CN111896366A - A method for simulating multi-structure river bank resistance flow scour - Google Patents

Abstract

The invention relates to a method for simulating multi-structured river bank resistance water flow scouring, and belongs to the technical field of water conservancy. The hydraulic model used in the method includes a water tank, a multi-structure soil placement device, a sink structure of the water tank, a photographing device and a flow velocity measurement device. By using the multi-structure soil placement device, the multi-structure soil can be easily prepared, and at the same time, it is convenient to place or replace. For soil samples, before the test, the mold is easy to disassemble, and the multi-structure soil can be quickly placed in the test part of the water tank, which is convenient to operate and use. Moreover, both the photographing device and the measuring device ensure the timely acquisition and integrity of the test data.

Description

A method for simulating multi-structure river bank resistance flow scour

technical field

The invention relates to a method for simulating a multi-structured river bank resisting water flow scouring by using a hydraulic model, and belongs to the technical field of water conservancy.

Background technique

Most alluvial river beds (river banks) have a typical layered structure, with both a clay layer formed by extremely fine sand and a soft layer formed by coarse sand. Coarse sand and fine sand are often distributed around the upper and lower sides of the clay layer. mezzanine. Due to the existence of the layered structure, different parts of the river bed have different anti-scour properties, resulting in frequent occurrence of deformed river conditions and beach bank collapse, resulting in unstable river conditions, threatening the flood control of the downstream river, and causing a series of problems.

For banks with less clay layers, the soil particle structure is looser and the anti-scour capacity is weak. For river banks composed of medium-dense and slightly dense fine sand or silty and sandy loam, not only the anti-scour ability is very weak, but also the collapsed soil is easily decomposed into loose particles and taken away by water flow; Under the condition of strong and weak soil anti-scour ability, if the anti-scour of the river bank is relatively uniform along the course, the river bank will basically retreat in parallel with a large collapse speed, and the bank line will be in a continuous "zigzag" or "banana shape". ; If the anti-scourability of the river bank is not uniform along the course, in the place where the anti-scour ability is weak and the composition of the river bank is relatively uniform, the river bank will basically retreat in parallel with a large slump speed; The anti-scour of the layer is strong, and the water flow will constantly wash away the soft sandy soil layer below the clay layer, and the shoreline may form a "duck pear shape" or "pocket shape". It can be seen that the multi-structured riverbanks composed of different materials have significantly different impedance effects on the impact of water flow.

Since it is impossible to effectively monitor the morphological response of the multi-structured riparian soil to the scour of water flow in natural rivers, the basic theoretical research can only be carried out by means of model tests. The previous studies on the scour resistance of riparian soils were all carried out for single-structure soils (only for cohesive or non-cohesive sediments), and they did not combine the characteristics of riparian soil and water and sediment movement well. At the same time, its research has fragmented the integrity of the interaction between water flow and river bank to a certain extent.

SUMMARY OF THE INVENTION

The invention provides a method for simulating multi-structure river bank resistance water flow erosion, fully considering the interaction between water flow and river bank soil, and records the erosion process and morphological evolution process of multi-structure river bank soil in multiple directions and clearly, so as to provide information for river management. Provide decision-making basis and technical support. The technical solution of the present invention is as follows:

A method for simulating multi-structure river bank resistance flow erosion, comprising the following steps:

Step 1. Set up the hydraulic model of multi-structure river bank resistance flow scour:

The hydraulic model includes a water tank, a multi-structure soil placement device, a water tank subsidence structure, a photographing device and a flow velocity measuring device. The photographing device includes a side camera arranged on one side of the water tank and an upper camera arranged above the water tank. The soil placement device is arranged in the sink structure of the water tank;

The multi-structure soil placement device includes a sandy soil layer mould and a mixed layer mould; the sandy soil layer mould is composed of wooden boards into five sides, the top is open, the bottom side of the wooden board is 50cm long and 30cm wide, and the four sides of the board are 30cm long and 10cm wide; The two adjacent surfaces are linked by two hinges, and the upper two sides are respectively clamped with wooden clips; the bottom of the sand layer mold is covered with a layer of wooden bottom plate, and the size of the wooden bottom plate is the same as that of the bottom of the sand layer mold, so that it can just fit into the bottom of the sand layer mold. The sandy soil layer mold is suitable; two holes are drilled on both sides of the wooden bottom plate, and an iron wire is passed through each side;

The mixed layer mold is composed of four sides of wooden boards, the upper and lower sides are open, the length of the front and rear sides is 20cm, the width is 10cm, the length of the left and right sides is 10cm, the width is 10cm; The two sides are respectively linked by a hinge, and the upper and lower sides of the mold are respectively stuck by wooden clips;

The sinking structure of the water tank is arranged in the middle part of the water tank and is used for placing multi-structure soil;

Described flow velocity measuring device comprises ADV three-dimensional flow velocity meter arranged at each measuring section;

Step 2: Make multi-structure soil samples:

First, assemble the sand layer mold, then lay the wooden bottom plate on the bottom of the inner side of the sand layer mold, straighten the iron wires on both sides and place them on the side walls of the wooden boards on both sides, put in the sand, tamp them, and then use the wooden clips to separate them. stuck on top of the sand layer mold;

Then place the mixed layer mold in the sand layer mold containing the sand sample, and place sand and clay in the mixed layer mold in turn. The thickness of the soil sample is determined according to the test requirements. Remove the wooden clips and hinges, and remove the boards around the soil sample, leaving only the wooden bottom plate to support the prepared multi-structure soil; place the prepared multi-structure soil in the sink structure of the sink;

Step 3: Drain water from the sink and record the test process:

Debug the side camera, the upper camera and the ADV three-dimensional flow meter, turn on the water flow, and set the flow rate. After the water flow is stable, the timing starts and the side camera and the upper camera are turned on to shoot at the same time.

The present invention has the following remarkable effects and advantages:

(1) Simple structure and convenient operation

The multi-structure soil prepared by the method takes the dual-structure soil as an example, the upper part is a mixed layer mold, and the lower part is a sand soil layer mold. Among them, the mixed layer mold can be placed with multi-layer structural soil according to the requirements of test simulation. Using the device, it is easy to prepare multi-structured soil, and at the same time, it is convenient to place or replace soil samples. Before the test, the mold is easy to disassemble, and the multi-structured soil can be quickly placed in the test part of the water tank, which is convenient to operate and use.

(2) The test and measurement system is complete

The entire test device laid out by this method is equipped with cameras on one side and directly above the soil body. During the test, the morphological changes of soil layers with different structures that resist water flow under the action of the same water flow can be clearly photographed; Clearly record the suspended state of the sand layer being washed by water flow at different times. The top camera can clearly record the cracks that occur when the lower sand layer is washed out to a certain width, and the upper clay layer loses support and itself resists water flow. and collapse, as well as record the final surface morphology of soils of different structures subjected to water erosion during the whole test process; a flow meter is set up on the measuring section to measure the change of water flow speed around the soil at different times; both the photographing device and the measuring device are used. This ensures the timely collection and integrity of test data.

Description of drawings

Fig. 1 is the sandy soil layer mould development plan view that the present invention adopts;

Fig. 2 is the three-dimensional view of the sand layer mould adopted by the present invention;

Fig. 3 is the schematic diagram of the soil supporting device inside the sand layer mould adopted by the present invention;

Fig. 4 is the mixed layer mould schematic diagram that the present invention adopts;

Figure 5 is a perspective view of the multi-structure soil placement device used in the present invention (no planks are laid at the bottom);

Figure 6 is a perspective view of the multi-structure soil placement device used in the present invention (laying wooden boards at the bottom);

Fig. 7 is the front view of the sink structure of the sink adopted in the present invention;

8 is a front view of the overall arrangement of the hydraulic model adopted in the present invention;

Among them, 1 is a wooden board, 2 is a hinge, 3 is a wooden clip, 4 is a wooden base plate, 5 is a hole, 6 is an iron wire, 7 is a sand layer mold, 8 is a mixed layer mold, 9 is the sink structure of the sink, 10 is the water tank, 11 is the side camera, 12 is the upper camera, 13 is the ADV three-dimensional flow meter, 14 is the sand layer, and 15 is the clay layer.

Detailed ways

The present invention will be described in detail below in conjunction with accompanying drawings 1-8.

A method for simulating multi-structure river bank resistance flow scour, comprising:

Step 1. Set up the hydraulic model of multi-structure river bank resistance flow scour:

The hydraulic model includes a water tank 10, a multi-structure soil placement device (shown in Figures 1-6), a water tank subsidence structure 9 (Figure 7), a photographing device and a flow velocity measuring device 13. The photographing device includes a device arranged on one side of the water tank. The side camera 11 and the upper camera 12 arranged above the water tank, the multi-structure soil placement device is arranged in the sink structure 9 of the water tank;

The multi-structure soil placement device (Figs. 1-6) includes a sand layer mold 7 and a mixed layer mold 8. The sandy soil layer mould 7 is composed of wooden boards 1 into five surfaces, the top is open, the bottom board is 50cm long and 30cm wide, and the four boards are 30cm long and 10cm wide; There are a total of five wooden boards 1. In order to make the mold more secure, the upper two sides are respectively clamped with wooden clips 3. A layer of wooden base plate 4 is laid on the bottom of the base plate 4, the size is the same as that of the bottom of the sand layer mold 7, and it is suitable to fit into the sand layer mold 7; , as shown in Figure 3. The sandy soil layer mould 7 is assembled, then the wooden base plate 4 is laid flat on the inner bottom of the sandy soil layer mould 7, the iron wires 6 on both sides are straightened and placed on the side walls of the wooden boards 1 on both sides, and the prepared sandy soil sample is placed at this time, Compact, and then use wooden clips 3 to clip above the sand layer mold, one on each side of the left and right sides;

The mixed layer mold 8 is composed of four sides of the wooden board 1, and the upper and lower sides are open. The two adjacent surfaces are respectively linked by a hinge 2, and the upper and lower sides of the mold are respectively clamped by wooden clips 3 to fix the mold and make the mold more tightened, as shown in Figure 4;

The sinking structure 9 of the water tank (Fig. 7) is arranged in the middle part of the water tank 10, and it is suitable to just put down the sandy soil layer, which is used to place the layered soil body;

The shooting device includes a side camera 11 and an upper camera 12 respectively set up on one side of the water tank and directly above the layered soil. The inner image is clear and the size is appropriate;

Said flow velocity measuring device means that measuring sections are respectively arranged at the front, rear and middle of the multi-structure soil body in the water tank 10 at suitable positions, and an ADV three-dimensional flow meter 13 is erected at each measuring section to measure different time points respectively. Changes of water flow structure around multi-structure soil;

Step 2: Make multi-structure soil samples:

When preparing multi-structure soil, the sandy soil layer mold 7 is all placed with sandy soil samples, and the mixed layer mold 8 can be placed in multiple layers of soil samples with different structures according to the test requirements;

First, assemble the sand layer mold 7, then lay the wooden bottom plate 4 on the inner bottom of the sand layer mold 7, straighten the iron wires 6 on both sides and place them on the side walls of the wooden boards 1 on both sides, put in the sand, tamp it, and use it again. The wooden card strips 3 are respectively stuck above the sand layer mold, one on each side of the left and right sides;

Then, place the mixed layer mold 8 in the sandy soil layer mold 7 containing the sandy soil samples, and place sand, clay and other soil samples in the mixed layer mold 8 in turn. , the preparation of 15. When the prepared multi-component structure soil meets the requirements of the scouring test, remove the wooden clips 3 on the mold, remove the hinges 2, and remove the surrounding wooden boards 1 of the soil sample. At this time, only the wooden bottom plate 4 is left to hold the prepared multi-component Structural soils 14, 15; the prepared multi-structure soils 14, 15 are placed in the sink structure 9 of the water tank;

Step 3. Drain water from the water tank 10, and record the test process:

Debug the side camera 11, the upper camera 12 and the ADV three-dimensional flow meter, turn on the water flow, and set the flow rate. After the water flow is stable, the timing starts and the erected side camera 11 and the upper camera 12 are turned on to shoot at the same time.

Claims (1)

1. a method for simulating multivariate structure river bank resistance flow erosion, is characterized in that, comprises the steps: Step 1. Set up the hydraulic model of multi-structure river bank resistance flow scour: The hydraulic model includes a water tank 10, a multi-structure soil placement device, a water tank subsidence structure 9, a photographing device and a flow velocity measuring device 13. The photographing device includes a side camera 11 arranged on one side of the water tank and an upper part above the water tank. The camera 12 and the multi-structure soil placement device are arranged in the sink structure 9 of the water tank; The multi-structure soil placement device includes a sandy soil layer mould 7 and a mixed layer mould 8; the sandy soil layer mould 7 is composed of a wooden board 1 into five surfaces, the top is open, the bottom board is 50cm long and 30cm wide, and the four sides of the board are 30cm long. The width is 10cm; each adjacent two surfaces are linked by two hinges 2, and the upper two sides are respectively stuck with wooden clips 3; the bottom of the sand layer mold 7 is covered with a layer of wooden bottom plate 4, and the size of the wooden bottom plate 4 is the same as that of the sand layer. The bottom of the mold 7 is the same, and it is suitable to just fit into the sand layer mold 7; two holes 5 are drilled on both sides of the wooden base plate 4, and an iron wire 6 is worn on each side; The mixed layer mold 8 is composed of four sides of the wooden board 1, and the upper and lower sides are open. The two adjacent surfaces are respectively linked by a hinge 2, and the upper and lower sides of the mold are respectively clamped by wooden clips 3; The sinking structure 9 of the water tank is arranged in the middle part of the water tank 10 for placing multi-structure soil; Described flow velocity measuring device comprises ADV three-dimensional flow velocity meter arranged at each measuring section; Step 2: Make multi-structure soil samples: First, assemble the sand layer mold 7, then lay the wooden bottom plate 4 on the inner bottom of the sand layer mold 7, straighten the iron wires 6 on both sides and place them on the side walls of the wooden boards 1 on both sides, put in the sand, tamp it, and use it again. The wooden clips 3 are respectively stuck above the sand layer mould 7; Then the mixed layer mold 8 is placed in the sand layer mold 7 containing the sand sample, and sand and clay are placed in the mixed layer mold 8 in turn. The thickness of the soil sample is determined according to the test requirements. When removing the wooden clips 3 and hinges 2, remove the surrounding boards 1 of the soil sample, and only the wooden bottom plate 4 is left to support the prepared multi-structure soil bodies 14, 15; place the prepared multi-structure soil bodies 14, 15 in the sink structure 9; Step 3. Drain water from the water tank 10, and record the test process: Debug the side camera 11, the upper camera 12 and the ADV three-dimensional flow meter, turn on the water flow, and set the flow rate.

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