JP2000338258A - Fill dam control system by specific resistance tomography method and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a dam inexpensively over a long term with a simple configuration. SOLUTION: A temperature sensor 6 for detecting the temperature of a fill dam 3 and electrodes Pa1-Pan and Pb1-Pbn for detecting specific resistance are buried into the fill dam 3 in advance when the fill dam 3 (4, 3A) is to be constructed by obtaining the relationship among the specific resistance and each physical property of temperature, gap ratio, and saturation by an experiment in advance and acquiring the basic elements for analysis and abnormality judgment. After the fill dam 3 is completed, temperature data that is collected from the temperature sensor 6 being buried into the fill dam 3 and potential data that is measured by an electrical prospecting device 2 are processed by a computer 5 for creating a temperature distribution and a specific resistance distribution with time, then the created physical property distribution and specific resistance distribution are compared based on a relation expression that is obtained by an experiment in advance, it is judged whether the change in the specific resistance distribution is abnormal or normal based on the comparison, and an abnormal site is detected according to the region of the specific resistance region when it is judged to be abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a fill dam management system using a resistivity tomography method and a management method thereof.

[0002]

2. Description of the Related Art Conventionally, the management of a fill dam (a dam whose main body is made of a debris material) is conventionally performed by deformation observation using a surface displacement meter or a stratified subsidence meter, stress state observation using an earth pressure gauge, pore water pressure gauge or an observation hole. Observations are made by observation of infiltration lines based on water levels and water leakage by flow meters.

[0003] However, in the conventional fill dam management, there is a problem in long-term reliability of the observed value due to aging of the sensor in observation by an instrument. In addition, the observed value is point information, and in order to specify the abnormal location of the embankment two-dimensionally,
There is a problem that a large number of observation points are required, and the observation work is troublesome. The term “two-dimensional” as used herein means that the underground structure or the topography changes only in the measurement direction and the depth direction, and does not change in the direction (depth direction) orthogonal to the vertical section under the measurement line. Further, increasing the number of observation points does not necessarily mean that desired information can be obtained. In addition, since the observation point was located inside the embankment or the foundation ground, no information was obtained on the portion where the embankment and the foundation ground, which greatly contribute to the safety of the impermeable section, were in contact. Therefore, application of two-dimensional non-destructive exploration by resistivity tomography is conceivable to identify an abnormal part of the fill dam.

In the electrical resistivity tomography method, an electrode is installed underground using a boring hole, a tunnel, or the like around a portion to be searched, in contrast to an electrical detection method in which electrodes are installed only on the ground surface. This is a method to analyze the underground resistivity structure with higher accuracy. In addition, the resistivity monitoring is carried out over time using the electric prospecting resistivity method or resistivity tomography method,
It is a technique to estimate the change of underground saturation and porosity from the obtained change of resistivity.

[0005]

When the resistivity tomography method is used to specify an abnormal portion of a fill dam, a boring hole is formed and an electrode is provided after the dam is built. It was difficult to install electrodes in the reservoir on the upstream side and at the bottom of the embankment. In addition, it was difficult to transmit current because the water-blocking part on the downstream side of the embankment was covered with rock material. Also, in the general resistivity tomography method,
It is difficult to install electrodes all around the area to be searched, and there is a problem in the analysis accuracy in an area where electrodes cannot be installed. Furthermore, since the resistivity structure of the portion to be explored is unknown, it was necessary to find an initial model that has a large effect on the analysis result by repeating trial and error. Also, in general resistivity monitoring for natural ground, many assumptions are required to identify the main factors of the obtained resistivity change, and especially in the civil engineering field, external conditions given to the resistivity of the stratum are required. The effects have not been taken into account much.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned problems, and can easily and accurately detect an abnormal portion of a fill dam with a simple configuration, and can perform management at low cost for a long period of time. It is an object of the present invention to provide a fill dam management system using a resistivity tomography method and a management method thereof.

[0007]

A fill dam management system using a resistivity tomography method according to the present invention is determined in advance at the time of constructing a levee body comprising a water-blocking portion and a shell portion upstream and downstream of the water-blocking portion. Based on the predetermined arrangement, a large number of electrodes buried along substantially the outer periphery of a predetermined cross section of the water shielding portion, and the electrodes are electrically connected to each other, and a current is transmitted by an arbitrary current electrode among these electrodes. An electric probe that measures a potential difference between the other potential electrodes except the current electrode, and outputs the measured value to the outside, and is electrically connected to the electric probe, controls the electric probe, and controls the electric probe. A computer for analyzing a specific resistance structure of a predetermined cross section based on a measurement value input from the device, and generating a first specific resistance distribution from the specific resistance structure of the predetermined cross section; After a specified time from creation In order to create a post-new resistivity distribution,
The changes in resistivity distribution are monitored over time by comparing these resistivity distributions that differ over time, and when an abnormal change in resistivity is found in the resistivity distribution, an abnormal portion of the embankment corresponding to the abnormal portion is detected. Is detected.

[0008] In the fill dam management system based on the resistivity tomography method according to the present invention, when the embankment composed of the water impermeable portion and the outer shell on the upstream and downstream sides of the water impermeable portion is constructed, the electrodes are arranged in a predetermined arrangement. A large number of the electrodes are buried along the outer periphery of a predetermined cross section of the water-blocking portion based on the above, and an electric probe is electrically connected to the electrodes, and the electric probe transmits a current through an arbitrary current electrode among these electrodes. Then, a potential difference between the other potential electrodes except the current electrode is measured, the measured value is output to the outside, and the electric probe is controlled by a computer electrically connected to the electric probe, and the electric probe is controlled. The specific resistance structure of a predetermined cross section is analyzed based on the measurement value input from the exploration device, and a first specific resistance distribution is created from the specific resistance structure of the predetermined cross section.
A new specific resistance distribution is sequentially created after a predetermined time has elapsed from the time of the creation of the second time, and a change in the specific resistance distribution is monitored over time by comparing these specific resistance distributions different over time. When a specific resistance change is detected, the abnormal part of the embankment corresponding to the abnormal part is detected, so that the non-destructive exploration can accurately detect the abnormal part and simplify the measurement equipment. Thus, precise management over a long period of time is possible.

Further, in the method for managing a fill dam according to the resistivity tomography method according to the present invention, when constructing a levee body comprising a water-blocking portion and an outer shell portion outside the water-blocking portion, the electrodes are arranged in a predetermined arrangement. An electrode embedding step of embedding a large number of the electrodes substantially along the outer periphery of a predetermined cross section of the water impervious portion, electrically connecting the electric prospecting device to the electrodes, and transmitting a current by an arbitrary current electrode among these electrodes. Measuring the potential difference between the other potential electrodes except for the current electrode, and a measuring step of outputting the measured value to the outside, and electrically and controllably connecting a computer to the electric exploration device, from the electric exploration device Analyzing the specific resistance structure of the predetermined cross section based on the input measurement values, creating a first specific resistance distribution from the specific resistance structure of the predetermined cross section, and creating the first specific resistance distribution Elapsed time from time After that, a specific resistance distribution creating step for sequentially creating a new specific resistance distribution, and comparing these specific resistance distributions different with time, change in the specific resistance distribution is monitored with time, and an abnormal specific resistance is detected in the specific resistance distribution. When a change is discovered,
And a detecting step of detecting an abnormal portion of the bank corresponding to the abnormal portion.

In the method for managing a fill dam according to the specific resistance tomography method according to the present invention, when the embankment including the water-blocking portion and the outer shell portion outside the water-blocking portion is constructed in the electrode burying step, the electrodes are set to a predetermined predetermined value. Many are buried along the outer periphery of a predetermined cross section of the water-blocking part based on the arrangement of the water-impervious portion, and the electric probe is electrically connected to the above-mentioned electrodes in the measuring step, and a current is transmitted by an arbitrary one of these electrodes. Then, the potential difference between the other potential electrodes except the current electrode is measured, the measured value is output to the outside, and a computer is electrically and controllably connected to the electric prospecting device by a resistivity distribution creating step, Analyzing the specific resistance structure of the predetermined cross section based on the measurement value input from the electric prospecting apparatus, creating a first specific resistance distribution from the specific resistance structure of the predetermined cross section, Specific resistance After a predetermined time elapses from the time of creation, a new resistivity distribution is sequentially created, and the resistivity distribution different over time is compared by the detection process, and the change of the resistivity distribution is monitored over time. When an unusual change in resistivity is found, an abnormal part of the embankment corresponding to the abnormal part is detected, so that the entire embankment can be accurately probed non-destructively without generating undetectable areas In addition, as long as the electrodes and electric wires function, the bank can be managed semipermanently.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a fill dam management system using a resistivity tomography method according to an embodiment of the present invention, and FIG. 2 is a flowchart thereof.
In the fill dam management system according to the above embodiment, at the planning stage of the construction of the embankment 3 (see FIG. 1), an electrode arrangement plan is created together with the material test of the embankment (see FIG. 2) (FIG. 2).
Step S1). At a predetermined experimental site, a relationship between specific resistance and temperature, a relationship between specific resistance and a gap ratio, a relationship between specific resistance and a degree of saturation for a water-blocking material of the water-blocking portion 4 (see FIG. 1) in advance by an experiment. (Step Sp in FIG. 2)
1, see FIGS. 5 and 6). Further, at the time of excavating the foundation of the embankment body 3, the specific resistance of the foundation ground is measured (see Step Sp2 in FIG. 2). Based on the relationship between the specific resistance obtained by these experiments and each physical property (temperature, gap ratio, saturation, etc.) (see FIGS. 5 and 6) and the specific resistance measurement of the foundation ground obtained by actual measurement. Then, in order to make the initial model by the specific resistance tomography method known, basic data for analysis / abnormality determination is acquired (see Step Sp3 in FIG. 2).

Further, as shown in FIG. 1, the fill dam management system according to the above-described embodiment includes an electric prospecting device 2,
Measurement electrodes Pa1 to Pan, Pb1 buried in the embankment (fill dam) 3 and electrically connected to the electric prospecting device 2
, Pbn, a temperature sensor 6 buried at a predetermined position in the water shielding section 4, a thermometer 7 electrically connected to the temperature sensor 6, and outputting temperature data from the temperature sensor 6 to the outside, and an electric probe 2 And a thermometer 7 for controlling the electric probe 2 and for analyzing and controlling the measurement results sent from the electric probe 2. As shown in FIG. 1, the embankment body 3 is formed with a water-blocking portion 4 and an outer shell 3 </ b> A into which rocks, earth and sand, etc. are charged, on the upstream and downstream sides of the water-blocking portion 4.

The measuring electrodes Pa1 to Pan, P
b1 to Pbn, as shown in FIG.
Installed in a predetermined direction of the water shielding portion 4 (in the present embodiment, two directions of the upstream and downstream directions A and the bank axis direction B),
After construction, it is composed of a corrosion-resistant metal piece that is embedded in the bank body 3. That is, based on a predetermined electrode arrangement plan (see step S1 in FIG. 2), after the foundation excavation of the embankment body 3 (see step S2 in FIG. 2), as shown in FIG. A predetermined electrode Pa1 is provided on the portion
Pa5, Pb1... Pb5 are installed (step S3 in FIG. 2).
2), the electrodes Pa1 to P1 are placed at predetermined positions where the electrodes Pa1 to P4 are set up while performing the filling (see step S4 in FIG. 2).
An, Pb1 to Pbn and the temperature sensor 6 are installed (see step S5 in FIG. 2) to form the impermeable portion 4 and the embankment 3
(See step S6 in FIG. 2). After the completion of the filling, a flooding test is performed as shown in FIG. 2, and the operation is started.

When the embankment 3 is constructed (step S in FIG. 2).
3 to S6), and a buried design device (not shown) such as a pore water pressure gauge is buried in a predetermined place. These embedded devices are used to measure pore water pressure, stress and deformation. In the analysis by resistivity tomography, the measured data of physical properties are output to the computer 5 and compared with the distribution of specific resistance at that time. Associate the data with the resistivity distribution,
These comparisons are repeated with time, and the function may be performed at least until a relationship between physical properties and specific resistance is derived. For this reason, after the relational expression is derived, even if a failure occurs, it does not have to be replaced. The saturation area of the water impervious part is estimated from the data of the pore water pressure gauge, and the change is correlated with the change of the resistivity distribution. The embedded design itself is not unique to the present invention, and is conventionally installed as a part of a dam as needed. However, what is relevant to the present invention is the distribution of the saturated portion, particularly by the pore pressure gauge. In other words, when the water column height is obtained from the pressure using the pore water pressure gauge buried in the dam, the infiltration line (boundary between the saturated part and the unsaturated part) can be drawn. A change in water pressure indicates a change in the infiltration line, indicating a change in the saturated portion. This is associated with a change in resistivity with respect to saturation. In addition, if there is an abnormality in the earth pressure gauge or the subsidence gauge, it can be used as a data for determining the abnormality in relation to the change in the specific resistance in the vicinity. that time,
Although the void ratio changes, the void ratio is not directly measured.

In this embodiment, each measuring electrode system Pa1
As shown in FIG. 1, Pan and Pb1 to Pbn are buried along the outer periphery of the water shield 4 in both the upstream and downstream directions A and the bank axis direction B. At the time of construction of the water shielding portion 4, the temperature sensor 6 is used for each measurement electrode system Pa1 to Pa
n, buried at a predetermined position on a plane formed by Pb1 to Pbn. The temperature sensor 6 is provided to eliminate the influence of temperature on the obtained specific resistance change, or to clarify the contribution of the temperature change to the specific resistance change. The temperature information is sent to the outside. Regarding the temperature sensor 6, the electric conductivity changes with the temperature, and the specific resistance, which is the reciprocal thereof, also changes with the temperature, as shown at 25 ° C. conversion. Since the temperature of the upper portion of the embankment changes, for example, the resistivity differs between day and night, and between summer and winter. The temperature sensor 6 is required in order not to mistake such a daily change or an annual change as a bank body abnormality.

As shown in FIG. 3, the electric prospecting apparatus 2 includes, for example, measurement electrodes P1 to Pn and a multi-core cable 21 electrically connected to each of the measurement electrodes P1 to Pn.
And a terminal plate 22 electrically connected to the multi-core cable.
And a transmitter 23 and a receiver 24 which are electrically connected to the terminal plate 22, are connected to the terminals, and repeat the measurement while moving each terminal. The electric prospecting device 2
Two electrodes (C1, C2) of the measurement electrodes P1 to Pn
2) is used as a current electrode, and another measurement electrode is used as a potential electrode as a potential measurement electrode. That is, for example, as illustrated in FIG. 1, the electric prospecting device 2 includes the electrodes Pa <b> 1 to Pan installed in the upstream / downstream direction A.
Of two current electrodes (transmitting electrodes) C1 and C2
(For example, C1 = Pa1, C2 = Pa14), and a current is transmitted between two potential electrodes (measurement electrodes) P1 and P2 other than the current electrode (for example, P1 = Pa2... Pan).
(Excluding Pa1), the potential difference of P2 = Pa2... Pan (excluding Pa14) was measured, and the measured value was measured by a computer 5.
To be sent. There are no fixed specifications for the measurement combinations, but it is desirable to transmit and receive as many combinations as possible, increase the number of data, and improve the analysis accuracy, but it is uneconomical to measure all possible combinations. However, only the necessary and sufficient points can be measured according to the site.

The computer 5 calculates a potential electrode (for example, a current electrode C1 = Pa) from the measured values of the plurality of combinations.
1, when C2 = Pa14, the specific resistance structure corresponding to the surface formed by Pa2 and Pan excluding these Pa1 and Pa14 (that is, the cross section of the bank 3) is analyzed. Further, when temperature information from the temperature sensor 6 is input to the computer 5 via the thermometer 7, the temperature distribution in the cross section of the water shielding portion 4 surrounded by the electrodes Pa1 to Pan can be monitored. That is, the computer 5 can estimate a change in the temperature distribution in the bank body 3 and a change in the water-containing state from the change in the measured value and the change in the specific resistance structure. That is, the input data is processed by the specific resistance tomography method, the first specific resistance structure serving as a reference is analyzed, and after a predetermined period or time elapses, the specific resistance structure analyzed and processed in the same manner is The change with time is grasped in comparison with that of the above, and the change in physical properties is estimated from the change in specific resistance.

Next, a fill dam management method using the resistivity tomography method based on the operation of the fill dam management system using the resistivity tomography method according to the present embodiment will be described. At the planning stage of the construction of the embankment body 3, as shown in FIG. 2, an electrode arrangement plan is created (see step S1 in FIG. 2), and at a predetermined experimental site, the relationship between the specific resistance and the temperature is determined in advance by experiments. , The relationship between the specific resistance and the gap ratio, the relationship between the specific resistance and the saturation, and the like are obtained (step Sp in FIG. 2).
1, see FIGS. 5 and 6). Further, at the time of excavation of the foundation of the embankment body 3, the specific resistance of the foundation ground is measured (see Step Sp2 in FIG. 2). Based on the relationship between the specific resistance obtained by these experiments and each physical property (temperature, gap ratio, saturation, etc.) (see FIGS. 5 and 6) and the specific resistance measurement of the foundation ground obtained by actual measurement. Then, in order to make the initial model by the specific resistance tomography method known, basic data for analysis / abnormality determination is acquired (see step Sp3 in FIG. 2).

When the embankment body 3 is constructed, the electrodes Pa1 to Pan, P
The b1 to Pbn are installed and buried in a predetermined arrangement in two directions of the upstream and downstream directions A and the bank axis direction B on substantially the entire outer peripheral surface (including the bottom part) of the water shielding portion 4 (burying step). For this reason,
The electrodes Pa1 to Pan, P
b1 to Pbn, for one of the electrode systems Pa or Pb, two selected current electrodes C1 and C2 (for both C1 and C2, the electrodes Pa1 to Pa2).
When a current is transmitted from a current electrode (a transmission electrode) arbitrarily selected from n, a potential difference between two potential electrodes other than these current electrodes is measured. This measurement is performed by a combination of a large number of electrodes (measurement step). That is, based on the specific resistance tomography method, a cross section surrounded by one electrode system Pa is divided into small regions as a search target region, and the potential difference for each of these small regions is measured by a combination of electrodes. I have. That is, regarding the electrode system Pa, a cross section in the upstream and downstream directions of the bank body 3 (FIG. 7)
(See the model divided into the respective regions) with the other electrode system Pb
Is measured by modeling the cross section of the bank body 3 in the bank axis direction.

In the fill dam management method based on the resistivity tomography method, when the embankment body 3 is constructed (see steps S3 to S6 in FIG. 2), a buried design device such as a temperature sensor 6 and a pore water pressure gauge is provided at a predetermined place. (Not shown). These embedding devices output measurement data of various physical properties. By the way, firstly, the function acting as a variable of the specific resistance change is temperature, and the temperature distribution monitor inside the embankment 3 obtained by the temperature sensor 6 embedded in the embankment 3 controls the specific resistance change. It is designed to eliminate the effects of temperature. Further, the data measured by the implanted device is output to the computer 5, and the computer 5 compares the data measured by the implanted device, such as a change in the infiltration line (change of the saturated portion), with a change in the specific resistance. ing.

The measured values of the electric probe 2 for each electrode combination are output to the computer 5. The computer 5 analyzes the specific resistance structure of the specific resistance block of the model (see FIG. 7) based on the measurement values input by the electric prospecting apparatus 2, and creates a first specific resistance distribution (step S7 in FIG. 2). reference). Next, this first
The measurement is repeated over time (see step S8 in FIG. 2) from the time of the first creation to sequentially create different resistivity distributions over time (resistivity distribution creation step). At the time of this time-dependent measurement, as shown in step Sp4 of FIG. 2, basic specifications of the analysis and abnormality determination obtained in advance by experiment (step Sp4 of FIG. 2)
3), the physical property data measured from the embedded design device is compared with the resistivity distribution, and these resistivity distributions different over time are compared to monitor the change of the resistivity distribution over time. When an abnormal change in specific resistance is found in the resistance distribution, an abnormal portion of the embankment corresponding to the abnormal portion is detected (detection process, see step S9 in FIG. 2).
Further, the normal value / abnormality judgment value is updated based on the data of the embedded design device obtained in step Sp4 of FIG. 2 (see step Sp5 of FIG. 2). Therefore, the accuracy of the normal / abnormal judgment is improved each time the measurement over time is repeated.

As described above, in the fill dam management system and the fill dam management method according to the above embodiment,
The relationship between specific resistance and each physical property (temperature, saturation, etc.) is obtained in advance through experiments to obtain the basic specifications for analysis / abnormality judgment, and to measure the pore water pressure, etc., of the embankment 3 during construction of the embankment 3 The instrument and temperature sensor 6 and the electrodes Pa and Pb for detecting the specific resistance are embedded in the embankment 3 in advance, and after the embankment 3 is completed, the physical properties collected from the embedding design device and the temperature sensor 6 embedded in the embankment 3 The data and the potential data measured by the electric prospecting apparatus 2 are processed by the computer 5 to create a physical property distribution (temperature distribution, saturation distribution, etc.) and a specific resistance distribution with time, and thereafter, these created. The physical property distribution and the resistivity distribution are compared based on a relational expression obtained in advance by an experiment, and based on the comparison, it is determined whether the change in the resistivity distribution is abnormal or normal. Detection of abnormal parts according to the area of resistivity distribution Going on. Further, the data obtained by this comparison can be accumulated while being updated as normal / abnormal judgment data.

Also, by making the initial model known based on the basic specifications of the analysis and abnormality determination obtained in advance by experiments, the accuracy of detecting an abnormality can be improved by performing an inverse analysis using this known information. I do. In this case, it is also possible to detect an abnormality by a change in the resistivity distribution regardless of the presence or absence of the physical property data detected from the embedded design device, but preferably, the resistivity distribution and the physical property distribution detected from the embedded design device are used. If an abnormality is detected by comparing, the accuracy is further improved.

The relationship between the specific resistance and each physical property (moisture content, temperature) shown in FIGS. 5 and 6 is obtained in advance in a laboratory experiment, and each physical property that can be a variable of the specific resistance function is as follows.
The temperature in the embankment, the degree of saturation of the impermeable material, the porosity of at least one of the impermeable material and the foundation ground, the electrical conductivity of interstitial water, and the like. The electric conductivity is a variable of temperature. The temperature sensor 6 is required as long as data can be collected in order to remove the influence of the temperature change from the specific resistance change in the bank body 3. Furthermore, although the temperature sensor 6 is for two-dimensional temperature correction, an abnormality at that point may be known from the temperature change itself. Monitor by resistivity
It is used after the direct sensors (buried design device) for directly detecting the physical properties of the embankment body 3 are stopped, and the sensors are prioritized as monitoring items while measurement by a pore water pressure gauge or the like is possible. The pore pressure gauge as a type of the buried design device is not shown because it is used as a general buried design device.

In the specific resistance tomography method, an actual measurement value is obtained by combining a large number of electrodes, the area to be searched is divided into small areas, and the specific resistance distribution model is changed by changing the specific resistance of each small area. This is a method in which the measured value calculated from the model is corrected and the measured value is compared with the actual measured value, and a model that minimizes the sum of squares of the difference is obtained. Comparing the analysis results for two periods, if a comparative resistance change portion is found, a change in the physical properties represented by the following equation (Archie, 1942) is estimated in that portion.

[0026]

(Equation 1)

Where the saturation S is

[0028]

(Equation 2)

Thus, an exponential relationship is established between the water content and the specific resistance of the soil.

FIG. 5 is a diagram showing a change in specific resistance when the moisture content is changed using weathered mudstone used as a water-blocking material as a sample, and is data obtained in advance by an indoor test (Equation 3). (See step Sp1 in FIG. 2).

[0031]

(Equation 3)

Further, since the specific resistance of pore water changes with temperature, the specific resistance is a function of temperature. FIG. 6 is a diagram showing a change in specific resistance when the temperature is changed using cohesive soil as a sample, and is data obtained in advance by an indoor test (see step Sp1 in FIG. 2).

On the other hand, the abnormality related to the fill dam
Is a phenomenon. One is the change of the infiltration line due to the change of the water-containing state inside the water-blocking part 4, which is indicated from the measurement data of the buried pore pressure gauge. This is the formation of a water leakage path in the foundation ground around the part 4. Physically, the former is regarded as a change in the degree of saturation of the impermeable material, and the latter is regarded as a change in the porosity of the impermeable material or the foundation ground, and a change in the temperature and electric conductivity of the interstitial water. These physical properties are variables of the specific resistance function as described above, and a specific resistance tomography method using an electrode system buried in the vicinity of the impermeable portion 4 at the time of embankment is performed with time, and the change in specific resistance distribution is observed. By monitoring, it is possible to detect an abnormality of the impermeable portion 4 of the embankment body 3 in a long term. At the same time, by monitoring the temperature distribution inside the embankment body 3, the contribution of the temperature change to the specific resistance change can be clarified. In the specific resistance tomography method, since the specific resistance distribution in a portion outside the region surrounded by the electrode system can also be analyzed, an abnormality can be detected even in the foundation ground in contact with the embankment.

[0034]

Next, an example in which an experiment was conducted using the fill dam management system based on the resistivity tomography method according to the above configuration will be described. In the experiment, we modeled the cross section in the upstream and downstream direction of the embankment, and performed a numerical experiment on the specific resistance change when the impermeable part changed. The model simplifies the fill dam,
As shown in FIG. 7, the central water-impervious portion is 30 Ωm, and the downstream lock member (outer shell) and the space are 999,999 Ω.
m, the saturated rock material and water storage on the upstream side were set to 50Ωm, and the foundation ground was set to 300Ωm. The calculation area used for the numerical modeling and the inverse analysis by the difference method was set to a range of 59 × 50 mesh, and the analysis area of the inverse analysis was set to a range of 20 × 21 blocks in units of a 2 × 2 mesh specific resistance block ( (See FIG. 7). The electrode spacing was 2 mesh, and 64 points were arranged on the outer periphery of the water-blocking portion. The measurement electrode arrangement is a two-pole method, and the total number of measurement points is 2016.

With respect to the above model, a specific resistance change according to the case was given to the specific resistance block of the initial model, and numerical modeling by the difference method was performed on the specific model to calculate measured values. The measured value was subjected to an inverse analysis by the least squares method with a smoothing constraint, and the results of 10 repeated calculations were displayed as the analysis results.

FIG. 8 shows the results of analysis on the calculated and measured values obtained from the initial model of FIG. 7, with the resistivity structure unknown and the initial value of the block resistivity being 100 Ωm uniform. A resistivity value close to that of the initial model has been analyzed, indicating that a resistivity structure outside the range surrounded by the electrode system is also required.

FIG. 9 shows the specific resistance structure according to the initial model given as the initial value of the block specific resistance using the same measured values as those in FIG. It can be seen that the analysis accuracy is improved by knowing the specific resistance structure.

FIGS. 10 and 11 show the results of the same analysis as in FIGS. 8 and 9, respectively, in the case where the electrode cannot be installed on the bottom surface of the water impervious portion. In this case, there are 53 electrodes and 1,378 calculated measurements. FIG. 10 and FIG.
No. 1 shows a large difference between the model and the results of analysis of the water impermeable portion and the foundation ground near the bottom surface without electrodes, indicating the necessity of electrode installation on the bottom surface.

FIG. 12 shows that a water leaking part occurs in a part of the embankment of the embankment, and the part is changed from 30 Ωm to 20 Ωm due to an increase in porosity.
It is the result of analyzing the calculated measurement values obtained from the model, assuming the case of changing to Ωm. The change situation is well analyzed.

FIG. 13 shows the result of analyzing the calculated measurement values obtained from the model, assuming a case where a water leakage point occurs on the embankment foundation and the portion changes from 300 Ωm to 150 Ωm due to an increase in the porosity. is there. Changes in the outside of the electrode system are well analyzed.

FIG. 14 shows the case where the infiltration line changes at the upper part of the embankment body and the part changes from 30 Ωm to 50 Ωm due to the increase of the unsaturated part, and the calculated measurement values obtained from the model are analyzed. It is a result. For this as well, the change situation is well analyzed.

From the above results, in the fill dam management system using the resistivity tomography method according to the present embodiment,
It is possible to monitor the change in the specific resistance generated in the water shielding portion 4 of the embankment body 3, and it is possible to estimate the occurrence of the abnormality and its location. In this system, it is possible to identify a change in physical properties that causes a change in resistivity while various types of embedded devices are operating, and accumulate examples of evaluation of changes in specific resistance after failure of the embedded device. Further, in this fill dam management system, it is possible to monitor a wider range by providing electrodes in a borehole or the like.

In the above embodiments and examples, two predetermined measuring potential electrodes among the buried measuring potential electrodes are used as current electrodes. However, the present invention is not limited to this. As shown in FIG. 4, far electrodes C31 and C3 are used for transmission and reception according to the electrode arrangements P31 to P3n employed.
2 and embedded potential electrode P for measurement
One of 31-P3n may be used for transmission and reception. Reference numerals 22, 23, and 24 denote terminal boards, transmitters, respectively.
It is a receiver. Further, the electrodes are buried in the bank axis direction and the upstream / downstream direction of the impermeable portion, but the present invention is not limited to this, and the electrode of the present invention may be applied in either the bank axis direction or the upstream / downstream direction. Can achieve the purpose. Also,
It goes without saying that the arrangement may be appropriately changed according to the embankment body. Furthermore, in the fill dam management system and the fill dam management method according to the above-described embodiment, data is collected by the embedded design device and the temperature sensor.
The present invention is not limited to this, and even if there is no embedded design device, the object of the present invention can be achieved with a temperature sensor.

[0044]

As described above, in the fill dam management system according to the resistivity tomography method of the present invention, when the embankment composed of the water-blocking portion and the outer shell upstream and downstream of the water-blocking portion is determined in advance, Based on the predetermined arrangement, a large number of electrodes buried along substantially the outer periphery of a predetermined cross section of the water shielding portion, and the electrodes are electrically connected to each other, and a current is transmitted by an arbitrary current electrode among these electrodes. An electric probe that measures a potential difference between the other potential electrodes except the current electrode, and outputs the measured value to the outside, and is electrically connected to the electric probe, controls the electric probe, and controls the electric probe. A computer for analyzing a specific resistance structure of a predetermined cross section based on a measurement value input from the device, and generating a first specific resistance distribution from the specific resistance structure of the predetermined cross section; Predetermined time from creation After that, a new resistivity distribution is created in sequence, and these resistivity distributions that differ over time are compared to monitor changes in the resistivity distribution over time, and when an abnormal resistivity change is found in the resistivity distribution. Detects an abnormal part of the embankment corresponding to the abnormal part, so that the abnormal part can be detected accurately by non-destructive exploration, and the measuring equipment is simplified and precise management over a long period of time Therefore, the cost of dam management can be reduced. In addition, measurement over a longer period of time can be performed as compared with a conventional embedded design device. For this reason, long-term safety management of dams can be performed, and an accurate investigation plan can be set for abnormal situations and countermeasures can be taken. Furthermore, it can be expected to be applied to the evaluation of repair and renewal time due to aging of facilities.

In the method for managing a fill dam according to the resistivity tomography method of the present invention, the electrodes are arranged in a predetermined arrangement at the time of constructing the embankment composed of the impermeable portion and the outer shell portion outside the impermeable portion. An electrode embedding step of embedding a large number along the substantially outer periphery of the predetermined cross section of the water impervious part based on, and electrically connecting the electric prospecting device to the electrodes, transmitting a current by an arbitrary current electrode among these electrodes, A measuring step of measuring a potential difference between the other potential electrodes except the current electrode and outputting the measured value to the outside, and electrically and controllably connecting a computer to the electric prospecting device, and inputting from the electric prospecting device. Analyzing the specific resistance structure of the predetermined cross section based on the measured value, creating a first specific resistance distribution from the specific resistance structure of the predetermined cross section, and creating the first specific resistance distribution. After a predetermined time from A specific resistance distribution creation step for sequentially creating a specific resistance distribution, and monitoring the change of the specific resistance distribution over time by comparing the different specific resistance distributions with time. And a detection step for detecting an abnormal portion of the embankment corresponding to the abnormal portion when the is found, so that the entire embankment can be accurately and nondestructively searched without generating an unsearchable area. At the same time, as long as the electrodes function, the bank can be managed semipermanently, so that the management cost can be reduced and the management can be performed for a long period of time.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a fill dam management system using a resistivity tomography method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing steps of a fill dam management method using a resistivity tomography method according to one embodiment of the present invention.

FIG. 3 is a conceptual diagram schematically showing an electric prospecting apparatus used for the resistivity tomography method of FIG.

FIG. 4 is a conceptual diagram showing a modified example of the electric prospecting apparatus of FIG. 3;

FIG. 5 is a graph showing a relationship between a water content ratio and a specific resistance obtained in an experiment in advance.

FIG. 6 is a graph showing a relationship between a temperature and a specific resistance obtained in advance by an experiment.

FIG. 7 is an explanatory diagram showing a calculation region of 59 × 50 mesh in a thin line region and a calculation region of 20 × 21 blocks in an analysis region, an analysis region, and an initial model in a thick line region.

FIG. 8 is a graph showing an analysis result of a calculated measurement value obtained from the initial model of FIG. 7;

FIG. 9 is a graph showing an analysis result in which a specific resistance structure according to an initial model is given as an initial value of block specific resistance using the same calculated measurement values as in FIG. 8;

FIG. 10 is a graph showing an analysis result similar to that of FIG. 8 in a case where an electrode cannot be installed on the bottom surface of the water shielding portion.

FIG. 11 is a graph showing the same analysis result as that of FIG. 9 in a case where an electrode cannot be installed on the bottom surface of the water shielding portion.

FIG. 12 is a graph showing an analysis result of a calculated measurement value obtained from a model in a case where a water leakage point occurs in the water-impedance portion of the embankment body.

FIG. 13 is a graph showing an analysis result of a calculated measurement value obtained from a model in a case where a leakage point occurs in a bank body foundation.

FIG. 14 is an analysis result of a calculated measurement value obtained from a model in a case where an infiltration line changes in an upper part of an embankment and an unsaturated portion is generated.

[Explanation of symbols]

 2 Electric exploration device 3 Fill dam (bank body) 3A outer shell 4 Water barrier 5 Computer Pa1-Pan, Pb1-Pbn Measurement electrodes (electrodes) C1, C2 Transmission electrodes (current electrodes)

Claims (10)

[Claims] At the time of constructing a levee body composed of a water-blocking portion and an outer shell on the upstream and downstream of the water-blocking portion, the embankment extends along substantially the outer periphery of a predetermined cross section of the water-blocking portion based on a predetermined arrangement. A large number of buried electrodes and the electrodes are electrically connected to each other, a current is transmitted from any of these electrodes, and a potential difference between the potential electrodes other than the current electrodes is measured. And an electrical probe that outputs the data to the outside, and is electrically connected to the electrical probe, controls the electrical probe, and analyzes the specific resistance structure of a predetermined cross section based on the measurement values input from the electrical probe. A first specific resistance distribution is created from the specific resistance structure having the predetermined cross section, and a new specific resistance distribution is sequentially created after a lapse of a predetermined time from the time of the first generation. Specific resistance distributions Monitor changes in distribution over time,
A fill dam management system using a resistivity tomography method, which detects an abnormal portion of a bank body corresponding to an abnormal portion when an abnormal change in the specific resistance is found in the specific resistance distribution. 2. When the embankment is built, the embankment is buried in the embankment based on a predetermined arrangement, and has a buried design device for measuring physical properties and outputting the measured data to the outside. 2. The fill dam management system according to claim 1, wherein the abnormality in the embankment is analyzed by comparing the change in the specific resistance and the measurement data output from the embedded design device. 3. A relationship between the specific resistance and the physical properties of the water-blocking material of the water-blocking portion is derived in advance, and based on the specific resistance-physical relationship, basic data for determining an abnormality at the time of analysis is obtained. 3. The fill dam management system based on the resistivity tomography method according to claim 1 or 2, wherein the inverse analysis is performed by using. 4. The monitoring system according to claim 1, wherein a normal value is updated based on a value when no abnormality is detected in the embankment, and an abnormality determination value is updated based on a value when abnormality is detected. A fill dam management system based on the resistivity tomography method according to any one of the above. 5. The fill dam management system according to claim 1, wherein the electrode is buried in at least one of the bank axis direction and the upstream / downstream direction of the impermeable portion. 6. The embedding design device according to claim 2, wherein the temperature sensor and a thermometer electrically connected to the temperature sensor and outputting temperature information of a predetermined surface of the embankment to the outside. Fill dam management system by resistivity tomography. 7. When constructing a levee body comprising a water-blocking portion and an outer shell portion outside the water-blocking portion, the electrodes are arranged along substantially the outer periphery of a predetermined cross section of the water-blocking portion based on a predetermined layout. An electrode embedding step of burying a large number of electrodes, electrically connecting an electric probe to the above electrodes, transmitting a current through any of these electrodes, and measuring a potential difference between the other potential electrodes except the above current electrodes A measuring step of outputting the measured value to the outside, and a computer electrically and controllably connected to the electric prospecting device, and based on the measured value input from the electric prospecting device, the specific resistance of the predetermined cross section. The structure is analyzed, a first specific resistance distribution is created from the specific resistance structure of the predetermined cross section, and a new specific resistance distribution is sequentially created after a lapse of a predetermined time from the creation of the first specific resistance distribution. The process of creating the resistivity distribution The change of the resistivity distribution is monitored over time by comparing the different resistivity distributions, and when an abnormal resistivity change is found in the resistivity distribution, the abnormal portion of the embankment corresponding to the abnormal portion is detected. A fill dam management method by resistivity tomography, comprising: a detection step. 8. When the embankment is constructed, an embedding device that measures physical properties based on a predetermined arrangement and outputs it to the outside is buried in the embankment, and the ratio is analyzed by a measured value of an electric prospecting device. The method according to claim 7, wherein the abnormality in the embankment is analyzed by comparing the resistance change with the measurement data output from the embedded design device. 9. A relationship between specific resistance and physical properties of a water-blocking material of a water-blocking portion is derived in advance, and based on the specific resistance-physical properties relationship, basic data for abnormality determination at the time of analysis is obtained. The method according to claim 7 or 8, wherein the inverse analysis is performed by using a method. 10. The monitoring device according to claim 7, wherein a normal value is updated based on a value when no abnormality is detected in the embankment, and an abnormality determination value is updated based on a value when abnormality is detected. The fill dam management method according to the specific resistance tomography method according to any one of the above.