Method for identifying underwater terrain erosion and deposition state in real time

Abstract

The invention relates to a method for identifying an underwater terrain erosion and deposition state in real time, which comprises the following steps: placing a hexahedral frame with six hollow surfaces at monitoring points at the bottom of a water body, fixing a water depth sensor at the top of the frame, and fixing a water pressure sensor at the bottom, so that the water pressure sensor is just exposed in an initial state; the signal emission direction of the water depth sensor is downward. The real-time measurement values of the water depth sensor and the water pressure sensor are utilized to construct a time sequence for elevation value calculation, and the real-time elevation value of the monitoring point is obtained. The monitoring device used by the method can be directly placed on the river surface, is convenient to install and use, displaces along with the movement of the riverbed, is convenient to accurately identify the scouring condition of the riverbed, can judge the state change of riverbed scouring and deposition, and obtains the accurate topographic change data time sequence of the underwater riverbed; and technical and data support is provided for bank collapse early warning.

Description

Technical Field

[0001] The invention belongs to the field of water conservancy topography surveying and relates to a method for real-time identification of the scouring and silting state of underwater terrain. Background Art

[0002] Bank collapse endangers the safety of embankments and directly affects the operation of infrastructure such as ports, terminals, shipping facilities, and drainage outlets on both sides of the river. Therefore, it is necessary to conduct real-time monitoring of the stability of bank slopes prone to collapse along the river, accurately obtain real-time changes in underwater terrain in sections prone to collapse, scientifically analyze bank deformation information, scientifically predict bank instability, discover bank collapse hazards in advance, and proactively deal with them to minimize losses.

[0003] Patent ZL202210099622.9 discloses a real-time monitoring device for underwater bank displacement. This method uses water pressure changes measured by a water pressure sensor to infer underwater topography changes. When scouring occurs at the location where the water pressure sensor is located, the water pressure sensor moves downward with the riverbed, and the measured water pressure increases. The underwater riverbed elevation at the monitoring point is inferred based on the water pressure and the real-time water depth. However, when the water body contains a large amount of sediment, the underwater riverbed will silt up, and the sensor surface will be covered with sediment. Because the sediment pressure is greater than the water pressure, the water pressure measured by the water pressure sensor will also increase in this case. If the above method is used, it will still be inferred that the riverbed has scoured at that location, which may lead to the misjudgment of underwater topography changes. In addition, the device involved in this method is mainly used for bank displacement monitoring. The sensor needs to be fixed with a pull rod. When the riverbed is scouring, the water pressure sensor does not necessarily move downward with the riverbed, so the measured water pressure value will not change, resulting in the inability to detect scouring. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems existing in the above-mentioned prior art and provide a method for real-time identification of the scouring and silting status of underwater terrain.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A method for real-time identification of underwater terrain scouring and silting conditions, the method comprising:

[0007] A hexahedral frame with six hollow sides is placed at the monitoring point at the bottom of the water body. A water depth sensor is fixed on the top of the frame, and a water pressure sensor is fixed on the bottom, so that the water pressure sensor is exposed in the initial state; the signal transmission direction of the water depth sensor is downward;

[0008] Get the initial measurement value h of the water depth sensor a0 , and based on the initial measurement value P of the water pressure sensor s0 The converted initial water depth value h at the location of the water pressure sensor b0 ; Calculate the real-time water level and h at the monitoring pointb0 The difference between the initial height h0 and the initial height h1 at the monitoring point is:

[0009] Collect real-time measurement values of water depth sensor and water pressure sensor h am 、P m , judge the scouring and silting status of the monitoring point, including:

[0010] Record the h at each moment am 、P m , and in h am = h a0 Time conversion P m The corresponding real-time water depth value of the water pressure sensor h bm ;

[0011] If h am =h a0 , then the monitoring point has no change or is eroded at the current moment; based on the real-time water level and water depth value of the water pressure sensor at the monitoring point at the current moment h bm Get the elevation value at the monitoring point;

[0012] If h am <h a0 , then the monitoring point is silted up at the current moment; based on h a0 and h am Obtain the buried depth of the water pressure sensor, and combine it with the elevation value of the monitoring point at the previous moment to obtain the elevation value of the monitoring point at the current moment; or, based on the water depth sensor measurement value h at the previous moment am-1 and the h am Get the current siltation depth and combine it with the elevation value of the monitoring point at the previous moment to get the elevation value of the monitoring point at the current moment.

[0013] As a preferred embodiment, the method further includes assigning a different identifier to the state of the monitoring point at each moment; when calculating the elevation value of the monitoring point at the current moment, the scouring or silting state of the monitoring point at the previous moment is confirmed by detecting the identifier at the previous moment, so as to select a calculation method for the current monitoring point elevation value. For example, -1 and 1 are used as identifiers for the scouring and silting states, respectively. For the silting state, the current elevation value calculation method is different based on whether the previous moment was a scouring state or a silting state. In this case, after identifying the previous moment's state, the elevation value calculation method can be quickly confirmed.

[0014] As a preferred embodiment, the frame is 0.4-0.6 m high.

[0015] As a preferred embodiment, the water pressure sensor and the water depth sensor are fixed to the top and bottom of the frame respectively through brackets.

[0016] As a preferred embodiment, the brackets are connected to the top diagonal and bottom diagonal portions of the frame in a cross-shaped manner, and the water pressure sensor and the water depth sensor are respectively fixed at the intersections.

[0017] As a preferred implementation, the water depth sensor is fixed directly above the water pressure sensor.

[0018] As a preferred embodiment, the frame is a quadrangular pyramid-shaped frame.

[0019] As a preferred embodiment, the frame is placed parallel to the water flow direction.

[0020] As a preferred embodiment, the method further includes placing a plurality of the frames at intervals on the bottom of the water body to measure the scouring and silting status of the range terrain.

[0021] As a preferred embodiment, the water depth sensor is an acoustic wave sensor.

[0022] The present invention has the following beneficial effects:

[0023] (1) The monitoring device used in the method of the present invention can be placed directly on the river surface, is easy to install and use, and moves with the movement of the riverbed, making it easy to accurately identify the scouring conditions of the riverbed;

[0024] (2) The method of the present invention combines two sensors to identify the scouring and silting conditions of the riverbed, and can also combine historical data status changes to determine the state changes of riverbed scouring and silting, and obtain the accurate time series of underwater riverbed terrain change data, providing technical and data support for bank collapse warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a device for identifying underwater real-time terrain scouring and sedimentation.

[0026] Figure 2 This is a schematic diagram of underwater riverbed scour calculation at time T1.

[0027] Figure 3 This is a schematic diagram of underwater riverbed sedimentation calculation at time T1.

[0028] Figure 4 It is a calculation diagram of the underwater riverbed being scoured first and then scoured at time T2.

[0029] Figure 5 This is a calculation diagram of the underwater riverbed being eroded first and then deposited at time T2.

[0030] Figure 6 This is a calculation diagram of the underwater riverbed first silting up and then scouring at time T2.

[0031] Figure 7It is a schematic diagram of calculation of the underwater riverbed first silting up and then silting up at time T2. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] The real-time water level measured in the embodiment is the real-time water level at the monitoring point, and the real-time water level is obtained using a water level measuring device conventionally configured on the shore.

[0034] A section of the lower reaches of the Yangtze River in Jiangsu Province that is prone to bank collapse was selected as the experimental area. Figure 1 As shown, a quadrangular pyramid frame is set up, with a height of 0.5m. The six sides of the frame are hollow, and both mud and water can pass through the inside of the pyramid. In addition, the pyramid should have a certain amount of deadweight to ensure that it can remain stable under the impact of large water flows and will not overturn. A water depth sensor A is installed in the middle of the top of the pyramid, and a water pressure sensor B is installed in the middle of the bottom. Brackets are fixed to the top and bottom frames of the pyramid respectively. The brackets are connected to the diagonal corners of the top frame and the diagonal corners of the bottom frame in a cross form. The water depth sensor A and water pressure sensor B are fixed to the intersection of the top and bottom brackets of the frame respectively. The brackets should reduce the lateral area as much as possible while ensuring firmness, so that the top and bottom of the pyramid are left as empty as possible to ensure the fluidity of mud and water inside the device. The data collected by the water depth sensor A and the water pressure sensor B are preferably transmitted via cables.

[0035] After the device is built, it is placed on the riverbed. At this time, the sensor B on the bracket is exposed. Figure 1 As shown, the water depth h measured in real time by the water depth sensor A is a0 That is, the distance between it and the water pressure sensor B. The distance between the two at the initial measurement (at time T0) is L0. At this time, h a0 =L0. The water pressure measured in real time by the water pressure sensor is P m According to formula (1), water pressure can be converted into water depth h bm :

[0036] (1)

[0037] In the formula is the density of water, is the acceleration due to gravity, h bm T m The water depth at the water pressure sensor at the moment. At time T0, the real-time water level H0 of the water surface and the real-time water depth h of the riverbed measured by the water pressure sensor b0 The difference is the real-time underwater slope elevation value of the monitoring point at time T0 h0=H0-h b0 , assuming that the initial measured underwater slope elevation is h0.

[0038] Multiple data acquisitions are performed according to the set data acquisition frequency. Assume that the time of the second data acquisition is the T1 moment, the real-time water level of the water surface at the T1 moment is H1, and the real-time water pressure of the riverbed measured by the water pressure sensor B is P1. At this time, the scouring and siltation state of the underwater riverbed is unknown, and the distance h between the water depth sensor A and the water pressure sensor B measured in real time is used to judge the scouring and siltation state inside the support by comparing it with the size of L0: a1 To judge the scouring and siltation state inside the support by comparing the size between h

[0039] (1)If h a1 = L0, as shown in Figure 2 , it means that there is no silt above the sensor B (the real-time state of the support is marked as scouring, represented by S1 = -1). At this time, the real-time water pressure P1 of the riverbed is only the pressure caused by the water above the riverbed. Therefore, the water depth h b1 can be calculated by Equation (1). At this time, the underwater riverbed elevation value h1 at this location can be calculated by Equation (2), and the scouring thickness Δh1 at this location is Δh1 = |h1 - h0|. Since h1 < h0, the final state of the riverbed at the T1 moment (relative to the initial state, i.e., the state at the T0 moment) is judged to be scouring (S1’ = -1).

[0040] h1 = H1 - h b1 (2)

[0041] From the T0 moment, record the state at each moment, including the measured values and calculated values, into a two-dimensional table. For example, Table 1 shown below:

[0042] Table 1

[0043]

[0044] In the table, the final scouring and siltation state is judged according to the positive or negative of h n+1 - h0. A positive value indicates siltation, and a negative value indicates scouring.

[0045] (2)If h a1 < L0, as shown in Figure 3 , it means that there is silted sediment above the sensor B (the real-time state of the support is marked as siltation, represented by S1 = 1). At this time, the real-time water pressure P1 of the riverbed is the sum of the water pressure above the riverbed and the sediment pressure. The water depth h b1 ’ calculated according to Equation (1) is not the actual water depth h b1 of the water pressure sensor. Furthermore, the elevation value h1 = H1 - h b1 ’ calculated by Equation (2) is not the actual elevation value of the underwater riverbed at this location. At this time, the actual elevation value of the underwater riverbed at this location is h1 = h0 + L0 - h a1 , and the siltation thickness Δh1 at this location is Δh1 = |L0 - h a1|. When h1 > h0, the final state of the riverbed at time T1 (relative to the initial state at time T0) is judged to be siltation (S1’ = 1).

[0046] Assume that the time of the third data collection is time T2. Starting from time T2, the scouring and siltation state is judged by combining the final state of the riverbed at historical times. The real-time water level of the water surface at time T2 is H2, and the real-time water pressure P2 of the riverbed measured by the water pressure sensor B. At this time, the scouring and siltation state of the underwater riverbed is unknown, and the distance h between it and the water pressure sensor B measured by the water depth sensor A in real time a2 is used to judge the scouring and siltation state inside the support by comparing with the size of L0:

[0047] (1) If h a2 = L0, as Figure 4 shown, it means that there is no silt above the sensor B (the real-time state of the support S2 = -1). At this time, the real-time water pressure P2 of the riverbed is only the pressure caused by the water above the riverbed. Therefore, the water depth h b2 can be calculated by Equation (1). At this time, the underwater riverbed elevation value h2 at this place can be calculated by Equation (2), and the scouring thickness Δh2 at this place of the riverbed = |h2 - h0|. When h2 < h0, the final state of the riverbed at time T2 is judged to be scouring (S2’ = -1).

[0048] (2) If h a2 < L0, as Figure 5 shown, it means that there is silt sediment above the sensor B (the real-time state of the support S2 = 1). Similarly, at this time, the real-time water pressure P2 of the riverbed is the sum of the water pressure above the riverbed and the silt pressure. The water depth h b2 ’ calculated according to Equation (1) is not the actual water depth h b2 of the water pressure sensor. At this time, h2 needs to be calculated according to the real-time scouring and siltation state S1 of the support at time T1.

[0049] a. If the real-time state of the riverbed at time T1 is scouring, as Figure 5 shown, that is, S1 = -1. At this moment, the underwater riverbed elevation value h2 = h1 + L0 - h a2 . If h2 < h0, judge that the final state of the riverbed is scouring (S2’ = -1), and the scouring thickness Δh2 at this place of the riverbed = |h2 - h0|; if h2 > h0, judge that the final state of the riverbed is siltation (S2’ = 1), and the siltation thickness Δh2 at this place of the riverbed = |h2 - h0|.

[0050] b. If the final state of the riverbed at time T1 is siltation, as Figure 6 、 Figure 7 shown, that is, S1 = 1. At this moment, there are the following two situations for the underwater riverbed elevation:

[0051] (a) As Figure 6 As shown, scouring occurred inside the support after time T1 at time T2. At this time:

[0052] h2 = h1 - (Y1 - Y2) = h1 - Y1 + Y2 = h1 - (L0 - h a1 ) + (L0 - h a2 ) = h1 + h a1 -h a2 ;

[0053] where Y1 = L0 - h a1 , Y2 = L0 - h a2 .

[0054] (b) As Figure 7 shown, siltation occurred inside the support after time T1 at time T2. At this time:

[0055] h2 = h1 + (Y2 - Y1) = h1 + h a1 -h a2 ;

[0056] where Y1 = L0 - h a1 , Y2 = L0 - h a2 .

[0057] In summary, when S1 = 1, the underwater riverbed elevation h2 at time T2 = h1 + h a1 -h a2 . If h2 < h0, the final state of the riverbed at this time is scouring (S2' = -1), and the final scouring thickness Δh2 at this location of the riverbed = |h2 - h0|; if h2 > h0, the final state of the riverbed at this time is siltation (S2' = 1), and the final siltation thickness Δh2 at this location of the riverbed = |h2 - h0|.

[0058] Next, the fourth measurement is carried out (at time T3). The real-time water level of the water surface at time T3 is H3, and the real-time water pressure P3 of the riverbed measured by the water pressure sensor B. At this time, the scouring and siltation state of the underwater riverbed is unknown. The distance h a3 between the water depth sensor A and the water pressure sensor B measured in real time is used to judge the scouring and siltation state inside the support:

[0059] ① If h a3 = L0, it means that there is no silt above the sensor B (the real-time state of the support at this time S3 = -1). At this time, the real-time water pressure P3 of the riverbed is only the pressure caused by the water above the riverbed. Therefore, the water depth h b3 can be calculated from Equation (1). At this time, the underwater riverbed elevation value h3 at this location can be calculated from Equation (2).

[0060] ② If h a3<L0 indicates that there is silt accumulation above sensor B (at this time, the state S3 of the support = 1). Similarly, at this time, the real-time water pressure P3 of the riverbed is the sum of the water pressure above the riverbed and the silt pressure. The water depth h calculated according to Equation (1) b3 ’ is not the actual water depth h of the water pressure sensor b3 . At this time, h3 needs to be calculated based on the real-time scouring and siltation state of the support at time T2.

[0061] a. If the real-time state of the support at time T2 is scouring, that is, S2 = -1, at this moment, the underwater riverbed elevation value h3 = h2 + L0 - h a3 . If h3 < h0, the final state of the riverbed at this time is scouring (S3’ = -1), and the scouring thickness Δh3 of the riverbed at this place = |h3 - h0|; if h3 > h0, the final state of the riverbed at this time is siltation (S3’ = 1), and the siltation thickness Δh3 of the riverbed at this place = |h3 - h0|.

[0062] b. If the real-time state of the support at time T2 is siltation, that is, S2 = 1, there are the following two situations for the underwater riverbed elevation at this moment:

[0063] (a) Scouring occurs inside the support at time T3 after time T2. At this time, h3 = h2 - (Y2 - Y3) = h2 + h a2 - h a3 , where Y2 = L0 - h a2 , Y3 = L0 - h a3 .

[0064] (b) Siltation occurs inside the support at time T3 after time T2. At this time, h3 = h2 + (Y3 - Y2) = h2 + h a2 - h a3 , where Y2 = L0 - h a2 , Y3 = L0 - h a3 .

[0065] In summary, when S2 = 1, the underwater riverbed elevation h3 at time T3 = h2 + h a2 - h a3 .

[0066] If h3 < h0, the final state of the riverbed at this time is scouring (S3’ = -1), and the final scouring thickness Δh3 of the riverbed at this place = |h3 - h0|; if h2 > h0, the final state of the riverbed at this time is siltation (S3’ = 1), and the final siltation thickness Δh3 of the riverbed at this place = |h3 - h0|.

[0067] ……

[0068] And so on. When making the (n + 1)-th measurement, the real-time water level at time T n is Hn , the real-time water pressure P of the riverbed measured by the water pressure sensor B n . At this time, the scouring and silting state of the underwater riverbed is unknown. The distance h between the water depth sensor A and the water pressure sensor B measured in real time is used to judge the scouring and silting state inside the support by comparing it with L0: an If h

[0069] ① If h an = L0, it means there is no silt above the sensor B (at this time, the state S of the support n = -1). The water depth h can be calculated from Equation (1). bn . At this time, the underwater riverbed elevation value h at this location n can be calculated from Equation (2).

[0070] ② If h an < L0, it means there is silt accumulation above the sensor B (at this time, the state S of the support n = 1). At this time, h needs to be calculated according to the scouring and silting state of the support at time T n-1 : n :

[0071] a. If the real-time state of the support at time T n-1 is scouring, that is, S n-1 = -1, the underwater riverbed elevation value h at this moment n = h n-1 + L0 - h an ;

[0072] b. If the real-time state of the support at time T n-1 is siltation, that is, S n-1 = 1, the underwater riverbed elevation h at time T n = h n + h n-1 - h an-1 - h an .

[0073] If h n < h0, the final state of the riverbed is scouring (S n ’ = -1). At this time, the final scouring thickness Δh of the riverbed at this location n = |h n - h0|; if h n > h0, the final state of the riverbed is siltation (S n ’ = 1). At this time, the final siltation thickness Δh of the riverbed at this location n = |h n - h0|.

Claims

1. A method for real-time identification of underwater terrain erosion and deposition status, characterized in that: The method comprises: A hexahedral frame with six hollow sides is placed at the monitoring point at the bottom of the water body. A water depth sensor is fixed on the top of the frame, and a water pressure sensor is fixed on the bottom, so that the water pressure sensor is exposed in the initial state; the signal transmission direction of the water depth sensor is downward; Get the initial measurement value of the water depth sensor h a0 , and based on the initial measurement value of the water pressure sensor P 0 converted initial water depth value at the location of the water pressure sensor h b0 ; Calculate the real-time water level and h b0 The difference between the initial elevation and the initial elevation of the monitoring point h 0 ; Collect real-time measurement values of water depth sensors and water pressure sensors h am 、 P m , judge the scouring and silting status of the monitoring point, including: Record every moment h am 、 P m , and in h am = h a0 Time conversion P m Corresponding real-time water depth value of the water pressure sensor h bm ; like h am = h a0 , then the monitoring point has no change or is being washed away at the current moment; based on the real-time water level and water depth value of the water pressure sensor at the monitoring point at the current moment h bm Get the elevation value at the monitoring point; like h am < h a0 , then the monitoring point is silted up at the current moment; based on h a0 and h am Get the buried depth of the water pressure sensor, and combine it with the elevation value of the monitoring point at the previous moment to get the elevation value of the monitoring point at the current moment; or, based on the water depth sensor measurement value at the previous moment h am-1 and stated h am Get the current siltation depth and combine it with the elevation value of the monitoring point at the previous moment to get the elevation value of the monitoring point at the current moment.

2. The method according to claim 1, characterized in that The method also includes assigning different identifiers to the status of the monitoring point at each moment; when calculating the elevation value of the monitoring point at the current moment, confirming the scouring or siltation status of the monitoring point at the previous moment by detecting the identifier at the previous moment, so as to select the calculation method of the current monitoring point elevation value.

3. The method according to claim 1, characterized in that The frame is 0.4-0.6 m high.

4. The method according to claim 1, wherein The water pressure sensor and the water depth sensor are respectively fixed to the top and bottom of the frame through brackets.

5. The method according to claim 4, characterized in that The brackets are connected to the top diagonal points and the bottom diagonal points of the frame in a cross-shaped manner, and the water pressure sensor and the water depth sensor are respectively fixed on the intersection points.

6. The method according to claim 1, characterized in that The water depth sensor is fixed directly above the water pressure sensor.

7. The method according to claim 1, characterized in that The frame is a quadrangular pyramid frame.

8. The method according to claim 1, characterized in that The frame is placed parallel to the water flow direction.

9. The method according to claim 1, characterized in that The method also includes placing a plurality of the frames at intervals on the bottom of the water body to measure the scouring and silting status of the range terrain.

10. The method according to claim 1, characterized in that The water depth sensor is an acoustic wave sensor.

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