A mudline position tester integrated with a subsea in situ equipment and a method of identification

Abstract

This invention provides a mudline position testing instrument and identification method integrated into in-situ seabed equipment. The testing instrument includes an acoustic transducer and a pressure sensor. The identification method encompasses water pressure and depth data inversion, suspended sediment concentration acoustic inversion, accurate mudline position identification, and equipment settlement calculation. It solves the problem of being unable to determine the spatial relationship between in-situ seabed equipment and the mudline due to the coupling effect of seabed surface sediments and equipment settlement. Based on the acoustic inversion principle and hydrostatic pressure calculation method, undisturbed observation is performed, avoiding the disturbance to seabed surface sediments caused by traditional contact testing and interface monitoring methods. By converting echo signal data and pressure data into sediment concentration and water depth data, and combining this with the specific location of the mudline spatial position testing instrument installed on the in-situ seabed equipment, the spatial relationship between the in-situ seabed equipment and the mudline can be accurately determined, and the settlement depth of the in-situ seabed equipment can be accurately analyzed.

Description

Technical Field

[0001] This invention relates to the field of seabed in-situ exploration and monitoring technology, and more particularly to a mudline position tester and identification method integrated into seabed in-situ equipment. Background Technology

[0002] With the deepening of marine scientific research, resource and energy development, and environmental protection, an increasing number of engineering structures and in-situ equipment need to be laid on seabed surface sediments for long-term operation, such as deep-sea observation networks, cable systems, and mining vehicles. The design, construction, and long-term operation of these structures are closely related to the physical and mechanical properties of seabed surface sediments. Therefore, the physical and mechanical properties of seabed surface sediments have attracted widespread attention, promoting the continuous development of in-situ testing technology for seabed surface sediments. Currently, the "Meiji" submersible, part of the National Key Research and Development Program led by Ocean University of China, has achieved the goal of detecting the mechanical parameters of seabed surface sediments at all ocean depths. However, the complex interaction processes between seabed surface sediments, ambient water, and in-situ detection equipment in different sea areas make it difficult to determine the positional relationship between these bottom-mounted in-situ seabed equipment and the mudline, resulting in difficulties in data analysis based on in-situ equipment.

[0003] For example, in in-situ testing of the strength of seabed surface sediments, the mudline is typically used as the upper interface of the seabed surface sediments. Above the mudline is the ambient water, which is a Newtonian fluid. Below the mudline is a mixture of water and sediment (McKee et al., 2004), defined as seabed surface sediments, exhibiting non-Newtonian fluid mechanical behavior (Nian et al., 2019; Zhang et al., 2021). In traditional in-situ seabed testing, due to the very low strength of the seabed surface sediments below the mudline, in-situ equipment is highly likely to sink into deeper sediment layers, making it difficult to determine the spatial position of the testing device relative to the mudline (it is even possible that the initial position of the test probe is already below the mudline). Consequently, the in-situ test data cannot accurately reflect the strength parameters of the seabed surface sediments and their corresponding locations. Even with high-precision probes (static cone penetration test, full-flow penetration test) that acquire data in real time, the low strength characteristics of the seabed surface sediments during probe penetration make it extremely difficult to determine when the probe contacts the mudline using in-situ test data.

[0004] Furthermore, in practical engineering applications, the vast majority of in-situ subsea equipment needs to be placed on the seabed. When this equipment is lowered to the seabed, based on experience in marine engineering geological surveys, the support legs of the equipment inevitably embed themselves into the surface sediments to a certain depth in many cases. However, under current conditions, the embedment depth is difficult to obtain and assess. Therefore, it is difficult to determine whether the observation (or detection) instruments carrying the in-situ subsea equipment are above the mudline, and when they begin to contact the mudline. More importantly, the surface sediments near the mudline are the most closely monitored part of marine observation and engineering construction.

[0005] Current identification methods mostly rely on sensors that penetrate sediment to identify mudlines. For example, patent (application number: 201810114193.1) discloses an apparatus and method for in-situ measurement of the location and mechanical properties of the seawater-sediment interface, and patent (application number: 202110814070.0) discloses a pore pressure observation device and working method for identifying seabed interfaces based on the spontaneous potential method. These methods use mechanical property testing probes and electrical property testing probes, respectively, to distinguish interfaces through penetration. These are all contact-based testing methods, which not only require the insertion of one or more probes, significantly increasing costs, but also disturb the surrounding sediment, affecting the testing of the penetration device. More importantly, during the probe insertion process, the equipment carrying the probe may shift, thus requiring the penetration device to operate synchronously with the spatial position testing device. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a mudline position tester and identification method integrated into seabed in-situ equipment. The test instrument includes an acoustic transducer and a pressure sensor, and the method encompasses water pressure data and water depth data inversion, suspended sediment concentration acoustic inversion, accurate mudline position identification, and equipment settlement calculation. It can achieve accurate determination of the spatial position of mudlines under the settlement state of most seabed in-situ equipment.

[0007] This invention is achieved through the following technical solution: a mudline position tester and identification method integrated into seabed in-situ equipment. The mudline position tester, integrated into seabed in-situ equipment, includes a pressure-resistant housing with a fixing device, a connecting channel installed inside the pressure-resistant housing, a data acquisition and storage control unit, a battery, a connecting pipe, a pressure sensor, and an acoustic transducer located at the lower end of the pressure-resistant housing. The fixing device is fixedly installed on the upper part of the pressure-resistant housing, with one end connected to the tester and the other end connected to the bottom-mounted seabed in-situ equipment. The data acquisition and storage control unit is connected to the pressure sensor via a data cable, which extends to the acoustic transducer through the connecting channel. The pressure sensor collects the water pressure at the top of the tester in real time through the connecting pipe. The acoustic transducer is located at the lower part of the tester, and the data acquisition and storage control unit sets the tester to emit acoustic signals of specific thickness and layer to a profile within a water depth range below the installation position. The battery is located between the pressure sensor and the acoustic transducer, and supplies power to the pressure sensor, the acoustic transducer, and the data acquisition and storage control unit via wires.

[0008] The identification method for a mudline position tester integrated into in-situ seabed equipment includes the following steps:

[0009] Step 1: Based on the regional sea conditions and geological information survey, determine the seabed conditions at the instrument deployment location;

[0010] Step 2: Calibrate the pressure sensor and set the device's observation time, acquisition frequency, and acoustic layer thickness h. Determine the cable, deployment vessel, deployment date, and station latitude and longitude. ;

[0011] Step 3: Fix the tester to the structure of the bottom-mounted seabed in-situ equipment using a fixing device, with no obstructions below it, and record the height H of the installation position from the support foot. H is the acoustic signal observation range of the tester.

[0012] Step 4: Deploy the device to the designated location to conduct tests, wait for all observations to be completed, and then retrieve it from the water. On land, disassemble, maintain, and store the device, read the data from the acquisition, storage, and control unit, obtain the real-time water depth, and complete the correction of the echo signal.

[0013] Step 5: Conduct indoor instrument calibration experiments to ensure that the actual in-situ test data corresponds to the spatial position of the mudline and the equipment settlement distance.

[0014] As a preferred option, step 4 specifically includes the following steps:

[0015] Step 4.1: Process the in-situ acquired water pressure data by averaging the real-time water pressure data observed by the pressure sensor in ten-minute intervals to obtain the average water pressure. Based on the hydrostatic pressure calculation method formula (1), This data is converted into water depth data for observation equipment.

[0016] (1)

[0017] in, The water depth at the instrument installation location is in meters (m). The density of seawater is kg·m⁻³. The acceleration due to gravity is m·s⁻². The average water pressure is expressed in Pa.

[0018] Step 4.2: Combine the latitude and longitude of the instrument placement location and instrument installation water depth Obtain the spatial location of the in-situ marine bottom testing equipment. .

[0019] Step 4.3: Use formula (2) to process the original echo signal. Corrected to reflect the backscattering intensity of suspended sediment concentration in water bodies ;

[0020] (2)

[0021] in, The backscattering intensity is expressed in dB. =0.4 is the received signal conversion factor, dB·count-1; It is the echo intensity received by the instrument, count; This is system noise, in dB; It is the distance from the acoustic transducer to the observation position, calculated from the layer thickness, in meters (m). is the absorption coefficient, obtained from the properties of the sediment in step 1, dB·m⁻¹; C is a constant related to the transducer, including errors caused by factors such as the emission pulse and emission power performance parameters, calculated from the transducer performance indicators, dB.

[0022] As a preferred embodiment, the fixing device includes screws, fixing buckles, and fixing rods. There are four fixing rods evenly distributed on the upper part of the pressure-resistant shell. The fixing rods have mounting holes. The screws pass through the mounting holes to fix the tester to the fixing buckles. One end of the fixing buckle is connected to the tester, and the other end is connected to the bottom-mounted seabed in-situ equipment to achieve the fixing of the tester.

[0023] As a preferred option, step 5 specifically includes the following steps:

[0024] Step 5.1: Conduct a calibration test indoors using the same substrate as the observation location. Fix the mudline identification device above the calibration bucket, turn on the instrument, and perform filtration experiments on water samples from different locations to obtain the suspended sediment concentration. ;

[0025] Step 5.2: Collect water sample filtration test data The backscattering intensity after corresponding position correction is fitted according to formula (3) to determine the fitting coefficient. ;

[0026] (3)

[0027] in, The concentration of suspended sediment is expressed in kg·m⁻³. The backscattering intensity is expressed in dB. for The parameters obtained from the fitting;

[0028] Step 5.3: Substitute the fitting coefficients into formula (3) to obtain the suspended sediment concentration. Backscattering intensity The correlation was then used to obtain the suspended sediment concentration within the observation profile H below the test instrument;

[0029] Step 5.4: Calculate the concentration gradient of suspended sediment concentration with stratification height h as the independent variable and stratification concentration as the dependent variable; the gradient calculation can be based on the gradient function in Matlab.

[0030] Step 5.5: Based on the difference in suspended sediment concentration between the environmental water body and the mudline, find the height position where the maximum gradient value is located from top to bottom, which is the mudline position H1;

[0031] Step 5.6: Based on the installation position of the testing instrument on the bottoming device, the settlement depth H2 = H – H1 can be determined.

[0032] By employing the above technical solutions, this invention has the following beneficial effects compared to existing technologies:

[0033] (1) This invention patent provides a mudline spatial position testing instrument integrated into seabed in-situ equipment. It solves the problem that the spatial position relationship between seabed in-situ equipment and mudline cannot be determined under the coupling effect of seabed surface sediments and equipment subsidence.

[0034] (2) The mudline spatial position tester provided by this invention has the advantages of small size, easy installation, low power consumption and strong identification ability. It can be used on most seabed in-situ equipment through a fixed device, and realize synchronous observation with seabed in-situ equipment.

[0035] (3) Based on acoustic principles, this invention conducts undisturbed observation, avoiding the disturbance to seabed surface sediments caused by traditional contact testing methods and interface monitoring methods, thus ensuring the accuracy of in-situ test data.

[0036] (4) Based on the acoustic inversion principle and hydrostatic pressure calculation method, this invention patent converts echo signal data and pressure data into sediment concentration data and water depth data. Combined with the specific location of the mudline spatial position tester installed on the seabed in-situ equipment, it can accurately determine the spatial position relationship between the seabed in-situ equipment and the mudline, and accurately analyze the settling depth of the seabed in-situ equipment.

[0037] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0039] Figure 1 This is a schematic diagram of the equipment.

[0040] Figure 2 This is a schematic diagram showing the instrument's installation location and observation range;

[0041] Figure 3 This is a schematic diagram for identifying the location of the mudline;

[0042] in, Figures 1 to 3 The correspondence between the reference numerals and components in the attached drawings is as follows:

[0043] 1. Fixing device, 2. Data acquisition and storage control unit, 3. Connection channel, 4. Acoustic transducer, 5. Connection tube, 6. Pressure sensor, 7. Battery, 8. Pressure-resistant housing. Detailed Implementation

[0044] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0045] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0046] The following is combined with Figures 1 to 3 The mudline position tester and identification method integrated into the seabed in-situ equipment according to embodiments of the present invention will be described in detail.

[0047] like Figure 1As shown, this invention proposes a mudline position tester and identification method integrated into seabed in-situ equipment. The mudline position tester integrated into seabed in-situ equipment includes a pressure-resistant housing 8 with a fixing device 1, a connecting channel 3, a data acquisition and storage control unit 2, a battery 7, a connecting pipe 5, a pressure sensor 6 installed inside the pressure-resistant housing 8, and an acoustic transducer 4 located at the lower end of the pressure-resistant housing 8. The fixing device 1 includes screws, fixing buckles, and fixing rods. There are four fixing rods evenly distributed on the upper part of the pressure-resistant housing 8. The fixing rods have mounting holes. The screws pass through the mounting holes to fix the tester to the fixing buckles. One end of the fixing buckle is connected to the tester, and the other end is connected to the bottom-mounted seabed in-situ equipment to realize the fixation of the tester. The data acquisition and storage control unit 2 is connected to the pressure sensor 6 via a data cable. The data cable extends to the acoustic transducer 4 via a connection channel 3, enabling the data acquisition and storage control unit 2 to set, adjust, and store the sensor test parameters. The pressure sensor 6 collects the water pressure located at the top of the tester in real time via a connecting pipe 5. The acoustic transducer 4 is located at the bottom of the tester. The data acquisition and storage control unit 2 sets the tester to emit acoustic signals of specific thickness and layer to the profile within the water depth range below the installation position. The interval between each sampling depth can be set, and the transducer 4 receives signals reflected back from the silt or other suspended particles in the depth profile. The battery 7 is located between the pressure sensor 6 and the acoustic transducer 4, and supplies power to the pressure sensor 6, the acoustic transducer 4, and the data acquisition and storage control unit 2 via wires.

[0048] The identification method for a mudline position tester integrated into in-situ seabed equipment includes the following steps:

[0049] Step 1: Based on the regional sea conditions and geological information survey, determine the seabed conditions at the instrument deployment location;

[0050] Step 2: Calibrate the pressure sensor according to the national standard (GB / T12763.10—2007), and set the device's observation time, acquisition frequency, and acoustic layer thickness. h Determine the cable, deployment vessel, and deployment date and location (latitude and longitude). ;

[0051] Step 3: Secure the testing instrument to the bottom-mounted seabed in-situ equipment frame using fixing device 1. Ensure there are no obstructions below, so as not to block the propagation of acoustic signals or affect the normal operation of other onboard observation instruments; record the height of the installation position from the support legs. H , H This refers to the acoustic signal observation range of the test instrument; see the instrument's relevant locations. Figure 2 .

[0052] Step 4: Deploy the device to the designated location for testing. After all observations are completed, retrieve it from the water. Disassemble, maintain, and store the device on land. Read the data from the acquisition, storage, and control unit 2 to obtain the real-time water depth and complete the echo signal correction. Specifically, this includes the following steps:

[0053] Step 4.1: Process the in-situ acquired water pressure data by averaging the real-time water pressure data observed by pressure sensor 6 in ten-minute intervals to obtain the average water pressure. To eliminate water pressure changes caused by high-frequency factors; based on the hydrostatic pressure calculation method formula (1) This data is converted into water depth data for observation equipment.

[0054] (1)

[0055] in, The water depth at the instrument installation location is in meters (m). The density of seawater is kg·m -3 ; Let m be the acceleration due to gravity. -2 ; The average water pressure is expressed in Pa.

[0056] Step 4.2: Combine the latitude and longitude of the instrument placement location and instrument installation water depth Obtain the spatial location of the in-situ marine bottom testing equipment. .

[0057] Step 4.3: The echo signal obtained by acoustic transducer 4 is distorted due to noise and signal propagation attenuation, and cannot be used directly. Formula (2) is used to convert the original echo signal. Corrected to reflect the backscattering intensity of suspended sediment concentration in water bodies ;

[0058] (2)

[0059] in, The backscattering intensity is expressed in dB. =0.4 is the received signal unit conversion factor, dB·count -1 ; It is the echo intensity received by the instrument, count; This is system noise, in dB; It is the distance from acoustic transducer 4 to the observation position, calculated from the layer thickness, in meters; It is the absorption coefficient, obtained from the sediment properties in step 1, dB·m -1 ; CIt is a constant related to the transducer, including errors caused by factors such as the transmitted pulse and transmitted power performance parameters, and is calculated through the transducer performance indicators, in dB.

[0060] Step 5: Conduct indoor instrument calibration experiments to ensure correspondence between actual in-situ test data and the spatial location of the mudline and the equipment settlement distance, guiding engineering design and scientific research. This includes the following steps:

[0061] Step 5.1: Conduct a calibration test indoors using the same substrate as the observation location. Fix the mudline identification device above the calibration bucket, turn on the instrument, and perform filtration experiments on water samples from different locations to obtain the suspended sediment concentration. ;

[0062] Step 5.2: Collect water sample filtration test data The backscattering intensity after corresponding position correction is fitted according to formula (3) to determine the fitting coefficient. ;

[0063] (3)

[0064] in, The suspended sediment concentration is expressed in kg·m³. -3 ; The backscattering intensity is expressed in dB. for The parameters obtained from the fitting;

[0065] Step 5.3: Substitute the fitting coefficients into formula (3) to obtain the suspended sediment concentration. Backscattering intensity The correlation was then used to obtain the following observation profile from the testing instrument. H The concentration of suspended sediment within the specified range;

[0066] Step 5.4: Assess suspended sediment concentration by stratification height h Using stratified concentrations as the dependent variable and independent variable as the independent variable, the concentration gradient is calculated; the gradient can be calculated using the gradient function in Matlab.

[0067] Step 5.5: Based on the difference in suspended sediment concentration between the environmental water body and the mudline, the height at which the maximum gradient value is located from top to bottom is the location of the mudline. H 1, such as Figure 3 ;

[0068] Step 5.6: The settlement depth can be determined based on the installation position of the testing instrument on the bottom-sitting equipment. H 2= H – H 1.

[0069] In the description of this invention, the term "a plurality of" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0070] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying a mudline position tester integrated into a seabed in-situ equipment, the mudline position tester integrating the seabed in-situ equipment comprising a pressure-resistant housing (8) with a fixing device (1), a connecting channel (3), a data acquisition and storage control unit (2), a battery (7), a connecting pipe (5), a pressure sensor (6) installed inside the pressure-resistant housing (8), and an acoustic transducer (4) located at the lower end of the pressure-resistant housing (8), characterized in that... The fixing device (1) is fixedly installed on the upper part of the pressure-resistant shell (8), with one end connected to the tester and the other end connected to the bottom-mounted seabed in-situ equipment. The acquisition, storage and control unit (2) is connected to the pressure sensor (6) through a data line, and the data line extends to the acoustic transducer (4) through the connection channel (3). The pressure sensor (6) collects the water pressure at the top of the tester in real time through the connecting pipe (5). The acoustic transducer (4) is located at the lower part of the tester and is set by the acquisition, storage and control unit (2) to emit acoustic signals of specific thickness and layer to the profile within the water depth range below the installation position. The battery (7) is located between the pressure sensor (6) and the acoustic transducer (4) and supplies power to the pressure sensor (6), the acoustic transducer (4) and the acquisition, storage and control unit (2) through wires. Specifically, the following steps are included: Step 1: Based on the regional sea conditions and geological information survey, determine the seabed conditions at the instrument deployment location; Step 2: Calibrate the pressure sensor and set the device's observation time, acquisition frequency, and acoustic layer thickness. h Determine the cable, deployment vessel, and deployment date and location (latitude and longitude). ; Step 3: Fix the testing instrument to the structure of the bottom-mounted seabed in-situ equipment using the fixing device (1), ensuring there are no obstructions below it, and record the height of the installation position from the supporting legs. H , H This refers to the acoustic signal observation range of the tester; Step 4: Deploy the device to the designated location for testing, wait for all observations to be completed, and then retrieve the water. On land, disassemble, maintain, and store the device, read the data from the acquisition, storage, and control unit (2), obtain the real-time water depth, and complete the echo signal correction. Specifically, the following steps are included: Step 4.1: Process the in-situ acquired water pressure data, and average the water pressure data observed in real time by the pressure sensor (6) in ten-minute intervals to obtain the average water pressure. Based on the hydrostatic pressure calculation method formula (1), This data is converted into water depth data for observation equipment. （1） in, The water depth at the instrument installation location is in meters (m). The density of seawater is kg·m -3 ; Let gravitational acceleration be m·s -2 ; The average water pressure is expressed in Pa. Step 4.2: Combine the latitude and longitude of the instrument placement location and water depth at instrument installation location Obtain the spatial location of the in-situ marine bottom testing equipment. ; Step 4.3: Use formula (2) to process the original echo signal. Corrected to reflect the backscattering intensity of suspended sediment concentration in water bodies ; （2） in, The backscattering intensity is expressed in dB. =0.4 is the received signal unit conversion factor, dB·count -1 ; It is the echo intensity received by the instrument, count; This is system noise, count; It is the distance from the acoustic transducer (4) to the observation position, calculated from the layer thickness, in meters; It is the absorption coefficient, obtained from the sediment properties in step 1, dB·m -1 ; C These are constants related to the transducer, including errors caused by factors such as the transmitted pulse and transmitted power performance parameters, calculated using the transducer performance indicators, in dB; Step 5: Conduct indoor instrument calibration experiments to ensure correspondence between the actual in-situ test data and the spatial correspondence of the mudline and the equipment settlement distance; this specifically includes the following steps: Step 5.1: Conduct a calibration test indoors using the same substrate as the observation location. Fix the mudline identification device above the calibration bucket, turn on the instrument, and perform filtration experiments on water samples from different locations to obtain the suspended sediment concentration. ; Step 5.2: Collect water sample filtration test data The backscattering intensity after corresponding position correction is fitted according to formula (3) to determine the fitting coefficient. ; （3） in, The suspended sediment concentration is expressed in kg·m³. -3 ; The backscattering intensity is expressed in dB. for The parameters obtained from the fitting; Step 5.3: Substitute the fitting coefficients into formula (3) to obtain the suspended sediment concentration. With backscattering intensity The correlation was then used to obtain the following observation profile from the testing instrument. H The concentration of suspended sediment within the specified range; Step 5.4: Assess suspended sediment concentration by stratification height h The concentration gradient is calculated using stratified concentration as the dependent variable and independent variable as independent variable; the gradient calculation is based on the gradient function in Matlab. Step 5.5: Based on the difference in suspended sediment concentration between the environmental water body and the mudline, the height at which the maximum gradient value is located from top to bottom is the location of the mudline. H 1; Step 5.6: The settlement depth can be determined based on the installation position of the testing instrument on the bottom-sitting equipment. H 2= H – H 1.

2. The identification method of a mudline position tester integrated into in-situ seabed equipment according to claim 1, characterized in that... The fixing device (1) includes screws, fixing buckles and fixing rods. There are four fixing rods evenly distributed on the upper part of the pressure-resistant shell (8). The fixing rods have mounting holes. The screws pass through the mounting holes to fix the tester to the fixing buckles. One end of the fixing buckle is connected to the tester, and the other end is connected to the bottom-mounted seabed in-situ equipment to fix the tester.

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