CN201610538U - River bottom peeling off simulation test device of hyperconcentrated flood - Google Patents

Abstract

The utility model relates to a river bottom peeling off simulation test device of hyperconcentrated flood, which comprises a test water tank, a simulated riverbed is arranged on the test water tank, and the simulated riverbed consists of the following two layers: the lower layer is a coarse sand layer which adopts coarse-grained fly ash with the median particle diameter of 0.05mm to simulate and has the thickness of 40-45cm, the upper layer is a gumming dirt layer which adopts very fine fly ash with the median particle diameter less than 0.01mm to simulate and has the thickness of 1-3cm, wherein the bed gradient of the simulated riverbed is 4 per mill; and a muddy water inlet section is arranged at the left end of the test water tank, a muddy water outlet section is arranged at the right end, the muddy water outlet section is communicated with a recession pond, the recession pond is communicated with the test water tank through a water tank circulation pipeline, and a flat plate gate is arranged between the muddy water outlet section and the test water tank. The utility model provides a feasible test device for researching a difficult problem of the river bottom peeling off phenomenon of the Yellow River, lays a foundation for understanding the mechanism of the river bottom peeling off phenomenon and establishing a river bottom peeling off erosion index and plays a positive role of the development of the subject of river sediment.

Description

High-sediment flood to expose the river bottom simulation test device

Technical field:

The utility model relates to a hydraulic model, in particular to a simulation test device for exposing the river bottom by a high-sediment flood and simulating the start-up of a high-sediment flood.

Background technique:

In the Xiaobei main stream of the Yellow River and the Weihe River, when floods with high sediment content pass through, the riverbed will often undergo severe concentrated erosion, and after a certain period of siltation and sedimentation in the early stage, a "clay layer" with high density and high strength will occur. , sometimes lifted from the bed, rolled up like a "carpet", exposed to the water surface in pieces, with an area of several square meters or even more than ten square meters, and then broken in a short time , collapsed, and was carried away by the current. The masses vividly call the violent scouring of the riverbed under the condition of high-sediment flood "exposing the river bottom". The Yellow River is "one of the unique phenomena of high-sediment flow movement". Due to the special conditions for the formation of the phenomenon of "exposing the bottom of the river", including water conservancy workers who have been working on the banks of the Yellow River for many years and the people along the Yellow River, few people can really witness the phenomenon of "exposing the bottom of the river", so it is known as the century-old wonder of the Yellow River. known as. Once this happens, the riverbed often undergoes strong undercutting, and in severe cases, a flood peak can wash the riverbed several meters or even nearly ten meters deep. The scouring of "exposing the river bottom" has a strong scouring and trough-making effect, which can well restore the flood capacity of the river; but at the same time, the scouring often causes the migration of the main channel of the river, which makes the project's sliding position constantly change, and easily causes the sinking of the river project. Stings and collapses increase the complexity of flood control and emergency rescue during flood seasons; in particular, due to the large-scale erosion of the river channel, the water level of the big river drops, causing the electromechanical irrigation stations along the river to deflow, which seriously affects the industrial and agricultural production along the river. Since the 1970s, this phenomenon has been highly concerned by water conservancy workers at home and abroad, and a large number of researches have been carried out, which has laid a foundation for people to further understand the phenomenon of "exposing the river bottom". Due to the randomness of the occurrence, it is difficult to obtain the actual measurement data of "exposing the river bottom" with strong followability in practice, which restricts the establishment of the "exposing the river bottom" scour index. For this reason, this problem has to be studied through model experiments. However, there is no relevant report on the simulation of the "exposing the bottom" of the Yellow River.

Invention content:

The purpose of the utility model is to overcome the deficiencies in the prior art and to provide a simulation test of the high-sediment flood that successfully simulates the phenomenon of "exposing the river bottom" of the Yellow River and provides hydraulic parameters for the study of the phenomenon of "exposing the river bottom" in the Yellow River. device.

The technical scheme of the utility model is achieved in that:

Provide a kind of simulation test device of high sediment content flood to expose the bottom of the river, the test device includes a test tank, and a simulated river bed is arranged on the test tank, and the simulated river bed is composed of two layers: the lower layer is made of coarse sand with a median particle size of 0.05mm The coarse sand layer simulated by granular fly ash has a thickness of 40-45 cm, and the upper layer is a "clay layer" simulated by ultra-fine fly ash with a median particle size of less than 0.01 mm, with a thickness of 1-3 cm, simulating the bed surface of the river bed The gradient is 4‰; there is a stirring tank outside the test tank, and a submersible pump is installed in the mixing tank. The submersible pump is connected to the test tank through the tank circulation pipeline, and an electromagnetic flowmeter and an automatic control valve are installed on the tank circulation pipeline. , the left end of the test tank is the muddy water inlet section, and the right end is the muddy water outlet section. There are flat gates between the water tanks. The test water tanks are equipped with water level measuring needles and mobile measuring bridges. The mobile measuring bridges are equipped with flow rate meters, which are used to follow and measure hydraulic sediment parameters at different positions.

The utility model has the following positive effects: due to the strong randomness of the phenomenon of "uncovering the bottom of the river", it is difficult to obtain detailed hydraulic parameters on the prototype. test. The utility model provides a feasible test method and device for studying the difficult problem of "uncovering the river bottom" phenomenon of the Yellow River, and provides a feasible test method for studying the start-up of consolidated cohesive soil, which is a difficult problem in the water conservancy industry; The occurrence mechanism of the "river bottom" phenomenon and the establishment of the "exposing the river bottom" scour index have laid a foundation, which has played a certain positive role in the development of the discipline of river sediment.

Description of drawings:

Fig. 1 is a schematic structural diagram of the test device of the present invention.

Detailed ways:

As shown in Figure 1, the high-sediment flood simulation test device for uncovering the bottom of the river includes a test tank 1, and a simulated river bed (not shown in the figure) is arranged on the test tank. The simulated river bed is composed of two layers: the lower layer is the Coarse sand layer simulated by coarse-grained fly ash with a particle size of 0.05 mm, with a thickness of 40-45 cm, and the upper layer is a "clay layer" simulated by ultra-fine fly ash with a median particle size of less than 0.01 mm, with a thickness of 1-45 cm. 3cm, and the bed surface gradient of the simulated river bed is 4‰; a stirring tank 2 is set outside the test tank 1, and a submersible pump 3 is arranged in the stirring tank 2, and the submersible pump 3 is connected with the test tank 1 through the tank circulation pipeline 4. An electromagnetic flowmeter 5 and an automatic control valve 6 are installed on the tank circulation pipeline 4. The left end of the test tank 1 is the muddy water inlet section 7, and the right end is the muddy water outlet section 8, and the muddy water outlet section is connected with the retreating pool 9. The retreat pool 9 is connected to the test tank 1 through the tank circulation pipeline 4, and a flat gate 10 is provided between the muddy water outlet section 8 and the test tank 1. The test tank 1 is equipped with a water level measuring needle 11 and a mobile measuring bridge 12. A current meter is installed on the mobile measuring bridge 12, which is used to follow and measure hydraulic sediment parameters at different positions.

Using this test device, carry out the simulation experiment of exposing the river bottom by high-sediment flood:

(1), choose three groups of graded fly ash to simulate river bed stratification:

Through prototype site investigation and on-site excavation of the riverbed of the "Jiehedi" section, it is confirmed that the riverbed of the "Jiehedi" section is silted in layers, so the riverbed must also be layered in the test. Using fly ash as the model sand, the fly ash of Zhengzhou Thermal Power Plant was selected as the model sand. After strict hydraulic separation, the ultra-fine fly ash with a median particle size of less than 0.01mm was used to simulate the clay block of the sediment, that is, the "clay layer" ", the fine fly ash with a median particle size of 0.03 mm was used to simulate suspended sand, and the coarse fly ash with a median particle size of 0.05 mm was used to simulate loose bed sand, that is, the coarse sand layer; The coarse-grained fly ash is spread on the bottom of the test tank, which represents the coarse sand layer; the fine-grained fly ash with a thickness of 1-3 cm is spread on the coarse sand layer to simulate the "clay layer".

(2) The casting simulation method of the flocculation and solidification "clay layer", using the casting method to simulate the flocculation and consolidation mode of the "clay block": how to simulate the "clay block" existing on the river bed is also one of the key points of the plan, the natural situation When different floods occur in different tributaries, due to the difference in sediment source, flood sediment content and sediment gradation, the river course will be bedding and silted up. In particular, when the incoming flood has a high content of fine-grained sediment, due to the flocculation of fine-grained sand particles, the sediment will accumulate into blocks, and within a certain period of time, the sediment will gradually consolidate and compact to form " Clay Blocks". In the test, the "clay block" can be simulated by casting.

First, pour the ultra-fine fly ash with a median particle size of less than 0.01mm into a bucket filled with water to make a slurry with a sand content of 800-1000kg/ ^m3 , and then use a mixer to mix the ultra-fine fly ash slurry The mixture is fully stirred evenly, and poured into the space reserved on the coarse fly ash layer in the water tank, after 2 to 3 hours of condensation, it is gradually consolidated to form a cement block, in order to simulate the consolidation into a The "clay layer" of the block, under the condition of moisture content of 10% to 45%, the cohesive force of the superfine fly ash consolidated into the block is about 28-35KPa, which meets the cohesive force of the prototype clay block of 25-40KPa The requirements ensure that the cohesive force of the test clay block itself is basically similar to that of the prototype.

(3) Simulation method of highly sandy flow shaping:

The test must be carried out in a special test device, and the structure of the special test device is shown in Figure 1. The test tank is 31.5m long and 0.80m wide. The inlet of the test system is pumped by a Shanghai Hongqiao submersible sewage pump. The maximum flow rate can reach 54l/s when the water is clean, and the inlet flow rate is controlled by an electromagnetic flowmeter. The water level at the inlet of the sink, the test section and the tailgate is measured by the probe. The test is controlled by a flat gate. After the water exits the gate, it enters the retreat pool, and then it is drawn back to the imported mixing pool to form the self-circulation system of the entire test tank. In the test, fine fly ash with a median particle size of 0.03 mm was added into the mixing tank to form a high-sand content flow with a sand content of 100 to 300 kg/ ^m3 , and the water flow was fully stirred to ensure that the water flow entered the test tank, that is, complete The high-sediment flow simulates the natural high-sediment flood of the Yellow River.

(4) Test method for "exposing the river bottom" of high-sediment floods:

The initial water tank bed surface gradient was 4‰, and the test was started 24 hours after the topography was completed. The inlet sediment concentration was 100kg/m ³ . After the cycle, the inlet flow was continuously increased, and the water flow in the key test section of the tank was observed Changes, and use relevant instruments to measure relevant hydraulic sediment parameters until the phenomenon of "exposing the river bottom" occurs, and obtain the hydraulic sediment parameters of the phenomenon of "exposing the river bottom" of high-sediment floods with strong followability.

The "clay block" should have a certain rigidity: In order to ensure that the sediment is lifted up when the phenomenon of "exposing the river bottom" occurs, the "exposing the river bottom" in the test simulation generally needs to meet a certain rigidity, and the thickness of the block is generally 1cm to 3cm. , the thicker the block, the greater the energy required to lift it.

In the topography preparation in the early stage of the test, coarse-grained fly ash with a thickness of 40-45 cm was laid first, and the surface gradient of the water tank was controlled to be 4‰ by using a section plate, and it was wetted with water and compacted. Reserve a space according to the size of the designed clay block on the coarse fly ash layer, and fill it with ultra-fine fly ash in the future to simulate the clay block.

24 hours after the completion of the terrain paving, the water was released. Before the water was released for the test, adequate preparations were made for the video recording during the test. At the beginning of the test, the inlet control valve was used to control the inlet flow rate of the tank to 20l/s. The water level and flow state in the tank were relatively stable all the time. Only the water flow turbulence at the front end of the cement block in the tank was relatively violent, and the test personnel touched it with their hands. At these positions, it was found that the thin layer of coarse pulverized coal layer sprinkled on the clay block was scoured first, and the front end of the clay block ("lens") also scoured thereupon, and formed scour pits. The local scour of the layer front is very similar to the local scour process of the piers. Due to the strong impact resistance of the clay block, the clay block was not washed away. It lasted for about ten minutes. It was found that the clay block in the tank was not lifted, so the inlet flow was adjusted to 27l/s through the valve. With the increase of the flow rate, Some changes have taken place in the water tank, and the scour pit at the front end of the clay block has further enlarged, but the phenomenon of "uncovering the bottom of the river" has not yet occurred. Therefore, the flow rate continued to increase and was adjusted to 30l/s. The flow rate lasted for only a few minutes, and it was found that the flow state of the test section covered with fine fly ash had a significant change. There seemed to be a water embankment in the tank. Blocks (0.3m x 0.3m x 0.02m) were lifted out of the water by the current. I touched the bottom of the sink with my hand, and found that the place where the fine clay blocks were laid had been uncovered, and the surrounding area had been partially scoured. At the same time, some particularly thin clay blocks were also removed, but they did not come out of the water. When I touched it with my hand, I found that it had been washed away. Finally, the flow rate is also gradually increased to 40l/s, and at this time, some hardened larger cement blocks are also exposed to the water surface. After the cement blocks made by the pawn shop were correspondingly uncovered, the water was cut off to announce the end of the test.

Claims (1)

1. a kind of high sand content flood is revealed the river bottom simulation test device, it is characterized in that: this test device comprises test tank (1), is arranged with simulated river bed on test tank (1), and described simulated river bed is made up of two layers: The lower layer is a coarse sand layer simulated by coarse fly ash with a median particle size of 0.05mm, with a thickness of 40-45cm, and the upper layer is a "clay layer" simulated by very fine fly ash with a median particle size of less than 0.01mm. The thickness is 1-3cm, and the bed surface gradient of the simulated river bed is 4‰; a stirring tank (2) is arranged outside the test tank (1), and a submersible pump (3) is arranged in the agitating tank (2), and the submersible pump ( 3) Connect the test water tank (1) through the water tank circulation pipeline (4), and install an electromagnetic flowmeter (5) and an automatic control valve (6) on the water tank circulation pipeline (4). The left end of the test water tank (1) is The muddy water inlet section (7), the right end is the muddy water outlet section (8), and the muddy water outlet section is connected with the receding pool (9), and the receding pool (9) passes through the tank circulation pipe (4) and the test tank (1 ) are connected, a flat gate (10) is provided between the muddy water outlet section (8) and the test tank (1), and the test tank (1) is equipped with a water level measuring needle (11) and a mobile measuring bridge (12), The mobile measuring bridge (12) is equipped with a current meter, which is used to follow and measure hydraulic sediment parameters at different positions.

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