Implementation method of safe route for flood crossing of ships in water area in front of Guland Dam

Abstract

The invention discloses an implementation method of a safe airline for flood crossing of ships in a water area in front of a Gourand Dam, and relates to the technical field of safe airline construction and implementation. Comprising the following steps: researching water state flow potential of a water area; constructing a coordinate system, partitioning the water area and elaborating the characteristics of each region; constructing a ship kinematics model, and analyzing the safe underlying logic of the safe route; marking safe route coordinates; proposing a method key point for realizing a safe route; and analyzing kinematic logic of wrecks in typical cases of ship out-of-control. According to the scheme, a ship driver can more accurately plan on four routes, and a safe route is realized, so that accidents are reduced. The scheme has the characteristics of universality, operability and convenience in digitization.

Description

Technical Field

[0001] The present invention relates to the technical field of navigation safety, and in particular to a method for realizing a safe route for ships crossing flood season in the waters in front of Gezhouba Dam. Background Art

[0002] Currently, ships sailing on the four routes of the Gezhouba Dam, Dajiang and Sanjiang, must follow the "Rules for the Separation of Navigation Channels for Vessels in the Three Gorges Dam-Gezhouba Waters of the Yangtze River"; ships must also meet the access requirements of the "Flood Season Navigation Flow Standards for the Channel Between the Two Dams of the Three Gorges Dam-Gezhouba Water Conservancy Project of the Yangtze River" (JTS / T180-5-00). Four safe routes can be constructed on these four routes, with coordinates as follows: Figure 1 Many pilots are unaware that these four safe routes can be constructed as planned routes. Even if they do, they often fail to accurately grasp the impact of water levels in different areas on ships, making it difficult to accurately implement safe routes. This can lead to dangerous situations and accidents for ships, seriously threatening the safety of the Gezhouba Hub.

[0003] This invention discloses for the first time the coordinates (ranges) of four universally safe routes for ships entering the waters, proposes a practical method for accurately implementing the routes, and deeply analyzes the underlying logic of this practical solution to ensure ship safety. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to help ship drivers plan and accurately realize a safe route for flood crossing.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for constructing and implementing a safe route for ships to cross floods, comprising the following steps: S1. Analysis of Water Regime and Flow Patterns: Study the water regime during flood season, describe the flow patterns in different areas of the water, clarify the water regime characteristics of rapids, weirs, and flooded shoals formed in specific areas, and the relationship between water regime characteristics and flow rate. Analyze the effects of flow changes on ships on the cross-section of the channel under different flow rates. S2. Regional coordinate setting: Set several straight lines in the water area to divide the water area into multiple areas and describe the characteristics of each area; S3. Kinematic model characteristics: Construct a vector triangle model of flood speed, the ship's inherent speed, and the combined speed of the two. Based on the vector model, quantitatively analyze the impact of subjective and objective factors on the magnitude and direction of the ship's speed during ship motion, and clarify the two characteristics of "subjective active operation affecting ship speed adjustment"; S4. Construction of safe routes: Based on the above analysis and statistical experience data, a safe route suitable for most ships is summarized.

[0006] Preferably, in the water regime flow state analysis step, it is clarified that the flow state of the water area in front of the dam from the upstream end to the downstream end is "weak turbulence, strong turbulence, strong turbulence" or "strong turbulence, strong turbulence, strong turbulence".

[0007] Preferably, in the step of setting the area coordinates, the divided areas include Figure 1 In the middle area ①, there are weirs and flooded shoals on the side close to the center line of the river. There is also a small special area at the weir, which can be called the "downstream ship diversion warning area". It is an important route "selection point" for downstream ships to divert and enter the Dajiang waterway or Sanjiang waterway; there is a strong backflow on the right bank of this area.

[0008] Preferably, in the step of setting the area coordinates, the divided area includes a Figure 1 Area ⑦ is known as the "Devil's Triangle". If a downstream ship mistakenly enters this area, it is easy to be swept by the current to the direction of Erjiang River. If an upstream ship mistakenly enters this area, it is very likely to drift sideways to the direction of Erjiang River.

[0009] Preferably, in the kinematic model feature construction step, it is concluded through velocity vector triangle analysis that in order to make the ship move from a point in the middle of the river channel to a point near the shore, the modulus of the ship's own velocity vector and the angle between it and the flood velocity vector need to be increased. The modulus and angle of the ship's own velocity vector are determined by the ship's own conditions and cannot be increased infinitely instantaneously. Therefore, the driver's operation becomes the only subjective factor.

[0010] Preferably, in the safe route construction step, the safe routes summarized include safe routes for ships entering and exiting specific waterways.

[0011] Preferably, in the safe route for ships entering and exiting a specific waterway, the downstream route coordinates of the safe route for ships entering and exiting a large river include entering the large river channel after passing through several consecutive points in sequence, and the upstream route coordinates include reaching the upstream position after passing through several consecutive points in sequence, so a corresponding speed vector database can be established.

[0012] Preferably, in the safe routes for ships entering and exiting specific waterways, the downlink route coordinates of the safe routes for ships entering and exiting Sanjiang include entering the Sanjiang upper navigation channel after passing through several consecutive points in sequence, and the uplink route coordinates include reaching the upstream position after passing through several consecutive points in sequence, so a corresponding safe route speed vector database can be established.

[0013] The present invention provides a method for constructing and implementing a safe route for ships during flood season, which has the following beneficial effects.

[0014] 1. Safety. By comprehensively and in-depth analyzing the water conditions and flow patterns, accurately dividing the area, and constructing a kinematic model, ship operators can more thoroughly understand the patterns of ship movement in the waters and the impact of complex water conditions on the ship. This allows for more accurate route planning and selection, effectively reducing the possibility of accidents caused by ship deviations or improper response to water conditions, and significantly reducing the incidence of dangerous shipping accidents in the flood season.

[0015] 2. Accuracy. Detailed descriptions of water conditions in different areas and quantitative analysis of kinematic models provide a scientific basis for pilots to navigate complex water conditions. For example, through numerical sequence changes, key adjustments to the velocity vector during vessel movement are clarified, enabling pilots to perform appropriate operations in advance, consistently, and with appropriate intensity. This improves accuracy and stability, eliminating the previous practice of blindly "free" navigation in these waters.

[0016] 3. Universality. The summarized safe routes are applicable to different types of ships and ships with different hardware conditions entering the waters, lowering the technical barriers for ships and pilots to navigate in these waters and demonstrating strong universality.

[0017] 4. Economical. Accurate route planning and effective response to water conditions can reduce energy consumption and equipment wear during navigation, avoiding additional costs such as fuel waste and equipment repairs caused by incorrect navigation or inappropriate response to water conditions, thereby reducing ship operating costs.

[0018] 5. Policy Basis. Detailed water flow analysis, regional division, and kinematic model construction provide scientific data and theoretical support for navigation management departments and relevant decision-making bodies, helping them formulate more reasonable navigation management policies and safety measures, and further optimize the navigation environment in this water area.

[0019] 6. Basic. The present invention provides a method for constructing and implementing a safe route for ships to cross floods. It is not difficult to foresee that if the flood flow rate is further constructed through technical means, 水 Sequence, individual ship's inherent speed 本 The corresponding calculation results are 船 Database, and then with the corresponding safe route 安 By comparing the database, intelligent assisted manual driving or even intelligent driving can be achieved, thus filling the gap of "intelligence" in the safety toolbox of ships sailing in these waters. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and examples: Figure 1 This is the "Coordinate Map of Water Situation, Safe Navigation Routes, and Deviated Navigation Routes in the Water Area in Front of Gezhouba Dam" in the embodiments of the present invention.

[0021] Note: ①, ②, ③, ④, ⑤, ⑥, ⑦ are respectively the partition numbers; the solid arrow lines represent the flowing direction of the flood, and the swirling arrow lines represent the direction of the backwater; the continuous slender dotted lines are the river channel demarcation lines, which respectively form the navigation channels of the main river and the Sanjiang River with the shorelines on both sides; the △OPQ formed by the dotted lines is the devil's triangle area in Area ⑦. Each "shoremark" with fixed longitude and latitude constitutes the framework of the water area coordinate system. The continuous solid arrow lines are the safe navigation routes for downstream, and the intersection points with the straight line are A0…A4 respectively. I and III respectively represent the safe navigation routes for downstream ships entering the main river and the Erjiang River; the continuous dotted arrow lines are the safe navigation routes for upstream, and the intersection points with the straight line are B4…B0 respectively. II and IV respectively represent the safe navigation routes for upstream ships leaving the main river and the Erjiang River; the continuous dotted curves are the schematic diagrams of typical deviated navigation routes.

[0022] Figure 2 This is the "Coordinate Map of the Downstream Navigation Warning Area" in the embodiments of the present invention.

[0023] Note: The coordinate set enclosed by the ellipse on the straight line L1 is the schematic diagram of the downstream navigation warning area; on the right bank side of the M point on the straight line, there are two A1 points. The former is the navigation diversion selection point for downstream ships intending to enter the Sanjiang River (note: according to the navigation rules, downstream ships intending to enter the Sanjiang River should be on the left bank side of the M point, but during the flood season, due to the large flow rate, ships are often washed into the ellipse), and the latter is the navigation diversion selection point for downstream ships intending to enter the main river. The plum blossom-shaped figure is the location of the soaking area, and the backflow on its right bank is indicated by a swirling arrow.

[0024] Figure 3 This is the "Vector Relationship Diagram of Ship Speed" in the embodiments of the present invention.

[0025] Note: V_water is the magnitude and direction of the flood, V_ship_in_calm_water is the magnitude and direction of the ship in still water, and V_ship is the magnitude and direction of the combined ship speed. α and β are respectively the angles between V_ship, V_ship_in_calm_water and the flood. Specific Embodiments

[0026] This part will elaborate in detail on a method for realizing the safe navigation routes of ships in the water area in front of Gezhouba Dam. Through a series of steps, it helps ship drivers plan and implement safe navigation routes more accurately, reducing accidents. The method specifically includes the following steps: I. Analyze the overall water flow situation in the water area Crew members usually refer to the period when the discharge from the Three Gorges Dam lasts for multiple days ≥ 15,000 cubic meters per second as the flood season. During the flood season, the water situation in the 5-kilometer section from the Gezhouba axis to the Sow's Mouth will show a jumpy change with the change of the discharge from the upstream Three Gorges Dam. This change seems disorderly, but the underlying kinematic principle is not complex, and the specific explanation is as follows (see Figure 1 ) Flow patterns above Xiaolantuo: Affected by canyon confluence, the waters between Muzhuzui and Sanyoudong exhibit a pattern of "weak turbulence, strong turbulence, weak turbulence" from left bank to right. From the entrance to the alley, further confluence of the canyon and a narrowing of the right-hand turn radius cause the flow to shift to "strong turbulence, strong-strong turbulence, strong-strong turbulence," resulting in rapid currents. From 150 meters below the alley's entrance mark to the Xiaolantuo shore mark, a floodplain forms during flood season. Simultaneously, weirs and flooded shoals form between the centerline and the right bank. Notably, the intensity of this floodplain is positively correlated with flood discharge: the greater the discharge, the more severe the floodplain, making it a key navigational indicator for determining flow velocity.

[0027] Flow patterns below Xiaolantuo: Below Xiaolantuo, the river water forms a trumpet-shaped channel, gradually diverging into the three rivers. Since the Dajiang and Sanjiang rivers primarily serve as navigable waterways, their flows are relatively low, while the Erjiang river, as a power generation area, experiences extremely high flows. During the off-flood season, the cross-sectional zones of the trumpet exhibit a pattern of "narrow laminar flow, wide strongly turbulent flow, then narrow laminar flow." During high flow conditions, the flow pattern exhibits a pattern of "narrow turbulent flow, wide strongly turbulent flow, then narrow turbulent flow," with the flow pattern positively correlated with flow. Especially when the Erjiang Power Plant is operating at full capacity or opening its sluice gates for flood discharge, the nearshore flows of the Dajiang and Sanjiang rivers are low, and the mainstream flows "rush toward the Erjiang River." At this time, the flow rate (measured as flow velocity) across the channel cross-section exhibits large gradients. This variation creates torque differences between the port and starboard sides, and between the bow and stern. This not only severely weakens the rudder's ability to control the ship's direction, but also creates a thrust force that causes the ship to drift toward the center of the river.

[0028] II. Explain the characteristics of water conditions in each region In order to analyze and describe the situation of this water area more clearly, we first divide it into areas ①-⑦, and the division method is as follows (see Figure 1 ): Draw straight lines L0, L1, and L2 perpendicular to the centerline of the river, passing the Sanyoudong, Xiangzikou, and Xiaolantuo side marks. L0, L1, and L2 intersect the centerline of the river (Note: The river is not a "navigation channel." From this point to the dam axis, the navigation area is divided, with navigation channels distributed on both sides of the river) at K, M, and N, respectively. Draw straight line L3 past the Xiangjiazui No. 1 Hongfu and Qingliangshu side marks, intersecting the centerline of the river at O. Draw straight line L4 past the Dajiang Anti-Siltation Dike Position Marker and the Sanjiang Pilotage No. 7 side mark, intersecting both marks at P and Q. Using these four lines, L1, L2, L3, and L4, divide the area between the line connecting points M, N, O, and P and the right bank into three areas: ①, ②, and ③. Draw the area between the line connecting points M, N, O, and Q and the left bank into three areas: ④, ⑤, and ⑥. The triangle formed by the line connecting points O, P, and Q is area ⑦.

[0029] The characteristics of each region are described in detail as follows: Area ① and Area ④: During the flood season, these two areas have weirs and flooded shoals, and there is a strong backflow between the flooded area and the right bank. The upstream end of this area is the most important "selection point" for downstream ships to enter the Dajiang and Sanjiang rivers. Figure 1 The specific coordinates of the "Downward Flight Alert Area" are shown in Figure 2 According to navigation rules, ships entering and leaving the Three Rivers should navigate through Zone ④. However, due to the heavy flow during the flood season, downstream ships entering the Three Rivers are often washed into Zone ② by the floods and then need to be adjusted from Zone ② to the left bank to Zone ⑥.

[0030] Areas ② and ③: These two zones can be considered extensions of the upper reaches of the Yangtze River. These are the only areas where vessels entering the Yangtze River from Area ① must adjust their routes after selecting their route. They are shaped like a "knife," with sharp turns and a very small turning radius, limiting both maneuvering space and time. Area ③ experiences strong backflow on the right bank, particularly from the "knife edge" to the "knife hook," or segment OP, where there is significant inward drag toward the Second River.

[0031] Areas 5 and 6: These two areas can be considered extensions of the Sanjiang Pilot Channel. Due to the narrow channel and high vessel density, downstream vessels often occupy Area 2 during passing. Area 6, located near the silt-control dike at the boundary between the Second and Third Rivers, i.e., line segment OQ, experiences significant inward drag toward the Second River.

[0032] Area ⑦: This area is known as the "Devil's Triangle" by rescue tugboat crews. Because of the strong inward drag between the waists of the △OPQ, downstream vessels that stray into this area are easily swept toward the second river. Upstream vessels that stray into this area are also at high risk of drifting sideways toward the second river.

[0033] 3. Building a Ship Motion Model Ship motion model: We analyze the ship's motion by constructing a vector triangle model of three speeds: flood, ship's own speed, and the combined speed of the two (e.g. Figure 3 Assume that the ship's speed in still water at various rudder angles and speeds is 本 , the flood flow rate is 水 , the combined ship speed of the two according to the vector law is 船 , α is 船 The angle with the water flow direction, β is 本 and 水 The angle between the two axes is , and |V| is the modulus of the vector. According to the water potential and flow pattern, the kinematic vector model of the ship at a certain time and place can be constructed, namely: 船 = 本 + 水 .

[0034] It can be seen intuitively from the velocity vector triangle that when 水 After the size and direction are determined, 本 The size and direction of the influence 船 The only factor that determines the size and direction of the impact (so it is called the subjective factor). The size of the impact value is as follows: Directional model: α=arccos

(V 2 船 +V 2 水 −V 2 本 ) / 2V 船 V 水

[0035] Establish a database with two ship motion model characteristics along the channel direction: Assume 本 、 水 、 船 The modulus values of the three vectors along the cross-section lines L0…L4 in the channel direction are represented by |V 本 |L0…|V 本 |L4,|V 水 |L0…|V 水 | L4 ,|V 船 |L0…|V 船 |L4 is represented by; the directions are represented by βL0…βL4, γL1…γL4, αL0…αL4. Then, it is not difficult to understand that 本 、 水 、 船 The velocity model and direction model corresponding to each straight line in the channel direction can be expressed by the following three groups (six columns in total): Table 1: List of characteristic numbers of ship motion model along the channel direction

[0036] When a ship moves, the motion model along the channel direction, that is, from L0 to L4 in the table above, has six corresponding series in three groups. These six series have the following two characteristics: Flood flow rate 水 It is determined by the location and is an objective existence that is not controlled by the driver. It follows the water potential and water state characteristics of each area in the aforementioned waters. The driver controls the vehicle speed and steering angle to form 本 , including its size |V 本 | and direction β, with 水 The two are naturally synthesized 船 , is the only subjective factor that determines the speed and direction of the ship. As the driver continues to use the car and rudder on the route, 本 |series and βseries are constantly changing, which directly leads to |V 船 | sequence and α sequence, corresponding changes will occur. This feature can be called the "causal" feature.

[0037] Due to the existence of the "one-to-one correspondence" relationship, it is necessary to promote |V 船 The corresponding changes in the number series, especially the α series, require the pilot to continuously control the vehicle and rudder during navigation; it cannot be achieved at the last moment. To ensure that α matches the planned course before L3, proactive adjustments should be made from L0 and before L3, decisively and promptly. Otherwise, the opportunity for adjustment will be lost. This characteristic can be called the "uncorrected" feature.

[0038] In summary, the two characteristics of "cause and effect" and "unresolved" determine that if the ship is to adjust its displacement from the center of the river to the shore (for example, submersion), if the α value needs to be increased, the only way is to increase |V 本 | and the angle β. And |V 本 The limits of | and β are determined by the ship's own conditions and cannot change infinitely in an instant. Therefore, in the "selection area" area ①, especially the "downward navigation warning area", and the "adjustment areas" ②, ③ and ⑤, ⑥, corresponding operations must be completed decisively.

[0039] 4. Marking safe route coordinates Each ship, due to its own hardware conditions and maneuverability, theoretically has a safe route that matches the water level. The so-called safe route is when the driver uses the best timing and intensity of steering and controls the ship. 本 , thereby controlling 船 , thereby achieving the correct displacement of the ship at each moment and achieving the route with the highest safety factor (its mathematical expression is 安changes in the values of the sequence).

[0040] Combining years of on-duty experience, the Gezhouba Dam rescue tugboat team, together with the local maritime authorities, has summarized routes that are "universal" for most ships entering the dam, which can be used as "safe routes" (Note: The inventor has summarized and written a paper on "safe routes" for the first time, which is expected to be published in a general navigation academic journal in the near future). There are a total of routes I to IV, as follows (reference Figure 1 ): Safe routes for ships entering and leaving major rivers I and II: Coordinates of downlink route I (indicated by red arrows in the color picture and solid arrows in the black and white picture): A0→A1→A2→A3→A4→Dajiang Channel.

[0041] Coordinates of the uplink route II (indicated by the green arrow in the color image and the dotted arrow in the black and white image): B4→B3→B2→B1→B0→sow's mouth.

[0042] Safe routes for ships entering and leaving Sanjiang III and IV: Coordinates of downlink route III (indicated by red arrows in the color map and solid arrows in the black and white map): A0→A1→A2→A3→A4→Sanjiang Upper Pilot Channel.

[0043] Coordinates of the uplink route IV (indicated by the green arrow in the color image and the dotted arrow in the black and white image): B4→B3→B2→B1→B0→sow's mouth.

[0044] 5. Constructing a safe route coordinate sequence Assume that the launching route intersects L0, L2, L3, and L4 at points A1, A2, A3, and A4 respectively, and the launching route intersects L0, L2, L3, and L4 at points B1, B2, B3, and B4 respectively (e.g. Figure 1 shown).

[0045] Assume that the safe speed is 安 , the modulus is |V 安 |, direction is θ, and the safe route coordinate series of the corresponding position can be listed. For the convenience of expression, the safe route series is only explained by taking diving as an example, and the coordinates of each point A0-A4 can be listed (see Table 2).

[0046] Table 2: Ship motion model characteristics and safe routes along the channel direction

[0047] It is important to emphasize again that the size and direction of each point on the ship's safe route constructed based on statistical conclusions, i.e. 安 Two series, universally applicable to ships entering; the driver's task is to control 本 Two sets of sequences, generating 船 Two sets of series, so that they are as close as possible 安 The two sets of number sequences are consistent.

[0048] VI. Implementation Guidelines for Each Route In order to make 船 and 安 The coordinate sequence of the L1-L4 lines should be as consistent as possible. The ship's driver should follow the following guidelines (see Figure 1 、 Figure 2 ): (1) Downstream ship instructions: Maintaining Spacing: Vessels entering the gorge in a single file, i.e., vessels on Routes I and III, must maintain sufficient spacing to avoid potential misalignment when emergency corrections are needed after exiting the gorge. Specific navigation guidelines are as follows: From Pingshan Dam to the "Downstream Separation Warning Area," the distance between the following vessel and the preceding vessel should be no less than 500 meters.

[0049] Entering the Dajiang Channel: Vessels intending to enter the Dajiang Channel, i.e., vessels on Route I, should steer close to the right bank. When entering the "Downstream Diversion Warning Area," A1 (Note: A1 is the general term for the starting point of the downstream diversion. A1 for Route I and A1 for Route III are on the same straight line L1 in the same cross-section, with the former off the right bank and the latter off the left bank) should be chosen as close as possible between the flooded area and the right bank, and the vessel should sail along the right tangent of the flooded area to avoid accidentally entering the backflow and "shooting the hook." When the vessel reaches the entrance of the alley, it is necessary to decisively increase speed to improve vessel control, turn right into the current, and place the backflow on the starboard side of the vessel and the vortex on the port side. Hold the Xiaolan Tuotuo Leng while turning right and heading downstream. Maintain a high position along the way, preventing the vessel from collapsing into the Erjiang River and the anti-siltation dike on the left, and from accidentally entering the backflow on the right. Once the vessel passes the Dajiang anti-siltation dike, the vessel should promptly release the engine and follow the operating instructions for vessels passing through Lock No. 1.

[0050] Entering the Sanjiang Channel: Vessels intending to enter the Sanjiang Channel, i.e., vessels traveling along Route III, should proceed north of the centerline of the channel, following the weir. When a downstream vessel intending to enter the Sanjiang Channel reaches the "Downstream Diversion Warning Area," point A1 should be selected as close as possible to the "flooded" side of the centerline, following the north bank. The vessel should strive to maintain a small angle with the left bank and straighten out as quickly as possible, leaving ample space on the port side for upstream vessels to make way.

[0051] (2) Guidance for embarking vessels: Approaching the shore: All upstream vessels, i.e., those sailing along routes II and IV, must approach the shore and maintain a safe distance from the shore. When approaching the south bank Xiangzikou or the north bank Sanyoudong Anzui, vessels must be careful to prevent the bow from straying into the oblique current or the stern from entering the backflow, to prevent the danger of "slipping".

[0052] Exiting the major river channel: Vessels traveling upstream from the major river channel, i.e., along Route II, should avoid passing at the head of the major river's anti-siltation dike and leave space for downstream vessels intending to enter the major river channel. When exiting the major river channel, vessels should use caution to reduce speed and navigate within the coastal navigation zone according to traffic separation rules.

[0053] Exiting the Sanjiang Pilot Channel: Vessels traveling upstream from the Sanjiang Pilot Channel, i.e., along Route IV, should avoid passing vessels at the Sanjiang Anti-siltation Dike and Sanyoudong, and should leave space for downstream vessels entering the Sanjiang Pilot Channel. After exiting the Sanjiang Pilot Channel, vessels should also exercise caution in reducing speed and proceed upstream along the north bank according to traffic lane separation rules.

[0054] 7. Case Analysis Statistics on ship dangers: According to the statistics of the Gezhouba flood season dam protection and rescue tugboat project team (see Table 3), from 2012 to 2024, a total of 86 ship loss-of-control dangers occurred.

[0055] Table 3: Rescue Cases in Gezhouba Controlled Waters (2012-2024)

[0056] Although the details of the loss of control scenarios vary, the main reasons for the loss of control are: downstream ships mainly deviate from the safe route due to inaccurate selection of point A1 and untimely adjustment in the adjustment area (② or ⑤); upstream ships mainly deviate from the safe route due to improper shore distance selection or failure to use a safe speed. Statistics also show that there are relatively more cases of dangerous situations involving downstream ships. For example, in 2020, there were as many as 8 dangerous situations at Xiangzikou due to inaccurate route selection (see Table 4), and these deviation cases all occurred on the side of the safe route that was off the center of the river, such as Figure 1 The red curve in the middle is shown as a “typical off-course”.

[0057] Table 4: List of ships that strayed and were in distress in the waters in front of Gezhouba Dam during the flood season in 2020

[0058] Analysis of the above ship danger situation (see Figure 1 Typical cases of ships going off-course include: Due to the large gradient of flow across the channel cross section, ships with large angles to the current or ships with poorly matched propulsion systems are highly susceptible to being swept into the Second River by floodwaters. This can manifest as downstream ships experiencing hook strikes, collisions with mountains or silt-control dikes, and being swept directly into the Second River, while upstream ships can experience twisting and turning back into the Second River. The following are three specific case analyses: Case 1 (Ship Hook Shooting): At 2:10 PM on August 16, 2014, with a flow rate of 27,900 cubic meters per second, the fully loaded Chutian 888 was heading downstream for Dajiang No. 1 Ship Lock. At the entrance of Xiangzi, the vessel, fearing being swept into the Erjiang River by floodwaters, drew too close to the south bank, ignoring the backflow from the south bank. This caused the vessel's bow to stray into the backflow, and the stern, affected by the diagonal current, caused the vessel to rapidly turn right and collide with the mountain. After fully steering to port, the vessel's steering was insufficient due to speed limitations, and the drag from the Erjiang River caused it to rapidly drift sideways and downward. The vessel was subsequently rescued by the on-duty tugboat.

[0059] Analysis: This case Figure 1 The cause of the accident can be divided into two stages: the ship hugged the south bank too tightly at the entrance of the alley, the stern was in the rapids, and the bow mistakenly entered the south bank backflow. From the performance of the series, at the L2 line, the ship αL2 seriously deviated from the safe course θA2; when the L2 line transitioned to L3, the ship had to accelerate to ensure navigation efficiency, and after acceleration, |V 船 |L3 is too large, so the time available for adjustment is too short, and the ship has been swept into the Devil's Triangle.

[0060] Case 2 (Ship Collision with Mountain and Dajiang Anti-siltation Dike): At 11:00 PM on August 8, 2012, with a flow rate of 27,900 cubic meters per second, the Guanghua 968, fully loaded, was heading downriver, preparing to enter the Dajiang No. 1 Ship Lock. The vessel's grip on the south bank at the entrance to the alley was loose, deviating from its normal course. After exiting the alley, it was swept toward the Erjiang River. The captain, observing this, made a sharp right turn, attempting to cling to the south bank, but the current proved too strong to control. While sailing at Xiaolantuo, the hook struck the mountain, causing the vessel to break and take on water. The powerful reaction force caused the vessel to bounce back, causing it to collapse again into the Erjiang River. Furthermore, the vessel's severe tilt from the damage and water ingress made it difficult to maneuver. Even after dropping two anchors, the vessel continued to drift down toward the Erjiang Power Plant's Dajiang Anti-siltation Dike, where it again collided with the dike. Thanks to the strenuous efforts of a dam protection tugboat, the Guanghua 968 was finally controlled and towed away from the waters in front of the Gezhouba Dam.

[0061] Analysis: This case Figure 1 See the "typical deviation from the route" on the right bank. The cause of the ship's accident was a typical domino effect. The initial cause was that the ship was not close to the south bank at the entrance of the alley, and it did not turn in time with the bay, so it entered the Devil's Triangle outside Xiaolantuo. At this time, to increase the value of the ship's heading α, it is necessary to increase the ship's β value (i.e., the rudder direction) and at the same time increase |V 本 | (i.e., vehicle speed). However, the β value is limited by the maximum steering angle and cannot be increased indefinitely. A huge increase in |V 本 | means that the ship's inertia increases dramatically, making it difficult to control the ship, resulting in a situation where it "cannot adjust before the Devil's Triangle." The underlying logic reflected in Table 2 is: until the straight line L3, αL3>θA3, |V 船|L3>|V 安 |L3, if αL3 is not satisfied, it should be <θA3, |V 船 |L3 should be <|V 安 |L3 conditions.

[0062] Case 3 (Ship Collision with Qingliangshu Mountain): At 11:00 PM on July 26, 2016, the Luhai 689, heading downstream for Sanjiang No. 2 Lock, ignored the on-duty tugboat's warnings to correct the vessel. Believing it had sufficient maneuverability, and lacking awareness of the force of the Erjiang current, it sailed through the weir, wading through the water and choosing a right-hand course, ultimately being swept toward Erjiang. Upon realizing the vessel was unresponsive, the captain immediately turned hard left, narrowly avoiding the Sanjiang anti-silt dike. However, due to the vessel's excessive inertia, when it turned right again at the dike, attempting to align with the Sanjiang channel, the right-hand turning radius was insufficient, and even with full starboard rudder, it was unable to immediately correct its course. As a result, it struck a slope at Qingliangshu.

[0063] Analysis: This case Figure 1 The left bank in the middle is a "typical deviation from the route", and the physical essence is the same as the previous case.

[0064] Summary: Many shipwrecks occur in the waters in front of Gezhouba Dam, primarily due to significant deviations from the planned safe route before entering the Xiangzikou. Once outside the Xiangzikou, time and distance are extremely limited, making correcting the course increasingly difficult. Escape from the floodwaters often requires full fuel and full rudder control. However, even if a ship manages to escape and enter the Sanjiang or Dajiang pilot channel, excessive inertia and the steep angle with the pilot channel can lead to marine casualties such as "hook-out" and "impact on the embankment." This is the root cause of frequent accidents near the Qingliangshu or Sanjiang anti-siltation dikes on the left bank and the Xiaolantuo or Dajiang anti-siltation dikes on the right bank. When choosing a route at the Xiangzikou, it is important to accurately assess the distances between the three navigational landmarks: the left and right banks, the flooded weirs, and the centerline of the river.

Claims

1. A method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam, characterized in that: The following steps are involved: S1. Analysis of water regime and flow patterns in water areas. Study the water regime during flood season in water areas, explain the flow patterns in different areas of water areas, clarify the water regime characteristics of rapids, weirs, and shoal flooding formed in specific areas, and the relationship between water regime characteristics and flow rate. Analyze the force exerted on ships by flow gradient changes in channel cross sections under different flow rates. S2. Regional coordinate setting: set several straight lines in the water area to divide the water area into multiple areas and describe the characteristics of each area; S3. Kinematic model characteristics: construct a vector triangle model of flood speed, ship's inherent speed, and the composite ship speed of flood speed and ship's inherent speed. Based on the vector formula, analyze the influence of each velocity vector on the magnitude and direction of the ship's speed during ship motion, and explain the characteristics of velocity vector adjustment. S4. Safe route construction: Based on the above analysis, a safe route suitable for ships entering the port is obtained; S5. Based on the above analysis, summarize the essentials of sailing to achieve a safe route.

2. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 1 is characterized in that: In the water regime flow state analysis steps, it is clarified that the flow state of the water area in front of the dam from the upstream end to the downstream end is "weak turbulence, strong turbulence, strong turbulence" or "strong turbulence, strong turbulence, strong strong turbulence".

3. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 1 is characterized in that: In the step of setting the regional coordinates, the divided area includes an area with weirs and shoals near the center line of the river, and a downstream ship diversion warning area exists at the weir in the above-mentioned area. The downstream ship diversion warning area is an important route selection for downstream ships to divert into the Dajiang waterway or the Sanjiang waterway; there is a strong backflow on the right bank side of the downstream ship diversion warning area.

4. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 1 is characterized in that: In the step of setting the regional coordinates, the divided area includes a Devil's Triangle. If a downstream ship mistakenly enters the Devil's Triangle, it is easy to be swept to the direction of Erjiang by the water flow. If an upstream ship mistakenly enters the Devil's Triangle, it will be turned sideways.

5. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 1 is characterized in that: In the kinematic model feature analysis step, it is concluded through velocity vector triangle analysis that in order to move the ship from the middle of the river channel to the nearshore point, the modulus of the ship's own velocity vector and the angle between it and the flood velocity vector need to be increased.

6. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 1 is characterized in that: In the safe route construction step, the safe routes summarized include safe routes for ships to enter and exit specific waterways.

7. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 6 is characterized in that: In the safe route for ships entering and exiting a specific waterway, the downlink route coordinates of the safe route for entering and exiting a major river include entering the major river channel after passing through several consecutive points in sequence, and the uplink route coordinates include reaching an upstream position after passing through several consecutive points in sequence.

8. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 6 is characterized in that: In the safe route for ships entering and exiting the specific waterway, the downstream route coordinates of the safe route for ships entering and exiting Sanjiang include entering the Sanjiang upper pilot channel after passing through several consecutive points in sequence, and the upstream route coordinates include reaching the upstream position after passing through several consecutive points in sequence.

9. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to any one of claims 6 to 8, characterized in that: A series database is established for the ship's own speed vector, flow velocity vector, synthetic ship speed vector and safe route vector when the ship enters and exits a specific channel.

10. The method for realizing a safe navigation route for ships crossing the flood season in the waters in front of Gezhouba Dam according to claim 9 is characterized in that: By comparing and correcting the synthetic ship speed vector and safe route vector database, it serves as a means of digitalization and intelligentization of navigation.

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