Driftwood collection method

Abstract

The present invention relates to a method for collecting driftwood, which belongs to the field of hydraulics and includes the following steps: S1: uniformly mixing pebbles, coarse sand, and clay according to a mass ratio and placing them into a nylon bag, where a single nylon bag constitutes a spur dike. S2: setting up a spur dike structure in a tributary according to design parameters, with one end of the spur dike structure located in the tributary's channel, not connected to the riverbank, and the other end connected to the tributary's bank farther downstream, where the downstream refers to the channel after the main stream and tributary meet. Design parameters include: the ratio of the spur dike structure length (l) to the tributary channel width (D); the angle θ between the spur dike structure and the tributary bank; the distance from the spur dike structure's connection point with the bank to the confluence; and the height of the spur dike structure. S3: deploying a net in the separation zone of the river channel after the main stream and tributary meet, collecting driftwood diverted by the spur dike structure in the separation zone. This method utilizes the spur dike structure to guide driftwood into the separation zone, making it convenient for salvage personnel to salvage and collect driftwood in the separation zone.

Description

Technical Field

[0001] The invention relates to the field of hydraulics, and in particular to a method for collecting driftwood. Background Art

[0002] Along riverbanks, felled or fallen trees can be carried downstream by flash floods or debris flows, forming driftwood. In recent years, riverbank erosion and landslides have generated an increasing amount of driftwood, which increases the overall risk of flooding. Furthermore, driftwood can impact hydraulic structures. Furthermore, driftwood often accumulates near bridge piers, hydropower stations, and other hydraulic structures, causing blockages. This reduces the flow capacity of the river channel and the cross-sectional area of ​​the waterway, impacting the power generation head of the hydropower station and reducing the economic benefits of the water conservancy project. It can even cause excessive water pressure, seriously threatening the safe operation of hydraulic structures.

[0003] There are two main measures to reduce the impact of driftwood: (1) installing driftwood guide piles, driftwood removal devices and other protective measures at places prone to blockage, such as bridge tunnels; and (2) installing driftwood interception measures at key sections of the river.

[0004] Both methods intercept driftwood in low-velocity areas such as near bridge piers and culverts, or along river bends and concave banks. They are unable to intercept driftwood at river confluences. However, river confluences are key control nodes in plain river networks. Intercepting and collecting driftwood at these confluences can prevent driftwood from entering hydraulic structures, further protecting them and making them highly valuable for widespread application.

[0005] The high flow rate at river confluences makes it difficult to collect and salvage driftwood. Although the flow rate in the separation zone at river confluences is slow and the water has less swirling, making it easier to salvage driftwood, in actual salvage operations, driftwood cannot enter the separation zone, so using the separation zone to collect driftwood still needs to be studied. Summary of the Invention

[0006] In order to overcome the deficiencies in the prior art, the present invention proposes a driftwood collection method, which aims to solve the technical problem of how to make the driftwood at the confluence of rivers enter the separation zone as much as possible and be collected.

[0007] In order to achieve the above object, the present invention provides a driftwood collection method, characterized in that it comprises the following steps:

[0008] S1: Pebbles, coarse sand, and clay are uniformly mixed according to mass ratio and placed into nylon bags. A single nylon bag is a spur dike unit. S2: According to the design parameters, spur dike units are stacked in the tributary. Multiple spur dike units form a spur dike structure. One end of the spur dike structure is located in the tributary river channel and is not connected to the river bank. The other end is connected to the tributary river bank far downstream. The downstream refers to the river channel after the main stream and tributary meet. The design parameters include: the ratio of the spur dike structure length l to the tributary river channel width D, the distance from the connection point of the spur dike structure to the intersection, the angle θ between the spur dike structure and the tributary river bank, and the height of the spur dike structure.

[0009] From a bird's-eye view, the connection point between the spur dike and the riverbank is marked as point O, the intersection point of the tributary and the main stream is marked as point A, and the end of the spur dike is marked as point B. The angle θ between the spur dike and the tributary riverbank is ∠AOB;

[0010] Furthermore, in step S1, the spur dike monomer is prepared by mixing pebbles, coarse sand and clay in a mass ratio of (0-2.5):(0-2.5):(5-10), placing the mixture into nylon bags and arranging the mixture.

[0011] Furthermore, in step S2, the ratio l / D of the length l of the spur dike structure to the width D of the tributary river channel is in the range of 30%-50%, the angle θ between the spur dike structure and the tributary river bank is in the range of 45°-75°, the distance between the spur dike structure and the intersection is maintained at 1-3 meters, and the height of the spur dike structure exceeds the water surface by greater than or equal to 10 centimeters.

[0012] Furthermore, in step S3, a string of pontoons is placed along the river channel after the main stream and the tributary meet. The trajectory of the string of pontoons is arranged along the edge of the separation zone. The barrier net is hung at the lower end of the string of pontoons and submerged under the water surface. One end of the string of pontoons is fixed to the river bank, and a long pole is fixed to the bottom of the other end; one end of the long pole is fixed to the pontoon, and the other end is inserted into the river bottom and fixed to the river bottom.

[0013] Beneficial effects:

[0014] This application sets up a dike structure to divert the driftwood to the separation area. Based on the hydrological characteristics of the slow water flow in the separation area, it is convenient for salvage workers to collect and salvage the driftwood. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the experimental setup for Experiment 1;

[0016] Figure 2 This is a schematic diagram of the experimental setup for Experiment 2;

[0017] Figure 3 This is a schematic diagram of the experimental setup for Experiment 3;

[0018] Figure 4 This is a schematic diagram of the positional relationship between the dam and the river channel;

[0019] Figure 5 It is a line chart of Table 1.

[0020] 1. Separation area; 2. Blocking net; 3. Buoy; 4. Long pole; 5. Spur dike structure. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] A driftwood collection method comprises the following steps:

[0023] S1: Pebbles, coarse sand and clay are evenly mixed according to the mass ratio and put into nylon bags. A single nylon bag is a single spur dike unit.

[0024] S2: According to the design parameters, spur dike units are stacked in the tributary. Multiple spur dike units form a spur dike structure. One end of the spur dike structure is located in the tributary river channel and is not connected to the river bank. The other end is connected to the river bank far away from the downstream of the tributary. The downstream refers to the river channel after the mainstream and tributary meet. The design parameters include: the ratio of the spur dike structure length l to the tributary river channel width D, the distance from the connection point of the spur dike structure and the river bank to the intersection, the angle θ between the spur dike structure and the tributary river bank, and the height of the spur dike structure.

[0025] like Figure 1 As shown in the figure, from a bird's-eye view, the connection point between the spur dike structure and the river bank is marked as point O, the intersection point of the tributary and the main stream is marked as point A, the end of the spur dike structure is marked as point B, and the angle θ between the spur dike structure and the tributary river bank is ∠AOB.

[0026] S3: Deploy a net in the river separation area after the main stream and tributary meet, and collect driftwood that has been diverted through the spur dike structure in the separation area.

[0027] In step S2, the ratio of the length l of the spur dike structure 5 to the width D of the tributary river channel is in the range of 30%-50%, the angle between the spur dike structure 5 and the tributary river bank is in the range of 45°-75°, the distance between the spur dike structure 5 and the intersection is maintained at 1 meter-3 meters, and the height of the spur dike structure 5 exceeds the water surface by greater than or equal to 10 centimeters.

[0028] In step S1, the spur dike structure is constructed by mixing pebbles, coarse sand, and clay in a mass ratio of (0-2.5):(0-2.5):(5-10), placing the mixture in nylon bags, and then arranging the bags. The nylon bags filled with pebbles, coarse sand, and clay are then stacked at the confluence of the rivers to form the spur dike structure 5.

[0029] In step S3, a string of buoys 3 is placed along the river channel after the main stream and tributary meet. The trajectory of the string of buoys 3 is arranged along the edge of the separation zone 1. The above-mentioned barrier net 2 is hung at the lower end of the string of buoys 3 and submerged under the water surface. One end of the string of buoys 3 is fixed to the river bank, and the bottom end of the other end is fixed to a long pole 4. One end of the long pole 4 is fixed to the buoy 3; the other end is inserted into the riverbed and fixed to the riverbed. Figure 4 As shown. Thus, the purpose of fixing both ends of the buoy 3 is achieved. The length of the buoy 3 is 10%-20% of the width of the river after the main stream and tributaries meet, and the aperture of the barrier net 2 is 5-10 cm.

[0030] The separation zone refers to the supporting effect of the tributary on the water surface upstream of the mainstream and the backflow zone that appears downstream of the confluence.

[0031] Since the engineering workload of this application is large and difficult to implement and test in a short period of time, in order to illustrate the effect of the above-mentioned collection method, it was decided to conduct a proportional simulation in a laboratory water tank based on the actual situation.

[0032] Experimental setup and conditions:

[0033] This experiment involved a 10-meter-long flume. The main stream and tributary flow merged 3 meters upstream of the flume, at a 60° angle. Both the main stream and tributary were 3 meters long and 0.32 meters wide. The resulting channel, after the confluence of the main stream and tributary, was 7 meters long and 0.42 meters wide.

[0034] Water tanks were installed upstream of both the main and tributary streams, connected to flow meters, pumps, and valves to maintain a 1:1 flow ratio between the main and tributary streams. The water level in both streams was maintained at 20 cm. Wooden sticks of uniform size were used to represent actual driftwood.

[0035] The model of the spur dike structure 5 is set at a distance of 15 cm from the intersection, and the model of the spur dike structure 5 is 1 cm above the water surface.

[0036] Experiment 1:

[0037] According to the method in step S2 above, the ratio of the length l of the spur dike structure 5 model to the width D of the tributary river channel is set to 30%, and the angle between the spur dike structure 5 model and the tributary bank is changed to 45°. Figure 1 shown.

[0038] Wooden sticks are placed 1.5 meters away from the confluence of the mainstream and tributary, with random angles.

[0039] In Experiment 1, wooden sticks were repeatedly placed and the probability of the sticks entering separation zone 1 was calculated.

[0040] Experiment 2:

[0041] According to the method in step S2 above, the ratio of the spur dike structure 5 model l to the tributary river width D is set to 40%, and the angle between the spur dike structure 5 model and the tributary bank is changed to 60°. Figure 2 shown.

[0042] Wooden sticks are placed 1.5 meters away from the confluence of the mainstream and tributary, with random angles.

[0043] In Experiment 2, wooden sticks were repeatedly placed and the probability of the sticks entering separation zone 1 was calculated.

[0044] Experiment 3:

[0045] According to the method in step S2 above, the ratio of the length l of the spur dike structure 5 model to the width D of the tributary river channel is set to 50%, and the angle between the spur dike structure 5 model and the tributary bank is changed to 75°. Figure 3 shown.

[0046] Wooden sticks are placed 1.5 meters away from the confluence of the mainstream and tributary, with random angles.

[0047] In Experiment 3, wooden sticks were repeatedly placed and the probability of the sticks entering separation zone 1 was calculated.

[0048] Experiment 4:

[0049] A set of control cases was set up, in which no spur dike structure 5 was set up at the confluence of the mainstream and tributary.

[0050] Wooden sticks are placed 1.5 meters away from the confluence of the mainstream and tributary, with random angles.

[0051] In Experiment 4, wooden sticks were repeatedly placed and the probability of the sticks entering separation zone 1 was calculated.

[0052] After repeated experiments 1-4, the probability of the stick entering the separation zone 1 was statistically analyzed, which is related to the ratio of the length l of the spur dike structure 5 to the width D of the tributary river channel (width ratio) and the angle between the spur dike structure and the tributary bank, as shown in the following figure: Figure 5 , as shown in Table 1.

[0053] Table 1: Probability of the stick entering the separation zone at various width ratios and angles

[0054]

[0055] According to the data in Table 1, compared with Experiment 4, the probability of the wood sticks entering the separation zone in Experiments 1-3 increased to approximately 7%, 14%, and 30%, respectively. This shows that the method for collecting driftwood in a tributary proposed in this application significantly increases the probability of driftwood staying in the separation zone.

[0056] Furthermore, as can be seen from Table 1, the probability of the stick remaining in the separation zone is highest when the width ratio is 50% and the angle is 75 degrees. Based on common knowledge among those skilled in the art, the separation zone has the hydraulic properties of low flow velocity and minimal water swirl, making it easier to collect and salvage driftwood. Since this application can increase the probability of driftwood entering the separation zone, it can also facilitate salvage personnel in the separation zone.

[0057] The method of the present application increases the probability of drift wood in nature entering the separation zone by setting up a spur dike structure, thereby achieving more efficient collection of drift wood.

[0058] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A driftwood collection method, characterized in that: The following steps are included: S1: Pebbles, coarse sand and clay are evenly mixed according to the mass ratio and put into nylon bags. A single nylon bag is a single spur dike unit. S2: According to the design parameters, spur dikes are stacked in the tributary. Multiple spur dikes form a spur dike structure. One end of the spur dike structure is located in the tributary channel and is not connected to the river bank. The other end is connected to the tributary bank far downstream. The downstream refers to the river channel after the main stream and tributary meet. The design parameters include: the ratio of the spur dike structure length l to the tributary channel width D, the distance from the connection point of the spur dike structure to the river bank to the intersection, the angle θ between the spur dike structure and the tributary bank, and the height of the spur dike structure. From a bird's-eye view, the connection point between the spur dike and the riverbank is marked as point O, the intersection point of the tributary and the main stream is marked as point A, and the end of the spur dike is marked as point B. The angle θ between the spur dike and the tributary riverbank is ∠AOB; S3: Deploy a net in the river separation area after the main stream and tributary meet, and collect driftwood that has been diverted by the spur dike in the separation area; In step S2, the ratio l / D of the length l of the spur dike structure to the width D of the tributary river channel is set to 50%, the angle θ between the spur dike structure and the tributary river bank is set to 75 degrees, the distance between the connection point of the spur dike structure and the river bank and the intersection is maintained at 1-3 meters, and the height of the spur dike structure exceeds the water surface by greater than or equal to 10 centimeters.

2. A driftwood collection method according to claim 1, characterized in that: In step S1, the spur dike monomer is prepared by mixing pebbles, coarse sand and clay in a mass ratio of (0-2.5):(0-2.5):(5-10), placing the mixture into nylon bags and arranging the mixture.

3. A driftwood collection method according to claim 1, characterized in that: In step S3, a string of buoys is placed along the river channel after the main stream and the tributary meet. The trajectory of the string of buoys is arranged along the edge of the separation zone. The barrier net is hung at the lower end of the string of buoys and submerged under the water surface. One end of the string of buoys is fixed to the river bank, and a long pole is fixed to the bottom of the other end; one end of the long pole is fixed to the buoy, and the other end is inserted into the riverbed and fixed to the riverbed.

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