CN115201928A - A time-shift resistivity anomaly extraction method - Google Patents

Abstract

The invention discloses a time-shifting resistivity anomaly extraction method. The calculation method is characterized in that the resistivity break variable can be quickly obtained by analyzing the measured resistivity data of the previous and subsequent time periods and quickly calculating the difference between the resistivity theoretical data of a certain time period and the resistivity data of the corresponding time period to perform comparative analysis.

Description

A time-shift resistivity anomaly extraction method

technical field

The invention belongs to the field of geophysical exploration, and in particular relates to a method for extracting time-shifted resistivity anomalies. Specifically, a special method is used to quickly calculate the theoretical resistivity value of a certain time period, and then the theoretical value and the actual observed value are calculated. Comparative analysis, so as to quickly and accurately obtain the resistivity mutation position and mutation amount.

Background technique

The time-shift resistivity method is currently widely used in dam leakage monitoring. Many domestic units have carried out a lot of research on time-shift electrical monitoring technology for dams. The 3D high-density electrical method is used to detect the contact leakage of dams and culverts. Li Wenzhong and Sun Weimin of Changjiang Survey, Planning, Design and Research Co., Ltd. have carried out research on the time-shift detection of dikes. At present, most of the time-shifted resistivity data processing methods use multiple inversion methods to calculate the resistivity model results of multiple time segments, and then extract the model resistivity change rate processing method. Discrete in the space-time domain, and use the time parameter as one of the variables for full 4D inversion; or invert and iterate the data sets and model parameters at multiple different time points at the same time. At present, most of these time-shift electrical data inversion processing methods are used. In the research stage, the calculation efficiency is relatively low, and it has not been popularized and applied in the monitoring data processing of the dyke time-shift method.

The time-lapse resistivity data forward and inversion work is also based on the conventional 2D/3D resistivity forward and inversion algorithm. The core is to compare and analyze the differences and changes of the observed data at different times, and forward the calculation to calculate the differences in the electrical parameters of the corresponding underground electrical structure models. , the computational model shows the real changes in the subsurface medium over time. Because the time-lapse resistivity forward and inversion work is time-consuming and consumes a lot of computing power, and the electrical anomalies inside the dam cannot be analyzed in time, it cannot support the flood season command work in time. Therefore, a fast calculation method for the extraction of time-shift resistivity anomalies is proposed. .

SUMMARY OF THE INVENTION

In order to solve the problem of rapid localization of prominent changes in resistivity in river embankment leakage monitoring during flood season, the present invention provides a time-shifted resistivity anomaly extraction method. This method mainly calculates the theoretical resistivity value based on the relative stability coefficient of the resistivity change rate of adjacent time segments, and displays the resistivity anomaly of a certain time segment in time through the calculated change amount, and at the same time provides positive and negative results for the future fast time series. Acting work provides background models. The principle of the method is simple and reliable, the calculation results are easy to identify, and it is easy to popularize.

The technical scheme adopted in the present invention is as follows:

A method for extracting abnormal time-shifted resistivity, which is used for rapidly extracting resistivity mutation amount and mutation position in resistivity monitoring work, characterized in that the method comprises the following steps:

Step 1): obtain the observed resistivity data of multiple time periods;

Step 2): Calculate the theoretical resistivity values of different time periods according to the observed resistivity data;

Step 3): Calculate the resistivity change amount according to the theoretical resistivity value and the observed resistivity data, delineate the resistivity mutation amount according to the threshold value designed by experience, and locate the spatial position of the resistivity mutation at the same time.

Further, in step 2), the theoretical resistivity value is calculated according to formulas (1)-(3); wherein, the formulas (1)-(3) are expressed as follows:

为T时间段观测电阻率数据，k为常系数，

为T时间段理论电阻率值，x、y、z为与电阻率对应的空间位置参数，T-1,T或T+1为时间段信息。in,

is the observed resistivity data in the T time period, k is a constant coefficient,

is the theoretical resistivity value in the T time period, x, y, and z are the spatial position parameters corresponding to the resistivity, and T-1, T or T+1 is the time period information.

Further, in step 3), the resistivity variation is calculated according to formula (4); wherein, the formula (4) is expressed as follows:

为T时间段异常电阻率偏离度。in,

is the deviation of abnormal resistivity in the T time period.

The present invention can achieve the following beneficial effects:

The invention analyzes the measured resistivity data before and after the time period, and quickly calculates the difference between the resistivity theoretical data of a certain time period and the actual measured resistivity data of the corresponding time period, and can quickly obtain the resistivity mutation value. The data is synchronized with spatial position information, so the corresponding mutation position can be obtained at the same time when the resistivity mutation value is obtained, which provides a reference for the time-shifted resistivity early warning work. .

Description of drawings

Figure 1 shows the layout of the time-shift resistivity observation system for the dam.

Fig. 2 is the calculated resistivity mutation value and position distribution diagram, wherein, the calculated change amount of more than 5% is selected as the resistivity mutation region.

Detailed ways

The specific embodiments of the present invention will be further explained below in conjunction with the accompanying drawings. Note that the following description is not a limitation of the present invention, but an explanation of the spirit and principle of the present invention.

The present invention relates to a method for extracting abnormal time-shift resistivity, which is used for rapidly extracting resistivity mutation amount and mutation position in time-shift resistivity monitoring work, and comprises the following steps:

Step 1): obtain the observed resistivity data of multiple time periods; the resistivity information of multiple different time periods is shown in Table 1;

Table 1

Step 2): calculate the theoretical resistivity values of different time periods in the later stage according to the observed resistivity data; see Table 2 for the calculated theoretical resistivity values of different time periods in the later stage;

Table 2

Step 3): Calculate the resistivity variation according to the theoretical resistivity value and the actual resistance value, so as to quickly obtain the magnitude of the variation and the corresponding spatial position of the resistivity mutation.

Further, in step 2), the theoretical resistivity value is calculated according to formulas (1)-(3); wherein, the formulas (1)-(3) are expressed as follows:

为T时间段观测电阻率数据，k为常系数，

为T时间段理论电阻率值，x、y、z为相对应的电阻率空间位置参数，T-1,T,T+1为时间段信息。in,

is the observed resistivity data in the T time period, k is a constant coefficient,

is the theoretical resistivity value in the T time period, x, y, and z are the corresponding resistivity spatial position parameters, and T-1, T, T+1 are the time period information.

Further, in step 3), the resistivity variation is calculated according to formula (4), as shown in Table 3; wherein, the formula (4) is expressed as follows:

为T时间段异常电阻率偏离度。in,

is the deviation of abnormal resistivity in the T time period.

table 3

Further, in step 3), it also includes marking the value and the spatial position of the resistivity change with a large amount, as shown in Table 4, which is convenient for on-site personnel to locate and check.

Table 4

Example 1:

The time-lapse resistivity observation of a dam is carried out in a certain reservoir dam. Figure 1 is a schematic diagram of the layout of the observation system. As shown in Figure 1, an electrical monitoring line is arranged on the backwater slope of a certain dam, which can monitor the backwater in real time. The resistivity change under the slope can be judged by the resistivity change, and the seepage law of the dam can be judged, and the time-lapse resistivity monitoring work can be carried out;

In this embodiment, the method for extracting abnormal time-shift resistivity includes the following steps:

(1) Obtain the resistivity information of different time periods measured on site, and the resistivity information of different time periods is shown in Table 5;

table 5

(2) Calculate the resistivity data of the corresponding time period according to the resistivity information of different time periods, the specific data are shown in Table 6 below;

Table 6

(3) Use formula 4 to calculate and compare the difference between the resistivity in the theoretical calculation period and the measured resistivity, and mark the value and spatial position of the resistivity change with a large amount. The specific data are shown in Table 7 below. Here, the resistivity A change of 5% is used as the threshold value of the resistivity mutation, and the resistivity value of the resistivity change exceeding 5% is regarded as a value with a large change;

Table 7

As shown in Figure 2, the left picture is the monitored time-shift resistivity data, and the right picture is the extracted resistivity change data. According to the field experience, the design change is 5% as the threshold, and more than 5% is the resistivity mutation The value of the normal resistivity is below 5%. Through comparison, it is found that the range of the resistivity change is all within 5%, indicating that the internal resistivity of the dam in this area is stable, the dam body is stable, there is no abnormal change, and there is no hidden leakage.

The parts of the present invention that are not described in detail belong to the well-known techniques in the art. The above-mentioned embodiments are only to describe the preferred embodiments of the present invention, and the preferred embodiments do not describe all the details in detail, nor do they limit the present invention to only the described specific embodiments. On the premise of not departing from the design spirit of the present invention, various modifications and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims (3)

1. a time-shifted resistivity abnormal extraction method, the method is used for rapidly extracting resistivity mutation and mutation position in resistivity monitoring work, it is characterized in that, described method comprises the following steps: Step 1): obtain the observed resistivity data of multiple time periods; Step 2): Calculate the theoretical resistivity values of different time periods according to the observed resistivity data; Step 3): Calculate the resistivity change amount according to the theoretical resistivity value and the observed resistivity data, delineate the resistivity mutation amount according to the threshold value designed by experience, and locate the spatial position of the resistivity mutation at the same time. 2. a kind of time-shifted resistivity abnormal extraction method according to claim 1, is characterized in that, In step 2), the theoretical resistivity value is calculated according to formulas (1)-(3); wherein, the formulas (1)-(3) are expressed as follows:

in,

is the observed resistivity data in the T time period, k is a constant coefficient,

is the theoretical resistivity value in the T time period, x, y, and z are the spatial position parameters corresponding to the resistivity, and T-1, T or T+1 is the time period information. 3. a kind of time-shifted resistivity abnormal extraction method according to claim 2, is characterized in that, In step 3), the resistivity variation is calculated according to formula (4); wherein, the formula (4) is expressed as follows:

in,

is the deviation of abnormal resistivity in the T time period.

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