CN110703335A

CN110703335A - Towed underwater geological electrical detection system and method

Info

Publication number: CN110703335A
Application number: CN201911007529.5A
Authority: CN
Inventors: 张平松; 欧元超; 孙斌杨; 李圣林; 刘畅; 许时昂
Original assignee: Anhui University of Science and Technology
Current assignee: Anhui University of Science and Technology
Priority date: 2019-10-22
Filing date: 2019-10-22
Publication date: 2020-01-17
Also published as: ZA201907538B

Abstract

The invention discloses a towed underwater geology electrical method detection system and a towed underwater geology electrical method detection method, which comprise the following steps: the system comprises an underwater cable, a simple underwater electrode, a water pressure measuring and sensing unit, a cable floating and sinking unit, an underwater GPS (global positioning system), an inflator, an electrical method data acquisition and storage module and a data processing module; the underwater cable is fixed with the cable floating and sinking unit, and the cable floating and sinking unit is connected with the inflator; the underwater cable is sequentially connected with the electric method data acquisition and storage module and the data processing module; a simple underwater electrode and a water pressure measuring and sensing unit are fixed on the underwater cable; the underwater GPS positioning system comprises a transponder, a shipborne transducer and a GPS; the transponder is fixed at the front, middle and tail simple underwater electrodes on the underwater cable; the transponder is wirelessly connected with the shipborne transducer; the GPS is fixed on the tug. The towed underwater geologic electrical detection system and method provided by the invention solve the defects and problems in the existing underwater geologic electrical detection, and have good application prospects.

Description

Towed underwater geological electrical detection system and method

Technical Field

The invention relates to the technical field of geophysical exploration, in particular to a towed underwater geologic electrical method detection system and method.

Background

With the acceleration of the urbanization process in China, the foundations of all regions are built and arranged to be conducted vigorously. Among them, underwater infrastructure related to underwater rock-soil body structures, underwater environmental resources, river-crossing underwater engineering construction projects, and the like, is increasing year by year. Therefore, geological information such as the water bottom geological structure and the like is analyzed and judged in advance through related technical detection means, and the method has important significance on later engineering design, measure formulation, safety construction and the like.

At present, the technical means for acquiring the underwater geologic structure, abnormality and the like comprise drilling, ground penetrating radar, transient electromagnetism, sonar, seismic exploration, conventional electrical prospecting and the like. The drilling can directly obtain the water bottom geological information of a certain position under water, but the drilling consumes time and labor and cannot obtain the water bottom geological information in the whole area; the electromagnetic wave transmitted by the ground penetrating radar is quickly attenuated in water, limited geological information such as a water bottom bed rock surface and the like can be obtained only due to the limitation of the detection depth, and the geological information at the lower part of the water bottom cannot be detected with high precision; the transient electromagnetism has serious low-resistance shielding phenomenon caused by low-resistance water, the high-precision transient electromagnetism can obtain a water bottom geological structure with the depth of kilometers, but the accurate detection resolution of a small-scale target body in a shallow geological body such as human underwater engineering construction is difficult to achieve; underwater sonar and seismic exploration have limited resolving power on targets in sedimentary layers below the water bottom surface, so that a hidden underwater target body with relatively small scale is difficult to effectively detect; the conventional electrical prospecting is to move a cable and a collecting instrument for ground electrical prospecting to a water area for detection, and has the defects of low construction measurement efficiency, slow data collection, poor controllability, low accuracy and the like.

In response to the shortcomings of conventional electrical prospecting currently applied to water areas, improvements have been made by those skilled in the art. The invention patent with the publication number of CN105259584B and the name of a water area electrical prospecting system discloses that a transmitter outputs alternating current signals under the control of a main control platform and sends the alternating current signals to an underwater electric field generated underwater, a multi-channel receiver receives earth voltage reflecting earth information at different depths through an electric field sensor and an underwater dragging detection cable, collects the sending current of the transmitter and transmits the sending current to the main control platform, and then the main control platform receives signals of all channels of the multi-channel receiver to obtain earth electrical parameters reflecting underwater geological conditions, thereby completing the electrical prospecting of fresh water areas.

Although the above patent is improved to some extent in terms of different problems, the following problems are still not solved systematically:

1) the topography of the water bottom is fluctuated: because the fluctuation of the terrain affects the later data result, if the cable system arranged at the water bottom does not correct the elevation coordinates of each electrode of the cable according to the actual terrain, but only defaults that each electrode of the cable is positioned on the same horizontal plane for processing, the data processing result which does not correct the elevation coordinates of the electrodes has larger difference with the result of actually adding the elevation coordinates, and the water bottom geological information cannot be truly and accurately reflected. The cables designed by the prior patent mostly float on the water surface or at the same depth in the water, the height coordinates of electrodes on the cables are obtained due to the difference of the topography fluctuation of the water bottom after a cable system is arranged on the water bottom, and even if the cables are directly sunk to the water bottom for detection, the topography fluctuation of the water bottom is not clearly indicated to be considered and explained, and the height coordinates of the electrodes on the cables are designed to be measured and obtained by sensors and are brought into processing software for carrying out operations such as topographic data processing and the like.

2) Dragging the underwater cable: and after the collection is finished, all the electrodes need to be taken out of the soil medium and then are dragged to move forwards to the next area to be measured by a tugboat to measure. Wherein, the separation problem of each electrode of cable and the submarine soil body needs at first to be solved in dragging of submarine cable line, in addition, only directly drags the cable system at the submarine after separating both, then probably has because submarine foreign matter drags the cable to damage the cable structure or because submarine topography fluctuation leads to the electrode to insert the soil body medium again and can't directly drag the problem that the reality probably appears such as.

3) Underwater positioning of the cable: the position of a cable needs to be positioned during the measurement of the underwater geologic body, the purpose is to determine the actual control length of the cable and the position of the cable during each acquisition, provide actual coordinate positioning data for the cable movement and the cable overlapping laying position at each time, and improve the accuracy of the field cable laying and data acquisition strictly according to the designed measurement line position and area. The problems that the moving position of the cable deviates from the actual position every time, the cable moves every time and the error of the position point is measured in an overlapping mode are solved by carrying out underwater positioning on the cable. The existing cable positioning only installs a positioning system at the head and tail electrodes to obtain the laying position of the cable, but does not consider the initial point coordinate of the overlapped laying section after each movement of the cable, if the laying deviation is large, the accuracy of the result after the data of each section is subjected to combined processing can be influenced, and the accuracy of underwater geologic body detection is reduced.

Disclosure of Invention

In view of the above, the present invention provides a towed underwater electromechanic prospecting system and method, which can solve the above-mentioned shortcomings and problems in underwater electromechanic prospecting. Has better application prospect.

In order to achieve the purpose, the invention adopts the following technical scheme:

a towed underwater geoelectrical detection system comprising: the system comprises an underwater cable, a simple underwater electrode, a water pressure measuring and sensing unit, a cable floating and sinking unit, an underwater GPS (global positioning system), an inflator, an electrical method data acquisition and storage module and a data processing module;

the underwater cable is fixed with the cable floating and sinking unit, and the cable floating and sinking unit is connected with the inflator; the underwater cable is sequentially connected with the electrical method data acquisition and storage module and the data processing module;

a plurality of simple underwater electrodes and a plurality of water pressure measurement sensing units are fixed on the underwater cable; the water pressure measuring and sensing unit and the simple underwater electrode are correspondingly arranged;

the underwater GPS positioning system comprises: a transponder, an onboard transducer and a GPS; the number of the transponders is only three, and the transponders are respectively fixed at the front, middle and tail simple underwater electrodes on the underwater cable; the transponder is wirelessly connected with the onboard transducer; the GPS is fixed on the tug.

Preferably, the underwater cable line is a specially-made special underwater geophysical prospecting cable with sealing, water resistance and strong tensile property, wherein each copper sheet channel on the cable line is designed into a pressing die circular tap (copper ring).

Preferably, the cable buoy unit includes: a plurality of underwater airbags and snorkels;

the underwater airbags are fixed above the simple underwater electrodes in a one-to-one correspondence manner; the underwater airbags are communicated with each other through the vent pipe, and the vent pipe is connected with the inflator. The cable floating and sinking unit has the capability of controlling the cable to float up and down in water and consists of an underwater air bag with good contraction and expansion performance and a communicating pipe. The underwater airbag is arranged right above the simple underwater electrode fixed at each copper ring position on the cable; all the underwater air bags are communicated with each other through the vent pipe, and the sealing performance is good; the cable floating and sinking unit and the underwater cable can be required to be bonded, manufactured and fixed by manufacturers before leaving factories.

Preferably, the method further comprises the following steps: a water pressure display; the water pressure measuring and sensing unit is connected with the water pressure display in a wireless mode.

The water pressure measuring and sensing unit has sealing and waterproof performance; the water pressure measuring and sensing units are fixed beside each copper ring of the underwater cable and used for measuring the water pressure of the depth of each electrode on the underwater cable, further calculating the depth of each electrode at the water bottom and obtaining the topographic relief data of the water bottom; each water pressure measurement sensing unit transmits the water bottom depth data of the simple underwater electrodes obtained by measurement and calculation to a water pressure display on the tugboat through wireless signals; the water pressure display is used for receiving and storing the measurement data transmitted back by each water pressure measurement sensing unit and can display the measurement data in real time.

Preferably, the method further comprises the following steps: positioning the display; the positioning display is arranged on the tug boat; the shipborne transducer is connected with the positioning display.

The underwater GPS positioning system consists of a shipborne GPS, a shipborne energy converter, an underwater transponder and a positioning display; the shipborne GPS and the positioning display are arranged on the ship; the shipborne energy converter is arranged below the water surface near the stern; only three underwater transponders are needed, two of the underwater transponders are respectively fixed on the cables at the head and tail electrodes of the underwater cable, and the other transponder is fixed at the cable position point for moving the cable and overlapping the measurement each time according to the cable overlapping measurement section; the transponder fixed in the middle of the underwater cable can be adjusted and fixed well before the cable works underwater according to the overlapping range of actual needs;

the underwater GPS positioning technology combines GPS positioning and underwater sound positioning, and extends the high-precision positioning capability of the GPS water surface to the underwater by using the underwater sound relative positioning technology, so that the object to be measured can obtain the longitude and latitude coordinates of the object to be measured in the working depth, and the positioning precision can be ensured to be in the same order of magnitude as the GPS water surface positioning precision. The ultra-short baseline (USBL) positioning technology belongs to one of underwater acoustic positioning technologies, and is suitable for working in shallower water areas. In the USBL system, a transponder is installed on an underwater cable line, and a shipborne transducer finishes the attitude positioning of the underwater cable line by measuring the horizontal and vertical angles and the slant distance of the transponder. The underwater GPS positioning technology has the advantages of simple installation, convenient operation, no need of constructing an underwater base line array, high ranging precision and the like.

Positioning data obtained by the measurement of the shipborne transducer is sent to a positioning display through a CAN bus; the positioning display is used for accurately measuring the longitude and latitude coordinates of the head electrode point and the tail electrode point on the cable at each time, the effective measurement length range of the underwater cable collected and laid at each time and the position point overlapped after the cable moves by automatically calculating the underwater positioning data obtained by the measurement of the shipborne GPS and the shipborne transducer, so that the position of the cable system laid at the bottom at each time is effectively controlled on a measuring line in the area to be measured to move and accurately control the overlapped measurement range.

Preferably, according to the underwater actual condition of cable conductor cloth in the submarine, plain type underwater electrode includes: a dorsal fin underwater electrode, a circular arc underwater electrode and a pointed cone underwater electrode.

The simple underwater electrode changes the design style of the existing rod type electrode only suitable for the earth surface, and is designed into a back fin type, an arc shape, a pointed cone type and other simple underwater electrodes which can be selected by various styles according to the actual situation that the underwater cable is arranged at the water bottom, wherein the back fin type and the arc shape electrodes are suitable for soft contact surfaces such as mucky soil layers and the like at the water bottom, and the pointed cone type electrodes are suitable for contact surfaces with larger or harder particles such as sand layers, gravel layers and the like at the water bottom; preferably, the simple underwater electrode is made of copper and other materials with excellent conductivity, is of a solid structure, and can increase the weight of the cable; the simple underwater electrode is fixedly buckled on each copper ring channel of the cable. The simple underwater electrode has the advantages of simple structure, easiness in fixation, low price, good contact coupling effect with underwater soil media and strong applicability.

Preferably, the inflator is a controllable inflator connected to a vent pipe in the cable-sinking unit through a gate valve. The aeration pipe is aerated by controlling the aerator, gas is gathered into each underwater air bag through the aeration pipe, so that the underwater air bags are aerated and expanded, the cable system is separated from a water bottom soil medium to float upwards by buoyancy generated by the expansion of the air bags (wherein, the maximum buoyancy generated after the air bags are aerated needs to enable the cable to float on the water surface integrally), and after the cable moves forwards to the next measurement area along with a ship, the cable is sunk to the water bottom of the area to be measured and is in contact with the water bottom soil medium by deflating the underwater air bags. The controllable inflator is used for inflating and deflating the underwater airbag, so that the cable system can be adjusted to sink to the water bottom, suspend in the water or float on the water surface and other different positions.

Preferably, the inner side of the simple underwater electrode is provided with a plurality of conductive reeds, and each simple underwater electrode is fixed with each copper sheet channel on the underwater cable through the conductive reeds.

Preferably, the position of the transponder at the mid-section underwater electrode on the cable is determined from the overlapping measurement positions of the underwater cable after each movement of the underwater cable at the water bottom.

Preferably, the electrical method data acquisition and storage module comprises a network parallel electrical method instrument; the underwater cable is connected with a data acquisition interface of the network parallel electrical method instrument through a matched navigation plug; the network parallel electrical method instrument has the parallel acquisition function of multiple electrode spacing of a high-density electrical method, and also has the function of continuously and rapidly scanning a ground electric field in parallel, so that the field electrical method data acquisition efficiency and the data quality are greatly improved.

The data processing module is a notebook computer or a desktop computer which is preset with corresponding data processing software; the data processing software includes: network parallel electrical method processing system software, Surfer mapping software, Excel and AGI inversion software.

A detection method of a towed underwater geoelectrical detection system comprises the following steps:

(1) preparation work

On the tug boat, fixing the simple underwater electrode, the transponder, the water pressure measuring and sensing unit and the cable floating and sinking unit on corresponding positions of an underwater cable to form an underwater cable system, and sequentially connecting the underwater cable with the electric method data acquisition and storage module and the data processing module;

the method specifically comprises the following steps: the method comprises the steps of firstly, respectively and fixedly buckling the simple underwater electrodes on copper rings of a cable, then, fixing a transponder at the position of a corresponding electrode in the middle of the cable according to the overlapping measurement range of the actual cable after the cable moves at the bottom every time, inserting a special navigation plug at the tail end of the cable into a data acquisition interface of a network parallel electrical method instrument, connecting a tail end vent pipe of a cable floating and sinking unit with a controllable inflator, fixing a shipborne GPS at the stern, and arranging a shipborne transducer under the surface of the stern water. It should be noted that the cable sinking and floating unit, the water pressure measuring and sensing units fixed beside the copper rings of the cable, and the transponders fixedly mounted at the head and tail electrodes of the cable all can be mounted and fixed at corresponding positions on the underwater cable before the manufacturer leaves the factory.

(2) Placing an underwater cable system at the bottom of a water

The underwater cable system is put into water, the inflator inflates the cable floating and sinking unit, the underwater cable system floats below the water surface, after the tugboat pulls the underwater cable system to reach the position of the area to be measured, the inflator gradually releases the air quantity of the underwater air bag in the cable floating and sinking unit to enable the underwater cable system to gradually sink, in the process, the underwater GPS positioning system can obtain the posture and the position of the underwater cable in real time, the water pressure measuring and sensing unit measures the water depth of each simple underwater electrode, after the underwater cable system reaches the specified line measuring position and sinks into the water bottom, the electrodes are completely contacted with the soil medium at the water bottom, acquiring and storing water bottom topographic data measured by a water pressure measuring and sensing unit at each simple underwater electrode position and longitude and latitude coordinates measured by transponders at three positions including head and tail electrodes and electrodes at an overlapping starting point on an underwater cable;

(3) collecting electrical data of water bottom geology

The method comprises the steps of setting parameters of an electrical method data acquisition and storage module, supplying power after the setting is finished, sequentially generating current into a water bottom soil body medium through simple underwater electrodes on an underwater cable line to form an electric field, and acquiring potential to acquire water bottom geological electrical data in a monitoring section;

the method specifically comprises the following steps: firstly, setting instrument acquisition parameters, such as constant current time, sampling time interval, power supply voltage, an acquisition mode, a power supply mode and the like; after the parameters of the instrument are set, the instrument is powered, all copper sheets on the underwater cable sequentially generate current into a water bottom soil body medium through the electrodes to form an electric field, potential acquisition is carried out on all the other electrodes, and finally water bottom geological electrical data in the monitoring section are obtained. The network parallel electrical method instrument is divided into two different acquisition modes of an AM method (single-point power supply field) and an ABM method (dipole power supply field), wherein the AM method acquisition mode can be used for simultaneously acquiring electrical method data of two-stage and three-stage device types (infinite electrodes are required to be arranged), and the ABM method acquisition mode can be used for simultaneously acquiring electrical method data of three device types including Wenna quadrupole, Wenna dipole and Wenna differential (infinite electrodes are not required to be arranged). In general, the constant current time and the sampling time interval of the AM acquisition mode are respectively set as follows: 0.5s, 50 ms; the constant current time and the sampling time interval of the ABM method acquisition mode are respectively set as follows: 0.2s, 100 ms.

(4) Drag to next detection position and repeat the above steps

After the data acquisition is finished, the aerator inflates the vent pipe, so that the underwater cable system floats upwards along with the expansion of the underwater airbag, the simple underwater electrode is separated from the underwater soil medium and floats upwards along with the whole underwater cable system, the tug pulls the whole underwater cable system to move towards the direction of the next detection section and reaches a designated area, the first electrode on the cable is controlled to be at the starting point of the overlapping section by an underwater GPS positioning system, namely, the position coordinate point of the middle transponder during the last acquisition, and then the air-bleeding operation is gradually carried out on the underwater air bag, so that the whole underwater cable system is sunk to the water bottom, after the underwater cable system is completely sunk to the water bottom and the simple underwater electrode is inserted into the soil medium of the water bottom, repeating the data acquisition operation and the operation of moving and dragging the underwater cable system to the next detection area until the data acquisition in the whole test area is finished;

(5) data processing stage

The data processing stage comprises preprocessing, data inversion processing and data result mapping;

pretreatment: opening original data by using network parallel electrical method processing system software; checking and modifying the coordinates of the simple underwater electrode, wherein the operation comprises the steps of converting, sorting and combining coordinate data in Excel software, adding topographic data and exporting files; putting the exported file data with the terrain into a network parallel electrical method processing system, and simultaneously merging and unifying the original data of each section; then, decoding conventional data, outputting an apparent resistivity data file and an AGI inversion format data file, wherein the acquired data needs to be checked before decoding the conventional data, and if abnormal jumping points which do not accord with actual conditions exist in the data, the abnormal jumping points need to be removed;

data inversion processing: according to the field geological condition, an appropriate inversion method is selected by combining the quality of actual data acquisition, so that the best result is obtained by inversion, three inversion methods are provided in AGI inversion software, wherein the inversion methods comprise damped least square inversion, smooth model inversion and anti-noise inversion, and the main flow is as follows: initial setting of inversion parameters, selection of a proper inversion method, setting of data noise standard, inversion iteration times, rounding coefficient and maximum root mean square error; opening an AGI inversion format data file, performing joint inversion to obtain an electrical data profile of a complete water bottom geologic body on the whole measuring line, and after the inversion is finished, exporting an inversion resistivity data file in a dat format;

data results are plotted: respectively mapping the apparent resistivity data and the inversion resistivity data derived by the AGI inversion software by using Surfer mapping software, wherein the mapping processing comprises the following steps: opening data in a dat format in Surfer software, gridding the data, selecting a gridding method, gridding the data, filtering abnormal data, performing basic processing flow, selecting a filter according to actual needs to filter the data, performing whitening processing, and finally obtaining a water bottom geological electrical result map with terrain through the processing flow;

(6) analysis of electrical results of underwater geology

According to the actual water bottom detection purpose and the detection result diagram, the resistivity and distribution rule characteristics of different areas in the electrical property result diagram are explained by combining the existing field geological data, and the water bottom geological information is comprehensively analyzed and judged.

The towed underwater geology electrical detection system and the towed underwater geology electrical detection method provided by the invention have wide application range, can quickly detect underwater geology of shallow sea water areas, rivers, lakes, reservoirs and the like with high precision and high resolution, and specifically can detect underwater geology of shallow sea water areas, rivers, lakes, reservoirs and the like, and comprise the following steps: the method is characterized in that the method comprises the following steps of accurately exploring underwater geology such as the thickness of an underwater silt layer, the depth of an underwater foundation rock surface, the structural integrity of an underwater rock body, the stability of underwater foundation engineering, the intrusion degree and range of seawater, the occurrence position of underwater shallow layer gas, karst cavities, fissure water seepage channels, the spatial distribution of a goaf below a water body in the field of coal mines, the height of a fracture zone of an overlying rock body of a working surface and the like, and obtaining accurate and detailed geological information of an underwater geological target body.

According to the technical scheme, the invention discloses and provides a towed underwater geologic electrical method detection system and method, and compared with the prior art, the towed underwater geologic electrical method detection system and method have the beneficial effects that:

1. the designed simple underwater electrode overcomes the defects of the traditional rod type electrode sinking to the water bottom or floating on the water surface for detecting, improves the contact coupling effect of the underwater cable and the underwater soil medium, and has the advantages of simple structure, convenience in fixing, detachability, strong applicability and the like. The cable system of the fixed simple underwater electrode has deeper detection depth after sinking to the water bottom, higher data resolution and more reliable data result.

2. The actual problem that the water area cable system does not consider the fluctuation of the water bottom topography is solved, the water depth of each electrode is measured through the water pressure measuring and sensing unit, the actual water bottom topography coordinates of each electrode are brought into data processing software for processing, the result is more real and reliable, and the circle of the position of the abnormal body is more accurate.

3. The problems that the position of an underwater cable on the site cannot be accurately determined, the actual underwater effective measurement length of the cable is unknown, the deviation of a cable moving overlapping position point is large and the like are solved, the actual position of the cable and the starting point coordinate of the overlapping position of the next station after the cable moves can be accurately positioned in real time through an underwater GPS positioning system, the posture of the cable system at the water bottom can be mastered constantly, and the laying and moving of the underwater cable are controlled to be carried out on a measurement line all the time.

4. The controllable inflator is used for inflating and deflating the underwater air bag, the buoyancy of the air bag is changed to drive the cable system to sink to the water bottom or float up and down in the water, and the ship towing cable moves towards a next measuring area, so that the problem that the towing cable system is arranged at the water bottom to ensure that the simple underwater electrode is separated and moved after being inserted into the medium contact coupling of the water bottom soil body is effectively solved.

5. The network parallel electrical method instrument has the characteristics of a conventional high-density electrical method instrument and has the advantage of continuously and quickly scanning a ground electric field in parallel, so that the network parallel electrical method instrument and the intelligent integrated towed type underwater geological electrical method detection system are popularized and applied to the field of water area electrical method detection, and quick and high-resolution scanning of an underwater geological structure can be realized.

The towed underwater geology electrical method detection system and method provided by the invention systematically solve the problems and technical problems existing in the current water area electrical method detection, and have wide application prospects.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic view of the overall structure of a towed underwater geoelectrical detection system according to the present invention;

FIG. 2 is a schematic diagram of the whole system floating after the cable floating and sinking unit is inflated;

FIG. 3 is a schematic diagram of the movement of a system for towing underwater cables by a tug according to the present invention;

FIG. 4 is a schematic view of the arrangement of the submarine cable system provided by the present invention after reaching the next measurement section;

FIG. 5 is a front view of a simplified underwater electrode of the three design types provided by the present invention;

FIG. 6 is a side view of a simplified underwater electrode provided by the present invention;

FIG. 7 is a schematic diagram of the operation of the water pressure measuring module provided by the present invention;

FIG. 8 is a schematic diagram of the operation of an underwater GPS positioning system provided by the present invention;

FIG. 9 is a flow chart of the field operation of the towed underwater geoelectrical detection system provided by the present invention;

FIG. 10 is an inverted resistivity profile of a conventional water-surface electrical method for detection at the surface;

FIG. 11 is an inversion resistivity profile of a conventional water-surface electrical method at 2.5m below the water surface for detection;

FIG. 12 is an inversion resistivity profile of the towed underwater geoelectrical detection system of the present invention positioned on the surface of the underwater soil medium for detection.

In the figure, 1-underwater transponder, 2-simple underwater electrode, 3-underwater air bag, 4-water pressure measurement sensing unit, 5-voltage reference electrode N pole, 6-cable, 7-vent pipe, 8-ship transducer, 9-GPS, 10-CAN bus, 11-tug, 12-controllable inflator, 13-network parallel electrical method instrument, 14-positioning display, 15-water pressure display and 16-conductive reed.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a schematic view of an overall structure of a towed underwater geoelectrical detection system provided by the present invention, which specifically includes: the system comprises an underwater cable 6, a simple underwater electrode 2, a water pressure measuring and sensing unit 4, a cable floating and sinking unit, an underwater GPS (global positioning system), an inflator 12, an electrical method data acquisition and storage module and a data processing module;

the underwater cable 6 is fixed with a cable floating and sinking unit which is connected with an inflator 12; the underwater cable 6 is sequentially connected with an electrical method data acquisition and storage module and a data processing module;

a plurality of simple underwater electrodes 2 and a plurality of water pressure measuring and sensing units 4 are fixed on the underwater cable 6; the water pressure measuring and sensing unit 4 is arranged corresponding to the simple underwater electrode 2;

an underwater GPS positioning system comprising: transponder 1, onboard transducer 8 and GPS 9; only 3 transponders 1 are needed and are respectively fixed at the front, middle and tail simple underwater electrodes 2 on the underwater cable 6; the transponder 1 is wirelessly connected with the shipborne transducer 8; the GPS9 is fixed to the tug 11.

During specific implementation, the underwater cable 6 is fixedly adhered to the cable floating and sinking unit, the underwater cable 6 is connected with a data interface of an electrical method data acquisition and storage module through an aerial plug, and specifically, the electrical method data acquisition and storage module is a network parallel electrical method instrument 13; the network parallel electrical method instrument 13 is connected with the data processing module.

The simple underwater electrode 2 is fixed with each copper sheet channel on the underwater cable 6; the water pressure measuring and sensing unit 4 is fixedly arranged on an underwater cable 6 beside the simple underwater electrode 2; the front, middle and tail electrodes on the underwater cable 6 are fixed with the transponder 1 in the underwater GPS positioning system; a shipborne transducer 8 in the underwater GPS positioning system is hung at the tail part of a tug 11 and is arranged below the water surface; a GPS9 in the underwater GPS positioning system is fixed at the tail of the tug 11; the network parallel electrical method instrument 13, the data processing module, the inflator 12, the water pressure display 15, the GPS9 and the matched positioning display 14 are arranged on the tug; wherein, the water pressure measuring and sensing unit 4 is connected with the water pressure display 15 in a wireless mode; the onboard transducer 8 is connected to a positioning display 14. The underwater cable 6, the simple underwater electrode 2, the transponder 1, the water pressure measuring and sensing unit 4 and the cable floating and sinking unit are integrated and then are placed under the water.

In order to further optimize the above technical solution, the cable floating and sinking unit includes: a plurality of underwater airbags 3 and snorkels 7; the underwater airbags 3 are fixed above the simple underwater electrodes 2 in a one-to-one correspondence manner; the underwater air bags 3 are communicated through vent pipes 7, and the vent pipes 7 are connected with inflators 12.

According to 6 laying subaqueous actual conditions of cable conductor under water, plain type is electrode 2 under water includes: fig. 5 shows a dorsal fin underwater electrode, an arc underwater electrode, and a pointed underwater electrode, where fig. 5a shows the dorsal fin underwater electrode, fig. 5b shows the arc underwater electrode, and fig. 5c shows the pointed underwater electrode. The back fin-shaped and arc-shaped electrodes are suitable for soft contact surfaces such as mucky soil layers and the like on the water bottom, and the pointed cone-shaped electrodes are suitable for contact surfaces with larger or harder particles such as sand layers, gravel layers and the like on the water bottom. Referring to fig. 6, the simple underwater electrode has a conductive reed 16, wherein the conductive reed 16 is a conductive reed with certain deformation and clamping fixing ability capable of clamping and fixing the simple underwater electrode 2 on a copper sheet of the cable, that is, the simple underwater electrode 2 is fixed with each copper sheet channel on the underwater cable 6 through the conductive reed 16.

Preferably, the inflator 12 is a controllable inflator 12 connected to the vent pipe 7 in the cable heave unit through a gate valve. The aeration pipe is aerated by controlling the aerator, gas is gathered into each underwater air bag through the aeration pipe, so that the underwater air bags are aerated and expanded, the cable system is separated from a water bottom soil medium to float upwards by buoyancy generated by the expansion of the air bags (wherein, the maximum buoyancy generated after the air bags are aerated needs to enable the cable to float on the water surface integrally), and after the cable moves forwards to the next measurement area along with a ship, the cable is sunk to the water bottom of the area to be measured and is in contact with the water bottom soil medium by deflating the underwater air bags. The controllable inflator is used for inflating and deflating the underwater airbag, so that the cable system can be adjusted to sink to the water bottom, suspend in the water or float on the water surface and other different positions.

Referring to fig. 7, fig. 7 is a schematic working diagram of the water pressure measuring module provided by the present invention, wherein the water pressure measuring sensing unit 4 is installed and fixed at each copper sheet position on the cable 6, and is used for measuring the water depth of each simple underwater electrode 2 to obtain the water bottom undulation data, and by operating the water pressure display 15, the water pressure measuring sensing unit 4 is controlled in real time to obtain the water bottom undulation data and wirelessly transmit the data to the water pressure display 15.

Fig. 8 is a working schematic diagram of the underwater GPS positioning system provided by the present invention. Specifically, the underwater GPS positioning system consists of a ship-borne GPS9, a ship-borne transducer 8, an underwater transponder 1 and a positioning display 14; the onboard GPS9 and the positioning display 14 are located onboard the vessel; the shipborne transducer 8 is arranged below the water surface near the stern; the underwater transponders 1 are only three, two of the underwater transponders are respectively fixed on the cables at the head and tail electrodes of the underwater cable, and the other transponder is fixed at the cable position point of each cable moving and overlapping measurement according to the cable overlapping measurement section; the transponder fixed in the middle of the underwater cable can be adjusted and fixed well before the underwater operation of the cable according to the overlapping range of actual needs. The system is suitable for accurately positioning the attitude and the position of the underwater cable and an initial overlapping measurement point, and provides accurate positioning data for the movement and the determination of the position of the cable on site each time, thereby providing more reliable guarantee for the combination processing of later data.

In the overall structure of the towed submarine electrical prospecting system, the distance and the number of the annular copper sheets designed according to a certain electrode distance on a cable wire and the position of a voltage reference electrode N pole (the annular copper sheets) can be customized by a manufacturer according to actual needs, the parts between a vent pipe and an underwater airbag on the upper part of the cable wire, the parts between the vent pipe, the underwater airbag and the cable wire, all water pressure measuring sensing units and transponders at the head and the tail electrodes of the cable wire are processed and integrated into a whole by the manufacturer according to customer requirements before leaving factory, the parts and the structure do not need to be fixed by field workers, the field workers only need to fix one underwater transponder at the corresponding position on the cable wire and clamp and fix the simple underwater electrodes at the annular copper sheets on the cable wire to complete the field installation work of the underwater cable system, after the installation of the underwater cable system is completed, the breather pipe is communicated with the controllable inflator, the cable navigation plug is connected with the network parallel electrical method instrument interface, and the shipborne transducer is connected to the positioning display interface through the CAN bus, namely the connection and fixation work of the whole system is completed.

The towed underwater geology electrical detection system designed by the invention has wide application range, can quickly detect underwater geology of shallow sea water areas, rivers, lakes, reservoirs and the like with high precision and high resolution, and specifically can detect the underwater geology of the shallow sea water areas, the rivers, the lakes, the reservoirs and the like with high precision and high resolution, and comprises the following steps: the method is characterized in that the method comprises the following steps of accurately exploring underwater geology such as the thickness of an underwater silt layer, the depth of an underwater foundation rock surface, the structural integrity of an underwater rock body, the stability of underwater foundation engineering, the intrusion degree and range of seawater, the occurrence position of underwater shallow layer gas, karst cavities, fracture leakage channels, the spatial distribution of a goaf below a water body in the field of coal mines, the height of a fracture zone of an overlying rock body of a working surface and the like, and obtaining accurate and detailed geological information of an underwater geological target body. According to the depth and the size of the different detection target bodies, the electrode distance and the number of electrode channels of the cable can be flexibly designed. For example, for the detection of a shallow geologic body structure at 10m below the water bottom, the cable can be designed to have an electrode distance of 1m, the number of electrode channels of 32, or the electrode distance of 1m, the number of electrode channels of 64, and the like; aiming at the detection of a shallow geologic body structure at 50m below the water bottom, the cable can be designed to have the electrode distance of 2.5m and 64 electrode channels; and aiming at geological body abnormity detection such as goaf below a water body with the depth of 150m at the water bottom, overlying rock mass damage of a coal mining working surface and the like, cables need to be designed into 5m electrode distance, 64 electrode channels or 5m electrode distance, 96 electrode channels and the like. Compared with the existing water area cable system, the intelligent integrated cable system directly arranges the cable system at the water bottom, so that the simple underwater electrodes are in direct contact and good coupling with the water bottom soil medium, and the characteristics of measuring the water bottom relief topography at each electrode and the like are achieved.

The electrical method data acquisition and storage module used by the invention comprises a network parallel electrical method instrument 13; the underwater cable 6 is connected with a data acquisition interface of the network parallel electrical method instrument 13 through a matched aviation plug;

The parallel electrical method acquisition system has the parallel acquisition function of multiple electrode spacing of a high-density electrical method, and also has the function of continuously and rapidly scanning a ground electric field in parallel, so that the electrical method data acquisition efficiency and the data quality are greatly improved. The electric method collection instrument has the advantages that the power supply voltage of 0, 24, 48, 72 and 96v which are totally five gears can be selected, reasonable selection can be carried out on the site according to the conditions of the depth of a detected target, the length of a cable and the like, partial electrodes on the cable can be automatically set and controlled according to the site requirement to carry out data collection, and the flexibility is high. The instrument is divided into an AM acquisition mode and an ABM acquisition mode, wherein the AM acquisition mode can simultaneously acquire electrical data of two-stage and three-stage device types (infinite electrodes need to be arranged), and the ABM acquisition mode can simultaneously acquire electrical data of three device types, namely Wennal quadrupole, Wennal dipole and Wennal differential (infinite electrodes do not need to be arranged). In general, the constant current time and the sampling time interval of the AM acquisition mode are respectively set as follows: 0.5s, 50 ms; the constant current time and the sampling time interval of the ABM method acquisition mode are respectively set as follows: 0.2s, 100 ms. Taking the number of the electrode tracks on the cable as 64 tracks as an example, the acquisition time required by the acquisition mode of the AM method is only 96s, and the acquisition time required by the acquisition mode of the ABM method is 1080 s. The data volume acquired by the ABM method is large, but compared with the AM method, the time required by field acquisition is too long, and the requirement of field rapid detection is difficult to meet, so that the AM method is more suitable to be used as a field electrical method data acquisition mode on the basis of ensuring the data reliability. And moreover, the AM method is adopted on the site for data acquisition, the requirement of rapid electric field scanning is met, and meanwhile, the AM method data can still be deduced into ABM method data through post-processing, so that more electric method device data can be provided on the basis of efficient and rapid acquisition.

In addition, referring to fig. 1 to 4 and fig. 9, the embodiment of the invention also discloses a detection method of a towed underwater geoelectrical detection system, which comprises the following steps:

(1) preparation work

referring to the attached drawing 1, the number of electrode channels on the cable in fig. 1 is 8, the electrodes from 1# to 8# are sequentially arranged from left to right, the simple underwater electrodes 2 are respectively and fixedly buckled on the copper rings of the cable 6, then a transponder 1 is fixed at the position of the corresponding electrode (electrode # 6) in the middle of the cable 6 according to the overlapping measurement range of the actual cable after moving at the water bottom each time, a special navigation plug at the tail end of the cable 6 is inserted into a data acquisition interface of a network parallel electrical method instrument 13, a tail end vent pipe 7 of a cable floating and sinking unit is connected with a controllable inflator 12, a shipborne GPS9 is fixed at the stern of the ship, and the shipborne transducer 8 is arranged under the water surface of the stern of the ship. It should be noted that, the water pressure measurement sensing unit 4 fixed on the cable 6 beside each copper ring of the cable, and the transponder 1 respectively and fixedly mounted at the head (1# electrode) and tail (8# electrode) electrodes of the cable 6 are fixedly mounted by manufacturers before leaving the factory, the underwater airbag and the vent pipe are communicated and adhered to the upper part of the cable 6, and the adhesion and fixation of the cable sinking and floating unit are completed by the manufacturers.

(2) Placing an underwater cable system at the bottom of a water

The underwater cable system is put into water, the inflator inflates the cable floating and sinking unit, the underwater cable system floats below the water surface, after the tugboat pulls the underwater cable system to reach the position of the area to be measured, the inflator gradually releases the air quantity of the underwater air bag in the cable floating and sinking unit to enable the underwater cable system to gradually sink, in the process, the underwater GPS positioning system can obtain the posture and the position of the underwater cable in real time, the water pressure measurement sensing unit measures the water depth of each simple underwater electrode, after the underwater cable system reaches the specified line measurement position and the electrodes are completely contacted with the underwater soil medium, acquiring and storing water bottom topographic data measured by a water pressure measuring and sensing unit at each simple underwater electrode position and longitude and latitude coordinates measured by transponders at three positions including head and tail electrodes and electrodes at an overlapping starting point on an underwater cable;

the method specifically comprises the following steps: after the debugging of each unit module is completed, the underwater cable system is put into water, at the moment, the inflator 12 inflates the underwater airbag 3 through the vent pipe 7, the underwater cable system floats below the water surface, the tug 11 pulls the underwater cable system to reach the measuring line position of the area to be measured, the air quantity of the underwater airbag 3 is controlled and gradually released through the controllable inflator 12, so that the underwater cable system gradually sinks to the water bottom through self weight, in the process, the data obtained by the underwater GPS positioning system can be displayed on the positioning display 14 in real time to obtain the posture and the position of a cable, the water pressure measuring and sensing unit 4 can measure the water depth of each electrode in real time, and after the underwater cable system reaches the appointed measuring line position and the electrode is completely contacted with the soil medium of the water bottom, the water bottom topographic data measured by the water pressure measuring and sensing unit 4 at each electrode position can be obtained and stored, and the topographic relief data is wirelessly transmitted and stored in a water pressure display 15 on the tug 11, and longitude and latitude coordinates of three positions of the head and tail electrodes and the electrodes at the overlapped starting point on the underwater cable are obtained. The overall arrangement of the underwater cable system after sinking into the water bottom and the electrodes coupled to the soil medium on the water bottom is shown in fig. 1.

(3) Collecting electrical data of water bottom geology

Parameter setting is carried out on the electrical method data acquisition and storage module, power supply is carried out after the setting is finished, each copper sheet on the underwater cable line sequentially generates current into a water bottom soil body medium through a simple underwater electrode to form an electric field, potential acquisition is carried out, and water bottom geological electrical data in a monitoring section are obtained;

the method specifically comprises the following steps: firstly, setting instrument parameters such as constant current time, sampling time interval, power supply voltage, an acquisition mode, a power supply mode and the like; after the parameters of the instrument are set, the instrument is powered, all copper sheets on the underwater cable 6 sequentially generate current into the underwater soil medium through the electrodes 2 to form an electric field, and all other electrodes are used for potential acquisition to finally obtain the underwater geological electrical data in the monitoring section. The network parallel electrical method instrument is divided into two different acquisition modes of an AM method (single-point power supply field) and an ABM method (dipole power supply field), wherein the AM method acquisition mode can be used for simultaneously acquiring electrical method data of two-stage and three-stage device types (infinite electrodes are required to be arranged), and the ABM method acquisition mode can be used for simultaneously acquiring electrical method data of three device types including Wenna quadrupole, Wenna dipole and Wenna differential (infinite electrodes are not required to be arranged). In general, the constant current time and the sampling time interval of the AM acquisition mode are respectively set as follows: 0.5s, 50 ms; the constant current time and the sampling time interval of the ABM method acquisition mode are respectively set as follows: 0.2s, 100 ms.

(4) Drag to next detection position and repeat the above steps

After the data acquisition is finished, the inflator inflates the vent pipe, so that the underwater cable system floats upwards along with the expansion of the underwater airbag, meanwhile, the simple underwater electrode is also driven to separate from the underwater soil medium and float upwards along with the whole underwater cable system, the tugboat pulls the whole underwater cable system to move towards the direction of the next detection section and then reaches the designated area, the first electrode on the cable is controlled to be at the starting point of the overlapping section by an underwater GPS positioning system, namely, the position coordinate point of the middle transponder during the last acquisition, and then the air-bleeding operation is gradually carried out on the underwater air bag, so that the whole underwater cable system is sunk to the water bottom, after the underwater cable system is completely sunk to the water bottom and the simple underwater electrode is inserted into the soil medium of the water bottom, repeating the data acquisition operation and the operation of moving and dragging the underwater cable system to the next test area until the data acquisition in the whole detection area is finished;

the method specifically comprises the following steps: after the data acquisition is finished, the controllable inflator 12 inflates the vent pipe 7 to enable the underwater air bag 3 on the cable 6 to expand, the simple underwater electrode 2 is separated from the underwater soil medium and floats upwards along with the whole underwater cable system after being subjected to the upwards buoyancy force gradually increased by the air bag 3, the tugboat 11 drags the whole underwater cable system to move towards the direction of a next detection section and reaches a designated area, after the cable 1# electrode is controlled at the starting point of the overlapping section (namely the measurement repetition starting point where the 6# electrode is located in figure 2) through the underwater GPS positioning system, the air bag 3 is gradually deflated, so that the whole cable system gradually sinks into the designated area of the water bottom, after the cable system completely sinks into the water bottom and the simple underwater electrode is inserted into the soil medium of the water bottom, and repeating the data acquisition operation and moving the dragging cable system to the next test area. See fig. 3 and fig. 4 for details.

(5) Data processing stage

the pretreatment process comprises the following steps: opening raw data using a network parallel electrical processing system (WBD Pro); checking and modifying the electrode coordinates, wherein the operation comprises the steps of converting, arranging and combining coordinate data in Excel software, adding topographic data, exporting files and the like; putting the exported file data with the terrain into a WBD Pro processing system, and simultaneously merging and unifying the original data of each section; and then performing conventional data decompiling, outputting a apparent resistivity data file (dat format) and outputting an AGI inversion format data file (urf format), wherein the acquired data needs to be checked before performing conventional data decompiling, and if abnormal jumping points which do not accord with the actual situation exist in the data, the abnormal jumping points need to be removed, so that the influence on real data caused by later software computing and inversion is reduced, and the quality of the data is improved.

The data inversion processing flow and the AGI inversion software provide three inversion methods, wherein the inversion method comprises damped least square inversion, smooth model inversion and anti-noise inversion, and a proper inversion method can be selected according to field geological conditions and the quality of actual data acquisition during inversion processing so that the optimal result can be obtained through inversion. The main process is as follows: initial setting of inversion parameters, selection of a proper inversion method, setting of parameters such as data noise standard, inversion iteration times, rounding coefficient, maximum root mean square error and the like. And opening a urf format file to be inverted, performing joint inversion after the setting is completed, obtaining an electrical data profile of the complete water bottom geologic body on the whole measuring line, and exporting an inversion resistivity data file in a dat format after the inversion is finished.

And (4) mapping the data result, and respectively mapping the apparent resistivity data and the inversion resistivity data derived by the AGI inversion software by using Surfer mapping software. Which comprises the following steps: opening data in a dat format in Surfer software, gridding the data, selecting a gridding method, gridding the data, filtering abnormal data, and selecting a filter to filter and whiten the data according to actual needs, and finally obtaining a water bottom geological electrical result map with terrain through the processing flows.

(7) Analysis of electrical results of underwater geology

The towed underwater geology electrical method detection system and the towed underwater geology electrical method detection method which are designed by the invention have wide application range, can quickly detect underwater geology of shallow sea water areas, rivers, lakes, reservoirs and the like with high precision and high resolution, and specifically can detect the underwater geology of the shallow sea water areas, rivers, lakes, reservoirs and the like, and comprise the following steps: the method is characterized in that the method comprises the following steps of accurately exploring underwater geology such as the thickness of an underwater silt layer, the depth of an underwater foundation rock surface, the structural integrity of an underwater rock body, the stability of underwater foundation engineering, the intrusion degree and range of seawater, the occurrence position of underwater shallow layer gas, karst cavities, fissure water seepage channels, the spatial distribution of a goaf below a water body in the field of coal mines, the height of a fracture zone of an overlying rock body of a working surface and the like, and obtaining accurate and detailed geological information of an underwater geological target body. According to the actual water bottom detection purpose and the detection result diagram, the resistivity and distribution rule characteristics of different areas in the electrical property result diagram are explained by combining the existing field geological data, and the water bottom geological information is comprehensively analyzed and judged.

The invention specifically provides and designs the intelligent underwater geological exploration dragging type cable system. Compared with other inventions which lay the cable on the water surface or in water, the invention directly lays the cable system on the water bottom, directly contacts and couples each electrode on the cable with soil body media such as a water bottom sludge layer and the like, simultaneously measures the water depth of each electrode through the water pressure measuring module to obtain real topographic data of the water bottom, brings the coordinates of each electrode into data processing software to carry out a topographic apparent resistivity map and a topographic resistivity inversion, obviously improves the precision and the reliability of field detection data, enables the data result to better accord with the actual situation, simultaneously increases the effective detection depth of the cable system to the water bottom geologic body, and accurately measures the longitude and latitude coordinates of the head and tail electrode points on the cable each time, the effective measurement length range of the cable which is collected and laid each time and the overlapped position point after the cable moves through the underwater GPS positioning system, the cable system is effectively controlled to move and overlap the measurement line in the region to be measured at each time when the cable system is arranged at the underwater position, and finally the original electrical data collected after each moving arrangement are combined and then processed in a combined mode, so that the electrical data profile of the complete underwater geologic body on the whole measurement line can be obtained.

The invention designs the cable system according to the actual problems and requirements on site, and designs the structure of the cable system, lays the cable system on site, collects the depth of the water bottom of the electrode and the topographic data, determines the longitude and latitude coordinates of the head and tail electrodes of the measuring line and the overlapped electrode points, sets the parameters of the instrument on site, collects the data, after the acquisition is finished, the external controllable inflator inflates each underwater airbag through the vent pipe to enable the whole cable system to float upwards (the floating position is controllable), after the ship body moves to the next measurement section, the 1# electrode on the cable is controlled above the overlapping point, the airbag deflates to enable the cable system to slowly sink to the area to be measured, in the process, the cable needs to be controlled and properly adjusted in the measurement section, the error is reduced, the steps are repeated to conduct data acquisition, and the like.

The invention solves the problem that the cable system is arranged at the water bottom and then the electrode is directly contacted and coupled with the soil body, the traditional rod type electrode only suitable for the ground is not required to be designed and installed, the design structure is complicated, and the water area electrode which is complicated to arrange is arranged on site, compared with the cable which floats on the water surface and is used for detection, the invention has the obvious advantages of more reliable detection data quality, more accurate data result, deeper detection depth and the like; the water area cable system solves the actual problem that the water bottom topography fluctuation is not considered in the water area cable system of the prior invention, the depth of the electrodes is measured through the water pressure measurement sensing unit, the actual water bottom topography coordinates of each electrode are brought into the data processing software for processing, and the result is more real and reliable; the problems that the position of an underwater cable on site cannot be accurately determined, the actual effective measurement length of the cable is unknown, the deviation of a cable movement overlapping position point is large and the like are solved, the actual position of the cable and the overlapping position point of the next station after the cable moves are accurately positioned through an underwater GPS positioning system, and the posture and the movement of the underwater cable are constantly controlled to be always on a survey line; the problem of how to remove after drag formula cable system lays and makes plain type underwater electrode and underwater medium contact coupling in the bottom is solved, through aerifing the gasbag under water, drive cable system come-up back, move to next measuring area through the hull drag cable.

It should be noted that the cable system designed by the invention mainly sinks to the water bottom to enable the simple underwater electrode to be directly contacted and coupled with soil media such as a silt layer with undulating topography at the water bottom for detection, so as to improve the precision and the exploration depth of exploration data, but the cable system is not limited to be only used for geological detection at the water bottom, the invention uses an external controllable aerator to inflate an underwater airbag, so that the whole cable system can float in the water and any position of the water surface for detection, and uses an underwater GPS positioning system and a water pressure measurement sensing unit to obtain accurate data such as the depth and the position of the cable system in the water, so that in the process of detecting the water bottom geology on site, if a plurality of foreign matters which influence the arrangement of the cable system exist at the water bottom of certain areas and interfere with the cable system, when the cable system is not convenient to sink to the water bottom, the cable system can float in water or any position of the water surface in the above mode, and then field data are collected, it needs to be explained that the depth of each electrode when the cable system floats in water does not need to be controlled at the same depth, the water depth of each electrode can be obtained in real time through the water pressure measuring module at each electrode position, and electrode coordinate data with electrode elevation can be brought into processing software for processing in the data processing process. Therefore, the invention can timely adjust the cable system to sink at the water bottom or float in the water or on the water surface according to different geological conditions, terrain complex conditions or external interference conditions and the like at the water bottom, so the invention has stronger field applicability, meets the requirement of directly detecting the water bottom geology while simultaneously giving consideration to the design and has the capability of quickly scanning and detecting at any depth of the water or the water surface.

In order to compare and verify that the detection of the technical scheme provided by the invention is more accurate and better in effect than the current water area electrical method detection, a field contrast detection experiment is carried out in a certain river channel. Fig. 10 and 11 are resistivity profile diagrams inverted from detection results obtained by respectively positioning a cable on the water surface and 2.5m below the water surface by using a conventional water area electrical method detection system, and fig. 12 is a resistivity profile diagram inverted from detection results obtained by positioning a towed water bottom geological electrical method detection system provided by the invention on the surface of a water bottom soil medium. Wherein, the electrode spacing on the cable conductor that three section diagrams used all is 1m, the electrode channel number all is 64, 16 electrodes of overlapping between the survey line all use the parallel electrical method appearance of network to gather the on-the-spot underwater electrical data, wherein the instrument supply voltage all is 72V, all carries out AM method data acquisition.

Analyzing the graph 10, it can be found that, because the cable system is arranged on the water surface, the electric field generated in the test area after the instrument is powered on is mainly distributed in the water body due to the low-resistance shielding effect of the water body, and the electric field entering the inside of the water bottom geologic body is weaker, which leads to that the electric data of the water bottom geologic body cannot be effectively obtained.

The analysis of the figure 11 shows that the detection result of the cable system placed in the depth of 2.5m below the water surface is better than that of the cable system placed on the water surface, the position of the underwater geological abnormal body can be better defined, the dark color area in the figure is underwater bedrock, the white color area is the distribution position of soil body media such as silt, the white low-resistance area exists in the bedrock with the depth of 8-16 m in the range of 55-80 m in the transverse direction, the integrity of the bedrock in the area is probably poor through analysis, and long-term water flow erosion causes the position to be filled with a large amount of soil body media such as silt.

In order to compare the difference of the effect and the accuracy between the detection of the invention and the two detections, the towed submarine geologic prospecting system is adopted in the same test area, the simple underwater electrode is well coupled with the submarine medium due to the self weight and the weight of the cable system, and then the on-site detection is carried out, and the cable system is arranged on the submarine interface, and the submarine has certain topographic relief, so the effective detection length in the horizontal direction is slightly shorter than the two methods. After the acquired data are correspondingly processed, obtaining an inversion resistivity profile diagram with the underwater topography as shown in figure 12, clearly distinguishing the thickness of underwater silt layers at different positions and the position of an interface of the underwater bedrock from the diagram, wherein a white area on the diagram is the distribution condition of soil media such as the underwater silt layers, a dark area is the underwater bedrock media, and observing figure 12, a low-resistance area similar to a notch is arranged at a bedrock surface at the position of 50-55 m in the horizontal direction, a low-resistance area within the range of 9-15 m in the longitudinal direction and 45-75 m in the horizontal direction is arranged below the notch, the low-resistance area is communicated, the resistivity of the area is basically 5-20 omega m, the resistivity of the low-resistance area is close to that of the silt layer at the upper part of the bedrock, and the analysis shows that the stability and the integrity of the underwater bedrock is poor, and the low-resistance area part in the bedrock is filled with a large amount of water, and the bedrock above the low-resistance area is in a suspended state, so that the stability and the safety of the later engineering structure can be seriously influenced if pile bodies or other engineering construction is carried out at the position under the condition that the underwater geology of the area is not effectively explored. In order to verify the accuracy of the detection result of the system, the field drilling crew drills at two positions of 55m and 70m in the horizontal direction of the test area respectively for verification, and the results are basically consistent and the field detection result is accurate and reliable according to the comparison between the drilling result and the figure 12. The results of the two detection modes are compared with the detection results of the system disclosed by the invention, and the two results cannot reach the resolution and the accuracy, and meanwhile, the effective detection depth of the water bottom geologic body is shallow, so that accurate water bottom geologic data information and reliable guidance are difficult to provide for the engineering construction of the area. Therefore, compared with the prior art, the system and the method of the invention have obvious advantages.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A towed underwater electromechanically prospecting system, comprising: the system comprises an underwater cable, a simple underwater electrode, a water pressure measuring and sensing unit, a cable floating and sinking unit, an underwater GPS (global positioning system), an inflator, an electrical method data acquisition and storage module and a data processing module;

the underwater GPS positioning system comprises: a transponder, an onboard transducer and a GPS; the transponders are respectively fixed at the front, middle and tail simple underwater electrodes on the underwater cable; the transponder is wirelessly connected with the onboard transducer; the GPS is fixed on the tug.

2. The towed underwater geoelectrical detection system of claim 1, wherein said cable heave unit comprises: a plurality of underwater airbags and snorkels;

the underwater airbags are fixed on the cable right above the simple underwater electrodes in a one-to-one correspondence manner; the underwater airbags are communicated with each other through the vent pipe, and the vent pipe is connected with the inflator.

3. The towed underwater electrometric sounding system of claim 1, further comprising: a water pressure display; the water pressure measuring and sensing unit is connected with the water pressure display in a wireless transmission mode.

4. The towed underwater electrometric sounding system of claim 1, further comprising: positioning the display; the positioning display is arranged on the tug boat; the shipborne transducer is connected with the positioning display.

5. The towed underwater geoelectrical detection system of claim 1, wherein said underwater electrodes comprise, in response to the fact that the underwater cables are laid on the water bottom: a dorsal fin underwater electrode, a circular arc underwater electrode and a pointed cone underwater electrode.

6. The towed underwater electrical prospecting system of claim 1, wherein the inflator is a controllable inflator connected to the snorkel tube of the cable heave unit via a gate valve.

7. The towed underwater geoelectrical detection system of claim 1, wherein said simplified underwater electrodes have a plurality of conductive reeds on the inside thereof, each of said simplified underwater electrodes being secured to each of said copper channels on said underwater cable by said conductive reeds.

8. The towed underwater geoelectrical detection system of claim 1, wherein the transponder at the mid-plain underwater electrode is affixed to the cable at a position determined by the position of the cable overlap after each movement of the underwater cable over the water bottom.

9. The towed underwater electro-hydraulic detection system of any one of claims 1 to 8, wherein the electrical data collection and storage module comprises a network parallel electrical instrument; the underwater cable is connected with a data acquisition interface of the network parallel electrical method instrument through a matched navigation plug;

10. A detection method of a towed underwater geoelectrical detection system is characterized by comprising the following steps:

(1) preparation work

(2) placing an underwater cable system at the bottom of a water

The underwater cable system is put into water, the inflator inflates the cable floating and sinking unit, the underwater cable system floats below the water surface, after the tugboat pulls the underwater cable system to reach the position of the area to be measured, the inflator gradually releases the air quantity of the underwater air bag in the cable floating and sinking unit to enable the underwater cable system to gradually sink, in the process, the underwater GPS positioning system obtains the posture and the position of the underwater cable in real time, the water pressure measuring and sensing unit measures the water depth of each simple underwater electrode, after the underwater cable system reaches the specified line measuring position and sinks into the water bottom, the electrodes are completely contacted with the soil medium at the water bottom, acquiring and storing water bottom topographic data measured by a water pressure measuring and sensing unit at each simple underwater electrode position and longitude and latitude coordinates obtained by transponders at three positions including head and tail electrodes and electrodes at an overlapping starting point on an underwater cable;

(3) collecting electrical data of water bottom geology

(4) drag to next detection position and repeat the above steps

After the data acquisition is finished, the aerator inflates the vent pipe, the underwater air bag gradually expands, the simple underwater electrode is separated from the underwater soil medium and floats upwards along with the whole underwater cable system, the tug pulls the whole underwater cable system to move towards the direction of the next detection section and reaches a designated area, the first electrode on the cable is controlled to be at the starting point of the overlapping section by an underwater GPS positioning system, namely, the position coordinate point of the middle transponder during the last acquisition, and then the air-bleeding operation is gradually carried out on the underwater air bag, so that the whole underwater cable system is sunk to the water bottom, after the underwater cable system is completely sunk to the water bottom and the simple underwater electrode is inserted into the soil medium of the water bottom, repeating the data acquisition operation and the operation of moving and dragging the underwater cable system to the next detection area until the data acquisition in the whole test area is finished;

(5) data processing stage

(6) analysis of electrical results of underwater geology