JP2021056021A - Quality evaluation method for improved ground - Google Patents
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Abstract
Description
本発明は、改良地盤の品質評価方法に関する。 The present invention relates to a method for evaluating the quality of improved ground.
固化材を用いた地盤改良工事における品質管理方法としては、改良後の地盤（以下、「改良地盤」ともいう。）からボーリングによってコアを採取し、採取されたコアの強度（例えば、一軸圧縮強さ）を実際に測定して改良の効果を確認して、地盤改良の施工条件を適宜変更する方法等が挙げられる。
特許文献１には、地盤改良の実施工に先立ち、現場土試料に対して、固化材の設計添加量に対して複数の増量された固化材を添加した試験体を作製し、該試験体に対してせん断波速度と強度とを求める室内試験を行ってせん断波速と強度との関係を定式化して回帰曲線を求め、該回帰曲線に、改良直後の改良地盤で求めたせん断波速度値を適用して当該改良地盤の強度を把握して改良効果確認を行うようにしたことを特徴とするセメント改良地盤の品質管理試験方法が記載されている。該方法によれば、早期に改良地盤の強度（一軸圧縮強さ）の数値を推定することができる。
As a quality control method in ground improvement work using a solidifying material, cores are collected by boring from the improved ground (hereinafter, also referred to as "improved ground"), and the strength of the collected cores (for example, uniaxial compressive strength). The method of actually measuring the above) to confirm the effect of the improvement and appropriately changing the construction conditions for the ground improvement can be mentioned.
In Patent Document 1, prior to the ground improvement work, a test body in which a plurality of solidifying materials increased with respect to the design addition amount of the solidifying material was prepared for the on-site soil sample, and the test body was used. On the other hand, an laboratory test to determine the shear wave velocity and intensity was performed to formulate the relationship between the shear wave velocity and intensity to obtain a regression curve, and the shear wave velocity value obtained from the improved ground immediately after the improvement was applied to the regression curve. The quality control test method for the improved cement ground is described, which is characterized in that the strength of the improved ground is grasped and the improvement effect is confirmed. According to this method, the numerical value of the strength (uniaxial compressive strength) of the improved ground can be estimated at an early stage.
改良地盤から採取されたコアの強度は、該コアが採取された箇所によって、その大きさにばらつきが生じることがある。この原因として、固化材と改良の対象となる地盤の混合の程度が十分ではなかったこと等が考えられる。しかし、固化材と地盤が十分に混合されているかどうかを判断することは困難である。
本発明の目的は、改良地盤の品質（例えば、固化材と地盤の混合の程度等）の評価を行うことができる方法を提供することである。
The strength of the core collected from the improved ground may vary in size depending on the location where the core was collected. It is considered that the cause of this is that the degree of mixing between the solidifying material and the ground to be improved was not sufficient. However, it is difficult to determine if the solidifying material and the ground are well mixed.
An object of the present invention is to provide a method capable of evaluating the quality of improved ground (for example, the degree of mixing of solidifying material and ground).
本発明者は、上記課題を解決するために鋭意検討した結果、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る工程と、改良地盤をボーリングして、コア体を得る工程と、コア体を、Ｘ線ＣＴを用いて分析し、コア体のＣＴ値に関するデータを得る工程と、ＣＴ値に関するデータを用いて、改良地盤の品質を評価する工程を含む方法によれば、上記目的を達成できることを見出し、本発明を完成した。
すなわち、本発明は、以下の［１］〜［５］を提供するものである。
［１］ 地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る第一の地盤改良工程と、上記改良地盤をボーリングして、コア体を得るボーリング工程と、上記コア体を、Ｘ線ＣＴを用いて分析し、上記コア体のＣＴ値に関するデータを得る第一の分析工程と、上記ＣＴ値に関するデータを用いて、上記改良地盤の品質を評価する評価工程を含むことを特徴とする改良地盤の品質評価方法。
［２］ 上記ＣＴ値に関するデータが、ＣＴ値の分布画像であり、上記評価工程において、上記ＣＴ値の分布画像を用いて、上記地盤改良材と上記改良の対象となる地盤の混合の程度を評価する前記［１］に記載の改良地盤の品質評価方法。
As a result of diligent studies to solve the above problems, the present inventor obtains a core body by mixing the ground improvement material and the ground to be improved to obtain the improved ground and boring the improved ground. According to the method including a step, a step of analyzing the core body using X-ray CT to obtain data on the CT value of the core body, and a step of evaluating the quality of the improved ground using the data on the CT value. , The present invention has been completed by finding that the above object can be achieved.
That is, the present invention provides the following [1] to [5].
[1] The first ground improvement step of mixing the ground improvement material and the ground to be improved to obtain the improved ground, the boring step of boring the improved ground to obtain the core body, and the core body. Includes a first analysis step of analyzing using X-ray CT to obtain data on the CT value of the core body, and an evaluation step of evaluating the quality of the improved ground using the data on the CT value. A characteristic quality evaluation method for improved ground.
[2] The data related to the CT value is a distribution image of the CT value, and in the evaluation step, the degree of mixing of the ground improvement material and the ground to be improved is determined by using the distribution image of the CT value. The quality evaluation method for the improved ground according to the above [1] to be evaluated.
［３］ 上記第一の地盤改良工程の前に、改良の対象となる地盤から得られた土を含み、かつ、地盤改良材の添加量が異なる２つ以上の試験体を作製する試験体作製工程と、上記試験体を、Ｘ線ＣＴを用いて分析し、上記試験体のＣＴ値に関するデータを得る第二の分析工程と、上記試験体の品質に関するデータを従属変数とし、上記試験体のＣＴ値に関するデータを独立変数として、回帰分析を行って、上記試験体の品質の予測式を作成する予測式作成工程を行い、上記評価工程において、上記コア体のＣＴ値に関するデータと、上記予測式を用いて、上記コア体の品質に関するデータの予測値を得た後、該予測値に基いて、上記改良地盤の品質を評価する前記［１］または［２］に記載の改良地盤の品質評価方法。
［４］ 上記品質に関するデータが、地盤改良材の添加量、改良地盤の一軸圧縮強さ、透水係数、ｐＨ、及び改良地盤からの重金属類の溶出量から選ばれる１種以上である前記［３］に記載の改良地盤の品質評価方法。
［５］ 前記［１］〜［４］のいずれかに記載の改良地盤の品質評価方法によって、上記改良地盤の品質を評価した後、該評価の結果に基づいて、地盤の改良条件を調整する調整工程と、調整した地盤の改良条件に基いて、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る第二の地盤改良工程を含む改良地盤の品質管理方法。
[3] Prior to the first ground improvement step, preparation of two or more test specimens containing soil obtained from the ground to be improved and having different amounts of ground improvement materials added is prepared. The process, the second analysis step of analyzing the test piece using X-ray CT to obtain data on the CT value of the test piece, and the data on the quality of the test piece as the dependent variables of the test piece. Regression analysis is performed using the data related to the CT value as an independent variable, and a prediction formula creation step for creating a prediction formula for the quality of the test piece is performed. In the evaluation step, the data related to the CT value of the core body and the prediction are performed. The quality of the improved ground according to the above [1] or [2], in which the quality of the improved ground is evaluated based on the predicted value after obtaining the predicted value of the data relating to the quality of the core body by using the formula. Evaluation method.
[4] The above quality data is one or more selected from the amount of ground improvement material added, the uniaxial compressive strength of the improved ground, the hydraulic conductivity, the pH, and the amount of heavy metals eluted from the improved ground. ] The quality evaluation method of the improved ground described in.
[5] After evaluating the quality of the improved ground by the quality evaluation method of the improved ground according to any one of [1] to [4], the ground improvement conditions are adjusted based on the evaluation result. A quality control method for improved ground including a second ground improvement step of mixing the ground improvement material and the ground to be improved based on the adjustment process and the adjusted ground improvement conditions to obtain the improved ground.
本発明の改良地盤の品質評価方法によれば、改良地盤の品質（例えば、地盤改良材と地盤の混合の程度等）を評価することができる。
することができる。
According to the quality evaluation method of the improved ground of the present invention, the quality of the improved ground (for example, the degree of mixing of the ground improving material and the ground) can be evaluated.
can do.
本発明の改良地盤の品質評価方法は、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る第一の地盤改良工程と、改良地盤をボーリングして、コア体を得るボーリング工程と、コア体を、Ｘ線ＣＴを用いて分析し、コア体のＣＴ値に関するデータを得る第一の分析工程と、ＣＴ値に関するデータを用いて、改良地盤の品質を評価する評価工程を含むものである。
以下、各工程を詳細に説明する。
The quality evaluation method of the improved ground of the present invention includes a first ground improvement step of mixing the ground improvement material and the ground to be improved to obtain the improved ground, and boring to obtain the core body by boring the improved ground. The process, the first analysis step of analyzing the core body using X-ray CT to obtain data on the CT value of the core body, and the evaluation step of evaluating the quality of the improved ground using the data on the CT value. It includes.
Hereinafter, each step will be described in detail.
［第一の地盤改良工程］
本工程は、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る工程である。
本明細書中、「地盤改良材」とは、地盤の固化（強度の向上）、地盤中の重金属類の不溶化、地盤中の空洞または空隙の充填等の、地盤の改良を目的として地盤と混合される材料である。
地盤改良材の例としては、セメントを母材とし、石膏、高炉スラグ微粉末、石炭灰（フライアッシュ）、石灰石微粉末、シリカフューム等の各種有効成分を添加したセメント系固化材；軽焼マグネシア、軽焼マグネシアの部分水和物等の酸化マグネシウム含有物や、水酸化マグネシウム含有物等のマグネシウム系不溶化材；硫酸第一鉄、硫酸第二鉄、ポリ硫酸第二鉄等の硫酸鉄塩や、硫酸アルミニウム、硫酸アルミニウムカリウム、硫酸アルミニウムナトリウム等の硫酸アルミニウム塩等の金属硫酸塩系不溶化材；塩化第一鉄、塩化第二鉄等の塩化鉄塩や、ポリ塩化アルミニウム等の塩化アルミニウム塩等の金属塩化物系不溶化材；水ガラス等が挙げられる。
地盤改良材の種類及び量は、特に限定されるものではなく、一般的な地盤改良材から、改良の対象となる地盤（土壌）の性状に応じて適宜定めればよい。
地盤改良材と改良の対象となる地盤を混合する際の、地盤改良材の形態は、スラリー、粉体、粒体、グラウト等のいずれであってもよい。なお、地盤改良材の形態によって、第一の分析工程においてＸ線ＣＴを用いて分析されるコア体のＣＴ値の数値が変化する。
[First ground improvement process]
This step is a step of mixing the ground improvement material and the ground to be improved to obtain the improved ground.
In the present specification, the "ground improvement material" is mixed with the ground for the purpose of improving the ground such as solidification of the ground (improvement of strength), insolubilization of heavy metals in the ground, filling of cavities or voids in the ground, etc. It is a material to be used.
Examples of ground improvement materials are cement-based solidifying materials that use cement as the base material and add various active ingredients such as gypsum, blast furnace slag fine powder, coal ash (fly ash), limestone fine powder, and silica fume; light-baked magnesia, Magnesium oxide-containing substances such as partial hydrates of light-baked magnesia and magnesium-based insolubilizers such as magnesium hydroxide-containing substances; ferrous sulfate, ferric sulfate, ferric sulfate such as polyferrous sulfate, and iron sulfates. Metallic sulfate-based insolubilizers such as aluminum sulfates such as aluminum sulfate, potassium aluminum sulfate and sodium aluminum sulfate; iron chloride salts such as ferric chloride and ferric chloride, and aluminum chloride salts such as polyaluminum chloride. Metal chloride-based insolubilizer; water glass and the like can be mentioned.
The type and amount of the ground improvement material are not particularly limited, and may be appropriately determined from a general ground improvement material according to the properties of the ground (soil) to be improved.
When mixing the ground improvement material and the ground to be improved, the form of the ground improvement material may be any of slurry, powder, granules, grout and the like. Depending on the form of the ground improvement material, the numerical value of the CT value of the core body analyzed by using X-ray CT in the first analysis step changes.
本工程において、地盤改良材と改良の対象となる地盤を混合する方法としては、特に限定されるものではない。例えば、地盤改良材をスラリーの形態で用いる場合には、トレンチャー撹拌機、ロータリー式撹拌機、ツインヘッダ等を用いて混合する方法や、深層混合処理工法における、各種機械攪拌（スラリー撹拌）工法、各種高圧噴射工法、各種機械攪拌併用型高圧噴射工法に従って混合する方法等が挙げられる。
また、地盤改良材を粉体又は粒体の形態で用いる場合には、バックホウバケット、スケルトンバケット等を用いて混合する方法や、深層混合処理工法における、各種機械攪拌（粉体噴射撹拌）工法に従って混合する方法等が挙げられる。
また、グラウト等の流動性を有する液体（薬液）の形態で、地盤改良材を混合（注入）する方法としては、各種薬液注入工法に従って混合（注入）する方法等が挙げられる。
なお、本明細書中、地盤改良材の混合には、地盤改良材の注入が含まれるものとする。
In this step, the method of mixing the ground improvement material and the ground to be improved is not particularly limited. For example, when the ground improvement material is used in the form of a slurry, a method of mixing using a trencher stirrer, a rotary stirrer, a twin header, etc., or various mechanical stirring (slurry stirring) methods in the deep mixing processing method, Examples thereof include various high-pressure injection methods and a method of mixing according to various mechanical stirring combined high-pressure injection methods.
When the ground improvement material is used in the form of powder or granules, it follows a method of mixing using a backhoe bucket, a skeleton bucket, etc., or various mechanical stirring (powder injection stirring) methods in the deep layer mixing treatment method. Examples include a method of mixing.
Further, as a method of mixing (injecting) the ground improvement material in the form of a fluid (chemical solution) having fluidity such as grout, a method of mixing (injecting) according to various chemical solution injection methods and the like can be mentioned.
In the present specification, the mixing of the ground improvement material shall include the injection of the ground improvement material.
［ボーリング工程］
本工程は、地盤改良工程によって得られた改良地盤をボーリングして、コア体を得る工程である。
ボーリングによって採取されるコア体（改良地盤の一部）の大きさや形状は、Ｘ線ＣＴ装置を用いて分析する際に支障がない大きさであればよいが、通常、直径３〜１０ｃｍ、高さが５〜１５ｃｍの円柱状である。また、改良地盤の一軸圧縮強さを「ＪＩＳ Ａ １２１６：２００９（土の一軸圧縮試験方法）」に準拠して測定する目的で改良地盤から採取した供試体を、一軸圧縮強さを測定する前に、本発明において使用してもよい。
[Bowling process]
This step is a step of boring the improved ground obtained by the ground improvement step to obtain a core body.
The size and shape of the core body (a part of the improved ground) collected by boring may be a size that does not hinder analysis using an X-ray CT device, but is usually 3 to 10 cm in diameter and high. It is a columnar shape with a diameter of 5 to 15 cm. In addition, before measuring the uniaxial compressive strength of the specimen collected from the improved ground for the purpose of measuring the uniaxial compressive strength of the improved ground in accordance with "JIS A 1216: 2009 (uniaxial compressive test method of soil)". In addition, it may be used in the present invention.
［第一の分析工程］
本工程は、ボーリング工程で得られたコア体を、Ｘ線ＣＴを用いて分析し、コア体のＣＴ値に関するデータを得る工程である。
分析は、市販のＸ線ＣＴ装置を用いて行えばよい。
コア体のＣＴ値に関するデータの例としては、Ｘ線ＣＴ装置によって撮影された、コア体のＣＴ値の分布画像、該画像から得られるＣＴ値と頻度の関係を示したＣＴ値ヒストグラム、上記画像または上記ＣＴ値ヒストグラムから得られる特定の値、上記画像から得られるＣＴ値の標準偏差の数値等が挙げられる。
[First analysis process]
This step is a step of analyzing the core body obtained in the boring step using X-ray CT to obtain data on the CT value of the core body.
The analysis may be performed using a commercially available X-ray CT apparatus.
Examples of data related to the CT value of the core body include a distribution image of the CT value of the core body taken by an X-ray CT apparatus, a CT value histogram showing the relationship between the CT value obtained from the image and the frequency, and the above image. Alternatively, a specific value obtained from the CT value histogram, a numerical value of the standard deviation of the CT value obtained from the image, and the like can be mentioned.
コア体のＣＴ値の分布画像は、コア体のＣＴ値（単位：ＨＵ）の分布を、白黒の濃淡のみで表した画像（光度以外の情報が含まれない画像：グレースケール）である。該画像において、ＣＴ値が大きい部分ほど、白く表示され、ＣＴ値が小さい部分ほど、黒く表示される。
Ｘ線ＣＴ装置によって撮影された画像の一部の領域を選択し、該領域をＣＴ値の分布画像としてもよい。該領域は、通常、Ｘ線ＣＴ装置によって撮影された画像の端部、辺縁部を除いた中心部分が選択される。また、該領域は線、平面、空間のいずれからなる領域であってもよい。
また、ＣＴ値の分布画像（Ｘ線ＣＴ装置によって撮影された画像、または該画像から選択された一部の領域）に対して、改良地盤の品質をより正確に評価する観点から、各種の画像処理を行ってもよい。各種画像処理としては、二値化処理、Ｗａｔｅｒｓｈｅｄ法、濃度変換等が挙げられる。上記二値化処理において、基準となる閾値を定める方法としては、単純閾値、Ｐ−タイル法、モード法、判別分析法（大津の二値化法）等が挙げられる。
さらに、分布画像は２Ｄ画像であっても、３Ｄ画像であってもよい。
ＣＴ値は、Ｖｏｘｅｌ（画素）毎に得られるものである。Ｖｏｘｅｌの一辺の大きさは、φ５〜６ｃｍのコア体を対象とし、一般的な解像度で撮影された場合、通常、１〜５０μｍである。
The distribution image of the CT value of the core body is an image showing the distribution of the CT value (unit: HU) of the core body only in black and white shades (image that does not include information other than luminosity: grayscale). In the image, a portion having a large CT value is displayed in white, and a portion having a small CT value is displayed in black.
A part of the image taken by the X-ray CT apparatus may be selected and the area may be used as a distribution image of CT values. As the region, a central portion excluding the edge portion and the peripheral portion of the image captured by the X-ray CT apparatus is usually selected. Further, the region may be a region consisting of a line, a plane, or a space.
In addition, various images are used from the viewpoint of more accurately evaluating the quality of the improved ground with respect to the distribution image of the CT value (the image taken by the X-ray CT device or a part of the area selected from the image). Processing may be performed. Examples of various image processings include binarization processing, Watershed method, density conversion, and the like. Examples of the method for determining the reference threshold value in the above binarization process include a simple threshold value, a P-tile method, a mode method, a discriminant analysis method (Otsu's binarization method), and the like.
Further, the distribution image may be a 2D image or a 3D image.
The CT value is obtained for each Voxel (pixel). The size of one side of Voxel is usually 1 to 50 μm when a core body having a diameter of 5 to 6 cm is taken and photographed at a general resolution.
また、コア体のＣＴ値の分布画像から得られる特定の値の例としては、上記分布画像に表示されているＣＴ値の平均値や、上記分析画像において最も大きな領域（面積）を占めるＣＴ値等が挙げられる。
コア体のＣＴ値の分布画像から得られる、ＣＴ値と頻度の関係を示したＣＴ値ヒストグラムから得られる特定の値の例としては、ＣＴ値ヒストグラムの、特定のＣＴ値の数値範囲内（通常、頻度のピークを有する範囲内）の頻度の最大値、該範囲内におけるピークの面積、該範囲内のピークのブロード（ＣＴ値の幅）、該範囲内のピークの凸性の度合いを数値に変換したもの等が挙げられる。
Further, as an example of a specific value obtained from the distribution image of the CT value of the core body, the average value of the CT values displayed in the distribution image and the CT value occupying the largest area (area) in the analysis image. And so on.
An example of a specific value obtained from a CT value histogram showing the relationship between the CT value and the frequency obtained from the distribution image of the CT value of the core body is within the numerical range of the specific CT value of the CT value histogram (usually). , The maximum value of the frequency (within the range having the frequency peak), the area of the peak in the range, the broadness of the peak in the range (the width of the CT value), and the degree of convexity of the peak in the range are numerical values. Examples include converted ones.
［評価工程］
本工程は、第一の分析工程で得られたＣＴ値に関するデータを用いて、改良地盤の品質を評価する工程である。
評価に用いられるＣＴ値に関するデータは、上述した１種であってもよく、２種以上であってもよい。
ＣＴ値に関するデータを用いて、改良地盤の品質を評価する方法の例としては、コア体のＣＴ値の分布画像から目視によって評価する方法、上記分布画像または上記分布画像から得られるＣＴ値と頻度の関係を示したＣＴ値ヒストグラムから特定の値を得た後、該値に基づいて評価する方法、予測式作成工程（後述）において得られた予測式を用いて評価する方法、分布画像を畳み込みニューラルネットワーク等を用いた画像解析によって評価する方法等が挙げられる。
[Evaluation process]
This step is a step of evaluating the quality of the improved ground using the data related to the CT value obtained in the first analysis step.
The data regarding the CT value used for the evaluation may be one type or two or more types described above.
Examples of the method of evaluating the quality of the improved ground using the data related to the CT value include a method of visually evaluating the distribution image of the CT value of the core body, the above distribution image or the CT value and frequency obtained from the above distribution image. After obtaining a specific value from the CT value histogram showing the relationship between, the method of evaluating based on the value, the method of evaluating using the prediction formula obtained in the prediction formula creation step (described later), and the convolution of the distribution image. Examples thereof include a method of evaluation by image analysis using a neural network or the like.
以下、分布画像から目視によって改良地盤の品質を評価する方法について、具体的に説明する。
評価する改良地盤の品質の例としては、地盤改良材の添加量、地盤改良材と地盤の混合の程度、地盤改良材の添加時の形態、締固めの打継ぎの有無等が挙げられる。
例えば、ＣＴ値の分布画像において、白い（ＣＴ値が大きい）部分ほど、密度が大きく、黒い（ＣＴ値が小さい）部分ほど、密度が小さいことを意味している。すなわち、画像が全体的に白いほど、地盤改良材の添加量が大きく、全体的に黒いほど、地盤改良材の添加量が小さいと評価することができる。
また、分布画像において、色むらがない（ＣＴ値のばらつきが少ない）ほど、地盤改良材と地盤の混合が十分に行われ、地盤改良材が均一に分散していると評価することができ、色むらが大きい（ＣＴ値のばらつきが大きい）ほど、地盤改良材と地盤の混合が不十分であり、地盤改良材の分散が不均一であると評価することができる。また、地盤改良材と地盤の混合が不十分であるため、地盤改良材がコア体の一部分にダマとして偏在している（塊状となって存在している）場合には、地盤改良材のダマは、ＣＴ値の分布画像において、略円形状の白い塊として表示され、該ダマの有無によって、地盤改良材と地盤の混合の程度を評価することができる。
Hereinafter, a method for visually evaluating the quality of the improved ground from the distribution image will be specifically described.
Examples of the quality of the improved ground to be evaluated include the amount of the ground improvement material added, the degree of mixing of the ground improvement material and the ground, the form when the ground improvement material is added, the presence or absence of compaction jointing, and the like.
For example, in a CT value distribution image, a white portion (larger CT value) means a higher density, and a black portion (smaller CT value) means a lower density. That is, it can be evaluated that the whiter the image is, the larger the amount of the ground improvement material is added, and the blacker the image is, the smaller the amount of the ground improvement material is added.
Further, in the distribution image, the more there is no color unevenness (less variation in CT value), the more the ground improvement material and the ground are mixed sufficiently, and it can be evaluated that the ground improvement material is uniformly dispersed. It can be evaluated that the larger the color unevenness (larger variation in CT value), the more insufficient the mixture of the ground improvement material and the ground, and the more uneven the dispersion of the ground improvement material. In addition, because the mixture of the ground improvement material and the ground is insufficient, if the ground improvement material is unevenly distributed as lumps (exists in a lump) on a part of the core body, the lumps of the ground improvement material Is displayed as a substantially circular white mass in the distribution image of the CT value, and the degree of mixing of the ground improvement material and the ground can be evaluated by the presence or absence of the lump.
また、地盤改良材と改良の対象となる地盤を混合する際の、地盤改良材の形態によっても、ＣＴ値は異なってくる。具体的には、地盤改良材が粉体の状態で混合された場合、地盤改良材がスラリーの形態で混合された場合と比較して、画像がより白く表示される（ＣＴ値が大きくなる）。
さらに、分布画像において、白黒の濃淡が、明確な境目として表れた場合には、地盤改良材と地盤を混合する際に、該境目において締固めの打継ぎが行われたと評価することができる。
In addition, the CT value also differs depending on the form of the ground improvement material when the ground improvement material and the ground to be improved are mixed. Specifically, when the ground improvement material is mixed in the powder state, the image is displayed whiter (the CT value becomes larger) than when the ground improvement material is mixed in the form of a slurry. ..
Further, when the black and white shade appears as a clear boundary in the distribution image, it can be evaluated that the compaction joint was performed at the boundary when the ground improvement material and the ground were mixed.
また、上記分布画像または上記分布画像から得られるＣＴ値と頻度の関係を示したＣＴ値ヒストグラムから、特定の値を得た後、該値の大きさに基づいて評価する方法の例としては、例えば、上記分布画像に表示されているＣＴ値の平均値や、上記分析画像において最も大きな領域（面積）を占めるＣＴ値や、上記ＣＴ値ヒストグラムの、特定のＣＴ値の数値範囲内（通常、頻度のピークを有する範囲内）の頻度の最大値、該範囲内におけるピークの面積、該範囲内のピークのブロード（ＣＴ値の幅）、該範囲内のピークの凸性の度合いを数値に変換したもの等の値が、事前に定めた基準となる数値を満たすかどうかによって改良地盤の品質を評価する方法等が挙げられる。
なお、特定のＣＴ値の数値範囲内（通常、頻度のピークを有する範囲内）の頻度の最大値が大きい場合、地盤改良材の添加量が大きく、上記最大値が小さい場合には固化材の添加量が小さい傾向がみられる。
また、特定のＣＴ値の数値範囲内（通常、頻度のピークを有する範囲内）の頻度の最大値が小さく、かつ、上記範囲内のピークのブロード（ＣＴ値の幅）が大きい場合、地盤改良材と地盤の混合が不十分でありムラが存在しており、上記最大値が大きく、かつ、上記ブロードが小さい場合、地盤改良材と地盤の混合が十分であり、地盤改良材が均一に分散している傾向がみられる。
事前に定めた基準となる数値は、これらの傾向を考慮して、適宜定めればよい。
また、ＣＴ値は、対象となる地盤の土質（例えば、土の粒度や含水量の大きさ）や、地盤改良材の使用時の形態（例えば、粉体形状、スラリー形状）、地盤改良材の添加量等によって変わるため、同じＣＴ値であっても、改良地盤の品質が異なる場合がある。このため、事前に室内配合試験を行い、上記基準となる数値を定めてもよい。
Further, as an example of a method of obtaining a specific value from the distribution image or the CT value histogram showing the relationship between the CT value obtained from the distribution image and the frequency, and then evaluating based on the magnitude of the value. For example, the average value of the CT values displayed in the distribution image, the CT value occupying the largest area (area) in the analysis image, and the numerical range of a specific CT value in the CT value histogram (usually). Converts the maximum frequency value (within the range having the frequency peak), the area of the peak within the range, the broadness of the peak within the range (the width of the CT value), and the degree of convexity of the peak within the range into numerical values. There is a method of evaluating the quality of the improved ground based on whether or not the value of the ground is satisfied with a predetermined standard numerical value.
When the maximum value of the frequency within the numerical range of the specific CT value (usually within the range having the peak frequency) is large, the amount of the ground improvement material added is large, and when the maximum value is small, the solidifying material is used. The amount added tends to be small.
Further, when the maximum value of the frequency within the numerical range of a specific CT value (usually within the range having a peak of frequency) is small and the broadness of the peak within the above range is large (the width of the CT value), the ground is improved. When the mixture of the material and the ground is insufficient and unevenness exists, the maximum value is large and the broad is small, the mixture of the ground improvement material and the ground is sufficient, and the ground improvement material is uniformly dispersed. There is a tendency to do.
Numerical values to be used as a predetermined standard may be appropriately set in consideration of these tendencies.
The CT value is the soil quality of the target ground (for example, the particle size and water content of the soil), the form of the ground improvement material when used (for example, powder shape, slurry shape), and the ground improvement material. Since it changes depending on the amount of addition and the like, the quality of the improved ground may differ even if the CT value is the same. Therefore, an indoor compounding test may be conducted in advance to determine a numerical value that serves as the above standard.
また、より正確かつ詳細に改良地盤の品質を評価する観点から、以下の工程を行ってもよい。
［試験体作製工程］
本工程は、第一の地盤改良工程の前に行われる工程であって、改良の対象となる地盤から得られた土を含み、かつ、地盤改良材の添加量が異なる２つ以上の試験体を作製する工程である。
試験体は、上記土と上記地盤改良材を混合してなるものである。
地盤改良材の添加量は特に限定されるものではないが、少なくとも１つの試験体における地盤改良材の添加量は、第一の地盤改良工程において、地盤改良材と改良の対象となる地盤を混合する際に添加する予定の量であることが好ましい。また、上記試験体の１つとして、地盤改良材の添加量が０ｋｇ／ｍ３であるものを用いてもよい。
試験体としては、地盤改良を行う前に、改良の対象となる地盤に対する地盤改良材の添加量を定める目的で一般的に行われている、室内配合試験で作製される試験体を利用することができる。
Further, from the viewpoint of evaluating the quality of the improved ground more accurately and in detail, the following steps may be performed.
[Test specimen preparation process]
This step is a step performed before the first ground improvement step, and includes two or more test specimens containing soil obtained from the ground to be improved and having different amounts of ground improvement materials added. Is the process of producing.
The test piece is a mixture of the soil and the ground improvement material.
The amount of the ground improvement material added is not particularly limited, but the amount of the ground improvement material added in at least one test piece is a mixture of the ground improvement material and the ground to be improved in the first ground improvement step. It is preferable that the amount is to be added at the time of preparation. Further, as one of the above-mentioned test specimens, one in which the amount of the ground improving material added is 0 kg / m 3 may be used.
As the test body, use a test body prepared by an indoor compounding test, which is generally performed for the purpose of determining the amount of the ground improvement material added to the ground to be improved before the ground improvement is performed. Can be done.
［第二の分析工程］
本工程は、試験体作製工程で得られた試験体を、Ｘ線ＣＴを用いて分析し、試験体のＣＴ値に関するデータを得る工程である。
本工程は、ボーリング工程で得られたコア体の代わりに、試験体作製工程で得られた試験体を用いる以外は、上述した第一の分析工程と同様の工程である。
試験体のＣＴ値に関するデータの例としては、Ｘ線ＣＴ装置によって撮影された、試験体のＣＴ値の分布画像または該画像から得られるＣＴ値と頻度の関係を示したＣＴ値ヒストグラムから得られる、特定の値等が挙げられる。該特定の値は、上述した、コア体のＣＴ値の分布画像から得られる特定の値、及び、コア体のＣＴ値の分布画像から得られる、ＣＴ値と頻度の関係を示したＣＴ値ヒストグラムから得られる特定の値と同様である。
[Second analysis process]
This step is a step of analyzing the test piece obtained in the test piece preparation step using X-ray CT to obtain data on the CT value of the test piece.
This step is the same as the first analysis step described above, except that the test piece obtained in the test piece preparation step is used instead of the core body obtained in the boring step.
As an example of data regarding the CT value of the test piece, it is obtained from a distribution image of the CT value of the test piece taken by an X-ray CT apparatus or a CT value histogram showing the relationship between the CT value obtained from the image and the frequency. , Specific values and the like. The specific value is a CT value histogram showing the relationship between the CT value and the frequency obtained from the above-mentioned specific value obtained from the distribution image of the CT value of the core body and the distribution image of the CT value of the core body. Similar to the specific value obtained from.
［予測式作成工程］
本工程は、試験体作製工程で得られた試験体の品質に関するデータを従属変数とし、第二の分析工程で得られた試験体のＣＴ値に関するデータを独立変数として、回帰分析（重回帰分析を含む）を行って、上記試験体の品質の予測式を作成する工程である。
従属変数である、上記試験体の品質に関するデータの例としては、地盤改良材の添加量、改良地盤（土と地盤改良材を混合してなる試験体）の一軸圧縮強さ、改良地盤の透水係数、ｐＨ、及び改良地盤からの重金属類の溶出量等の実測値が挙げられる。
重金属類とは、カドミウム及びその化合物、六価クロム化合物、シアン、水銀及びその化合物、セレン及びその化合物、鉛及びその化合物、ひ素及びその化合物、フッ素及びその化合物、及び、ホウ素及びその化合物（土壌汚染対策法（平成１５年）において第二種特定有害物質として挙げられているもの）のいずれかである。なお、フッ素及びホウ素は重金属ではないが、フッ素及びその化合物、及び、ホウ素及びその化合物は重金属類に含まれるものとする。
中でも、より正確に評価することができる観点から、六価クロム化合物、水銀及びその化合物、セレン及びその化合物、フッ素及びその化合物、及び、ホウ素及びその化合物が好ましい。
独立変数は、一種であってもよく、２種以上であってもよい。
[Prediction formula creation process]
In this step, regression analysis (multiple regression analysis) uses the data on the quality of the test piece obtained in the test piece preparation step as the dependent variable and the data on the CT value of the test piece obtained in the second analysis step as the independent variable. This is a step of creating a prediction formula for the quality of the test piece by performing (including).
Examples of data on the quality of the above-mentioned test specimens, which are dependent variables, include the amount of ground improvement material added, the uniaxial compressive strength of the improved ground (test specimen made by mixing soil and ground improvement material), and the permeability of the improved ground. Measured values such as coefficient, pH, and amount of heavy metals eluted from the improved ground can be mentioned.
Heavy metals are cadmium and its compounds, hexavalent chromium compounds, cyanide, mercury and its compounds, selenium and its compounds, lead and its compounds, arsenic and its compounds, fluorine and its compounds, and boron and its compounds (soil). It is one of the Class 2 Specified Hazardous Substances listed in the Pollution Control Law (2003). Although fluorine and boron are not heavy metals, fluorine and its compounds, and boron and its compounds are included in heavy metals.
Of these, hexavalent chromium compounds, mercury and its compounds, selenium and its compounds, fluorine and its compounds, and boron and its compounds are preferable from the viewpoint of being able to evaluate more accurately.
The independent variable may be one kind or two or more kinds.
予測式は、従属変数（試験体の品質に関するデータ）１種につき一つ作成される。
予測式は、評価工程において、評価する品質（地盤改良材の添加量、改良地盤の一軸圧縮強さ、改良地盤の透水係数、ｐＨ、及び改良地盤からの重金属類の溶出量等）の種類の数に応じて、複数作成してもよい。
回帰分析に用いられる、従属変数および独立変数からなるデータの組み合わせの個数（試験体の個数）は、２つ以上、予測の精度をより向上する観点から、好ましくは３つ以上、より好ましくは５以上である。
One prediction formula is created for each dependent variable (data on the quality of the test piece).
The prediction formula is a type of quality to be evaluated in the evaluation process (amount of ground improvement material added, uniaxial compressive strength of improved ground, hydraulic conductivity of improved ground, pH, amount of heavy metals eluted from improved ground, etc.). Depending on the number, a plurality may be created.
The number of combinations of data consisting of dependent variables and independent variables (number of test specimens) used in regression analysis is 2 or more, preferably 3 or more, and more preferably 5 from the viewpoint of further improving prediction accuracy. That is all.
予測式作成工程において、予測式を作成した後、上述した評価工程において、第一の分析工程で得られたコア体のＣＴ値に関するデータと、上記予測式を用いて、コア体（ボーリング工程で得られたもの）の品質に関するデータの予測値を得た後、該予測値に基いて、改良地盤の品質を評価することができる。
具体的には、第一の分析工程で得られたコア体のＣＴ値に関するデータ（例えば、上述した、コア体のＣＴ値の分布画像から得られる特定の値や、コア体のＣＴ値の分布画像から得られる、ＣＴ値と頻度の関係を示したＣＴ値ヒストグラム得られる特定の値）を、上記予測式における独立変数として、上記予測式に代入し、得られた予測値（第一の地盤改良工程における地盤改良材の添加量、改良地盤（コア体）の一軸圧縮強さ、改良地盤の透水係数、及び改良地盤からの重金属類の等の予測値）を用いて、改良地盤の品質を評価する。
また、上記予測式を用いた改良地盤の品質の評価と、第一の分析工程で得られたＣＴ値の分布画像を用いた目視による改良地盤の品質の評価を組み合わせて行ってもよい。
In the prediction formula creation step, after the prediction formula is created, in the evaluation step described above, the data on the CT value of the core body obtained in the first analysis step and the above prediction formula are used to perform the core body (in the boring step). After obtaining the predicted value of the data regarding the quality of (obtained), the quality of the improved ground can be evaluated based on the predicted value.
Specifically, the data related to the CT value of the core body obtained in the first analysis step (for example, the specific value obtained from the above-mentioned distribution image of the CT value of the core body or the distribution of the CT value of the core body). The CT value histogram obtained from the image showing the relationship between the CT value and the frequency (a specific value obtained) is substituted into the above prediction formula as an independent variable in the above prediction formula, and the obtained prediction value (first ground) is used. The quality of the improved ground is determined by using the amount of ground improvement material added in the improvement process, the uniaxial compression strength of the improved ground (core body), the water permeability coefficient of the improved ground, and the predicted values of heavy metals from the improved ground). evaluate.
Further, the evaluation of the quality of the improved ground using the above prediction formula and the visual evaluation of the quality of the improved ground using the distribution image of the CT values obtained in the first analysis step may be combined.
上述した改良地盤の品質評価方法によって、第一の地盤改良工程で得られた改良地盤の品質を評価した後、以下の工程を行うことによって、改良地盤の品質を管理することができる。
［調整工程］
本工程は、上記評価工程において、改良地盤の品質を評価した後、該評価の結果に基づいて、地盤の改良条件を調整する工程である。
地盤の改良条件を調整する方法の例としては、地盤改良材の添加量を変更する方法、スラリーの水と地盤改良材の質量比（水／地盤改良材）を変更する方法、地盤改良材の種類を変更する方法、地盤改良材と地盤の混合条件を調整する方法等が挙げられる。
［第二の地盤改良工程］
本工程は、調製工程において調整した地盤の改良条件に基いて、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る工程である。
After evaluating the quality of the improved ground obtained in the first ground improvement step by the above-mentioned quality evaluation method of the improved ground, the quality of the improved ground can be controlled by performing the following steps.
[Adjustment process]
This step is a step of evaluating the quality of the improved ground in the above evaluation step and then adjusting the ground improvement conditions based on the evaluation result.
Examples of methods for adjusting the ground improvement conditions include a method of changing the amount of the ground improvement material added, a method of changing the mass ratio of the slurry water to the ground improvement material (water / ground improvement material), and a method of the ground improvement material. Examples include a method of changing the type and a method of adjusting the mixing conditions of the ground improvement material and the ground.
[Second ground improvement process]
This step is a step of obtaining the improved ground by mixing the ground improving material and the ground to be improved based on the ground improvement conditions adjusted in the preparation step.
以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
［実施例１］
粘性土（含水比６８．５％）に、混合後の土壌の含水比が７１．５％となる量の水を添加してホバート社製の竪型ミキサで１分間混合して得られた土壌に、粉体状の地盤改良材（高有機質土用固化材）を、１００ｋｇ／ｍ３となる量で添加し、「ＪＧＳ ０８２１−２００９（安定処理土の締固めをしない供試体作製方法）」に準拠して、試験体を作製した。試験体の作製において、ホバート社製の竪型ミキサに各材料を同時に投入し、地盤改良材が均一に分散するように、３分間混合した後、７日間密封養生した。
養生後の試験体について、Ｘ線ＣＴ装置（島津製作所社製、商品名「ｉｎｓｐｅＸｉｏ ＳＭＸ−２２５ＣＴ」）を用いて分析を行い、ＣＴ値の分布画像を得た。結果を図１に示す。
Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.
[Example 1]
Soil obtained by adding water to cohesive soil (water content ratio 68.5%) so that the water content ratio of the mixed soil is 71.5% and mixing with a vertical mixer manufactured by Hobart for 1 minute. to, powdered ground improvement material (high organic dog days solidifying material) was added in an amount of 100 kg / m 3, "JGS 0821-2009 (no compaction of treated soil specimen manufacturing method)" A test piece was prepared according to the above. In the preparation of the test piece, each material was put into a vertical mixer manufactured by Hobert Co., Ltd. at the same time, mixed for 3 minutes so that the ground improvement material was uniformly dispersed, and then sealed and cured for 7 days.
The specimen after curing was analyzed using an X-ray CT apparatus (manufactured by Shimadzu Corporation, trade name "inspeXio SMX-225CT"), and a distribution image of CT values was obtained. The results are shown in FIG.
［実施例２］
試験体の作製において、地盤改良材が均一に分散せずに、混合むらが生じるようにする目的で、含水比３％相当の水を固化材と同時に添加して混合時間を１分間にする以外は、実施例１と同様にして試験体を作製した後、該試験体のＣＴ値の分布画像を得た。結果を図２−１に示す。
また、ＣＴ値の分布画像を得る際に、分布画像の低ＣＴ値の領域を非表示に変更することで得られたＣＴ値の分布画像を図２−２に示す。
［実施例３］
粉体状の地盤改良材の代わりに、該地盤改良材と水を、水地盤改良材比（水／地盤改良材の質量比）が１となるように混合してなるスラリーを用いる以外は、実施例１と同様にして試験体を作製した後、該試験体のＣＴ値の分布画像を得た。結果を図３に示す。
［実施例４］
粘性土（含水比６８．５％）に、混合後の土壌の含水比が７１．５％となる量の水を添加してホバート社製の竪型ミキサで１分間混合して得られた土壌にと粉体状の地盤改良材（高有機質土用固化材）を、該固化剤の添加量が１００ｋｇ／ｍ３となるように、ホバート社製の竪型ミキサに同時に投入し、地盤改良材が均一に分散するように、３分間混合した後、締固めを行った。次いで、締固めた土壌の上面に、土壌に、粉体状の地盤改良材を、２００ｋｇ／ｍ３となる量で使用し、同様に混合した混合物を投入し、締固めを行った。さらに、締固めた土壌の上面に、土壌に、粉体状の地盤改良材を、３００ｋｇ／ｍ３となる量で使用し、同様に混合した混合物を投入した後、締固めを行い、試験体を得た。該試験体について、Ｘ線ＣＴ装置を用いて分析を行い、ＣＴ値の分布画像を得た。結果を図４に示す。
[Example 2]
In the preparation of the test piece, for the purpose of preventing the ground improvement material from being uniformly dispersed and causing uneven mixing, water having a water content of 3% is added at the same time as the solidifying material to set the mixing time to 1 minute. After preparing a test body in the same manner as in Example 1, a distribution image of CT values of the test body was obtained. The results are shown in FIG. 2-1.
Further, when the distribution image of the CT value is obtained, the distribution image of the CT value obtained by changing the region of the low CT value of the distribution image to non-display is shown in FIG. 2-2.
[Example 3]
Instead of using a powdery ground improvement material, a slurry obtained by mixing the ground improvement material and water so that the water ground improvement material ratio (mass ratio of water / ground improvement material) is 1 is used. After preparing a test body in the same manner as in Example 1, a distribution image of CT values of the test body was obtained. The results are shown in FIG.
[Example 4]
Soil obtained by adding water to cohesive soil (water content ratio 68.5%) so that the water content ratio of the mixed soil is 71.5% and mixing with a vertical mixer manufactured by Hobart for 1 minute. to a powder-like soil improvement material (high organic dog days solidifying material), as the addition amount of the solid agent is 100 kg / m 3, and at the same time put in Hobart Corp. vertical mixer, soil improvement material After mixing for 3 minutes so that the mixture was uniformly dispersed, compaction was performed. Next, on the upper surface of the compacted soil, a powdery ground conditioner was used in an amount of 200 kg / m 3 in the soil, and a similarly mixed mixture was added to compact the soil. Further, on the upper surface of the compacted soil, a powdery ground improving material was used in the soil in an amount of 300 kg / m 3, and a mixture mixed in the same manner was added, and then compaction was performed to test the test piece. Got The test piece was analyzed using an X-ray CT apparatus to obtain a distribution image of CT values. The results are shown in FIG.
図１と図２−１の比較から、地盤改良材の混合が不十分である場合（図２−１：実施例２）、地盤改良材の混合が十分である場合（図１：実施例１）と比較して、ＣＴ値の分析画像において、色むらが生じていることがわかる。また、図２−２から、地盤改良材のダマが生じていることがわかる。
また、図１と図３の比較から、粉体状の地盤改良材を用いた場合（図１：実施例１）、スラリー状の地盤改良材を用いた場合（図３：実施例３）と比較して、分布画像が全体的に白い（ＣＴ値が大きい）ことがわかる。
さらに、図４から、地盤改良材の添加量が大きくなると、ＣＴ値の分析画像において、色がより白くなる（ＣＴ値が大きくなる）ことがわかる。
From the comparison between FIGS. 1 and 2-1, when the mixing of the ground improving material is insufficient (Fig. 2-1: Example 2) and when the mixing of the ground improving material is sufficient (Fig. 1: Example 1). ), It can be seen that color unevenness occurs in the analysis image of the CT value. Further, from FIG. 2-2, it can be seen that the ground improvement material is lumped.
Further, from the comparison between FIGS. 1 and 3, when the powdery ground improving material was used (Fig. 1: Example 1) and when the slurry-like ground improving material was used (Fig. 3: Example 3). By comparison, it can be seen that the distribution image is generally white (the CT value is large).
Further, from FIG. 4, it can be seen that as the amount of the ground improving material added increases, the color becomes whiter (the CT value increases) in the analysis image of the CT value.
Claims (5)
上記改良地盤をボーリングして、コア体を得るボーリング工程と、
上記コア体を、Ｘ線ＣＴを用いて分析し、上記コア体のＣＴ値に関するデータを得る第一の分析工程と、
上記ＣＴ値に関するデータを用いて、上記改良地盤の品質を評価する評価工程を含むことを特徴とする改良地盤の品質評価方法。 The first ground improvement process to obtain improved ground by mixing the ground improvement material and the ground to be improved,
The boring process to obtain the core body by boring the above improved ground,
The first analysis step of analyzing the core body using X-ray CT and obtaining data on the CT value of the core body, and
A quality evaluation method for improved ground, which comprises an evaluation step for evaluating the quality of the improved ground using data related to the CT value.
改良の対象となる地盤から得られた土を含み、かつ、地盤改良材の添加量が異なる２つ以上の試験体を作製する試験体作製工程と、
上記試験体を、Ｘ線ＣＴを用いて分析し、上記試験体のＣＴ値に関するデータを得る第二の分析工程と、
上記試験体の品質に関するデータを従属変数とし、上記試験体のＣＴ値に関するデータを独立変数として、回帰分析を行って、上記試験体の品質の予測式を作成する予測式作成工程を行い、
上記評価工程において、上記コア体のＣＴ値に関するデータと、上記予測式を用いて、上記コア体の品質に関するデータの予測値を得た後、該予測値に基いて、上記改良地盤の品質を評価する請求項１または２に記載の改良地盤の品質評価方法。 Before the first ground improvement process above,
A test specimen preparation process for preparing two or more test specimens containing soil obtained from the ground to be improved and having different amounts of ground improvement materials added.
A second analysis step of analyzing the test piece using X-ray CT to obtain data on the CT value of the test piece, and
Regression analysis is performed with the data related to the quality of the test piece as the dependent variable and the data related to the CT value of the test piece as the independent variable, and a prediction formula creation step for creating a prediction formula for the quality of the test piece is performed.
In the evaluation step, after obtaining the predicted value of the data related to the quality of the core body by using the data related to the CT value of the core body and the prediction formula, the quality of the improved ground is determined based on the predicted value. The quality evaluation method for improved ground according to claim 1 or 2 to be evaluated.
調整した地盤の改良条件に基いて、地盤改良材と改良の対象となる地盤を混合して、改良地盤を得る第二の地盤改良工程を含む改良地盤の品質管理方法。 After evaluating the quality of the improved ground by the quality evaluation method of the improved ground according to any one of claims 1 to 4, the adjustment step of adjusting the improvement conditions of the ground based on the evaluation result, and the adjustment step.
A quality control method for improved ground including a second ground improvement step of mixing the ground improvement material and the ground to be improved based on the adjusted ground improvement conditions to obtain the improved ground.
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