JP6621137B2 - Method for evaluating the soundness of buried objects - Google Patents
Method for evaluating the soundness of buried objects Download PDFInfo
- Publication number
- JP6621137B2 JP6621137B2 JP2016008423A JP2016008423A JP6621137B2 JP 6621137 B2 JP6621137 B2 JP 6621137B2 JP 2016008423 A JP2016008423 A JP 2016008423A JP 2016008423 A JP2016008423 A JP 2016008423A JP 6621137 B2 JP6621137 B2 JP 6621137B2
- Authority
- JP
- Japan
- Prior art keywords
- evaluation
- soil
- soundness
- natural potential
- steel material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims description 26
- 229910000831 Steel Inorganic materials 0.000 claims description 135
- 239000010959 steel Substances 0.000 claims description 135
- 238000011156 evaluation Methods 0.000 claims description 118
- 239000002689 soil Substances 0.000 claims description 106
- 239000000463 material Substances 0.000 claims description 90
- 230000035699 permeability Effects 0.000 claims description 31
- 238000005259 measurement Methods 0.000 claims description 8
- 238000005260 corrosion Methods 0.000 description 61
- 230000007797 corrosion Effects 0.000 description 60
- 229910001335 Galvanized steel Inorganic materials 0.000 description 14
- 239000008397 galvanized steel Substances 0.000 description 14
- 229910001018 Cast iron Inorganic materials 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000011701 zinc Substances 0.000 description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 230000001066 destructive effect Effects 0.000 description 4
- 229910052725 zinc Inorganic materials 0.000 description 4
- 238000005273 aeration Methods 0.000 description 3
- 238000009933 burial Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000011835 investigation Methods 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 238000009412 basement excavation Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 230000036962 time dependent Effects 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 241000243714 Lutosa Species 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- VEMHQNXVHVAHDN-UHFFFAOYSA-J [Cu+2].[Cu+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O Chemical compound [Cu+2].[Cu+2].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O VEMHQNXVHVAHDN-UHFFFAOYSA-J 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000001364 causal effect Effects 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical class [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 238000013480 data collection Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- -1 for example Substances 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Landscapes
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Description
本発明は、土壌中に縦埋設された鋼材の健全度を非破壊に評価する方法であり、地際から土中部までの表面状態を非破壊に調べることができる埋設物健全度評価方法に関する。 The present invention relates to a method for nondestructively evaluating the soundness of a steel material vertically embedded in soil, and relates to a method for evaluating the soundness of a buried object capable of nondestructively examining the surface state from the ground to the middle of the soil.
従来から、土壌中に埋設された鋼材の腐食に関する評価技術としては、幾つかの提案がなされている。
例えば、特許文献１では、対地電位測定器のターミナルを土壌中に埋設された鋳鉄管に接触させ、銅硫酸銅電極を管路に沿って移動させて地上から鋳鉄管の対地電位Ｐ／Ｓを測定すると共に自然電位測定器により地上から鋳鉄の自然電位Ｅｃｏｒを測定し、鋳鉄管の管対地電位Ｐ／Ｓの値と管対地電位と鋳鉄の自然電位Ｅｃｏｒの差の値の両者から腐食を判定し、これらの値の大きさから腐食度と将来の腐食進行度を予測する技術が提案され、これによって、地上から簡単に埋設鋳鉄管の腐食を検知し、かつ将来の腐食の進行度を予測できるとされている。
Conventionally, several proposals have been made as an evaluation technique related to corrosion of steel materials embedded in soil.
For example, in Patent Document 1, a terminal of a ground potential measuring device is brought into contact with a cast iron pipe embedded in soil, and a copper sulfate copper electrode is moved along the pipe line to obtain a ground potential P / S of the cast iron pipe from the ground. The natural potential E cor of the cast iron is measured from the ground with a natural potential measuring device, and corrosion is determined from both the value of the pipe-to-ground potential P / S of the cast iron pipe and the difference between the pipe-to-ground potential and the natural potential E cor of the cast iron. A technology has been proposed that predicts the degree of corrosion and the degree of future corrosion from the magnitude of these values, which makes it easy to detect the corrosion of buried cast iron pipes from the ground and the degree of future corrosion. Can be predicted.
また、特許文献２には、土中に埋設された鋳鉄管の腐食深さを、
η＝ｋｔα ［η：腐食深さ、ｔ：埋設期間、ｋ，α：定数］で表し、定数ｋを、
ｋ＝ｅｘｐ（β０＋Ｃ１＋Ｃ２＋Ｃ３＋Ｃ４＋Ｃ５＋Ｃ６） ［β０： 定数、Ｃ１〜Ｃ６：土質、地盤の種類、土壌の比抵抗、土壌のｐＨ、土壌の酸化還元電位、土壌における硫化物の検出の有無にもとづく係数］で表し、多数の地域において埋設されているそれぞれの鋳鉄管の腐食深さの測定値と、その管の周囲の土壌の分析結果とから、多数の調査サンプルを作成して、定数β０と係数Ｃ１〜Ｃ６とをあらかじめ決定しておいて、特定の地域に埋設されている管の腐食深さを、その管が埋設されている土壌についての情報と、その管の埋設期間にもとづいて予測することが提案され、これによって、地中に埋設された管体の腐食量を予測するに際し、その予測を行うごとに管体の腐食深さについての情報を得る必要はなくなるとされている。
In Patent Document 2, the corrosion depth of the cast iron pipe embedded in the soil is
η = kt α [η: corrosion depth, t: burial period, k, α: constant]
k = exp (β 0 + C1 + C2 + C3 + C4 + C5 + C6) [β 0 : constant, C1 to C6: soil quality, soil type, soil resistivity, soil pH, soil redox potential, coefficient based on the presence or absence of detection of sulfide in soil A large number of survey samples are created from the measured corrosion depth of each cast iron pipe buried in a large number of areas and the analysis result of the soil surrounding the pipe, and the constant β 0 Coefficients C1 to C6 are determined in advance, and the corrosion depth of a pipe buried in a specific area is predicted based on information about the soil in which the pipe is buried and the period of time the pipe is buried. Therefore, when predicting the amount of corrosion of pipes buried in the ground, it is no longer necessary to obtain information about the corrosion depth of pipes every time the prediction is made. The
また、特許文献３には、土壌等の媒質中に配設され、腐食検討対象物である埋設管のアノード部とコンクリート建物内の鉄筋であるカソード部との間に形成されるマクロセルにより発生する腐食を推定するに際し、腐食を腐食検討対象物の深さ方向断面で半回転楕円状に減肉が進む楕円状腐食と見なし、現在の減肉深さｒと媒質の比抵抗ρとを求め、求められた現在の減肉深さｒと前記媒質の比抵抗ρとに基づいて、腐食検討対象物の余寿命Ｔ−ｔを求めることによって、現在の減肉深さ、腐食検討対象物周りに存する媒質の比抵抗から、余寿命を推定することが提案されている。 Further, in Patent Document 3, it is generated in a macro cell that is disposed in a medium such as soil and formed between an anode portion of a buried pipe that is a subject of corrosion examination and a cathode portion that is a reinforcing bar in a concrete building. When estimating the corrosion, the corrosion is regarded as an elliptical corrosion in which the thinning proceeds to a half-rotation elliptical shape in the depth direction cross section of the corrosion examination object, and the current thinning depth r and the specific resistance ρ of the medium are obtained, Based on the obtained current thinning depth r and the specific resistance ρ of the medium, the remaining life T-t of the corrosion examination object is obtained, so that the current thinning depth and the corrosion examination object are surrounded. It has been proposed to estimate the remaining lifetime from the specific resistance of the existing medium.
さらに、特許文献４には、一部がコンクリートで覆われ且つ他部が土壌に接触する状態で土壌中に埋設される鋼材の診断方法として、少なくとも前記鋼材の対地電位と土壌の比抵抗とを測定し、前記鋼材の対地電位及び前記土壌の比抵抗に基づいて鋼材の全面腐食に関する評価を行い、前記一部及び他部における前記鋼材の対地電位の電位差に基づいて、鋼材に発生し得るＣ／Ｓマクロセル腐食に関する評価を行い、前記鋼材に発生し得る通気差マクロセル腐食に関する評価を行い、全面腐食に関する評価結果とＣ／Ｓマクロセル腐食に関する評価結果と通気差マクロセル腐食に関する評価結果とを用いて、鋼材の腐食状態を診断することが提案され、これによって、実際に試掘を行うことなく、土壌中に埋設される鋼材の劣化状況を診断し得るとされている。 Furthermore, in Patent Document 4, as a method for diagnosing steel material partly covered with concrete and the other part in contact with the soil, at least the ground potential of the steel material and the specific resistance of the soil are described. Measure and evaluate the overall corrosion of the steel material based on the ground potential of the steel material and the specific resistance of the soil, C that can occur in the steel material based on the potential difference of the ground potential of the steel material in the part and other parts / S macrocell corrosion is evaluated, and aeration difference macrocell corrosion that can occur in the steel material is evaluated, and the evaluation results regarding overall corrosion, the evaluation results regarding C / S macrocell corrosion, and the evaluation results regarding aeration difference macrocell corrosion are used. Therefore, it is proposed to diagnose the corrosion state of steel materials, thereby diagnosing the deterioration status of steel materials embedded in the soil without actually conducting a trial digging. Lutosa has been.
しかし、前記特許文献１〜４で提案された技術には、次に述べるような種々の問題点があった。
まず、前記特許文献１で提案された技術では、配管表面近くの自然電位Ｅｃｏｒを測定するための削孔作業が必要であり、また、普遍的な判定基準を得るためには、膨大なデータ収集ならびに解析が必要になるという問題点があった。
また、前記特許文献２で提案された技術では、特定の地域の測定データが数多く必要とされ、関係式を求めるための作業量や費用が多くなるばかりか、汎用性のある式を求めるために膨大なデータならびに解析が必要であるという欠点があった。
前記特許文献３で提案された技術は、被覆した土壌中配管には適用できるが、被覆のない裸鋼管には適用できず、また、腐食形態が、局部的な場合には適用できるが、腐食部が広い場合には適用できないという問題点があった。
さらに、前記特許文献４で提案された技術では、作業量や費用が多くなるとともに、評価基準の数が多すぎるため、汎用性のある式を求めるために膨大なデータならびに解析が必要であるという欠点があった。
However, the techniques proposed in Patent Documents 1 to 4 have various problems as described below.
First, the technique proposed in Patent Document 1 requires a drilling operation for measuring the natural potential E cor near the pipe surface, and a large amount of data is required to obtain a universal criterion. There was a problem that collection and analysis were necessary.
In addition, the technique proposed in Patent Document 2 requires a large amount of measurement data in a specific area, which not only increases the amount of work and cost for obtaining the relational expression, but also to obtain a versatile expression. There was a drawback that a huge amount of data and analysis were required.
The technique proposed in Patent Document 3 can be applied to coated soil pipes, but cannot be applied to uncoated bare steel pipes, and can be applied when the corrosion form is localized. There is a problem that it cannot be applied when the section is wide.
Furthermore, the technique proposed in Patent Document 4 requires a large amount of data and analysis in order to obtain a versatile expression because the amount of work and cost increase and the number of evaluation criteria is too large. There were drawbacks.
また、前記特許文献１〜４で提案された技術に加え、土壌中に縦埋設された鋼材の健全度を評価するためには、例えば、以下の方法もあったが、非破壊検査ではできないか、評価の精度が悪かった。
深さ方向の自然電位測定：
縦埋設された鋼材の深さ方向の自然電位の値Ｅｃｏｒおよびその分布Ｅｄｉｓによって鋼材の腐食形態をおおよそ評価することができたが、自然電位を測定するための照合電極を鋼材に沿って深さ方向に当てるための縦孔を設ける必要があり、現地では多大な労力を要するという作業上の問題があった。
鋼材の分極抵抗測定：
鋼材の分極抵抗Ｒｐを現地で測定し、下式に示すような換算式によって鋼材の腐食速度を推定する方法があったが、下式の定数ｋが土壌環境や鋼材の表面状態（さびの有無、さびの分布、亜鉛めっき層の有無など）によって変わるために正確な腐食速度を求めることができなかった。
ｉ＝ｋ／Ｒｐ
ここで、ｉは腐食速度ｍＡ／ｍ２、ｋは定数ｍＶおよびＲｐは分極抵抗Ωｍ２である。
In addition to the techniques proposed in Patent Documents 1 to 4, for example, in order to evaluate the soundness of the steel material vertically embedded in the soil, there was the following method. The accuracy of the evaluation was bad.
Self potential measurement in the depth direction:
Although the corrosion form of steel was able to be roughly evaluated by the value E cor and the distribution E dis of the natural potential in the depth direction of the vertically embedded steel, a reference electrode for measuring the natural potential was provided along the steel. It was necessary to provide a vertical hole for application in the depth direction, and there was a work problem that required a great deal of labor locally.
Measurement of polarization resistance of steel:
The polarization resistance R p of the steel was measured in the field, there was a method of estimating the corrosion rate of the thus steel in terms of type, as shown in the following equation, the surface condition (rust constant k of the formula soil environment and steel The exact corrosion rate could not be obtained because it changed depending on the presence or absence of rust, the distribution of rust, the presence or absence of a galvanized layer, etc.
i = k / R p
Here, i is a corrosion rate mA / m 2 , k is a constant mV, and R p is a polarization resistance Ωm 2 .
そこで、本発明者らは、前記従来技術における種々の問題点を解消すべく、土壌中に縦埋設された鋼材の健全度を非破壊に評価する方法について鋭意検討したところ、次のような知見を得たのである。 Therefore, the present inventors have conducted intensive studies on a method for non-destructively evaluating the soundness of a steel material vertically embedded in soil in order to solve various problems in the prior art. I got.
まず、土壌中に縦埋設された対象鋼材から水平方向に任意の間隔で地表面に照合電極を当てて自然電位Ｅｃｏｒ、自然電位分布Ｅｄｉｓおよびその分布の形状Ｅｐａｔを測定し、自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓを、予め実績値に基づいて作成しておいた鋼材の自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓと表面状態Ｐｃｏｒからなる電位分布評価基準にあてはめ、対象鋼材の健全度を評価することによって、土壌中に縦埋設された鋼材の健全度を、少ないデータから汎用性のある評価をし得る評価方法を見出したのである。 First, the natural potential E cor , the natural potential distribution E dis and the shape E pat of the distribution are measured by applying a reference electrode to the ground surface at an arbitrary interval in the horizontal direction from the target steel material vertically embedded in the soil. E cor and natural potential distribution E dis are applied to the potential distribution evaluation standard consisting of the natural potential E cor , natural potential distribution E dis and surface state P cor of the steel material prepared in advance based on the actual values. By evaluating the soundness level, they found an evaluation method that can evaluate the soundness of steel materials vertically embedded in soil from a small amount of data.
また、前記評価方法に加え、測定対象の土壌中に複数の鋼材（例えば、亜鉛めっき鋼、裸鋼、ステンレス鋼）を埋設してそれらの自然電位を測定し、この測定値を、予め実績値に基づいて作成しておいた土壌通気性評価基準にあてはめ、土壌通気性の良否を評価し、さらに、この評価を、前記電位分布評価基準に基づく評価と組み合わせることによって、対象鋼材の健全度をより精度よく評価し得る評価方法を見出したのである。 In addition to the evaluation method, a plurality of steel materials (for example, galvanized steel, bare steel, stainless steel) are embedded in the soil to be measured, and their natural potentials are measured. Is applied to the soil permeability evaluation criteria prepared based on the above, and the quality of soil permeability is evaluated, and further, this evaluation is combined with the evaluation based on the potential distribution evaluation criteria, thereby reducing the soundness of the target steel material. We have found an evaluation method that can be evaluated more accurately.
さらに、埋設土壌の比抵抗分布ρｄｉｓを測定し、ρｄｉｓの値と前記自然電位分布Ｅｄｉｓの値を、予め実績値に基づいて作成しておいた腐食性評価基準にあてはめ、土壌中に流れる腐食電流を算出し、埋設鋼材の腐食されやすさ（腐食速度）を推定し、これを前記二つの評価と組み合わせることにより、対象鋼材の腐食性を推定するとともに、その健全度をより精度よくかつ総合的に評価し得る評価方法を見出したのである。 Further, the specific resistance distribution ρ dis of the buried soil is measured, and the value of ρ dis and the value of the natural potential distribution E dis are applied to the corrosivity evaluation standard prepared based on the actual value in advance. By calculating the flowing corrosion current, estimating the susceptibility (corrosion rate) of the buried steel material, and combining this with the above two evaluations, the corrosivity of the target steel material is estimated, and its soundness level is more accurate. In addition, they have found an evaluation method that can be comprehensively evaluated.
本発明は、上記知見に基づいてなされたものであって、
（１）土壌中に縦埋設された対象鋼材について、該対象鋼材の埋設地点から水平方向に任意の間隔で地表面に照合電極を当てることにより、該対象鋼材の自然電位Ｅｃｏｒを測定し、測定した自然電位Ｅｃｏｒ と対象鋼材からの距離との関係から自然電位分布Ｅｄｉｓを求め、自然電位Ｅｃｏｒおよび自然電位分布Ｅｄｉｓを、予め実績値に基づいて作成しておいた鋼材の自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓと表面状態Ｐｃｏｒからなる電位分布評価基準にあてはめ、対象鋼材の健全度を精度よく評価する埋設物健全度評価方法（以下、「本発明１」ともいう）、
を特徴とするものである。
The present invention has been made based on the above findings,
(1) For the target steel material vertically embedded in the soil, the natural potential E cor of the target steel material is measured by applying a reference electrode to the ground surface at an arbitrary interval in the horizontal direction from the target steel material burying point, The natural potential distribution E dis is obtained from the relationship between the measured natural potential E cor and the distance from the target steel material , and the natural potential E cor and the natural potential distribution E dis are generated based on the actual values in advance. The embedded object soundness evaluation method (hereinafter also referred to as “present invention 1”) is applied to the potential distribution evaluation standard composed of the potential E cor , the natural potential distribution E dis, and the surface state P cor and accurately evaluates the soundness of the target steel material. ,
It is characterized by.
また、本発明は、
（２）前記（１）に記載の埋設物健全度評価方法において、測定対象の土壌中に複数の異種鋼材を埋設して該異種鋼材の自然電位を測定し、この測定値を、予め実績値に基づいて作成しておいた土壌通気性評価基準にあてはめて土壌通気性の評価を行い、さらに、前記電位分布評価基準による評価と土壌通気性評価基準による評価との組み合わせによって、対象鋼材の健全度をより精度よく評価する前記（１）に記載の埋設物健全度評価方法（以下、「本発明２」ともいう）、
を特徴とするものである。
The present invention also provides:
(2) In the buried object soundness evaluation method according to (1), a plurality of dissimilar steel materials are embedded in the soil to be measured, and the natural potential of the dissimilar steel materials is measured. The soil permeability is evaluated based on the soil permeability evaluation criteria prepared based on the above, and the soundness of the target steel material is further improved by combining the evaluation based on the potential distribution evaluation criteria and the evaluation based on the soil permeability evaluation criteria. The embedded object soundness evaluation method according to (1) for evaluating the degree of accuracy more accurately (hereinafter, also referred to as “present invention 2”),
It is characterized by.
さらに、本発明は、前記（２）に記載の埋設物健全度評価方法において、鋼材が縦埋設されている土壌の深さ方向の比抵抗分布ρｄｉｓを測定し、この測定値ρｄｉｓと自然電位分布Ｅｄｉｓを、予め実績値に基づいて作成しておいた腐食性評価基準にあてはめて対象鋼材の腐食性の評価を行い、さらに、前記電位分布評価基準による評価と前記土壌通気性評価基準による評価と腐食性評価基準による評価との組み合わせによって、対象鋼材の腐食性を推定するとともに、健全度をより精度よく総合的に評価する前記（２）に記載の埋設物健全度評価方法（以下、「本発明３」ともいう）、
を特徴とするものである。
Further, the present invention provides the embedded object soundness evaluation method according to the above (2) , wherein the resistivity distribution ρ dis in the depth direction of the soil in which the steel material is vertically embedded is measured, and the measured value ρ dis The potential distribution E dis is applied to the corrosivity evaluation criteria prepared in advance based on the actual values, and the corrosivity of the target steel material is evaluated. Further, the evaluation based on the potential distribution evaluation criteria and the soil permeability evaluation criteria The method for evaluating the soundness level of buried objects according to the above (2) , in which the corrosivity of the target steel material is estimated and the soundness level is comprehensively evaluated with a combination of the evaluation based on the evaluation based on the evaluation based on the corrosiveness evaluation standard , Also referred to as “Invention 3”),
It is characterized by.
そして、前記本発明１〜３によれば、腐食電位を測定するための削孔作業が不要となり、また、電位分布、土壌の通気性、比抵抗による判定基準は、ＦＥＭ（有限要素法）のような数値解析が可能であり、普遍性が高いので、膨大なデータ収集や解析が不要となる。
つまり、オームの法則やファラデーの法則など基本的な原理にしたがって解析することができ、また、電気化学的な因子と腐食との因果関係に基づいて埋設物健全度を評価し得る。
さらに、評価基準の数が最大三要素であって、評価が簡単であり、被覆のない裸鋼の腐食判定にも適用でき、腐食形態が広い場合にも適用できることから、前記従来技術の問題点を解消することができるのである。
And according to the said invention 1-3, the drilling operation | work for measuring a corrosion potential becomes unnecessary, and the determination criteria by electric potential distribution, soil air permeability, and specific resistance are FEM (finite element method). Such numerical analysis is possible and the universality is high, so huge data collection and analysis are not required.
In other words, analysis can be performed according to basic principles such as Ohm's law and Faraday's law, and the soundness of buried objects can be evaluated based on the causal relationship between electrochemical factors and corrosion.
Furthermore, since the number of evaluation criteria is a maximum of three elements, the evaluation is simple, it can be applied to the corrosion judgment of uncovered bare steel, and can be applied even when the corrosion form is wide. Can be eliminated.
以下、本発明について、詳細に説明する。 Hereinafter, the present invention will be described in detail.
自然電位分布Ｅｄｉｓから縦埋設した鋼材の健全度を評価する方法（本発明１）：
図１に、本発明１の概略説明図を示す。
図１において、土壌中に対象鋼材が縦埋設され、電圧計（デジタルマルチメータ）のプラス端子が対象鋼材に接続され、マイナス端子は照合電極に接続されている。
縦埋設した対象鋼材から等間隔（例えば０．２ｍの間隔。図１中では、等間隔位置を破線で示す。）に、距離の合計が対象鋼材の埋設深さ程度になるまで、照合電極移動方向（水平方向）に沿って、照合電極を直線上に移動しながら、対象鋼材の自然電位Ｅｃｏｒを測定し、記録することによって、自然電位分布Ｅｄｉｓを得ることができる。
そして、測定値について、例えば、横軸を対象鋼材からの距離、また、縦軸を自然電位Ｅｃｏｒの値として両者の関係をプロットすると、自然電位分布Ｅｄｉｓの形が、分布の形状Ｅｐａｔとしてグラフ化されて描かれる。
図２は、自然電位分布Ｅｄｉｓをグラフ化した分布の形状Ｅｐａｔの一例である。
Method for evaluating the soundness of a steel material vertically embedded from the natural potential distribution E dis (present invention 1):
FIG. 1 shows a schematic explanatory diagram of the first aspect of the present invention.
In FIG. 1, a target steel material is vertically embedded in soil, a plus terminal of a voltmeter (digital multimeter) is connected to the target steel material, and a minus terminal is connected to a reference electrode.
The reference electrode is moved at equal intervals from the vertically embedded target steel material (for example, at an interval of 0.2 m. In FIG. 1, the equally spaced positions are indicated by broken lines) until the total distance is about the embedded depth of the target steel material. The natural potential distribution E dis can be obtained by measuring and recording the natural potential E cor of the target steel material while moving the reference electrode on a straight line along the direction (horizontal direction).
Then, with respect to the measured values, for example, when the horizontal axis is the distance from the target steel material and the vertical axis is the value of the natural potential E cor , the relationship between the two is plotted, and the shape of the natural potential distribution E dis becomes the distribution shape E pat As a graph.
FIG. 2 is an example of a distribution shape E pat in which the natural potential distribution E dis is graphed.
自然電位分布Ｅｄｉｓあるいは分布の形状Ｅｐａｔにおいて、対象鋼材の腐食箇所が地表面に近い場合は鋼材に近い位置の自然電位の差が５ｍＶ以上卑（マイナス方向）な値に、深い個所にある場合は鋼材から遠い位置の自然電位差が５ｍＶ以上卑な値になるので、自然電位分布Ｅｄｉｓあるいは分布の形状Ｅｐａｔから、対象鋼材の腐食の発生を推定できる。
また、自然電位の値Ｅｃｏｒと表面状態Ｐｃｏｒによって、鋼材が腐食しているかまたは防食状態にあるかが判定できるので、上記の自然電位分布Ｅｄｉｓと組み合わせることによって、埋設部の腐食形態が判定できる。また、自然電位分布Ｅｄｉｓの差が５ｍＶ未満であれば均一に腐食しているかまたは腐食していないことが分かる。
なお、自然電位分布Ｅｄｉｓは、対象鋼材から複数の方向に測定することによって、方向によって異なる腐食形態を調べることもできる。
これらの評価基準は、実績値に基づいて予め作成し、対象鋼材に関する測定値を評価基準として一覧化した評価基準表と照合することによって、対象鋼材の健全度評価を容易にかつ非破壊に行うことができる。
なお、本発明１〜３でいう「実績値」とは、実地測定値、表面観察結果、数値解析結果に基づいた過去からの蓄積データをいう。
In the natural potential distribution E dis or the distribution shape E pat , when the corrosion location of the target steel material is close to the ground surface, the difference in natural potential at the position close to the steel material is 5 mV or more in the base (minus direction) value and deep. In this case, since the natural potential difference at a position far from the steel material is a base value of 5 mV or more, the occurrence of corrosion of the target steel material can be estimated from the natural potential distribution Edis or the distribution shape Epat .
Further, since it is possible to determine whether the steel material is corroded or anticorrosive based on the natural potential value E cor and the surface state P cor , the corrosion form of the buried portion can be determined by combining with the natural potential distribution E dis described above. Can be judged. Moreover, if the difference of the natural potential distribution E dis is less than 5 mV, it can be seen that it is uniformly corroded or not corroded.
In addition, the self- potential distribution Edis can also investigate the corrosion form which changes with directions by measuring in several directions from object steel material.
These evaluation criteria are created in advance based on the actual values, and the evaluation of the soundness of the target steel is easily and non-destructive by comparing with the evaluation criteria table listing the measured values related to the target steel as the evaluation criteria. be able to.
The “actual values” in the first to third aspects of the present invention refers to accumulated data from the past based on actual measured values, surface observation results, and numerical analysis results.
土壌通気性評価を組み合わせた、自然電位分布Ｅｄｉｓから縦埋設した鋼材の健全度を評価する方法（本発明２）：
測定対象の土壌中に複数の異種鋼材、例えば、亜鉛めっき鋼、裸鋼、ステンレス鋼、を埋設して、前記異種鋼材のそれぞれの自然電位を測定し、この測定値を、予め実績値に基づいて作成しておいた土壌通気性評価基準にあてはめて土壌通気性の評価を行い、さらに、前記本発明１における上記の電位分布評価基準に基づく評価と組み合わせて評価することにより、自然電位分布Ｅｄｉｓによる評価をより精度よく行うことができる。
一般に、通気性の良い土壌中では、埋設されてから１時間以内では、貴（プラス方向）の自然電位を示し、通気性の悪い土壌中では、卑な自然電位を示す。土壌の通気性とこれらの自然電位との関係をまとめた評価基準を上記の自然電位分布Ｅｄｉｓと組み合わせることによって、測定対象の自然電位が通気性によるものなのか、鋼材表面性状（鋼材の腐食生成物による自然電位の貴化、亜鉛めっきの腐食生成物による自然電位の貴化、乾燥による自然電位の貴化など）によるものなのかを判別できるので、上記の自然電位分布Ｅｄｉｓによる評価をより正確に行うことができる。
A method for evaluating the soundness of a steel material vertically embedded from the natural potential distribution E dis , combined with soil permeability evaluation (present invention 2):
A plurality of dissimilar steel materials, for example, galvanized steel, bare steel, and stainless steel, are embedded in the soil to be measured, and the respective natural potentials of the dissimilar steel materials are measured. Soil permeability is evaluated by applying to the soil permeability evaluation criteria prepared in the above, and further, in combination with the evaluation based on the potential distribution evaluation criteria in the first aspect of the invention, the natural potential distribution E Evaluation by dis can be performed with higher accuracy.
In general, during breathable soil, within 1 hour after being buried set is noble indicate the natural potential of the (positive direction), the poor soil breathable shows baser natural potential. By combining the evaluation standard that summarizes the relationship between the soil air permeability and these natural potentials with the above natural potential distribution Edis , whether the natural potential of the measurement object is due to air permeability or the surface properties of the steel (corrosion of the steel) noble of natural potential by products, noble of natural potential by corrosion products of zinc plating, it is possible to determine seemingly due noble of) the natural potential by drying, the evaluation by the natural potential distribution E dis It can be done more accurately.
埋設土壌の比抵抗分布ρｄｉｓを組み合わせた自然電位分布Ｅｄｉｓから鋼材の腐食性を推定し、対象鋼材の健全度をより精度よく総合的に評価する方法（本発明３）：
土壌中の鋼材がマクロセル腐食を生じると、土壌中にマクロセル電流Ｉが流れる。土壌は電気抵抗Ｒを有するので電位勾配ＩＲを生じる。電位勾配は自然電位分布Ｅｄｉｓと相関するので、埋設土壌の抵抗の分布を測定することによって、そこに流れる電流Ｉを求めることができる。土壌の比抵抗分布ρｄｉｓと自然電位分布Ｅｄｉｓとの関係を、実績値として予め蓄積しておき、両者の組合せから鋼材表面で生じるマクロセル電流Ｉを推定することができ、またこれと同時に、対象鋼材の腐食性の評価とともに、健全度を評価することができる。
なお、比抵抗分布ρｄｉｓは、例えば、比抵抗の測定法として当業者に既によく知られているＷｅｎｎｅｒ法（例えば、Ｗｅｎｎｅｒの四電極法）によって求めることができる。
A method of estimating the corrosivity of a steel material from a natural potential distribution E dis combined with a specific resistance distribution ρ dis of a buried soil and comprehensively evaluating the soundness of the target steel material (present invention 3):
When the steel material in soil causes macrocell corrosion, a macrocell current I flows in the soil. Since the soil has an electric resistance R, a potential gradient IR is generated. Since the potential gradient correlates with the natural potential distribution Edis , the current I flowing therethrough can be obtained by measuring the resistance distribution of the buried soil. The relationship between the specific resistance distribution ρ dis and the natural potential distribution E dis of the soil can be accumulated in advance as actual values, and the macrocell current I generated on the steel surface can be estimated from the combination of both, The soundness can be evaluated along with the evaluation of the corrosiveness of the target steel.
The specific resistance distribution ρ dis can be obtained by, for example, the Wenner method (for example, Wenner's four-electrode method) well known to those skilled in the art as a specific resistance measurement method.
本発明の埋設物健全度評価方法によれば、対象鋼材の自然電位Ｅｃｏｒ、自然電位分布Ｅｄｉｓおよびその分布の形状Ｅｐａｔを測定し、自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓと表面状態Ｐｃｏｒを電位分布評価基準にしたがって評価し（本発明１）、または、さらに土壌通気性評価基準を加味して評価し（本発明２）、あるいは、さらに腐食性評価基準を加味して評価する（本発明３）ことにより、非破壊で精度よく縦埋設された鋼材の健全度評価ができる。
そして、本発明によれば、評価を行うに必要とされる作業量が少なく、低コストで精度の高い健全度評価が可能になり、また、腐食性（腐食速度の大小）の推定によって、対象鋼材の維持管理対策における優先順位を容易につけることができ、さらに、対象鋼材の劣化要因が明らかになるので適正な補修対策を選定できる、という効果が奏される。
According to the buried object soundness evaluation method of the present invention, the natural potential E cor , the natural potential distribution E dis and the shape E pat of the distribution of the target steel are measured, and the natural potential E cor and the natural potential distribution E dis and the surface state are measured. P cor is evaluated according to the potential distribution evaluation standard (present invention 1), or further evaluated with the soil permeability evaluation standard (present invention 2), or further evaluated with the corrosive evaluation standard added. By (Invention 3), it is possible to evaluate the soundness of a non-destructive steel material vertically embedded with high accuracy.
According to the present invention, the amount of work required for the evaluation is small, and the soundness evaluation with high accuracy can be performed at a low cost. It is possible to easily prioritize the maintenance management measures for the steel material, and further, since the deterioration factor of the target steel material becomes clear, it is possible to select an appropriate repair measure.
本発明の実施例を、以下に図面とともに説明する。 Embodiments of the present invention will be described below with reference to the drawings.
土壌中に４０年間縦埋設されている対象鋼材に対して、本発明１〜３の埋設物健全度評価方法を適用して、健全度の評価を行った。
なお、評価は評点の合計によって行われるが、評点の合計点が高いほど、より厳しい腐食環境にあり、埋設物健全度評価は低くなるといえる。
The soundness evaluation was performed by applying the buried object soundness evaluation method according to the first to third aspects of the present invention to the target steel material vertically buried in the soil for 40 years.
In addition, although evaluation is performed by the total of a score, it can be said that it is in a severer corrosive environment and the evaluation of the soundness level of a buried object becomes low, so that the total score is high.
自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓ：
まず、対象鋼材が縦埋設（縦埋設長さ：２．６ｍ）されている土壌の地表面に照合電極を設置し、自然電位Ｅｃｏｒを測定した。また、０．２ｍ（任意）の間隔で対象鋼材から遠ざかるように照合電極を設置し、自然電位Ｅｃｏｒ、自然電位分布Ｅｄｉｓおよびその分布の形状Ｅｐａｔを測定した。
表1に、測定した自然電位Ｅｃｏｒ、自然電位分布Ｅｄｉｓを示す。
また、図２に、表1に示した自然電位分布Ｅｄｉｓをグラフ化した自然電位分布の形状Ｅｐａｔを示す。
なお、電位値は全て飽和硫酸銅電極基準（ＣＳＥ）で示した。
この測定結果を、表２に示す電位分布評価基準表と照合し、対象鋼材の表面状態を評価した。
Natural potential E cor and natural potential distribution E dis :
First, a reference electrode was installed on the ground surface of the soil in which the target steel material was vertically embedded (vertical embedded length: 2.6 m), and the natural potential E cor was measured. Moreover, the collation electrode was installed so that it might move away from the target steel material at intervals of 0.2 m (arbitrary), and the natural potential E cor , the natural potential distribution E dis and the shape E pat of the distribution were measured.
Table 1 shows the measured natural potential E cor and the natural potential distribution E dis .
FIG. 2 shows a shape E pat of the natural potential distribution obtained by graphing the natural potential distribution E dis shown in Table 1.
In addition, all the potential values were shown by a saturated copper sulfate electrode standard (CSE).
This measurement result was collated with the potential distribution evaluation standard table shown in Table 2 to evaluate the surface state of the target steel material.
自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓと表面状態Ｐｃｏｒに関する評価結果：
自然電位Ｅｃｏｒは対象鋼材の地表近辺（深さ：０ｍ）では、−５４５ｍＶの自然電位Ｅｃｏｒを示したが、対象鋼材から遠ざかるほど卑な電位を示し、２．６ｍ地点で最も卑な−６６０ｍＶの自然電位Ｅｃｏｒを示した。
測定した自然電位Ｅｃｏｒの範囲は、−５４５ｍＶ〜−６６０ｍＶであって、「Ｅｃｏｒ≧―８００ｍＶ」（評点２の欄）を満たすが、自然電位分布Ｅｄｉｓに関して、自然電位Ｅｃｏｒの差ΔＥは最大で１１５ｍＶ（＝６６０ｍＶ−５４５ｍＶ）であったため、表２の電位分布評価基準表におけるＥｄｉｓの評価基準によれば、評点は４（即ち、対象鋼材の表面状態Ｐｃｏｒは、「マクロセル：大」）となる。
Evaluation results regarding the natural potential E cor , the natural potential distribution E dis and the surface state P cor :
The natural potential E cor showed a natural potential E cor of −545 mV in the vicinity of the surface of the target steel (depth: 0 m). However, the natural potential E cor showed a lower potential as the distance from the target steel decreased, and the lowest at 2.6 m. A natural potential E cor of 660 mV was exhibited.
The range of the measured natural potential E cor is −545 mV to −660 mV and satisfies “E cor ≧ −800 mV” (the column of the rating 2), but the difference ΔE of the natural potential E cor with respect to the natural potential distribution E dis. maximum for a which was 115mV (= 660mV-545mV), according to the evaluation criteria for E dis in potential distribution criteria table Table 2, scores 4 (i.e., surface condition P cor of the subject steel, "macrocell: Large ").
なお、前記表２に示す評価基準は、以下に示す方法で策定したものである。
評点０（塗膜健全）：
鋼材表面にエポキシ樹脂塗装した亜鉛めっき鋼試験片を土壌中に埋設し、自然電位を測定した。試験片の自然電位の経時変化を図３に示す。埋設初期から埋設２０日経過時には、自然電位は−１１８から−２７６ｍＶで貴な値を示し、機器の表示値が不安定だった。しかし、埋設２６日経過時から、自然電位が急激に卑化し、−６００ｍＶ以下を示し、機器の表示値は安定した。これは、埋設初期では、塗膜が健全であったことが原因と考えられる。したがって、自然電位が貴な値を示し、機器の表示値が安定しない場合、塗膜が健全であるとした。
評点１および２（亜鉛めっき健全、下地鋼材露出）：
普通鋼および亜鉛試験片を土壌中に埋設し、自然電位を測定した。試験片の自然電位の経時変化を図４に示す。亜鉛めっき鋼の自然電位は試験期間中、最も貴な値で−８６３ｍＶであったが、普通鋼は−８００ｍＶ付近を示した。したがって、−８００ｍＶより卑な値を示す場合では、亜鉛めっきが健全であり、−８００ｍＶより貴な値を示す場合では、下地鋼材が露出しているとした。
評点３および４（マクロセル小および大）：
土壌中に縦埋設された鋼材の水平方向電位分布を調べたところ、その最貴値と最卑値の電位差が１００ｍＶ以下の場合、掘り上げ調査で軽微な腐食が確認された。また、電位差が１００ｍＶより大きい場合、掘り上げ調査で腐食貫通孔が発生するほどの激しい腐食が確認された。したがって、１００ｍＶを基準にマクロセルの大小を定めた。
Note that the evaluation criteria shown in Table 2 are established by the following method.
Score 0 (sound coating film):
A galvanized steel specimen coated with epoxy resin on the steel surface was embedded in the soil, and the natural potential was measured. The change with time of the natural potential of the test piece is shown in FIG. When 20 days have passed since the initial burial, the natural potential showed a precious value from −118 to −276 mV, and the display value of the device was unstable. However, since the lapse of 26 days from the time of burial, the natural potential rapidly decreased and showed −600 mV or less, and the display value of the device was stable. This is probably because the coating film was healthy in the initial stage of embedding. Therefore, when the natural potential shows a noble value and the display value of the device is not stable, the coating film is considered to be healthy.
Grades 1 and 2 (galvanized sound, underlying steel exposed):
Normal steel and zinc specimens were embedded in the soil and the natural potential was measured. FIG. 4 shows changes with time of the natural potential of the test piece. The natural potential of the galvanized steel was -863 mV, the most noble value during the test period, while the normal steel showed around -800 mV. Therefore, when the value is lower than −800 mV, the galvanization is sound, and when the value is higher than −800 mV, the base steel material is exposed.
Grades 3 and 4 (macrocell small and large):
When the horizontal potential distribution of the steel material vertically embedded in the soil was examined, when the potential difference between the most noble value and the most base value was 100 mV or less, a slight corrosion was confirmed by the excavation investigation. Further, when the potential difference is larger than 100 mV, it was confirmed that the corrosion was so severe that the corrosion through-hole was generated in the excavation investigation. Therefore, the size of the macro cell was determined based on 100 mV.
土壌通気性：
対象鋼材の付近に、複数の異種鋼材、即ち、土壌通気性評価用電極としての普通鋼および亜鉛めっき鋼、を０．５ｍの深さにまで差し込み、普通鋼および亜鉛の自然電位Ｅａｉｒを測定した。
この測定結果によれば、土壌通気性評価用電極としての自然電位Ｅａｉｒは、普通鋼では−６７３ｍＶ、また、亜鉛めっき鋼では−１０２３ｍＶであった。
この測定値を、表３に示す土壌通気性評価基準表と照合し、対象鋼材が埋設されている土壌の通気性を評価した。
Soil permeability:
A plurality of dissimilar steel materials, that is, ordinary steel and galvanized steel as soil breathability evaluation electrodes are inserted to a depth of 0.5 m in the vicinity of the target steel material, and the natural potential E air of ordinary steel and zinc is measured. did.
According to this measurement result, the natural potential E air as an electrode for evaluating soil air permeability was −673 mV for ordinary steel and −1023 mV for galvanized steel.
This measured value was collated with the soil air permeability evaluation standard table shown in Table 3, and the air permeability of the soil in which the target steel material was buried was evaluated.
土壌通気性に関する評価結果：
測定した普通鋼の自然電位Ｅａｉｒ（−６７３ｍＶ）は、表３の土壌通気性評価基準表のＦｅに関する評価基準の「−６００ｍＶ≧Ｅａｉｒ≧−７５０ｍＶ」の範囲内にあるから評点３であり、また、亜鉛めっき鋼の自然電位Ｅａｉｒ（−１０２３ｍＶ）は、同じく表３のＺｎに関する評価基準の「−１０００ｍＶ≧Ｅａｉｒ≧−１１００ｍＶ」の範囲内にあるから評点３となる。
したがって、対象鋼材が埋設されている土壌は評点３であって、通気性は中程度であり、腐食反応に必要な酸素の供給が良く、水分も含まれているという評価となった。
Evaluation results on soil permeability:
Since the measured natural potential E air (−673 mV) of ordinary steel is within the range of “−600 mV ≧ E air ≧ −750 mV” of the evaluation standard regarding Fe in the soil air permeability evaluation standard table of Table 3, it is a score 3. Further, the natural potential E air (−1023 mV) of the galvanized steel falls within the range of “−1000 mV ≧ E air ≧ −1100 mV” of the evaluation criteria for Zn in Table 3 as well, so that the score is 3.
Therefore, the soil in which the target steel material is buried has a rating of 3, the air permeability is medium, the supply of oxygen necessary for the corrosion reaction is good, and moisture is also included.
なお、前記表３として示す土壌通気性評価基準表は、次の方法で作成したものである。
まず、土壌通気性が鋼材電位に及ぼす影響を調べるため、普通鋼および亜鉛めっき鋼を種々の性状に調製した土壌に埋設して自然電位を測定した。
試験土壌は、市販の川砂および屋外で採取した黒ボク土を水道水で含水率が４０％程度とした自然含水状態および地表面に水面が現れるまで含水した冠水状態の２種類の含水条件に調製した。
表４に各土壌での鋼材の自然電位を示す。
自然含水状態では、普通鋼の自然電位は−６６５から−７１５ｍＶ、亜鉛めっき鋼は−１０２０から−１０６１ｍＶの貴な値を示した。
一方で、土壌の空隙に水分が充填し、通気性が低い冠水状態では、普通鋼は−８１２から−８４０ｍＶ、亜鉛めっき鋼は−１１７６から−１１８７ｍＶの卑な値を示した。
したがって、土壌通気性評価用電極の自然電位が普通鋼で−７５０ｍＶおよび亜鉛めっき鋼で−１１００ｍＶを基準値とし、基準値より卑な場合は「通気性：低」、基準値より貴な場合は、「通気性：中程度」とした。また、土壌が乾燥している場合では土壌中に空隙が多く存在し、水分が少ないため通気性が高く、通気性が中程度の土壌より電位値が貴な値を示すことが考えられる。そこで、普通鋼の自然電位が−６００ｍＶ、亜鉛めっき鋼は−１０００ｍＶより貴な値を示す場合は「通気性：高」とした。
鋼材の腐食が進行するためには酸素と水が必要であるが、「通気性：低」の土壌では、酸素の供給性が悪く、腐食は発生しにくいため、安全側の評点１とした。一方で、「通気性：高」の土壌では酸素の供給性が良いが、水分が少ないため評点２とした。「通気性：中程度」の土壌では酸素の供給性が良く、水分が含まれているため腐食しやすいと考え、危険側の評点３とした。
In addition, the soil permeability evaluation criteria table | surface shown as said Table 3 was created with the following method.
First, in order to investigate the effect of soil air permeability on the steel material potential, normal potential was measured by burying ordinary steel and galvanized steel in soil prepared in various properties.
The test soil is prepared in two types of water conditions: commercial river sand and outdoor black soil collected in tap water with a water content of about 40% and a submerged condition in which the water surface is submerged until the water surface appears. did.
Table 4 shows the natural potential of the steel material in each soil.
In a natural water-containing state, the natural potential of ordinary steel showed a noble value of −665 to −715 mV, and that of galvanized steel showed a noble value of −1020 to −1061 mV.
On the other hand, in the submerged state where moisture was filled in the voids of the soil and the air permeability was low, plain steel showed a low value of -812 to -840 mV, and galvanized steel showed a base value of -1176 to -1187 mV.
Therefore, the natural potential of the soil breathability evaluation electrode is -750 mV for ordinary steel and -1100 mV for galvanized steel, and the reference value is "breathability: low" if it is lower than the reference value. “Breathability: medium”. Further, when the soil is dry, there are many voids in the soil, and since there is little moisture, the air permeability is high, and the potential value may be higher than that of the soil with moderate air permeability. Therefore, when the natural potential of ordinary steel is -600 mV and the value of galvanized steel is more precious than -1000 mV, "breathability: high" is set.
Oxygen and water are required for the corrosion of steel materials to progress, but in the soil of “breathability: low”, oxygen supply is poor and corrosion does not easily occur. On the other hand, in the soil of “Breathability: High”, the oxygen supply property is good, but since the water is low, the score is 2. In the case of soil of “Breathability: Moderate”, oxygen supply is good and water is included.
土壌腐食性の推定：
対象鋼材近辺の深さ方向の土壌比抵抗ρの分布を測定した。
測定した土壌比抵抗ρの値と、表２に示す電位分布評価基準表における自然電位分布Ｅｄｉｓの値に対応する評点と組み合わせ、腐食性評価基準表と照合することで対象鋼材の腐食性を評価した。
表５に、測定した土壌比抵抗ρと測定位置（深さ）との関係を示す。
また、表６には、腐食性評価基準表を示す。
Estimating soil corrosion:
The distribution of soil resistivity ρ in the depth direction near the target steel was measured.
Combined with the value of the measured soil resistivity ρ and the score corresponding to the value of the natural potential distribution E dis in the potential distribution evaluation standard table shown in Table 2, and collated with the corrosivity evaluation standard table, the corrosivity of the target steel material evaluated.
Table 5 shows the relationship between the measured soil resistivity ρ and the measurement position (depth).
Table 6 shows a corrosivity evaluation standard table.
土壌腐食性の評価結果：
対象鋼材近くの土壌比抵抗ρは、地表面から深さ０．９ｍまで２００Ω・ｍ程度を示したが、それより深い位置では、７５Ω・ｍ程度の低い値を示し、Δρは１２５Ω・ｍであった。
また、自然電位分布Ｅｄｉｓに関する評点は、前述したように、表２の電位分布評価基準表における評点４であったため、Δρの値（＝１２５Ω・ｍ）と自然電位分布Ｅｄｉｓに関する評点４を表６の腐食性評価基準表にあてはめると、土壌腐食性は評点５（即ち、腐食性が非常に大である）となる。
したがって、対象鋼材は深さ０．９ｍ付近での土壌通気差でマクロセルを形成し、激しく腐食する可能性があるという評価となった。
Evaluation results of soil corrosion:
The soil resistivity ρ near the target steel was about 200 Ω · m from the ground surface to a depth of 0.9 m, but at a deeper position, it showed a low value of about 75 Ω · m, and Δρ was 125 Ω · m. there were.
Further, as described above, since the score regarding the natural potential distribution E dis is the score 4 in the potential distribution evaluation standard table of Table 2, the value of Δρ (= 125Ω · m) and the score 4 regarding the natural potential distribution E dis are When applied to the corrosivity evaluation standard table of Table 6, the soil corrosivity is score 5 (that is, the corrosivity is very large).
Therefore, it was evaluated that the target steel material may corrode severely by forming a macrocell due to a difference in soil aeration near a depth of 0.9 m.
埋設物健全度の総合評価：
前述した自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓに関する評価、土壌通気性に関する評価および土壌腐食性の評価をもとに、対象鋼材の健全度の総合評価を行うことができる。
表７に、健全度の総合評価を行うための総合評価表の一例を示す。
Overall assessment of soundness of buried objects:
Based on the above-described evaluation regarding the natural potential E cor and the natural potential distribution E dis, the evaluation regarding the soil air permeability, and the evaluation of the soil corrosiveness, a comprehensive evaluation of the soundness of the target steel material can be performed.
Table 7 shows an example of a comprehensive evaluation table for comprehensive evaluation of soundness.
表７に示す総合評価表にしたがって、実施例で対象とした鋼材の総合評価を行った場合、前述したように、自然電位Ｅｃｏｒと自然電位分布Ｅｄｉｓに関する評価は評点４、土壌通気性に関する評価は評点３および土壌腐食性の評価は評点５であるから、これらを合計した評点合計は１２である。
これを、表７の総合評価表にあてはめると、対象鋼材の健全度の総合評価は、健全度ランクＩＶの「腐食が著しいので更新する。」となり、また、講じるべき対策は、「更新時にランクIIと同様な防食対策を実施する。」となる。
なお、表８に、総合評価結果を示す。
According to the comprehensive evaluation table shown in Table 7, when the comprehensive evaluation of the steel materials targeted in the examples is performed, as described above, the evaluation regarding the natural potential E cor and the natural potential distribution E dis is the rating 4, regarding the soil air permeability. Since the evaluation is score 3 and the evaluation of soil corrosivity is score 5, the total score is 12.
If this is applied to the comprehensive evaluation table in Table 7, the overall evaluation of the soundness of the target steel will be “Renewed because corrosion is significant”, and the measures to be taken are “Rank when updated”. to implement a similar anti-corrosion measures and II. becomes. "
Table 8 shows the comprehensive evaluation results.
実施例で用いた対象鋼材について、前記の各評価および総合評価となったので、対象鋼材を土壌から堀り上げて、土壌中に埋め込まれていた箇所について目視による観察・調査を行った。
図５に、土壌中に埋め込まれていた対象鋼材の写真を示す。
対象鋼材を観察・調査した結果、図５からもわかるように、深さ０．７〜１．３ｍ付近で腐食が発生していること、深さ１．２ｍでは腐食による貫通孔発生箇所の存在が確認され、土壌中の対象鋼材は、著しい腐食状態に曝されていたことがわかる。
上記観察・調査結果は、本発明による対象鋼材健全度の各評価、総合評価と一致していることから、本発明の埋設物健全度評価方法によって、土壌中に縦埋設された鋼材の健全度を非破壊で精度よく評価し得ることが理解される。
Since it became each said evaluation and comprehensive evaluation about the object steel material used in the Example, the object steel material was dug up from soil, and the observation and investigation by visual observation were performed about the location embedded in soil.
FIG. 5 shows a photograph of the target steel material embedded in the soil.
As a result of observing and investigating the target steel materials, as can be seen from FIG. 5, corrosion occurs at a depth of 0.7 to 1.3 m, and presence of through-holes due to corrosion at a depth of 1.2 m. It is confirmed that the target steel material in the soil was exposed to a significant corrosion state.
Since the above observation / survey results are consistent with each evaluation and overall evaluation of the target steel soundness according to the present invention, the soundness of the steel vertically embedded in the soil by the embedded object soundness evaluation method of the present invention. It can be understood that non-destructive and accurate evaluation can be performed.
本発明によれば、土壌に縦埋設された鋼材の健全度評価を行うに必要とされる作業量が少なく、非破壊、低コストで精度の高い健全度評価が可能になり、また、腐食性（腐食速度の大小）の推定によって、対象鋼材の維持管理対策における優先順位を容易につけることができ、さらに、対象鋼材の劣化要因（例えば、「地際の腐食が卓越」、「土中のマクロセル腐食が卓越」、「いずれの腐食も軽微」等）が明らかになるので適正な補修対策を選定できることから、産業上の有益性は高いといえる。 According to the present invention, the amount of work required for performing the soundness evaluation of steel materials vertically embedded in the soil is small, enabling highly accurate soundness evaluation at a non-destructive, low cost, and corrosive (Evaluation of the corrosion rate) makes it easy to prioritize the maintenance management measures for the target steel, and the deterioration factors of the target steel (for example, “substantial corrosion is outstanding”, “ Since the macro-cell corrosion is “excellent” and “all of the corrosion is minor” etc.), it is possible to select appropriate repair measures.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2016008423A JP6621137B2 (en) | 2016-01-20 | 2016-01-20 | Method for evaluating the soundness of buried objects |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2016008423A JP6621137B2 (en) | 2016-01-20 | 2016-01-20 | Method for evaluating the soundness of buried objects |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2017129435A JP2017129435A (en) | 2017-07-27 |
| JP6621137B2 true JP6621137B2 (en) | 2019-12-18 |
Family
ID=59396280
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2016008423A Active JP6621137B2 (en) | 2016-01-20 | 2016-01-20 | Method for evaluating the soundness of buried objects |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP6621137B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6705036B1 (en) * | 2019-03-06 | 2020-06-03 | 西日本電信電話株式会社 | Steel pipe column deterioration prediction system |
| CN114660158B (en) * | 2022-01-30 | 2022-12-20 | 北京市鼎新新技术有限责任公司 | Medium-low pressure gas pipe network corrosion risk comprehensive detection and evaluation method and device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0716993Y2 (en) * | 1985-05-21 | 1995-04-19 | 日本防蝕工業株式会社 | Rotary multi-point simultaneous potential measurement device |
| JP3315189B2 (en) * | 1993-04-06 | 2002-08-19 | 東京瓦斯株式会社 | Corrosion spot detection method for cast iron pipes buried in soil |
| JP5033648B2 (en) * | 2008-01-10 | 2012-09-26 | 中国電力株式会社 | Diagnosis method of steel material buried in soil |
| JP3198840U (en) * | 2015-05-14 | 2015-07-23 | 日進工業株式会社 | Prop road boundary inspection system |
-
2016
- 2016-01-20 JP JP2016008423A patent/JP6621137B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| JP2017129435A (en) | 2017-07-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kim et al. | Global and local parameters for characterizing and modeling external corrosion in underground coated steel pipelines: A review of critical factors | |
| US10001436B2 (en) | In-situ measurement of corrosion in buried pipelines using vertically measured pipe-to-soil potential | |
| Vedalakshmi et al. | Reliability of Galvanostatic Pulse Technique in assessing the corrosion rate of rebar in concrete structures: Laboratory vs field studies | |
| JP6621137B2 (en) | Method for evaluating the soundness of buried objects | |
| Popov et al. | Cathodic protection of pipelines | |
| Ezzeldin et al. | Accelerated wet/dry corrosion test for buried corrugated mild steel | |
| Jun et al. | Methodologies for evaluation of corrosion protection for ductile iron pipe | |
| JP6370701B2 (en) | Soil corrosion evaluation method | |
| Tan et al. | Field and laboratory assessment of electrochemical probes for visualizing localized corrosion under buried pipeline conditions | |
| Wang et al. | Electrochemical characterization of the soils surrounding buried or embedded steel elements | |
| Tan et al. | New electrochemical methods for visualizing dynamic corrosion and coating disbondment processes on simulated pipeline conditions | |
| Tan et al. | Monitoring dynamic corrosion and coating failure on buried steel using an multi-electrode array | |
| JP2017129436A (en) | Soil permeability evaluation method and soil permeability measuring apparatus | |
| Tan et al. | An overview of recent progresses in acquiring, visualizing and interpreting pipeline corrosion monitoring data | |
| Huo | A study of the effects of potential excursions and the environment on the effectiveness of cathodic protection | |
| Choi et al. | A Galvanic Sensor for Monitoring the Corrosion Damage of Buried Pipelines: Part 3—Correlation of Probe Current to Cathodic Protection and Stray Current | |
| Hamsa et al. | An Investigation of Soil Resistivity Level at UTHM Pagoh Campus | |
| Tan et al. | An overview of new progresses in understanding pipeline corrosion | |
| Zamanzadeh et al. | Galvanized steel pole and lattice tower corrosion assessment and corrosion mitigation | |
| Kiviste et al. | Half-cell potential mapping for corrosion risk evaluation of prestressed concrete ribbed panels from agricultural building after 20 years of service | |
| Putra et al. | Effect of Soil Composition on the Corrosion Rate of Underground Water Distribution Pipes in Natural Environment | |
| Tan et al. | Visualizing dynamic corrosion and coating disbondment processes on simulated pipeline conditions | |
| Choi et al. | A Galvanic Sensor for Monitoring the Corrosion Damage of Buried Pipelines: Part 2Correlation of Sensor Output to Actual Corrosion Damage of Pipeline in Soil and Tap Water Environments | |
| Barker et al. | Determining the Behavior of Sulfur Compounds in Controlling Preferential Weld Corrosion in CO2-saturated Brine | |
| Bourreau et al. | Better understanding of tide's influence on half-cell potential and electrical resistivity measurements for reinforced concrete in marine environment |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20160209 |
|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20180605 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20190327 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20190508 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20190628 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20191114 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20191114 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 6621137 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |