A method for jointly vertically detecting the burial depth of submarine optical cables using a magnetic antenna and a pressure gauge

Abstract

The present invention discloses a method for jointly and vertically detecting the burial depth of submarine optical cables by using a magnetic antenna and a pressure gauge, that is, a three-dimensional magnetic probe device (orthogonal magnetic rod antenna), a gyroscope, and a pressure gauge are installed together to form an underwater detector, and the magnetic probe data, pressure gauge data, and gyroscope data are transmitted to a receiving device in real time; the tilt angles of the three-dimensional magnetic probe device at two positions on the vertical section are calculated, and the average value of the submarine optical cable burial depth values obtained at each position is taken to obtain the final submarine optical cable burial depth. The biggest difference between the method disclosed in the present invention and the previous methods is that it uses vertical detection in the direction of the sea surface instead of the measurement method of sinking and dragging. While ensuring the measurement accuracy, on the one hand, it is not necessary to consider the relative distance and azimuth between the underwater detector and the submarine optical cable, and on the other hand, it is not necessary to place the underwater detector on the seabed and drag it forward by an operating ship, and the controllability is stronger.

Description

Technical Field

[0001] The present invention belongs to the field of application research on the propagation of low-frequency electromagnetic waves across water-air media, and particularly relates to a method for jointly vertically detecting the burial depth of submarine optical cables by using a magnetic antenna and a pressure gauge in this field. Background Art

[0002] Currently, the widely used and relatively mature method for detecting the burial depth of submarine cables is the active electromagnetic detection method. Its basic principle is to pass an ultra-low-frequency (30 Hz - 300 Hz) alternating current through the submarine cable, and judge the burial depth of the submarine cable by detecting the electromagnetic field signal generated around the submarine cable. Zhou Xuejun and Wang Hongxia of Naval University of Engineering proposed a method for detecting the burial depth of submarine cables by using a dual three-dimensional array probe based on this principle. In this method, two probes are fixed at both ends of a rigid rod with a length of d, and three mutually orthogonal magnetic rod antennas are respectively installed on the probes to form two arrays to detect the magnetic field signals in the x, y, and z directions. As Figure 1 shown, a rectangular coordinate system is established with the centers o 1 o 2 of the two arrays as the origin respectively, o 1 z 1 and o 2 z 2 are the directions perpendicular to the seabed, and o 1 x 1 and o 2 x 2 are the directions of the rod. By calculating the projection of the magnetic field vector sum of each probe in the oxy plane and the angle α with the x-axis, as well as the angle β 1 z 1 between o 2 z 2 (i = 1, 2). Then, the relative position relationship between the array and the submarine cable is divided into three types: the array crosses the submarine cable, the array is in the upper left of the submarine cable, and the array is in the upper right of the submarine cable. The relational expressions between the burial depth h of the submarine cable and d, α, and β i (i = 1, 2) in these three cases are respectively deduced, and then the burial depth value is obtained. i (i = 1, 2) are obtained.

[0003] The advantage of this method is that the burial depth of the submarine cable can be measured regardless of whether the array is above the submarine cable and regardless of whether the submarine cable route is perpendicular to the array. However, this method also has three deficiencies: First, when the array is far from the submarine cable or the angle between the connecting rod of the array and the axial direction of the submarine cable is small, the calculation accuracy is poor; Second, this method is not applicable to the case where any array is directly above the submarine cable; Third, since the formulas for the burial depth of the submarine cable corresponding to the two cases of the array crossing the submarine cable and the array not crossing the submarine cable are different, a determination method for these two cases needs to be given during actual measurement. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for vertically detecting the burial depth of submarine optical cables by combining a magnetic antenna and a pressure gauge.

[0005] The present invention adopts the following technical solutions:

[0006] A method for vertically detecting the burial depth of submarine optical cables by combining a magnetic antenna and a pressure gauge, the improvement lies in: a three-dimensional magnetic probe device (orthogonal magnetic rod antenna), a gyroscope and a pressure gauge are installed together to form an underwater detector, and the underwater detector is electrically connected to the receiving device on the operation ship through a cable, and transmits the magnetic probe data, the pressure gauge data and the gyroscope data to the receiving device in real time;

[0007] When the operation ship arrives at the test point, the underwater detector is put into the water and slowly sinks to the seabed. When the pressure gauge data is stable, it is determined that the underwater detector has reached the seabed, and the magnetic probe data, the pressure gauge data and the gyroscope data at position 1 are collected. Then, the underwater detector is slowly lifted as much as possible along the direction perpendicular to the sea surface by retrieving the cable, and the magnetic probe data, the pressure gauge data and the gyroscope data at positions 2 to N during the lifting process are collected in real time;

[0008] Calculate the inclination angle θ of the three-dimensional magnetic probe device at position n and position 1 in the vertical section, n = 2, 3, 4,..., N,

[0009]

[0010] Δx is the horizontal distance difference between position n and position 1, obtained from the acceleration value measured by the gyroscope, and h is the vertical distance difference between position n and position 1, obtained from the pressure difference measured by the pressure gauge; the larger θ is, the worse the calculation accuracy is;

[0011] When θ < 1°, the magnetic probe data at position n is retained to ensure the calculation accuracy. If the retained magnetic probe data is less than 3, the underwater detector is put into the water again for re-measurement;

[0012] Define the horizontal distance of the three-dimensional magnetic probe device from the submarine optical cable as x, and the vertical distance z from position 1 (seabed) to the submarine optical cable 1 is equal to the burial depth of the submarine optical cable, and the vertical distance from position n to the submarine optical cable is z 2 , z 1 , z 2 and x are all non-negative numbers, z 2 = z 1 + h;

[0013] The amplitude values of the magnetic field of the three-dimensional magnetic probe device (antenna) at position 1 and position n are respectively:

[0014]

[0015]

[0016]

[0017]

[0018] Among them, equations (2) and (3) respectively represent the amplitude values of the vertical and horizontal magnetic fields of the three-dimensional magnetic probe device (antenna) at position 1, and equations (4) and (5) respectively represent the amplitude values of the vertical and horizontal magnetic fields of the three-dimensional magnetic probe device (antenna) at position n. I is the low-frequency alternating current value of the submarine optical cable;

[0019] According to equations (2) and (3), we can obtain:

[0020]

[0021] If Use To calculate, the equation is:

[0022]

[0023] If Use To calculate, the equation is:

[0024]

[0025] The burial depth z of the submarine optical cable can be obtained through equation (7) or (8) 1 ;

[0026] For the burial depth z of the submarine optical cable obtained at each position 1 Take the average of the values to obtain the final burial depth of the submarine optical cable.

[0027] The beneficial effects of the present invention are:

[0028] The biggest difference between the method disclosed in the present invention and the previous methods is that it uses vertical detection in the direction of the sea surface instead of the measurement method of bottom towing. While ensuring the measurement accuracy, on the one hand, it is not necessary to consider the relative distance and azimuth between the underwater detector and the submarine optical cable, and on the other hand, it is not necessary to place the underwater detector on the seabed and drag it forward by an operation ship, so the maneuverability is stronger. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of a double three-dimensional array probe;

[0030] Figure 2 It is a schematic diagram of the operation mode of the method of the present invention;

[0031] Figure 3 It is a schematic diagram of the flow of the method of the present invention;

[0032] Figure 4 It is a schematic diagram of the direction of the horizontal component when moving from position 1 to position n. Specific embodiments

[0033] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Embodiment 1. This embodiment discloses a method for jointly vertically detecting the burial depth of submarine optical cables using a magnetic antenna and a pressure gauge. As shown in Figure 2 , 3, the specific steps are as follows: The first step is to lower the underwater detector into the water and slowly sink it to the seabed. When the data of the pressure gauge is stable, it is determined that the underwater detector has reached the seabed, and the data at position 1 is collected. The second step is to slowly lift the underwater detector by retrieving the cable, controlling the direction of the cable and the attitude of the underwater detector, and making the underwater detector float as much as possible along the direction perpendicular to the sea surface, and collecting (N - 1) groups of data at positions 2 to position N during the floating process in real time. The third step is to calculate the horizontal distance Δx and the vertical distance h at these two positions respectively according to the gyroscope and pressure gauge data at position 1 and position n (n = 2, 3, 4,..., N). The fourth step is to determine whether the inclination angle θ is less than 1°. If it is less than 1°, continue to the fifth step; if it is greater than or equal to 1°, return to the third step to take the next set of data (at position n + 1) for calculation. If the number of positions less than 1° is less than 3, return to the first step to lower the underwater detector into the water again for re-measurement. The fifth step is to determine whether to use Equation (7) or (8) to solve for z according to the magnitude relationship between the horizontal component and the vertical component of the magnetic field measured at position 1 1 , and then a set of submarine optical cable burial depths can be obtained, and then return to the third step to take the data at position n + 1 for calculation. The sixth step is to take the average of all the obtained submarine optical cable burial depth values z 1 obtained previously after the calculation of the data at position N is completed, and the final submarine optical cable burial depth value is obtained. Figure 4 It is a schematic diagram of the direction of the horizontal component when moving from position 1 to position n.

Claims

1. A method for jointly vertically detecting the burial depth of submarine optical cables using a magnetic antenna and a pressure gauge, characterized in that: A three-dimensional magnetic probe device, a gyroscope, and a pressure gauge are installed together to form an underwater detector. The underwater detector is electrically connected to the receiving device on the operation ship through a cable and transmits the magnetic probe data, pressure gauge data, and gyroscope data to the receiving device in real time; When the operation ship reaches the test point, the underwater detector is dropped into the water and slowly sinks to the seabed. When the pressure gauge data is stable, it is determined that the underwater detector has reached the seabed, and the magnetic probe data, pressure gauge data, and gyroscope data at position 1 are collected. Then, the underwater detector is slowly lifted vertically along the direction perpendicular to the sea surface by retrieving the cable, and the magnetic probe data, pressure gauge data, and gyroscope data at positions 2 to N during the lifting process are collected in real time; Calculate the inclination angle θ of the three-dimensional magnetic probe device at position n and position 1 in the vertical section, where n = 2, 3, 4,..., N, Δx is the horizontal distance difference between position n and position 1, obtained from the acceleration value measured by the gyroscope, and h is the vertical distance difference between position n and position 1, obtained from the pressure difference measured by the pressure gauge; When θ < 1°, retain the magnetic probe data at position n. If the number of retained magnetic probe data is less than 3, the underwater detector is dropped into the water again for re-measurement; Define the horizontal distance of the three-dimensional magnetic probe device from the submarine optical cable as x, and the vertical distance of position 1 from the submarine optical cable as z 1 is equal to the burial depth of the submarine optical cable, and the vertical distance of position n from the submarine optical cable is z 2 , z 1 , z 2 and x are both non-negative numbers, z 2 = z 1 + h; The amplitude values of the magnetic fields of the three-dimensional magnetic probe device at positions 1 and n are respectively: Among them, equations (2) and (3) respectively represent the amplitude values of the vertical and horizontal magnetic fields of the three-dimensional magnetic probe device at position 1, and equations (4) and (5) respectively represent the amplitude values of the vertical and horizontal magnetic fields of the three-dimensional magnetic probe device at position n. I is the low-frequency alternating current value of the submarine optical cable; According to equations (2) and (3), it can be obtained that: If using for calculation, the equation is: If using for calculation, the equation is: The burial depth z of the submarine optical cable can be obtained by Equation (7) or (8). 1 ; The buried depth z of the submarine optical cable obtained at each position 1 is averaged to obtain the final buried depth of the submarine optical cable.

2. The method for jointly vertically detecting the burial depth of submarine optical cables using a magnetic antenna and a pressure gauge according to claim 1, characterized in that: The three-dimensional magnetic probe device is an orthogonal magnetic rod antenna.

Images