Grid type channel debris flow blocking dam

Abstract

The invention belongs to the field of debris flow disaster prevention and reduction, and provides a grating type channel debris flow blocking dam which comprises a vertical grating, an upstream inclined grating and a downstream inclined grating, and the grating type channel debris flow blocking dam is arranged in a gentle slope section ditch bed of a steep and gentle connection section of a channel; the lower end of the vertical grating is fixed in the gentle slope section ditch bed, and the vertical grating is vertical to the bed surface of the gentle slope section ditch bed and the along direction of the gentle slope section ditch bed; the starting ends of the upstream inclined grating and the downstream inclined grating are both connected with the top end of the vertical grating, the stopping ends of the upstream inclined grating and the downstream inclined grating are both higher than the top end of the vertical grating, the upstream inclined grating is located on the upstream side of the vertical grating, and the upstream inclined grating and the downstream inclined grating are located on the downstream side of the vertical grating. According to the grating type channel debris flow blocking dam, the movement speed and destructive power of debris flow particles can be reduced, and the energy dissipation blocking capacity of an existing grating dam on channel debris flow is improved.

Description

Technical Field

[0001] The invention belongs to the field of debris flow disaster prevention and reduction, and relates to a grid-type channel debris flow retaining dam. Background Art

[0002] Debris flow refers to the phenomenon that a large amount of loose debris such as rocks, sand and gravel gather and flow rapidly under the action of gravity, resulting in the instantaneous instability of the slope under the action of dynamic factors such as earthquakes and heavy rains. Debris flow is extremely destructive. It can cover a wide area in a short period of time, destroying infrastructure such as buildings, roads and bridges along the way, and posing a major threat to human life and property safety.

[0003] Due to the extremely destructive nature of debris flows, research on the transport mechanism and prevention and control methods of debris flows has always been a hot and difficult issue in the field of disaster prevention and mitigation at home and abroad. For example, Lei et al. used the discrete element method to numerically calculate the movement and accumulation process of loose slopes under different pile forest settings, and analyzed the influence of pile forest layout on the movement velocity of loose slopes and the average kinetic energy of particles, the number of unit contacts, the quality of sediment replenishment, the sediment accumulation morphology, and the distribution characteristics of particle size along the way. Based on the simulation results of the discrete element method, Shen Zhihao et al. pointed out that particle reversal is a stable structure in a probabilistic sense, and obtained a "binary structure" transport model by studying the movement law of debris flows. Taking the Wenjiagou debris flow as an example, Yuan Jintao explored and analyzed the influence of factors such as seismic load and particle grading on the scraping effect through physical model experiments and numerical simulations, and established an instantaneous scraping model of landslide debris flow based on impact mechanics. Due to the extremely complex transport and accumulation mechanisms of debris flows, although the academic community has conducted a lot of research on the scientific prevention and control of debris flow disasters, a mature solution that can be directly applied to engineering has not yet been formed, and the interaction mechanism between debris flows and retaining structures is still under continuous exploration.

[0004] Traditional retaining structures are usually large solid retaining dams. Although such solid retaining dams can effectively block the invasion of debris flow in the early stage, due to the limitation of storage capacity, as the debris flow material continues to accumulate, once the storage capacity is filled, its protective function is greatly reduced, and it is difficult to effectively resist the impact of subsequent debris flow. Compared with solid retaining dams, the application of grid dams in debris flow prevention and control projects has been rapidly developed due to its advantages such as good stress conditions and simple structure. However, when the debris flow contacts and collides with the grid dam, a large number of particles will be splashed from the bed surface, which greatly reduces the retaining and protective effect of the grid dam. For this reason, it is necessary to improve the existing grid dam used for channel debris flow interception to improve its energy dissipation efficiency. Summary of the invention

[0005] In view of the problem that when existing grid dams block channel debris flow, a large amount of particles will be splashed from the bed surface after the debris flow collides with the grid dam, resulting in a significant reduction in the blocking and protection effect of the grid dam, the present invention is based on the transport law of channel debris flow and provides a grid-type channel debris flow blocking dam to reduce the movement speed and destructive power of debris flow particles, improve the energy dissipation and blocking capacity of existing grid dams for channel debris flow, and provide a new technical means for disaster prevention and mitigation of channel debris flow.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A grid-type channel debris flow barrier dam comprises a vertical grid, an upstream inclined grid and a downstream inclined grid, and the grid-type channel debris flow barrier dam is arranged in a channel bed of a gentle slope section of a steep-gentle transition section of a channel;

[0008] The lower end of the vertical grid is fixed in the ditch bed of the gentle slope section, and the vertical grid is perpendicular to the bed surface of the ditch bed of the gentle slope section and the along-direction of the ditch bed of the gentle slope section; the starting ends of the upstream inclined grid and the downstream inclined grid are both connected to the top end of the vertical grid, and the ending ends of the upstream inclined grid and the downstream inclined grid are both higher than the top end of the vertical grid, the upstream inclined grid is located on the upstream side of the vertical grid, and the upstream inclined grid and the downstream inclined grid are located on the downstream side of the vertical grid.

[0009] In the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the angle between the upstream inclined grid and the bed surface of the gently sloping ditch bed is preferably 30° to 60°, and the angle between the downstream inclined grid and the bed surface of the gently sloping ditch bed is preferably 30° to 60°.

[0010] In the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the widths of the starting ends of the upstream inclined grid and the downstream inclined grid are consistent with the width of the top of the vertical grid, the ending end of the upstream inclined grid is parallel to the starting end, and the ending end of the downstream inclined grid is parallel to the starting end.

[0011] Furthermore, in the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the distance from the starting end to the ending end of the upstream inclined grid is preferably 10% to 30% of the width of the ditch bed of the gentle slope section, and the distance from the starting end to the ending end of the downstream inclined grid is preferably 10% to 30% of the width of the ditch bed of the gentle slope section.

[0012] In the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the height of the upstream inclined grid in the direction perpendicular to the grid height may be equal to or unequal to the height of the downstream inclined grid in the direction perpendicular to the grid height.

[0013] Furthermore, in the technical solution of the above-mentioned grid-type channel debris flow barrier, the width of the terminal end of the upstream inclined grid is greater than or equal to the width of the starting end, and the width of the terminal end of the downstream inclined grid is greater than or equal to the width of the starting end. For example, the upstream inclined grid and the downstream grid can be rectangular or trapezoidal.

[0014] In the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the height of the vertical grid is preferably 20% to 30% of the width of the channel bed in the gentle slope section.

[0015] In the technical solution of the above-mentioned grid-type channel debris flow barrier dam, the width of the vertical grid is consistent with the width of the gentle slope section ditch bed. More specifically, the width of the vertical grid is consistent with the width of the gentle slope section ditch bed where the vertical grid is set.

[0016] In the above-mentioned technical solution of the grid-type channel debris flow barrier dam, the grids on the vertical grid, the upstream inclined grid and the downstream inclined grid are all rectangular grids. Furthermore, the side length of the rectangular grid is preferably 5% to 40% of the width of the gentle slope section of the channel bed.

[0017] In the technical solution of the above-mentioned grid-type channel debris flow barrier dam, the vertical grid is composed of a plurality of columns and beams, the columns and beams are perpendicular to each other, and the upstream inclined grid and the downstream inclined grid are composed of a plurality of beams. The material, thickness, cross-sectional shape, etc. of the columns and beams constituting the vertical grid, and the beams constituting the upstream inclined grid and the downstream inclined grid are generally based on the principle that the strength of the grid-type channel debris flow barrier dam can withstand the impact of the channel body debris flow. For example, the columns, cross-sectional shapes and beams can be made of reinforced concrete or steel, and the cross-sectional shape can be rectangular.

[0018] In the technical solution of the above-mentioned grid-type channel debris flow retaining dam, the area where the gentle slope section of the steep-gentle transition section of the channel where the grid-type channel debris flow retaining dam is set, or the downstream area of ​​the gentle slope section, has a disaster prevention and protection object. Through the blocking and energy dissipation effect of the grid-type channel debris flow retaining dam, the disaster prevention and mitigation effect of the channel debris flow can be played on the disaster prevention and protection object.

[0019] Compared with the prior art, the technical solution provided by the present invention produces the following beneficial technical effects:

[0020] 1. The present invention provides a grid-type channel debris flow retaining dam, comprising a vertical grid, an upstream inclined grid and a downstream inclined grid. The grid-type channel debris flow retaining dam is arranged in the gently sloping ditch bed of the steep-gentle transition section of the channel, the lower end of the vertical grid is fixed in the gently sloping ditch bed, the vertical grid is perpendicular to the bed surface of the gently sloping ditch bed and the along-direction of the gently sloping ditch bed; the starting ends of the upstream inclined grid and the downstream inclined grid are both connected to the top end of the vertical grid, the terminal ends of the upstream inclined grid and the downstream inclined grid are both higher than the top end of the vertical grid, the upstream inclined grid is located on the upstream side of the vertical grid, and the upstream inclined grid and the downstream inclined grid are located on the downstream side of the vertical grid. By setting upstream inclined grids and downstream inclined grids on the upstream and downstream sides of the top of the existing grid dam, compared with the situation of setting the existing grid dam in the channel, after setting the grid-type channel debris flow retaining dam of the present invention in the channel, it can effectively reduce the collision between particles of the channel slope debris flow and reduce the movement speed of the particles in the channel. At the same time, it can produce better energy dissipation and regulate the downstream sediment replenishment process, which can enhance the disaster prevention and mitigation effect of the channel debris flow.

[0021] 2. The present invention has been verified through numerical simulation calculations that, under the same arrangement position and the same total height, compared with setting an existing grid dam in the channel, setting the grid-type channel debris flow retaining dam of the present invention in the channel can effectively reduce the collision between particles of the debris flow on the channel slope and reduce the movement speed of the particles in the channel, thereby producing a more excellent energy dissipation and retaining effect on the channel debris flow.

[0022] 3. The grid-type channel debris flow retaining dam described in the present invention has a simple structure. In actual engineering applications, the height and size of the vertical grid can be flexibly set according to the characteristics of the actual channel and different protection requirements, and the size, inclination and size of the upstream inclined grid and the downstream inclined grid can be flexibly adjusted, thereby achieving diversified sand regulation and disaster reduction effects and effectively enhancing the feasibility and convenience of engineering applications. The above characteristics are conducive to the practical application value of the grid-type debris flow retaining dam described in the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a comparison chart of the numerical simulation results of the sediment transport process under different sediment inflow conditions using the discrete element method and the experimental data in the literature.

[0024] Figure 2 It is a schematic diagram of the channel physics model.

[0025] Figure 3 It is a schematic diagram of setting up a grid-type channel debris flow barrier in the channel physical model.

[0026] Figure 4 It is a structural schematic diagram of a grid-type channel debris flow retaining dam.

[0027] Figures 2 to 4 In the figure, 1 is the vertical grid, 2 is the upstream inclined grid, 3 is the downstream inclined grid, 4 is the steep slope section, 5 is the gentle slope section, 6 is the grid-type channel debris flow barrier, V is the width of the steep slope section, L1 is the length of the steep slope section, L2 is the length of the gentle slope section, α is the angle between the ditch bed surface of the steep slope section and the horizontal plane, h1 is the height of the vertical grid, a1 is the height of the first grid layer of the vertical grid, a2 is the height of the second grid layer of the vertical grid, h2 is the height of the downstream inclined grid in the vertical grid height direction, H0 is the total height of the grid-type channel debris flow barrier, θ1 is the angle between the upstream inclined grid and the ditch bed surface of the gentle slope section, θ2 is the angle between the downstream inclined grid and the ditch bed surface of the gentle slope section, b1, b2, b3 are the widths of each grid of the upstream inclined grid, l1 is the length of the upstream grid, l2 is the length of the downstream inclined grid.

[0028] Figure 5 is a schematic diagram of the structure of the existing grid dam used in comparative example 1, Figure 5 Middle, H 01 —Total height of the grating dam, a 10 、a 20 、a 30 —The height of the first, second and third grid layers of the grid dam, b 10 、b 20 、b 30 —The width of the first, second and third layers of the gratings of the grating dam.

[0029] Figure 6 is the particle size distribution diagram of channel debris flow.

[0030] Figure 7 It is a cloud diagram of the movement speed of particles in the channel physical model of comparative example 2 at different times.

[0031] Figure 8 It is a cloud diagram of the movement speed of particles in the channel physical model of comparative example 1 at different times.

[0032] Fig. 9 It is a cloud diagram of the movement speed of particles at different times in the channel physical model of the grid-type channel debris flow retaining dam of type A in Example 1.

[0033] Fig.10 Figure (A) is a numerical simulation result of the effect of the average movement speed of particles in the physical model of Examples 1 to 3 on the x-direction. Fig.10 Figure (C) is a numerical simulation result of the effect of the average movement speed of particles in the physical model of Examples 1 to 3 on the z direction. Fig.10In Figures (A) and (C), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of Comparative Example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°. Fig.10 FIG. (B) is a numerical simulation result of the influence of the average movement velocity of particles in the x direction in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Examples 1-2, Fig.10 Figure (D) is a numerical simulation result of the influence of the average movement velocity of particles in the z direction in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Examples 1-2, Fig.10 In Figures (B) and (D), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0034] Fig.11 Figure (A) shows the relationship between the number of unit contacts and time in the physical model of Example 1 and Example 3. Fig.11 In Figure (A), the ordinary grid dam represents the physical model in Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models in Comparative Example 3 where the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°. Fig.11 FIG. (B) shows the relationship between the number of unit contacts over time in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Example 1. Fig.11 In Figure (B), the ordinary grid dam represents the physical model in Comparative Example 1, and the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0035] Fig.12 Figure (A) shows the variation of the average combined velocity of particles in the physical model of Examples 1 to 3 over time. Fig.12In Figure (A), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of Comparative Example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°. Fig.12 FIG. (B) shows the variation of the average combined velocity of particles over time in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Examples 1-2. Fig.12 In Figure (B), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0036] Fig.13 Figure (A) shows the relationship between the cumulative mass of particles in the studied section and time in Examples 1 to 3. Fig.13 In the figure (A), the non-grid dam represents the physical model of comparative example 2, the ordinary grid dam represents the physical model of comparative example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of comparative example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°. Fig.13 FIG. (B) shows the relationship between the cumulative mass of particles in the research section and the time of the channel physical model of the channel physical model of the three types of grid channel debris flow barriers A, D, and E in Example 1 and the channel physical model in Comparative Examples 1-2. Fig.13 In the figure (B), the non-grid dam represents the physical model of comparative example 2, the ordinary grid dam represents the physical model of comparative example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1. DETAILED DESCRIPTION

[0037] The following is a further description of the grid-type channel debris flow barrier dam of the present invention through examples and drawings. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above invention content and implement them specifically, which still falls within the scope of protection of the invention.

[0038] In the following embodiments, in order to analyze the influence of the grid-type channel debris flow barrier on the transport process of the channel debris flow and the energy dissipation and barrier effect, it is necessary to use the discrete element method to numerically simulate the transport process of the channel debris flow under different working conditions. Therefore, it is necessary to verify the reliability and accuracy of the discrete element method in simulating the transport process of the channel debris flow.

[0039] Specifically, it is based on the verification method provided in the literature [Cheng Hao, Han Peifeng, Su Youwen. Analysis of sliding accumulation characteristics and influencing factors of loose bodies based on discrete element method [J]. Acta Physica Sinica, 2020, 69(16): 164501.], and the sediment loads in the literature [Zhou JW, Yang XG, Hou TX. An analysis of the supply process of loose materials to mountainous rivers and gullies as a result of dry debris avalanches [J]. Environmental Earth Sciences, 2017, 76(13): 452.] are 0.005m 3 and 0.015m 3 The numerical calculation was carried out based on the model test, that is, the discrete element method was used to calculate the sediment flow rate of 0.005m 3 and 0.015m 3 The transport process of sediment particles with a particle size of 20 to 60 mm was numerically simulated under the conditions of . The comparison between the numerical simulation results and the experimental data in the literature is shown in Figure 1 As shown by Figure 1 It can be seen that the particle cumulative mass versus time curve obtained by numerical simulation is in good agreement with the experimental results, and the overall trend is consistent. This shows that the use of discrete element method to simulate the transport process of channel debris flow is effective and reliable.

[0040] Example 1

[0041] In this embodiment, a grid-type channel debris flow retaining dam is provided.

[0042] Considering that most actual channels are in the form of steep slopes and gentle slopes connected to each other, in this embodiment, according to the topography of an actual natural channel, a channel physical model is adopted in which a steep slope section (first slope) and a gentle slope section (second slope) are connected to each other. Figure 2As shown, the channel physical model includes a steep slope section 4 and a gentle slope section 5 connected to each other. In the channel physical model, the widths of the steep slope section and the gentle slope section are equal, the width V of the steep slope section is 20m, the length L1 of the steep slope section is 100m, and the length L2 of the gentle slope section is 200m. The angle α between the ditch bed surface of the steep slope section and the horizontal plane is 45°, and the angle between the gentle slope section and the horizontal plane is 0°. Loose deposits are deposited on the top of the steep slope section, and the loose deposits will be transformed into channel debris flow under the impact of the incoming flow.

[0043] The structure of the grid channel debris flow barrier 6 is as follows: Figure 4 As shown, the grid-type channel debris flow barrier is arranged in the ditch bed of the gentle slope section (see FIG. Figure 3 ), the lower end of the vertical grid 1 is fixed in the ditch bed of the gentle slope section, the vertical grid 1 is perpendicular to the bed surface of the ditch bed of the gentle slope section, and the vertical grid 1 is perpendicular to the along-course direction of the ditch bed of the gentle slope section; the starting ends of the upstream inclined grid 2 and the downstream inclined grid 3 are both connected with the top of the vertical grid 1, and the terminal ends of the upstream inclined grid 2 and the downstream inclined grid 3 are both higher than the top of the vertical grid 1, the upstream inclined grid 2 is located on the upstream side of the vertical grid 1, and the upstream inclined grid 2 and the downstream inclined grid 3 are located on the downstream side of the vertical grid 1. The angle between the upstream inclined grid 2 and the bed surface of the ditch bed of the gentle slope section is 30° to 60°, and the angle between the downstream inclined grid 3 and the bed surface of the ditch bed of the gentle slope section is 30° to 60°.

[0044] More specifically: the vertical grid 1 is rectangular in shape as a whole, and is composed of a number of columns and beams, which are perpendicular to each other. Two layers of grids are set on the vertical grid, with three grids on each layer; the upstream inclined grid and the downstream inclined grid are rectangular in shape as a whole, and are composed of a number of perpendicular beams. Two layers of grids are set on the upstream inclined grid, with three grids on each layer, and one layer of grids is set on the downstream inclined grid, with a total of three grids. The vertical grid is set on a section with a horizontal distance of 125m from the starting end of the steep slope section.

[0045] The height of the vertical grid is recorded as h1, the height of the first layer of the vertical grid is recorded as a1, the height of the second layer of the vertical grid is recorded as a2, the height of the downstream inclined grid in the vertical grid height direction is recorded as h2, the height of the upstream inclined grid in the vertical grid height direction is equal to the height of the downstream inclined grid in the vertical grid height direction, the total height of the grid-type channel debris flow barrier is recorded as H0, H0=h1+h2, the angle between the upstream inclined grid and the bed surface of the gentle slope section ditch bed is recorded as θ1, the angle between the downstream inclined grid and the bed surface of the gentle slope section ditch bed is recorded as θ2, the width of each grid of the upstream inclined grid is recorded as b1, b2, b3, respectively, the width of each grid in the downstream inclined grid and the vertical grid is equal to the width of the upstream inclined grid, as shown in FIG. Figure 4As shown in the markings in. The width of the vertical grid = the width of the upstream inclined grid = the width of the downstream inclined grid = 20m. Based on h2, θ1 and θ2, the length l1 of the upstream grid and the length l2 of the downstream inclined grid can be calculated.

[0046] In this embodiment, nine types of grid-type channel debris flow retaining dams A to I are provided, and their external dimension parameters are shown in Table 1.

[0047] Table 1 Dimensional parameters of the grid-type channel debris flow barrier

[0048] Dam form <![CDATA[H0(m)]]> <![CDATA[h1(m)]]> <![CDATA[h2(m)]]> <![CDATA[a1、a2(m)]]> <![CDATA[b1、b3(m)]]> <![CDATA[b2(m)]]> <![CDATA[θ1(°)]]> <![CDATA[θ2(°)]]> <![CDATA[l1(m)]]> <![CDATA[l2(m)]]> A 6 4 2 2 6.2 7.6 30 30 4 4 B 6 4 2 2 6.2 7.6 45 45 2.8 2.8 C 6 4 2 2 6.2 7.6 60 60 2.3 2.3 D 6 4 2 2 6.2 7.6 30 45 4 2.8 E 6 4 2 2 6.2 7.6 30 60 4 2.3 F 6 4 2 2 6.2 7.6 45 60 2.8 2.3 G 6 4 2 2 6.2 7.6 45 30 2.8 4 H 6 4 2 2 6.2 7.6 60 30 2.3 4 I 6 4 2 2 6.2 7.6 60 45 2.3 2.8

[0049] Comparative Example 1

[0050] In this comparative example, an existing grid dam is set in the channel physical model.

[0051] The structural diagram of the grid dam in this comparative example is as follows Figure 5 As shown, the structure of the grid dam is similar to the vertical grid in the embodiment, specifically: the grid dam is rectangular as a whole, and is composed of a number of columns and beams, the columns and beams are perpendicular to each other, and there are three layers of grids on the grid dam, with three grids on each layer. The total height H of the grid dam 01 The total height H0 is equal to that of the grid-type channel debris flow retaining dam described in Example 1, that is, H 01 =H0. The height of the first, second and third layers of the grid dam is recorded as a 10 、a 20 、a 30 The width of each grid of the grid dam is recorded as b 10 , b 20 , b 30 In this embodiment, a 10 =a 20 =a 30 The width of the grid dam is 20m, and the width of each grid of the grid dam is equal to the width of each grid of the upstream inclined grid in Example 1, that is, b 10 = b1, b 20 = b2, b 30 =b3, the external dimension parameters of the grid dam are shown in Table 2.

[0052] Table 2 Dimensional parameters of the grid dam

[0053] <![CDATA[H 01 (m)]]> <![CDATA[a 10 、a 20 、a 30 (m)]]> <![CDATA[b 10 、b 30 (m)]]> <![CDATA[b 20 (m)]]> Grille dam 6 2 6.2 7.6

[0054] In the channel physical model in which the grid dam is set up with the same structure as in Example 1, the setting position and setting form are the same as in Example 1, that is, the lower end of the grid dam is fixed in the gentle slope section ditch bed, the grid dam is perpendicular to the bed surface of the gentle slope section ditch bed, and the grid dam is perpendicular to the along direction of the gentle slope section ditch bed.

[0055] Comparative Example 2

[0056] In this comparative example, the same channel physical model as that of Example 1 is used, and no channel debris flow blocking structure is arranged in the channel physical model.

[0057] Comparative Example 3

[0058] In this comparative example, the retaining dam is arranged in the channel physical model according to the arrangement in Example 1. The structure of the retaining dam arranged in the channel physical model in this comparative example is basically the same as the structure of the grid-type channel debris flow retaining dams of types A, B, and C in Example 1. The only difference is that the downstream inclined grid in the grid-type channel debris flow retaining dams of types A, B, and C in Example 1 is removed, and only the upstream inclined grid is retained.

[0059] Example 2

[0060] In this embodiment, the discrete element method is used to simulate the transport process of the channel debris flow, specifically simulating the transport process of the channel debris flow in Example 1 and Comparative Examples 1 to 2, and examining the influence of the grid-type channel debris flow retaining dam and the grid dam on the movement law of the channel debris flow.

[0061] This embodiment refers to the method in the literature [Zhao Chuan, Fu Chenghua, Zou Haiming, et al. Numerical simulation analysis of three-dimensional landslide process based on discrete element method [J]. People's Pearl River, 2015, 4 (2): 11-15.] to perform numerical simulation calculations. The calculation parameters used in the numerical simulation are shown in Table 3. The effect of the cohesion between particles is not considered in the numerical simulation calculation process. The particle size distribution of the channel debris flow is shown in Figure 6 shown.

[0062] Table 3 Numerical simulation calculation related parameters

[0063]

[0064] 1. Numerical simulation of the channel physical models in Example 1 and Comparative Examples 1-2 to compare their effects on the movement law of channel debris flow

[0065] The aforementioned method of this embodiment is used to perform numerical simulation on the channel physical model of the grid-type channel debris flow retaining dam of type A in Example 1, as well as the channel physical models in Comparative Examples 1 and 2. Figure 7 It is a cloud diagram of the movement speed of particles in the channel physical model of comparative example 2 at different times. Figure 8 It is a cloud diagram of the movement speed of particles in the channel physical model of comparative example 1 at different times. Fig. 9It is a cloud diagram of the movement speed of particles at different times in the channel physical model of the grid-type channel debris flow retaining dam of type A in Example 1.

[0066] Depend on Figure 7 It can be seen that when there is no blocking structure in the ditch bed of the gentle slope section, the debris flow particles slide rapidly along the ditch under the action of gravity, showing characteristics such as large volume, fast speed and strong impact force. Figure 8 It can be seen that when the existing grid dam is set in the ditch bed of the gentle slope section, the movement speed of the debris flow particles is effectively reduced, indicating that the grid dam has a certain regulatory effect on the migration process of the debris flow. However, when the front edge of the debris flow contacts and collides with the grid dam, a large number of particles will splash upward from the ditch bed surface, resulting in a serious reduction in the blocking and energy dissipation effect of the grid dam on the debris flow.

[0067] Depend on Fig. 9 It can be seen that after the grid-type channel debris flow barrier is set in the gentle slope section, the energy dissipation effect on the splashed particles can be significantly improved compared with the grid dam set in Comparative Example 1. Figures 8-9 It can be seen that when the total height of the grid dam and the grid-type channel debris flow retaining dam is the same, the range of the low-speed area in the velocity cloud map of the particles in the physical model with the grid-type channel debris flow retaining dam is significantly larger than that in the physical model with the grid dam, indicating that the grid-type channel debris flow retaining dam has a better energy dissipation and retaining effect.

[0068] 2. Numerical simulation of the channel physical models in Example 1 and Comparative Examples 1 to 3 to compare their effects on the average particle movement speed

[0069] The aforementioned method of this embodiment is used to perform numerical simulation on the channel physical models in Comparative Examples 1 to 3. Fig.10 Figure (A) is a numerical simulation result of the effect of the average moving speed of particles in the physical model of Examples 1 to 3 on the x-direction. Fig.10 Figure (C) is a numerical simulation result of the effect of the average movement speed of particles in the physical model of Examples 1 to 3 on the z direction. Fig.10 In Figures (A) and (C), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of Comparative Example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°.

[0070] The aforementioned method of this embodiment is used to perform numerical simulation on the channel physical model of the three types of grid-type channel debris flow retaining dams A, D, and E in Example 1, as well as the channel physical models in Comparative Examples 1-2. Fig.10FIG. (B) is a numerical simulation result of the influence of the average movement velocity of particles in the x direction in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Examples 1-2, Fig.10 Figure (D) is a numerical simulation result of the influence of the average movement velocity of particles in the z direction in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Examples 1-2, Fig.10 In Figures (B) and (D), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0071] Depend on Fig.10 As shown in Figures (A) and (C), according to the method of comparative example 3, adding an upstream inclined grid on the basis of the existing grid dam reduces the movement speed of the particles in the physical model, and its blocking effect is better than that of the existing grid dam. In addition, the average speed of the particles in the physical model in the x and z directions gradually decreases as the angle between the upstream inclined grid and the gentle slope ditch bed decreases. Fig.10 It can be seen from Figures (B) and (D) that, according to the method of Example 1, after adding upstream inclined grids and downstream inclined grids on the basis of the existing grid dam, its blocking and protection capabilities can be effectively improved, and it has a better energy dissipation effect than the existing grid dam. Taking the particle movement time of 8s as an example, in the physical model of Example 1, the average speed of the particles in the x and z directions are 11.4m / s and 1.4m / s respectively. In the physical model of the grid-type channel debris flow retaining dam of types A, D, and E set in Example 1, the average speed of the particles in the x and z directions are 9.1m / s and 1.1m / s respectively, with a decrease of 20.2% and 23.4% respectively. However, the average speed of the particles in the x and z directions in the physical model is not sensitive to the change in the angle between the downstream inclined grid and the bed surface of the gentle slope section of the ditch bed.

[0072] 3. Numerical simulation of the channel physical models in Example 1 and Comparative Examples 1 to 3 was performed to compare their effects on the collision degree during the movement of debris flow

[0073] The number of unit contacts in the debris flow movement in the channel can reflect the degree of collision of particles in the channel. The above method of this embodiment is used to perform numerical simulation on the physical models of comparative examples 1 to 3. Fig.11 Figure (A) shows the relationship between the number of unit contacts and time in the physical model of Example 1 and Example 3. Fig.12Figure (A) shows the change of the average combined velocity of particles in the physical model of Examples 1 to 3 over time. Figures 11-12 In Figure (A), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of Comparative Example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°.

[0074] The aforementioned method of this embodiment is used to perform numerical simulation on the channel physical model of the grid-type channel debris flow retaining dams of three forms A, D, and E in Example 1 and the channel physical models in Comparative Examples 1-2. Fig.11 FIG. (B) shows the relationship between the number of unit contacts over time in the channel physical model of the channel debris flow barrier dams in the three forms of A, D and E set in Example 1 and the channel physical model in Comparative Example 1. Fig.12 Figure (B) shows the change of the average combined velocity of particles over time in the channel physical model of the channel debris flow retaining dam with three types of grid-type channels A, D, and E in Example 1 and the channel physical model in Comparative Examples 1 to 2. Figures 11-12 In Figure (B), the non-grid dam represents the physical model of Comparative Example 2, the ordinary grid dam represents the physical model of Comparative Example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0075] Depend on Figures 11-12 It can be seen that at the beginning of the movement of the channel debris flow, the particles are tightly stacked and the number of unit contacts is 49911. As time goes by, the channel debris flow moves rapidly, the number of unit contacts drops rapidly and then slowly recovers, and the average speed of the particles shows the opposite change characteristics. The reduction in the number of unit contacts indicates that the degree of particle collision is weakened, the kinetic energy loss of the debris flow is reduced, and the average speed of the particles increases. Compared with the existing grid dam, the grid-type channel debris flow retaining dam in Example 1 can increase the number of unit contacts of the debris flow. For the retaining dam in Comparative Example 3, the number of unit contacts and the angle between the upstream inclined grid and the bed surface of the gentle slope section of the ditch bed are generally negatively correlated, such as Fig.11 As shown in Figure (A). Fig.11 As shown in Figure (B), adding upstream and downstream inclined grids to the existing grid dam can increase the number of unit contacts during debris flow transport, but the number of unit contacts is not sensitive to the change in the angle between the downstream inclined grid and the ditch bed surface on the gentle slope.

[0076] 4. Numerical simulation of the channel physical models in Example 1 and Comparative Examples 1 to 3 to compare their effects on the downstream sediment replenishment process

[0077] A section with a horizontal distance of 130 m (a section with a horizontal distance of 130 m from the starting end of the steep slope section) was selected as the research section, and the above method of this embodiment was used to perform numerical simulation on the physical models of comparative examples 1 to 3. Fig.13 Figure (A) shows the relationship between the cumulative mass of particles in the studied section and time in Examples 1 to 3. Fig.13 In the figure (A), the non-grid dam represents the physical model of comparative example 2, the ordinary grid dam represents the physical model of comparative example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of comparative example 3 in which the angles between the upstream inclined grid and the gentle slope ditch bed are 30°, 45°, and 60°.

[0078] A section with a horizontal distance of 130 m (a section with a horizontal distance of 130 m from the starting end of the steep slope section) was selected as the research section, and the aforementioned method of this embodiment was used to perform numerical simulation on the channel physical model of the grid-type channel debris flow retaining dams in the three forms of A, D, and E in Example 1 and the channel physical model in Comparative Examples 1-2. Fig.13 FIG. (B) shows the relationship between the cumulative mass of particles in the research section and the time of the channel physical model of the channel physical model of the three types of grid channel debris flow barriers A, D, and E in Example 1 and the channel physical model in Comparative Examples 1-2. Fig.13 In the figure (B), the non-grid dam represents the physical model of comparative example 2, the ordinary grid dam represents the physical model of comparative example 1, the new grid dam (30°), the new grid dam (45°), and the new grid dam (60°) represent the physical models of the grid-type channel debris flow retaining dams of types A, D, and E set in Example 1.

[0079] Depend on Fig.13It can be seen that with the passage of time, the sediment mass passing through the study section generally shows a change characteristic of first increasing and then decreasing; after adding the upstream inclined grid on the basis of the existing grid dam, the sediment supply intensity and the total amount of sediment supply through the study section can be reduced; after adding the upstream inclined grid and the downstream inclined grid on the basis of the existing grid dam, the sediment supply intensity and the total amount of sediment supply through the study section can be further reduced, and when the angle between the upstream inclined grid and the ditch bed surface of the gentle slope section is 30°, the sand regulation and energy dissipation effect is the best when the angle between the downstream inclined grid and the ditch bed surface of the gentle slope section is 30°, and the blocking effect is relatively small when the angle between the downstream inclined grid and the ditch bed surface of the gentle slope section is 45° and 60°; compared with the existing grid dam, when the angle between the upstream inclined grid and the downstream inclined grid and the ditch bed surface of the gentle slope section is 30°, the sediment accumulation mass passing through the study section increases from 9.51×10 5 kg decreased to 3.15×10 5 kg, a decrease of 70%.

[0080] This embodiment has confirmed through the above numerical simulation process that, compared with the case of setting the existing grid dam, setting the grid-type channel debris flow retaining dam described in the present invention in the gentle slope ditch bed of the steep-gentle transition section of the channel can effectively reduce the collision between the particles of the channel slope debris flow and reduce the movement speed of the particles in the channel, while producing better energy dissipation and regulating the downstream sediment replenishment process, and can enhance the disaster prevention and mitigation effect on the channel debris flow.

Claims

1. A grid-type channel debris flow barrier, comprising a vertical grid (1), characterized in that: It also includes an upstream inclined grid (2) and a downstream inclined grid (3), wherein the grid-type channel debris flow barrier is arranged in the channel bed of the gentle slope section of the steep-gentle transition section of the channel; The lower end of the vertical grid (1) is fixed in the gentle slope section ditch bed, and the vertical grid (1) is perpendicular to the gentle slope section ditch bed surface and the along-course direction of the gentle slope section ditch bed; the starting ends of the upstream inclined grid (2) and the downstream inclined grid (3) are both connected to the top end of the vertical grid (1), and the ending ends of the upstream inclined grid (2) and the downstream inclined grid (3) are both higher than the top end of the vertical grid (1); the upstream inclined grid (2) is located on the upstream side of the vertical grid (1), and the upstream inclined grid (2) and the downstream inclined grid (3) are located on the downstream side of the vertical grid (1).

2. The grid-type channel debris flow barrier according to claim 1, characterized in that: The angle between the upstream inclined grid (2) and the surface of the ditch bed in the gentle slope section is 30° to 60°, and the angle between the downstream inclined grid (3) and the surface of the ditch bed in the gentle slope section is 30° to 60°.

3. The grid-type channel debris flow barrier according to claim 1, characterized in that: The widths of the starting ends of the upstream inclined grille (2) and the downstream inclined grille (3) are consistent with the width of the top end of the vertical grille (1); the ending end of the upstream inclined grille (2) is parallel to the starting end; and the ending end of the downstream inclined grille (3) is parallel to the starting end.

4. The grid-type channel debris flow barrier dam according to claim 3, characterized in that: The distance from the starting end to the ending end of the upstream inclined grid (2) is 10% to 30% of the width of the ditch bed in the gentle slope section, and the distance from the starting end to the ending end of the downstream inclined grid (3) is 10% to 30% of the width of the ditch bed in the gentle slope section.

5. The grid-type channel debris flow barrier dam according to claim 4, characterized in that: The width of the terminal end of the upstream inclined grille (2) is greater than or equal to the width of the starting end, and the width of the terminal end of the downstream inclined grille (3) is greater than or equal to the width of the starting end.

6. The grid-type channel debris flow barrier according to any one of claims 1 to 5, characterized in that: The height of the vertical grid (1) is 20% to 30% of the width of the ditch bed in the gentle slope section.

7. The grid-type channel debris flow barrier according to any one of claims 1 to 5, characterized in that: The width of the vertical grid (1) is consistent with the width of the ditch bed in the gentle slope section.

8. The grid-type channel debris flow barrier according to any one of claims 1 to 5, characterized in that: The grids on the vertical grid (1), the upstream inclined grid (2) and the downstream inclined grid (3) are all rectangular grids.

9. The grid-type channel debris flow retaining dam according to claim 8, characterized in that: The side length of the rectangular grid is 5% to 40% of the width of the ditch bed in the gentle slope section.

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