〜４の工法と比較例５の工法との間に有意差は認められなかった。また３個の実施例の間でも有意差があるとは言えなかった。
しかし比較例３及び４の工法により構築された道路は使用が開始されるまでの静的荷重による沈下量が比較的大きく、他の実施例２〜４の工法と比較例５の工法との間に有意差が認められた。また道路が使用されてからは動的荷重に起因して、比較例３，４の工法による道路の沈下量は著しく大きく、段差Ａがはっきりと現れたのに対して、実施例２〜４及び比較例５の工法による道路の沈下量はすべて小さく、段差は全く生じなかった。実施例２〜４の工法による道路の中で、特に実施例２及び３はその沈下量が比較的小さく、比較例５に匹敵する値を示した。
(b) 工費について：
実施例１の工法の工費を１００としたときの他の実施例２〜４の各工法の工費の概算値は、沈下量の大きな比較例１〜４の各工法の工費の概算値よりも高価であったが、柱状体の下端を支持層に埋設するようにした比較例５の工法の工費の概算値の約２０％〜約２７％の低いものであった。
【００３５】
【発明の効果】
以上述べたように、本発明によれば、工期を無用に長引かせる過剰な地盤改良を行わずに、比較的短い工期で安価に道路を構築することができ、軟弱地盤上に盛土により構築された道路が使用された際に、動的荷重による圧密沈下を抑制することができる。
また、軟弱地盤上に設けられた暗渠などの地下構造物の上を横断する道路が使用された際に、道路の地下構造物の上の部分とそれに隣接する部分との境界に段差を生じさせることがない優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明の実施例１の工法で構築した道路方向に直交する方向から視た断面図。
【図２】本発明の実施例２の工法で構築した道路方向に直交する方向から視た断面図。
【図３】本発明の実施例３の工法で構築した道路方向に直交する方向から視た断面図。
【図４】本発明の実施例４の工法で構築した道路方向に直交する方向から視た断面図。
【図５】本発明の胴部に節部を有する地盤改良柱状体の正面図。
【図６】本発明の先端に拡大部を有する地盤改良柱状体の正面図。
【図７】本発明の格子状に配置した地盤改良柱状体の平面図。
【図８】本発明の非接触形千鳥に配置した地盤改良柱状体の平面図。
【図９】比較例１の工法で構築した道路方向に直交する方向から視た断面図。
【図１０】比較例２の工法で構築した道路方向に直交する方向から視た断面図。
【図１１】比較例３の工法で構築した道路方向に直交する方向から視た断面図。
【図１２】比較例４の工法で構築した道路方向に直交する方向から視た断面図。
【符号の説明】
１１軟弱地盤
１２地下構造物
１３浅層改良土層
１６支持層
１７支持杭
１８道路舗装
１８ａクラッシャーラン層
１８ｂ粒度調整砕石層
１８ｃアスファルト・コンクリート
２０柱状体
２０ａ胴部
２０ｂ節部
２０ｃ拡大部
２１補強用網状体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction method for constructing a road by embankment on soft ground. The present invention also relates to a method for constructing a road that crosses an underground structure such as a culvert provided on soft ground by embankment.
[0002]
[Prior art]
When building roads by embankment on soft ground with thick buried or alluvium layers, the following method is adopted. First, as shown in FIG. 9, the improved ground 2 with improved rigidity of the shallow layer is obtained by dry mixing the cement-based solidified material in the shallow layer portion of the soft ground 1 and then solidifying to form the shallow improved soil layer 2 a. Alternatively, as shown in FIG. 10, quick lime is dry-mixed in the shallow layer portion of the soft ground 1 and then solidified to form the shallow improved soil layer 2b, and the Fe lime is further formed on the shallow improved soil layer 2b. The dry ground is solidified and then solidified to form the shallow improved soil layer 2c, whereby the improved ground 2 with improved shallow layer rigidity is obtained. Next, as shown in FIG. 9 and FIG. 10, the improved ground 2 is used as a road bed, and the embankment composed of a crusher run layer 3 a and a crushed stone layer 3 b for particle size adjustment is provided thereon to form the road bed 3. Asphalt / concrete layer 4 is provided and paved.
In this specification, the roadbed and the pavement are referred to as road pavement without combining them.
[0003]
Further, as shown in FIG. 11 or FIG. 12, an underground structure 6 such as a culvert with subsidence suppressed is provided in a shallow layer portion of the soft ground 1 having a thick buried layer or alluvial layer, and the underground structure 6 When the road crossing the road is constructed by road paving on the underground structure 6 and the soft ground 1 other than the underground structure, first, a deep layer portion of the soft ground 1 is provided with a support layer 7 below the soft ground. After supporting the underground structure 6 with the support pile 8 that reaches, after forming the improved ground 2 and the roadbed 3 in the shallow layer portion of the soft ground 1 other than the underground structure, as in FIG. 9 or FIG. The asphalt concrete layer 4 is provided on the pavement. At the bridge mounting part, a stepping plate method is used as a measure to prevent a step near the abutment due to the sinking of the backfill or embankment layer of the abutment.
[0004]
[Problems to be solved by the invention]
A dynamic load due to the traveling of an automobile is applied to the road bed as well as a static load due to embankment, and these loads are transmitted to the road bed. When the embankment thickness is as thin as about 1.0 m, the dynamic load is comparable to a static load and has a property of repeatedly acting for a long time. Therefore, if the degree of ground improvement is not enough, even if it can sufficiently withstand consolidation settlement due to static load, it cannot withstand several times the dynamic load, and the road will continue to settle due to dynamic load. It will be. On the other hand, if the ground is sufficiently improved, consolidation settlement due to dynamic load can be suppressed, but the relationship between the degree of ground improvement and the suppression effect of consolidation settlement due to dynamic load is not fully understood. For this reason, excessive attempts to suppress consolidation settlement caused excessive ground improvement, unnecessarily prolonging the construction period, and incurring unnecessary construction costs.
[0005]
In addition, when building by building roads on soft ground other than underground structures and underground structures, the underground structures are supported by support piles, so they will not sink, There are few. When the static load and the dynamic load described above are applied to the road constructed across the underground structure that hardly sinks, as shown by the broken line in FIG. 11 or FIG. A step A was produced at the boundary with the adjacent portion, and the smooth running of the automobile was hindered. Such a step is repeatedly generated even after repair.
[0006]
An object of the present invention is to provide a road construction method that can be constructed inexpensively in a relatively short construction period and suppresses consolidation settlement due to dynamic load when a road constructed by embankment on soft ground is used. It is in.
Another object of the present invention is that it can be constructed inexpensively with a relatively short construction period, and when a road crossing over an underground structure such as a culvert provided on soft ground is used, the underground structure of the road An object of the present invention is to provide a road construction method that does not cause a step at the boundary between the upper part and the adjacent part.
[0007]
[Means for Solving the Problems]
As shown in FIG. 1, the invention according to claim 1 has a length that does not reach the support layer below the soft ground and the improvement rate of 10 to 50% on the soft ground 11 on the road foundation. Then, a reinforcing mesh 21 is laid on the plurality of columnar bodies 20, and either one or both of an additive or an additive is further added to the earth and sand and the solidifying material on the reinforcing mesh 21. This is a road construction method characterized in that a shallow improved soil layer 13 is laid by mixing and solidifying, and a road pavement 18 is constructed on the shallow improved soil layer 13.
A reinforcing net-like body 21 is laid on the columnar body 20, and either one or both of an additive or an additive is further added to the earth and sand and the solidifying material, and the mixture is solidified to be solidified. By laying 13 and further performing road pavement 18, the thickness of the crusher run layer 3 a shown in FIGS. 9 and 10 can be reduced, and the consolidation settlement due to the dynamic load on the road can be further suppressed. Moreover, since the columnar body 20 has a length that does not reach the support layer below the soft ground 11, it leads to a shortened construction period and a reduction in construction costs.
[0008]
In the invention according to claim 2, as shown in FIG. 2, a plurality of columnar bodies 20 are provided on the soft ground 11 in the vicinity of the underground structure 12 embedded in the soft ground 11 of the road foundation and settling suppressed. It is constructed at a rate of improvement of 10 to 50% so as to gradually shorten as it gets away from the underground structure 12 with a length that does not reach the support layer 16, and a reinforcing mesh 21 is provided on the plurality of columnar bodies 20. The road construction method is characterized in that a road pavement 18 is constructed on the underground structure 12 and the reinforcing net 21 by laying.
By performing the road pavement 18 on the columnar body 20 via the reinforcing mesh body 21, the improved ground 2 shown in FIG. 11 and FIG. 12 is omitted and the consolidation settlement due to the dynamic load on the road is suppressed. In addition, since the plurality of columnar bodies 20 are gradually shortened as they move away from the underground structure 12, when the road is used, in the vicinity of the underground structure 12, the consolidation settlement is suppressed as much as possible and separated. Gradually allow a certain amount of consolidation settlement. Thereby, the level | step difference which generate | occur | produces in the boundary of the part on the underground structure 12 of a road and the part adjacent to it can be suppressed. Moreover, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, it leads to a shortening of the construction period and a reduction in construction costs.
[0009]
As shown in FIG. 3, the invention according to claim 3, as shown in FIG. 3, places a plurality of columnar bodies 20 on the soft ground 11 in the vicinity of the underground structure 12 buried in the soft ground 11 of the road foundation and restrained from sinking below the soft ground. It is constructed at a rate of improvement of 10 to 50% so that the length does not reach the support layer 16 and gradually decreases as it moves away from the underground structure 12, and earth and sand and solidified material are mixed on the plurality of columnar bodies 20. Then, the shallow improved soil layer 13 is laid by solidifying, and the road pavement 18 is constructed on the underground structure 12 and the shallow improved soil layer 13.
The invention according to claim 4 is the invention according to claim 3, wherein either one or both of an additive or an additive is further added to the earth and the solidifying material, and the mixture is solidified to be solidified. This is a construction method of a road laying 13.
A shallow soil improvement soil layer 13 is laid on the columnar body 20 by further adding one or both of an additive or an additive to the sand and the solidifying material, and mixing and solidifying, and a road pavement 18 is formed thereon. 11 and 12, the thickness of the crusher run layer 3a shown in FIGS. 11 and 12 can be reduced to suppress consolidation settlement due to the dynamic load of the road, and the plurality of columnar bodies 20 can be connected to the underground structure. As the distance from 12 is gradually shortened, as in the invention according to claim 2, when the road is used, the boundary between the upper portion of the underground structure 12 of the road and the portion adjacent thereto is used. Does not cause a step. Moreover, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, it leads to a shortening of the construction period and a reduction in construction costs.
[0010]
As shown in FIG. 4, the invention according to claim 5, as shown in FIG. 4, places a plurality of columnar bodies 20 on the soft ground 11 near the underground structure 12 embedded in the soft ground 11 of the road foundation and restrained from sinking below the soft ground. It is constructed at a rate of improvement of 10 to 50% so as to gradually shorten as it gets away from the underground structure 12 with a length that does not reach the support layer 16, and a reinforcing mesh 21 is provided on the plurality of columnar bodies 20. Laying on the reinforcing net-like body 21, the shallow improvement soil layer 13 is laid by adding one or both of the additive and / or additive to the earth and sand and further solidifying by mixing. The road construction method is characterized in that a road pavement 18 is constructed on the structure 12 and the shallow improved soil layer 13.
A reinforcing net-like body 21 is laid on the columnar body 20, and either one or both of an additive or an additive is further added to the earth and sand and the solidifying material, and the mixture is solidified to be solidified. 13 and further road pavement 18, the thickness of the crusher run layer 3 a shown in FIGS. 11 and 12 can be reduced, and the consolidation settlement due to the dynamic load of the road can be further suppressed. Further, since the plurality of columnar bodies 20 are gradually shortened as the distance from the underground structure 12 increases, when the road is used, the top of the road underground structure 12 is removed. Can be suppressed from occurring at the boundary between this part and the part adjacent thereto. Moreover, since the columnar body 20 has a length that does not reach the support layer 16 below the soft ground 11, it leads to a shortening of the construction period and a reduction in construction costs.
[0011]
The invention according to claim 6 is the invention according to claim 1, 4 or 5, by further adding either one or both of an additive or an additive to earth and sand and a solidifying material, followed by wet mixing and solidifying. This is a road construction method for laying the shallow improved soil layer 13.
By wet mixing, dust generation by powder at the construction site is suppressed, and the environment in the vicinity of the site is not contaminated with powder. In addition, the wet mixing method does not require compaction, and variation in quality can be reduced.
[0012]
The invention according to claim 7 is the invention according to

claim

1, 4, 5 or 6, wherein the additive is made of foam beads or rice husk, the additive is made of a bubble generator, and the additive or additive is either One or both of them are road construction methods that are one or more low-density bodies selected from the group consisting of foam beads, rice husks, and bubble generators.
By adding a low-density material as an additive or additive, the shallow improved soil layer 13 can be reduced in weight, and the static load caused by the shallow improved soil layer can be reduced. Moreover, since the low density body absorbs vibration due to a dynamic load, the amount of dynamic consolidation settlement can be reduced.
[0013]
The invention according to claim 8 is the invention according to

claim

1, 4, 5, or 6, wherein the additive is a clinker formed by incineration of industrial waste.
According to this construction method, it is possible to effectively use a clinker that is formed by incineration of industrial waste and is difficult to dispose of.
[0014]
The invention according to claim 9 is the invention according to

claim

1, 4, 5 or 6, and is a road construction method in which the additive is an inorganic fiber or a synthetic fiber.
By adding the above fibers as an additive, the shallow improved soil layer 13 is reinforced, cracking of the improved ground due to traffic load is prevented, and the durability of the improved ground is improved. Further, even if the layer thickness is made thinner than that of the shallow improved soil layer not containing fibers, durability equivalent to that of the shallow improved soil layer not containing fibers can be obtained.
[0015]
The invention according to claim 10 is the invention according to any one of claims 1 to 3 or 5, and is a road construction method in which the columnar body 20 is a ready-made pile or a ground improvement columnar body. By using ready-made piles for the columnar body, construction can be carried out at a lower cost in a shorter construction period, and by using the ground improved columnar body, consolidation consolidation of the road can be prevented more reliably.
[0016]
The invention according to claim 11 is the invention according to any one of claims 1 to 3 or 5 as shown in FIG. 5, wherein the columnar body 20 is a ground improvement columnar body. This is a road construction method having a node portion 20b in a trunk portion 20a.
By providing the node portion 20b in the trunk portion of the ground improvement columnar body, the settlement resistance of the ground improvement columnar body is increased, and the consolidation settlement of the road can be prevented more reliably.
[0017]
The invention according to claim 12 is the invention according to any one of claims 1 to 3, 5 or 11 as shown in FIG. 6, wherein the columnar body 20 is a ground improvement columnar body, and this columnar body. This is a road construction method in which the tip of 20 has an enlarged portion 20c having a diameter larger than that of the trunk portion 20a.
By providing the enlarged portion 20c having a diameter larger than that of the trunk portion at the tip of the ground improvement columnar body, the settlement resistance force of the ground improvement columnar body is increased, and the consolidation settlement of the road can be prevented more reliably.
[0018]
The invention according to claim 13 is the invention according to any one of claims 1 to 3, 5, 11, or 12, wherein the columnar body 20 is a ground improvement columnar body, and the columnar body 20 is an inorganic fiber or a synthetic fiber. This is a road construction method that contains fiber.
By including the fiber in the columnar body, even if the columnar body is cracked due to the lateral flow of the soft ground, the bending resistance of the columnar body is exhibited and the subsequent lateral flow can be suppressed.
[0019]
The invention according to claim 14 is the invention according to any one of claims 1 to 3, 5 or 11 to 13, wherein the columnar body 20 is a ground improvement columnar body, and the columnar body 20 is mechanically stirred. Or it is the construction method of the road constructed | assembled by the high pressure jet stirring method.
By constructing the ground improved columnar body by the mechanical stirring method, the outer diameter of the improved body can be built at a low price regardless of the soil quality. In addition, by constructing the ground improvement columnar body by the high-pressure jet stirring method, the construction machine can be reduced in size and weight, and can be constructed even in a narrow place or under an existing hanging plate.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The present invention constructs a columnar body that does not reach the support layer below the soft ground on the soft ground, and the reinforcing net or shallow improved soil layer or the reinforcing net and shallow improved soil layer are formed on the columnar body. Both are laid. When adopting the above combination, the value L, which is the length of the columnar body and the thickness of the road pavement plus the thickness of the shallow improved soil layer, is used to suppress consolidation settlement due to traffic load, that is, dynamic load. It is a big condition. If the improvement rate of the columnar body is constructed in the range of 10 to 50% and the value L is set to 4 m or more, consolidation settlement due to dynamic load can be substantially eliminated. Here, the improvement rate of the columnar body means the percentage of the cross-sectional area of the columnar body in the unit area of the improved ground when the columnar body is viewed from above as shown in FIGS. 7 and 8. If the improvement rate of the columnar body is less than 10%, consolidation settlement cannot be sufficiently suppressed, and if it exceeds 50%, there is a problem that the construction period and the construction cost are increased. Preferably the improvement is 15-30%.
[0021]
Although the value L is required to be 4 m or more, even if it is increased, the effect of suppressing the dynamic consolidation settlement does not increase so much. However, as the value L increases, the effect of suppressing static consolidation settlement increases accordingly. In the present invention, in order to avoid excessive ground improvement, the lower end of the columnar body does not reach the support layer 16 below the soft ground 11 as shown in FIGS. Although the support layer is not shown in FIG. 1, the columnar body 20 does not reach the support layer as well. The maximum value of this value L is appropriately determined in consideration of the layer thickness of the soft ground and its degree of softness, load conditions, economy, and the like. As shown in FIG. 2, when the road pavement 18 is applied directly on the reinforcing net 21 without providing the shallow improvement soil layer, it is necessary to increase the improvement rate of the columnar body 20.
As shown in FIGS. 2 to 4, in the step elimination method when a long columnar body is constructed in the vicinity of the underground structure and a shorter columnar body is constructed step by step as the distance from the underground structure increases, it is efficient and economical. Therefore, the conditions for ground improvement in the vicinity of the underground structure are the same as in the case of improvement over the entire road length shown in FIG. 1, and the length of the columnar body gradually decreases as the distance from the underground structure increases. The difference is that it becomes zero at the end.
[0022]
1, 2, and 4, the reinforcing network 21 of the present invention is a network formed of a material such as inorganic fiber, synthetic fiber, synthetic resin, or steel. A net-like body made of inorganic fiber or synthetic fiber is a string-like body made from this fiber and made from the net. Examples of inorganic fibers include glass fibers, and examples of synthetic fibers include polyamide-based nylon fibers, polyolefin-based polyethylene fibers, and polypropylene fibers. Examples of the synthetic resin include polyethylene and polypropylene resin. A net-like body made of steel is formed by pulling both edges of a plate-shaped steel in a direction perpendicular to the cuts, after making a number of cuts parallel to the plate-like steel, leaving a peripheral edge. The mesh spacing of the mesh body is 10 to 200 mm. Depending on the required degree of reinforcement, the reinforcing mesh body is used as a single sheet or a plurality of sheets are used in combination.
[0023]
The shallow improved soil layer 13 of the present invention shown in FIGS. 1, 3 and 4 is composed of earth and sand, solidified material such as powder or slurry cement, cement-based solidified material, quicklime, etc., and additive or additive. Either one or both are mixed uniformly and solidified. Depending on the water content of the target ground, there may be a case where a shallow improved soil layer is formed by mixing and compacting, or a case where the shallow ground improvement soil layer is formed without compaction. When the moisture content of the target ground is low, if a slurry-like solidifying material is used and either or both of the additive and / or additive are further added to the solidified material and the earth and wet-mixed, the powder at the construction site The generation of dust is suppressed and the environment in the vicinity of the site is not contaminated with powder.
[0024]
Examples of the additive of the present invention include low-density bodies such as foam beads and rice husks, clinker formed by incineration of industrial waste, inorganic fibers, and synthetic fibers. The additive of the present invention includes a bubble generator. The above additives or additives may be added alone or in combination of two or more. You may mix an additive and an additive. The expanded beads are added in an amount of 20 to 50% by volume based on 100% by volume of the material forming the shallow improved soil layer. If it is less than 20% by volume, the purpose of addition cannot be achieved, and if it exceeds 50% by volume, the strength of the shallow improved soil layer when solidified decreases. By adding the low-density body, the shallow improved soil layer is reduced in weight, the static consolidation settlement can be reduced, the elastic modulus of the shallow improved soil layer is reduced, and the dynamic load due to traffic load is absorbed. . Accordingly, even if the length of the columnar body is shortened, consolidation settlement can be prevented.
[0025]
Examples of the low-density bubble generator include polyoxyethylene alkyl ether compounds and higher alcohol sulfate compounds. This bubble generator is a liquid before mixing, but is a substance that entrains bubbles in the layer when forming a shallow improved soil layer. When the rice husk is made of a low density body, the rice husk is made of SiO. ₂ Because it contains a large amount, the corrosion resistance is high, and the resistance to the traffic load is large in order to increase the shear strength of the shallow improved soil layer over the long term from its shape.
When a clinker having a diameter of 5 mm or less formed by incineration of industrial waste is used as an additive, a clinker that is in need of this disposal can be used effectively.
[0026]
When inorganic fiber or synthetic fiber is used as an additive, it is preferably an inorganic fiber such as steel fiber having a length of about 2 to 4 cm, or a polyamide-type nylon fiber, a polyolefin-type polyethylene fiber, or a polypropylene fiber having a length of about 4 to 7 cm. A synthetic fiber consisting of If the length is less than the above lower limit value, the reinforcing effect is poor, and if the length exceeds the above upper limit value, it becomes difficult to handle when mixing with other materials. By adding the fiber as an additive, the shallow improved soil layer is reinforced, cracking of the improved ground due to traffic load is prevented, and durability of the improved ground is improved. Further, even if the layer thickness is made thinner than that of the shallow improved soil layer not containing fibers, durability equivalent to that of the shallow improved soil layer not containing fibers can be obtained.
In order to achieve the above object, rice husks, inorganic fibers or synthetic fibers are 0.1 to 5.0% by volume, preferably 0.2 to 2% with respect to 100% by volume of the material forming the shallow improved soil layer. 0.0% by volume is added, and the clinker is added at 30% by volume or less. The bubble generator is added in an amount of 0.01 to 1.0% by weight, preferably 0.1 to 0.5% by weight, based on 100% by weight of the material forming the shallow improved soil layer.
[0027]
There are two methods for constructing a columnar body: a method of driving a prefabricated pile such as a wooden pile, a prefabricated concrete pile, a steel pile or the like into a deep ground, and a method of constructing a ground improved columnar body. By using ready-made piles for the columnar body, construction can be carried out at a lower cost in a shorter construction period, and by using the ground improved columnar body, consolidation consolidation of the road can be prevented more reliably. There are two methods for constructing this soil-improved columnar body: mechanical stirring and high-pressure jet stirring.However, when the ground-improved columnar body is constructed by mechanical stirring, it is inexpensive and has a constant outer diameter regardless of the soil quality. can do. Moreover, by constructing by a high-pressure jet stirring method, the construction machine can be reduced in size and weight, and can be constructed even in a narrow place or under an existing tread plate. When constructing this ground improvement columnar body, the node part 20b can also be formed in the trunk | drum 20a of the ground improvement columnar body 20, as shown in FIG. As a result, the frictional force on the peripheral surface of the ground improvement columnar body is increased, the settlement resistance is increased, and the consolidation settlement of the road can be prevented more reliably. There is also an advantage that it is difficult to generate a lateral flow of the soft ground. Moreover, when constructing a ground improvement columnar body, an enlarged portion 20c having a diameter larger than that of the trunk portion 20a can be formed at the tip of the ground improvement columnar body 20, as shown in FIG. Thereby, the settlement resistance of the ground improvement columnar body is further increased, and the consolidation settlement of the road can be prevented more reliably.
[0028]
Furthermore, the ground improvement columnar body 20 can also contain an inorganic fiber or a synthetic fiber. In this case, steel fibers having a length of about 2 to 4 cm are preferably used for the inorganic fibers, and polyamide-type nylon fibers, polyolefin-type polyethylene fibers and polypropylene fibers having a length of about 4 to 7 cm are used for the synthetic fibers. If the length is less than the above lower limit value, the reinforcing effect is poor, and if the length exceeds the above upper limit value, it becomes difficult to handle when mixing with other materials. This fiber contains about 0.2-2.0 volume% with respect to all the materials which form a ground improvement columnar body. By including the fiber in the columnar body, even if the columnar body is cracked due to the lateral flow of the soft ground, the bending resistance of the columnar body is exhibited and the subsequent lateral flow can be suppressed.
[0029]
By constructing the columnar body, lateral flow of the ground due to dynamic load can be prevented. A method of constructing the columnar body when viewed from above will be described with reference to FIGS. Considering the construction efficiency and economy, the planar arrangement of the columnar bodies should be a grid arrangement as shown in FIG. 7 or a non-contact type staggered arrangement as shown in FIG. It is preferable to suppress. When the improvement rate is in the range of 10 to 50% and the lattice arrangement shown in FIG. ₁ (However, lattice spacing d ₁ ≧ lattice spacing d ₂ ) Is less than twice the height from the top of the columnar body to the road pavement, and also when the non-contact staggered arrangement shown in FIG. , When the road direction is D, the columnar spacing d _Three (However, columnar spacing d _Three ≧ Distance between columnar bodies d _Four ) Is less than twice the height from the upper end of the columnar body to the road pavement surface, the static load and the dynamic load are reliably transmitted to the columnar body, respectively, and the lateral flow of the ground can be sufficiently prevented. it can.
[0030]
As shown in FIGS. 1-4, the road pavement 18 of this invention consists of the crusher run layer 18a, the particle size adjustment crushed stone layer 18b, and asphalt concrete 18c. 1 to 4, the crusher run layer 18a is laid to a thickness of 5 to 15 cm, the particle size-adjusted crushed stone layer 18b is laid to a thickness of 10 to 30 cm, and the asphalt concrete 18c is laid to a thickness of 10 to 40 cm. .
[0031]
【Example】
Next, examples of the present invention will be described based on the drawings together with comparative examples.
<Example 1>
As shown in FIG. 1, the ground improved columnar body 20 was constructed on the target soft ground 11 by a mechanical stirring method so as not to reach the support layer below the soft ground 11. At this time, each columnar body has a diameter a of 80 cm and a length L. _Four Is 400 cm and the distance d shown in FIG. _Three , D _Four Were constructed in a non-contact staggered arrangement with 125 cm and an improvement rate of 25.7%, respectively.
A reinforcing net-like body 21 made of glass fiber is laid on the ground improvement columnar body 20, and cement powder is added to the excavated soil and separately prepared earth and sand, and a rice husk which is a low-density body is further added as an additive. After adding 20% by weight of the entire material, dry mixing, and then compacting the shallow improved soil layer 13 by L _Five = Laying to a thickness of 60 cm. A crusher run layer 18a was laid on this to a thickness of 30 cm, a particle size-adjusted crushed stone layer 18b was further laid on the thickness of 10 cm, and the asphalt concrete 18b having a thickness of 5 cm was paved thereon. The total length L shown in FIG. 1 was 505 cm.
<Comparative Example 1>
As shown in FIG. 9, the same soft ground 1 as in Example 1 is excavated, a cement-based solidifying material is added to the excavated soil and separately prepared soil, dry-mixed, and then compacted by compaction. The soil layer 2a was laid to a thickness of 60 cm. After the crusher run layer 3a was provided on this to a thickness of 30 cm, a crushed stone layer 3b for adjusting the particle size was further laid on the thickness of 10 cm, and the asphalt concrete 4 having a thickness of 5 cm was paved thereon. . The total length L shown in FIG. 9 was 105 cm.
<Comparative example 2>
As shown in FIG. 10, the same soft ground 1 as in Example 1 is excavated, and quick lime is added as a solidifying material to the excavated soil and separately prepared sand, and after dry mixing, the shallow layer is improved by compaction. The soil layer 2b was laid to a thickness of 150 cm. Fe lime was dry-mixed on the shallow improved soil layer 2b and then solidified to form a shallow improved soil layer 2c having a thickness of 30 cm. After providing the crusher run layer 3a to a thickness of 30 cm on the shallow improved soil layer 2c, a crushed stone layer 3b for adjusting the particle size is further laid to a thickness of 10 cm, and a thickness of 5 cm is provided thereon. Paved with asphalt concrete 4. The total length L shown in FIG. 10 was 225 cm.
<Example 2>
As shown in FIG. 2, after excavating the same soft ground 11 as in the first embodiment and supporting the underdrain which is the underground structure 12 on the support layer 16 via the support pile 17, the target soft ground in the vicinity of the underdrain 11, a ground improvement columnar body 20 having a diameter a of 80 cm was constructed by a mechanical stirring method so as not to reach the support layer 16 below the soft ground 11. At this time, the ground improvement columnar body 20 was constructed so that the columnar body gradually shortened as it moved away from the culvert. The length L of the columnar body closest to the culvert ₇ Is 400 cm, and the columnar body has an interval d shown in FIG. ₁ , D ₂ Were constructed in a non-contact staggered arrangement with 125 cm and an improvement rate of 25.7%, respectively.
A reinforcing mesh body 21 made of glass fiber is laid on the ground improvement columnar body 20, a crusher run layer 18a is laid thereon to a thickness of 30 cm, and a particle size-adjusted crushed stone layer 18b is further formed thereon to a thickness of 10 cm. And then paved with 5 cm thick asphalt concrete 18c. Depth L from the lower end of the longest ground improvement columnar body shown in FIG. ₆ Was 20 m and the overall length L was 445 cm.
<Example 3>
As shown in FIG. 3, the same soft ground 11 as in Example 1 is excavated, and after the underdrain 12 is supported by the support layer 16 in the same manner as in Example 2, mechanical agitation is applied to the soft ground 11 in the vicinity of the underdrain. Thus, the ground improvement columnar body 20 having a diameter a of 80 cm was constructed in such a manner that the columnar body was gradually shortened as it moved away from the underdrain as in Example 2, and the length did not reach the support layer 16 below the soft ground 11. . The length L of the columnar body closest to the culvert ₉ Is 400 cm, and the columnar body has an interval d shown in FIG. _Three , D _Four Were constructed in a non-contact staggered arrangement with 125 cm and an improvement rate of 25.7%, respectively.
On the ground improvement columnar body 20, a slurry-like cement-based solidifying material is added to excavated soil and separately prepared sand, and further, 30% by volume of low-density foam beads are added as an additive, and wet mixing is performed. L shallow shallow improved soil layer 13 _Ten = Laying to a thickness of 30 cm. A crusher run layer 18a was laid on this to a thickness of 30 cm, a particle size-adjusted crushed stone layer 18b was further laid on the thickness of 10 cm, and the asphalt concrete 18c having a thickness of 5 cm was paved thereon. Depth L from the lower end of the longest ground improvement columnar body shown in FIG. ₈ Was 20 m and the overall length L was 475 cm.
<Example 4>
As shown in FIG. 4, the same soft ground 11 as in Example 1 is excavated, and after the underdrain 12 is supported on the support layer 16 in the same manner as in Example 2, mechanical agitation is applied to the soft ground 11 near the underdrain. Thus, the ground improvement columnar body 20 having a diameter a of 80 cm was constructed in such a manner that the columnar body gradually shortened as it moved away from the underdrain as in Example 2, and had a length that did not reach the support layer 16 below the soft ground 11. . The length L of the columnar body closest to the culvert ₁₂ Is 400 cm, and the columnar body has an interval d shown in FIG. _Three , D _Four Were constructed in a non-contact staggered arrangement with 125 cm and an improvement rate of 25.7%, respectively.
A reinforcing net-like body 21 made of glass fiber is laid on the ground improvement columnar body 20, and cement powder is added to the excavated soil and separately prepared earth and sand, and a rice husk which is a low-density body is further added as an additive. After adding 20% by volume of the entire material, dry mixing, and then compacting, the shallow improved soil layer 13 can be reduced to L ₁₃ = Laying to a thickness of 30 cm. A crusher run layer 18a was laid on this to a thickness of 30 cm, a particle size-adjusted crushed stone layer 18b was further laid on the thickness of 10 cm, and the asphalt concrete 18c having a thickness of 5 cm was paved thereon. Depth L from the lower end of the longest ground improvement columnar body shown in FIG. ₁₁ Was 20 m and the overall length L was 475 cm.
<Comparative Example 3>
As shown in FIG. 11, after excavating the same soft ground 1 as in Example 1 and supporting the underdrain 6 on the support layer 7 through the support pile 8 in the same manner as in Example 2, the soft ground near this underdrain is shown. The ground 1 was excavated, and a cement-based solidifying material was added to the excavated soil and separately prepared sand, mixed dry, and then compacted to lay the shallow improved soil layer 2a to a thickness of 60 cm. After the crusher run layer 3a was provided on this to a thickness of 30 cm, a crushed stone layer 3b for adjusting the particle size was further laid on the thickness of 10 cm, and the asphalt concrete 4 having a thickness of 5 cm was paved thereon. . The total length L shown in FIG. 11 was 105 cm.
<Comparative example 4>
As shown in FIG. 12, the same soft ground 1 as in Example 1 is excavated, and after the underdrain 6 is supported by the support layer 7 through the support pile 8 in the same manner as in Example 2, the soft ground near this underdrain is shown. The ground 1 was excavated, and quick lime was added as a solidifying material to this excavated soil and separately prepared sand, and after dry mixing, the shallow improved soil layer 2b was laid to a thickness of 150 cm by compaction. Fe lime was dry-mixed on the shallow improved soil layer 2b and then solidified to form a shallow improved soil layer 2c having a thickness of 30 cm. After providing the crusher run layer 3a to a thickness of 30 cm on the shallow improved soil layer 2c, a crushed stone layer 3b for adjusting the particle size is further laid to a thickness of 10 cm, and a thickness of 5 cm is provided thereon. Paved with asphalt concrete 4. The total length L shown in FIG. 12 was 225 cm.
<Comparative Example 5>
3 except that the ground improvement columnar body 20 shown in FIG. 3 is lengthened and the lower end of the columnar body is embedded in the support layer 16 below the soft ground (not shown). Improved ground.
<Comparison test and results>
About the amount of subsidence of roads and the state of occurrence of steps formed by various methods of Examples 1 to 4 and Comparative Examples 1 to 5, until the start of use after construction, Until 720 days elapse. Moreover, about the construction cost required for road construction, when Example 1 was set to 100, the approximate value of another Example and a comparative example was investigated. These results are shown in Table 1.
[0032]
[Table 1]

[0033]
(a) About the amount of subsidence and the occurrence of steps:
As is apparent from Table 1, both the road constructed by the construction method of Example 1 and the road constructed by the construction method of Comparative Examples 1 and 2 are both subsidized by static load until the use is started. There was no significant difference between the construction method of Example 1 and the construction methods of Comparative Examples 1 and 2. However, after the road was used, due to dynamic load, the amount of road subsidence by the method of Comparative Examples 1 and 2 was large, whereas the amount of road subsidence by the method of Example 1 was small. .
[0034]
Moreover, when a columnar body is constructed in the vicinity of a culvert that is an underground structure, both the road constructed by the construction method of Examples 2 to 4 and the road constructed by the construction method of Comparative Example 5 are used until the start of use. The amount of subsidence due to static load was small, the step A shown in FIGS. 11 and 12 was not seen, and no significant difference was found between the construction methods of Examples 2 to 4 and the construction method of Comparative Example 5. . Also, it could not be said that there was a significant difference among the three examples.
However, the road constructed by the construction methods of Comparative Examples 3 and 4 has a relatively large subsidence amount due to static load until the start of use. Between the construction methods of other Examples 2 to 4 and the construction method of Comparative Example 5 A significant difference was observed. In addition, since the road was used, the amount of subsidence of the road by the method of Comparative Examples 3 and 4 was remarkably large due to the dynamic load, and the level difference A appeared clearly. The amount of subsidence of the road by the construction method of Comparative Example 5 was all small, and no steps were generated. Among the roads according to the construction methods of Examples 2 to 4, in particular, Examples 2 and 3 had a relatively small subsidence and showed values comparable to Comparative Example 5.
(b) About construction cost:
When the construction cost of the construction method of Example 1 is set to 100, the estimated value of the construction cost of each of the other construction methods of Examples 2 to 4 is higher than the estimated value of the construction cost of each construction method of Comparative Examples 1 to 4 having a large amount of subsidence. However, it was a low value of about 20% to about 27% of the estimated cost of the method of Comparative Example 5 in which the lower end of the columnar body was embedded in the support layer.
[0035]
【The invention's effect】
As described above, according to the present invention, a road can be constructed inexpensively in a relatively short construction period without excessive ground improvement that unnecessarily prolongs the construction period, and is constructed by embankment on soft ground. When a road is used, consolidation settlement due to dynamic load can be suppressed.
In addition, when a road crossing over underground structures such as underdrains provided on soft ground is used, a step is generated at the boundary between the upper part of the road underground structure and the adjacent part. There is an excellent effect that never happens.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view seen from a direction perpendicular to a road direction constructed by a construction method according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view seen from a direction perpendicular to the road direction constructed by the construction method of Embodiment 2 of the present invention.
FIG. 3 is a cross-sectional view seen from a direction perpendicular to the road direction constructed by the construction method of Embodiment 3 of the present invention.
FIG. 4 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Example 4 of the present invention.
FIG. 5 is a front view of a ground improvement columnar body having a node portion in a trunk portion of the present invention.
FIG. 6 is a front view of a ground improvement columnar body having an enlarged portion at the tip of the present invention.
FIG. 7 is a plan view of a ground improvement columnar body arranged in a lattice shape of the present invention.
FIG. 8 is a plan view of a ground improvement columnar body arranged in a non-contact type staggered pattern according to the present invention.
9 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Comparative Example 1. FIG.
10 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Comparative Example 2. FIG.
11 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Comparative Example 3. FIG.
12 is a cross-sectional view seen from a direction orthogonal to the road direction constructed by the construction method of Comparative Example 4. FIG.
[Explanation of symbols]
11 Soft ground
12 Underground structures
13 Shallow improved soil layer
16 Support layer
17 Support pile
18 Road paving
18a Crusher run layer
18b Particle size-adjusted crushed stone layer
18c Asphalt and concrete
20 Columnar body
20a trunk
20b node
20c Enlarged part
21 Reinforcing mesh

Claims

道路基礎の軟弱地盤(11)に複数本の柱状体(20)を前記軟弱地盤(11)の下方の支持層に到達しない長さでかつ１０〜５０％の改良率で構築し、前記複数本の柱状体(20)の上に補強用網状体(21)を敷設し、前記補強用網状体(21)の上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層(13)を敷設し、前記浅層改良土層(13)の上に道路舗装(18)を構築することを特徴とする道路の構築工法。A plurality of columnar bodies (20) are constructed on a soft ground (11) of a road foundation with a length that does not reach the support layer below the soft ground (11) and an improvement rate of 10 to 50%. A reinforcing mesh (21) is laid on the columnar body (20), and one or both of an additive or an additive is further added to the earth and sand and the solidifying material on the reinforcing mesh (21). A road construction method characterized in that a shallow improved soil layer (13) is laid by mixing and solidifying and a road pavement (18) is constructed on the shallow improved soil layer (13).

道路基礎の軟弱地盤(11)に埋設され沈下を抑制された地下構造物(12)の近傍の前記軟弱地盤(11)に複数本の柱状体(20)を前記軟弱地盤(11)の下方の支持層(16)に到達しない長さで前記地下構造物(12)から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、前記複数本の柱状体(20)の上に補強用網状体(21)を敷設し、前記地下構造物(12)及び補強用網状体(21)の上に道路舗装(18)を構築することを特徴とする道路の構築工法。A plurality of columnar bodies (20) are placed below the soft ground (11) on the soft ground (11) in the vicinity of the underground structure (12) buried in the soft ground (11) of the road foundation and subsidized. It is constructed with an improvement rate of 10 to 50% so as to gradually shorten as it moves away from the underground structure (12) with a length that does not reach the support layer (16), and is formed on the plurality of columnar bodies (20). A road construction method characterized by laying a reinforcing mesh (21) and constructing a road pavement (18) on the underground structure (12) and the reinforcing mesh (21).

道路基礎の軟弱地盤(11)に埋設され沈下を抑制された地下構造物(12)の近傍の前記軟弱地盤(11)に複数本の柱状体(20)を前記軟弱地盤(11)の下方の支持層(16)に到達しない長さで前記地下構造物(12)から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、前記複数本の柱状体(20)の上に土砂と固化材を混合して固化することにより浅層改良土層(13)を敷設し、前記地下構造物(12)及び浅層改良土層(13)の上に道路舗装(18)を構築することを特徴とする道路の構築工法。A plurality of columnar bodies (20) are placed below the soft ground (11) on the soft ground (11) in the vicinity of the underground structure (12) buried in the soft ground (11) of the road foundation and subsidized. It is constructed with an improvement rate of 10 to 50% so as to gradually shorten as it moves away from the underground structure (12) with a length that does not reach the support layer (16), and is formed on the plurality of columnar bodies (20). A shallow improved soil layer (13) is laid by mixing and solidifying the earth and sand, and a road pavement (18) is constructed on the underground structure (12) and the shallow improved soil layer (13). A road construction method characterized by

土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層(13)を敷設する請求項３記載の道路の構築工法。The road construction method according to claim 3, wherein the shallow soil improvement soil layer (13) is laid by further adding one or both of an additive or an additive to the earth and sand and the solidifying material, and mixing and solidifying.

道路基礎の軟弱地盤(11)に埋設され沈下を抑制された地下構造物(12)の近傍の前記軟弱地盤(11)に複数本の柱状体(20)を前記軟弱地盤(11)の下方の支持層(16)に到達しない長さで前記地下構造物(12)から遠ざかるに従って段々に短くなるように１０〜５０％の改良率で構築し、前記複数本の柱状体(20)の上に補強用網状体(21)を敷設し、前記補強用網状体(21)の上に土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて混合して固化することにより浅層改良土層(13)を敷設し、前記地下構造物(12)及び浅層改良土層(13)の上に道路舗装(18)を構築することを特徴とする道路の構築工法。A plurality of columnar bodies (20) are placed below the soft ground (11) on the soft ground (11) in the vicinity of the underground structure (12) buried in the soft ground (11) of the road foundation and subsidized. It is constructed with an improvement rate of 10 to 50% so as to gradually shorten as it moves away from the underground structure (12) with a length that does not reach the support layer (16), and is formed on the plurality of columnar bodies (20). A reinforcing mesh (21) is laid, and by adding one or both of additive or additive to earth and sand and solidifying material on the reinforcing mesh (21), the mixture is solidified to be shallow. A road construction method characterized by laying a layer improvement soil layer (13) and constructing a road pavement (18) on the underground structure (12) and the shallow layer improvement soil layer (13).

土砂と固化材に添加材又は添加剤のいずれか一方又は双方を更に加えて湿式混合して固化することにより浅層改良土層(13)を敷設する請求項１、４又は５記載の道路の構築工法。The road according to claim 1, 4 or 5, wherein the shallow improvement soil layer (13) is laid by further adding one or both of an additive or an additive to the earth and sand and the solidifying material and wet-mixing and solidifying. Construction method.

添加材が発泡ビーズ又は籾殻からなり、添加剤が気泡発生体からなり、前記添加材又は添加剤のいずれか一方又は双方が発泡ビーズ、籾殻及び気泡発生体からなる群より選ばれた１種又は２種以上の低密度体である請求項１、４、５又は６記載の道路の構築工法。The additive is made of foam beads or rice husks, the additive is made of bubble generators, and either one or both of the additives or additives are selected from the group consisting of foam beads, rice husks and bubble generators or The road construction method according to claim 1, wherein the road construction method is two or more kinds of low-density bodies.

添加材が産業廃棄物の焼却により形成されたクリンカである請求項１、４、５又は６記載の道路の構築工法。The road construction method according to claim 1, 4, 5, or 6, wherein the additive is a clinker formed by incineration of industrial waste.

添加材が無機繊維又は合成繊維である請求項１、４、５又は６記載の道路の構築工法。The road construction method according to claim 1, 4, 5, or 6, wherein the additive is an inorganic fiber or a synthetic fiber.

柱状体(20)が既製杭又は地盤改良柱状体である請求項１ないし３又は５いずれか１項に記載の道路の構築工法。The road construction method according to any one of claims 1 to 3 or 5, wherein the columnar body (20) is a ready-made pile or a ground improvement columnar body.

柱状体(20)が地盤改良柱状体であって、前記柱状体(20)の胴部(20a)に節部(20b)を有する請求項１ないし３又は５いずれか１項に記載の道路の構築工法。The road body according to any one of claims 1 to 3 or 5, wherein the columnar body (20) is a ground improvement columnar body, and the body (20a) of the columnar body (20) has a node (20b). Construction method.

柱状体(20)が地盤改良柱状体であって、前記柱状体(20)の先端が胴部(20a)より大径の拡大部(20c)を有する請求項１ないし３、５又は１１いずれか１項に記載の道路の構築工法。The columnar body (20) is a ground improvement columnar body, and the tip of the columnar body (20) has an enlarged portion (20c) larger in diameter than the trunk portion (20a). The road construction method according to item 1.

柱状体(20)が地盤改良柱状体であって、前記柱状体(20)が無機繊維又は合成繊維を含む請求項１ないし３、５、１１又は１２いずれか１項に記載の道路の構築工法。The road construction method according to any one of claims 1 to 3, 5, 11, or 12, wherein the columnar body (20) is a ground improvement columnar body, and the columnar body (20) includes an inorganic fiber or a synthetic fiber. .

柱状体(20)が地盤改良柱状体であって、前記柱状体(20)を機械撹拌法又は高圧噴射撹拌法により構築する請求項１ないし３、５、又は１１ないし１３いずれか１項に記載の道路の構築工法。The columnar body (20) is a ground improvement columnar body, and the columnar body (20) is constructed by a mechanical stirring method or a high-pressure jet stirring method, according to any one of claims 1 to 3, 5, or 11 to 13. Road construction method.