JP4469066B2 - Method for obtaining specific resistance distribution and method for detecting damage position of impermeable layer - Google Patents

Description

【００２１】
この比抵抗の補正は地盤又は埋立地の複数の点に対して行う。また、解析結果の電位分布と本測定工程時の電位分布が一致するまで、必要に応じて繰り返し行う。こうして算出した比抵抗分布を設定した解析モデルによって例えば遮水層近傍の電位分布を算出する。
【００２２】
＜ハ＞損傷位置の推定
遮水層１の間に電流を流し、遮水層１の近傍に発生した電位分布を測定する。
本測定工程時の電位分布から解析工程時の電位分布を引いて差分電位分布とする。
内部給電電極を＋とし、外部給電電極を−とした差分電位分布図上で最も電位が低い位置が損傷の中心位置と推定できる。
この最も電位が低い位置を推定する方法として、以下の方法が使用できる。
第１の方法として、損傷位置と仮定して損傷周辺の電位変化を示す理論式に当てはめて求めた理論値と、前記差分電位分布との平均二乗誤差を求め、この誤差が最も小さくなる損傷位置を特定する方法が利用できる。
ここで、理論式を以下に示す。
【００２３】
【式２】

【００２４】
第２の方法として、数値シミュレーション解析から求めた電位分布と、前記差分電位分布との一致性から損傷位置を特定する方法が利用できる。
【００２５】
【実施例２】
遮水層を２重構造にする場合の実施例について以下に説明する。
＜イ＞外部給電電極を遮水層の内部に設置する場合
図６に概要図を示す。
この場合、外部給電電極３１と外部基準電極３０を上部遮水層１１と下部遮水層１２に囲まれた範囲に設置する。
こうする事によって、上部遮水層１１が損傷した場合にその位置を検知することが可能となる。
なお、内部給電電極と電位測定電極を下部遮水層１２の下方に設置した場合は、下部遮水層１２の損傷位置を検知することができる。
【００２６】
＜ロ＞給電電極と電位測定電極を遮水層の内部に設置する場合
図７に概要図を示す。
この場合、埋立地７の内側と外側の両方に給電電極（３３、３５）と基準電極（３２、３４）を設置する。
この場合は、上部遮水層１１の損傷位置も下部遮水層１２の損傷位置も別々に検知することができる。
【００２７】
＜ハ＞その他の場合
図２に示す遮水層を２重構造にすることも当然可能である。こうする事によって、上部遮水層１１と下部遮水層１２の両方が破損した場合に、上部遮水層１１の損傷位置を検知することができる。
また、図２に示す遮水層を２重構造とし、外部給電電極３１を埋立地内部に、内部給電電極（２１、２２）及び電位測定電極４を埋立地外部の下部遮水層１２の近傍に設置することもできる。こうする事によって、上部遮水層１１と下部遮水層１２の両方が破損した場合に、下部遮水層１２の損傷位置を検知することができる。
【００２８】
【本発明の効果】
本発明の比抵抗分布を求める方法は以上説明したようになるから次のような効果を得ることができる。
＜イ＞測定した電位分布と算出する電位分布が一致するような比抵抗分布を求める。このため、地盤又は埋立地の比抵抗分布を精度良く求めることができる。
＜ロ＞従来の方法に比べて測定電極の数を増やしたりしなくても、精度良く比抵抗分布を求めることができる。従って、精度を向上させるための測定器の設置に、費用と時間をかけなくてもよい。
【００２９】
また、本発明の遮水層の損傷位置検知方法は以上説明したようになるから次のような効果を得ることができる。
＜イ＞遮水構造物の遮水層の損傷位置を精度良く検知することができる。
＜ロ＞損傷位置を推定する前に、内外の導電性の不均一性、給電電極の位置による電位分布の影響、遮水構造物の形状による電位分布の影響などの背景電位分布による影響を取り除く。このため、精度よく遮水層の損傷位置を検知できる。
＜ハ＞従来の方法に比べて測定電極の数を増やしたりしなくても、精度良く遮水層の損傷位置を検知できる。従って、精度を向上させるために、埋立地の建設費を増加させることがない。
＜ニ＞形状が複雑な埋立地に適用した場合でも測定電極を増やすことなく精度良く遮水層の損傷位置を検知できる。
＜ホ＞埋立中の埋立地に適用した場合でも、埋立の進行に伴う電気的な特性変化に影響されずに精度良く遮水層の損傷位置を検知できる。
【図面の簡単な説明】
【図１】本発明の比抵抗分布を求める場合の概要図
【図２】本発明の内部給電電極間に給電する場合の概要図
【図３】内部給電電極と外部給電電極間に給電する場合の概要図
【図４】測定した電位分布の等電位線図の一表示例
【図５】差分電位分布の等電位線図の一表示例
【図６】遮水層が２重構造で外部給電電極を遮水層の内部に設置する場合の実施例の概要図
【図７】遮水層が２重構造で給電電極と電位測定電極を遮水層の内部に設置する場合の実施例の概要図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a specific resistance distribution of a ground or a landfill and a damage position detection method for a water shielding layer of a water shielding structure.
[0002]
[Prior art]
The specific resistance distribution of the ground or landfill can be obtained by placing the measurement electrodes densely and measuring directly by the four-electrode method, or by measuring the ground resistance of each of the densely arranged measurement electrodes and surrounding the measurement electrodes There is a method obtained by obtaining the specific resistance.
In addition, taking a water-impervious layer in a landfill as an example, a conventional method for detecting a damage position of a water-impervious layer is a method for detecting the position of a water-impervious layer between power supply electrodes installed with a water-impervious layer electrically sandwiched between ( For example, a current is passed between the inside and outside of the landfill, and the potential distribution generated above or below the water shielding layer or between the water shielding layers in the case of a double water shielding layer structure is measured. Then, the damage position of the water shielding layer is detected from the potential distortion generated around the damage position.
[0003]
[Problems to be solved by the present invention]
The conventional method for obtaining the specific resistance distribution has the following problems.
<A> In order to obtain the specific resistance distribution accurately and directly, it is necessary to arrange the measurement electrodes densely. For this reason, it takes cost and time to install the measurement electrode.
<B> Since the error in the end portion in the range where the measurement electrodes are arranged increases, it is necessary to increase the electrode density particularly in the end portion. When applied to landfills, the measurement range becomes wider as landfill progresses, so in order to arrange the electrodes so that the electrodes at the end always become dense, arrange the electrodes densely in a wide range. There is a need.
<C> When the shape of the measurement range is complicated (such as the final disposal site), there is a problem that the measurement error increases.
[0004]
The conventional method for detecting the damage position of the water shielding layer has the following problems.
<I> When waste is landfilled in the landfill, the potential distribution is affected by non-uniformity of the material of the landfill waste and its distribution. As a result, the potential distortion generated around the damaged position is also affected, and the error may increase.
<B> The above problem is also caused by the difference in the position of the feeding electrode and the shape of the landfill.
<C> In landfills during landfill, the electrical conditions (for example, resistivity distribution) in the landfill change daily as landfill progresses. Therefore, when solving with a fixed model, errors increase as landfill progresses. There is a possibility that the damage position of the water shielding layer cannot be detected accurately.
[0005]
[Object of the present invention]
The present invention has been made in order to solve the conventional problems as described above, and an object thereof is to accurately obtain the specific resistance distribution of the ground or landfill.
Or it aims at detecting the damage position of the water shielding layer of a water shielding structure with high precision using the specific resistance distribution calculated | required with high precision.
Or damage to the water shielding layer with high accuracy without being affected by the background potential distribution, such as non-uniformity of conductivity inside and outside, influence of potential distribution due to the position of the feeding electrode, and influence of potential distribution due to the shape of the water shielding structure The purpose is to detect the position.
Or, in the case of a landfill during landfill, the electrical conditions in the landfill change daily with the progress of landfill. An object of the present invention is to detect the damage position of the water shielding layer with high accuracy without being affected by the potential distribution.
The present invention achieves at least one of these objects.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the method for detecting a damage position of a water shielding layer according to the present invention is a method for detecting a damage position of a water shielding layer having an electrically high resistance. Preliminary measurement step of installing power supply electrodes in at least two places on one side and passing a current between the power supply electrodes to measure the potential distribution in the ground or landfill,
Assuming the initial value of the resistivity distribution in the analysis model of the same shape as the ground or landfill, the ground potential distribution calculated by giving the current of the ground or landfill during the preliminary measurement process to this resistivity distribution The potential distribution in the ground measured in the preliminary measurement step is compared, the initial value of the specific resistance distribution is changed based on the comparison result, and the calculated potential distribution is almost the same as the potential distribution measured in the preliminary measurement step. An analysis step of calculating a specific resistance distribution near the water shielding layer so as to have the same distribution, and calculating a potential distribution near the water shielding layer from the specific resistance distribution, assuming that a current flows between the water shielding layers. The main measurement process, regardless of the order of the analysis process, the main measurement process for measuring the potential distribution generated in the vicinity of the impermeable layer by passing a current between the impermeable layers, the potential distribution calculated in the analysis process, The differential potential distribution is calculated from the difference from the potential distribution measured in the measurement process. A comparison step of forming, is made of the estimated step of estimating the presence or absence and the position of the damage from the difference potential distribution.
[0007]
[Embodiments of the Invention]
Hereinafter, an embodiment of a method for obtaining a specific resistance distribution according to the present invention will be described with reference to FIG.
[0008]
<A> Preliminary measurement process The preliminary measurement process is a process of measuring the potential distribution of the ground or landfill.
The potential distribution is measured by, for example, the potential measuring electrode 4 installed at a predetermined interval on the ground or a landfill. The potential measuring electrodes 4 have, for example, a lattice shape with equal intervals in the vertical and horizontal directions, and are arranged in a plurality of stages at intervals in the depth direction.
Here, it is necessary to grasp the current of the ground or landfill when measuring the potential distribution. For this reason, for example, a known current is passed between the feeding electrodes 2 and the potential distribution is measured by the potential measuring electrode 4. Moreover, you may utilize the natural current etc. which exist in the ground or a landfill.
The potential distribution is measured, for example, by passing a current between the power supply electrodes 2 and measuring the potential difference between the potential measurement electrode 4 and the reference electrode 8. For example, an alternating current, an alternating current or the like is used as a current flowing between the power supply electrodes 2.
[0009]
<B> Calculation step The calculation step is a step of calculating a specific resistance distribution (hereinafter referred to as a specific resistance distribution) of the ground or landfill based on the potential distribution during the preliminary measurement step.
First, an analysis model having the same shape as the ground 70 is created. Then, an initial value of the specific resistance distribution is given on the analysis model.
Next, in the analysis model given the initial value of the specific resistance distribution, for example, the potential distribution of the ground 70 is calculated on the assumption that a current is passed between the feeding electrodes.
The calculated potential distribution is compared with the potential distribution measured in the preliminary measurement step, and the initial value of the specific resistance of the portion where the potential distribution is different is corrected.
Then, a specific resistance distribution is calculated such that the calculated potential distribution is substantially the same as the potential distribution in the preliminary measurement process.
[0010]
Embodiments of a method for detecting a damage position of a water shielding layer of the present invention will be described below with reference to the drawings.
[0011]
<A> Installation of feeding electrode and potential measurement electrode Hereinafter, description will be given with reference to FIG.
The water-impervious structure may be anything having a water-impervious structure such as a landfill for general waste or industrial waste, a reservoir, and the landfill is taken as an example in the embodiment.
The ground of the planned landfill site is excavated, and an electrically high resistance impermeable layer 1 is laid on the bottom and side surfaces thereof. For example, a rubber sheet or the like is used for the water shielding layer.
In the vicinity of the water shielding layer 1, potential measuring electrodes 4 are installed at predetermined intervals. Here, the vicinity of the impermeable layer may be in the vicinity of the impermeable layer 1 and may be in contact with the impermeable layer 1. For example, it is installed in a lattice form with equal vertical and horizontal intervals.
At least two internal feeding electrodes (21, 22) are installed on the side of the water shielding layer 1 on which the potential measuring electrode 4 is installed.
For example, an external power supply electrode 31 is installed outside the landfill 7.
Moreover, it is desirable to install an internal reference electrode 20 and an external reference electrode 30 inside and outside the landfill 7 respectively.
In FIG. 2, the potential measuring electrode 4 is installed on the upper surface of the water shielding layer 1, but it may be installed on the lower surface of the water shielding layer 1.
[0012]
<B> Specific resistance distribution The specific resistance distribution near the impermeable layer is obtained.
For example, first, a current is passed through one side of the water shielding layer 1 as a boundary, and the potential distribution generated in the vicinity of the water shielding layer 1 is measured.
The potential distribution is measured by, for example, passing a current between the internal feeding electrodes (21, 22) and measuring the potential distribution generated in the vicinity of the water shielding layer 1 as a potential difference between the potential measuring electrode 4 and the internal reference electrode 20. By doing. Here, even if the external reference electrode 30 is used instead of the internal reference electrode 20, the potential distribution may be measured as a potential difference between the potential measurement electrodes without using the reference electrode.
As the current flowing between the internal power supply electrodes (21, 22), for example, an alternating current, an alternating current, or the like whose polarity is alternately changed is used.
When power is supplied between power supply electrodes (for example, between internal power supply electrodes) installed only on one side with the water shielding layer as a boundary, the potential distribution can be obtained without being affected by the presence or absence of damage to the water shielding layer. This is because the current passing through the damaged portion is much smaller than the current flowing in the landfill 7.
[0013]
The specific resistance distribution in the vicinity of the water shielding layer is obtained so as to coincide with the potential distribution measured by the above method.
The specific resistance distribution calculation method assumes, for example, a landfill having the same shape as the landfill 7 (hereinafter referred to as an analytical model), and assumes that a current flows between the internal feeding electrodes in the same manner as the above-described potential distribution was measured. Then, a specific resistance distribution is obtained so as to show a potential distribution substantially the same as the measured potential distribution.
[0014]
<C> Analysis process The analysis process is a process of calculating the potential distribution in the vicinity of the impermeable layer 1 using the analysis model having the specific resistance distribution calculated as described above.
For example, on the analysis model, it is assumed that a current flows between the internal power supply electrode 21 and the external power supply electrode 31 as shown in FIG. 3, and the potential distribution generated by the specific resistance distribution near the water shielding layer is calculated.
[0015]
<D> Main Measurement Step The main measurement step is a step of measuring a potential distribution generated in the vicinity of the water shielding layer 1 by passing a current between the water shielding layers 1.
For example, as shown in FIG. 3, power is supplied between the internal power supply electrode 21 (or 22) and the external power supply electrode 31, and the potential distribution is measured by the potential measurement electrode 4.
FIG. 4 shows an example of an equipotential diagram of the potential distribution measured during the main measurement process.
[0016]
<E> Estimation of damage position The damage position is estimated using the potential distribution calculated in the analysis step and the potential distribution measured in the main measurement step. Note that the order of the analysis step and the main measurement step may be the first or the second.
The difference between the potential distribution during the analysis step and the potential distribution during the main measurement step is defined as a differential potential distribution.
FIG. 5 shows an example of an equipotential diagram of the differential potential distribution.
Here, the position where the equipotential lines of the differential potential distribution are illustrated densely is estimated as the damage position. For example, an equipotential diagram of the difference potential distribution is created, and if there is a concave (or convex) portion, the lowest position (or higher position) of the depression is estimated as the damage position.
[0017]
[Example 1]
[0018]
<A> Measurement of potential distribution The measurement of the potential distribution is performed with the potential measuring electrodes 4 installed in a grid pattern at a pitch of 5 to 30 m, for example, on the ground or landfill.
For example, a state in which no current flows for a certain period of time at regular intervals appears between the feeding electrodes, and an alternating current having a waveform whose polarity changes is passed.
[0019]
<B> Calculation of resistivity distribution First, an analysis model having the same shape as the ground 70 or the landfill 7 is created. And the initial value of specific resistance distribution is given to the inside of the near landfill corresponding to the impermeable layer 1 on the analysis model, for example.
Next, in the analysis model that gives the initial value of the specific resistance distribution, the potential distribution in the vicinity of the impermeable layer is calculated on the assumption that a current flows between the feeding electrodes. This result is set as a potential based on the analysis result.
The potential based on the analysis result is compared with the potential of the potential distribution during the main measurement process, and the initial value of the specific resistance distribution is corrected by the following equation.
[0020]
[Formula 1]

[0021]
The specific resistance is corrected for a plurality of points on the ground or landfill. Moreover, it repeats as needed until the electric potential distribution of an analysis result and the electric potential distribution at the time of this measurement process correspond. For example, the potential distribution in the vicinity of the water shielding layer is calculated by an analysis model in which the calculated specific resistance distribution is set.
[0022]
<C> A current is passed between the estimated impermeable layers 1 at the damaged position, and the potential distribution generated in the vicinity of the impermeable layers 1 is measured.
The potential distribution during the analysis process is subtracted from the potential distribution during the main measurement process to obtain a differential potential distribution.
It can be estimated that the position where the potential is lowest on the differential potential distribution diagram where the internal feeding electrode is + and the external feeding electrode is-is the center position of damage.
As a method for estimating the position having the lowest potential, the following method can be used.
As a first method, a mean square error between a theoretical value obtained by applying a theoretical expression indicating a potential change around the damage assuming a damage position and the difference potential distribution is obtained, and the damage position where the error is minimized A method for identifying the can be used.
Here, the theoretical formula is shown below.
[0023]
[Formula 2]

[0024]
As a second method, a method of specifying a damage position from the coincidence between the potential distribution obtained from the numerical simulation analysis and the difference potential distribution can be used.
[0025]
[Example 2]
Examples in which the water shielding layer has a double structure will be described below.
<A> When an external power supply electrode is installed inside a water shielding layer, a schematic diagram is shown in FIG.
In this case, the external power supply electrode 31 and the external reference electrode 30 are installed in a range surrounded by the upper water shielding layer 11 and the lower water shielding layer 12.
This makes it possible to detect the position of the upper impermeable layer 11 when it is damaged.
In addition, when the internal power feeding electrode and the potential measurement electrode are installed below the lower impermeable layer 12, the damage position of the lower impermeable layer 12 can be detected.
[0026]
<B> When the feeding electrode and the potential measuring electrode are installed inside the water shielding layer, a schematic diagram is shown in FIG.
In this case, the feeding electrodes (33, 35) and the reference electrodes (32, 34) are installed both inside and outside the landfill 7.
In this case, the damage position of the upper impermeable layer 11 and the damage position of the lower impermeable layer 12 can be detected separately.
[0027]
<C> In other cases, it is naturally possible to make the water shielding layer shown in FIG. By carrying out like this, when both the upper impermeable layer 11 and the lower impermeable layer 12 are damaged, the damage position of the upper impermeable layer 11 can be detected.
Also, the water shielding layer shown in FIG. 2 has a double structure, the external feeding electrode 31 is located inside the landfill, and the internal feeding electrodes (21, 22) and the potential measuring electrode 4 are located near the lower water shielding layer 12 outside the landfill. It can also be installed. By carrying out like this, when both the upper impermeable layer 11 and the lower impermeable layer 12 are damaged, the damage position of the lower impermeable layer 12 can be detected.
[0028]
[Effect of the present invention]
Since the method for obtaining the specific resistance distribution of the present invention is as described above, the following effects can be obtained.
<A> A specific resistance distribution is obtained so that the measured potential distribution matches the calculated potential distribution. For this reason, the specific resistance distribution of the ground or landfill can be obtained with high accuracy.
<B> The specific resistance distribution can be obtained with high accuracy without increasing the number of measurement electrodes as compared with the conventional method. Therefore, it is not necessary to spend cost and time to install a measuring instrument for improving accuracy.
[0029]
Moreover, since the method for detecting the damage position of the water shielding layer of the present invention has been described above, the following effects can be obtained.
<I> It is possible to accurately detect the damage position of the water shielding layer of the water shielding structure.
<B> Before estimating the damage position, remove the influence of background potential distribution such as non-uniformity of internal and external conductivity, influence of potential distribution due to the position of the feed electrode, and influence of potential distribution due to the shape of the water shielding structure. . For this reason, the damage position of the water shielding layer can be detected with high accuracy.
<C> Even if the number of measurement electrodes is not increased as compared with the conventional method, the damage position of the water shielding layer can be detected with high accuracy. Therefore, in order to improve the accuracy, the construction cost of the landfill is not increased.
<D> Even when applied to a landfill with a complicated shape, it is possible to accurately detect the damage position of the water shielding layer without increasing the number of measurement electrodes.
<E> Even when it is applied to a landfill during landfill, it is possible to accurately detect the damage position of the water shielding layer without being affected by changes in electrical characteristics accompanying the progress of landfill.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for obtaining a specific resistance distribution according to the present invention. FIG. 2 is a schematic diagram when power is supplied between internal power supply electrodes of the present invention. Fig. 4 Example of equipotential diagram of measured potential distribution Fig. 5 Example of equipotential diagram of differential potential distribution Fig. 6 External power supply with double structure Outline diagram of the embodiment when the electrode is installed inside the impermeable layer. [Fig. 7] Outline of the embodiment when the impermeable layer has a double structure and the feeding electrode and the potential measuring electrode are installed inside the impermeable layer. Figure

Claims (2)

In the method of detecting the damage position of an electrically high resistance water shielding layer,
Install feed electrodes at least at two locations on one side of the ground with the impermeable layer as the boundary,
A preliminary measurement step of measuring the potential distribution in the ground or landfill by passing an electric current between the feeding electrodes;
Assuming the initial value of resistivity distribution in the analysis model of the same shape as the ground or landfill,
Underground potential distribution calculated by giving the ground or landfill current during the preliminary measurement process to this resistivity distribution,
Compare the ground potential distribution measured in the preliminary measurement step,
Based on the comparison result, the initial value of the resistivity distribution is changed,
Calculate the specific resistance distribution near the impermeable layer so that the calculated potential distribution is almost the same as the potential distribution measured in the preliminary measurement process,
Assuming that a current was passed between the impermeable layers,
An analysis step of calculating a potential distribution in the vicinity of the impermeable layer from the specific resistance distribution;
This measurement process, regardless of the analysis process and order,
A main measurement process for measuring a potential distribution generated in the vicinity of the impermeable layer by passing an electric current between the impermeable layers;
A comparison step of creating a differential potential distribution from the difference between the potential distribution calculated in the analysis step and the potential distribution measured in the main measurement step;
It consists of an estimation process for estimating the presence and location of damage from the differential potential distribution,
A method for detecting the damage position of a water shielding layer . In the method for detecting a damage position of the water shielding layer according to claim 1 ,
The water shielding layer has a double structure consisting of two layers,
Detecting at least one damaged position of the water shielding layer,
A method for detecting the damage position of a water shielding layer.

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