CN112540410A - Reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method - Google Patents

Reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method Download PDF

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CN112540410A
CN112540410A CN202011398401.9A CN202011398401A CN112540410A CN 112540410 A CN112540410 A CN 112540410A CN 202011398401 A CN202011398401 A CN 202011398401A CN 112540410 A CN112540410 A CN 112540410A
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dam
transient electromagnetic
parallel electrical
electrical method
measuring
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谭磊
江晓益
李红文
俞炯奇
陈星�
许小杰
江树海
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Zhejiang Institute of Hydraulics and Estuary
Zhejiang Guangchuan Engineering Consulting Co Ltd
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Zhejiang Institute of Hydraulics and Estuary
Zhejiang Guangchuan Engineering Consulting Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/083—Controlled source electromagnetic [CSEM] surveying
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation

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Abstract

The invention discloses a reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method, comprising a longitudinal detection system, wherein the longitudinal detection system comprises a parallel electrical method detection device and a transient electromagnetic detection device, the parallel electrical method detection device comprises a parallel electrical method measuring line and a parallel electrical method instrument which are arranged on a central axis or an anti-seepage end surface at the top of a dam, and the parallel electrical method measuring line comprises copper bars which are adjacently inserted on the dam at intervals and cables connected with the copper bars; the transient electromagnetic detection device comprises a transient electromagnetic measuring line and a transient electromagnetic instrument which are arranged on a dam crest central axis or an impervious section of two dam shoulders of a dam and/or a dam crest hardening area, wherein the transient electromagnetic measuring line comprises a coil arranged on a measuring point and a coil cable connected with the coil; the cable and the coil cable are respectively connected with a parallel electrical method instrument and a transient electromagnetic instrument; the parallel electrical method instrument and the transient electromagnetic instrument are used for connecting with an analysis system.

Description

Reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method
Technical Field
The invention relates to the technical field of hydraulic engineering safety diagnosis, in particular to a reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method.
Background
The investigation and prevention and control of the leakage problem of the reservoir dam are difficult points of the standardized management of the hydraulic engineering, and the short board for supplementing the hidden danger of the engineering has important significance for ensuring the smooth infrastructure and the sustainable development of water efficiency. The earth and rockfill dam is an earth and rockfill granular structure formed by manual or mechanical layered rolling and stacking, seepage problems occur in multiple stages of construction, operation, maintenance and the like of a reservoir, in the process of continuously solving abnormal seepage risks of engineering series, researchers obtain certain achievements in the aspects of understanding of earth and rockfill dam seepage mechanisms, seepage safety evaluation, searching of seepage hidden dangers, safety improvement and the like, and particularly, scientific basis is provided for realizing accurate locking of target seepage areas along with the rapid development of high-efficiency, convenient and perspective nondestructive diagnosis technology. For example: the utility model CN 205538138U authorizes the detection device for detecting and directionally processing the hidden trouble of earth and rockfill dam leakage, and realizes the integration of leakage detection and processing of hidden trouble by introducing the parallel electrical detection technology to the earth and rockfill dam leakage detection and reasonably implementing grouting according to the detection result, thereby achieving the purpose of rapid directional processing; the invention patent CN 110082393A discloses a dam real-time monitoring system and a method based on mobile communication and high-density electrical method, which can perform real-time monitoring and early warning on the dam leakage condition, is easy to implement, completes the manual analysis process of data results by a computer, and simultaneously excavates data and provides richer conclusions. However, reservoir leakage is a result of continuous deterioration and accumulation of abnormal seepage in a dam, has the characteristics of unknown etiology, unknown focus and various diseases, and is represented by the fact that space position information is complex and changeable and a plurality of hidden patients are in cross coupling, so that the problem of misjudgment and misjudgment in the process of identifying hidden dangers by a single geophysical prospecting means is caused.
The invention patent CN 109782357A discloses a method for detecting dam leakage by combining a ground magnetic resonance method and a high-density electrical method, which utilizes an MRS method to accurately detect the leakage hidden trouble attribute of a low-resistance abnormal area disclosed by the high-density electrical method, and effectively improves the detection signal-to-noise ratio by optimizing the number of turns of a coil so as to improve the diagnosis efficiency and the accuracy of inversion result interpretation; the invention patent CN 111381276A discloses a monitoring method for dam leakage damage occurrence development and positioning, which utilizes common points and respective advantages of micro-motion and micro-vibration monitoring technologies to provide accurate time for occurrence of seepage damage and position of seepage damage, win time for treatment of hidden danger and greatly improve the working effect of treatment of hidden danger. However, the current detection methods for the hidden troubles of the hydraulic engineering have the characteristics of multiple types, different application conditions and the like, and most of the detection methods do not adopt a comprehensive geophysical prospecting method in a practical way, so that the waste of resources and the reduction of efficiency are caused to a certain extent, and how to adopt the optimal matching combination to realize the efficient, accurate and economic full perspective detection of the hidden troubles of the reservoir dam becomes a key. The leakage of the reservoir dam occurs in the area below the infiltration line, the most obvious physical property difference between the seepage weak area and the surrounding medium is mainly represented by the high and low resistivity, and therefore the electrical method technology plays an important role in diagnosing the leakage hidden danger. The high-density electrical method is generally applied to reservoir dams, but the field working efficiency is low, and the problems of hardening of the surface layer of the dam and blind areas at two ends of a measuring line are more prominent; the transient electromagnetic technology can adopt a non-contact coil to transmit and receive signals, has a good application prospect in leakage hidden danger detection in a complex field, but the size of the conventional transient electromagnetic detection equipment is large, and the shallow surface layer of a detection area has a blind area due to the turn-off time of an instrument and the interference of a primary field signal. Therefore, according to the characteristics of the reservoir dam in the geological, construction and operation processes, the advanced technology and the corresponding combined technology are adopted in sequence, so that the diagnosis reliability is improved, and the harrowing area is improved for the precise treatment of the reservoir dam.
Disclosure of Invention
The invention aims to solve the problems of single means or combined underoptimization and the like in reservoir dam leakage detection by a geophysical exploration method, and provides a reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method. The invention has the characteristics of high leakage channel resolution, quick field detection effect and complementary advantages of detection precision of different parts of the dam, and changes the detection arrangement system and the detection sequence according to field conditions in the use process, thereby improving the precision and the reliability of leakage diagnosis of the reservoir dam and realizing high-efficiency detection of the whole dam without blind areas.
A reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system comprises a longitudinal detection system, wherein the longitudinal detection system comprises a parallel electrical method detection device and a transient electromagnetic detection device, the parallel electrical method detection device comprises a parallel electrical method measuring line and a parallel electrical method instrument which are arranged on a central axis or an anti-seepage end surface at the top of a dam, and the parallel electrical method measuring line comprises copper bars which are adjacently inserted on the dam at intervals and cables connected with the copper bars; the transient electromagnetic detection device comprises a transient electromagnetic measuring line and a transient electromagnetic instrument which are arranged on a dam crest central axis or an impervious section of two dam shoulders of a dam and/or a dam crest hardening area, wherein the transient electromagnetic measuring line comprises a coil arranged on a measuring point and a coil cable connected with the coil; the cable and the coil cable are respectively connected with a parallel electrical method instrument and a transient electromagnetic instrument; the parallel electrical method instrument and the transient electromagnetic instrument are used for connecting with an analysis system.
Preferably, after the copper rod is inserted into the dam, a funnel-shaped pit is dug in the range of the radius of 10cm with the copper rod as the center, and the pit is filled with brine.
Preferably, the coils are placed horizontally on the surface of the dam and the coil normal is vertically downward. Preferably, the parallel electrical method instrument is provided with a wireless transmission module, a control module and an acquisition module, wherein the acquisition module is connected with a cable, the control module is used for issuing an acquisition instruction and a data recovery instruction to the acquisition module, and the wireless transmission module is used for remotely transmitting the data recovered by the control module to the analysis system; the analysis system has the dual functions of processing parallel electrical data and transient electromagnetic data, issues a transient electromagnetic data recovery instruction to the transient electromagnetic instrument, and remotely transmits data recovered in the transient electromagnetic instrument to the analysis system through the wireless transmission module.
Preferably, when the measuring lines are laid on site, the dam crest measuring lines, the first-level backwater slope measuring lines, the second-level backwater slope measuring lines, the third-level backwater slope measuring lines and the n-level backwater slope measuring lines are sequentially laid along the transverse width direction from the dam crest to the dam foot of the dam, and the distance between every two adjacent measuring lines is 5 m; the measuring line of the backwater slope of the next stage is determined by the range of the abnormal detection region of the previous stage.
Preferably, parallel electrical method measuring lines are arranged on a central axis or an impermeable section of the top of the dam, transient electromagnetic measuring lines are arranged on the two dams, the first-level back slope measuring line position is divided into a normal region and an abnormal region according to the dam top parallel electrical method and the transient electromagnetic detection result by combining the space position of the leakage point of the dam, the parallel electrical method measuring lines are arranged on the abnormal region of the first-level back slope measuring line, and the transient electromagnetic measuring lines are additionally arranged on the two dams; combining the spatial position of a leakage point of the dam, dividing the position of a second-level back slope measuring line into a normal area and an abnormal area according to the result of the parallel electrical method and the transient electromagnetic detection of the first-level back slope measuring line of the dam, arranging the parallel electrical method measuring line on the position of the abnormal area of the second-level back slope measuring line, and additionally arranging the transient electromagnetic measuring line on two dam shoulders; dividing the position of the three-level back water slope measuring line into a normal area and an abnormal area according to the parallel electrical method of the two-level back water slope measuring line of the dam and the result of transient electromagnetic detection by combining the spatial position of the leakage point of the dam; and analogizing in sequence until all measuring lines of the whole dam are detected, and gradually reducing the range of the abnormal area through the detection of measuring lines with different elevations so as to finally reach the trend of the leakage channel.
Preferably, when a hardening area exists from the dam crest of the dam, the position of the first-level back water slope measuring line, the position of the second-level back water slope measuring line to the position of the n-level back water slope measuring line, a transient electromagnetic measuring line is added in the hardening area.
Preferably, when the dam leaks around the dam, a transverse detection system vertical to the dam is additionally arranged at the dam abutment, a transverse line measurement system of the transverse detection system also comprises the parallel electrical method detection device, and a transverse line measurement is arranged from the top of the dam to the bottom of the dam; a backwater slope is divided into a plurality of measuring points from the top of the dam to the bottom of the dam according to equal slope distance, each measuring point corresponds to the embedded position of the copper rod, and each copper rod electrode is connected by a cable and forms a parallel electrical method detection device with a parallel electrical method instrument.
The diagnosis method of the reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system is characterized in that: the analysis system respectively carries out marshalling processing on the received parallel electrical method data body and the transient electromagnetic data body to obtain an apparent resistivity contour line, an inverted resistivity image, a measuring point-induced electromotive force curve and an apparent resistivity image of the dam crest or the impervious section of the dam; normalizing the superposed part of the apparent resistivity contour line and the apparent resistivity image, correcting the apparent resistivity contour line and the apparent resistivity image by utilizing the normalized ratio parameter, and splicing the corrected apparent resistivity contour line and the apparent resistivity image to obtain an apparent resistivity cloud picture of the dam crest of the dam; sequentially repeating the steps for the data in the marshalling step by step to obtain an apparent resistivity cloud chart of the first-level to n-level back slope full dam; and forming a full dam three-dimensional apparent resistivity diagram by the grouped apparent resistivity cloud diagrams according to a three-dimensional coordinate system diagram.
Preferably, in the diagnosis method, if the low-resistance region in the abnormal region of the three-dimensional apparent resistivity diagram of the whole dam in the horizontal direction has obvious communication characteristics from the dam top to the dam foot, the existence of a leakage channel in the section is indicated; if no obvious communication characteristic occurs from the dam crest to the dam foot in the low-resistance region in the abnormal region of the low-resistance region, the hidden danger of seepage abnormality of the dam is indicated; if the low resistance of the downstream measuring line is abnormal and the low resistance of the transverse measuring line is abnormal in the upstream normal area of the dam, the dam leaks around the dam; if each survey line dam is represented as a normal area, the dam has no hidden trouble.
The invention is described in detail below:
the longitudinal detection system is arranged to preferentially arrange a parallel electrical method detection device on the dam crest of the dam, quickly obtain a parallel electrical method two-dimensional resistivity sectional image of the dam, utilize multi-turn overlapped small-coil transient electromagnetic equipment to perform supplementary detection on a hardening part of the dam crest of the dam and blind area parts at two ends of the dam crest of the parallel electrical method, further obtain a transient electromagnetic two-dimensional resistivity sectional image, perform normalization processing on data in an overlapped area of the transient electromagnetic two-dimensional resistivity sectional image and the transient electromagnetic two-dimensional resistivity sectional image, and further perform correction calculation on the parallel electrical method two-dimensional resistivity sectional image and the transient electromagnetic two-dimensional resistivity sectional image, so that a resistivity image of the full section of the dam is obtained; combining the position of a leakage point of the dam, dividing a backwater slope of the dam into a multistage normal area and an abnormal area according to the difference of resistivity, adding the longitudinal detection system to the divided abnormal area, particularly, when the dam crest detection result shows that the dam has leakage abnormality around the dam, adding a transverse detection system close to the dam head of the dam, arranging a transverse parallel electrical method measuring line with a starting point at the dam crest and a stopping point at the dam foot, orderly exploring the leakage hidden danger of the reservoir by combining the longitudinal detection system and the transverse detection system, realizing the aim of accurately exploring the hidden danger of the dam, simultaneously improving the working efficiency and reducing the cost of comprehensive geophysical prospecting multi-method blind exploration.
In order to achieve the aim, the invention provides a reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system which comprises an analysis system, a parallel electrical method instrument, a cable, a copper bar, a transient electromagnetic instrument, a coil cable and the like.
The parallel electrical method instrument comprises a wireless transmission module, a control module and an acquisition module, wherein the wireless transmission module is used for remotely transmitting data recovered by the control module to an analysis system, the control module issues an acquisition instruction and a data recovery instruction to the acquisition module, the acquisition module is connected with a cable, the cable is connected with a copper bar, and the copper bar is fully coupled with dam filling; the analysis system has the dual function of processing parallel electrical method data and transient electromagnetic data, the analysis system gives the instruction that transient electromagnetic data retrieved to transient electromagnetic instrument, transient electromagnetic data is also data teletransmission to the analysis system of retrieving in the transient electromagnetic instrument through wireless transmission module, transient electromagnetic instrument is connected with the coil through the coil cable, the coil level is placed at dam surface and the coil normal direction is vertical downwards.
The analysis system has dual functions of recovering and processing parallel electrical data and transient electromagnetic data.
A control module in the parallel electrical method instrument acquires a data command of AMN & MNB, the parallel electrical method instrument has the characteristic of shielding electrodes, the cable comprises taps at equal intervals, and each tap is connected with the copper rod through a double-chuck lead; the length of the copper rod is 40cm, the diameter of the copper rod is 2cm, the copper rod enters a dam for 30cm during detection, meanwhile, a funnel-shaped pit is dug by taking the copper rod as a center and taking 10cm as a radius, and brine is filled in the pit;
the coil comprises a transmitting coil and a receiving coil, and is cylindrical with the diameter of 50cm, so that the coil is convenient to carry and quick to use;
the distance between the copper bars is 1m, and the point distance between the coils is 1 m; the cable line is provided with a plurality of taps, and the length of the cable line is related to the length of the dam crest of the dam;
the analysis system respectively processes the parallel electrical method data and the transient electromagnetic data, and the parallel electrical method is mainly judged according to an apparent resistivity contour line and an inversion resistivity image; the transient electromagnetic judgment is mainly based on a measuring point-induced electromotive force curve and an apparent resistivity image, wherein the measuring point-induced electromotive force curve reflects the transverse change of the dam, and the apparent resistivity image reflects the change of an anomaly in the depth direction;
the reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system further comprises a layout scheme of field measuring lines:
the combined diagnosis system comprises a longitudinal detection system and a transverse detection system; the hardened area refers to the dam crest clay layer of the dam covered by concrete precast blocks (bricks), grouted rubble, asphalt and other materials.
The number of the on-site measuring lines of the longitudinal detection system is related to the transverse width of the dam crest and the dam foot of the dam, the distance between adjacent measuring lines is 5m, and the measuring line grouping names are the dam crest measuring line, the first-stage backwater slope measuring line, the second-stage backwater slope measuring line and the third-stage backwater slope measuring line … … in sequence;
the measuring lines of the longitudinal detection system are sequentially sequenced according to the sequence, the measuring line with the corresponding sequence in the front has the advantage of preferential detection, the first measuring line is the measuring line at the top of the dam, the second measuring line is the measuring line at the first-stage backwater slope, and the rest is done in the same way;
the layout range of the primary backwater slope measuring line of the longitudinal detection system is determined by the detection abnormal area range of the dam crest measuring line, the layout range of the secondary backwater slope measuring line is determined by the abnormal area range of the primary backwater slope measuring line, and the rest can be done;
the specific implementation is that a longitudinal detection system firstly arranges parallel electrical method measuring lines on a central axis or an anti-seepage section at the top of the dam, then additionally arranges transient electromagnetic measuring lines on two dams, and simultaneously if the top of the dam has a hardening area, the area also needs to be added with the transient electromagnetic measuring lines; combining the spatial position of a leakage point of the dam, dividing the position of a first-stage backwater slope measuring line into a normal region and an abnormal region according to the parallel electrical method of the measuring line of the dam crest of the dam and the result of transient electromagnetic detection, arranging the measuring line of the parallel electrical method on the position of the abnormal region of the first-stage backwater slope measuring line, additionally arranging transient electromagnetic measuring lines on two dam shoulders, and simultaneously adding the transient electromagnetic measuring lines in the region if a hardening region is arranged on the position of the first-stage backwater slope measuring line; combining the spatial position of a leakage point of the dam, dividing the position of a second-level back slope survey line into a normal area and an abnormal area according to the results of a parallel electrical method and transient electromagnetic detection of the first-level back slope survey line of the dam, arranging the parallel electrical method survey line at the position of the abnormal area of the second-level back slope survey line, additionally arranging transient electromagnetic survey lines on two dam shoulders, and adding the transient electromagnetic survey line in the area if a hardening area is arranged at the position of the second-level back slope survey line; dividing the position of the three-level back water slope measuring line into a normal area and an abnormal area according to the parallel electrical method of the two-level back water slope measuring line of the dam and the result of transient electromagnetic detection by combining the spatial position of the leakage point of the dam; analogizing in sequence until all measuring lines of the whole dam are detected, and gradually reducing the range of the abnormal area through the detection of measuring lines with different elevations so as to finally reach the trend of the leakage channel;
particularly, if the dam has the problem of leakage around the dam, a transverse detection system vertical to the dam is additionally arranged at the dam abutment and also comprises a parallel electrical method device, and a transverse measuring line is arranged at the top of the dam and ends at the dam foot; a backwater slope is divided into a plurality of measuring points from the top of the dam to the bottom of the dam according to the equal-slope intervals, each measuring point corresponds to the burying position of the copper rod, and each copper rod electrode is connected through a cable and forms a parallel electrical method device with a parallel electrical method instrument.
Particularly, the judgment basis of the normal area and the abnormal area is the relative size of the apparent resistivity value;
the reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis method comprises the following steps:
1. data acquisition
According to the dam length of the dam, when the seepage of the dam body of the dam is detected, parallel electrical method measuring lines are arranged on a central axis or an anti-seepage section at the top of the dam, copper bars are arranged at the positions of cable line taps, a funnel-shaped pit is dug around each copper bar by taking the copper bar as the center and taking 10cm as the radius, brine is filled, and the work is sequentially carried out on all the copper bars on the dam; after all copper bars are installed, connecting cable taps with the copper bars in sequence by using double-chuck leads, connecting the cables with a parallel electrical method instrument, setting sampling parameters (data acquisition instructions, sampling time, sampling intervals, power supply modes and shielding electrodes) by using a control module of the parallel electrical method instrument, and instructing the lower part of the acquisition module, wherein when the acquisition module receives the instructions, the acquisition module sequentially supplies power and samples the copper bars on the cables in a single mode, so that the acquisition of dam natural electric field, primary field and secondary field data is realized, after the acquisition is finished, the control module recovers the acquired data body in real time, and packs all data integrally and remotely transmits the data to an analysis system through a wireless transmission module;
the transient electromagnetic survey line is also arranged on a central axis or an impervious section at the top of the dam and is positioned in two dam shoulders or a hardened area of a dam face of the dam, a transient electromagnetic survey section is defined by combining the height of the dam and the blind area position of a resistivity isoline according to a parallel electrical method, a survey point is marked in the survey section, the central point of a transient electromagnetic coil is placed on the survey point, the transient electromagnetic coil is connected with a transient electromagnetic instrument through a coil cable, parameters such as the number of turns of the coil, the transmitting frequency, the transmitting current, the superposition times, the survey mode and the like obtained by the transient electromagnetic instrument are adjusted, the optimal survey parameter is obtained by observing the attenuation characteristic of induced electromotive force, each survey point is sampled by utilizing the transient electromagnetic, and finally, all data are packed by a wireless transmission module and are remotely sent to an analysis system;
particularly, the parallel electrical method measuring lines should extend to two banks as far as possible, if the dam has the problem of leakage around the dam, a transverse detecting system vertical to the dam should be additionally arranged at the dam abutment and comprises a parallel electrical method device (namely a parallel electrical method detecting device), and the transverse measuring lines are arranged from the top of the dam to the bottom of the dam; dividing a backwater slope into a plurality of measuring points from the top of the dam to the bottom of the dam according to an equi-slope interval, wherein each measuring point corresponds to the embedded position of a copper rod, and connecting each copper rod electrode by using a cable and forming a parallel electrical method device with a parallel electrical method instrument; arranging parallel electrical method measuring lines on a dam back slope, arranging copper bars at cable line tapping positions, digging funnel-shaped pits around each copper bar by taking the copper bar as a center and taking a radius of 10cm, filling salt water, and sequentially carrying out the work on all the copper bars on the dam; after all the copper bars are installed, a double-chuck wire is sequentially used for connecting a cable tap with the copper bars, the cable is connected with a parallel electrical method instrument, a control module of the parallel electrical method instrument is used for setting sampling parameters (a data acquisition instruction, sampling time, sampling intervals, a power supply mode and a shielding electrode) and giving instructions to the lower part of the acquisition module, when the acquisition module receives the instructions, the copper bars on the cable are sequentially subjected to single power supply and multiple sampling, so that the acquisition of dam natural electric fields, primary fields and secondary field data is realized, after the acquisition is completed, the control module recovers acquired data bodies in real time, and all data are integrally packaged and remotely transmitted to an analysis system through a wireless transmission module.
Combining the spatial position of a leakage point of the dam, dividing the position of a first-stage backwater slope measuring line into a normal region and an abnormal region according to the parallel electrical method of the measuring line of the dam crest of the dam and the result of transient electromagnetic detection, arranging the measuring line of the parallel electrical method on the position of the abnormal region of the first-stage backwater slope measuring line, additionally arranging transient electromagnetic measuring lines on two dam shoulders, and simultaneously adding the transient electromagnetic measuring lines in the region if a hardening region is arranged on the position of the first-stage backwater slope measuring line; combining the spatial position of a leakage point of the dam, dividing the position of a second-level back slope survey line into a normal area and an abnormal area according to the results of a parallel electrical method and transient electromagnetic detection of the first-level back slope survey line of the dam, arranging the parallel electrical method survey line at the position of the abnormal area of the second-level back slope survey line, additionally arranging transient electromagnetic survey lines on two dam shoulders, and adding the transient electromagnetic survey line in the area if a hardening area is arranged at the position of the second-level back slope survey line; dividing the position of the three-level back water slope measuring line into a normal area and an abnormal area according to the parallel electrical method of the two-level back water slope measuring line of the dam and the result of transient electromagnetic detection by combining the spatial position of the leakage point of the dam; and analogizing in sequence until all measuring lines of the whole dam are detected, and gradually reducing the range of the abnormal area through the detection of measuring lines with different elevations so as to finally reach the trend of the leakage channel.
2. Processing of data
The analysis system carries out grouping on the received parallel electrical method data bodies, wherein the grouping comprises a dam crest measuring line data body, a primary backwater slope measuring line data body, a secondary backwater slope measuring line data body, a tertiary backwater slope measuring line data body and the like, each group of data bodies are independently processed, data of a center axis or an anti-seepage section at the dam crest are preferentially processed, then the primary backwater slope measuring line data body is processed, the secondary backwater slope measuring line data body is processed, and the like; the processing steps comprise: coordinate input, signal dryness removal, data interpretation, apparent resistivity calculation, inversion calculation and the like, and after processing, an apparent resistivity contour line and an inversion resistivity image of the dam crest or the impervious section of the dam are obtained;
particularly, the parallel electrical method dam crest data body also comprises a transverse line measurement data body;
the analysis system carries out grouping on the received transient electromagnetic data bodies, wherein the grouping comprises a dam crest data body line measurement data body, a primary backwater slope line measurement data body, a secondary backwater slope line measurement data body, a tertiary backwater slope line measurement data body and the like, each group of data bodies are independently processed, data of an axis or an anti-seepage section at the top of the dam are preferentially processed, then the primary backwater slope line measurement data body is used, the secondary backwater slope line measurement data body is used, and the like; the processing steps comprise: induced voltage display, road parameter modification, interference correction and apparent resistivity mapping, and a measuring point-induced electromotive force curve and an apparent resistivity image of the dam crest or the impervious section of the dam are obtained after processing;
particularly, the transient electromagnetic dam crest data body also comprises a transverse line measurement data body;
normalizing the overlapped part of the dam crest parallel electro-optic resistivity contour line and the transient electromagnetic apparent resistivity image, correcting the apparent resistivity contour line and the transient electromagnetic apparent resistivity image by utilizing the normalized ratio parameter, and splicing the corrected apparent resistivity contour line and the transient electromagnetic apparent resistivity image to obtain an apparent resistivity cloud picture of the dam crest of the dam;
and similarly, the steps are sequentially repeated for the data in the marshalling step by step, and the apparent resistivity cloud charts of the whole dam such as the first-stage backwater slope, the second-stage backwater slope, the third-stage backwater slope and the like are further obtained.
3. Interpretation of data
The images participating in data interpretation comprise apparent resistivity contour lines and inversion resistivity images of each group, measuring point-induced electromotive force curves and apparent resistivity images of each group and apparent resistivity cloud pictures of each group;
the apparent resistivity cloud chart of each group consists of an apparent resistivity contour line of each group and a transient electromagnetic apparent resistivity image;
the inversion resistivity and the measuring point-induced electromotive force curve of each group are used for dividing a normal area and an abnormal area of each group;
forming a full dam three-dimensional apparent resistivity map by the grouped apparent resistivity cloud maps according to a three-dimensional coordinate system;
the dam leakage occurs below the saturation line, so the basis for judging the leakage is to show the characteristic of low resistance according to the apparent resistivity, combine the construction and operation data of the reservoir dam and the position of the water outlet point of the dam foot, and indicate that a leakage channel exists in the section if the low-resistance area in the abnormal area of the three-dimensional apparent resistivity diagram of the whole dam in the horizontal direction has obvious communication characteristics from the dam top to the dam foot; if no obvious communication characteristic occurs from the dam crest to the dam foot in the low-resistance region in the abnormal region of the low-resistance region, the hidden danger of seepage abnormality of the dam is indicated; if the low resistance of the downstream measuring line is abnormal and the low resistance of the transverse measuring line is abnormal in the upstream normal area of the dam, the dam leaks around the dam; if each survey line dam is represented as a normal area, the dam has no hidden trouble.
The invention has the advantages that:
1. the parallel electrical method and the transient electromagnetic technology are combined into a whole, so that the problems of dam shoulder leakage around the dam and dam hardening are effectively solved, and the efficient detection of the whole dam without blind areas is realized;
2. the dam crest and the backwater slope are grouped according to the width of the dam, and are divided into a multi-stage normal area and an abnormal area according to detection components, so that the leakage phenomenon is effectively reduced, and the effect of accurate diagnosis is achieved;
3. the method is simple to operate, convenient to use and feasible, and the field parallel electric method and the transient electromagnetic detection are implemented in sequence, so that redundant workload is avoided;
4. according to the method, the overlapping part of the parallel electro-optic resistivity contour line and the transient electromagnetic apparent resistivity image is subjected to normalization processing, the identification capability of leakage hidden danger is improved, and meanwhile, the three-dimensional apparent resistivity image of the whole dam can clearly show information such as the buried depth, scale and trend of a leakage channel.
Drawings
FIG. 1 is a schematic diagram of the line measurement layout of a reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system,
figure 2 is a schematic diagram of a dam crest detection system,
figure 3 is a schematic illustration of the interpretation flow of the present invention,
FIG. 4 is a view (a, b) and a plan view (c) of a dam of a reservoir,
figure 5 is a high density electrical layout and isolation factor,
figure 6 is a plot of the secondary field attenuation of different bodies,
figure 7 is an apparent resistivity plot for different elevation logs,
figure 8 is an inverted resistivity section and a sample of the earth being drilled,
figure 9 is a plot of transient electromagnetic induction voltage and apparent resistivity,
FIG. 10 shows the change in reservoir level and leakage amount.
1-dam body; 2-dam abutment; 3-dam crest of dam; 4-a copper rod; 5-a cable wire; 6-parallel electrical method instrument; 7-wireless transmission module; 8-an analysis system; 9-dam crest hardening zone; 10-a coil; 11-transient electromagnetic instruments; 12-a coil cable; 13-backwater slope.
Detailed Description
1. As shown in fig. 1, detection measuring lines are named as dam crest measuring lines, primary backwater slope measuring lines, secondary backwater slope measuring lines and tertiary backwater slope measuring lines … … in sequence according to the transverse width from the dam crest to the dam toe; when the dam has the leakage problem around the dam, a transverse measuring line vertical to the dam is additionally arranged at the dam abutment, and the transverse measuring line is arranged from the top of the dam to the bottom of the dam.
2. As shown in fig. 2, when detecting the leakage of the dam body 1 of the dam according to the dam length of the dam, parallel electrical method measuring lines are arranged on the axis or the seepage-proofing section of the dam crest 3 of the dam, copper bars 4 are arranged at the position of a cable 5 tap, a funnel-shaped pit is dug around each copper bar by taking the copper bar 4 as the center and taking the 10cm as the radius, brine is filled, and the work is sequentially carried out on all the copper bars 4 on the dam crest 3 of the dam; after all the copper bars 4 are installed, connecting cable taps with the copper bars 4 in sequence by using double-chuck leads, connecting the cables 5 with an acquisition module of a parallel electrical method instrument 6, setting sampling parameters (acquisition data instructions, sampling time, sampling intervals, power supply modes and shielding electrodes) by using a control module of the parallel electrical method instrument 6 and giving instructions to the lower part of the acquisition module, and when the acquisition module receives the instructions, sequentially carrying out single power supply and multiple sampling on the copper bars on the cables 5 so as to realize the acquisition of the data of the natural electric field, the primary field and the secondary field of the dam, and after the acquisition is finished, recovering the acquired data body in real time by using the control module and remotely transmitting all the data to an analysis system 8 through a wireless transmission module 7 in a whole package mode;
the transient electromagnetic survey line is also arranged on a central axis or an impervious section of the dam top 3 of the dam, is positioned in two dam shoulders 2 or a dam face hardening area 9 of the dam, is combined with the height of the dam and the blind area position of a resistivity isoline according to a parallel electrical method to demarcate a transient electromagnetic survey section, marks a measuring point in the survey section, places the central point of a transient electromagnetic coil 10 on the measuring point, connects the transient electromagnetic coil 10 with a transient electromagnetic instrument 11 through a coil cable 12, adjusts the parameters of the transient electromagnetic instrument such as the coil turn number, the transmitting frequency, the transmitting current, the superposition times, the measuring mode and the like, obtains the optimal survey parameter by observing the attenuation characteristic of the induced electromotive force, samples each measuring point by using the transient electromagnetic, and finally packs all data integrally and sends the data to an analysis system 8 through a wireless transmission module 7.
If the dam has the problem of leakage around the dam, a transverse line measuring system (namely a transverse detection system) vertical to the dam is additionally arranged at the dam abutment, the transverse detection system of the dam comprises a parallel electrical method device, and the transverse line measuring system is arranged at the top of the dam and ends at the dam foot; specifically, a backwater slope is divided into a plurality of measuring points from the top of the dam to the bottom of the dam according to an equi-slope interval, each measuring point corresponds to the embedded position of a copper bar, and each copper bar electrode is connected by a cable and forms a parallel electrical method device with a parallel electrical method instrument; arranging parallel electrical method measuring lines on a dam back slope, arranging copper bars at cable line tapping positions, digging funnel-shaped pits around each copper bar by taking the copper bar as a center and taking a radius of 10cm, filling salt water, and sequentially carrying out the work on all the copper bars on the dam; after all the copper bars are installed, a double-chuck wire is sequentially used for connecting a cable tap with the copper bars, the cable is connected with a parallel electrical method instrument, a control module of the parallel electrical method instrument is used for setting sampling parameters (a data acquisition instruction, sampling time, sampling intervals, a power supply mode and a shielding electrode) and giving instructions to the lower part of the acquisition module, when the acquisition module receives the instructions, the copper bars on the cable are sequentially subjected to single power supply and multiple sampling, so that the acquisition of dam natural electric fields, primary fields and secondary field data is realized, after the acquisition is completed, the control module recovers acquired data bodies in real time, and all data are integrally packaged and remotely transmitted to an analysis system through a wireless transmission module.
Combining the spatial position of a leakage point of the dam, dividing the position of a first-stage backwater slope measuring line into a normal region and an abnormal region according to the 4-line measuring parallel electrical method and the transient electromagnetic detection result of the dam crest of the dam, arranging a parallel electrical method measuring line at the position of the abnormal region of the first-stage backwater slope measuring line, additionally arranging transient electromagnetic measuring lines on two dam shoulders, and adding a transient electromagnetic measuring line in the region if a hardening region is arranged at the position of the first-stage backwater slope measuring line; combining the spatial position of a leakage point of the dam, dividing the position of a second-level back slope survey line into a normal area and an abnormal area according to the results of a parallel electrical method and transient electromagnetic detection of the first-level back slope survey line of the dam, arranging the parallel electrical method survey line at the position of the abnormal area of the second-level back slope survey line, additionally arranging transient electromagnetic survey lines on two dam shoulders, and adding the transient electromagnetic survey line in the area if a hardening area is arranged at the position of the second-level back slope survey line; dividing the position of the three-level back water slope measuring line into a normal area and an abnormal area according to the parallel electrical method of the two-level back water slope measuring line of the dam and the result of transient electromagnetic detection by combining the spatial position of the leakage point of the dam; and analogizing in sequence until all measuring lines of the whole dam are detected, and gradually reducing the range of the abnormal area through the detection of measuring lines with different elevations so as to finally reach the trend of the leakage channel.
3. The analysis system carries out grouping on the received parallel electrical method data bodies, wherein the grouping comprises a dam crest measuring line data body, a primary backwater slope measuring line data body, a secondary backwater slope measuring line data body, a tertiary backwater slope measuring line data body and the like, each group of data bodies are independently processed, data of a center axis or an anti-seepage section at the dam crest are preferentially processed, then the primary backwater slope measuring line data body is processed, the secondary backwater slope measuring line data body is processed, and the like; the processing steps comprise: coordinate input, signal dryness removal, data interpretation, apparent resistivity calculation, inversion calculation and the like, and after processing, an apparent resistivity contour line and an inversion resistivity image of the dam crest or the impervious section of the dam are obtained;
particularly, the parallel electrical method dam crest data body also comprises a transverse line measurement data body;
the analysis system carries out grouping on the received transient electromagnetic data bodies, wherein the grouping comprises a dam crest data body line measurement data body, a primary backwater slope line measurement data body, a secondary backwater slope line measurement data body, a tertiary backwater slope line measurement data body and the like, each group of data bodies are independently processed, data of an axis or an anti-seepage section at the top of the dam are preferentially processed, then the primary backwater slope line measurement data body is used, the secondary backwater slope line measurement data body is used, and the like; the processing steps comprise: induced voltage display, road parameter modification, interference correction and apparent resistivity mapping, and a measuring point-induced electromotive force curve and an apparent resistivity image of the dam crest or the impervious section of the dam are obtained after processing;
particularly, the transient electromagnetic dam crest data body also comprises a transverse line measurement data body;
normalizing the overlapped part of the dam crest parallel electro-optic resistivity contour line and the transient electromagnetic apparent resistivity image, correcting the apparent resistivity contour line and the transient electromagnetic apparent resistivity image by utilizing the normalized ratio parameter, and splicing the corrected apparent resistivity contour line and the transient electromagnetic apparent resistivity image to obtain an apparent resistivity cloud picture of the dam crest of the dam;
and similarly, the steps are sequentially repeated for the data in the marshalling step by step, and the apparent resistivity cloud charts of the whole dam such as the first-stage backwater slope, the second-stage backwater slope, the third-stage backwater slope and the like are further obtained.
4. Interpretation of data
The images participating in data interpretation comprise apparent resistivity contour lines and inversion resistivity images of each group, measuring point-induced electromotive force curves and apparent resistivity images of each group and apparent resistivity cloud pictures of each group;
the apparent resistivity cloud chart of each group consists of an apparent resistivity contour line of each group and a transient electromagnetic apparent resistivity image;
the inversion resistivity and the measuring point-induced electromotive force curve of each group are used for dividing a normal area and an abnormal area of each group;
forming a full dam three-dimensional apparent resistivity map by the grouped apparent resistivity cloud maps according to a three-dimensional coordinate system;
the dam leakage occurs below the saturation line, so the basis for judging the leakage is to show the characteristic of low resistance according to the apparent resistivity, combine the construction and operation data of the reservoir dam and the position of the water outlet point of the dam foot, and indicate that a leakage channel exists in the section if the low-resistance area in the abnormal area of the three-dimensional apparent resistivity diagram of the whole dam in the horizontal direction has obvious communication characteristics from the dam top to the dam foot; if no obvious communication characteristic occurs from the dam crest to the dam foot in the low-resistance region in the abnormal region of the low-resistance region, the hidden danger of seepage abnormality of the dam is indicated; if the low resistance of the downstream measuring line is abnormal and the low resistance of the transverse measuring line is abnormal in the upstream normal area of the dam, the dam leaks around the dam; if each survey line dam is represented as a normal area, the dam has no hidden trouble.
Detailed description of the preferred embodiment
The method is characterized in that a dockside reservoir leakage exploration is used as a test object, a multi-elevation hidden danger exploration is carried out on a reservoir dam by utilizing a parallel electrical method, the distribution range of a weak leakage area of the dam is comprehensively judged according to transient electromagnetic exploration results, the downstream leakage amount is obviously reduced after directional treatment is carried out on a target area, and reference is provided for optimization and selection of a comprehensive geophysical prospecting method for accurately diagnosing the engineering hidden danger of the reservoir dam.
1. Engineering overview and exploration arrangement
The family depressed reservoir is located in Jiulicun village in Tianmu mountain town of Lin-an district of Hangzhou city, the reservoir is established in 12 months of 1957, the dam is a clay core wall dam, and the total storage capacity is 11.1 ten thousand meters3Its functions are urban water supply and irrigation. The length of the dam crest of the dam is 54m, the width of the dam crest is 3.5m, the elevation of the dam crest is 157.5m, and the maximum dam height is 14.4 m; the spillway is positioned on the right bank of the dam and is of a straight groove type; the water discharging facility is a siphon pipe, the material is a steel pipe with the inner diameter of 20cm, and the elevation of the horizontal section of the hump is 152.8 m.
The reservoir dam is a living engineering structure, and along with the continuous increase of engineering service life, the problem of aging of the internal structure of the dam is more and more prominent, and especially along with the frequent occurrence of extreme weather, the safety risk is increased. For example, when a family dock reservoir is worn in 8 months in 2009 and is influenced by Moraxel typhoon, a dam has dangerous situations such as local piping and collapse, and a left dam slope has a serious leakage phenomenon. Because the reason and the spatial position of dam leakage are not clear, although the dam is subjected to seepage-proofing reinforcement treatment for many times, the hidden danger of leakage is not fundamentally solved, and the reservoir can only be kept to operate at a low water level, so that the normal performance of reservoir benefits is influenced. In order to solve the problem of persistent leakage of the reservoir dam and consider that the distribution positions of hidden dangers are variable, a mode of combining a parallel electrical method and transient electromagnetism is provided for searching hidden danger positions, and a targeted area is provided for radical treatment of leakage diseases.
As shown in fig. 4(c), 3 parallel electrical method measuring lines (PL-1, PL-2 and PL-3) are arranged on the top of the dam and the backwater slope, the directions of the measuring lines are all from the right bank to the left bank, wherein the starting point of the measuring line PL-1 is located at the pile number K0-006m (taking the right dam head as the starting point, the same below), the total number of all measuring line electrodes is respectively 64, 48 and 41, and the minimum electrode spacing is 1 m; the initial point of the transient electromagnetic survey line at the top of the dam is positioned at the spillway on the left bank (pile number K0-011m), the total number of the survey points is 67, and the distance between the adjacent survey points is 1 m.
Working method
2.1 parallel electrical method technique
The parallel electrical method (Liu Sheng Dong, etc., 2019) is firstly proposed by the university of Anhui Ringjian and Jiangsu Donghua test GmbH, absorbs the idea of data acquisition in the seismic exploration process, utilizes the power supply electrodes to inject stable and constant current into the underground to form an electric field, arranges all the measuring electrodes to synchronously and parallelly record earth electricity data at different positions, and finally extracts, separates and combines the current and potential data combination according to the needs so as to obtain different device data bodies and general device information. Therefore, the basic principle of the parallel electrical method is the same as that of the high-density electrical method, and only the serial acquisition thought of a sub-device and a sub-electric field is no longer limited in data acquisition, so that the working efficiency is higher, the anti-interference capability is stronger, and the application range of the parallel electrical method in hydrology, environment and engineering is wider (YueJian Hua, etc., 2016).
The parallel electricity method adopts a point power supply mode in the application of reservoir dams, through single-point power supply, earth electricity information with two poles, three poles and high resolution can be obtained through multi-pole collection, and particularly, the resolution of hidden dangers and the depiction of dam boundaries are greatly improved through multi-device data combined processing (Mahuan et al, 2018). As shown in fig. 5;
2.2 transient electromagnetic method
The transient electromagnetic technique is to supply step pulse square wave through a non-grounded return wire or a grounded electrode, observe the induced voltage of a secondary field by using a probe or a receiving coil in the interval period of power failure, and infer the space-time distribution of a geologic body by analyzing the induced electromotive force attenuation characteristics of a single point at different moments and the change trend of multiple points at the same depth (Xue Guo et al, 2015). The research object of the transient electromagnetic method is the change of a pure secondary field, so that the signal response to the low-resistance abnormal body is more obvious, and the antenna is laid parallel to the dam crest to continuously obtain the signal of the whole dam, so that the transient electromagnetic method has the characteristic of strong directivity. When the packaged and modularized multi-turn small coil is used for detection on site, the requirement of high-efficiency and portable inspection of the dam can be met only by moving the coil according to the appointed step. The interpretation of the transient electromagnetic detection data of the reservoir dam mainly depends on attenuation curves and apparent resistivity images of different secondary fields, firstly, the transverse abnormality is preliminarily identified according to the characteristics of different measuring point-voltage curves, and then, the depth information of hidden danger is judged and read according to the calculated apparent resistivity.
2.2 optimization of the detection method
Under the action of hydrostatic pressure in the reservoir area, fine particles in the soil body continuously run off, and when normal seepage behavior deteriorates to form a local seepage channel, hidden dangers such as local void, incompact or hollow are generated in the dam. The leakage of the dam is under the saturation line, and the hidden danger of the dam in a saturated state has obvious low-resistance characteristic compared with surrounding media, thereby providing a physical property premise for the implementation of a parallel electrical method. For the leakage area of the joint part of the two dam shoulders with frequent hidden danger, the parallel electrical method is difficult to effectively identify low-resistance information due to the high-resistance shielding of the rock foundation, and the leakage area is just the blind area part of the parallel electrical method due to the constraint of the site condition of the dam. The basic electromagnetic induction principle of the transient electromagnetic method is weak in response to high resistance and has the inherent advantage of checking low resistance in a high-resistance area, and the complementary advantages of the two methods are beneficial to improving the level of diagnosing the hidden danger of the whole dam.
3 analysis and verification of test results
3.1 parallel Electrical method data processing and analysis
The test site adopts a WBD-1 type parallel electrical method instrument as a collector, the power supply mode is a single positive method, the constant current time is 0.5s, and the sampling interval is 0.05 s. Data of different elevations are subjected to de-coding, extraction, de-noising and gridding to obtain a Wennan three-pole right device apparent resistivity profile (as shown in figure 7), the elevation of a reservoir water level is 153.8m during testing, the range of an apparent resistivity value obtained by a measuring line PL-1 is 90-230 omega.m, 25-35 m sections of low-resistance abnormal areas on the measuring line are distributed in a closed ring shape, the buried depth is about 10m, 0-20 m sections on the measuring line are distributed in a strip shape within 5m of depth and have a tendency of extending to a right bank, and in view of the fact that electrodes cannot penetrate through concrete and are directly coupled with a dam from a measuring line starting point to a spillway section, an electrical profile measuring blind area is formed on the right bank, and whether the low-resistance abnormal area exists on the right bank or not needs to be supplemented by other methods; the low resistance abnormal areas in the images of the measuring lines PL-2 and PL-3 are more visual, the shapes reflected by the low resistance abnormal areas and the low resistance abnormal areas are basically consistent, and the low resistance abnormal areas are probably related to the fact that the flow direction of the leakage channel on the backwater slope is more stable and the distance between the ground measuring lines and the ground measuring lines is closer. Comparing the low-resistance abnormal region distributions in fig. 7(a, b, c), it can be seen that: the dam body part of the dam has a low-resistance closed abnormal region, the position of the abnormal region on a measuring line of a backwater slope has certain transverse movement and also shows a certain inclined form, and the low-resistance abnormal region at the downstream of the backwater slope is inferred to be possibly caused by the joint convergence of a low-resistance weak zone in the middle of the dam top and a low-resistance weak region of a right dam section, wherein the low-resistance trap abnormal region exists at a position of 30m in a graph 7(c), but no obvious abnormality exists on a measuring graph 7(b), so that the position of a concentrated leakage point is required to be considered when the abnormality at the position is analyzed.
The apparent resistivity value obtained by the high-density electrical method is a local response to a geologic body, the abnormal bodies reflected by different arrangement forms possibly have differences in depth, position, burial depth and form (such as the square-easy-small lock, 2019), and the three-pole device adopts a potential gradient measurement mode, so that the apparent resistivity images of the AMN and the MNB have certain asymmetry (such as the Huxiwu, 2018). Inversion is an optimal processing method for the measured data volume model reconstruction, is limited by space, and is illustrated by the result of a dam crest measuring line PL-1 of a dam, and fig. 8 is an inversion result graph of Wennan tripolar.
This document uses a least squares method based on a rounded model (Loke et al, 2012), whose expression:
(JTJ+λF)Δqk＝JTg-λFqk-1
wherein J is a Jacobi matrix; λ is a damping factor; g the residual between the measured apparent resistivity value and the calculated value.
FIG. 8(a) is the image obtained by the inversion calculation in FIG. 7(a), it can be seen that the inverted cross-sectional view is more finely characterized for the details of the dam, and the low-resistance abnormal region is also shifted to the right bank; fig. 8(b) is an inverted cross section of the wenner three-pole left device, and the low-resistance abnormal region in the middle of the dam is enlarged compared with fig. (a). In addition, as can be seen from comparing fig. 8(a) and (b), the winner tripolar left-right device shows that the shape of the dam foundation is greatly different, and may be related to the positions of the power supply and measurement points of the two devices. In order to reduce the difference of different devices, joint inversion of data volumes of two devices is a solution. The joint inversion image shown in fig. 8(c) absorbs the advantages of the two devices, and the description of the shape of the dam abutment rock foundation and the low-resistance abnormity of the dam is more reliable.
3.2 transient electromagnetic data processing and analysis
In the transient electromagnetic field, a multi-turn small loop coil is adopted to transmit and receive signals, the number of turns of a transmitting coil is 10, the number of turns of a receiving coil is 67, the transmitting frequency is 25HZ, the number of superposition times is 512, and a data body is subjected to flying spot removal, curve smoothing, coordinate setting, resistivity calculation and other steps in matched processing software to obtain a graph 9. FIG. 9(a) is a voltage variation curve diagram of all measuring points, and it can be seen from late signals of a dam that there are response characteristics of obvious secondary field signals in sections of 6-13 m, 24-27 m, 42-45 m and 54-60 m on a measuring line, which indicates that there may be a low-resistance zone seepage weak zone at the lower part of the zone; in the graph (b), apparent resistivity is distributed in a strip-shaped low-resistance mode within the range of 3m of burial depth, and is possibly related to a blind zone (sweep coins, 2016) formed by the influence of the turn-off time of a transient electromagnetic instrument, the depths of an impervious body and a seepage line of a general reservoir dam are lower relative to the blind zone, and the blind zone does not influence the judgment of the leakage hidden trouble of the dam. According to the apparent resistivity profile, the amplitude of low-resistance abnormity of 6-12 m on the measuring line is the largest, and a leakage channel possibly exists; the measuring line 24-27 m is positioned at the upper part of the siphon, so that certain interference of iron on electromagnetic field signals is not eliminated.
3.3 analysis of comprehensive exploration results
The parallel electrical method and the transient electromagnetic method respectively obtain earth electrical signals of the reservoir dam from the angles of the electrostatic field and the electromagnetic field, the earth electrical signals and the transient electromagnetic method have obvious response to leakage hidden dangers of the reservoir dam, the result reflected by the leakage hidden dangers in the dam body of the dam is more reliable, and the transient electromagnetic method has more advantages in detecting the leakage of the dam abutment.
The apparent resistivity images of 3 measuring lines on the dam crest and the backwater slope of the dam by the parallel electrical method can reflect low-resistance leakage hidden trouble areas, but the low-resistance leakage hidden trouble areas of the measuring lines on the dam crest are relatively regular, the form and space position matching degree of two measuring lines at the downstream is high, and a leakage channel has a tendency of extending towards a riverbed section; the range (18-40 m on the measuring line) of the low-resistance area of the joint inversion image at the dam crest of the dam is further expanded and is consistent with the flow direction of a leakage channel of two measuring lines at the downstream. Transient electromagnetic detection results are relatively more definite, seepage flow weak areas are mainly distributed in three sections, and the influence of a siphon pipe needs to be considered when the low-resistance abnormality of 24-27 m on a measuring line.
As the dam body segment shows strong low-resistance abnormality in the parallel electrical method image (pile number K0+ 012-K0 +034m) and the transient electromagnetic image (pile number K0-005-0 +002m), the drilling verification is carried out for further determining the reliability of the result. As shown in FIGS. 8(d) and (e), the filling section and the in-hole camera of the dam with the pile number K0+020m are shown in the filling section of the dam with the pile number K0+020m, the section with the hole depth of 0-11 m is broken stone-containing powdery clay, the gray brown soft plastic powdery clay is disclosed below 11m, wherein 9.5-10 m of the clay is locally mixed with broken stones, and the dam with the filling section has poor overall filling quality, more broken stones and local incompact phenomenon by combining the in-hole camera achievement of 0-8 m, which indicates that the dam filling body disclosed by the drilled hole may have local seepage abnormal phenomenon. The drilling of the pile number K0+000 shows that the hole depth is more than 5.3m, the broken stone-containing silty clay is contained, the strong-weak weathering sandstone is arranged below, the rock mass is extremely broken, cracks develop, and the dam foundation has serious leakage problem.
In conclusion, from the detection results of the two methods, the low-resistance abnormal area of the dam crest of the dam is mainly located in the sections with the pile numbers of K0-005-K0 +002m, K0+ 012-K0 +034m and K0+ 043-K0 +049m, and the section is presumed to be a seepage weak area causing dam seepage.
3.4 Directional treatment of leakage potential
The purpose of detecting the leakage hidden trouble of the reservoir dam is to provide a target area for the seepage control treatment design, and because the seepage weak zones of the earth-rock dam are distributed in a complex manner, the grouting seepage control treatment is carried out on the low-resistance abnormal area of the dam for more scientifically evaluating the detection result of comprehensive geophysical prospecting. As shown in fig. 10, when grouting starts in a dock-mounted reservoir (12/7/2018), the reservoir water level elevation is 155.12m, the concentrated leakage amount of the dam toe is 3.89L/s, the reservoir water level is basically kept stable in the whole seepage-proofing treatment process, and the leakage amount is changed in series, wherein the leakage amount is reduced to 2.91L/s in 18/7 th day, is reduced to 2.64L/s after grouting for the pile number K0+046 in 25/7 th day, and is obviously reduced after grouting for the two positions of the pile numbers K0-003 and K0+000, and the leakage amount is reduced to 0.07L/s. And then, the dam is subjected to enhanced seepage-proofing treatment, so that the seepage amount is reduced to be close to the allowable seepage amount, and the requirement of dam seepage-proofing is met.
Conclusion
In the case, a seepage-proofing treatment project of a docking station reservoir is taken as a test object, the hidden danger of dam seepage is probed by combining a parallel electrical method and a transient electromagnetic technology, a local suspicious weak area is verified by utilizing a project drilling and in-hole camera shooting technology, and finally directional grouting treatment is carried out according to a detection result, so that the problem of dam seepage is successfully solved.
(1) The parallel electrical method adopts a data acquisition mode of simulating earthquake, can obtain various high-density electrical method device data bodies by one-time acquisition, and has high working efficiency; the trend of a dam leakage channel can be determined by comparing apparent resistivity images with different elevations, and the joint inversion of a Wenna tripolar left-right device is favorable for homing of saphenous bodies and rock foundation identification of dam shoulders;
(2) the transient electromagnetic technology with the multiple turns of small coils is convenient to operate, is suitable for a complex field, and effectively identifies the low-resistance abnormal part in the longitudinal and transverse directions of the dam by interpreting a measuring point-voltage curve and an apparent resistivity profile;
(3) the parallel electrical method has high accuracy in judging the hidden dangers of the dam body of the dam, the transient electromagnetic method is suitable for exploring the hidden dangers of the dam abutment joint part, and the two technologies are combined with each other to form a set of comprehensive detection technology for the leakage diagnosis of the whole dam.
Reference to the literature
1. Louis Small Lock, Monyon, Tianbin, et al 2019, resolution response study of high density resistivity method to different electrode arrangements [ J ] geophysical evolution 34(6) 2421-: 10.6038/pg2019CC0313.
2. Huxiongwu, Lihong.2018, application of forward and reverse tripolar resistivity joint inversion in reservoir leakage detection [ J ] water conservancy and hydropower technology, 49(10):173-17, doi:10.13928/j.cnki.wrahe.2018.10.024.
3. Liu Sheng Dong, Liu Jing, Yunji, etc. 2019. mine parallel electrical method technical system and new development [ J ] coal bulletin, 44(8): 2336-.
4. Albizzia, Guo Yue, Spirodela, et al.2018 three-dimensional joint inversion of multiple device data based on MPI parallel algorithm the geophysical report, 61(12): 5052-: 10.6038/cjg2018M0005.
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Claims (10)

1. A reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system comprises a longitudinal detection system, wherein the longitudinal detection system comprises a parallel electrical method detection device and a transient electromagnetic detection device, the parallel electrical method detection device comprises a parallel electrical method measuring line and a parallel electrical method instrument which are arranged on a central axis or an anti-seepage end surface at the top of a dam, and the parallel electrical method measuring line comprises copper bars which are adjacently inserted on the dam at intervals and cables connected with the copper bars; the transient electromagnetic detection device comprises a transient electromagnetic measuring line and a transient electromagnetic instrument which are arranged on a dam crest central axis or an impervious section of two dam shoulders of a dam and/or a dam crest hardening area, wherein the transient electromagnetic measuring line comprises a coil arranged on a measuring point and a coil cable connected with the coil; the cable and the coil cable are respectively connected with a parallel electrical method instrument and a transient electromagnetic instrument; the parallel electrical method instrument and the transient electromagnetic instrument are used for connecting with an analysis system.
2. The diagnostic system of claim 1, wherein: after the copper rod is inserted into the dam, a funnel-shaped pit is dug in the range with the copper rod as the center and the radius of 10cm, and brine is filled in the pit.
3. The diagnostic system of claim 1, wherein: the coils are placed horizontally on the surface of the dam and the coil normal is vertically downward.
4. The diagnostic system of claim 1, wherein: the parallel electrical method instrument is provided with a wireless transmission module, a control module and an acquisition module, wherein the acquisition module is connected with a cable, the control module is used for issuing an acquisition instruction and a data recovery instruction to the acquisition module, and the wireless transmission module is used for remotely transmitting data recovered by the control module to an analysis system; the analysis system has the dual functions of processing parallel electrical data and transient electromagnetic data, issues a transient electromagnetic data recovery instruction to the transient electromagnetic instrument, and remotely transmits data recovered in the transient electromagnetic instrument to the analysis system through the wireless transmission module.
5. The diagnostic system of any one of claims 1-4, wherein: when the measuring lines are laid on site, the dam crest measuring lines, the first-level back water slope measuring lines, the second-level back water slope measuring lines, the third-level back water slope measuring lines and the n-level back water slope measuring lines are sequentially laid along the transverse width direction from the dam crest to the dam foot of the dam, and the distance between every two adjacent measuring lines is 5 m; the measuring line of the backwater slope of the next stage is determined by the range of the abnormal detection region of the previous stage.
6. The diagnostic system of claim 5, wherein: laying parallel electrical method measuring lines on a central axis or an impervious section of the top of the dam, laying transient electromagnetic measuring lines on two dams, dividing the position of a primary backwater slope measuring line into a normal region and an abnormal region according to the dam top parallel electrical method and the transient electromagnetic detection result by combining the spatial position of a leakage point of the dam, arranging the parallel electrical method measuring lines on the position of the abnormal region of the primary backwater slope measuring line, and then additionally arranging the transient electromagnetic measuring lines on the two dams; combining the spatial position of a leakage point of the dam, dividing the position of a second-level back slope measuring line into a normal area and an abnormal area according to the result of the parallel electrical method and the transient electromagnetic detection of the first-level back slope measuring line of the dam, arranging the parallel electrical method measuring line on the position of the abnormal area of the second-level back slope measuring line, and additionally arranging the transient electromagnetic measuring line on two dam shoulders; dividing the position of the three-level back water slope measuring line into a normal area and an abnormal area according to the parallel electrical method of the two-level back water slope measuring line of the dam and the result of transient electromagnetic detection by combining the spatial position of the leakage point of the dam; and analogizing in sequence until all measuring lines of the whole dam are detected, and gradually reducing the range of the abnormal area through the detection of measuring lines with different elevations so as to finally reach the trend of the leakage channel.
7. The diagnostic system of claim 6, wherein: when a hardening area exists from the dam crest of the dam, the position of the first-level back water slope measuring line, the position of the second-level back water slope measuring line to the position of the n-level back water slope measuring line, a transient electromagnetic measuring line is added in the hardening area.
8. The diagnostic system of claim 5 or 6, wherein: when the dam leaks around the dam, a transverse detection system vertical to the dam is additionally arranged at the dam abutment, a transverse line measurement system of the transverse detection system also comprises the parallel electrical method detection device, and a transverse line measurement is arranged from the top of the dam to the bottom of the dam; a backwater slope is divided into a plurality of measuring points from the top of the dam to the bottom of the dam according to equal slope distance, each measuring point corresponds to the embedded position of the copper rod, and each copper rod electrode is connected by a cable and forms a parallel electrical method detection device with a parallel electrical method instrument.
9. The diagnostic method of the diagnostic system of any one of claims 1 to 8, wherein: the analysis system respectively carries out marshalling processing on the received parallel electrical method data body and the transient electromagnetic data body to obtain an apparent resistivity contour line, an inverted resistivity image, a measuring point-induced electromotive force curve and an apparent resistivity image of the dam crest or the impervious section of the dam; normalizing the superposed part of the apparent resistivity contour line and the apparent resistivity image, correcting the apparent resistivity contour line and the apparent resistivity image by utilizing the normalized ratio parameter, and splicing the corrected apparent resistivity contour line and the apparent resistivity image to obtain an apparent resistivity cloud picture of the dam crest of the dam; sequentially repeating the steps for the data in the marshalling step by step to obtain an apparent resistivity cloud chart of the first-level to n-level back slope full dam; and forming a full dam three-dimensional apparent resistivity diagram by the grouped apparent resistivity cloud diagrams according to a three-dimensional coordinate system diagram.
10. The diagnostic method of claim 9, wherein: if the low-resistance region in the abnormal region of the three-dimensional apparent resistivity diagram of the whole dam in the horizontal direction has obvious communication characteristics from the dam crest to the dam foot, indicating that a leakage channel exists in the section; if no obvious communication characteristic occurs from the dam crest to the dam foot in the low-resistance region in the abnormal region of the low-resistance region, the hidden danger of seepage abnormality of the dam is indicated; if the low resistance of the downstream measuring line is abnormal and the low resistance of the transverse measuring line is abnormal in the upstream normal area of the dam, the dam leaks around the dam; if each survey line dam is represented as a normal area, the dam has no hidden trouble.
CN202011398401.9A 2020-12-04 2020-12-04 Reservoir dam parallel electrical method and transient electromagnetic technology combined diagnosis system and method Pending CN112540410A (en)

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CN113155380A (en) * 2021-04-17 2021-07-23 河北广宸建筑工程检测有限公司 Earth and rockfill dam leakage hidden danger detection and directional processing system and method
CN114965181A (en) * 2022-05-25 2022-08-30 中南大学 Rapid automatic positioning method for seepage-proofing barrier leakage area based on transient electromagnetic detection image
CN116754135A (en) * 2023-06-21 2023-09-15 水利部交通运输部国家能源局南京水利科学研究院 Thin core wall rock-fill dam leakage focus evolution monitoring and early warning system and method

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113155380A (en) * 2021-04-17 2021-07-23 河北广宸建筑工程检测有限公司 Earth and rockfill dam leakage hidden danger detection and directional processing system and method
CN114965181A (en) * 2022-05-25 2022-08-30 中南大学 Rapid automatic positioning method for seepage-proofing barrier leakage area based on transient electromagnetic detection image
CN114965181B (en) * 2022-05-25 2024-05-14 中南大学 Rapid automatic positioning method for seepage-proof barrier leakage area based on transient electromagnetic detection image
CN116754135A (en) * 2023-06-21 2023-09-15 水利部交通运输部国家能源局南京水利科学研究院 Thin core wall rock-fill dam leakage focus evolution monitoring and early warning system and method
CN116754135B (en) * 2023-06-21 2024-02-23 水利部交通运输部国家能源局南京水利科学研究院 Thin core wall rock-fill dam leakage focus evolution monitoring and early warning system and method

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