Mountain river fluid bed physical model bed load layering and zoning simulation method

Abstract

The invention provides a mountain river fluid bed physical model bed load layering and zoning simulation method, which comprises the following steps: carrying out sediment sampling on a simulated river reach, dividing sediment types, and layering and zoning sediment distribution; calculating representative gradation of each type of sediment, dividing sediment components and counting the proportion of each component; constructing a sediment similarity scale calculation formula, calculating the particle size of the model sand of each component, and preparing the model sand of each type of sediment; a physical model is manufactured, pre-prepared model sand is laid according to the sediment type of each layer area, and movable bed test verification is carried out. According to the method, accurate simulation of the movement rule of the bed load under the complex substrate condition of the mountain river is achieved, the problems of model sand selection, model sand laying and accurate simulation of the bed load in the moving bed physical model are effectively solved, and the design method of the moving bed physical model is enriched and developed.

Description

Technical Field

[0001] The invention belongs to the field of mountain river hydrodynamic sediment simulation methods, and in particular relates to a mountain river fluidized bed physical model bed load stratification and zoning simulation method. Background Art

[0002] Mountain rivers have fast flow rates and steep slopes, and the sediment particle size on the bed is relatively large, usually dominated by bedload movement; affected by the irregular boundaries on both sides, the river flow is usually alternating between shallows and deep troughs, and the bed sediment distribution is complex and diverse. In the simulation of bedload movement in the moving bed physical model, setting a single bed is difficult to reflect the complex bed sediment distribution on site, and setting a bed sediment distribution that is completely consistent with the site is difficult to achieve in actual operation. How to simulate bedload movement under complex bed sediment distribution in the moving bed physical model is still a difficult problem in the study of water and sediment dynamics in mountainous rivers. Summary of the invention

[0003] The present invention aims to solve the problems faced by traditional moving bed physical model design, such as difficulty in selecting suitable model sand to simulate the bed load movement and complex bed distribution of mountain rivers, and provide a bed load stratification and zoning simulation method for a mountain river moving bed physical model. The purpose is to provide a scientific and effective method for simulating the bed load movement law of a mountain river moving bed physical model.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A bed load stratification and partitioning simulation method for a mountain river mobile bed physical model, comprising: Take bottom sediment samples from the simulated river section, classify the sediment types of the sampled body according to the sediment particle size, and divide the bottom sediment distribution into layers and zones; Calculate the average gradation of each type of sediment as the representative gradation of the corresponding type of sediment, group the sediment particle size of each representative gradation and calculate the proportion of each particle size component; Under the condition of similar sediment initiation, a sediment particle size ratio is established; the statistical proportion of each particle size component is divided by the sediment particle size ratio to obtain the proportion of each particle size component of the model sand, and model sand of each type of sediment is prepared according to the proportion of each particle size component of the model sand; A moving bed physical model of the simulated river section is constructed, and the prepared model sand is laid according to the sediment types in each layer and area.

[0005] To optimize the above technical solutions, the specific measures taken also include: Furthermore, the bottom sediment sampling of the simulated river section is specifically: Arrange multiple sampling points on the riverbed surface along the center line of the river; Drilling exploration is carried out vertically on the riverbed, with the drilling point located on the center line of the river channel; the surface thickness is calculated based on the drilling samples, and the deep layer below the surface is sampled once.

[0006] Furthermore, the classification of the sediment types of the sampling body according to the sediment particle size is specifically as follows: The sampled bodies were sieved and the grading curves of the sampled bodies were drawn. The median particle size of the sampled bodies was obtained using the grading curves. According to the median particle size, the sampled bodies were divided into three sediment types: deep trough type, shallow shoal type and coarsened type according to the sediment particle size standards of 0.1-1mm, 1-10mm and 10-70mm.

[0007] Furthermore, the distribution of the bottom sediment is divided into layers and zones, specifically: The riverbed is divided into two layers vertically: the upper layer is the surface layer, the thickness of which is determined according to the surface thickness of the drilling sampling statistics; the lower layer is the deep layer, the thickness of which is determined according to the maximum scouring and silting thickness; For the surface layer, the surface layer was divided into zones according to the type of sediment in each sampling body in the surface layer.

[0008] Furthermore, the average gradation of each type of sediment is calculated as the representative gradation of the corresponding type of sediment, and the calculation formula is as follows: ; in, for n The average gradation of the samples of the same sediment type represents the average gradation of the corresponding type of sediment; For the i The gradation of the sample volume; n is the number of samples of the same sediment type, x is the sediment particle size, b To be infinitely close to x The approach coefficient, 0.1mm <b<x<100mm; The sediment particle size grouping for each representative gradation is to group the calculated representative gradations into particle size groups according to 0.1-1 mm, 1-5 mm, 5-20 mm and 20-70 mm respectively.

[0009] Furthermore, the calculation formula of the sediment particle size ratio is: ; in, is the sediment particle size ratio, is the sediment bulk density ratio, is the dry bulk density ratio of sediment, is the vertical scale of the model.

[0010] Furthermore, the construction of the moving bed physical model of the simulated river section is specifically as follows: Determine the model's horizontal scale based on the simulation scope and laboratory scale , combined with the model vertical scale , a moving bed physical model of the simulated river section was constructed, the model elevation error was within 1 mm, and the model had grooves reserved for laying model sand.

[0011] Furthermore, the model sand prepared according to the type of sediment in each layer and each area is specifically: The model sand is laid in two layers, the lower layer is laid first, and the lower layer is laid according to the sediment type of the deep sampling body during drilling exploration, and the laying thickness is greater than the maximum scouring and silting thickness; the upper layer is laid secondly, and the upper layer is laid according to the zoning of the surface layer, and the laying thickness is the surface thickness calculated by drilling sampling statistics.

[0012] Furthermore, after laying the prepared model sand, a moving bed test is conducted on the moving bed physical model of the simulated river section under typical annual flow conditions, specifically: According to the flow similarity scale and scouring and silting time scale Release the flow to verify the scouring and silting of the riverbed of the dynamic bed physical model of the simulated river section; is the vertical scale of the model, is the model horizontal scale, is the dry bulk density ratio of sediment, is the sediment bulk density ratio, is the sediment particle size ratio; If the deviation of the total scouring and silting of the entire river section of the model is within ±20%, the model verification is successful; If the deviation of the total amount of scouring and silting in the entire river section of the model exceeds ±20%, it will be compared with the scouring and silting morphology of the prototype terrain: for areas where the scouring amount in the model is greater than that in the prototype terrain, the model sand particle size will be increased; for areas where the silting amount in the model is greater than that in the prototype terrain, the model sand particle size will be reduced.

[0013] The beneficial effects of the present invention are as follows: the present invention divides the bed sediment into zones in the plane and layers in the vertical direction according to the on-site bed sediment distribution and particle size classification, and each layer adopts the same representative gradation for generalized sand selection, and performs scouring and silting verification, thereby realizing accurate simulation of bed sediment movement. The present invention has been rigorously demonstrated through correlation and model test verification, and the results are reliable. The present invention can be applied to the simulation research of bed sediment movement in mountainous rivers, and can effectively solve the problem of bed sediment movement being difficult to simulate under complex bed sediment conditions in mountainous rivers, and enriches and develops the design method of moving bed physical model. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a sampling section (point) arrangement diagram for bottom sediment sampling of a simulated river section in the embodiment.

[0015] Figure 2a to Figure 2d is a graph of sediment gradation of various types of samples in the embodiment; wherein, Figure 2a It is the deep trough type sediment gradation curve. Figure 2b It is a shallow-type sediment gradation curve. Figure 2c is the coarsening type sediment gradation curve. Figure 2d It is the sediment gradation curve of geological survey sampling.

[0016] Figure 3 It is a graph of median particle size along the cross section in the embodiment.

[0017] Figure 4 It is a generalized curve diagram of the prototype sand and sediment gradation in the embodiment.

[0018] Figure 5 2 is a graph showing the gradation of various types of model sand in the embodiments.

[0019] Figure 6 Schematic diagram of layered and zoned laying of model sand in the embodiment.

[0020] Figure 7a to Figure 7c is a verification diagram of the scouring and silting volume of each shoal in the embodiment; wherein, Figure 7a This is the verification diagram of the sedimentation volume of each beach section. Figure 7b This is the verification diagram of the scouring volume of each beach section. Figure 7c It is a verification chart of the erosion and siltation volume of each beach section. DETAILED DESCRIPTION

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] This embodiment proposes a method for simulating bed load stratification and partitioning in a mountain river mobile bed physical model, specifically comprising the following steps: 1. Sediment sampling and classification.

[0023] Carry out bottom sediment sampling in the simulated river section. Carry out bottom sediment sampling on the surface of the riverbed, with sampling points arranged along the centerline of the river channel, with the spacing between sampling points not exceeding 500m, and the weight of each sampling body (i.e., the sample collected at each sampling point) exceeding 5kg; carry out drilling exploration vertically on the riverbed, with at least one borehole set up in the study section, with the drilling point located on the centerline of the river channel, and the drilling depth exceeding 5m. According to the statistics of the surface thickness of the drilling exploration column, sample the deep layer below the surface once, and the weight of the sampling body exceeding 5kg.

[0024] All samples were screened, and the gradation curves of each sample were drawn. The median particle size D was obtained using the gradation curves. 50 According to the median particle size, the sampling body was divided into three types of sediment: deep trough type, shallow shoal type, and coarsened type according to the standards of 0.1-1 mm, 1-10 mm, and 10-70 mm.

[0025] For the surface area of ​​the riverbed, the surface riverbed is divided into zones according to the sediment types of each surface sampling body; the vertical area of ​​the riverbed is divided into two layers, the upper layer is the surface layer, the thickness is determined according to the surface thickness of the drilling sampling statistics, and the lower layer is the deep layer, the thickness is determined according to the maximum scouring and silting thickness.

[0026] 2. Calculate the representative gradation and the proportion of each component.

[0027] For the same type of sediment, calculate the average value of its sediment gradation as the representative gradation of this type of sediment. The formula for calculating the average sediment gradation is: ; in, for n The average gradation of the samples of the same sediment type represents the average gradation of the corresponding type of sediment; For the i The gradation of the sample volume, i Number each sampling point; n is the number of samples of the same sediment type, x is the sediment particle size (mm), b To be infinitely close to x The approach coefficient, 0.1mm <b<x<100mm。

[0028] In view of the representative gradations of the three types of sediment, in order to facilitate the preparation of model sand and cover the composition characteristics of each type of sediment gradation, the three representative gradations are grouped according to particle size of 0.1~1mm, 1~5mm, 5~20mm, and 20~70mm, and the proportion of each particle size component is calculated as the basis for selecting model sand.

[0029] 3. Establish a sediment similarity scale calculation formula and model for sediment selection.

[0030] Based on the condition of similar sediment initiation, the sediment particle size ratio is derived. : ; in, is the sediment bulk density ratio, is the dry bulk density ratio of sediment, The vertical scale of the physical model is determined based on the minimum water depth condition of the physical model. .

[0031] The sediment particle sizes of each particle size component of the model sand are calculated based on the sediment particle size ratio: , , , , based on the fact that the proportion of each particle size component in the model sand is consistent with that in the prototype sand, model sand for various types of sediment is prepared.

[0032] 4. Model sand laying and verification test.

[0033] Determine the model's horizontal scale based on the simulation scope and laboratory scale , combined with the vertical scale of the model determined above , a physical model of the simulated riverbed is constructed, and the model elevation error is controlled within 1mm. The model is reserved with grooves for laying model sand. The laying of model sand is divided into two layers. The lower layer is laid according to the sediment type of the deep sampling point of the geological survey, and the upper layer is laid according to the sediment zoning type of the surface sampling point of the river section. First, the lower layer is laid, and the laying thickness is greater than the maximum scouring and silting thickness of the river channel; then the upper layer is laid, and the thickness of the upper layer is the thickness of the surface covering layer.

[0034] After the model sand is laid, a moving bed test is carried out under typical annual flow conditions. and scouring and silting time scale Release the flow to verify the scouring and silting of the riverbed; if the plane morphology, thickness and change process of the moving bed model and the scouring and silting parts of the prototype terrain are basically similar, and the deviation of the total scouring and silting of the whole river section is within ±20%, the model verification is successful, and the verified model can be used to simulate the movement law of bedload under different working conditions; if the deviation of the total scouring and silting of the whole river section exceeds ±20%, it is necessary to compare with the scouring and silting morphology of the prototype terrain, and fine-tune the model sand particle size in some areas. For the moving bed area with large scouring, the model sand particle size in this area should be appropriately increased; for the moving bed area with large silting, the model sand particle size in this area should be appropriately reduced.

[0035] Next, the preparation and laying of model sand for the design of the moving bed of the physical model of the Dongjiang Likou-Binglangtan section is taken as an example, and this embodiment is explained in combination with the accompanying drawings and specific implementation inferences.

[0036] The Dongjiang River is one of the three main streams of the Pearl River system in China. It is 138 km long. The upper reaches are stone riverbeds with many pebbles. The flow rate slows down when it flows to the plains in the middle and lower reaches. The riverbed is sandy, the river width varies, and there are endless sandy shoals. The Likou-Binglangtan section studied in this case is located at the junction of the upper and middle reaches of the Dongjiang River. It is 16.2 km long and covers four shoals: the Menghutiaoqiang shoal section, the Guanyin Pavilion shoal section, the Lanpai shoal section, and the Hengling shoal. The annual bedload sediment transport can reach 180,000 tons. The bottom conditions are complex and diverse. The traditional single sand selection method is difficult to simulate its real moving bed morphology. Comprehensively considering the research scope and laboratory conditions, the model plane scale is selected as 120, the minimum water depth of the comprehensive model is greater than 3 cm, and the model vertical scale is selected as 50. The method of this embodiment is used to simulate and lay the complex bottom of the study river section, including the following steps: (1) Bottom sediment sampling and classification.

[0037] Horizontally, bed material was collected along the centerline of the waterway in the Likou - Binglangtan section. A sampling section was arranged every 500 m, with a total of 23 sampling sections. Sediment samples were collected on the centerline of each section. Vertically, drilling surveys were carried out at the Menghutiaoqiang Shoal, Guanyinge Shoal, Lanpai Shoal and Hengling Shoal, with one survey point at each shoal. The drilling points were located on the centerline of the river channel, and the drilling depth was greater than 5 m. According to the statistical surface layer thickness of the drilling exploration columnar body, samples were taken from the deep layer below the surface layer. The sampling layout sections (points) are as Figure 1 shown.

[0038] All sampling bodies were screened, and the grading curves of each sampling body were drawn. The median grain size D 50 was obtained using the grading curve. According to the median grain size, the sampling bodies were divided into 3 sediment types: deep - trough type, shoal type, and coarsening type according to the standards of 0.1 - 1 mm, 1 - 10 mm, and 10 - 70 mm. The grading curves and classifications of each sampled sediment are as Figure 2a to Figure 2d shown.

[0039] A graph of the variation of the median grain size along the center of the waterway was made. The river channel was divided into 19 regions horizontally. The variation of the median grain size of the cross - sections along the course is as Figure 3 shown. At the same time, through the analysis of drilling survey data, it was found that the bottom sediment below 1.5 m of the shoal riverbed was mainly coarse sand (D 50 = 1 - 10 mm), which was generally close to the sediment grading of the shoal type. Therefore, the model sand simulating the shoal type should be laid on the bottom layer of the physical model, and the laying range was below 1.5 m of the riverbed (i.e., below 3 cm of the model depth).

[0040] (2) Calculate the representative grading and the proportion of each component.

[0041] According to the formula (0.1 mm < b < x < 100 mm), a mathematical generalization model of sediment grading was constructed to generalize the sediment grading of each type. Through the generalization process, three sediment grading curves were obtained, representing the average grading composition of three types of sediment. The generalized curve of the prototype sand sediment grading is as Figure 4 shown.

[0042] According to the generalized grading curves of the three types of sediment shown in Figure 4 , in order to facilitate the preparation of the model sand and cover the characteristics of the grading composition of each type of sediment, the three representative gradings were grouped by particle size according to 0.1 - 1 mm, 1 - 5 mm, 5 - 20 mm, and 20 - 70 mm, and the proportion of each particle size component was calculated as the basis for selecting the model sand. The proportion of each component is shown in Table 1.

[0043] Table 1 Proportion of each component of the prototype sand

[0044] (3) Establish a sediment similarity scale calculation formula and a model for sediment selection.

[0045] The horizontal scale of the physical model of the river section studied in this example is , vertical scale is The model sand is made of Shanxi smokeless water-washed clean coal, with a specific gravity of about 1.45, then: Sediment density ratio: ; Sediment dry bulk density ratio: ; Sediment particle size ratio: ; in, It is the measured sediment bulk density; is the bulk density of the model sand; is the sediment bulk density ratio; It is the measured dry bulk density of sediment; is the dry bulk density of the model sand; is the dry bulk density ratio of sediment; The vertical scale of the physical model is determined based on the minimum water depth condition of the physical model. In order to prevent the model sand from being too fine and compacted, coal powder with light bulk density and large particle size was selected as the model sand to determine the sediment bulk density ratio. and sediment dry density ratio .

[0046] According to the sediment particle size ratio calculated above, the four segments corresponding to the model sand are: 0.015-0.15mm, 0.15-1mm, 1-3mm, and 3-10mm. The proportion of each component should be consistent with that of the prototype sand, as shown in Table 2.

[0047] Table 2 Model sand preparation

[0048] At the same time, the sediment grading diagram of the model sand can also be made, such as Figure 5 According to this composition ratio, model sand similar to various types of prototype sand can be prepared.

[0049] (4) Model sand laying and verification test.

[0050] The horizontal scale of the model is determined according to the simulation scope and laboratory scale. Combined with the vertical scale of the model determined above, a dynamic bed physical model of the study river section is constructed, and the model elevation error is controlled within 1 mm. The model is reserved with grooves for laying model sand. According to the on-site sampling situation, the laying of model sand is divided into upper and lower layers. According to the vertical sampling results, the bottom gradation of the riverbed below 1.5 m is similar to the shoal type gradation, so the bottom layer of the model is laid with model sand A simulating the shoal layer gradation, and it is laid to 3 cm below the riverbed elevation. The upper layer of model sand is based on Figure 3 The plane sampling results are laid to the riverbed bottom elevation. The schematic diagram of the model sand layering and partitioning is as follows Figure 6 shown.

[0051] After the model sand was laid, the verification of sediment scouring and deposition was carried out from September 9, 2015 to August 8, 2017. The verification period was 23 months, including two medium flood processes, which can reflect the scouring and deposition changes of the river section. During this period, 2016 was a major flood with an average flow of 1056m 3 / s, the maximum flow rate reaches 3620m 3 / s. According to the traffic similarity scale and scouring and silting time scale The simulation of the discharge and erosion and sedimentation of the river section is as follows: Figure 7a to Figure 7c As shown, the plane morphology, thickness and change process of the dynamic bed model and the prototype terrain scouring and silting parts are basically similar, and the deviation of the total amount of scouring and silting in the whole river section is within ±20%, and the model verification is successful.

[0052] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for simulating bed load stratification and partitioning in a mountain river fluid bed physical model, characterized in that: include: Take bottom sediment samples from the simulated river section, classify the sediment types of the sampled body according to the sediment particle size, and divide the bottom sediment distribution into layers and zones; Calculate the average gradation of each type of sediment as the representative gradation of the corresponding type of sediment, group the sediment particle size of each representative gradation and calculate the proportion of each particle size component; Under the condition of similar sediment initiation, a sediment particle size ratio is established; the statistical proportion of each particle size component is divided by the sediment particle size ratio to obtain the proportion of each particle size component of the model sand, and model sand of each type of sediment is prepared according to the proportion of each particle size component of the model sand; A moving bed physical model of the simulated river section is constructed, and the prepared model sand is laid according to the sediment types in each layer and area.

2. A method for simulating bed load stratification and partitioning in a mountain river fluid bed physical model according to claim 1, characterized in that: The bottom sediment sampling of the simulated river section is specifically as follows: Arrange multiple sampling points on the riverbed surface along the center line of the river; Drilling exploration is carried out vertically on the riverbed, with the drilling point located on the center line of the river channel; the surface thickness is calculated based on the drilling samples, and the deep layer below the surface is sampled once.

3. A method for simulating bed load stratification and partitioning in a physical model of a mountain river fluidized bed as claimed in claim 2, characterized in that: The classification of the sediment types of the sampling body according to the sediment particle size is specifically as follows: The sampled bodies were sieved and the grading curves of the sampled bodies were drawn. The median particle size of the sampled bodies was obtained using the grading curves. According to the median particle size, the sampled bodies were divided into three sediment types: deep trough type, shallow shoal type and coarsened type according to the sediment particle size standards of 0.1-1mm, 1-10mm and 10-70mm.

4. A method for simulating bed load stratification and partitioning in a physical model of a mountain river fluidized bed as claimed in claim 3, characterized in that: The distribution of the bottom sediment is divided into layers and zones, specifically: The riverbed is divided into two layers vertically: the upper layer is the surface layer, the thickness of which is determined according to the surface thickness of the drilling sampling statistics; the lower layer is the deep layer, the thickness of which is determined according to the maximum scouring and silting thickness; For the surface layer, the surface layer was divided into zones according to the type of sediment in each sampling body in the surface layer.

5. The method for simulating bed load stratification and partitioning of a mountain river fluidized bed physical model according to claim 1, characterized in that: The average gradation of each type of sediment is calculated as the representative gradation of the corresponding type of sediment, and the calculation formula is as follows: ； in, for n The average gradation of the samples of the same sediment type represents the average gradation of the corresponding type of sediment; For the i The gradation of the sample volume; n is the number of samples of the same sediment type, x is the sediment particle size, b To be infinitely close to x The approach coefficient, 0.1mm <b<x<100mm; The sediment particle size grouping for each representative gradation is to group the calculated representative gradations into particle size groups according to 0.1-1 mm, 1-5 mm, 5-20 mm and 20-70 mm respectively.

6. The method for simulating bed load stratification and partitioning of a mountain river fluid bed physical model according to claim 1, characterized in that: The calculation formula of the sediment particle size ratio is: ； in, is the sediment particle size ratio, is the sediment bulk density ratio, is the dry bulk density ratio of sediment, is the vertical scale of the model.

7. The method for simulating bed load stratification and partitioning in a mountain river fluid bed physical model according to claim 1, characterized in that: The construction of the moving bed physical model of the simulated river section is specifically as follows: Determine the model's horizontal scale based on the simulation scope and laboratory scale , combined with the model vertical scale , a moving bed physical model of the simulated river section was constructed, the model elevation error was within 1 mm, and the model had grooves reserved for laying model sand.

8. The method for simulating bed load stratification and partitioning of a mountain river fluid bed physical model according to claim 4, characterized in that: The model sand prepared according to the type of sediment in each layer and each area is specifically: The model sand is laid in two layers, the lower layer is laid first, and the lower layer is laid according to the sediment type of the deep sampling body during drilling exploration, and the laying thickness is greater than the maximum scouring and silting thickness; the upper layer is laid secondly, and the upper layer is laid according to the zoning of the surface layer, and the laying thickness is the surface thickness calculated by drilling sampling statistics.

9. The method for simulating bed load stratification and partitioning in a mountain river fluid bed physical model according to claim 1, characterized in that: After laying the prepared model sand, a moving bed test is also carried out on the moving bed physical model of the simulated river section under typical annual flow conditions, specifically: According to the flow similarity scale and scouring and silting time scale Release the flow to verify the scouring and silting of the riverbed of the dynamic bed physical model of the simulated river section; is the vertical scale of the model, is the model horizontal scale, is the dry bulk density ratio of sediment, is the sediment bulk density ratio, is the sediment particle size ratio; If the deviation of the total scouring and silting of the entire river section of the model is within ±20%, the model verification is successful; If the deviation of the total amount of scouring and silting in the entire river section of the model exceeds ±20%, it will be compared with the scouring and silting morphology of the prototype terrain: for areas where the scouring amount in the model is greater than that in the prototype terrain, the model sand particle size will be increased; for areas where the silting amount in the model is greater than that in the prototype terrain, the model sand particle size will be reduced.

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