JP2004124620A - Method for reforming excavated sediment - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、泥土圧シールド工法により生じた掘削土砂の性状を改質するための方法に関する。
【０００２】
【従来の技術】
トンネル工事において用いられる泥土圧シールド工法を、バインダー分が少ない砂礫等の硬質地盤等に適用する場合は、当該工法によって発生する掘削土砂は、カッターヘッドの回転のみでは容易に塑性流動化できないため、高粘度の塑性流動化用添加材を切羽に注入することにより、掘削土砂の塑性流動性を高めて切羽の安定性を図っている。
【０００３】
一方、前記作業により発生した掘削土砂は処分場等に搬出しなければならないが、塑性流動化しているために、箱ダンプやタンクダンプを用いて搬出していることが多く、平ダンプを用いて搬出する場合は、掘削土砂にセメント系固化材を混合撹拌して固化処理する作業が必要となる。
【０００４】
このとき、掘削土砂に対して、塑性流動化用添加材を２５容量％〜３５容量％混練するとともに、さらに、前記混練後の掘削土砂の総容量に対して、１０容量％〜１５容量％の固化材を添加する必要がある。
そのため、処理を行う掘削土砂量は、当初の掘削土砂量の１５０％（容積比）以上となってしまい、環境破壊等の元凶と見られている建設副産物を増加させてしまうこととなっていた。
また、塑性流動化用添加材により塑性流動化された掘削土砂に固化材を添加して処理しなければならないため、処理工程が複雑となり、処理費用が増大していた。
【０００５】
そこで、本願出願人等は、塑性流動化用添加材を含む掘削土砂にゲル化剤を混合することにより、当該掘削土砂を砂礫と泥土に分別して処理を行うことを可能とした技術を提案した（特許文献１参照）。
【０００６】
【特許文献１】
特開平１１−３０３５７１号公報（第２頁−第５頁）
【０００７】
【発明が解決しようとする課題】
しかし、前記出願では、塑性流動化用添加材を含む掘削土砂にゲル化剤を混合する場合において、掘削土砂のｐＨ（水素イオン濃度）について特別な考慮を図らなかったことから、当該ｐＨの状態によっては、良好な結果が得られない場合が生じてしまうことがあった。
【０００８】
本発明は、前記の問題点を解決するためになされたものであり、泥土圧シールド工法により生じた掘削土砂の性状をさらに良好に改質するための方法を提供することを目的としている。
【０００９】
【課題を解決するための手段】
前記課題を解決するために、本発明の掘削土砂の改質方法は、シールド掘削機前方の切羽に、水溶性高分子化合物である塑性流動化用添加材を送出して、掘削土砂と混合攪拌しながら切羽面を掘削する泥土式シールド工法において、前記掘削により生じた掘削土砂を搬出する途中で、前記掘削土砂に水素イオン濃度調整剤を添加して、前記掘削土砂のｐＨを８．２以上（８．２乃至１４．０）として、前記掘削土砂のスランプ値を低減させる（好ましくは０乃至１の範囲とする）ことを特徴としている。
ここで、ｐＨ調整剤とは、掘削土砂をアルカリ性にする作用を奏するための物質である。
【００１０】
また、前記掘削土砂の改質方法において、前記塑性流動化用添加材と、前記水素イオン濃度調整剤の組み合わせを、下記の（１）又は（２）であることとすれば好適である。
（１）前記塑性流動化用添加材としてのグアガムと、前記水素イオン濃度調整剤としてのホウ砂、ホウ酸又はアルミン酸ソーダ。
（２）前記塑性流動化用添加材としてのカルボキシメチルセルロースと、前記水素イオン濃度調整剤としてのアルミニウム化合物（加里ミョウバン、ポリ塩化アルミニウム、硫酸バンド等）。
【００１１】
また、前記掘削土砂の改質方法において、前記塑性流動化用添加材を前記掘削土砂の１００容量部に対して、１０容量部乃至３５容量部の範囲内で添加するとともに、前記水素イオン濃度調整剤を、前記掘削土砂の１容量部に対して、０．０５容量部乃至０．１５容量部の範囲内で添加することとすれば好適である。
【００１２】
【発明の実施の形態】
以下、本発明の好適な実施の一形態について、前記塑性流動化用添加材としてグアガムを、前記水素イオン濃度調整剤として、ホウ砂等を使用した場合を例として、詳細に説明する。
【００１３】
本発明の掘削土砂の改質方法は、シールド掘削機前方の切羽に、単体でも粘性の発生が活発な水溶性高分子化合物である塑性流動化用添加材を送出して、掘削土砂と混合攪拌しながら切羽面を掘削する泥土式シールド工法において発生する掘削土砂の性状を改質するための方法であり、以下の点を特徴としている。
すなわち、前記掘削により生じた掘削土砂を搬出する途中において、前記掘削土砂に水素イオン濃度調整剤を添加して、前記掘削土砂のｐＨを８．２乃至１４．０として、前記掘削土砂のスランプ値を０〜１程度に低減させる方法である。
【００１４】
このとき、前記塑性流動化用添加材を前記掘削土砂の１００容量部に対して、１０容量部乃至３５容量部の範囲内で添加するとともに、前記水素イオン濃度調整剤を、前記掘削土砂の１容量部に対して、０．０５容量部乃至０．１５容量部の範囲で添加することが好適である。
ここで、塑性流動化用添加材は、０．５重量％乃至３．０重量％の濃度である水溶液とすることが好適である。その理由は、０．５重量％未満であると低粘性となり固化に必要な粘性を確保できず、３．０重量％より多すぎると高粘性となり撹拌装置から分離することができないことから、各種実験から好適となる範囲を定めたものである。
【００１５】
なお、塑性流動化用添加材の添加量は、対象となる掘削土砂の組成により変わってくるものであり、ほとんどが砂礫分の場合には塑性流動化用添加材の添加量を多くする必要があり（３０容量部〜３５容量部程度）、粘土分を含む場合には塑性流動化用添加材の添加量を少なくすることができる（１０容量部〜３０容量部程度）（後記第３実施例参照）。
【００１６】
本発明の原理は、以下の通りである。
塑性流動化用添加材と混練された掘削土砂（以下、「被改質掘削土砂」という）は、主として水分の存在によって塑性流動化しており、そのｐＨは中性域である。
この被改質掘削土砂に、水素イオン濃度調整剤（以下、「ｐＨ調整剤」という）を添加することにより、当該被改質掘削土砂のｐＨをアルカリ域（８．２以上に変化させることで、前記塑性流動化の原因となっている水分の粘性を架橋させて塑性流動化用添加材を増粘させる。これにより当該被改質掘削土砂が固化した状態になる。
【００１７】
その結果として、塑性流動化している被改質掘削土砂の見かけの水分が減少するとともに、アルカリ性に変化した塑性流動化用添加材は高粘性な性状を呈する（以下、「ゲル化」ということがある）こととなり、この高粘性による粘着力が前記被改質掘削土砂の土粒子を結合させることで、当該被改質掘削土砂が普通土に近似した性質に改質されることになる。
【００１８】
このような被改質掘削土砂の改質度合いを数値的に表現する指標としては、スランプ値を用いることが好適であるが、処理後の被改質掘削土砂（以下、「処理掘削土砂」という）のスランプ値は０〜１程度になり、普通土と同様に平ダンプ等にて搬出することが可能な性状に改質されることとなる。
さらに、前記掘削土砂に適量の固化材（セメント系固化材又はスラグ系固化材等）を加えることにより、コーン指数を改良することができる。なお、コーン指数は４００ｋＮ／ｍ２以上にすることが処理掘削土砂を盛土等に使用するためには好ましい。
【００１９】
ここで、前記塑性流動化用添加材は、切羽の安定性と、掘削土砂の流動性を図るために加える物質であり、水溶性高分子化合物（植物性天然粘質物）であるグアガム等が用いられる。
このとき、前記塑性流動化用添加材にグアガムを用いた場合には、ｐＨ調整剤にはホウ砂（ボラックス）、ホウ酸又はアルミン酸ソーダの少なくとも１種類を用いることが好適である。
なお、前記ｐＨ調整剤は、被改質掘削土砂のｐＨを調整可能であるとともに、ゲル化剤としての役割をも果たしている。
【００２０】
なお、被改質掘削土砂にｐＨ調整剤を添加して混合攪拌する作業は、当該被改質掘削土砂をシールド掘進機のチャンバから坑外へ搬出する過程のうち、いずれかの段階で行うことができれば目的とする効果を達成することができるため、施工現場の状況に応じて、各種の方法（例えば、チャンバと接続されているスクリューコンベアの中間部に、輸送管を接続することにより、スクリューコンベア内で行う方法等）を採用することが可能である。
【００２１】
本発明の掘削土砂の改質方法によれば、塑性流動化用添加材のｐＨを所定値となるように調節することで、当該塑性流動化用添加材固化材としての役割を担わせて、掘削土砂の改質を行うことができる。従って、セメント系固化材等を使用しない場合であっても掘削土砂の改質を行うことができるため、処理を行うための残土の発生量を約１５容量％〜２０容量％程度低減させることができる。
【００２２】
また、塑性流動化用添加材が混練されている被改質掘削土砂に、ｐＨ調整剤を添加混合して、ｐＨをアルカリ域に調整することで、当該被改質掘削土砂を改質することができることから、当該ｐＨ調整剤を添加するための設備が小規模で済むため、処理費用の低減を図ることができる。なお、掘削土砂にセメント系固化材のみを添加して改質を行った場合と比較して、材料費を約１５％程度安価とすることができるとともに、処理掘削土砂の体積を減少させることにより、従来比で２５％〜３０％程度の残土処理費の低減を図ることができる。
【００２３】
以上、本発明について、好適な実施形態の一例を説明した。しかし、本発明は、前記実施形態に限られず、前記の各構成要素については、本発明の趣旨を逸脱しない範囲で、適宜設計変更が可能であることは言うまでもない。
【００２４】
なお、本発明を適用した処理掘削土砂に、強酸又は弱酸（希硫酸、クエン酸、りんご酸、マイレン酸等）を加えてｐＨを８．２未満にすることで、水分の架橋を解除して、土砂と水分を分離させることも可態である（この分離方法は、砂礫分を主要成分としている掘削土砂に特に有効である）。
【００２５】
【実施例】
次に、本発明の掘削土砂の改質方法についての有効性を確認するために、以下の各種実証実験を行った。
【００２６】
［第１実施例］
塑性流動化用添加材のｐＨに応じた粘性の変化を調べるため、塑性流動化用添加材（グアガム溶液）に、添加量を変化させてｐＨ調整剤（ホウ砂溶液）を添加して、その性状を観察した（配合は表１参照）。
【００２７】
【表１】
この結果によれば、ｐＨ調整剤の添加量を増やすことに伴い塑性流動化用添加材のｐＨ値が高くなり、ｐＨ値が８．２以上でゲル化して粘性が増加することが明らかになった（表２参照）。
【００２９】
【表２】
［第２実施例］
さらに、塑性流動化用添加材のｐＨによる粘性の変化を調べるため、塑性流動化用添加材（グアガム溶液）に、添加量を変化させてｐＨ調整剤（ホウ砂溶液）を添加して、その性状を観察した（配合は表３参照）。
【００３１】
【表３】
この結果によれば、ｐＨ調整剤の添加量を更に増やすことにより塑性流動化用添加材のｐＨが高くなり、それに伴って、粘性が増加することが明らかになった（表４参照）。
従って、第１実施例及び第２実施例によれば、ｐＨが中性である塑性流動化用添加材にｐＨ調整剤を添加して、そのｐＨを８．２以上に調節することで固化材としての粘性を確保できることが証明された。
【００３３】
なお、ｐＨ値が９．０（ｐＨ調整剤を１５０ｍｌ添加した場合）を超えた場合には、塑性流動化用添加材のゲルそのものはしっかりしているが、凝集作用により内部の水分が放出されることにより、粘性の低下が見られる結果となった。これは、一塊になった塑性流動化用添加材のゲルと実験容器の間の摩擦抵抗が放出水により低下したことによるものであり、水素イオン濃度による粘性の低下ではないと思慮される。
【００３４】
【表４】
また、結果は示さないが、塑性流動化用添加材としてＣＭＣを用い、ｐＨ調整剤としてアルミニウム化合物を適量添加した場合についても、前記第１実施例及び第２実施例と同様な結果が得られた。
【００３６】
［第３実施例］
本発明を適用した場合における処理土の性状を調べるために、表５に示す配合により、実験対象土砂に塑性流動化用添加材（グアガム溶液）とｐＨ調整剤（粉末ホウ砂）を添加し、当該塑性流動化用添加材の混練直後と、ｐＨ調整剤の添加直後のスランプ値を計測した。
なお、実験対象土砂には洗い砂を使用し、必要に応じて、バインダー分としての粉末粘土を加えた。
【００３７】
【表５】
この結果によれば、ｐＨ調整剤の添加直後のスランプ値は１．０以下となり、平ダンプ等で搬出可能な性状に改質されていることが明らかになった（表６参照）。
【００３９】
【表６】
［第４実施例］
第３実施例でｐＨ調整剤を添加した実験対象土砂に、さらに、適量の固化材を加えた場合における改質土の性状を分析した。使用した固化材はスラグセメントと高炉セメントの２種類であり、高炉セメントを用いた場合には希硫酸を添加した（配合は表７参照）。
【００４１】
【表７】
この結果によれば、実験番号４−１の場合を除いて、コーン指数は３００（ｋＮ／ｍ２）を超えており（４００（ｋＮ／ｍ２）近傍）、盛土材料等に転用可能な性状に改質されていることが明らかになった（表８参照）。従って、塑性流動化用添加材とｐＨ調整剤を加えた実験対象土砂に、さらに、適量の固化材を添加することが有効であることが証明された（なお、塑性流動化用添加材の濃度を増加させることにより、又は、高炉セメントを加えることにより、コーン指数は大きくなり、強度が増加することが明らかになった）。
【００４３】
【表８】
【発明の効果】
本発明によれば、泥土圧シールド工法により生じた掘削土砂の性状を、簡易かつ容易に改質することが可能となり、当該掘削土砂の処理費用の低減を効果的に図ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for modifying properties of excavated earth and sand generated by a mud pressure shield method.
[0002]
[Prior art]
If the mud pressure shield method used in tunnel construction is applied to hard ground such as gravel with a small binder content, the excavated earth and sand generated by the method cannot be easily plasticized and fluidized only by rotating the cutter head. By injecting a high-viscosity plastic fluidizing additive into the face, the plastic fluidity of the excavated earth and sand is enhanced, and the face is stabilized.
[0003]
On the other hand, the excavated earth and sand generated by the work must be carried out to a disposal site, etc., but because of plastic fluidization, it is often carried out using a box dump or a tank dump. In the case of carrying out, it is necessary to mix and stir a cement-based solidifying material into excavated earth and sand to perform a solidification treatment.
[0004]
At this time, 25% to 35% by volume of the plastic fluidizing additive is kneaded with the excavated earth and sand, and 10% to 15% by volume of the total volume of the excavated earth and sand after kneading. It is necessary to add a solidifying material.
For this reason, the amount of excavated sediment to be processed is more than 150% (volume ratio) of the original excavated sediment amount, and construction by-products that are considered to be the cause of environmental destruction are to be increased. .
In addition, the solidification material must be added to the excavated earth and sand that has been plastically fluidized by the plastic fluidization additive, and the solidification material must be added.
[0005]
Therefore, the applicants of the present application have proposed a technology that enables the excavated earth and sand to be separated into gravel and mud by mixing a gelling agent into the excavated earth and sand containing the additive for plastic fluidization and performing a treatment. (See Patent Document 1).
[0006]
[Patent Document 1]
JP-A-11-303571 (pages 2 to 5)
[0007]
[Problems to be solved by the invention]
However, in the above-mentioned application, when the gelling agent is mixed with the excavated earth and sand containing the additive for plastic fluidization, no special consideration is given to the pH (hydrogen ion concentration) of the excavated earth and sand. In some cases, good results may not be obtained.
[0008]
The present invention has been made to solve the above problems, and has as its object to provide a method for further improving the properties of excavated earth and sand generated by a mud pressure shield method.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the method for modifying excavated earth and sand according to the present invention comprises: sending an additive for plastic fluidization, which is a water-soluble polymer compound, to a face in front of a shield excavator; In the mud-type shield construction method of excavating the face while excavating the excavated sediment, a hydrogen ion concentration adjusting agent is added to the excavated sediment while carrying out the excavated sediment generated by the excavation, so that the pH of the excavated earth and sand is 8.2 or more. (8.2 to 14.0), characterized in that the slump value of the excavated earth and sand is reduced (preferably in the range of 0 to 1).
Here, the pH adjuster is a substance having an effect of making excavated earth and sand alkaline.
[0010]
In the method for modifying excavated earth and sand, it is preferable that the combination of the additive for plastic fluidization and the hydrogen ion concentration modifier is the following (1) or (2).
(1) Gua gum as the plastic fluidizing additive and borax, boric acid or sodium aluminate as the hydrogen ion concentration regulator.
(2) Carboxymethylcellulose as the plastic fluidizing additive and an aluminum compound (Kali alum, polyaluminum chloride, sulfate band, etc.) as the hydrogen ion concentration regulator.
[0011]
In the method for modifying excavated earth and sand, the plastic fluidizing additive is added within a range of 10 to 35 parts by volume with respect to 100 parts by volume of the excavated earth and sand, and the hydrogen ion concentration adjustment is performed. It is preferable that the agent is added in the range of 0.05 to 0.15 parts by volume with respect to 1 part by volume of the excavated earth and sand.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to an example in which guar gum is used as the plastic fluidizing additive and borax or the like is used as the hydrogen ion concentration regulator.
[0013]
In the method for modifying excavated earth and sand according to the present invention, an additive for plastic fluidization, which is a water-soluble polymer compound that is highly viscous even in a single body, is sent to a face in front of a shield excavator, and the excavated earth and sand are mixed and stirred. This is a method for improving the properties of excavated earth and sand generated in the mud shield method in which the face is excavated while performing the excavation, and has the following features.
That is, a hydrogen ion concentration adjusting agent is added to the excavated earth and sand while the excavated earth and sand generated by the excavation is being carried out to adjust the pH of the excavated earth and sand to 8.2 to 14.0. Is reduced to about 0 to 1.
[0014]
At this time, the plastic fluidizing additive is added within a range of 10 parts by volume to 35 parts by volume with respect to 100 parts by volume of the excavated earth and sand, and the hydrogen ion concentration modifier is added to the excavated earth and sand by 1%. It is preferable to add 0.05 to 0.15 parts by volume to the volume part.
Here, the plastic fluidizing additive is preferably an aqueous solution having a concentration of 0.5% by weight to 3.0% by weight. The reason is that if it is less than 0.5% by weight, the viscosity becomes low and the viscosity required for solidification cannot be secured. If it is more than 3.0% by weight, it becomes highly viscous and cannot be separated from the stirring device. The preferred range was determined from experiments.
[0015]
The amount of the plastic fluidizing additive depends on the composition of the excavated earth and sand, and when most of the material is gravel, it is necessary to increase the amount of the plastic fluidizing additive. Yes (approximately 30 parts by volume to 35 parts by volume), and when a clay component is included, the amount of the plastic fluidizing additive can be reduced (approximately 10 parts by volume to 30 parts by volume) (third embodiment described later) reference).
[0016]
The principle of the present invention is as follows.
Excavated earth and sand mixed with the additive for plastic fluidization (hereinafter referred to as “modified excavated earth and sand”) is plastically fluidized mainly due to the presence of moisture, and its pH is in a neutral region.
By adding a hydrogen ion concentration adjuster (hereinafter, referred to as a “pH adjuster”) to the modified excavated soil, the pH of the modified excavated earth is changed to an alkaline region (8.2 or more). Then, the viscosity of the water causing the plastic fluidization is crosslinked to thicken the plastic fluidizing additive, whereby the excavated soil to be modified is solidified.
[0017]
As a result, the apparent water content of the plasticized fluidized excavated excavated soil decreases, and the plastic fluidizing additive that has changed to alkaline exhibits a highly viscous property (hereinafter referred to as "gelation"). That is, the adhesive force due to the high viscosity binds the soil particles of the excavated soil to be modified, so that the excavated soil to be modified is modified to a property close to that of ordinary soil.
[0018]
It is preferable to use a slump value as an index for numerically expressing the degree of modification of the excavated sediment to be modified, but it is preferable to use a slump value. The slump value of ()) is about 0 to 1, and is modified to a property that can be carried out by flat dumping or the like, similarly to ordinary soil.
Further, the cone index can be improved by adding an appropriate amount of a solidifying material (such as a cement-based solidifying material or a slag-based solidifying material) to the excavated earth and sand. It is preferable that the cone index be 400 kN / m 2 or more in order to use the processed excavated earth and sand for embankment and the like.
[0019]
Here, the plastic fluidizing additive is a substance added to achieve stability of the face and fluidity of excavated earth and sand, and guar gum or the like, which is a water-soluble polymer compound (vegetable natural mucilage), is used. Can be
At this time, when guar gum is used as the plastic fluidizing additive, it is preferable to use at least one of borax, boric acid, and sodium aluminate as the pH adjuster.
The pH adjuster is capable of adjusting the pH of the excavated soil to be modified, and also has a role as a gelling agent.
[0020]
In addition, the operation of adding the pH adjuster to the excavated soil to be modified and mixing and mixing the same should be performed at any stage in the process of carrying the excavated soil to be modified out of the chamber of the shield machine. Can achieve the desired effect if possible, depending on the situation of the construction site, various methods (for example, by connecting a transport pipe to the middle of the screw conveyor connected to the chamber, A method performed in a conveyor).
[0021]
According to the method for modifying the excavated earth and sand of the present invention, by adjusting the pH of the plastic fluidizing additive to a predetermined value, by acting as a plastic fluidizing additive solidifying material, The excavated soil can be modified. Therefore, the excavated earth and sand can be modified even when a cement-based solidification material or the like is not used, so that the amount of residual soil generated for the treatment can be reduced by about 15% to 20% by volume. it can.
[0022]
Further, by adding and mixing a pH adjuster to the excavated soil to be modified in which the additive for plastic fluidization is kneaded, and adjusting the pH to an alkaline range, the excavated soil to be modified is modified. Therefore, the equipment for adding the pH adjuster can be reduced in scale, so that the processing cost can be reduced. The material cost can be reduced by about 15% as compared with the case where only the cement-based solidifying material is added to the excavated soil and modified, and the volume of the processed excavated sand is reduced. In addition, it is possible to reduce the remaining soil treatment cost by about 25% to 30% as compared with the related art.
[0023]
In the foregoing, an example of the preferred embodiment has been described for the present invention. However, the present invention is not limited to the above-described embodiment, and it goes without saying that the design of each of the above-described components can be appropriately changed without departing from the spirit of the present invention.
[0024]
In addition, by adding a strong acid or a weak acid (dilute sulfuric acid, citric acid, malic acid, maleic acid, etc.) to the treated excavated earth and sand to which the present invention is applied to adjust the pH to less than 8.2, the crosslinking of water is released. It is also feasible to separate the soil and water (this separation method is particularly effective for excavated sediment whose main component is gravel).
[0025]
【Example】
Next, in order to confirm the effectiveness of the method for modifying excavated earth and sand of the present invention, the following various verification experiments were performed.
[0026]
[First embodiment]
In order to examine the change in viscosity according to the pH of the plastic fluidizing additive, the pH adjusting agent (borax solution) was added to the plastic fluidizing additive (guar gum solution) by changing the amount of addition. The properties were observed (see Table 1 for formulation).
[0027]
[Table 1]
According to this result, it is clear that the pH value of the plastic fluidizing additive increases with an increase in the amount of the pH adjuster added, and that the viscosity increases when the pH value is 8.2 or more. (See Table 2).
[0029]
[Table 2]
[Second embodiment]
Further, in order to examine the change in viscosity due to the pH of the plastic fluidizing additive, the pH adjusting agent (borax solution) was added to the plastic fluidizing additive (guar gum solution) by changing the amount of addition. The properties were observed (see Table 3 for formulation).
[0031]
[Table 3]
According to this result, it was clarified that the pH of the plastic fluidizing additive was increased by further increasing the amount of the pH adjuster, and the viscosity was increased accordingly (see Table 4).
Therefore, according to the first embodiment and the second embodiment, by adding a pH adjuster to a plastic fluidizing additive having a neutral pH and adjusting the pH to 8.2 or more, the solidified material is obtained. It has been proved that the viscosity can be ensured.
[0033]
When the pH value exceeds 9.0 (when 150 ml of the pH adjuster is added), the gel itself of the plastic fluidizing additive is firm, but the internal water is released due to the coagulation action. This resulted in a decrease in viscosity. This is due to the fact that the frictional resistance between the lump of the plastic fluidizing additive gel and the experimental vessel was reduced by the released water, and is not considered to be a decrease in viscosity due to the hydrogen ion concentration.
[0034]
[Table 4]
Although the results are not shown, the same results as those of the first and second examples can be obtained when CMC is used as an additive for plastic fluidization and an appropriate amount of an aluminum compound is added as a pH adjuster. Was.
[0036]
[Third embodiment]
In order to investigate the properties of the treated soil when the present invention is applied, a plastic fluidizing additive (guar gum solution) and a pH adjuster (powder borax) were added to the experimental soil by the formulation shown in Table 5, Slump values were measured immediately after kneading the plastic fluidizing additive and immediately after adding the pH adjuster.
Washing sand was used as the soil for the experiment, and powdered clay was added as a binder if necessary.
[0037]
[Table 5]
According to this result, the slump value immediately after the addition of the pH adjuster was 1.0 or less, and it was clarified that the slump value was modified to a property that can be carried out by flat dumping or the like (see Table 6).
[0039]
[Table 6]
[Fourth embodiment]
In the third example, the properties of the modified soil in the case where an appropriate amount of the solidifying material was further added to the soil to be tested to which the pH adjuster was added were analyzed. The solidification materials used were two types, slag cement and blast furnace cement. When blast furnace cement was used, dilute sulfuric acid was added (for the blending, see Table 7).
[0041]
[Table 7]
According to this result, the cone index exceeds 300 (kN / m 2 ) (near 400 (kN / m 2 )) except for the case of Experiment No. 4-1, and the properties that can be diverted to embankment materials and the like (See Table 8). Therefore, it was proved that it was effective to further add an appropriate amount of the solidifying material to the test soil to which the plastic fluidizing additive and the pH adjuster were added (the concentration of the plastic fluidizing additive was not limited). It was found that by increasing the slag, or by adding blast furnace cement, the cone index increased and the strength increased).
[0043]
[Table 8]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to modify easily and easily the property of the excavated earth and sand produced by the mud pressure shield construction method, and it is possible to effectively reduce the processing cost of the excavated earth and sand.
Claims (3)
前記掘削により生じた掘削土砂を搬出する途中で、前記掘削土砂に水素イオン濃度調整剤を添加して、前記掘削土砂のｐＨを８．２以上として、前記掘削土砂のスランプ値を低減させることを特徴とする掘削土砂の改質方法。In the mud-type shield construction method, a plastic fluidizing additive, which is a water-soluble polymer compound, is sent to the face in front of the shield excavator, and the face is excavated while mixing and stirring with the excavated earth and sand.
In the course of unloading the excavated sediment generated by the excavation, adding a hydrogen ion concentration adjusting agent to the excavated sediment to adjust the pH of the excavated sediment to 8.2 or more and reduce the slump value of the excavated sediment. Characteristic method of excavated earth and sand.
（１）前記塑性流動化用添加材としてのグアガムと、前記水素イオン濃度調整剤としてのホウ砂、ホウ酸又はアルミン酸ソーダ。
（２）前記塑性流動化用添加材としてのカルボキシメチルセルロースと、前記水素イオン濃度調整剤としてのアルミニウム化合物。The method for modifying excavated earth and sand according to claim 1, wherein a combination of the plastic fluidizing additive and the hydrogen ion concentration modifier is the following (1) or (2).
(1) Gua gum as the plastic fluidizing additive and borax, boric acid or sodium aluminate as the hydrogen ion concentration regulator.
(2) Carboxymethyl cellulose as the plastic fluidizing additive and an aluminum compound as the hydrogen ion concentration regulator.
前記水素イオン濃度調整剤を、前記掘削土砂の１容量部に対して、０．０５容量部乃至０．１５容量部の範囲内で添加することを特徴とする請求項１又は請求項２に記載の掘削土砂の改質方法。While adding the plastic fluidizing additive to 100 parts by volume of the excavated earth and sand within a range of 10 parts by volume to 35 parts by volume,
The said hydrogen ion concentration modifier is added within the range of 0.05 volume part-0.15 volume part with respect to 1 volume part of the said excavated earth and sand, The Claim 1 or Claim 2 characterized by the above-mentioned. Of excavated earth and sand.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2020055984A (en) * | 2018-10-04 | 2020-04-09 | 株式会社大林組 | Mud-added material |
| CN114320322A (en) * | 2021-12-23 | 2022-04-12 | 中交第二航务工程局有限公司 | Weathered granite stratum earth pressure balance shield muck improvement method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2020055984A (en) * | 2018-10-04 | 2020-04-09 | 株式会社大林組 | Mud-added material |
| JP7127466B2 (en) | 2018-10-04 | 2022-08-30 | 株式会社大林組 | Addition material |
| CN114320322A (en) * | 2021-12-23 | 2022-04-12 | 中交第二航务工程局有限公司 | Weathered granite stratum earth pressure balance shield muck improvement method |
| CN114320322B (en) * | 2021-12-23 | 2023-07-21 | 中交第二航务工程局有限公司 | Method for improving earth pressure balance shield residue soil of weathered granite stratum |
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